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CHEMICAL 
DISINFECTION AND STERILIZATION 



CHEMICAL 

DISINFECTION AND 

STERILIZATION 



BY 

SAMUEL RIDEAL, D.Sc. (Lond.) 

FELLOW OF UNIVERSITY COLLEGE, LONDON; FELLOW OF THE INSTITUTE OF CHEMISTRY; 
PUBLIC ANALYST FOR THE METROPOLITAN BOROUGH OF CHELSEA 

AND 

ERIC K. RIDEAL, D.Sc. (Lond.), M.A. (Cantab.) 

FELLOW OF TRINITY HALL, CAMBRIDGE; FELLOW OF 1 HE INSTITUTE OF CHEMISTRY; 
OWEN JONES LECTURER IN PHYSICAL CHEMISTRY IN THE UNIVERSITY OF CAMBRIDGE 



LONDON 

EDWARD ARNOLD & CO. 

1921 

Ail rights reserved 



v\ 



BIOLOGY 
UBRARY 






PREFACE 

Modern science becomes daily more specialized — a factor unavoid- 
able, owing to the enormous growth which this child of the mind 
has made during the last fifty years, yet one to which serious objec- 
tions may be found. 

The control of growth of micro-organisms is a problem which 
enters into many diverse and separate compartments of present- 
day science. The methods discussed and elaborated in one field 
are rarely introduced into another, although in a few cases the 
effect of environment on some original stock method may be 
readily discernible. For example, the whole problem of osmosis, 
orierinally a problem of interest to biochemists and botanists, is 
now the subject of much polemic discussion amongst physical 
chemists. The determination of Ph or the hydrogen-ion activity in 
solutions, originally a method devised and elaborated by electro- 
chemists, is one of the chief corner-stones of modern physiological 
research. 

The scientific principles underlying disinfection are simple and 
well known, but their appHcation into the many diverse spheres in 
our private and corporate life has effected what appears at first 
sight to be an extraordinary transmutation of method. Closer in- 
vestigation, however, reveals the fact that such changes are not only 
to be depicted, but are also necessary. 

In the pages of this book an effort has been made to collect 
and summarize some of the more important applications of general 
methods which have interested the authors from time to time. 
Some apology is needed for the method of presentation. Although 
some of the problems which are briefly discussed are already dealt 
with in evteyi^o ia a wide and v^aried literature, others, equally 
important in their respective fields, are scarcely mentioned in current 
textbooks, and it was felt that the inclusion of even a brief sum- 
mary batween the covers of one volume would appeal to those whose 
interests cover this wide field, but who have neither access to, nor 
leisure to study, the very scattered literature on the subject. In 
addition, it is the hope of the authors that readers may be stimulated 



vi PREFACE 

to explore that fascinating but mysterious country wherein lie the 
secrets of the laws which govern the actions of germicides on micro- 
organisms. 

Our best thanks are due to Mr. R. Orchard for his kind 
assistance both in proof-reading and in summarizing the laboratory 

data. 

S. R. 
E. K. R. 

Jul , 1921. 



CONTENTS 

CHAPTER PAGE 

I. INTRODUCTION ------ 1 

n. THE DISINFECTION OF AIR - - - . 9 

in. STERILIZATION AND PRESERVATION OF FOOD - - 36 

IV. THE STERILIZATION OF WATER - - - - 61 

V. PUBLIC DISINFECTION - - - - - 92 

VI. PERSONAL AND INTERNAL DISINFECTION - - 106 

Vn. NON-BACTERIAL PARASITES - - . - 137 

Vin. WOOD PRESERVATION - - - - - 168 

IX. CHEMICALS EMPLOYED IN DISINFECTION — CHEMICAL CON- 
STITUTION AND GERMICIDAL ACTIVITY - - 182 
X. CHElVnCALS EMPLOYED IN DISINFECTION — INORGANIC 

SUBSTANCES ------ IQfi 

XI. CHEMICALS EMPLOYED IN DISINFECTION — ORGANIC SUB- 
STANCES: ALIPHATIC DERIVATIVES - - - 213 
Xn. CHEMICALS EMPLOYED IN DISINFECTION — ORGANIC SUB- 
STANCES I AROMATIC DERIVATIVES - - - 225 

XIII. CHEMICALS EMPLOYED IN DISINFECTION — ORGANO-METAL- 

LIC DERIVATIVES . - . - . 207 

XIV. METHODS OF ANALYSIS AND TESTING - 280 

SUBJECT INDEX ------ 303 

AUTHOR INDEX - - - - - - 311 



CHEMICAL 
DISINFECTION AND STERILIZATION 

CHAPTER I 
INTRODUCTION 

Bacteria and Public Health. — Bacteria were discovered over 
two centuries ago by the Dutch naturalist Leeuwenhoek, but the 
first demonstrations of the causal relation of micro-organisms to 
disease were those of Pasteur in relation to silkworms and of 
Davaine on the bacillus of anthrax in 1863. 

The relationship between bacteriology and Public Health in its 
^^ idest sense has now been more fully developed, and at the present 
time the ramifications of the science stretch into every compart- 
ment of our daily life. The monumental work of Robert Koch, 
chiefly devoted to the study of organisms producing disease — i.e., 
the pathogenic bacteria— has led to a closer study of the methods 
by which certain bacteria gain access to the body and there cause 
these zymotic diseases, and has mdicated the way to preventive 
measures agamst infection. The bacteria given off by a diseased 
person may find their way into the systems of healthy people by a 
great number of paths. Occasionally this is brought about by 
direct contact, all the more dangerous in the case of the disease 
" carriers " who exhibit none of the usual disease symptoms, but 
have the power of transmitting it. Air currents may carry atmo- 
spheric dust or particles of water containing the germs. Certain 
diseases are transmitted through the air by means of insects Avhich 
act as intermediary hosts, especially mosquitoes, flies, gnats, and 
fleas. These carry not only pathogenic bacteria, but many kinds 
of animal parasites, notably protozoa, which give rise to specific 
diseases. Animals, such as rats, are frecpient transmitters of 
plague. Cats and dogs have been shown to carry diphtheria. 
Water is a frequent vehicle of certain disease germs, such as typhoid, 
cholera, and dysentery, which get into water-supplies from sewage 
contamination. Unlikely but occasionally, dangerous sources of 
infection are found in the soil, contaminated food, even bank- 
notes, tram and train tickets, hides, and rag flock. 

Not only do certain micro-organisms produce diseases in the 
human system, but others may make food unsuitable for consumj) 

1 



2 DISINFECTION, AND . STEJRILIZ ATION 

tion by the production of ' by-products of a poisonous nature; this 
is especially true of " ptomaine " poisoning. Others cause diseases 
in plants and wood. Certain bacteria are of course used for technical 
purposes: in making alcohols and vinegar; again, in the tannery, 
bakeries, breweries, and dairies; other and minor applications are 
adopted for retting flax, fermenting coffee and cocoa fruits, and 
curing tobacco. Partial sterilization of soil has been knowTi to 
increase the growth of crops. For many of these industries pure 
cultures of organisms must be used to produce the desired results. 
" Wild " cultures produced by infection frequently cause the loss 
of much valuable material. 

It is evident that the chief methods of control of bacterial life 
are to be found in tracing the method of infection if it has arisen, 
V and killing the organisms AA'hen found. Ideal disinfectants should 
be able to kill germs which act injuriously on higher forms of life 
without having any marked action upon such higher forms. A 
disinfectant must likewise be efficient in destroying the spores of 
pathogenic organisms, which as a rule are more resistant than the 
germs which form them. From this definition it will be evident 
that a disinfectant must do much more than prevent decomposition 
and remove the noxious smells which often emanate from putre- 
fying matter. A disinfectant really goes to the source of the 
trouble and by killing the organisms prevents the spread of epidemic 
disease or the occurrence of the other evil effects of bacterial life 
which have already been alluded to. /An antiseptic, on the other 
hand, prevents animal or vegetable substances from undergoing I 
bacterial decomposition, and a body is said to be aseptic Avhen it is 
in a condition of sterility. A substance which has the property of 
absorbing the unpleasant odours which are emitted from matter 
undergoing decay is called a deodorant, and such substances must 
be carefully distinguished from true disinfectants. 8ome disin- 
fectants are deodorants; but a deodorant, unless of a permanent 
character, is not an antiseptic. It is true that in most cases a 
noxious smell accompanies decay, and therefore any substance 
which permanently removes the smell must necessarih^ cause the 
cessation of the decay ; but in other cases in which there is no appre- 
ciable odour a deodorant would not be required. Charcoal is an 
example of a body that will absorb any unpleasant smeU which may 
arise from organic matter, but which does not kill the germ producing 
the decay. Although commonly called a disinfectant, it should be 
more properly classed among the deodorants. 

Natural influences are at work correcting and retarding any 
extensive growth of organisms. In tropical countries, strong sun- 
light is a most ei'llcient germicide; recent investigation has shown 



INTRODUCTION 8 

tliat it is the ultra-violet portion of the spectrum ^\'llieh is the most 
effective, and special apparatus has now been designed for steriliza- 
tion by u-radiation with artificial light of short wave lengths. By 
bacterial sedimentation during storage and dilution natural purifi- 
cation takes place in lakes and artificial reservoirs, Avhile the washing 
away of organic matter and decomposmg filth by rain-storms 
removes much of the pabulum which the bacteria need for thriving 
on. Pathogenic germs are frequently destroyed b}' the putre- 
factive or other products of the life of micro-organisms which are 
not directly deleterious to the human organism. Professor 
Metchnikoff's lactic acid bacillus is an organism of this nature. 
Desiccation in dry climates and severe cold in northern latitudes 
do much to restrict bacterial outbreaks, but are not, strictly s]ieak- 
ing, natural disinfectors, but rather antiseptics. 

Very early in the history of the human race we find the use of 
aromatic substances used to mask the presence of noxious odours. 
Sulphur has been employed from the earliest times, and manv 
descriptions of its uses are given. Ulysses (Od3'ssey) says to his 
old nurse: " Old woman, bring me sulphur and fire in order that I 
may free the air of its poison and purify this palace." In the time 
of Hippocrates, sulphur was regarded as an antidote against plague. 
Ovid makes mention of the fact that sulphur was employed by the 
shepherds of his time for bleaching fleeces and for purifying their 
wool from contagious diseases. During the plague of Athens, 
x\cron, according to Plutarch, stayed the sjDread of epidemic by 
lighting fires in the middle of the public places and in the streets 
where deaths had occurred, and the lighting of fires during times of 
plague has been customary until quite recent times. 

H. Henriet asserts that he has proved the presence of traces of 
formaldehyde in the air, and considers that it plays an important 
part in the purification of the atmosphere. He finds that the 
quantit}^ of formaldehyde varies between one and five jiarts by 
weight in 100.000 of air, and is proportional to the temperature.^ 
The formation of sugars in the plant cell has been thought by 
Bayer to take place through the intermediary formation of formal- 
dehyde, and lends some support to Henriet's investigations. In 
pine forests the gradual oxidation of the turpentine and other 
terpenes yields cfuite appreciable quantities of various peroxides, all 
of which have quite marked germicidal properties. 

Ozone is found in the upper strata of the atmos])her(>. Its 
formation has been attributed to the photo-chemical action of the 
easily absorbed ultra-violet light of the solar spectrum. - 

^ Compt. rend.. 19():i, 138, No. 4; 1904. 139, Xo. 1. 
2 E. K. Ridoal, " Ozone." Coiistabk', iy2(). 



4 DT8TNFF.CTI0N AND STERILIZATION 

The uso of copper for sterilizing water is of an earlj' date. The 
Sanskrit " Susruta Samhita," about 800 B.C., gives the following 
directions for storing water: " It is good to keep water in copper 
vessels to exposes it to sunlight, and filter through charcoal "; while 
in the " Atharva Veda," probably of about the same date, it is stated 
that foul water may be cleansed by insolation and dipping hot 
copper into it. The Mosaic law, with all its minute instructions as 
to the purification of the people and their belongings, shows the 
same combination of religious ceremonial and sanitary precau- 
tions; this law undoubtedly contributed to the permanency of 
the Jewish race during its early history. 

Almost contem])orary with these hygienic rec[uirements of very 
early times grew the knowledge of preserving food from bacterial 
decomposition. Probably the oldest form of preserving was by 
desiccation, and although the preserved flesh now extant in the 
form of the Egyptian mummies is preserved by desiccation with 
the aid of preserving chemicals and the exclusion of air, the pre- 
paration of meat dried and pounded with fat, as the South American 
" charqui," North American " pemmican," and South African 
" biltong," and the use of dried fruits such as raisins, figs, herbs, 
and notably hay, are very early examples of drying used as a 
preservative. It has been stated that sealed jars of preserved figs 
were discovered during the excavations of Pompeii. They still 
j)reserved " their delicate flavour and freshness." 

The first discovery of the preservative use of salt was, no doubt, 
accidental, and due to the finding of carcasses embedded in the 
incrustations of the many saline deserts of Asia. Pliny describes 
salt as " defuncta etiam a putrescendo vincUcans, ut durent ita per 
secula,"^ and refers to " carnes sale adservatse," flesh preserved 
with salt.- Columella (de Re Rustica) has " muria condire," to 
preserve with brine. ^ But at periods when fresh food was easily 
obtained, preservation was not so much a matter of importance, 
and therefore there are few early allusions to the use of salt, vinegar, 
and allied substances except as medicines or condiments. 

The difference between various salts was confused, and the 
names given are diificidt to identify. Thus in Jeremiah ii. 22, and 
in Pliny, nitre signifies crude carbonate of soda, since called natron, 
and later in Spain barilla, and although the real nitre or saltpetre 
was collected in India before the Christian era; the beginning of 
its use for reddening salted meats is of a very early date. 

The Greeks and Romans made great use of salted fish, but 
mainly as an incentive to the consumption of wine. It was not 

' Hist. Xat., 33, !). - Ibid., 33, 10. 

•' The word condiment originally means a prcsuivaUvc, from this word condire- 



INTRODUCTION 5 

likely that salting would be employed popularly, since salt was by 
no means plentiful, as shown by the word " salary " (salarium), or 
allowance of salt, coming to mean the payment of officials (Trench). 
Wine was frequently salted, or made with sea-water, with the object 
of keeping. Olives, samphire, and other vegetables were preserved 
in brine. Pickles of various kinds, rapi^i-j, were used (Julius 
Pollux, book vi.). 

Alum was known to the Egyptians as a drug, and its astringent 
and preservative action on flesh is mentioned. The effects of 
suli^hur in fumigation are described by Homer. 

Boric acid and borax were confused b}' the ancients with other 
salts, and valued only as fluxes in the arts. Asiatic borax was first 
refined at Venice. Boric acid was named by the alchemists " sal 
sedativus," but without reference to its preservative effect. 

Aromatics, on the other hand, from being used for embalming, 
Avere eventually extended to food. These generally owed their 
properties to benzoic or cinnamic acid or to essential oils. Turpen- 
tine from Pistacia terehinthus (not from pines) was added to wine 
in Palestine, and is several times mentioned in the Bible. Among 
the Romans, myrrh, the gum-resin of Balsamodendron rmjrrha, 
which grew throughout the East, had a great reputation for pre- 
venting the souring of wine, Pliny^ says: " Lautissima apud 
priscos vina erant murrse odore condita." Essential oils, aloes, 
and other bitters were also used." 

Bitter herbs were used from the first, and owed their virtues in 
preventing change partly to their tannin, which coagulated albu- 
n^inous substances, and partly to essential oils and to alkaloids, 
which acted as antiseptics. Mugwort {Artemisia vulgaris), alecost 
[Chrysanthemum balsamita), and alehoof (Nepeta glechoma) derived 
their Saxon names from their preserving beer; worniAVOod (^4. 
absynthium) was much used for vegetable juices on the Continent. 
Camomile, quassia, gentian, and hop arc all bitters of the kind. 
Acrid substances like pepper were early employed as preservatives, 
particularly from insects. All these imparted their own strong 
flavour, and therefore their application was limited. " Cassaripe," 
the inspissated juice of the root of Manihot utilissima, is used by 
the natives of Brazil and the Antilles as a meat preservative.^ 

In northern climates the smoking of meats and fish was always 
pi-actised, and oak or beech wood smoke was preferred, as these 
yield more of the preserving ag(?nts, acetic acid and creosote. The 
formation of an " empweuma." or tarry liquor, from wood ^^•as 
early known, and to hasten the process the flesh \\as dipix'd 

1 Hist. Nat., 14, 13. - Ibid., 13, IT); Palladius, 11, 14. 

^ Zeifsch. ocst. Apoth. It/-., I'JUU, L'lT. 



6 DISINFECTION AND STERILIZATION 

in it before smoking, but in this waj^ an inferior j)roduct Avas 
obtained. 

With the groA\'th of baeteriologieal science these older methods 
of preservation and steriUzation have given way to newer ideas and 
practice, especially in the means of preservation employed for food, 
and the efficient sterilization of infection carriers, with a due apprecia- 
tion of the means by which infection is carried, and very proper 
precautionary measures both in the sick-room and outside it. 

The problem has resolved itself into a struggle for existence 
between man and inimical micro-organisms, which are knowTi to 
have great vitality, powers of endurance, and facilities for penetra- 
tion, accompanied by a stupendous fecundity. That a complete 
extermination of all microscopic life would not be desirable is 
evident from the industrial importance of some applications of 
mycology, while M. Schottelius,^ as a result of his experiments on 
hatching sterilized eggs, is of the opinion that life itself is impossible 
without micro-organisms. On the other hand, from a study of 
technical mycology, one is driven to the conclusion that the enzymes 
secreted by the organisms, and not the organisms themselves, are 
the all-important bodies, and therefore Schottelius' contention is 
not strictly valid. 

The means at our disposal for dealing Avith this problem are : 

1. Exclusion. The rough methods of quarantine and sanitary 
cordons have not proved a success, since the ways of ingress are so 
many and wide, and the intolerable oppressiveness of these regula- 
tions leads certainly to their frequent evasion. The English 
methods of inspection and temporary closure of certain routes 
have proved much more effectual. Cholera killed many people, but 
it did an immense service to England by forcing us to protect our 
water supplies. The last, or personal, line of defence lies in the 
care and jirecautions taken by the individual. Cleanliness, fresh air, 
light, and good water are the chief. 

In recent years it has always been shown that many, if not all, 
zymotic diseases may be excluded from the person by the intro- 
duction of special toxins into the individual, a process which renders 
him immune from the attacks of the organisms that produce the 
disease. These toxins are produced by the pathogenic organisms 
themselves, and, as already mentioned, are usually inimical to the 
growth of the organism, and may be regarded as their natural 
disinfectants. In view of these facts, Pasteur and his successors 
have cultivated the pathogenic organisms in broth and other media, 
and after sterilization have injected the liciuid products as prophy- 

^ Xat. M'c/.s.. l!»i;}, !}2. Sue also Guyeuut, Bull. Blul. Fr. el Bclij.. 51, I'JlT; and 
Peters, Jour. I'/ii/.n'uL, Cantab., 1920. 



INTRODUCTION 7 

lactics against various diseases. The virus can also be attenuated 
by passing it through different animals, or by special methods of 
taming, until, whilst still producing the toxins, it can be introduced 
into man without producing any dangerous symptoms, and thus 
can render him immune from fresh attacks, or place him in a 
position to develop the natural disinfectant sufficiently rapidly to 
kill off the pathogenic organisms, even after they have gained 
access to the blood. Roux, at Vienna in 1894, was one of the first 
to report a large number of cures of dij^htheria by injecting a 
quantity of serum from the veins of a horse previously inoculated 
with Loeffler's diphtheria bacillus. Under the name of antitoxin, 
this diphtheria antidote is now a commercial article, and may be 
regarded as a special disinfectant for dealing with the organisms 
of this disease ; whilst during the war success has attended the anti- 
toxin treatment of tetanus, pneumonia, and influenza, and similar 
treatment is now of common practice for plague and typhoid. 

2. Removal. Under this heading may be included the natural 
processes which obtain in a healthy individual, and artificial 
methods for improving his environment. It is now well established 
that the blood by its white corpuscles, as "phagocytes," or by its 
enzj^mes, has the power of assimilating and destroying bacteria and 
spores that find their way into it. If vigorous health be maintained, 
experience proves that a human being or animal may enjoy im- 
munity for a time, even when in an infectious area. The limit to 
this protection may be reached when the micro-organisms over- 
come the phagocytes or other defensive substances in the blood. 
Many natural processes external to the individual, such as the self- 
purification of rivers, aid the higher organisms in this combat. 
Man, by artificial methods of subsidence, mechanical precipitation 
by inert matters, filtration, and chemical precipitation, supplements 
these efforts of nature to purify the water supplies. 

3. Destruction. This is the office of real disinfectants, of which 
the physical agent heat is the most important. Next come the 
multitude of chemical disinfectants, many of ■\\'hich have been 
highly vaunted, but few of which are of actual value. A knowledge 
of the chemical constitution and relative position of these compounds 
throws considerable light on their mode of action; and recent 
])rogress in synthetical organic chemistry has been of great assist- 
ance in furnishing compounds of known purity and constitution, 
which have, at the hands of the bacteriologist, been sho^AH to 
})Ossess antise])tic and disinfectant properties of ascertained value. 
The number of th(>s(> compounds is constantly on the incr(>ase, but 
at present it is dillicult to jjredict, excei)t in some few special cases, 



8 DISINFECTION AND STERILIZATION 

ill wliat (lirectiun the constitution of a conijiound influences its 
bactericidal behaviour. Pathogenic organisms have been proved 
to differ in their susceptibihty to chemical agents, so that, for 
personal disinfection at any rate, some of the newer compounds may 
eventually be proved to be definite specifics. 



BIBLIOGRAPHY. 

Prinole: Meraoirc sur les substances sej^tiques et antiseptiques. 1750. 

Reichardt: Desinfectionsmittel. 1882. 

Wernitz: Disinfcctionslehre. 1885. 

Vallin: Desinfectants. 1888. 

ROLLO Russell: Epidemics, Plagues and Fevers. 1892. 

Trankland: Micro-organisms in Water. 1894. 

Sternberg: Infection and Immunity. 1903. 

Washbotjrn and Goodall: Infectious Diseases. 1908. 

Christian: Disinfection and Disinfectants. 1913. 

OppenheimeR: Toxines and Antitoxines. 1920. 

Recent Papers. 

E. Rousseau: Research on the Sterilization of Dressings, Instruments, Gloves, etc., 

in War Surgery. Arch. Med. Pharm., January, 1919, 71, 69. 
Barthelemy L. G. Gross: Sterilization with Formaldehyde. Bull. Acad. Med., 
Aprils, 1919,81,441. 

F. Fenger, E. R. Cram, and P. Rudnick: Heat Resistant Organisms: Study of 

Bacteria encountered in Heat Sterilization of Surgical Ligatures and Sutures- 
J. Amer. Med. Assoc, January 3, 1920, 74, 24. 



CHAPTER II 
THE DISINFECTION OF AIR 

In the early days of the development of the science of dis- 
infection it was considered necessary to disinfect air, since at that 
time the air was regarded as the natural vehicle of disease germs. 
It is now generally realized that air-borne infection is extremely rare, 
non-contact cases being, however, occasionally observed, probably 
due to particles of dust or spray inhaled during coughing acting 
as vehicles for the disease germs. Although organisms in virtue 
of their small size can remain suspended in the air for long periods 
of time, being wafted about by the slightest air current, yet they 
rapidly die unless surrounded by some protecting coating such as 
a water or mucus film, when their rate of subsidence naturally 
increases. Light and the small quantities of naturally occurring 
germicides in the air. such as ozone and hydrogen peroxide in the 
country and acids in town air. are concomitant causes for rapid 
destruction. 

The early experiments of C. Fliigge^ drew attention to the 
dangers attached to speaking loudly, sneezing, or coughing as an 
aid to the dissemination of germs. This work has been confirmed 
by numerous investigators, notably by P. Frankland.- In ordinary 
respiration, however, it has been sho^v^l by numerous observers 
that bacteria are arrested by the mouth, interior of the nose, and 
expelled by the ciliary membrane in the mucus to such an extent 
that expired air is almost free from organisms, while feA\' of those 
inhaled reach the lungs. 

In our laboratory at Westminster in 1914 we found 38 organisms 
in suspension per cubic foot, and they fell out of the air at the rate 
of 538 per square foot per hour. On another day, we found 110 
organisms falling per square foot per hour, and 20 organisms in 
each cubic foot. The maximum variation was from 840 to lin 
falling per square foot per lioiii'. The number condensing with 
moisture on a vertical cooled ])late varied from !»."> to 135 p(M' sipiare 
foot per hour. 

VVinslow and Browne ' undertook a very comprehensive bacterial 

1 Zcitisch. Hi/g., 25, 1. - Eastbourne. Health Congress. IHOl. 

■^ Moidldij Weather licvi-w, July, li)14. 42, 451'. 

y 



10 DISINFECTION AND STERILIZATION 

analysis of different sorts of airs, and came to the following con- 
clusions : 

1. The number of microbes developing at 20° C. from outdoor 
air in suburban districts is general!}^ under 50 jier cubic foot, and 
rarely over 100. The count at 37° C. for such air is about half that 
at 20° C; and rarely over 50 pei cubic foot. The number of mouth 
streptococci in such air is small, averaging 10 per 100 cubic feet. 
The air from still more remote regions would no doubt show smaller 
numbers. 

2. The air of city streets shows a slightly higher number of 
microbes, but the general relations are much the same in all the 
respects noted above. 

The air of occupied spaces shows, as might be expected, larger 
average numbers of bacteria and much greater fluctuations. The 
number of organisms growing at 20° C. may average over 100 
microbes per cubic foot, as in the factories studied, and ma}^ reach 
700 or more, as in some offices. The 37° C. count averages over 
50 both in factories and offices, and was nearly as high as the 20° C. 
count in the latter case. A few very high 37° C. counts were ob- 
tained, two between 1,000 and 2,000 in offices, and one of 5,200 
in the country, the latter clearly abnormal. Mouth streptococci 
are much more abundant in indoor air, varying from 20 to 40 per 
100 cubic feet of air, and the results bear out the conclusion that 
the number of these organisms furnishes a good measure of mouth 
pollution due to concentration of population in confined spaces. 

Preliminary methods of air purification may be conveniently 
classified under the following heads : 

1. Heat. When polluted air has simply to be got rid of, it can 
be passed through a furnace if care be taken that it all comes in con- 
tact with the heated surfaces. Experiments with refuse destructors 
have established that, although a comparatively low temperature 
is sufficient for killing micro-organisms, a temperature of at least 
680° C. is essential for destroying organic noxious vapours. Heated 
channels are open to the following objections : — (a) If the air passes 
rapidly, there is danger that the central parts of the current A\'ill 
escape without Ijcing sterilized, on account of the bad conducting 
qualities of air; {b) the air so treated is rendered unfit to breathe; 
(c) the coils, if narrow, become clogged and coated; (d) they are 
uncertain in action, depending on the working of the stove; (e) if 
made of firebrick flues or fireclay tubes, instead of iron, they are 
easily broken in stoking, stirring, or cleaning; (./') they have been 
known to cause fires by passing near woodwork. Nevertheless, a 
method of this kind is cl(>aner, cheaper, and more effectual than 
any chemical disinfection for constant use. 



THE DISINFECTION OF AIR 11 

2. Washing with water, with or without disinfectants. Numerous 
apparatus have been designed, with screens, bead-tubes, j)lates, 
fans, or bubbling-through arrangements. Screens constructed of 
vertical cords interlaced with horizontal copper wires, over which 
water trickles, are useful in dusty factories and in cases of dense 
fog; the air so purified is bright, clear, and free from odour, but 
dust is not entirely arrested. 

3. Air Filters. Cotton- wool strainers are used at the Houses 
of Parliament; they can be made efficient, but require considerable 
motive power to impel the air. Asbestos filters can be renewed by 
burning, but arc only practicable on a small scale. Sodium peroxide 
has been proposed for removing carbonic acid and renewing oxygen 
in confined spaces and in sick-rooms, but there is no disinfecting 
action. 

It has already been indicated that infection is not, strictly 
speaking, air-borne, since in those cases where aerial contamina-' 
tion was indicated it has been shown to be due to the passage of 
organisms on floating dust or drops of water. Nevertheless, the 
air in rooms is frequently used as a vehicle for diffusing vaporous 
disinfectants on to the surfaces and into crannies and chinks in 
the walls of the room. In many cases the settling of organisms on 
drops of Avater and the adherence to wet wall surfaces is augmented 
by the injection of a spray into the room, together with the gaseous 
disinfectant. 

4. Sterilization of Air by Chemical Methods. The chief volatile 
germicides used for this purjiose are formaldehyde, sulphur dioxide, 
and more rarely chlorine and ozone. 

(i.) Formic Aldehyde or Formaldehyde. 

H.CHO is onl}' known in solution, " Formalin," and in a state 
of vapour, since, if an attempt be made to condense it, it poly- 
merizes to a white crystalline solid, paraformaldehyde or trioxy- 
methylene, CgHgOg. Formaldehyde is readily soluble in water, 
giving, if perfectly jiure, a neutral solution; commercially it is 
ah\'ays slightly acid, from the presence of a little formic acid.' 
The odour is pungent, causing irritation to the eyes and nose; 
beyond this action it is not poisonous. The aqueous solution is 
stable when kept in well-closed bottles, but loses some of the gas 
on exposure. Loew and Fischer, in 1886,- discovered that it 
possessed powerful antiseptic properties; Trillat, in 1888, showed 

^ Cr. Bruni states that the acid sohitions are much more fatal to micro-organisms 
tliiiii tlic neutral ones {('hcjii. Zcnir.. 51 I'JOO). 
- J. pr. Chan., 33. 221. 



12 DISINFECTION AND STERILIZATION 

that the presence of a minute quantity of this substance hi urine 
effectually preserved it from putrefying. In a further paper he 
remarks that " hitherto it has been thought that the most powerful 
antiseptic bodies belonged to the hydroxjd compounds of the 
aromatic series of hydrocarbons (the phenols) and to the metallic 
salts. Formaldehyde is, however, a very powerful antiseptic, being 
actually superior to bichloride of mercury in this respect. The 
result is quite unexpected, as acetic aldehyde does not possess thi.« 
property."' It is prepared by passing methyl alcohol vapoui 
mixed Avith air over a red-hot platinum spiral or heated platinized 
asbestos, condensing and purifying the vapours." 

Buchner,-' Aronson,^ and F. Cohn,^ have investigated the pro- 
perties of formaldehyde, while Lehmann, Gegner, and Blum*' have 
examined its value as a general disinfectant, and Stahl,^ Hauser,*^ 
and Liebreich^ have reported on its suitability for special purposes. 
All these writers are agreed in attributing to formaldehj'de powerful 
antiseptic and deodorant properties. Blum, however, points out 
that micro-organisms are only killed in somewhat strong solutions 
(2 per cent.). In 1894 C. Slater and the author confirmed Blum's 
statement.^" 

Cam bier and Brochet showed that the vapour of formaldehyde 
produced by heating paraformaldehyde effects the complete 
sterilization of household dust.'' Slater and RideaP^ examined the 
action of the vapour evolved at 10° C. from a 40 per cent, solution 
by exposing to it glass slips of dry bouillon cultures under a bell jar. 
B. typhosus, B. coli, M. prodigiosus, and Sp. cholerce were killed in 
less than ten minutes; S. pyogenes aureus in twenty; B. pyocyaneus 
in thirty minutes. As to the disinfection of rooms, Ih ounces of 
40 per cent, formaldehyde were evaporated by a spirit lamp in a 
room of 1,548 cubic feet (about 11| feet side). The dust was 
disturbed by vigorous sweeping, then examined bacteriologically. 
After four hours' exposure to the vapour, the dust was again dis- 
turbed, and a sample examined. In other experiments threads 
soaked in various cultures were suspended at different heights and 
at about 3 to 5 feet from the source of the vapour. The results 
were not decisive, but showed marked effects from the vapour 
There is no reason why much larg(>r quantities of the antiseptic 
should not be used. The air before disinfection contained 429 

' M oti it riir Sclent., 1802. 4it(). 

" Trillat ;uul Jii^rlioz, Vowpt. rend., 114, I'iTS; 115, 290; 119, .ir.l. 

•' Mitnch. Med. Woch., 1HS<), No. 20. •* lUrlin. Klin. Woch., 1S92, 74!l. 

■'■' liotan. Venir., 1894, 'u:\. « Mitnch. Med. Woch., 1893, .'{2. 

7 Pharm. Zeit., 1893, 22. 8 Miinch. Med. Woch., 1893, 5G7, 055. 

" Themp. Monat.sch., 4, 183. '" Lancet, April 21, 1894. 

'1 Conipl. rend., 119, 007. ^- Lancet, April 21, 1894. 



THE DISINFECTION OF AIR 13 

organisms for 10 litres, afterwards only 71. The tlireads after 
disinfection in all cases produced more scanty cultures, which grew 
more slowiy. Some of those impregnated with B. typhosus and 
B. coli were sterile. 

An important observation frequently lost siglit of is that 
Formalin is an active germicide only in the presence of water 
vapour sufficient to prevent polymerization. This point has been 
investigated by A. Walker.^ 

Disinfection with formaldehyde has now become widely used, 
and a large amount of experimental work has been done on this 
subject. 

In the Slater and Rideal investigation just recorded the quantity 
employed corresponds to 0-4 ounce formaldehyde per 1,250 ounces 
of air, or 0-032 per cent, b}' weight. As formaldehj^de has practicallv 
the same density as air, this is also 0-032 per cent, b}' volume. There 
have since been introduced three distinct methods of applying; 
formaldehyde to room disinfection, A\hieh possess advantages over 
the method then adopted. The}^ are: 

(1) Mechanical Methods, (a) Vaporizing paraformaldehyde by 
means of heat in the presence of water vapour; (b) spraying the 
walls, ceiling, and floor with the solution. (See Room Disinfection.) 

(2) Chemical Methods. Vaporizing paraformaldehyde by 
mixing it with sodium peroxide or potassium permanganate. 

(3) Methods attempting to increase the efflcacy of the formal- 
dehyde vapour by the addition of chemicals. 

As a precaution to be noticed in adopting any method, it is 
necessary to efficiently seal up the room before disinfection. Paper 
should be pasted over the cracks round the doors and A\indows, 
and an efficient block placed up the chimney or in front of the grate 
aperture to prevent undue waste of the vapour. It is also im- 
portant to ensure that the temperature of the room is sufficiently 
high to ensure proper sterilization; frequently the room is well 
ventilated before disinfection, and in cold weather the temperature 
may easily sink to 40° or 45° F. temperatures, at which the 
germicidal power of the vapour is very weak. About 60° F. is a 
convenient temperature for the purpose. 

1. (a) Mechanical Vaporizers. 

Trillat observed that, when heated under a pressure of two or 
three atmospheres, nearly the whole of the formic aldehyde in a 
solution may be evolved as gas Avithout the polymerization that 
occurs when heated in the ordinary manner, and tliat the production 

1 .Ve«; York Mud. J., Oct. .her H», \\)\1. 



14 DISINFECTION AND STERILIZATION 

of the active gas is assisted hy tUv addition of neutral mineral salts 
such as calcium chloride. His a])]iaratus consisted essentially of 
an ordinary steam autoclave heated by means of gas or a Swedish 
])etrol(Mnn lamp. " Formochloral," which is formalin of 40 per 
cent, containing in solution about 10 per cent, of calcium chloride,' 
is placetl in the body of the apparatus, 1 pound being said to be suffi- 
cient for " an ordinary-sized room "■ — say 1,500 cubic feet. When 
a pressure of 35 to 40 pounds has been reached, corresponding to a 
temperature of 135° to 140° C, which takes about thirty minutes, 
the gas can be introduced into the sealed room by means of a fine 
copper tube or jet passing through the keyhole of the door, and 
controlled by the valve on the top of the autoclave, which is worked 
outside the room. According to the amoinit of the charge, from 
twenty minutefi to one hour is required to discharge the gas, the 
pressure; being maintained throughout the operation. 

Dr. Kenwood obtained perfect sterilization of diphtheria s^abs 
with this apparatus, and observes in his Leeds paper: 

'■ (1) When the air is charged with from I to 2 i:)er cent, of 
formaldehyde, the disinfection of all surfaces is complete and rapid, 
and this holds good under the ordinary conditions of temperature 
and moisture obtaining in living-rooms. 

" (2) The vapours possess a certain and variable amount of 
penetrating power into loose fabrics, especially when these are dry. 
This penetration is largely due to the circumstance that when 
produced in a warm state the vapour is of a low specific gravity and 
mixes well ^\'ith the air. 

." (3) That the vapours do not affect the colours of textile 
materials, etc., or (with the exception of iron or steel) metallic 
surfaces. 

" (4) That the room and articles exposed can be cleared of the 
vapours readily by sufficient aeration, and the vapours are not so 
irritating but one can always enter the room and unseal at the first 
attempt (an advantage over SOg and Clg). 

" (5) That the disinfecting properties of the aldehyde are greater 
than those of SO, or Cl^- 

" (6) That there is no danger in entering the room, either from 
the aldehyde or from the CO which is formed at the same time. 
This is proved from the fact that the men employed in the works 
and exposed to considerable quantities enjoy good health, and also 
from many experiments with animals in atmospheres heavil}' 
charged with the vapours generated as in room disinfection." 

^ Rosenau states that in similar apparatus in America 20 per cent, of calcium 
chloride, " or some other neutral salt, sucli as borax or common salt," is used, 
and that not less than 10 ounces of the solution is allowed per 1. ()()() cubic feet. 



THE DT8TNFECTT0N OF ATE 15 

Formaldehyde Lam s. It has alread}^ been shown that good 
results cannot be obtained by the simple evaporation of a concen- 
trated solution of formaldehyde, as, owing to various causes, the 
maximum amount of the gas is not obtained. R. G. Wilson,^ from 
experiments in railway carriages, concluded that the suspension of 
sheets moistened Avith undiluted formalin (40 per cent, formal- 
dehyde) was wholly inefficient. The dry heated air caused further 
concentration and poljonerization, so that the formaldehyde lost 
its volatilit3^ A similar observation was made by Dr. Liibbert 
when working in tropical Africa. - 

Many lamps for aerial disinfection have been proposed upon tlie 
principle that formaldehyde can be generated when the combustion 
of a mixture of methyl-alcohol vapours and air takes place over 
red hot platinum (Hoffn.ann). Such lamps have been devised 
bv, among others, Tollens, Bartel, Robinson, Trillat, Broche, 
Schweinertz, and Dieudonne. 

The objections to the use of the methyl-alcohol lamps are that 
the oxidation of the methyl alcohol to formic aldehyde is far frt)m 
complete, the rate of generation and amount of the gas varying 
considerably with the same apparatus in dilTerent hands, and also 
that quantities of poisonous carbon monoxide are evolved m the 
room ec[ual to 3 to 5 per cent, of the alcohol used. It is satisfactory, 
however, to notice that Dr. Kenwood has found that under proj^er 
conditions sufficient formalclehj^de can be generated from 1.^ litres 
of alcohol to disinfect a room of 2,000 cubic feet. 

■' It is most generally recommended that with these lamps about 
2 litres of alcohol is sufficient for rooms of 8.000 cubic feet, and 
about six hours' exposure should be given." 

The difficulties attending the direct production of formaldehyde 
from methyl alcohol in situ has led other investigators to endea\-()ur 
to obviate the production of paraformaldehyde when using the 
formaldehyde solution. In America, the Chicago Board of Health 
uses a special spray producer devised by Dr. Behm, and has, there- 
fore, given up all attempts at using lamps. The Massachusetts 
State Board uses a kind of autoclave, and this apparatus has been 
used by many of the Boards of Health in the States. It resembled 
very closely Trillat's autoclave, and the formaldehyde was first 
mixed with calcium chloride solution, which is meant to facihtate 
the retention of the water when the gas is generated. It would 
seem, from our own experiments, that formaldehyde to act as a 
disinfectant requires some water vapour, and, therefore, care 
must be taken not to generate the gas too dry; Avhilst. on tlic other 

1 New York Bull. Med. Sciences, October, 19(»1. 

2 Therapist, October If), 1 !)(>!. 



16 DISINFECTION AND STERILIZATION 

hand, thorougli jionetration soonis to be retarded when too much 
water is present. 

Halzine is a 35 to GO per cent, solution of formaldehyde in 
metliyl alcohol, with 5 per cent, of menthol '"to j)revent forma- 
tion of methylal." It was used in the Oppermann-Rosenberg 
apparatus, being evaporated from an asbestos plate by a few pieces 
of red -hot coke, and is also employed as a spray. K. Walter found 
that polymerization of the aldehyde was not prevented.^ Krell's 
patent, 23,886 of 1900, rapidly pouring formaldehyde solution into 
a vessel in which a sufficient mass of heated metal had been placed 
to evaporate the liquid, is open to the same objection of waste by- 
polymerization. 

Paraformaldehyde was used, compressed into tablets, under 
the name of '" paraform," by the Formalin Hygienic Company in 
their Alformant or " Schering " lamp. This was an ordinary spirit 
lamp with a large metal (chimney supj)orting a perforated metal cup 
at about 4 inches over the flame. Some " paraform " tablets, 
weighing about 1 gramme each, are j)laced in the cup, and the 
moist products of combustion from the spirit pass up through the 
perforations, when the paraformaldehyde is volatilized chiefly as 
active formaldehyde. The directions given are to use at least ten 
tablets or 10 grammes of paraformaldehyde to every 1,000 cubic 
feet with six hours' exj^osure. 

Dr. Kenwood succeeded in sterilizing swabs infected with 
B. diphthericB by using twenty-one j^araform tablets in a room of 
2,004 cubic feet with four hours' exposure. 

One of the authors has had considerable experience with the 
paraform lamps, and details of his experiments were published in 
Public Health, November, 1897. A room of 1,500 cubic feet was 
first used to find the minimum quantity of paraformaldehyde 
which would disinfect, and it was found that : 

(a) One gramme per 1,000 cubic feet did not kill B. coli com- 
munis when the room was sealed for four hours. 

(ft) Four grammes per 1,000 killed B. coli communis and SlapJi. 
pyog. aur. exposed on silk thread, but not when the cultures were 
soaked into paper slips, the room being sealed for six hours. 

(c) With 8 grammes per 1,000 B. coli communis and Staph, 
pyog. aur. were killed on paper slips. 

{(l) Fifteen tablets per 1,500 cubic feet (10 grammes per 1,000) 
succeeded in killing B. coli communis, B. typhosus, B. diphtherice, 
Staph, pyog. aur., when the room was sealed for twenty hours and 
the organisms exj)osed on silk threads, paper slips, and inside rolls 

^ C/nni. Zenlr., ISOC, ii., 119. 



THE DISINFECTION OF AIR 17 

of linen A\hith had been dipped into the cultures. B. anlhracis 
and B. subtilis exposed in the same three Avays were not killed in 
this experiment. 

(e) Twenty tablets, equal to 13-3 grammes per 1,000, with 
B. anthracis and B. subtilis, both containing spores, failed to sterilize 
the silk threads or paper slips when they were exposed in the centre 
of the room on the same level as the lamp, but the B. anthracis 
exposed on a linen slip near the wall was found to be sterile. Room 
sealed twenty hours. 

(/) With 20 grammes per 1,000 cubic feet, silk tln-eads infected 
vAVaB. aiithracis, and exposed (1) 6 feet over the lamp and (2) near 
the wall, were sterilized. A dry paper slip similarly infected near 
the Avail gave growths on subculture, but those from a wet slip 
Avere much attenuated and did not appear until the fourth da}-. 
An infected fold of dry linen similarly placed was not sterilized, 
but the organisms in another fold, Avetted and then infected, Averc 
killed. Room sealed tAventy-four hours. 

In further experiments to determine A\'hether it Avas necessarA^ 
to remove infected fabrics from the room — ^in other Avords, to ascer- 
tain the penetrating power — it Avas found that, AA'ith 10 grammes 
per 1,000 cubic feet, pieces of damp linen infected Avith Staph, 
pyog. aureus culture, and placed in test-tubes i:)lugged A\'ith cotton- 
Avool, were not sterilized Avhen they had been enclosed within eight 
folds of a heavy blanket, and AA^hen buried in the centre of a feather 
pilloAv; on the other hand, when 13-3 grammes per 1,000 cubic feet 
Avere tried, infected linen sealed in a sterile paper envelope exposed 
on a table in the room was sterile, and the infected linen from 
similar envelopes placed inside the pillow and between eight folds 
of the blanket did not give any groAvth of the staphj'lococcus after 
subculture, although in the last tAvo cases the broth of the sub- 
culture became turbid from some other adventitious organism. 
Room sealed twenty-four hours. 

In the above experiments there Avere obtained sufficient good 
results with 10 grammes per 1,000 cubic feet to Avarrant this quan- 
tity being used in all cases of ordinary dismfection, and if in special 
eases the walls and floors are in addition sprayed with a 0-5 per 
cent, formalin solution before using the lamp, Ave belie a^c that 
disinfection Avill be ensured. 

In a report to the London County Council dated February 10, 
1902, on their experiments Avith paraform lamps, using 20 grammes 
of the tablets per 1,000 cubic feet for five hours, Drs. Klein, Houston, 
and Gordon state that " in cases Avhere Avood flooring, unpainted 
or unvarnished articles of furniture, or similar absorbing materials 
and cloth fabrics are to be submitted to disinfection on account of 

2 



18 DISINFECTION AND STERILIZATION 

their being possibly polluted Avith tubercular sputum, or highly 
resistmg microbes like the spores of anthrax or other spores (e.g., 
tetanus), the disinfection with formalin alone (in the method 
mentioned) Avill not suffice." It will be noticed that the time is 
not even that given in the directions for the use of the lamp in 
ordinary cases. 

To disinfect goods like books and boots which were liable to be 
injured by steam, Dr. Charles Porter, at Stockport, placed them 
with an alformant lamp containing five tablets in the chest of a 
" Nottingham " steam dismfector of 200 cubic feet cax^acity. Dr. 
Symons, of Bath, used, either in sj)ray or liquid form, 3 to 6 ounces 
formalin, followed by 2 ounces water, in a steam disinfector of 
70 cubic feet, from which about two-thirds of the air had been 
exhausted, closing for at least one hour, then exhausting partially 
again and passing in 1 ounce of liq. ammonite a short time before 
opening. ^ 

Most of these lamps relied upon the Mater obtained in the 
combustion of the spirit used for heating the solid paraform for 
supplying the necessary amount of moisture, but methylated spirit 
gives somewhat too small a quantity for the best results. This 
defect has been remedied in what is called the Hydroformant lamp, 
in which an annular vessel holding 12 ounces of water is fixed^ 
and this water is converted into steam at the same time as the 
tablets are gasified. A somewhat more cumbersome apparatus, 
knowTi as Fliigge's, embodies the same idea, and is used largely in 
Germany. In connection with this apparatus, a second generator 
is employed, which is used for passmg ammonia into the room 
seven or eight hours after the development of the formaldehyde, 
the ammonia combining with the latter to form hexamethylene 
tetramine, which is free from odour, before the room is opened. 

Harrington states that the gas penetrates through dry pervious 
fabrics, but not always sufficiently to ensure germicidal action, 
and that when the fabrics are damp there is practically no penetra- 
tion. He concludes that formalde'hyde should only be resorted to 
for surface disinfection. Inasmuch as the vapour is so soluble in 
water, one would expect that materials previously moistened would 
absorb more of the gas than dry fabrics, and therefore show greater 
efficiency. 

K. Walter made a series of observations in the Research Depart- 
ment of the 10th German Army Corps on the strength of formal- 
dehyde solutions fatal to common forms of pathogenic bacteria. 
" With autlirax, cholera, typhoid, staph^-lococcus, and diphtheria 
1 in 10,000 arrested growth, and slightly stronger solutions sufficed 
^ J. Sun. liiist.., January, I'JUU, 075. 



THE DISINFECTION OF AIR 19 

to destroy. Fa3ces were deodorized and rendered aseptic by a 
10 per cent, solution in ten minutes."^ With regard to the vapour, 
although he concludes that it acts efficiently as a dismfectant on 
germs near the surface, he failed to secure steriUzation of those 
more deeply situated.^ Remarkmg that " steam in motion is more 
efficacious in penetrating objects than steam not in motion," in 
later exj)eriments he passed formaldehyde vapour, together with 
steam, under pressure through a cylinder 130 centimetres long and 
0-5 metre high containing the articles to be disinfected; by this 
method it was found that the formaldehyde penetrated to the 
interior. The mixed vapours were afterwards condensed, giving 
a solution adapted for washmg floors and walls. He is still of 
opinion that the disinfection of a room and its entire contents in 
one action cannot be carried out by the vapour, " no matter by 
what method it is evolved, but that dresses, uniforms, and th'^ 
like may be disinfected entirely and without injurj^ by means of 
a current of formaldehyde vapour."-' 

In our own experiments we had already remarked the superior 
energy of a current and of moisture, bearmg in mind that the con- 
vection current passes up from the lamp and down the walls; in 
fact one of the advantages we have indicated for formaldehyde 
is its ready diffusibility and solubility m water, so that if the room 
is properly sealed it is only a question of time and quantity v.dien 
the formaldehyde shall have completely dift'used through the air 
and impregnated all the moisture in the chamber. These experi- 
mental details are conditions of every species of disinfection; they 
are easily attained, but not often observed. At the same time, if 
the fabrics are considerable m number and volume, since the 
surfaces absorb a correspondingly greater amount of vapour, it 
will be necessary to employ a larger quantity of the reagent, or it 
may be even desirable to specially disinfect them in an apparatus 
such as Walter recommends.* 

A formaldehyde diffuser, known as the Kalzen, consists of a thick 
tube which is made inflammable, and burns with a smouldering 
flame sufficient to vaporize a paraformaldehyde charge placed hi 
the contamer. Provision is made for evolution of steam at the 
same time.-^' 

1 Zcilsch. llyg., 21,421. 

2 Chem. Zenir., 1890, ii., ll'J. 

^ Zcitsch. Uyg., 26, 454-475; Chem. Zenir., 1898, i., 30G; J. Soc. Chem. Iiid., 
April 30, 1898. 

* Miinch. Med. Woch., 1899, 46, 1533. 

5 J. Soc. Chem. Ind., June, 19U7, 020; Public Health, August, 19U5, 704; 
iSaiiilanj liccord, March, 1911, 257. 



20 DISINFECTION AND STERILIZATION 

2. Chemical Methods. 

{(() Formahn Permanganate Method. A nu'tluxl simpler in 
operation than the process of vaj)orization in lamps or spraying 
is the chemical method originally suggested by Evans and Russell. 
The method consists in mixing crystalline potassium permanganate 
with a certain quantity of formalin. A part of the aldehyde is 
oxidized to formic acid, usually about one-fifth; there is a consider- 
able heat evolution which vaporizes the formaldehyde and water. 
The success of the operation depends chiefly upon the relative 
amounts of formaldeh3de permanganate and water in order to 
ensure the proper vaporization of the formaldehyde. Kenwood 
describes the method b}' which he has obtained good results: 
142-5 grammes of potassium permanganate are placed in a metallic 
dish (which should be about 7 inches in diameter and from 3 to 
4 inches deep), and twice the weight of formalin is then poured 
upon the permanganate. Dorr and Raubitschek advise using per 
cubic yard of room space jj pint of formalin (40 per cent.), I ounce 
of potassium permanganate, and || pint of water. Lockemann and 
Croner' modify the mixture by using for the same space i ounce 
of permanganate, 1 pint of formalin, and | pint of water. We 
have found the ratio of 40 grammes of permanganate to 100 c.c. of 
formalin an effective mixture. Lockemann and Croner have also 
advocated a mixture of paraform and permanganate with bicar- 
bonate of soda ; this mixture requires simply the addition of water 
to generate the formalin vapour. Major Munson has obtained up 
to 86 per cent, formalin vaporized by this method, but in general 
practice not more than 50 to 60 per cent, is generally obtained. 

(6) Formalin Peroxide Method. This method, originally intro- 
duced by Eischengrun.- is known generally as the '' Autan " 
method. The mixture consists of about 30 per cent, paraformal- 
dehyde with 10 to 15 per cent, sodium bicarbonate, to which is 
added about 60 per cent, barium peroxide. About 50 grammes 
of the mixture are used per cubic metre of room space. On mixing 
with water, the oxidation of part of the formaldehyde proceeds 
energetically, and the rest of the formaldehyde is vaporized with 
large quantities of water. According to Auerbach and Pluddemann^ 
3 parts of formaldehyde must be oxidized to vaporize 1 part with 
the necessary quantity of water (about 6 jiarts of water to 
1 part of formaldehyde). 

(c) (i.) The addition of quicklime has been suggested for 
evolving formaldehyde from its solution, but in experiments with 

1 Desinfeklion, l'.)(t<J, 11-12. 

- See also R. P. Crandall, U.S. Nuiid Mtd. null., I!ii7, 11, .519. 



THE DISINFECTION OF AIR 21 

this dehydrating agent we liave obtained only 8 per cent, of the 
theoretical yield, so that the lieat evolved by the union of the lime 
with the water is sufficient to ]iolymerize a large quantity of the 
gas.' Fused calcium chloride and concentrated sul])}nu"ic acid also 
gave very little gas. When lime is added to the formahlehyde 
solution, calcium formate is produced, and probably, therefore, 
some methyl alcohol, according to the equation — 

2CH2O +H,0 ^CHgOH +H.COOH. 

(ii.) For local application an addition of glycerine seems to 
present advantages, on account of its remaining moist, and there- 
fore penetrating porous materials and retaining the formalin, in 
addition to its own antiseptic power. R. Walther and A. Schloss- 
mann, using Lingner's apparatus, by which a mixture of 7o per 
cent, formalin, 15 per cent, water, and 10 per cent, glycerine, called 
'" glycoformal." can be sprayed into a room until a thick fog 
results, using about 4 pounds of mixture per 1,000 cubic feet 
( = ;")44 grammes CHjO, or 1-4 per cent, in the air), and closing merely 
in the ordinary manner, reported that they succeeded in sterilizing 
a number of objects of the most refractory character and of con- 
siderable thickness, while live animals were not injured.- 

(iii.) Other addition agents Mhich have been tried and suggested 
from time to time are alcohol, acetone, and some organic acids, 
chiefly of the fatty series. The intent of these addition agents is to 
increase the penetrative power of the formalin itself. Fournier 
introduces acetone, ammonia, and water in the form of a fine spray 
into the room previous to the introduction of the formalin. 

To obtain complete sterility of the walls and floors large quan- 
tities of formalin would be required. In general practice this aim 
need not be accomplished provided that the destruction of all 
pathogenic organisms is ensured. The experiments of Werner. 
Bosc, Aronson, and others have shown that under normal c(mditions 
of disinfection with formalin vapour, provided that the recom- 
mendations as regards temperature, moisture, sealing of rooms, etc., 
are adhered to, anthrax spores and also tubercle bacilli in sputum 
may be rendered inactive even if the formalin be subsequently 
removed by ammonia or other means. ^ 

' Bolten (Pharm. Weekhlad. 1918, 55, (iO), on the other hand, dainis the limo 
jH'ocess to be more efficient than the permanganate process. 
2 ,/. pr. Clwm.. 57, 173, 512. 
^ Trans. Fifteenth Int. Cong, of Hygiene, Wasliingtun, ISU:?. T'lG. 



22 DLSTNFECTTON AND STERILIZATION 

in addition to pcrnicanganatc and barium peroxide otlier oxidiz- 
ing agents have had a limited application, such as sodium dichromate. 
suggested by S. G. Dixon ;^ sodium chlorate, employed by C. G. 
Stone,- and especially bleaching powder. This method has been 
extensively developed in America, when early experiments were 
conducted by D. W. Horn.^ Hamilton* obtained bad results with 
bleaching powder as an oxidant, and states that only chlorine was 
evolved. Pozen and Dieter, -^^ on the other hand, submitted all 
these chemical methods to an exhaustive bacteriological test, and 
came to the conclusion that under the proper conditions of opera- 
tion this method was as effective as any other and more economical 
in operation. They confirmed the poor results obtained with the 
aid of lime. They give the following quantities of reagents as 
effective in sterilizing 1,000 cubic feet of room space : 

Permanganate Method. Barium. Peroxide Method. 

Formalin . . . . 1 pint | Formalin . . 1 pint 

KMnO, . . . . 0-5 pound ', Barium peroxide \\ pounds 

Sodium Chlorate Method. \ Bichromate Method. 

Fonualin . . . . 1 pint Formalin . . 1 pint 

NaClOg .. .. Bounces | ^aAaO: •• 10 ounces 

Chlorinated Lime Method. \ H0SO4 . ! .. 1 1 fluid ounces 

Formalin . . . . 1 pint Glycerine . . 11 fluid ounces 

Chlorinated lime . . ;y pound - 

(ii.) Sulphur Dioxide. 

Sulphur dioxide or sulphurous anhydride, SO2, is a colourless 
gas of specific gravity 32 (air = 14-45), with the well-kno\\'n odour 
of burning sulphur. One litre weighs nearly 3 grammes. It is 
obtained by burning sulphur or a suljihide in air — 

S-fOo^SOg. 

One kilogramme of sulphur gives 700 litres of the gas. 

It is irrespirable, producing violent coughmg and suffocation. 
About 5 per cent, in air has produced fatal results, causing acute 
catarrh, acid eructations, anorexia, irregularity of the bowels, and 
permanently impaired digestion (Hirt, Eulenberg, etc.), but I per 
cent, can be endured for a length of time. A wet towel moistened 
with washing soda enables a larger amount to be faced. 

One litre of water at ordinary temperature dissolves 50 litres, 
or 145 grammes, producing an acid liquid containing the unstable 

^^^^3~ S02+H20=H,S03. 

1 J. Amer. Med. Assoc, 191.5, 64, 4r.O. - ./. Iiul. Emj. Chrw.. litis, 10, 123. 
3 Amer. Fuh. Health, 1918, 8, 101. * I hid.. 1917, 7, 2S:$. 

6 J. Ind. Eng. Chem., 1919, 11, 448. 



THE DISINFECTION OF AIR 23 

This liquid smells strongly of the gas, as, gradually at ordinary 
temperatures and rapidly on heating, it decomposes ngain into 
suljDhur dioxide and water. Henee it rapidly loses its strength 
unless well stoppered. (It only slowly attacks corks, so that it 
can be kept in a corked bottle.) In the anhydrous .state SO., is not 
disinfectant; on addmg water it becomes active; hence the term 
" sulphurous acid " will be iised throughout for this agenW as 
more familiar and accurate. It acts in four ways : 

1. As an acid it absorbs ammonia, compound ammonias, and 
organic bases like '" ptomaines " and the products of growth of 
pathogenic organisms. The salts so formed (sulphites) are much 
less injurious. Tt has this property in common with other acids. 

2. It decomposes sulphides and sulphuretted hydrogen, with the 
liberation of sulphur. 

3. It reduces organic matters, or combines with them to form 
compounds "which are in most cases inert. This explains its bleach- 
mg action on vegetable colours, as the compounds formed are 
nearl}' colourless. But the action is evanescent, as on exposure 
to air it is oxidized to sulphuric acid, and the colour often reappears. 

4. As a poison it kills living organisms. 

The gas can be easily condensed to a colourless liquid by pressure, 
and preserved in strong metal vessels. About 3 atmosjaheres 
(45 pounds on the square inch) is sufficient. This liquefied gas is 
attainable in any quantity at a cheap rate, and is much moie 
convenient to employ than sulphur. The vessels are opened by 
a lever attached to a screw\ The gas will flow steadily for forty 
hours, a single siphon evolving 500 litres of gas, equal to the amount 
obtained from about li pounds of sulphur. It can also be obtained 
in hermetically sealed tins which are sufficient for the disinfection 
of a small room. The gas is obtained by cutting with a knife the 
soft metal pipe attached to the tin. Each tin contains about 
20 ounces of liquefied gas, and is stated to be sufficient for the 
disinfection of a room 12 feet cube (1,728 cubic feet). 

The Governments of England, United States, Belgium, France, 
Austria, Sweden, and some others prescribe fumigation b}^ burning 
sulphur for infected rooms. Hence, as Arnould says, it is the 
'■ official disinfectant par excellence." Germany, amongst I^mopean 
nations, however, does not recommend it officially, and in Berlin 
sulphur disinfection is not much employed. The British Local 
Government Board })rescribcd that for a moderate-sized room 
IJ pounds of sulphur should be burnt over a small fire and the 
room kept sealed for six hours or more. (As 1 pound of sul])hur 
yields 11-7 cubic feet of SOg, the above quantity would give 1-75 ])er 
ci'ut. in the air if the room were 1,000 cubic feet.) The wall paper 



24 DISINFECTION AND STERILIZATION 

is then to be stri))p('(l ofT and Inirnt, and the ceiling and floors 
thoroughly washed, etc. The Society of Medical Officers of Health 
suggested also that hcdding and clothes should l)e spread out on 
lines, that the sulphui' sliould he burnt over a pail of water to sup])ly 
moisture, and that the time should be twenty-four hours. Other 
official recommendations were: Belgium, 20 to 30 grammes pei- 
cubic metre =2 to 3 per cent. SO.^ in the air; Paris, 20 grammes 
per cubic metre for forty-eight hours; American Committee on 
Disinfection, 1885, at least 4 per cent. SOg for twelve hours in 
presence of moisture, equal to 1 \ to 2 kilogrammes sulphur for 
every 28 cubic metres (about 1,000 cubic feet). For ships arriving 
in the Mississippi from infected ports, the cargo is sprayed with 
corrosive sublimate solution, but sul]:)hur fumigation is used for 
the hold. A battery of eighteen furnaces contained in a specially 
constructed tug is used for heating the sulphur, and the gas mixed 
with air is forced into the hold at the rate of 180,000 cubic feet per 
hour by means of a fan. One hundred to 1,700 pounds sulphur is 
used for each vessel, according to size. 

The sulphur flame is very liable to extinction, and various 
devices have been introduced to remedy this defect. Corfield and 
Louis Parkes burn it in an iron vessel with a little spirit. Nicholls 
and Billyen, and also Vallin, use 8 i:)arts of flower of sulphur, 2 or 
3 of nitre, and 2 or 3 of bran or liquorice jiowder. This would 
give a deflagration, would retain much of the sulphur in the residue 
as sulphate, and would result in rather too raj)id an evolution, so 
that the inevitable leakage would be greater. Another plan is to 
place it on an iron tray and throw a shovelful of red-hot coals on 
it. When this plan is adopted, there is usually a residue of un- 
burnt sulphur left. A chafing-dish of coals, properly protected, 
with an iron tray over it, and lumps of sulphur distributed, gives 
better results. Even with these devices it is almost impossible to 
keep up a combustion sufficiently long, and some of the sulphur 
is wasted by being sublimed. Mendeljeff also points out' that the 
sulphurous fumes, being given off hot, ascend to the ceiling, where 
they may hv absorbed by the plaster, while some time is required 
for the gas to reach the lower portion of the room where it is most 
required. Hence the liquefied gas, excluding, as it does, the risk 
of fire, is much to be preferred. 

T. A. Clayton has designed a large a])paratus for generating S0._, 
by combustion, and for using the gas in the hot state if required.^ 
Moore and Martin's U.S. patent, 700,537 of 1902, is another large 
generator. 

^ Principles of C/unii.sIri/, 40. 

2 Patent 4,8!)i> of l!t(»2. Pah. llniJlli Engineer, April 19, 1902. 



THE DISINFECTION OF AIR 25 

Kingzett's sulphur candles are made in the form of a night- 
light, and are placed in a water-jacket as a precaution against fire. 
They are made of sulphur Avith a " powerful oxidizing agent " and 
a wick, and are arranged to buTii two hours. Tliey are very 
convenient if a sufficient number are used, and the cost is moderate. 

Seabury's sulphur candles' also burn two hours, and ditfer 
from the above in having a large compound wick. Morse and 
Bourne's patent, Wade's, and Shaw's U.S. patent. 698,748 of 
1902, affect various details in the candles. 

There has been a great conflict of opinion on the value of sul- 
phurous acid disinfection. Vallin- pronounced it perfect; Arnould' 
says that '' sulphurous acid, even in the almost inapplicable dose 
of 10 per cent., is an uncertain means of destroying spores; even 
moisture does not ensure success." Dr. Cassedebat, after a research 
at the Marseilles School of Medicine,* remarks : '" Even in the highest 
dose it is too inconstant to be recognized in the disinfection of 
virus." Savarelli'^ condemns it. Miquel could not kill germs in 
twenty days.^ Sternberg's experiments'' were unfavourable: ''It 
requires special conditions rather than abundance." Dr. A. J. 
Martin^ says " its efficacy is contestable, without counting its public 
nuisance." 

Dujardin-Beaumetz,^ who studied the behaviour of this gas 
with Pasteur and Roux, found that 20 grammes of sulphur, as 
used in the official French fumigation, did not kill Bacillus anthracis 
though it sterilized tubes of vaccine. '° Since Wolffhiigel's experi- 
ments^^ in 1881, suli:)hurous acid has quite lost its reputation in 
Germany. Koch'- obtained indifferent results; he spread the 
spores about in a room where sulphur was burnt, or laid them on 
boards, which were then washed or sprayed with a solution of 
sulphurous acid and tested by transference to culture solutions or 
by inoculation.^'' 

Dubief and Bruhl^* state that '' sulphurous acid has the most 
destructive effect on aerial microbes, especially moist, acting 
mainly on the spores of bacteria, and when pure and acting for e 
long period, it may prove fatal to dry germs." 

M. d'Abaddee states that of the Sicilian labourers engaged in 

1 Patent No. 0,407, 1S9:1 - Traite des l)csinfertatit.<<. 

^ Hygiene, 1889, 501. * Brr. f/yg.. 1891. ^ Oiom.Snr. Hal. d'llyg.. 1890. 

^ Leu Org. vivants de I'Atmosph., 1883, 289 et .leq. 

~ Med. News of Philadelphia, MuTch 2H, 188,"). « Sue. Med. Pnhlique, 1892. 

9 Bull. Acad. Med., September 9, 1884. 
^^ See Rochard's Encyclopcedia d'llygienc, 1893, 5. 
'» Miltheil. Kai.t. Gesundh., 1, 188, i- Ibid., p. 234. 

'■' Wolffhiigel and Proskauer, Ohem. Zmtr.. 13, 334. 
'* Compt. rend., 1889. 



26 DISINFECTION AND STERILIZATION 

sulphur -works only 8 or D per cent, suffer from intcriuittent fever, 
as against 90 per cent, of those not so occupied. The sulphur 
works in the marshy plain of Catania protect the people in the 
vicinity from an evil that causes other villages to be deserted.^ 
This tends to prove that sulphurous acid is strongly antagonistic 
to malaria. 

Dr. P. Frankland- found that it killed several pathogenic 
organisms. Baumann destroyed B. tuberculosis with it, and 
formerly cases of early johthisis were treated by burning sulphur. 

Drs. Marsh and Watkins-Pitchford, from trials in an experimental 
room of 1,152 cubic feet at the Government Research Laboratory, 
Bombay, in June, 1898, reported that the contents of a cylinder 
of compressed SO., destroyed the plague bacillus in twenty hours, 
even when protected by one to three thicknesses of cotton or linen, 
or by thin coverings of earth, wool, leaves, or paper. 

Klein has furnished a key to these discrepancies by showing that 
although " most pathogenic microbes do not thrive in an acid 
medium, some putrefactive and zymogenic organisms can thrive 
well in acid — e.g., Bacillus subtilis, Micrococcus ure^x in acid urine, 
etc."^ Therefore, sulphur disinfection, though generally successful, 
may sometimes fail. Wynter Blyth is also of the same opinion. 

M. Thoinot sums up thus in his Report to the Committee of 
Public Hygiene of the Seine, 1891 : " The disinfection by sulphurous 
acid is only a practice of waiting, but it is a good practice, and 
ought not to be despised."' 

One of the authors has exjierimented on the disinfection of 
rooms, using the liquefied gas, and the results obtained may be 
briefly summarized as follows : Silk threads and paper slips infected 
with B. coli communis and Staph, p. aureus were sterilized after 
twenty-four hours' exposure in a sealed room of 1,500 cubic feet, 
into which 20 ounces of SOg were passed. B. subtilis spores were 
not killed. Using 10 ounces of the gas, the silk threads infected 
with B. coli communis and Staph, p. aureus were again sterilized, 
but the paper slips were not. An important point was brought out 
by a repetition of this experiment, exposing shallow pans of water 
in the room in order to moisten the air during the disinfection; 
the SOo content of the air of the room was actually lowered after 
the twenty-four hours, through absorption by the water, from 
0-5 per cent., present in the previous experiment, to 0-2 per cent., 

1 J. Soc. Chem. Ind., 1 515. 

2 Proc. Roy. Soc, 45, 292. 

^ Micro-Organisms and Diseases, 188G, p. 258. 

* Sec also Klein, Lawes, and Lingarcl in Report of M. Off. of Local Gov. Board, 
1884, on " C'lilorinc and Sul])hui()iis Acid on Swine Fever Virus "; and CrooUshanU's 
Bacterioloyi/, 1887, p. 150. 



THE DISINFECTION OF AIR 27 

and the B. coli and Staphylococcus were not destroyed eitlier in the 
paper or silk threads. Disinfection with liquid SO2 can be used 
for all purposes for which burning sulphur is efficacious, and 
possesses the advantages over the latter of freedom from risk of 
fire and convenience in application. The quantity of aqueous 
vapour normally present in the air in England is sufficient to ensure 
the activity of the gas, and the above experiment shows that the 
exposure of large wet surfaces is to be avoided. 

An objection to the use of sulphurous acid is that non-volatile 
sulphuric acid is left behind as a result of oxidation. This acid is 
liable to corrode metal work and fabrics submitted to the disin- 
fecting j)rocess. 

(iii.) Chlorine. 

About the year 1800, Guy ton de Morveau in France, and 
Cruikshank in England, proposed the use of chlorine as a disin- 
fectant. Cruilvshank suggested 2 pints common salt, 1 pmt 
powdered manganese dioxide, with 1 pint water and \ pint sul- 
phuric acid gradually added, for hospital disinfection, giving the 
amount required for a certain number of beds. 

A similar method of generating chlorine is to gently warm 
1 part of manganese dioxide in a granular form AA'ith 4 parts of 
concentrated hydrochloric acid (5 grammes MnOo and 20 grammes 
HCl give I litre of Clg ; \ ounce of MnOj is abundance for a large 
room).^ Letheby recommended one teaspoonful of powdered 
manganese dioxide and half a cupful of strong crude hydrochloric 
acid, mixed by degrees by stirring in a saucer set on a hot brick. 

It should be remembered that the crude acid contains arsenic, 
which would be evolved as the intensely poisonous arsenious 
chloride; hence, at a little additional expense, pure acid only 
should be employed. 

Each of these methods requires heat, which presents great 
difficulties m application. Usually, therefore, the chlorine is 
evolved from chloride of lime by the action of moderately diluted 
sulphuric or hydrochloric acid. It has been stated- that I part 
bleaching powder with 2 parts sulphuric acid of specific gravity 1-53, 
and enough water to cover the powder, evolved three times as 
much chlorine as when hydrochloric is used. This may be due to 
tlie heat generated by the sulphuric acid, as the amounts yielded 
are theoretically the same, as the following equations show : 

CaCloO + H.,SO., = CaS04 + HoO + CL. 
C^aCUO + 2HC1 = CaCl. + Hob + ClJ 

' Roichardt, J)efii»fectia)is>iiilli/, ],. r,:>. - Laiint, 188S, 11(1. 



28 DISINFECTION AND STERILIZATION 

If the insoluble, and therefore solid, sulphate of lime keeps bark 
less chlorine than does the deliquescent calcium chloride, the 
difference in the yield might be explained. 

Dr. Mehlhausen' of Berlin used 600 grammes of bichromate of 
potash and 3 kilogrammes of pure hydrochloric acitl, of s])ccific 
gravity 1*10, for generating chlorine. These weights yield on 
warming 130'6 litres (405 grammes) of chlorine. He traced a 
somewhat greater activity to the gas than when prepared by the 
ordinary processes; this may, perhaps, be due to some chromyl 
chloride (CrOoClo) evolved in addition. The cost of this method 
prevents it from being generally emj^loyed. 

Chlorine has three possible modes of action : 

1. Especially when concentrated, it can combine directly with 
organic matters, or replace the hydrogen in them, precipitating all 
albuminous substances and rendering them imputrescible, while 

\j at the same time killing microbial life by combining with and 
coagulating protoplasm. Many of the substituted chloro-com- 
pounds are also inimical to bacteria; some of them, such as '' chloro- 
picrin," C(N02)Cl3, have very pungent odours. Such action would be 
slow, would scarcely occur at all except in sunlight, but yet would 
be the only possible action on dry matter. It may account for the 
antiseptic action of chlorine, as distinguished from its disinfecting 
power; the former has been questioned, but the experiments of 
Baxter and Sternberg on dried vaccine lymph seem to be conclusive. 

2. The offensive gases of putrefaction are decomposed by 

chlorine, sulphuretted hydrogen being resolved into sulphur and 

hydrochloric acid — 

H.,S+C1.,=2HC1+S. 

Phosphoretted hydrogen would be also decomposed. Ammonia 
(and compound ammonias) would give first of all ammonium 
chloride and nitrogen — 

8NH3 + 3(^2 = 6NH4CI + Na, 

hence the copious white fumes frequently noticed when a chlorine 
mixture is thrown into a dung-pit. More chlorine decomposes the 
ammonium chloride first formed; when this takes place, there is 
always a formation of intensely acrid vapours which attack the 
eyes and lungs, owing to the production of chlorides of nitrogen 
and compounds like chloropicrin. In dealing with cesspools, ash- 
bins, or privies this becomes strongly prominent in chlorine dis- 
infection. Marsh gas and some other hydrocarbons are not readily 
attacked by chlorine, but usually also are less objectionable than 
the gases mentioned above. 

' Btrirht dcr Chule.ni Conmtission, 187!>, 6, 335. 



THE DISINFECTION OF AIR 29 

3. The common and most important action of chlorine is as an 

oxidizing agent. In the presence of water, more esjx'cially in Hght, 

it combines with h} drogen to form hydrochloric acid, and liberates 

oxygen — 

2H,0 + 2Clo = 4HC1 + 0,. 

The oxygen so formed is far more active than atmospheric oxygen, 
and is in a condition to burn up the putrescent matters and kill 
the organisms which accompany the putrefaction. But there are 
several requirements for thorough disinfection in this way, and 
amongst these (a) moisture is shown by the above equation to be 
an essential, while [b) light is strongly assistant. 

(c) Quantity. Baxter was one of the first to state that the 
disinfecting action of chlorine and of potassium permanganate 
depends much more upon the nature of the liquid than upon the 
sjjecific organism present. Kuhn. Bucholtz, and Haberkorn con- 
firmed this view. They showed that in a fluid like urine, which 
consumes large quantities of chlorine, even though the liquid be 
deodorized, the action on organisms is only feeble until the chlorine 
is in excess, and that it must be maintained in excess until the last 
germ is destroyed, otherwise the fermentation will recommence. 
But if the action has been completed, germs that may afterwards 
enter from the atmosphere find it an unsuitable medium for growth. 
From this it follows that the smell of chlorine must be perceptible 
and persistent for some time, or no good result will have been 
obtained. Excess of chlorine may be chemically tested for b}' a 
paper dipped in a solution of iodide of potassium and starch paste, 
which is turned blue by free chlorine, or the bleaching of litjuus 
paper may be used as an indication. 

Baxter in his experiments mixed chlorine with vaccine lymph, 
and found that the activity of the latter was not destroyed till it 
had become acid from the presence of free HCl. Most putrefactive 
organisms thrive best in alkaline solution; hence the antiseptic 
power of all free acids in varying degrees. 

To kill pure vaccine, Baxter found the mininuuu proportion of, 
chlorine to be 0*2 per cent, {i.e., soda chlorinata solution, B.I'. 
1 in 10; chloride of lime, 1 in 100, both acidified). Hofnumn' 
gives 0-15 per cent, as sufficient for septic virus. 

{(I) Time. The vitality of the organisms considerably in- 
lluences the length of tinu^ required for sterilization. tSternberg" 
found that 1 per cent, of chlorine in air in six hours made dry 
vaccine inert. This is a vei'y large quantity, for a room of 50 cubic 

^ V icrtdjahrtmchrijt Jiir ycnchUichc Mtdicin, April, 1878. 
- Bulletin oj the U.S. Board of Health, Washington, 1881. 



30 DISINFECTION AND STERILIZATION 

metres would require at this rate 5 kilogrammes of bleaching powder, 
even if all the chlorine were evolved, which is generally impossible. 
Baxter stated' that air saturated with chlorine by standing over 
the aqueous solution took thirty mmutes to sterilize needles charged 
with dry vaccine. 

These are impossible conditions hi practice. Living organisms 
themselves contain 90 to 1)5 per cent, of water, hence the disin- 
fectant entering them Avould be greatly diluted. IMoreover, their 
envelopes are often tough and resisting, especially those of spores. 
Therefore more time must be given. 

Fischer and Proskaucr,- from laboratory experiments on sjjores 
of anthrax and various bacteria, concluded that for air fumigation 
at least 0-54 per cent, of chlorine must be present, and considered 
it more efficacious than suljjhurous acid. The experiments of Jalan 
de la Croix^ on the putrefying bacteria of beef-tea gave a sur- 
prisingly favourable account of the power of chlorine among the 
agents which are fatal to low organisms, and placed it next to 
corrosive sublimate as an " antivirulent." 

Vallin* threw some doubt on these researches, and asserted 
that the antivirulent action of chlorine is relatively restricted, and 
is notably inferior to what would be presumed by the figures given. 

Dr. Mehlhausen^ made a number of experiments, of which the 
following is an abstract : 

I. In a room of 37 cubic metres, with door and window sealed, 
he placed a number of insects in gauze enclosures, and two vessels 
of water teeming with vibrios, rotifers, and infusoria. An earthen 
pot containing 740 grammes (20 grammes per cubic metre) of 
bleaching powder with a little water, to which he added 
1,100 grammes of hydrochloric acid, was also introduced and the 
door sealed. After nine hours the room was opened and ventilated. 
The animals were all livmg; the flies only were insensible, but 
recovered on the next day. The water in the vessels, originalh' 
neutral, had become acid, and gave with nitrate of silver a copious 
precipitate of chloride. All the bacteria w^ere dead. The 
740 grammes of chloride of lime had given 59-7 litres of chlorine — 
i.e., 1-613 litres per cubic metre, or 0-1613 'per cent, in the air (about 
the amount mentioned by Hofmann, as above given), whilst some 
had been undoubtedly wasted by non-evolution and by leakage. 

II. With the same conditions as before, but with double the 
amount of chlorine. The vessel contained fermenting urme. In 

' Jieporl of Med. Off. oj I'rinij (Jouncil on DininJixUtntti. ISTo. 

- Mittlicil. Kaiserl. Gesundh., 1884. ^ Arch. exp. Path., 1881. 

* Traitc dcs Dcsinje.clants, 1882, 118. 

^ Bcrlchl dcr Vhultra Coiitiniasiun, 1S7'J, 6, 335. 



THE DISINFECTION OF AIR 31 

eight hours there was much residual chlorine. Most of the higher 
organisms were killed; the urine had become acid, but the bacteria 
and spirilla were still moving. 

III. Equal parts of common salt and manganese dioxide, with 

2 parts of sulphuric acid and 1 part of ^\'ater, were warmed together, 
whilst putrid urine and dysenteric stools in wide, tlat dishes were 
exposed for twenty hours to the gas. On oj^ening, only a feeble 
odour of chlorine was noticed, as it was masked by the efitiuvia 
from the stools and urme. Some of the organisms were only 
benumbed, and recovered their activity in fresh air. The lic^uids 
were very acid, and had not entirety lost their foetid odour. 

IV. In another room of 48 cubic metres a glass balloon was 
placed containing 600 grammes of bichromate of potash and 

3 kilogrammes of hydrochloric acid of sj)ecific gravity 1-16; by 
warming, 405 grammes of chlorine were evolved, equal to 2-7 litre:? 
per cubic metre, or 0-27 per cent. Under these conditions all the 
organisms were killed, but the time required was not stated. The 
process is, however, long, difficult, and more expensive than the 
others, the cost being given as 4 centimes per cubic metre, or 
about Is. 6d. for disinfecting a room II feet square. 

Vallin maintams that fumigations with chlorine are of little 
advantage, and are decidedly inferior to those with sulphurous 
acid. The disengagement of chlorine is incomplete, unless stirred 
and heated constantly, A\'liich is almost impossible in ordinarj^ 
practice. The facility of " sulphuring " is, on the other hand, of 
the greatest value, and the ex2)ense is about four or five times less.' 

Jeannel- noticed that chlorine seemed to have only a temporary 
action on certain vibrios, as he was able by means of ammonia to 
restore them to acti^aty after they had been subjected to the 
influence of chlorine for a long period. 

The experiments of Sternberg^ concerning the action of chlorine 
on infusoria and micro-organisms show that the resistance of the 
latter is considerable. In an experimental room of 10 litres capacity 
he placed 28 grammes of chloride of lime. It was an hour and a 
half before the movements of the bacteria contained in a drop of 
putrid meat infusion ceased, although the watch-glass holding the 
liquid was directty exposed to the gas. (If he did not acidify, the 
only chlorine evolved would be that liberated by the small quantity 
of carbonic acid in the air present — namely, about 0-071 per cent., 
which is too small a proportion, if we take Hofmann's minimum 
of 0-10 percent., or Baxter's 0-2 per cent, to be admitted.' IWil t he 

1 See Sulphurous Acid, later. - Uniun Midicah, September 2S, 1871. 

^ Bulletin oj National Board of IlaiUh, Wiishington, Julj' 23, 1881. 
* tSee later, under Chloride of Lime. 



32 DISINFECTION AND STERILIZATION 

total amount would still be immense if it could be absorbed by the 
drop of fluid, as it would reach 7 grammes of chlorine in the 10 litres 
of air.) Sternberg did not consider the movements definitely 
destroj'^ed until after an hour's exposure to fresh air they had not 
reappeared. 

Dr. Cash^ subsequently studied the action of chlorine, and 
endeavoured to determine the comparative value of the halogens 
and of sulphurous acid in destroying the virus of anthrax and 
tubercle; he concluded that the halogens do not present any great 
differences Avhen employed in solutions, the strengths of which are 
proportional to their atomic weights, though chlorine was the least 
active and iodine the most. This would oblige us to use 127 parts 
of iodine for 80 of bromine and 35-4 of chlorine. He found that 
when employed in dilute solutions they did not disinfect (that 
is, below Baxter's limit of 0-2 per cent.). He prefers sulphurous 
acid if the disinfecting agent be employed as a gas, but considers 
it better to employ a solution of the gas if possible.^ 

One volume of water dissolves approximately 2 volumes of 
chlorine gas, and as 1 litre Clg Aveighs 3-169 grammes, cold saturated 
chlorine water contains 0-634 per cent, of weight of CU- 

(e) Contact. Intimate contact between the gas and the centre 
of infection must be assured. Reichardt remarked that chlorine 
failed with large masses of putrescible matter like faeces, and must 
be supplemented by the addition of metallic salts, etc. For if all 
easily decomposable matter be not destroyed, a recommencement 
of putrefaction is not prevented.^ Klein,"* however, used chlorine 
fumigations in stables for disinfection from swine plague with 
success. Care must be taken not to give a false security by illusory 
means. Probably in many cases it is better to rely on purification 
being accomplished naturally by air and moisture than run the 
risk of natural decomposition being retarded by the employment 
of inefficient quantities of antiseptics. It must be remembered 
that manure that has been treated with chlorine or chloride of 
lime loses agricultural value on account of the destruction of its 
ammonium salts. On the other hand, if chloride of lime is sprinkled 
over faical matter before removal, it destroys any offensive gases 
that may be evolved. 

It cannot be too strongly emphasized that air cannot be dis- 
infected and still remain fit to breathe. Wernitz'^ condenms all 
fumigations as "illusory specifics," since "we require a body 

' Fharm. J., 1887, 485; L.G.B. Si.rtecntit Animal Report. 

^ Sco Inter, SuljiluirouH Atid. 

^ Reichardt, Dcsitijccltonninilld, p. 57. * L.G.B. Thirtcaiih Annual licport. 

^ Desinfectionslehre, 1882. 



THE DISINFECTION OF AIR. X] 

which sliall come in intimate contact with atmospheric dust, and 
act for a long time on it." Vallin says: "Disinfection of air is 
useless, and gives a deceitful security. To make a strong odour 
of phenol, or ]iut a basin of chlorine in a corner, is, with regard to 
destruction of virus, an operation quite futile, as the virulent 
particles in air are probably protected by an envelope of dried 
albuminous matter." 

(iv.) Ozone. 

Ozone (O3), an allotrope of oxygen (O2), is generally produced 
in the form of ozonized air by means of the silent electric discharge. 
It occurs naturally in the atmosphere, the concentration increasing 
with the altitude, rarelj^, however, exceeding 0-5 milligramme per 
cubic metre in amount. Its presence in air is to be attributed chiefly 
to the photospithetic action of ultra-violet sunlight of wave length 
A = 180 jufi, and in part to its formation along with hydrogen 
peroxide in naturally occurring processes of slow oxidation — e.g., 
of turpentme and essential oils. Chemically it may be produced 
in small quantities by the decomposition of various peroxides such 
as those of calcium or barium, from persulphates, permanganates, 
and periodates, and in relatively large quantities by the slow 
oxidation of phosphorus. The utilization of essential oils in the 
so-called disinfectors for hanging up in confined spaces is probably 
based upon the supposition that the minute amounts of ozone 
when the disinfector is operating successfully would have a marked 
germicidal activity in the surrounding air. The silent electric 
discharge, however, is the onty method at hand for the convenient 
preparation of ozonized air. Ozone is one of the strongest oxidizing 
agents known, and although it generally reacts with a utilization 
of only one-third of its available oxygen as follows : 

03+M = 02+MO, 

yet under certain conditions it may act as a whole — 

O3 f3M=3MO. 

A great number of industrial types of ozonizers have been designed 
for the purification of air in lecture-halls, theatres, public lavatories, 
slaughter-houses, tanneries, and breweries, Avhilst the London 
underground system of railways probably represents the largest 
application of the system in the world. The evidence for the 
specific utility of ozone as a means of purifying air, however, is 
distinctly disencouraging. Dewar and IMcKendrick^ show that 
by the inhalation of ozonized air the frequency of pulsation of 

1 Poijij. Ann.. 1S74,.152, 329. 



34 DISINFECTION AND STERILIZATION 

the heart is lowered ver}- considerably, the blood temperature 
sinks from 3"^ to 5° C, and post-mortem examination shows that 
the blood has become venous in appearance. Thenard^ and 
Briny^ confirmed these observations of Dewar's. Schultz^ records 
several cases of chronic poisoning by ozone. Jordan and Carlson* 
confirmed the deodorant action of ozone on air, but showed that 
long before the concentrations reached those necessary for germi- 
cidal action, injury Avas caused to the respiratory tract. 

The lowest concentration of ozone in air which can exert a 
definite disinfecting action^ appears to lie in the neighbourhood of 
13-5 milligrammes per litre. With such concentration sterilization 
can usually be accomplished in air, but the presence of large quan- 
tities of moisture lowers its germicidal activity, owing in part to 
catalytic decomposition according to the reaction — 

203=30.,. 

According to Labbe and Oudin^^ the highest concentration which 
may be inhaled without deleterious effect is approximately 0-11 
to 0-12 milligramme per litre. They state that beneficial results 
obtain by the inhalation of ozonized air of this concentration, a 
marked increase in the oxyhsemoglobin content of the blood taking 
place after an interval of from ten to fifteen minutes. It is there- 
fore evident that there is no question of germicidal activity in 
ozonized air of concentrations suitable for respiration. 

As a powerful oxidant, however, it removes small traces of 
sulphuretted hj'drogen and other impurities in air, whilst the un- 
pleasant smells associated with crowded places are amenable to 
treatment with ozone. Schwanz and Munchmeyer'^ investigated 
the deodorizing action of ozone in detail. It was noted that 
hydrogen sulphide and sulphur dioxide underwent oxidation, 
whilst the mercaptans, skatol, and amidol were oxidized to some- 
what pleasant-smelling substances. 

Carbon monoxide was but slowly oxidized, whilst ammonia was 
not affected. These observations have been in part confirmed by 
Riesenfeld and Egidius^ and Frankland.^ 

In the London Tube railway system the average concentration 
of ozone is stated to be 1-2 milligrammes per cubic metre, occasion- 
ally varying to 12 milligrammes per cubic metre. 

1 Compt. rend., 1876, 82, 157. ^ j^g,^ (jent. Bit., 1882. 20, 721. 

3 Arch.f. Expers. Path., 1892, 29, 365. 
* J. Amer. Med. Assoc, 1913, 61, 1007. 

5 Schultz, Zeitsch. Hyg., 1890, 75; De Christmas, Ann. Inst. Pastew; 1893, 7, 
689. « Compt. rend., 1891, 113, 41. 

7 Zeitsch. Kranl-h., 1913, 75, 81. ^ Zeitsch. Anorg. Chem., 1914, 85, 201. 

^ Fourth Int. Congress on School Hygiene in 1918. 



THE DISINFECTION OF AIR 35 

The use of ozonized air has been adopted to some extent in 
dairies and breweries. Will and Beyersdorfer^ state that air 
containing 0-6 to 0-7 gramme per cubic metre destroys organisms 
inimical to the brewery. They further showed by experiments con- 
ducted m the factory that moist air was more efficacious than dry, 
and that the ozone underwent catalytic decomposition on the 
surfaces of contact substances such as filtering materials. 

Frequently the fermenting tuns and the cascade coolers in 
breweries are enclosed in a suitable shaft, permitting the utilization 
of ozonized air containing a sufficiently high concentration of ozone 
to act as an effective germicide. 

Sterile air is also very desirable in refrigerating systems such 
as obtain in ship-holds or railway-cars, and the combination of an 
ozonized air generator and a refrigerator is particularly advan- 
tageous owing to the fact that the silent discharge apparatus 
operates most effectively with cold, dry air. 



BIBLIOGRAPHY. 

Wynne, W. P. : Atmospheric Pollution, Nature, 1915, 96, 442-444. 

Bolton, R. P. : The Problem of City Dust, J . Amer. Soc. Heat. Vent. Engin., 101.^, 

21, 225-231. 
William, Seward W. : Aerial cand Gaseous Disinfection, incorporating a Symjjo- 

.sium of Health Officers in Response to Seven Questions relating to Different 

Phasesof the Subject. Chicago, 1915, 30. 8vo. 
Hill, E. V.: Ventilation Standards and Synthetic Air Chart, J. Amer. Soc. Heat. 

Vent. Enghi., 1917, 23, 477-498. 
Henry, B. F. : Some Observations on Dust Separator Problems: Details that have 

been put into Practice with Improvements in Service, and Suggestions for 

Guiding in Piping, Metal Worker, etc., 1917, 87, 479-481. 
Browne, W. W. : Improved Technique in Bacterial Air Analysis, Amer. J. Put). 

Health, 1917, 7, 522. 
Knowle-s, E. R.: Dust: Its Universality, Elimination, and Conservation, J. Amer. 

Soc. Heat. Vent. Engin., 1917-18, 24, 285-327. 
W1LLIAM.S, A. W.: Flies in Winter, Brit. Med. J., 1918, i., (i9. 
'i'hird Report of the Committee for the Investigation of Atmos]jlieric Pollution, 

Lancet, 1918, 1, No. 12, Suppl., 1-24. 
Electrification of Atmo.spheric Dust, Med. Times, 1918, 46, 177. 
ToLMAN, R. C: Protection afforded by Various Filters against Bacterial Susjjen- 

sions in Air, J. Inject. Bis., June, 1919, 24, C37. 

1 Zeitsch. Branw., 1912, 35, 73. 



CHAPTER III 

STERILIZATION AND PRESERVATION OF FOOD 

The cliicf causes of change in food may be briefly enumerated 
as follows : 

1. Oxidation. — This is comparatively rare and slow in the 
absence of microbes. Dilute alcohol is transformed into acetic 
acid by air when in contact with platinum black, but the process is 
quicker under the action of the vinegar fungus, Mycoderma aceti. 
As far as is known, simple oxidation never renders substances 
injurious. 

2. Reduction. — Almost the only reducing agent that could 
naturally occur in this connection would be sulphuretted hydrogen, 
which would involve putrefaction in the substance or in the neigh- 
bourhood, and would therefore presuppose the presence of bacteria. 
It has been suggested that the peculiar taste of certain canned foods 
depends on the reduction of the fluids by the metal, on the ground 
that its degree is out of proportion with the traces of metal dis- 
solved, and that it is caused with such extreme rapidity, as, for 
example, when an apple or fish is cut with a steel knife. In this 
latter case the taste is often imaginary, as blindfold experiments 
with apples and fish show that the majority of persons are unable 
to detect which was cut with clean steel and which with silver. 
Of course, if the former metal is allowed time to become acted 
upon, a ferruginous taste is imparted. Zinc gives a different flavour, 
magnesium gives none ; hence the cause would seem to be the metal, 
not reduction. There is no evidence that a slight reduction would 
be at all injurious. Sulphites and formaldehyde, if used for pre- 
serving, would cause some reduction in unstable constituents of 
the food. 

3. Metallic Contamination. — The injury to the taste and colour 
of veo-etable substances coming in contact with iron led to the use 
of copper vessels for preparmg jams and syrups, and even pickles 
were formerly made in copper vessels. The employment of this 
metal for vinegar or very acid juices is most reprehensible, as, even 
if the surface be clean, an unknown and often considerable amount 
of metal finds its way into the food. Apparatus of wood, stone- 

30 



PRESERVATION OF FOOD 37 

ware, and even silver and platinum, have displaced copper in making 
pickles. Enamelled iron should be used for making jams. The 
presence of copper in preserved peas has been defended on the 
ground that (o) it improved the colour; (b) being antiseptic, it 
increased the keeping properties; (c) it was not poisonous in small 
quantities, but acted as a beneficial tonic. The best authorities 
regard it as irritant; it is cumulative, and it should certainly be 
prohibited. Lead may be present from the solder, and Hehner 
has drawn attention to the fact that almost all canned provisions 
contain tin in solution.' Superior goods are put up with oiled 
paper linings, so as not to come in contact with the metal. The 
irritant effects of some tinned goods have been attributed to 
chloride of zinc, which had entered in the soldering; this, and also 
the dropping in of particles of solder containing lead, have been 
since prevented by a guard-plate underneath the hole, or by the 
use of resin for soldermg instead of zinc chloride. W. Reuss- 
noticed the presence of lead in j^reserves contained in tinned iron 
canisters. The latter were constructed by bending some sheet- 
metal together, thereby avoiding contamination with lead by 
means of solder, and hermetically sealed by india-rubber bands. 
He subsequently traced the lead to these bands, M'hich owed their 
colour to red lead. On examining red india-rubber bands of 
French, German, and English manufacture, he found them to 
contain as much as 60 per cent, of red lead. Many of the india- 
rubber bands used for sealing pickles, jams, meats, and preserves 
owe their red colour to sulphide of antimony, and are free from 
lead, but antimony has not been found in the food itself. In Nev/ 
York, glass vessels have been tried to overcome these difficulties, 
but, owing to the expense, breakage, and unsightly appearance of 
some forms of soups and meats, they have not met with much 
success. For braA\Ti and potted meats earthenware is used. Its 
Aveight and fragility are the only disadvantages. 

Attempts have been made to coat the inside of t\w tin with 
varnish, paraffin, etc., but have not been successful. 

If the inside of the tin be much discoloured, or if tiniicil tin its 
show a strongly marked crystalline appearance on the inttM'ior 
surface, they are unsafe to be eaten. Any discoloration of the 
contents, or any peculiar odour or taste, should also l)e distrusted. 

4. Organisms, — ^ Yeast, moulds, and bacteria can be carried in 
the dust of the air on to the surface of any exposed food, and there 
develop fermentative and putrefactive changes. ]t \\()uld be 

1 H. Beckurtz {Apoth. Zeit., 1897, 1, 584), in his analyses of tinned iK-as, lu-ans, 
celery, aspara<^us, truffles, etc., detected tin to the amount of (•••J to (l-ti jiraninie 
]K'r Uilogranune. - Cliciu. Zcil.. IS'.M. 1.">l'"_'. 1.")S.'{. 



38 DISINFECTION AND STERILIZATION 

supposed, therefore, that exclusion of air and dust would suffice to 
preserve changeable bodies, and with this object receptacles ex- 
hausted by an air-j^ump and after^-ards hermetically sealed have 
been patented. But the food must be previously collected so as to 
exclude organisms, or must be sterilized by sufficient heat. It is 
practically impossible, however, to preserve most alimentary sub- 
stances in the raw state without the addition of spices or chemicals. 
Eggs can be preserved for months by keeping them in a pan of 
lime-water, or by dipping them in a cream of slaked lime and water ; 
in each case the shell is rendered impervious by a coating of car- 
bonate of lime, and the albummous inner lining of the shell is 
coagulated and rendered aseptic, as can be proved by breaking 
and examining. Smearing with fat or varnishing gives a bad 
flavour. Paraffin wax easily peels off, and is expensive. An 
immense number of processes have been suggested, but the most 
successful are lime-water, or excluding the air by a coating of 
vaseline. See an account of extensive trials in Germany, United 
States Consular Rej)orts, September, 1901. Sodium silicate 
(water-glass) also gives fair results.^ Fruit has been kept from 
decay by a coating of melted wax, when gathered fresh and not 
quite ripe.' B. Ehrlich cites^ a number of instances in which 
diseases were conveyed by fruit gathered, marketed, or handled 
under insanitary conditions, and points out that micro-organisms 
adhere readily to the surface of fruits. Experiments were there- 
fore undertaken to determine the number and kinds of such micro- 
organisms. The smallest number Avere found on blueberries and 
plums, and the largest number on currants and cherries. It was 
found to be possible to remove the greater number of micro- 
organisms by washing. 

Five strawberries from a pound bought in the open market in 
Covent Garden in 1914 were carefully washed in 20 c.c. of water. 
On cultures being prepared from this solution, coliform organisms 
were found present m 0-2 c.c, while anaerobic milk-clotting organisms 
were found present in 1 c.c. 

Jams are usually covered with parchment paper sealed down 
by white of egg ; this membrane does not necessarily exclude air, 
but its tiny holes must be small enough to arrest bacteria and 
spores of mould. Generally a disc of tissue paper is laid on the 
jam, when hot, as an additional precaution. It will be found some- 
times that mould has grown on the top of this, but has not pene- 
trated to the preserve. 

^ Chcm. and Driigg., 52, 704; Strutt, Chan. News, I'JUl, 83. 208. 
- Also see use of formaldehydo, p. ~i2,. 
■^ Arch. Hyj., I'JUl, No. -J. 



PRESERVATION OF FOOD 39 

Coating with glue, gelatine, or melted fat has been tried for 
meat, with only partial success. Meat is preserved to a certain 
extent by membranes such as sausage-skins. Electrical methods 
have been suggested,^ but have little effect on bacteria exce^Jt 
through the heat that maj^ be produced. 

The flour moth {Epheste Kuhniella) has long been a trouble in 
army stores, as it infests the biscuits. These biscuits, while being 
baked, are at a high temperature for a long tune and con- 
sequently the eggs in the flour from which they are made cannot 
remain living, but as the biscuits cool, these moths enter the mills 
and deposit their eggs. The remedy is to clean out the mills 
periodically with carbon disulphide or steam on the walls, floors, and 
machinery, and to cover all the open windows with fine netting. 
The biscuits can be packed in air-tight metal boxes until needed. 

Poisonous Products of Decomposition. — It must not be forgotten 
that as, in the first instance, micro-organisms settle on the surface, 
unsafe food may present a normal appearance, and consequently 
be passed by inspectors and others as suitable for consumption, 
a point in favour of the judicious use in certain cases, and under 
restrictions, of approved preservatives. Very slight evidences of 
decomposition in fish are sufficient to indicate the possible presence 
of toxic products of bacteria, so that fish can never be trusted in 
the same way that high game and mutton sometimes are. Van 
Ermengen states that the toxic ptomaines sometimes found in 
preserved meats originate from a specific organism. Bacillus hotu- 
linus. The soluble ptomaine, hotuline, which it excretes, is said 
to be mtensely poisonous. The ptomaine is destroyed at 60° to 
70° C, and the bacillus at 85° C, so thorough cooking is capable 
of removing the clanger. This anaerobic organism, B. botuUnus, may 
be taken as the type of one group, the conspicuous symptom of 
which is the disturbance of nerve functions which they give rise to. 
In the otlier grouji, gastro-enteric symptoms are produced by 
coliform organisms. 

Milk has been shown to be a frequent source of danger, and 
many epidemics have been traced to its pollution, either through 
the water supply of the cows, carelessness in the dairy, or in the 
conditions obtaining between the time when it is supplied by tlu» 
farmer and when it reaches the house of the consumer. Vaughan 
has further shoA\ii that, in addition to the danger of milk contaui- 
ing pathogenic organisms, under certain conditions fyrotoxicon, a 
ptomaine produced by a little-knoA\Ti species, has caused several 
outbreaks of summer and infantile cholera. As the poison is 

1 A3 iu patents 7,851 and S,:5<il of 1!)(I2. 



40 DISINFECTION AND STERILIZATION 

destroyed by boiling, its absence may be assured by this precaution. 
Vaughan also demonstrated its presence in cheese, ice-creams, and 
stale fish. 

Preservation of Meat. — As we have previously indicated, drying 
is one of the oldest methods of preserving meat; the expression of 
the water and desiccation leaves the fibre and dried juices incapable 
of putrefaction, but the flavour and digestibility are much impaired. 

Smoking dries the surface, and also impregnates it with acetic 
acid, wood spirit, and creosote. Although the two former eventu- 
ally volatilize from the food, the surface retains a good deal of the 
creosote, and undergoes little change except that the fat in time 
may become rusty or rancid. A great part of this rankness may 
be removed by putting about half a dozen lumps of freshly burnt 
or reheated charcoal in the water in which the meat is boiled. 
The charcoal removes the odour, but does not thereby render the 
article wholesome, hence the change must not have gone too far. 
Smoking has only a surface preservative action, and does not 
reach the interior, so that the ova of trichina, tape-worm, etc., 
remain undestroyed. In countries like Germany, where smoked 
sausages are consumed raw, or nearly so, the ravages of these 
parasites are frequently severe. In England, where thorough 
cooking is the rule, such epidemics are very rare ; still, it must be 
remembered that neither drying, smoking, nor salting secures 
safety against the ova of parasites. To save time, hams, haddocks, 
etc., are often cured by dipping in pyroligneous acid, or crude 
wood vinegar, with or without brine, or even by being merely 
brushed over with this solution. Kippers and haddocks are often 
prepared under most unsanitary conditions, and as the treatment 
is often far from complete, may be a source of danger. 

Salting. — The only inorganic salt that Ave intentionally and 
habitually add to our food is sodium chloride, which seems to be 
necessary for digestion and a natural instinct, as many wild animals 
are noticed regularly to visit salt deposits, and will lick lumps of 
salt. It will be noticed that these natural deposits ah\ays contain 
nitrates, and in many cases borax. 

There seems to be no direct equivalent of our Avord "' bacon " 
in the classics. "Perna,"^ "j)etasio," and " laridum " or " lar- 
dum," seem to be the nearest. The word " bacon " is old French. 

Salting, as commercially practised, is a process of osmosis or 
diffusion; a crystalloid applied externally, either as a solid or in 
strong solution, dii'fuses into the interior, while the soluble albu- 
minous matters pass out into the brine. Soluble mineral salts and 

1 Plautu.s, " Cure," ii., 3, 54; Persius, "et i^iper et pcrnse, Marsi monumenta 
clientis." 



PRESERVATION OF FOOD 41 

sugar also act as partial desiccators by their affinity for water. 
The flesh is deprived of a great part of its putrescent constituents, 
but at the same time loses a corresponding nutritive value 
(Liebig estimated the loss at one-third to one-half), and leaves 
nearly insoluble fibrinoids, partially hardened and less digestible 
— -■■ induratas sale," as Pliny says.^ 

After either smoking, salting, or drying, the characters of fresh 
food cannot be restored. It was not till the middle of the nine- 
teenth century that it Avas discovered that small quantities of 
certain antiseptics would enable the original qualities to be retained, 
and prevent decay for a considerable period, with less influence on 
digestion than the old curing processes. 

The quantity of mineral matter introduced in salting is con- 
siderable. A mixture of 2 pounds salt, 2 ounces saltpetre, and 
1| ounces moist sugar is rubbed thoroughly into the meat, which 
is then kept in a cool place and turned daily, rubbing in fresh salt 
where required. When the brine, as it forms, is drained away 
from the meat, the process is called dry-salting ; if it be allowed 
to remain on it, it is called wet- salting or pickling. A pickling 
brine is made with 4 pounds salt, | to 1 pound sugar, and 
2 ounces saltpetre in 2 gallons of water. The liquor in time 
becomes diluted by the meat juices, and is also apt to turn foul; 
therefore at intervals it is boiled down with more of the dry 
ingredients and skimmed, which has the effect of sterilizing it and 
removing albuminous matters. For a fine red colour the saltpetre 
is increased to about 8 per cent, of the pickling salt. In America 
it is usual to add to the brine about A per cent, of bicarbonate of 
potash or " saleratus," and creosote sometimes in the proportion 
of one drop to the gallon. 

In this way a high amount of salt and an appreciable quantity 
of nitre is consumed with the food. Thus, in mild-cured bacon we 
have found the following percentages : 

Soiliiim Potassium 

Chloride. Nitrate. 

Raw 4-27 .. 0-0083 

Smoked 3-34 .. 0-0086 

Smoked and l)oiIed 2-38 . . 0-0065 

Smoked and grilled 2-24 . . 0-0086 

The antiseptic power of salt is decidedly weak, hence the need 
for large quantities. In many cases brine becomes contaminated 
with ptomaines. The meat, however, is usually Avashcd before 
cooking. 

Occasionally carbolic acid or phenol has been ackled to brine, 

1 Hial. Nut., 28. •-'(•• 



42 DISINFECTION AND STERILIZATION 

but it is an objectionable antiseptic for food on account of its 
odour, taste, and poisonous character. Carbolic paper has, how- 
ever, been much used in Europe for packing meats. It is made by 
mixing 5 parts of paraffin wax, 5 of stearin, and 2 of phenol, and 
brushing in a melted state over paper. 

Preservation by Heat. — Articles of food always contain moisture, 
so that the conditions present here are heat and steam. In frying, 
the oil or fat reaches 160° to 180° C. (the temperature at which 
bread-crumb turns brown), so that sterilization is usually effected. 
In canned meats a temperature of over 100° C. is used, hence it is 
probable that the whole of the food is heated to that degree. But 
in cooking joints Dr. Vallin^ showed that the interior frequently 
attained only 54° to 60° C, or even less, and in long cooking only 
about 70° C. Dr. Fiore injected meat with anthrax bacilli, cooked 
it in various ways, and then tested the product by inoculating 
animals with the juice. He obtained, in roasting, a temperature 
of 60° to 65° C, and found that the bacilli were not killed unless 
the cooking had been very complete, and that the spores were not 
killed by a much higher temperature than is used in most countries 
for roasting meat. He concludes that prolonged boiling is the 
most favourable method of cooking for completely destroymg 
pathogenic germs. Vallin agrees with Fiore as to the danger of 
too much reliance on cooking, and the need of great vigilance in 
the supervision of meat supplies. 

M. Appert, of Paris, in 1810, first introduced the process of 
heating provisions in vessels Avhich could be hermetically closed, 
so that the steam should drive out the air and a vacuum be pro- 
duced. This is clearl}^ seen by the fact that the ends of tms which 
are in proper condition are concave (they may even collapse), and 
that there is an inrush of air when they are opened. Unless these 
signs are observed, the tin is bad and must not be eaten. All tins 
are examined in the warehouse, and such as are " blown " — i.e., 
convex at the ends — owing to gases from decomposition, are re- 
jected. In our laboratory a " blown " sardine tin yielded 30-5 c.c. 
of gas, which had the following composition : 

Carbon dioxide . . . . . . . . . . . . 69*7 

Oxygen 3-7 

Nitrogen, with a small quantity of Ho and CH4 . . 26-6 

The contents of the tin were semi-fluid, and had a very strong fishy, 
but not putrid, smell. There was also present a very vigorously 
growing anaerobic organism, which decomposed gelatine with the 
liberation of gas at 22° C. in less than twenty-four hours, together 
^ Rev. d'Hijg., Scptemljor, 18!)7. 



PRESERVATION OF FOOD 43 

with other liquefying organisms. Collapsed or crushed tins 
(which are sometimes offered cheap) are also dangerous, as, in 
the sharp bending of the tm, holes are apt to be formed. There 
are several processes for canning foods : 

1. The Chloride of Calcium Proaess. — ^The tins after being filled 
have the lids soldered on, leaving a pin-hole for escape of steam. 
They are immersed to two-thirds of their depth in a bath of calcium 
chloride solution, which boils at a higher temperature than water, 
heated to from 132^ to 170° C. for one to three hours, and the 
hole closed by a drojj of solder. 

2. The Aberdeen Process. — The tins are placed in a bath as 
before, but they are entirely closed. During the heating they are 
raised at times by a frame, opened to let out air and vapour, so 
that the tin does not burst, closed again, and the heating continued. 
This is repeated two or three times, according to the size and sub- 
stance. The pressure Avithin is judged by the forcing out of the 
ends. Superheated steam is used by some firms instead of salt 
baths; it is rather more difficult to manage, but leaves the tms 
clean. This process, which is known by the tins having two or 
three blow-holes, presents the advantage that more of the natural 
moisture and flavour are retained. It has superseded the former 
jirocess in Scotland, Australia, South America, and New Zealand. 

3. Jones\s Vacmim Process. — The tins are packed quite full, and 
soldere 1 up except a small hole, with a little quill tube, in the top. 
The bath contains ninety-six 2-230und tins. Along the centre of 
the bath runs a tube with twelve taps, each of which carries eight 
stuffing boxes connected with the tubes. By a fan or pumps a 
vacuum is created, and the bath is heated gradually to 100° C. 
The fluid in the tins, under the diminished pressure, boils at about 
38° C, so that the steam and air are carried off at a low temperature. 
After a time the exhaust taps are turned off. The tins then contain 
no air, and are full of steam. The cooking is continued for two 
hours at 121° C, letting oft^ the steam occasionally as the pressure 
increases. 

4. Salzer's Baltimore Process. — ^Meat is subjected to dry steam 
and compressed in moulds, then \ATapped in paper or other material, 
coated with plaster of Paris, and embedded in a heated fat such 
as suet or lard, in a can or in metallic foil, with certam j^rccautions.^ 

5. In Germany, and to a certain extent in Italy and France, 
the dangerous and objectionable custom is prevalent of eating 
meat in the uncooked state, simply smoked or pickled. Raw 
hams and bacon only smoke-dried, Gotha sausages, and even 
chopped raw steak with bread-crumbs and onions, are commonly 

1 i'atoat No. 11,U88, 18'J2. 



44 DISINFECTION AND STERILIZATION 

consumed. This practice necessitates that the meat in the markets 
should be rigidly inspected, and hundreds of carcasses are seized 
and destroyed. With the idea of saving this confiscated diseased 
meat for food, W. Budenberg, of Dortmund, invented a flesh 
sterilizer, in which the disease germs are killed by steam under 
pressure. 

It consists of a large iron cylinder, one end of ^\■hich opens on 
hinges and closes hermetically against packing. Steam at a j^ressure 
of half an atmosphere (112° C.) is injected at the top, circulates 
round the movable iron shelves on which the pieces of meat are 
placed, and escapes to a condenser through a tube at the bottom, 
or can be led into a firej^lace to burn any unpleasant vapours from 
the meat. The temperature can now be raised to 127^^ C. by 
letting in steam of 2i atmospheres; after two or three hours' 
heating all germs of disease are destroyed. The fat and liquor 
are drawn off separately below. The fat can be used, the liquor 
is thrown away. At a higher temperature the meat is much disin- 
tegrated and dried, but is still digestible and fit for the food of 
animals, dog biscuits, etc. The temperature of the interior of the 
largest lumps of flesh, as registered by a maximum thermometer, 
remains steady at from 100° to 120° C. The loss of weight is 
from 40 to 50 per cent. 

In some cases, where the apparatus is only used as a meat- 
steamer to save large quantities of meat from being lost by putre- 
faction in summer, it can be worked throughout at half an atmo- 
sphere of steam pressure. At this lower temperature the meat is 
as juicy and savoury as in ordinary cooking. The interior of the 
pieces reaches an approximate temperature of 100° C, so that it 
can be sold for eating without hesitation. The inventor states 
that the sterilization at the higher temperature was found b}^ 
experiment to be perfect. 

6. G. Harfmann''s Process'^ is on the principle of fractional 
sterilization, and consists of three steps. The first consists in 
subjecting the preserves to a temperature of 100° to 120° C. for 
a short time; the second in keeping them for some days at a tem- 
perature of 20° to 30° C, when any germs which have not been 
destroyed in the primary sterilizing process develop. These are 
then killed by a final sterilization. 

The modern processes of canning food consist chiefly in sub- 
jecting the cans to steam in autoclaves heated to 212° F. and 
higher;' careful control is exercised over the temperature, and from 
every batch a certain number of tins are always removed and 
incubated at 98° F. 

1 i'atoiit No. 14,(5U1, ISiCJ. K. T. Muhan, ./. Svc. Chan. Ind., lili:{, 32. 



PRESERVATION OF FOOD 45 

The following tj'pcs of spoiled cans are differentiated : leaks, 
springers, swells, and flat sours. 

In leaky cans the food is spoiled through entrance of the micro- 
organism through a small hole in a faulty tin. Invisible holes 
resulting from faulty can manufacture or sealing are not uncommon. 
The presence of non-sporing bacteria as well as of aerobic lactic 
acid organisms indicate the entrance of aerial contamination. 

Sprmgers are swelled cans which have been forced open by the 
pressure of the internally generated gases. Generally the trouble 
is due to under treatment, but occasionally a leaky can will admit 
of aerial contamination from outside and subsequently seal up. 
Some springers contain no living organisms ; the acids present may 
attack the tin lining and generate hydrogen, or fruit seeds or stones 
may, if the seed life has not been killed, develop in embryo and 
produce carbon dioxide. 

Flat sours are cans which contain foods turned sour and bitter. 
The bacteria bringing about this result are spore-bearers, non-gas- 
generating and anaerobic, living on the carbohydrates present. 
They are rather slow in developing, and detection is not easy. 

Preservation by Cold. — Although micro-organisms are ex- 
tensively resistant to cold, various methods of refrigeration are 
largely employed for preservative purposes. In the experiments, 
which have proved that some bacteria are not killed by very low 
temperatures, the time of exposure has been, with one exception, 
comparatively brief. Thus Pictet and Young cooled B. ayithracis, 
B. suhtilis, and a few other species progressively down to - 130° C, 
the entire duration of the test being about forty hours, after which 
growth was recovered on thawing. On the other hand, with 
B. subtilis spore-formation has not been observed below 6° C, and 
in B. antkracis not below 16° C. Coleman exposed meat for only 
six hours to -63° C; when kept in a warm room under cover it 
then putrefied " in a few days." Macfadyen and Rowland sub- 
jected P. vulgaris, B. coli communis, and a number of other bacteria 
to -252° C. for six hours without killing them, and subsequently 
they submitted several pathogenic species to the temperature of 
liquid air for six months without impairing their vitality. It may 
be generally stated that protracted cooling inhibits development, 
with eventual destruction, and prevents organisms exercising their 
proteolytic power. Moulds as a class do not grow below 2-5° C".. 
and their optimum tem]X'rature is much higher. Sedgwick and 
Winslow showed, in 1902, that of typhoid bacilli in ice or cold 
water over 40 per cent, will perish in three hours, and 1)8 per cent, 
and upward in two weeks. Sparks^ records a 65 ])(>r cent, reduc- 
' Water, September, 11)08, 259. 



46 



DISINFECTION AND STERILIZATION 



tion in the B. coli count of a polluted ice maintained at - 2"^ C. for 
two days, 95 per cent, in one week, 99-3 per cent, in two weeks, 
99-99 per cent, in seven weeks, and sterility in twelve weeks. 
B. typhosus was slightly less resistant, being completely eliminated 
in nine weeks. Large quantities of meat are imported into England, 
frozen at the temperature of from 15° to 20° F. by means of 
ammonia, carbon dioxide, or sulphur dioxide refrigerating 
machinery, or chilled at a temperature of about 29° F. The air 
must not be too dry, and the amount of humidity most favourable 
varies with the substance preserved. Dr. W. Hanna^ gives the 
following percentage saturations as adequate: Cheese 85 per cent., 
eggs 80 per cent., meat (chilled and frozen) 70 to 80 per cent., 
poultry 60 per cent., dry fruit 50 per cent. 

We have analyzed a piece of meat kept by this method for a 
period of eighteen years. The following is a table showing the 
comparative analyses of fresh English beef, Queensland cow frozen 
for a few months, and the beef frozen for eighteen years. The 
prolonged storage had not imj)aired digestibility or flavour, and 
the meat showed no signs of decomposition. 





English Beef. 


Queensland 
Cow. 


Beef Frozen for 
Eighteen Years. 


Total extract 


100 


100 


100 


Mineral .salts 


15-3 


15-4 


13-6 


Total nitrogen . . 


12-7 


13-0 


11-9 


Nitrogen in extractives 


7-1 1 


6-0 


6-2 


Nitrogen in protein.s 


5-6 i 


7-0 


5-7 


Soluble proteins . . 


43-2 


48-0 


44-5 


Albumin . . 


0-59 


1-4 


Trace 


Albumoses 


41-3 


47-7 


47-4 


Extractives 


. 1 34-0 : 


33-0 


r)rv2 


N 
Acidity c.c. — acid per 100 i 






grammes extract 


1028-0 i 


9.58-0 


9.55-0 



It will be noticed that the continued freezing has raised the 
extractive figure, although the extractive nitrogen remams the 
same, an indication that there has been a slow breaking up of these 
non-nitrogenous bodies, the carbohydrates and fats, into simple and 
more soluble bodies. 

The fact that time has little effect on the flesh is showTi by the 
familiar illustration that the flesh of mammoths which have re- 
mained frozen for thousands of years in the ice of Siberian rivers 
has been eaten by several travellers, and was used by natives as 
food. As it is almost impossible to entirely exclude putrefactive 
1 Public Health, March, 1914, 198. 



PRESERVATION OF FOOD 47 

organisms, we have to avoid tlieir injurious action l)y (1) cleanli- 
ness, (2) cold, (3) drjTiess. The necessity of cleanliness is shown 
by the fact that some species of bacteria and moulds can develop 
on frozen meat, and although they do not otherwise change, it 
may cause an unpleasant odour or taste, or discolorations. Proteus 
vulgaris was found by Levy in incrustations on ice-chests. 

Luxuriant growths of the common moulds, Penicillium. glaucum 
and cayididum and rnucor, are seen on the carcasses which have 
suffered from faulty refrigeration in transit. 

Dr. Klein has shown that bro%VTi spots on chilled beef, which 
had occasioned great loss by causing rejection by the meat inspectors 
in England, left the interior of the meat perfectly normal and 
sound. He isolated the fungus causing the infection, describing and 
figuring it in his report as a Saccharo^nyces. He found it to be 
non-pathogenic, and that it does not grow at blood-heat, but grows 
at ordinary temperatures and as low as -2° C, and that at -8° 
to -9° C. there was no growth. Therefore we may notice that it 
would not develop on hard frozen meat. Also, as it does not grow 
under anaerobic conditions, it does not penetrate into the surface. 
In 1905 one of us found that the sm-face of a sample of chilled meat 
was infected with a black mould, Cladosqwrium herbarum, accom- 
panied by the similar Chkanydomucor. This was also present in the 
calico cloth bags used as wrappers. It is therefore essential to 
sterilize these calico and stockinette envelopes and to instal dis- 
infectant measures at the factories. Dryness is to be sought in 
the surroundings, as damj) encourages the growths, whilst a moist 
coating on the meat itself is esjjecially to be avoided. In order 
to attain dryness in the air and on the svu-faces, boxes containing 
dry calcium chloride are now largely used without much expense, 
as the substance is recovered by simple evaporation and redrying. 
At intervals, when the chamber is cleansed, the surfaces should be 
sterilized bj- vapour or spray of formaldehj'de or sulphurous acid, 
and then dried in a current of air. For long raihvay journej's it 
has been proposed to use liquid air for cooling the refrigerator cars ; 
" the evaporation is so controlled that the oxygen passes into spaces, 
in the car walls, while the nitrogen is delivered round the foods, 
thereby avoiding oxidation," and the current would differ from 
ordinary air in that organisms could only rarely and accid(»ntally 
be present. 

The effect of low temperatures on animal parasites is dealt with 
by Ostertag in his handbook on "Meat Inspection." Of the 
dangerous animal parasites it has been established that Cysticerci 
are destroyed by freezing. Gage showed that in measl\- jiork kept 
fourteen days at lO'^ to 15'^ C. all the Cysticerci die, while Keis- 



48 DISINFECTION AND STERILIZATION 

mann found that this rosult occurs in joints of beef and in hams 
after keeping four days at 8° to 10° C. The legal enactment in 
Denmark is that " for domestic use and for sale in special booths 
in pieces not larger than 2-500 kilogrammes, and under statement 
of its nature, it is permitted to sell meat of animals slightly infected 
with Cysticerci, after its dangerous properties have been removed 
under veterinary supervision, either (1) by thorough boiling: 
(2) by pickling twenty-one days in 25 per cent, brine; or (3) preser- 
vation for twenty-one days in suitable (officially improved) cold- 
storage rooms in which a tem]ierature of .3" to at most 7° C. prevails 
and a moisture content of 70 to at most 75 per cent." This, it 
will be noticed, would be chilled meat. The regulations in Saxony 
and Baden are similar; in the latter it is prescribed that the cold 
storage must be for three weeks under police supervision, and that 
the temperature must not exceed 5° C. 

With trichinae, on the other hand, freezing is less effective, 
although, according to Bouley and Gibier, these parasites in hams 
containing them were killed by a cold of - 15° to -20° C. Kuhn 
found that trichinous meat kept in a refrigerator for seven weeks 
was still infested with the living worms. The sale of raw trichinous 
pork is therefore totally prohibited in Germany, although in Saxony 
meat slightly affected is allowed to market under declaration after 
thorough cooking or pickling. 

A method successfully used in the United States for preserving 
fish is to freeze them on trays in chambers kept at about - 16° C. 
then to dip the trays into cold water, when each fish becomes 
encased in a thick coating of ice; they are then packed and de- 
spatched by refrigerator car. One of the chief dangers in all cases 
is exposure to higher temperatures during transit from vessel or 
ear to the cold stores, and in the subsequent distribution. In this 
respect, freezing, as distinguished from merely chilling, has greater 
safety. 

Although we have evidence that bacteria moulds and parasites 
do not affect frozen meat when j^reserved under proper sanitary 
conditions, there is some evidence that enzyme activity has not 
been wholly restricted. It is common knowledge that frozen meat 
on thawing frequently liberates a reddish liquid of amphoteric 
reaction. We have obtained 70 cubic centimetres from 2| pounds 
of frozen beef, while J. Simons^ has obtained as much as 15 per 
cent, by weight of this fluid. The same author has measured the 
rate of autolysis of fresh and thawed frozen meat, and concludes 
that autolysis is more active in the latter. 

I'he following table shows the amomit of bases which -we have 
1 Af Froid, Jamuiiy 2."), l'.>14. 



PRESERVATION OF FOOD 49 

ttbtained from alcoholic acetic acid extractives of different kinds 

of meat : 

Weight of Base in 

Grammes obtained per 

250 Grammes. 

Fresh meat . . . . . . Negligible 

Fresh meat hung five days still fairly fresh . . 0-0041 

Siberian frozen fowl . . . . . . . . 0-0029 

Siberian frozen fowl kept three days thawed 0-0038 

Frozen meat eighteen years old ., .. .. 0-0118 

It is evident that prolonged storage mcreases the amomit of 
bases present, and must be taken as a sign of enzyme activity. 

In a sample of ice-cream purchased from a street vendor we 
have found the following bacterial contents : 

Total number of organisms per c.c. . . . . . . 540,000 

Blood-heat organisms per c.c. . . . . . . 230,400 

Rapidly liquefying per c.c. . . . . . . . . 10,000 

Bacteria of the B. coli group were present in a very large number. 

Chemical Preservatives used in Foods. 

Boric or Boracic Acid, H3BO3 (or HBO2H.3O), occurs in in- 
odorous, pearly, crystalline scales. The solubility hi water and 
in alcohol of 90 per cent, is about the same, 1 in 30. It dissolves 
in 3 parts of boiling water, and in 4 of glycerine.^ It has been 
proposed m an Italian patent to import it from Tuscany m the 
form of the native solution, but the cost of transport would thereby 
be increased. 

It is a weak acid, almost tasteless m dilute solution, and has 
no corrosive action either on tissues or metals ; this and its absence 
of odour, with a certam amount of preservative power and little 
effect on animals, have led to a large number of patents for the use 
of boric acid and borates for preventing the putrefaction of animal 
and vegetable substances. It is in no sense a disinfectant, and 
its antiseptic powers are low, although for many years it has held 
second place after salt and nitre as a preservative for meat and 
vegetables. The original discoverer, Gahn, sold in Europe two 
mixtures — ^(1) boric acid with 1 part alum, called "aseptinc"; 
and (2) boric acid with 2 parts alum, called "double asej)tine." 
It seems probable that he recognized m the alum a greater activity 
than in the boric acid. Provisions in part preserved by boric acid 
are generally within one or two months covered with a black crust, 
but the presence of alum prevents this action takmg place. 

1 Brit, riiar., 1898. 

4 



50 



DISINFECTION AND STERILIZATION 



Lehmann found that fresh beef with 1 per cent, of boric acid and 
50 per cent, salt pickle kept for several months at 80° F. Endemann 
stated^ that boric acid acted as a preservative to fresh meat only, 
and that previously salted meat could not be preserved by it. 
Lehmann infers in these cases it is not the boric acid that acts as 
a preservative, but the substances produced b}^ it — i.e., the acid 
phosjjhates. He states that " other mineral acids give exactly the 
same results without boric, especially phosphoric and hydrochloric."^ 
In investigating the effect of ordinary culinary operations on 
boric-cured hams and bacon we have found that when they had 
been soaked originally for a short time in the solution, or had been 
packed in a boric powder, the latter had penetrated very little 
beyond the rind, and was completely eliminated by the usual 
" washings " to remove salt. We also obtained the following 
results with some bacons cured with salt, saltpetre, and borax: 

Percentages of Preservatives. 



Description. 



Common 
Salt. 



Salt- 
petre. 



Borax. 



Raw. 



After 
Boiling. 



After After 
Grilling. Frying. 



Raw unsmokecl . . .. 4-27 
Raw smoked . . . . 3-34 
Raw smoked "for grill- 
ing and frying " . . 2*24 
Smoked and cooked "as j 

supplied to the trade " 2'38 

Raw undescribed . . — 



•0083 
•0080 

•0080 

•0005 



•210 
•175 



•084 



•120 



— •(11)4 -031 

•070 — I — 



Showing that a large quantity of the boric acid is removed in 
cooking. 

The great reduction in frying is explained by volatilization. 
Foulerton and RideaP investigated the digestibility of meat pre- 
served Avith boric acid by means of pej)sin, the amount of dis- 
solved nitrogen in the filtrate after one hour's digestion with pepsin 
at 38° C. being as follows : 



Control 
{No Preservative). 


Boric Mi.xlure in Meat 
(75 per Cent. Boric Acid, 25 per Cent. Borax). 


100 1 


Per Cent. 

0-05 

97-22 


Per Cent. \ Per Cent. 

0-1 0-3 

90-17 73-93 



1 Chem. News, April 2, 1880. 
'^ Lancet, November, 1899. 



- Lehmann, Practical Ilijgicuv, 1893, 2, 247. 



PRESERVATION OF FOOD 51 

It is evident that there is a reduction in digestibility of the 
meat when more than 0-1 per cent, acid is present. 

Sodium sulphite in the proportion of 1 pound to 1,000 pounds 
of meat has been found to keep the meat fresh and to retain its 
bright colour. The red colour of salted meat, according to Haldane, '■ 
is due to NO-hsemoglobin. With SOo no such compound is formed, 
but a pronounced spectrum of oxyhsemoglobin is produced.^ 

Various forms of spraying, especially with formaldehyde, have 
been used from time to time. In hot climates it is stated that a 
spray of very dilute hypochlorite keeps meat and fish fresh for a 
considerable time. 

Preservation of Fruit and Vegetables. — The general method of 
preparing '"preserved fruit" m sugar solutions or in the natural 
juices after subjecting them to heat sterilization is so well knowni 
as not to require detailed description. Tinned fruit and vegetables 
are prepared m much the same manner as meats, while dried fruits 
are easily prepared. Fruit is also largely preserved by refrigera- 
tion. In long transport it is recorded that from 14 to 26 per cent 
of oranges and lemons were formerly rendered unwholesome by 
decay, but that now, b}^ careful handling, by cooling the fruit 
through its whole substance immediately before shipment, and 
then shipping under refrigeration, all the fruit, withm about 2 per 
cent., is sound on arrival. Large cargoes of bananas are brought 
in perfect condition from Jamaica in ships' holds kept at 4-5^ 
to 7° C. by air currents cooled by means of a refrigerating machine, 
brine coils, and pumps. 

It is agreed that fruits for cold storage should be put into it 
at the earliest moment after picking, as the cold and dryness 
prevent fungi '" fruit rots." The freezing-point of apples, accord- 
ing to Madison Cooper, is below -0-5^ C, and they are sometimes 
stored without injury at - 1° C, but sudden freezing or sudden 
tha\\'ing injures the stock. Professor Siebil notes that grapes Mill 
stand -3-5^ C, while lemons will be spoilt if they go below -2" C. 
The citrus family of fruits are peculiarly susceptible to temperature. 
Taylor states that, after being kept in cold storage, fruits generally 
spoil very quickly on removal, as the moulds, etc., have been only 
restrained. It has been suggested that other succulent fruits 
besides grapes might stand freezing well on account of their elastic 
cells, and strawberries have been stated to be little affected b}' the 
cold. After cold storage the fruit has to be ripened for market 
by a dry heat never exceeding 21^ ('. This is attained at Covent 

1 J. Hyg., 1901, 1, No. 1. 

- J. Harrington, Injccl. Dinumts, 1, No. 'J; Altscliulcr, Aiclt. lli/<j., 48, -, 
p. 114. 



52 



DISINFECTION AND STERILIZATION 



Garden by electric radiators \\hich mature Malagra lemons in about 
live days, and also ripen bananas, and on the other hand keep 
tubers and bulbs so dry as to prevent them from sprouting. Spray- 
ing M'ith formaldehyde has been occasionally adopted to improve 
the keeping properties and appearance of fruit. The Board of 
Agriculture^ conducted experiments at Kew on the treatment of 
fruits with formaldehyde, and found that all kinds kept for ten 
to twenty-one days longer than when untreated; they gave the 
following directions: 

Put 10 gallons of water (preferably rain-water) mto a cask or 
a zinc bath ; add 3 pmts of formalin, mix thoroughly ; then immerse 
as many apples, contained in a net or loosely woven sack, as the 
water will cover. The fruit, after remaining in the solution for 
ten minutes, the sack being partly lifted uj) two or three tiaies to 
ensure every part of its contents coming into contact with the 
liquid, should be removed from the sack and placed on a layer 
of straw, haj^, or some suitable substance to drain and dry. It 
is not necessary to immerse in water, after their removal from the 
formalin mixture, apples that are intended for storing. Plums, 
strawberries, and other soft fruits should be placed m a sieve or 
some such firm open structure for immersion in the solution. 

The strength of the formalin solution is said to be little affected 
by use, so that the process of sterilizmg batch after batch of fruit 
can be continued until the solution is practically used up. 

The use of hydrocyanic acid has also been suggested. - 

Boric acid is nearly always detectable in fruits, but is mainly 
of natural occurrence.^ Allen and Tankard* give the following 
table, showing the proportion of boric acid contained in various 
fruits and ciders : 



Material Examined. 



Boric Acid (HgBOy) found. 



1. Apple (Norfolk) . , 

2. Apple (Fox whelp) 

3. Apple (Old Foxwhelp) . 

4. Pear, No. 1 


. . 0-009 per 
.. 0-013 ., 
.. 0-011 „ 
.. 0-007 „ 


cent. 


5. Pear, No. 2 


.. 0-016 „ 




0. Quince 


.. 0-016 „ 




7. Pomegranate 


. . 0-005 „ 




8. Grapes 

9. Norfolk cider 


.. 0-004 „ „ 

. . 0-009 gramme per 100 c.c 


10. Hereford cidei 


. . 0-017 „ 


5 J J> 


11. Devonshire cider . . 


. . 0-0()4 „ 


3J J5 


12. Apple juice (Devon) 


.. 0-004 „ 


JJ 35 



1 J . Board of Agriculture, December, 190G. 

- J. Sac. ahem, hid., 1901, 8G2. ^ Lippmanii, Ckcm. ZeiL, 1902, 26, 465. 

1 AnuLij6l, 190-i, 30-1. 



PRESERVATION OF FOOD 53 

It was discovered in Russia in 1004 that the fruit drinks sold 
were largely sweetened with saccharin, and in consequence a severe 
supervision was established over the sale of this drug. Saccharin 
(benzoyl sulphonimide) has a distinct preservative power. More 
frequently than these preservatives we find sulphites, benzoic acid, 
or salicylic acid. K. Lehmann^ states that no unpleasant effects 
were observed after fourteen days' consumption of jam containing 
0-125 per cent, of benzoic and 0-125 per cent, of 1:3- niethyl- 
benzoic acid. 

Preservation of Milk, Cream, Butter, Margarines, and Cheese. 

Milk. — A number of ])athogenic organisms find milk a favour- 
able place of growth, so that infection of different kinds can be 
carried by it, and several epidemics have been traced to this cause. 
Hence the recommendations that milk should be boiled, and the 
necessity for extreme cleanliness in dairies. Infectious disease 
occurring on the farm must, under heavy penalties, be instantly 
reported, and the supply of milk discontinued until the case has 
been removed and the buildings properly disinfected. Milk-cans 
should be washed and scalded as soon as possible after use, drained 
and dried in a place free from dust, and kept covered till wanted. 
Removing any stale smell bj^ charcoal is not a safe proceeding, as 
the odour is a sign that the cleaning has not been thorough; in 
such a case the can should be thoroughly steamed, and then washed . 
Water from ponds or contaminated wells should never be used for 
washing vessels that are intended for milk, as this has originated 
many cases of zymotic disease, and the purity of the supply should 
be periodically tested. Strongly smelling disinfectants cannot be 
employed for dairies, since miUc is so particularly absorbent of 
odours. Probably hydrogen peroxide would be the best agent for 
this purpose, if it were cheaper. It is to be regretted that jets of 
steam are not more extensively used for cleaning milk vessels; it 
would be easy to fit up an apparatus for this treatment at raUway- 
stations, where the cans could be systematically cleansed before 
going to the farms. 

Thorner- has estimated the acidity requisite to coagulate milk 
on warming as corresponding to 0-207 per cent, of lactic acid, but 
we have found the coagulating point somewhat higher than this, 
as the coagulation is not very marked even when the acidity is 
0-23 per cent., and we believe that when the acidity exceeds 0-25 ])er 
cent, of lactic acid the milk would be considered sour and unfit 
for sale. 

1 Chem. Zeit., 191 G, 40, 725. 

2 Lancet, January 27, 1900. 



54 DISINFECTION AND STERILIZATION 

The motliods of milk preservation may be divided into the 
following groups : 

I. Sterilization by Heat. — Milk can be kept for an indefinite 
time by heating it under pressure to 120° C, closmg it whilst hot 
M'ith sterilized sto2:)pers. and storing it in a cool place. If exposed 
in a Avarm situation after this, the casein is apt to undergo some 
molecular change, by which it clots into granules, or even sets 
almost solid, but no putrefaction ensues. According to Wroblewski, 
sterilization of milk causes the conversion of a little of the milk 
sugar into caramel, the formation of a trace of lactic acid, the 
coagulation of albumin, and a slight alteration in the casein, but 
does not lessen the digestibility. Duclaux kept milk for five years 
in a vessel from which he had j^reviously exhausted the air and 
heated the contents to 120° C. 

2. Pasteurization is a partial sterilization at a temperature high 
enough to kill pathogenic organisms and to prevent change for a 
moderate time, without seriously affecting the physical qualities 
of the milk. The International Congress of Hygiene, 1903, declared 
that milk of which the origin and conditions of production were 
unknown should be considered as dangerous for public supply, 
and must be submitted to heat before consumption. When 
properly conducted, such heating removed any pathogenic pro- 
perties without injuring sensibly the food value. Three methods 
were distinguished : 

(a) In simple ebullition, as practised domestically, milk is raised 
to y5°-98° C. for a short time, and then kept above 80° C. for 
fifteen to seventeen minutes; this destroys B. tuhercvlosis, the 
most resistant of the ordinary pathogenic forms occurring in milk, 
provided the pellicle Mhich forms on the surface of the fluid be 
removed, as this protects the tubercular organisms. The milk 
should be allowed to cool in the vessel in which it is heated. 

[h) In domestic pasteurization by apparatus of the Soxhlet 
type, bottles containing the milk are placed in water, which is 
heated to boiling and then cooled, the operation lasting about 
forty-five minutes. The bottles are closed by spring stoppers 
with rubber rings, so as to allow the escape of vapour while heating, 
and to close the vessel hermetically on cooling. On inverting the 
bottle and giving it a smart tap, a sharp click should be observed, 
indicating that a partial vacuum has been formed. 

(c) Industrial pasteurization on the large scale at 85°-90° C. 
According to Henseval and Mullie, in Denmark cream is heated 
to 85°, but in Belgium only to 70° or 75°; pasteurization improves 
it for keeping and for making butter. As milk is a somewhat 
viscous liquid, and does not conduct heat freely, it is kept in 



PRESERVATION OF FOOD 55 

circulation througli coils or plates, and the regenerative principle 
is frequently adoiited. 

The Congress agreed that the methods (/;) and (c) assured the 
destruction of tubercle bacilli, but did not sterilize the milk, which 
must be consumed within the following twenty-four to forty-eight 
hours. The favourable influence of agitation during the process 
was also recognized. 

In any system of milk sterilization a certain variation of tem- 
perature is liable to occur, and it is therefore important to leave 
a margin above the theoretical minimum of " sterilization," especi- 
ally where the process is intended as a safeguard against disease. 

3. Preservation by Freezing. — North Germany and Denmark 
have shipped much frozen milk in blocks, " milk ice," mostly to 
England. Machinery is used to agitate the milk during freezing 
to keep the substance uniform. An American consular report 
from Chemnitz deals with the advantages of delivering frozen milk, 
since it preserves its original properties unchanged for weeks. 
Frozen specimens kept over a month in a refrigerating-room showed 
on thawing no alteration in taste, while the number of bacteria 
was much reduced. The cream remained equally diffused through 
the solid mass. The freezing-point of milk is about - 0-5° C. 
Milk which has been frozen should be well shaken up in thawing. 
Supplemented by precautions of cleanliness and sterility of vessels, 
it is a great advantage for milk to be refiigerated immediately 
after milking, as this inhibits bacteria, which develop rapidly io 
the warm milk. 

4. Preservation and hiterilization try Ultra- Violet Light. — Experi- 
ments conducted by Bates at Liverpool and others have found 
that ultra-violet light ^\•ill sterilize milk if the latter is exposed in 
a sufficiently thin film to the action of the rays. Bloxan^ makes 
use of freezing to form thin plates of milk, which are then exposed 
to the action of the rays. It has been suggested that the vitamins 
are affected by the process. Henri and Helbronner also make use 
of preliminary cooling or freezing.- 

Freund^ gives some account of experiments conducted on the 
ozonization of milk, a process which has been the subject of numerous 
patents.* Although the treated milk kept well, it acquired an 
offensive taste and turned brownish. On standing, a ilocculent 
precipitate is formed. 

Shelmerdine'^ subjects the milk to the action of an electric 

1 J. Soc. Chem. Ind., 1911, 1027. 

2 Fr. pat., 442,807 of 1911; Fr. pat., 442,924 of 1911. 

3 J. Soc. Chem. Ind., 1911, 1082. * E.g., Fr. pat., 4r)8,;-5r)9 of IDi:} of A. :\ragits. 
5 Eng. pat., 17.5.')4 of 1911. 



56 DISINFECTION AND STERILIZATION 

current, and specifies the subjection of each 20 c.c. of milk to a 
current of 15 to 65 amperes at 200 volts per 508 square inches of 
area of the electrodes. 

J. M. Beattie^ claims to have effected the destruction of tubercle 
and B. coli in milk by means of a rapidl^^ alternating current, th(^ 
odour and colour of the milk being unaffected by the treatment. 

Fischer and Gruenert^ investigated the influence of the preser- 
vative on the keeping qualities of butter. They came to the con- 
clusion, as a result of their experiments, that salt was the best 
preservative when present to the extent of 30 per cent. By its 
presence the decomposition of the fat and casein was nearly in- 
hibited for three months, but in the case of other preservatives, 
such as benzoic, salicylic, or boric acid, even when present to the 
extent of 1 per cent., this result was not effected. 

A German Commission appointed in 1911 condemned the use of 
benzoates in food for the following reasons : Slightly putrefactive 
meat could be deodorized by means of this preservative, giving an 
appearance of freshness. Good margarine will keep for several 
months without preservatives, whilst, if preservatives are employed, 
the manufacturers tend to neglect cleanliness, especially with 
margarine and protein foods. 

Condensed Milk. — The process was invented by De Leinac, in 
1852, and modified later by Borden of New York, who introduced 
vacuum pans for concentrating the milk without burning. In 1866 
the Anglo-Swiss Company started Borden's process on a large scale. 
The milk is brought in every morning by farmers, who are kept 
under very careful supervision as to cleanlmess of surroundings 
and absence of disease. It is tested, mixed, and heated in a bath, 
with the addition of pure white sugar, then run into the vacuum 
pans (closed copper vessels from which the air and steam are 
exhausted), and evajjorated rapidly at a low heat for two or three 
hours till it is of the consistence of honey. It has been kept 
practically unchanged for upwards of twenty years. Great cleanli- 
ness is, of course, necessary in the process, and the tins must be 
sterilized by a jet of steam. In New Zealand^ the tins are 
first cleansed with lime-water, then with cold water, before 
steam sterilization. If there be any imperfection in the process, 
or if the tin be not properly sealed, the milk becomes solid 
and cheesy. If too highly concentrated, the milk-sugar crj'stallizes 
and the preparation becomes gritty. 

Condensed milk is perfectly wholesome, but the balance of its 

1 Lancet, April, 1914, 969. 

- Ze.it. Unlers. Nahr. Genussm.., 1911, 22, 553. 

^ 6Vjo?»6cr o/ Cowmerce, November, 1911. 



PRESERVATION OF FOOD 57 

food value is disturbed bj' the enormous proportion of sugar, about 
50 per cent. For this reason it is unsuitable for infants. The 
directions on the tin as to dilutions are frequently misleading — 
1 in 5 or 6 for adults, and 1 in 12 for infants — as the concentration 
is only 1 to 3 or 3|. Brands such as the '"Viking." containing no 
added sugai, have been introduced. 

Butter. — -The production of sterilized butter has not been 
entirely successful, owing to the fact that the proper sterilization 
of the cream is prevented by the necessary changing of the re- 
ceptacles during the manufacture. The cream is in consequence 
brought in contact M'ith numerous surfaces, and is necessarily 
subjected for a considerable time to the action of the air. The 
demand for sweet cream butter is not great, and the flavour of the 
commercial product is due to a " ripening " of the cream caused 
by certain bacteria, which in the larger dairies are now scientifically 
selected and controlled. The lactic bacteria, by producing acid, 
check the development of other organisms which may produce 
injurious fermentative changes. In Europe, the conclusion has 
been very general that butter produced from pasteurized cream, 
with the use of special bacterial cultures as starters of the ripening, 
is superior to that made from unjsasteurized cream. ^ We have 
seen that this opinion was endorsed at the Brussels Congress of 
Hj^giene, 1903. In America, however, according to Conn," the 
tests do not seem to have been so favourable to the pasteurized 
cream, as it does not produce so high a flavour.^ 

E. E. Ritsert* jDoints out that, notwithstanding the occurrence 
of most diverse micro-organisms in rancid fats, both aerobic and 
anaerobic germs die when added to the fresh undecomposed fat, 
from which it is inferred that the change is not initiated by them. 
He also found that under the influence of sunlight, which killed the 
germs, the rancidity was j^roduced more rapidly. Experiments 
were therefore made with sterilized lard — (1) protected from access 
of air, but exposed to sunlight, to diffused daylight, and kept in 
the dark; (2) with access of air, exposed to the sunlight, and kept 
in the dark; (3) in atmospheres of moist and dry oxygen, carbonic 
acid, nitrogen, and hydrogen. As a general result it may be stated 
that conditions favourable to the production of rancidity proved 
to be the action of light during contact with air. the change being 
induced the more rapidly the more intense the light. Thus it was 

1 Lunde, Centr. Agric, 1892, 554; Stoiner, Milchzeilujig, 1901, 401; :\larcas 
and Hensoval, Rev. Gen. de Lait, 1902, 387. 

- " Bacteria in Milk and its Products," Rebnian, 190.3. 
■' Bull. 45, I'emisi/lv. Agric. Exp. Sta., 1898. 
* Pharm. Zcit., September 13, 1890, 579. 



58 DISINFECTION AND STERILIZATION 

found that sterilized lard, either moist or dry, when kept from 
contact with air in sealed tubes, remained free from rancidity for 
two months, even though exposed to sunlight and warmth. 
Oxygen, both dry and moist, was absorbed freely in the light, the 
fat becoming strongly rancid in one month; but none was absorbed 
in the dark, the fat remaining quite fresh. Nitrogen and hydrogen 
were not absorbed in any case, and the fat remained unchanged. 
Carbonic acid was absorbed in the light, and to a less extent in the 
dark, but the lard only acquired a tallow-like taste, and no odour. 

Since butter as ordinarily made entangles about 10 per cent, 
of water, containing some of the butter-milk, partially preserved 
by salt, no external application of an antiseptic can be depended on. 

Cheese, as is well known, soon undergoes putrefactive changes, 
without a]iparently rendering it unwholesome. Antiseptic, or, 
better, aseptic, wrappers of close canvas, soaked in boric acid, and 
boroglyceride (p. 49) a,re here of value, and unobjectionable, as 
the rind is not eaten. They may prevent the access of the organism 
producing " tyrotoxicon " (p. 39), which is the cause of poisonous 
cheese. Milk which has been heated forms a less solid clot with 
rennet, and Dr. Tjaden stated at the Brussels Congress that in his 
experience, after treatment at 85° C, there was no difficulty in 
ulterioi applications, except that the fabrication of hard cheese 
with it had not been at present satisfactor3\ Klein and Kirsten^ 
showed that milk which had been heated for fifteen minutes at 
75° C. scarcely loses any of its capacity of being converted into 
cheese, but that an addition of calcium chloride shortens the time 
required by the rennet to coagulate the milk. The quantity 
recommended is 1 in 5,000. After the milk has been heated to 
85° C, twice the amount, and after 100" C. two and a half times the 
quantity, will be required to restore the coagulability by rennet. 
The salt is innocuous. 

The United States Department of Agriculture^ recommend the 
immersion of cheese in paraffin wax to prevent the growth of moulds 
and loss of weight on drying. The procedure advised is to dip 
the cheese for from one to ten seconds in a bath of paraffin wax 
heated to 220° F. (190° F. is too low). 

The " patent " preservatives which are occasionally used for 
the preservation of milk, cream, various fats, vegetables, and the 
like are both numerous and complex in character. As the art of 
sophistication of foodstuffs develops, the dexterity in evading the 
various pure food laws of the different countries becomes more 
pronounced and the position of the public analyst becomes more 
1 Chem. Zeit. Rep., 23, [vi.]. 51. 
^ Bureau oj Animal Ind., Circular No, 181, Novpmhcr 1, 1011. 



PRESERVATION OF FOOD 59 

difficult. As an example may be cited the milk preservation 
system, consisting of an aqueous solution of sodium nitrite and 
formaldehyde (according to Monier-Williams, Food Report to 
the Local Government Board, 17, 1912, containing 9-85 and 
0-30 per cent, respectively). Owing to the interaction of the 
nitrite with the tryptophane resulting from the hj^drolysis of the 
milk casein, the usual Hehner's test for formaldehyde, which is 
based upon the formaldehyde-tryptoj^hane condensation, fails, and 
it is necessary to eliminate the nitrite by means of urea before 
testing bv Hehner's method. 



BTBLTOORAPHY. 
MISCELLANEOUS. 

Haley, F. L.: Bleached Flour, Biochem. Bull., 1914, 3, 440-443. 

Utt, C. a. a.: Some Characteristics of Chlorine Bleached Flf)ur, J. Ind. Etig. Chem., 

1914, 6, 908. 
Kellerman, K. F. : Micrococci causing Red Deterioration of Salted Cod-Fish, 

Centr. Bacteriol, etc., 1914, 2 Abt., J. 
Thomson, R. T. : Notes on Flour: (1) Acidity of Flour; (2) Natural and Artificial 

Bleaching of Flour; (3) Sulphates and Lime in Flour, Analyst, 1914, 39, 

519-520. 
Fillers, A. W. N.: Some Metazoon Parasites met with in Food Inspection, and 

their Relationship to Public Health, J. Boy. Sail. Inst., 1915, 36, 154-1.58. 
Robertson, W. G. A.: The Advantages and Disadvantages of Preservatives in 

Food, J. State Med., 1915, 23, 176-182. 
Bentley, R. I.: Contributions of the Chemist to the Preserved Foods Industry. 

J. Ind. Eng. Chem., 1915, 287-289. 
BoRDiNO, A.: Recherches sur I'ultrafiltration du lait, Arch. Ital. dc hiol., 1915, 

65, 417-425. 
Sedgewick, W. T., Barnard, H. E. {et al.): Report of the Committee on Cold 

Storage, Amer. J. Pub. Health, 1910. 6, 1119-1121. 
Bachmann, Freda M. : The Inhibiting Action of Certain Spices on tlie Growth 

of Micro-Organisms, J. Ind. Eng. Chem., 1910, 8, 620-(i23. 
Delepine, S.: Disinfection by Heat. Med. Pre.is and CIrc.. 1916. 102, 8. 
Trotter. A. M. : Sterilization of Tubercular Meat for Human Consum])tion. Med. 

Officer, 1917. 18, 109. 
Martel, H.: Au sujet de I'emploi des substances chimiques pour la conservation 

des viandes. Bee. med. vet., 1917, 318-.324. 
SoERE: Note sur la conservation des viandes et abats, Bev. d'hyg., 1917, 39, 548- 

557. 
Shadwell, G. C. : The Preservation of Food Products by Drying, J. Amer. Soc 

Heat and Vent., 1917, 23, 545-500. 
GoBiNi, C: Nuovo contributo alia sterilizzazione industriale del jatte, Ann. d'ig, 

1917, 27, 729-734. 
Savage, W. G. : Prepared Meat Foods in Relation to Disease Causation, Pvh. 

Health, 1917-18, 31, 79-83. 
BOOBYER, P.: The Proposed Sale of Sterilized Meat, Med. Officer, 1917. 17, 175. 
Sedgeavick, W. T., Nickerson, J. F. (et al.): Fifth Report of the Committee on 

Cold Storage, Amer. J. Pub. Health, 1917, 7, 300-315. 



60 DJSINFKCTION AND STERILIZATION 

Hastings, E. G.: Tho Clarification of :\Iilk, ./. Aw,r. Mnl .-Jwoc. 1917. 68, S99- 

901. 
Bertareli.i, E.: La conservazione delle nova colla sterilizzazione, Hiv. d'ig.esari 

pitbb., 1917, 28, 49-52. 
Gates, I. : Measures to be taken to prevent Contamination of Food by Flies, J. Boy. 

San. Inst., 1917, 38,43-46. 
Straus, Lina Gutherz: Di.seases in Milk: the Remedy Pasteurization. The Life 

Works of Nathan Straus, 2nd edition, N.Y., 1917, Dutton, 383, 8vo. 
NuTTALL, G. H. F., and Gardiner, J. S.: The Histological Changes in Frozen 

Fish, and the Alterations in the Taste and Physiological Properties of their 

Flesh, J. Hyg., 1918-19, 17, 56-62. 
Smith, Gladys E.: Care of Food in Hot Weather, Month. Bull. X.Y. State Dcp. 

Health, 1918, 13, 169-172. 
Fitch, W. E.: Deliydration as a Means of Economic Food Preservation, Amcr. 

Med., 1918, 13, 340-344. 
Kitchen, J. M. W. : The Unremoved Menace of Infected and Contaminated Dairy 

Products, Med. Rev. of Rev., 1918, 24, 342-344. 
Hastings, C. J.: Some Reasons why Milk sliould be Pasteurized, Amcr. Med., 

1918, 13, 422-428. 
BouDOUiN, J. A.: Pasteurization of Milk Supi)ly, Puh. Health J., 1918, 60, 11-26. 
Bertarelli, E., and Bertarelli, M. : Sulla ricerca della formalina nelle .so.stanze 

alimentaire, Policlin., 1918, 25, sez. prat. 153. 
Chapman, R. N.: Measures for Protecting Wheat Flour Substitutes from Insects, 

Science, 1918, n.s. 93, 579-581. 

MEAT. 

Beratrelli, E. : Carni congelate e pericoli d'infexione e di transmissione perassi- 

taria, Gaz. d'osp., 1916, 27, 1074. 
BooBYER, P.: The Propo.sed Sale of Sterilized Meat, J. Roy. Sun. Inst., 1917, 

38, 71-77. 
HowARTH, W. J.: The Sterilization of Unsound Meat, J. State Med., 1917, 25, 161- 

168. 

MILK. 
L.4.VIALLE: Sur les proprietes du lait hypersucre, Tenth Inter. Cong. Med., 1913, 

Lond., 1914, Section V., Therap., pt. 277. 
ZiLVA. S. S.: The Rate of Inactivation by Heat of Peroxidase in Jlilk, Biorlicm. J., 

1914, 8, 656-669. 
Hope, E. W. : The Aims, Objects, and Methods of Sterilization of Milk. Pediatrics, 

1914, 26, 640-648. 
Ayers, S. H., and Johnson, W. T. : Ability of the Colon Bacilli to Survive Pasteuri- 
zation, J. Agric. Research, 1914-15, 3, 401-410. 
Frost, W. D.: A Microscope Test for Pasteurized Milk (Preliminary Paper), J. 

Amer. Med. As.soc., 1915, 64, 821. 
Williams, L. R.: Milk and Communicable Disease, Month. Bull. N.Y. State 

Department of Health, 1916, 32, 280-283. 
Allen, P. W. : Comparison of the Rate of Multiplication of Bacteria in Raw Milk, 

with the Rate in Pasteurized Milk, J. Infect. iJis., 1916, 19, 722-728. 
Cooksey, T.: The Deterioration of Sweetened Condensed Milk, Med. J. Australia, 

1916, 2, 271-273. 
Bahlman, C: Milk Clarifiers, Amer. J. Pub. Health, 1916, 6, 854-857. 
Beattie. J. M., and Lewis, F. C.: Electrical Treatment of Milk for Infant Feeding 

and the Destruction of Bacillus Tuberculosis, J. State Med.. 1916. 22, 174-177. 
Grulee, C. G.: Oxygenated Milk, Trans. Amer. Therap. Sac, 1916-17, 63-67. 



CHAPTER IV 

THE STERILIZATION OF WATER 

The methods adopted for j)urifying water from micro-organisms 
may be roughly divided into two classes : 

1. Those in which the elimination of the bacteria from the 
water is sought, and 

2. Those m which the actual destruction of the organisms is 
accomplished. 

The gradual elimination of a great number of bacteria may be 
brought about by storage, while in some cases sterile water may 
be obtained by filtration. 

Effect of Storage. — The knoA\'ledge of the improvement that 
could be obtained b}' storing water can be traced back to early 
Egyptian times, \\'hilst in Jerusalem and also in India we have 
the remains of tanks and cisterns that were famous in their day. 
]\Iodern reservoirs are of large capacity. The Island Barn and 
Chingford reservoirs of the London jNletropolitan Water Board 
hold respectively 1,000 and 3,000 million gallons, whilst theKensico 
reservoir of New York City has a caj^acity of no less than 40,000 
million gallons. Reduction in the bacterial population of stored 
water takes place by the following methods : 

1 . Sedimentation. — The effect of sedimentation can be enhanced 
b\' adding insoluble substances which, although not bactericidal 
themselves, drag doMii with them the bacteria in the water; their 
action may be classified into three distinct groups : 

(a) Plants and Plant Products. — These may be mucilaginous lil<c 
the quince, elm bark, or gum tragacanth, or they may act by virtue 
of the vegetable acids which they contam, formmg msoluble pre- 
cipitates with the earthy salts in the waters. The clearing nut 
of India, which is the fruit of a tree, 8trycJinos votaforum (Lmn.),^ 
has a high reputation and extensive use among the natives. Others, 
again, are astringent and tanninoid, among which the cinchona 
or Peruvian bark employed from antiquity by the South American 
Indians is the best known. A reference to similar practice is 
found in Exodus xv. 

^ Sec Triuicn's " i'luia uf t'cyluu," 1893, p. 170; " Useful i'lautb of iiidiu," 
1873, p. 408. 

Ui 



62 DISINFECTION AND STERILIZATION 

(6) Inert Chemicals and Powders. — These were first systemati- 
cally investigated by P. Frankland/ who conducted comparative 
experiments on spongy iron, j)owdered wood, charcoal, coke, chalk, 
china clay, lime (as in the Clark softening process), and other 
substances. The general conclusions are that the removal of 
bacteria is only partial, and subject to great irregularities caused 
by convection currents and the varying viscosity of the water. 
The organisms frequently rise from the inert precipitated matter, 
and recontaminate the water ; this is especially the case where the 
precipitant contains a pabulum for the organisms such as the 
phosphates of animal charcoal. 

(c) Chemical Coagulants. — The most usual coagulant is a soluble 
aluminium salt which reacts with the carbonates of calcium, mag- 
nesium, and ammonium present in the water, forming insoluble 
gelatinous hydrated alumina, which combines with colouring and 
other matters, and carries them do\\7i together with the organisms. 
As minerals, natural aluminium sulphate and alums are widely 
distributed, and their use for water purifying is a very ancient 
discovery. The Egyptians, from the earliest times, filtered their 
water through porous earthenware containing alum, whilst the 
Japanese and Chinese are also said to have used this process. 
Pliny- mentions " salsugo terrae," " agua alumina," and Vitruvius 
speaks of " aluminosi fontcs." Ahnnino -ferric is used in large 
quantities for purifying water and sewage at the present time. 
Iron hydroxides and sodium phosphates have also a limited 
application. 

2. By the action of sunlight on the surface of the stored water. 
This will be referred to later. 

3. By ingestion of the organisms in higher forms of life, such 
as protozoa,^ Crustacea,* and infusoria.'^ Strohmeyer has observed 
that a healthy growth of algsi sterilized the surrounding water 
in the course of one day. 

4. By exhaustion of their food supply and poisoning themselves 
with their own excretory products. The pathogenic organisms 
thrive best at blood heat, and are specially susceptible to these 
adhesive influences, together with the efifect of low temperatures. 
The work of Russell and Fuller^ and Houston''' has demonstrated 
the gradual impairing of the vitality of these susceptible organisms 
and the disappearance of one characteristic reaction after another, 

* " Micro-Orgaiiisms in Water," \^. 193. " llisl. Not., lib. xxxv.. cap. 1.5. 
=' Hautemuller, Arch. Ilyg., 1908, 54, 89. 

* Horliaramcr, Arch. Ilyg., 1911, 73, 183. 

5 Stoiivis and Swellengrcbol, J. Ilyg., 1911, 11, 481. 

^ Tram. Amcr. Public Health Assoc, 1905, 31. 

^ ^Annual Reports Lundun MctroydUuii IVultr IJoard. 



THE STERILIZATION OF WATER 63 

together with their virulence, by prolonged storage. This subject, 
including the important engineering and chemical j)roblems involved, 
is more fully dealt with in books on water supply. 



Methods of Filtration. 

Sand Filtration. — Sand filters were first regarded simply as 
strainers for turbid water, and the fineness and cleanness of the 
sand as the most important point. Analyses later proving that the 
soluble constituents were considerably affected, an explanation 
was sought in surface action. Afterwards, from the fact that 
nitrates and carbonic acid were formed, a chemical theory of simple 
oxidation arose, involving a free supply of air. 

Three discoveries, however, threw a new light on the process. 

1. The size of the finer mineral particles is only about t ornTTyo in'^'h 
(0-25/^), and that of most bacteria ryj^^o inch, or larger (/a to 5^), 
but both are smaller than the interstices between the grains of 
even fine sand; consequently it follows (a) that the clearing is not 
accounted for by simple straining, (b) that the organisms would be 
retained first. 

2. Piefke in Berlm, about I88G, found that sterilized sand 
effected hardly any purification, and did not retain microbes. It 
had previousl}- been noticed that sand filters did not become 
efficient for some days after relaying. 

3. When the oxygen or air and the water were sterilized, little 
or no oxidation of organic matter occurred. 

It was proved, therefore, that for the proper mechanical and 
chemical effects the action of organisms is essential. It must be 
remembered that some organisms have long flagella, while a large 
number, such as diatoms and bacteria, are normally surrounded by 
a gelatinous envelope which greatly increases their size, and enables 
them to adhere to surfaces, so that in a short time the sand in a 
new filter becomes covered with a living slimy layer which entangles 
suspended matters and effects the main part of the purification. 
This is called '" schmutzdecke," and sometimes the " schlamm- 
decke," or mud-covering, and until it forms the filtration is in- 
efficient. 

In the under layers of sand the nitrifying organisms, A\]iith 
work best in the dark, act as they do in soils, causmg oxidation, 
and producing nitrates by the aid of the dissolved oxygen. Green 
alga3 in their growth evolve oxygen, and so increase the amount in 
solution, while bacteria as a rule diminish it. Although the chief 
removal of organisms occurs in the " schmutzdecke," the lower 
layers of sand are not inactive, as Reinsch has shown at x\.ltona. 



64 DISINFECTION AND STERILIZATION 

For an example, he gives the average number of organisms per c.c. 
as: Raw water, 36,000; just under the sehmutzdecke, 1,800; at 
bottom of sand (35 inches), 44. 

The proportion of micro-organisms removed by the sand filters 
of water companies shows ordinarily a variation between 95 and 
98-5 per cent., but should be well up to the latter figure. Koch laid 
down as a limit that water containing more than 100 organisms 
per c.c. must not be allowed to pass into consumption. That 
when carefully used these filters afford a remarkable protection 
against pathogenic species was proved by experience in the cholera 
epidemic of 1892 at Hamburg and Altona,^ when in Altona the 
water was filtered carefully, in Hamburg not. Although the 
original water supplied to Altona was worse than that of Hamburg, 
the deaths in Altona were 221, in Hamburg 1,250, per 100,000. 
At the end of 1892 an outbreak occurred in Altona owing to a 
filter-bed bi caking down, a proof that the slightest imperfection 
in the manipulation is a constant menace during any epidemic. 

"Mechanical filters," of which there are various tj'pes (see 
Water Supj)ly), are much used, especially in America, for purifica- 
tion on the large scale. The water is driven through a much smaller 
bed of sand or crushed quartz at about forty tunes the rapidity. 
Coagulation by sulphate of alumina, followed by lime, is generally 
adopted as a preliminary to form an artificial " sehmutzdecke," or 
top film. Used in this way, they are capable of removing 90 to 
99-5 per cent, of the organisms. With or without coagulants, they 
are specially suitable, in cases where the supply has to be drawn 
from turbid sources, for preparing the water for the ordinary slow 
sand filtration, as they are much more easily cleaned and renewed 
than large filter-beds. 

Sterilizing Filters. — Sand and mechanical filters in good condi- 
tion, and under favourable circumstances, occasionally yield a, 
sterile effluent. But such a result cannot be depended on, and 
to secure it a much finer medium must be employed. At this date 
it is hardly necessary to refer to the large variety of filters formerly 
trusted, which have been proved by Plagge, Sims Woodhead, 
Guinochet, Johnston, and others, to be quite inefficient in pre- 
venting the passage of bacteria, though they may render the water 
bright in appearance. These filters were really worse than useless, 
as they formed a cultivation bed for organisms of all kinds, in- 
cluding path()g(>nic forms, and actually sometimes increased tlu'ir 
jiumbers. 

The only filter that has stood all tests is the Pasteur-Chamber- 

1 Kuch, Zcilach. llyij., 14, 3'J3; 16, S'J. 



THE STERILIZATION OF WATER 05 

land. This so-called " candle filter " originated, as is well known, 
from Pasteur's laboratory experiments in preparing germ-free 
broth cultures for bacteriological investigations, when Chamberland 
introduced the practical application to drinking-water of the tubes 
that Pasteur had found efficient for excluding bacteria. The same 
remark applies to these as m connection with sand filters, that 
the removal is not accounted for entirely by a mere straining by 
the material, as the bodies of some of the organisms are smaller 
than the pores, though the gelatinous envelope of the bacteria and 
their entanglement, joined with the much greater fineness and 
evenness of the medium, and the consequent slowness of filtration, 
make the removal complete. But there must be also some molecular 
attraction dependent on the material of the tube and its manu- 
facture, as a large number of fine-grained substances, to the naked 
eye apparently identical in texture, have been tried and found to 
be unreliable.^ Even with the Pasteur filter it is stated that " it 
requu'es the highest skill in pottery to produce a uniform result as 
to sterilizing capacity, and some 30 per cent, of the finished tubes 
are rejected on test." Candle filters are manufactured by the 
Sanitats Porzellan Fabrik, at Charlottenberg, and in this country 
several EngHsh-made candle filters have appeared. At present, 
however, there is not sufficient evidence to warrant the belief that 
any of them give the protection against water-borne disease which 
is afforded by Pasteur filtration, and the assumption that they 
function similarly is a very dangerous one for the general public, 
who are unable to distmguish between the forms. 

The methods of purification based on the destruction of 
organisms are divisible into physical and chemical processes of 
sterilization. 

Physical Methods of Sterilization. 

I. Sterilization by Heat. — Boiling is, of course, an efficient means 
on a small scale, but the expense is prohibitive when large quanti- 
ties of water have to be regularly dealt with. In India the Larymore 
boiler has been largely used and found efficient, but the taste of 
the boiled water is often objected to, as the liquid not only is flat 
and free from dissolved gases, but has frequently a burnt flavour 
from overheated organic matter. A successful heat sterilizer must, 
therefore, be so designed as not only to yield a Ava.tcr A\hich is 
bacterially pure, but to ensure the preservation of the natural 
flavour and gases of the water, and, further, some means of regen- 
erating the heat required for effecting the sterilization must be 

^ Hesse, Zeitsch. Hyg., 1011, 70, 311; and Bullock, Craw, and Anderson, ./. Ilijg., 
1906, 1908, 1909; Hofstiidter, ArcJi. Ilyg., 1905, 53, 205. 



66 DISINFECTION AND STERILIZATION 

included. One of the earliest methods for carrying out this object 
consisted in heating the water to a temperature of about 115° C. 
in a closed vessel (when the natural gases are not evolved, nor are 
the salts deposited to any considerable extent), and using the out- 
going water for warming that entering the boiler by means of 
interchanging coils. In such a system the heated water is not 
exposed to the air, and is therefore kept free from any subsequent 
contamination. At Brest, in 1892, apparatus on these lines by 
Rouart and Geneste-Herscher and Co. were officially tested. Later 
Professor Vaillard, of the Pasteur Institute in Paris, and Mons. 
Desmaroux devised similar plant, so arranged that all the water 
passed through a superheater in which it was subjected to a minimum 
temperature of 113° C. for about five minutes. Connected with 
the superheater was a temperature exchanger made of a double 
series of spiral compartments, which cooled the sterilized water to 
within a few degrees of the supply. This apparatus has been used 
at the Sanatorium de St. Trojan in Paris. When made on a large 
scale, the economy in fuel is greater, and at Tsaritzine, on the Volga, 
a large installation is heated from a common source, and there 
produces enough sterilized Avater for a population of 10,000. 

A difficulty in all such apparatus, however, is met with in the 
deposition of salts from hard Avaters in the temperature exchanger, 
and as, for perfect cooling, the tubes or compartments must neces- 
sarily be small, there is danger of such tubes blocking with the 
deposit, unless facilities for frequently cleansing are provided. 
More recently the heat sterilization of water has been effected in 
plant in which the water is not heated under pressure, but is brought 
to the boil, and at once passes over a weir into a temperature 
exchanger. Since the water only boils for a few seconds, it retains 
most of its origmal gas and taste, and the apparatus can be so 
constructed that it is impossible for any water which has not been 
boiled to pass into the cooler. The Forbes apparatus is designed 
on these lines. ^ A constant level in the tank j^laced above the 
exchanger is ensured by a float-actuated valve which maintains the 
water-level in the boiler slightly below a cup placed therein. The 
valve-box therefore regulates the flow of the water, irrespective of 
the pressure on the surface, in a similar manner to the bird fountain 
or aerostatic feed apparatus used when a constant level is required 
with a small volume of water. The sterilizer operates at a rate 
which will be dependent upon the size and intensity of the flame 
of the burner, as the water will boil over the cup at different rates. 
It is obvious that, although the speed in a given apparatus depends 
entirely upon the rate of boiling or the heat applied, the tempera- 
1 U.S. patent, Decombor 13, 1K<)8. 



THE STERILIZATION OF WATER 67 

ture of the sterilized water will correspondingly vary if the same 
cooler be always used. It was said to be practicable to build a 
sterilizer in any size, even to the extent of sterilizing the water supply 
of a city or town, at a cost of from 13s. 5)d. to 14s. per million 
gallons, including interest on the plant, fuel, and labour. In such 
apparatus in America, 1 pound of coal has sterilized from 2,000 
to 5,000 pounds of water. The Forbes sterilizer claimed as follows : 

(1) A source of water supply having a level maintained beloAv 
that required for causing the water to pass entirely through the 
apparatus. 

(2) The application of heat to a part of the water in the api^aratus 
at the point reached by gravity (due to the maintained level in 
the source of supply) until ebullition is produced, thereby causing 
the water to rise and pass through the remainder of the apparatus; 
and 

(3) The transference of the heat from the hot water passino- 
from, to the cold water passing to, the point where the heat is 
applied. 

In this country the LaA^Tence sterilizer has been in use for some 
time at Guy's Hospital and elsewhere, and accomplishes the object 
somewhat differently from the Foibes apparatus. It has a vertical 
boiler in which are placed depositing trays of iron above the water- 
line, and a series of plat?s, termed " locators," in the boiling water. 
The inflow passing down\\'ards is met by the steam produced below, 
and is thus progressively heated until it attains the highest temj^era- 
ture, and the most violent ebullition, in the lowest compartment. 
The gases in solution are expelled, and the carbonates of lime and 
magnesia are almost entirely deposited as a friable scale upon the 
trays and locators, which are removed from time to time for cleaning 
or replacement, while the small amount of sludge collecting at the 
bottom can be blown out without trouble. The softened liquid 
then passes upwards through an outer division of the cylinder 
to an interchanger, where it gives up its heat to the raw inflowing 
water, and finally issues at a temperature depending upon the rate 
of boiling, so that the heat is in this way almost wholly recovered. 
Very little attention is required, and trouble with reagents is 
avoided. When used for softening boiler-feed water, it is found 
best to cool only to 17° C. above the inflow to obviate the loss bv 
radiation involved in storing or transferring hot water. In common 
with the Forbes pattern, the rate of flow is regulated by the heat 
applied, but it is clear that w ithout special provision un.sterilized 
water can pass througli into the heat chamber, and so contaminate 
the supply. By inserting in the boiler a metal |)late fitted to a 
carefully adjusted valve, the steam produced in the boiler can be 



68 DISINFECTION AND STERILIZATION 

made to regulate the flow of the water, so that to a certain 
extent the apparatus can be made as automatic as the Forbes 
plant. 

Results obtamcxl in working different forms of heat sterilizers 
in our own laboratory show that, even with very varying rates of 
flow, sterile water can with care be usually ensured. At the same 
time, when working rapidly, the amount of dissolved gas in the 
treated water is much reduced, but the fault can be remedied, if 
required, by storing in carefully cleaned vessels protected by 
cotton-wool. 

The chief objection to heat sterilizers at present is the blocking 
up of the interchanger when used with dirty or hard waters, and 
in army service the difficulty of providing fuel. Further, heat 
sterilizers of non-pressure types clearly do not ensure the destruc- 
tion of spores, and therefore can only be used as a precaution 
against cholera and typhoid, and other non-spore-bearing patho- 
genic organisms. With candle filters (p. 65) it is clear that 
theoretically the transport problem is reduced to a mmimum, as 
there is no expenditure of any material during the period of use, 
so that the weight required is simply determined by the actual 
filter itself and necessary accessories. On the other hand, for 
small units and individual troopers, when away from their base, 
the weight of even a small pocket filter is considerable, and the 
advantage then lies in some form of chemical sterilization. 

II. Sterilization by Light. — The beneficial effects of sunlight on 
water were noticed at a very early date. As early as 1640 Dr. 
Hart cautioned his readers against the use of well-water " to which 
the sun hath no reflection." While the growth of green algaj can 
be prevented by excluding light from water during storage, yet 
the beneficial effect of light in destroymg the germs of disease is 
in this way hindered or lost. The algae may become troublesome, 
but are not dangerous like the pathogenic bacteria, and as the 
former undoubtedly cause a disappearance of some of the organic 
matter present, when not superabundant or of objectionable species, 
conferring odours or tastes, they are actually useful. 

The germicidal power of sunlight is strongest beyond the visible 
spectrum in the ultra-violet, while ordinary daylight and most 
forms of artificial illumination, so far from retarding growths, will 
often assist them. 

Downes and Blunt^ were the first to investigate systematically 
the sterilizing action of light on contaminated water. They found 
direct sunlight speedily fatal to most bacteria, and even in a little 
longer time to spores, while diffused light is harmful in a less degree. 

1 Proc. Boy. Soc, 1877, 26, 488. 



THE STERILIZATION OF WATER 69 

Dieudonne-i showed that the germicidal power of the light increased 
as it progressed from the red to the ultra-violet. 

Westbrook, at Marburg in 1900, showed that the action was not 
simply a physical one, but depended greatly on the function of the 
chemical rays in promoting oxidation; therefore free access of air 
is necessary. Observers have found that the inhibitive property 
of direct sunlight may penetrate in clear water to 6 or 8 feet, but 
with any turbidity it is soon arrested. Buchner's^ results with 
Vibrio cholerce, B. typhi, and B. pyocyaneus, were that light is 
germicidal down to 1-6 metres (5 feet), but that its antagonistic 
effect on some bacteria in clear water did not become imperceptible 
till a depth of 3 metres (9-8 feet) was reached. Whipple^ remarks 
that disinfection by sunlight is not a factor at depths greater than 
a few feet, although in the Tropics the effect may bo more marked 
and even become of importance.* 

The earliest scientific study of the biological effects of ultra- 
violet light was by Finsen and his pupils, who applied the bacteri- 
cidal effect of the rays, produced artificiall3^ to the curing of lupus 
and other fungoid diseases. The germicidal power of light in 
general, and of ultra-violet light in particular, having been proved, 
the next point was, as always, economical generation and use. 

Ordinary gas burners, incandescent mantles, or glowing fila- 
ments are very poor in such radiations, but, on the other hand, 
incandescent vapours are frequently rich in this actinic light, 
especially those of iron, aluminium, and mercury. Early experi- 
ments were carried out with electrodes of iron, or iron with alu- 
minium cores, for the production of an electric arc between the 
ends. The water was allowed to run in a thin film exposed to the 
rays, but the time of exposure to the light was generally not suffi- 
cient and difficulties occurred in the removal of the oxides of iron 
or aluminium formed. At Neuilly-sur-Marne a lamp of this type 
has sterilized a cubic metre of water with a current consumption of 
only 20 watts. 

Leo Arons^ was the first to make successful use of glo'wing 
mercury as a source of light. In 1895 M. Chas. Lambert sub- 
mitted to the Paris Service des Eaux the description of a process 
for " subjecting water to an intense illumination, while opposing 
no obstacle to the ultra-violet rays of the spectrum," and later 
M. de Mare patented " the use of quartz lamps m iih mcicurv 
vapour for sterilizing potable liquids such as wat(>r." 

1 ArO. Kais. Gesund., 1894, 40.'). - Arch, llyg., 1893. 17, 179. 

^ Internat. Cong. App. Chem., N.Y., 1912. 

* Clciuesha, " Bacteriology of Surfaco Wateis in i\w Ti()i>io.s," 1912. 

5 Wicd. Anil., 1892, 47, 7G7. 



70 DISINFECTION AND STERILIZATION 

In 1901) Drs. Coui-mont and Nogicr communicated to the 
Academy their research on the subject, which was followed by 
many others, proving that the pathogenic and other organisms were 
destroyed by short exposure, not connected with ozone formation, 
as has been supposed ; but the water had to be specially freed from 
suspended matter, since particles screened the microbes from the 
irradiation. It is because ordinary glass, though transparent, 
absorbs a great part of the rays that the lamps are constructed 
of fused silica. To utilize all the available light, the lamps are 
frequent!}^ entirely immersed in the water to be sterilized, and in 
many cases they are protected by a thin transparent envelope, 
which, of course, involves a small air space and some absorption 
of the rays. With immersed lamps two difficulties occur : in the 
first place, after a while the lamp becomes covered with a scale of 
deposited earthy carbonates and iron, blocking out the rays: 
secondly, the temperature is considerably lowered by the immersion, 
and the light emission for a given watt consumption seriously 
reduced. Consequently the lamp is often placed directly above 
the water, although this involves a sacrifice of energy. Dr. Reck- 
linghausen remarks: " In such a system, and in spite of reflectors, 
only perhaps 30 or 40 per cent, of the light emitted entered the water 
and obtained its effect." 

The use of baffle plates makes the water pass several times under 
the influence of the rays, thus lengthening the period of exposure. 
The action is very little affected by the temperature of the water; 
even ice, if transparent, can be sterilized in about the same time 
as water. 

As has already been mentioned, the action is not dependent on 
the production of ozone, and is not dependent on the amount of 
dissolved oxygen in the water; only minute traces of hydrogen 
peroxide are formed after several hours, whereas the sterilization 
takes only a short exposure. 

Various classes of organisms are not all equally sensitive to the 
rays, just as they are not equally sensitive to heat or to chemical 
agents, B. suhtilis and tetanus being the most resistant of those 
tested. 

The following table, from tests carried out in the Sorbonne Univer- 
sity, illustiates the effective range of the rays in an ordinary water 
infected with B. coU. but free from colour and suspended matter: 



]>,Ma ncc Jrom Lamp. Sterilize wi 

10 centimetres 

20 ., 

40 „ 

60 „ 



Number of Secovds required to 
th a 220 Volt Lamp. 

1 

4 
15 
30 



THE STERILIZATION OF WATER 71 

It will be noted from these figures that the time of sterilization 
does not follow the '" law of the inverse square of the distance " 
\\ith any great degree of accuracy. This rather surprismg result 
has been confirmed quite recently by some careful experiments by 
R. Scharff at Massachusetts, who came to the conclusion that no 
such generalization was to be found between distance and sterilizing 
poAver. 

The system of Henri Heilbronner and Recklinghausen has been 
installed in many toAms in France, the largest installation being 
at Amiens, dealing with nearly 4.000.000 gallons per day. Small 
installations are in use in various hospitals and at a public drinking 
fountain in Paris. A transportable plant has been adopted in 
the French Armj'.i 

III. Chemical sterilization is mainlj' to be regarded as an emer- 
gency method. The considerable total expense for even the 
cheapest chemical, apart from the labour and trouble mvolved, 
must necessarily render the operations costly. Under special 
circumstances, however, this method may become useful and even 
necessary. 

Oxidizing agents have generally been favoured on the ground 
that oxygen is the natural purifier, but we have seen that oxidation 
is only a part, and not the most essential one, of natural purifica- 
tion. Their great disadvantage is that thej^ are largely consumed 
by easily oxidizable substances, which may be phAsiologically 
harmless, before an excess can be established to act on bacteria; 
hence the Avater must be prepared beforehand by remoA'al of most 
of the organic matter. The \^ariations in the amount recorded as 
necessary by different observers are due in great part to this cause. 

It is obvious that for drinking-AA'ater only such reagents are 
available as do not affect its Avholesomeness or palatability. In 
AA-ater supplies, hoAA-ever, from Avhicli the greater part of the organic 
matter has been remoA^ed by some preliminar}^ process, the quantity 
of some oxidising agents required is so exceedingly small that it 
Avould have no injurious effect on the consumer. Among these 
substances the manganates and permanganates have long been 
popular. Potassium permanganate AA^as emploj-ed on a large scale 
by Lereboullet for the drinking-water of the soldiers in the Franco- 
German War of 1870; at that time it Avas not a question of destroy- 
ing the organisms, but solel>' the organic matter present. In India 
it has been Avidely used for purifying aacIIs and tanks, these being 
regularly " pinked " by officials as a defence against cholera, 
Hankin considering it to be a specific for cholera bacilli;- recent 
reports on the efficiency of the practice haA^e, hoAvcA^er, been un- 

1 La Science ct Vie, December, 1913. - Ihit. Med. J., March IG, 1895. 



72 DISINFECTION AND STERILIZATION 

favourable. Its action on bacteria lias been examined l)y numerous 
observers. Kocli^ states that it is effective only in concentrated 
solutions. Calvert" found 1 in 125 necessary to prevent growth in 
bouillon for six days. Miquel states that 3-5 grammes were 
required to sterilize 1 litre of beef-tea, or 1 in 268. Demarquay, 
from surgical experience, considered that 1 in 1.000 " disinfected- 
very well, but its action was rapidly exhausted, and it did not 
prevent the secretions from retaining their virulence." Vallin was 
of similar opinion,^ also Blyth* and Klem.^ Dr. A. H. Burgess 
found that 1 in 40 was required to destroy B. coli communis in 
one hour.^ 

Lepeyrere, at the Paris International Congress of Hygiene in 
1900, suggested the use of a mixture of potassium permanganate, 
sodium aluminate, and sodium and calcium carbonates for the 
purification of water in campaigns. After standing a few minutes, 
the water was passed through "purified peat fibre" mixed with 
manganese dioxide. The process was examined by Dr. A. Warner^ 
with water infected with B. typhosus ; even Avhen filtering slowly it 
did not get rid of the pathogenic bacteria. 

Permanganate, together with lime, salts of iron, and carbonic 
acid, has been successfully applied in the Linden process. It Avas 
adopted by the town of Ghent before the war to purify for drinking 
purposes the water of the River Scheldt, which is particularly foul 
and polluted. 

Ozone. 

Ozone has the exceptional advantage of being easily obtained 
everywhere from atmospheric oxygen, and recent progress in 
ozone generators and electric supply leads to the belief that this 
gas may be economically produced. In several directions it has 
been used for public supplies on a large scale, and it promises to 
be further extended as 'a " finisher " in the sterilization of water. 
The chief difference between the action of ozone, O3. and of atmo- 
spheric or ordinary oxygen, O,,, is that the latter ^\\\\ not act on 
most varieties of organic matter without the help of organisms — 
either direct, in their processes of life, or mdirect, through a special 
class of enz3^mes, called oxydases, that some of them produce. 
In the sterilizing function of ozone only one-third of the oxygen 
actually contained in it ranks as " available " oxygen. The gas 
attacks metals, india-rubber, gutta-percha, and wood, and is 
thereby itself destroyed ; hence apparatus for its production, storage, 

1 Mittheil. Kais. Gcsundh., 18S1. - Brit. Med. J., March Ki, 1895. 

^ Desmfectants, 1882. * Proc. Roy. Soc, 1886. 

^ Stevenson and Murphy's "Hygiene," 1893, p. 61. 

8 Lancet, June, 19UU. ^ public Health, July, 1901, 704. 



THE STERILIZATION OF WATER 73 

or conveyance, must be constructed of stoneware or glass, or, 
less advantageously, of protected metal. The air to be ozonized 
is first freed from dust by cotton-wool strainers, then dried, to 
avoid the formation of nitric acid, and passed through a cooled 
sjsace traversed by a silent electrical discharge. Sparks should be 
avoided, as heat reconverts ozone into ordinary oxj^gen. To 
obtain a strength of 7 per cent, (the highest mentioned) was found 
by M. Chassy to cost in electric energy ninety times as much as 
h per cent., so that if economy be considered, it is best only feebly 
to enrich the oxygen, while accelerating the circulation of gas. 
Ozonizers are of a number of forms. 

Baron Tindal, about 1896, proposed to the municipality of 
Paris to sterilize, by means of ozone, 5,000 cubic metres 
(1,100,000 gallons) of crude Seine water daily. His first experi- 
ments were made at Oudshoorn, Holland, in 1893. The system 
was installed experimentally in Paris, Brussels, and Ostend, and 
was proved by the reports of Dr. Van Ermengem and others to 
sterilize at a reasonable rate canal and other waters which had been 
previously filtered. 

In 1898 Siemens and Halske erected an experimental plant at 
Martinikenfelde, near Berlin, and it was found necessary to fi.rst 
remove (parser impurities by a quick filter. The original Avater 
from the Rivei Spree showed 100,000 to 600,000 organisms per 
c.c. ; the effluent was sometimes sterile, and never contained 
more than 2 to 9 organisms per c.c. That the water is not 
always sterilized may be due to the fact that the ozonization 
is less than the amount of 4 grammes per cubic metre which Van 
Ermengem found to be effective. 

Marmier and Abraham's apparatus, installed at Lille in 1898, 
has a plate ozonizer with cooled electrodes, working Avith 40,000 
volts, and the w^ater is sterilized as above in a masonry tower. 
The Commission who approved of the apparatus and its results 
reported that only a few spores of highly resistant and harmless 
B. suhtilis were left, and that these disappeared on about twelve 
hours' storage, the water remaining sterile in the air for four days, 
though showing no trace of ozone a few minutes after issuing from 
the apparatus. No antiseptic compound was formed, as water 
bacteria were not inhibited when added to the liquid after tr(>atment. 
The report concluded that of the few organisms which escape 
destruction in the tower, nearly all succumb after some minutes 
in the reservoirs. The only other alterations in the water were a 
decrease in the organic matter and an improvement in physical 
character. 

Eroelich, about 1890, proved that ozone destroyed micro- 



74 DISINFECTION AND STERILIZATION 

organisms, and that its action was most effective in presence of 
moisture. He showed^ that ozonization sterilizes water, oxidizes 
nitrites and sulphuretted hydrogen, and throws down iron as ferric 
hydroxide, and made the important suggestion that ozone should 
follow filtration. About the same time Kowalowski and Krukow- 
itsch in Russia, and Christmas in Paris, investigated its bactericidal 
power. Ohlmuller, in 1892,^ found that water from the River 
Spree was sterilized in ten minutes by 86-6 milligrammes of ozone 
per litre; sewage was not sterilized in an hour by 156-3 milligrammes; 
but distilled water to which bacteria in great numbers had been 
added was sterilized most easily, anthrax, typhoid, and cholera 
bacilli being killed in two to ten minutes, proving that where water 
was not too contaminated with organic impurities, ozone destroj^ed 
completely these pathogenic bacteria. Ransome and Foulerton, 
in 1903,^ even succeeded in killing bacteria in milk. 

Ozone is now rather extensively used in Europe for sterilizing 
partly purified water. In 1908 one of us was called upon to 
examine the De Frise system at the Paris waterworks at St. Maur, 
and found very successful results. The River Marne water, after 
ordinary sedimentation and filtration through gravel and sand, 
was still unfit for a supply, but by afterwards ozonizing it gave a 
well-aerated brilliant liquid of natural bluish tint, and quite 
inodorous, containing per c.c. only one or tw^o innocuous 
organisms of the B. subtilis type. The B. coli test became 
invariably negative, although altogether 1,580 c.c. were ex- 
amined, with a maximum of 200 c.c. at one test. It was 
found that 57 kilowatt hours per million imperial gallons 
were required for the sterilizing operation, and 76 kilowatt hours 
for pumping. These figures would be reduced to 47-5 and 63-4 kilo- 
watt hours respectively per million United States gallons. The 
De Frise apparatus used Siemens-Halske ozonizers with a simple 
and efficient ozonizing tower, and a circuit by which ozone escaping 
after action was returned and used again, thereby effecting an 
important economy. The Paris municipality decided in July, 1910, 
that the part of the city drinking su]iply derived from the Marne 
(about 20,000,000 gallons daily) should, after coarse filtration, be 
sterilized by ozone, half by the De Frise and half by the combined 
Otto process. The latter employs "emulsers," which are in- 
jectors effecting a mixture of ozonized air with the water, the 
action being com]ileted in '■ columns of self-contact." Ozone 
sterilization has l)(>en installed in about thirty French towns, in 
Rumania for the Danube, at Petrograd for the Neva, at two 

1 KUxtrolcchn. Zcit., 1S91. 26. '^ Arbcii. Kais. Gesund., 8, 229. 

^ Pruc. Roy. Soc, February 14. 78. 



THE STERILIZATION OF WATER 75 

waterworks in Holland (the pioneer), Belgium, Germany, Italy, 
Spain. Brazil, and Egypt, and experiments have been undertaken 
at Darjeeling in India. 

Other processes differing in mechanical details are the Vosmaer, 
tried at PhiladeljDhia, and the Howard-Bridge, at Lindsay. Ontario, 
Canada. 

One of the largest plants is that at Petrograd, Russia, for 
1 1.000,000 gallons per day. The water is first treated with sulphate 
of alumina, then passes on to thirty-eight sand filters at a rate of 
1,000 gallons per square metre of filtering surface per hour, and 
finally enters the five sterilizing towers along with ozonized air. 
There are 128 Siemens-Halske water-cooled ozonizers. The air is 
freed from moisture by refrigeration, and is ozonized to the degree 
of 2-5 grammes per cubic metre. The total cost from the raw 
river to the finished water was recorded in 1911 asO-86d. toO-97d. 
per 1,000 gallons. At St. Maur, Paris, M. Colmet Daage estimated 
that the cost, under the most favourable circumstances, was 0-3 Id. 
per 1.000 gallons, excluding interest, amortization, and repairs. 
At Nice, where cheap water power is available, the average annual 
cost is given as 0-164d. per 1,000 gallons, and at Rimiez, where 
there is, besides, no pumping, it Avas only 0T2od. A portable 
ozone purifier has been adopted by the Spanish Government for 
the water supply of armies in the field. 

The preference for ozone as a water-sterilizing agent has been 
hindered by several difficulties. One is the question of expense. 
In this regard the manufacture has been considerably cheapened. 
Another is that it has to be applied in the gaseous form diluted with 
air, so that a large quantity of inert gas must be pumped, and m ith 
this admixture the ozone does not very readily dissolve. The 
latter fact has been overcome by using towers and saturaters, as 
mentioned above. Moreover, the conversion of oxygen into ozone 
is a reversible action, requiring a number of precautions as to detail. 
In spite of the numerous researches, the best conditions are not yet 
fully agreed on; therefore, we have not reached finality in the 
economy of ozone production. It is stated that " the best results 
ever obtained with a silent discharge apparatus gave 36-7 grammes 
of ozone per kilowatt hour, the theoretical yield being over a 
kilogramme." A certain amount of the loss is due to the formation 
of ultra-violet light in the machine. When an ozonizer is acting 
properly, the interelectrodic space has an almost uniform violet 
illumination without any s])arking. Regener^ showed tliat the 
ultra-violet light limits the concentration of ozone., (Sep Ozone.; 

Siemens and Halske have several devices for preventing corro- 

1 Ann. Phijsik., lUUO, 9, U»33. 



76 DISINFECTION AND STERILIZATION 

sion of the metallic parts of the apparatus. British patent 17,7s7 
of 1910 reverses the usual procedure by drawing ozonized air 
through the Avater instead of forcing it through from below, so that 
the main work shall be done, and the ozone almost entirely used up, 
before entering the i:)um])s. This appears expensive mechanically. 
Their French (international) patent, 431,402 of 1910, introduces 
small quantities of water into the pumps at the same time that 
the gas is admitted. 

The Peroxides. 

Hydrogen Peroxide has not found any extended application as 
a water-sterilizing agent, although at first sight, owing to the fact 
that on decomposition water is the only resulting product, it would 
appear to be as ideal a reagent as ozone. 

The balance of recent researches, especially those of Reichet,^ 
has proved, however, that a concentration of 1 in 1,000 is neces- 
sary, and its cost and instability, the imj)urities of the commercial 
article, and the difficulties of transport of large quantities of a 
liquid, interfere with its use for sterilizing water. 

Sodium Peroxide is a jDowerful oxidizing agent which generates 
HoO., when dissolved, and, being a solid, is free from the last-named 
objection; either when used alone or in conjunction with the usual 
softening agents, such as lime or soda, it has advantages in that 
it sterilizes as well as softens. As by combination Avith softening 
so much of the organic matter is removed, the action of the hydrogen 
peroxide on the bacteria is better ensured. With the same object, 
where the organic matter is high, partial softening by ordinary 
methods can precede the addition of sodium peroxide. This jorocess 
has the further advantage that the final effect is only a slight 
addition to the natural sodium salts, and that acid moorland waters 
are naturalized and bleached, and their plumbo-solvency removed. 
Appended are two examjDles of satisfactory results that have been 
obtained in our laboratory : 

A. London tap -water, containing an average of 30 organisms 
per c.c. ; permanent hardness, 3-71 parts per 100,000. To separate 
quantities were added (1)3 parts per 100,000 caustic soda, (2) 3 parts 
per 100,000 of sodium peroxide. 

13. Somewhat impure water, containing i)3 organisms per c.c; 
permanent hardness about 4 parts. (1) Three parts per 100,000 of 
caustic soda, (2) 1-5 caustic^ and 1-5 sodium ]K'roxide. 

Blanks were mounted in each case, and all the waters after the 
first shaking were allowed to settle, in series A at about 10° C, 
in series B at 18°. The number of organisms per c.c. were as follows : 
1 Zcitsch. Hyg., 1908, 61, 49. 



THE STERILIZATION OF WATER 



i I 



A. 


B. 


Hours. 


Blank. 


(1-) 


(2.) 


Blank. 


(1) 


(2.) 


1 


31 


28 


11 


115 


94 


62 


^ 


27 


18 


1 


103 


100 


34 


24 


19 


16 





173 


117 


2 



(1) Shows the result of softening alone; (2) that of softening with the aid of 
sodium peroxide. The multiplication of organisms in B (1) at the liigher tempera- 
ture is in accordance with what we have previously noticed in simple softening. 

Calcium Peroxide, patent 17,460 of 1900, is sold under the 
name of bicalzit. Hetsch finds it to be more effective than hydro- 
gen peroxide, typhoid organisms being killed by ^ part per thousand. 
Freyringe and Roche in 1905 advocated its use for drinking-Avater. 
recommending the addition of small quantities of sodium bi- 
carbonate, with subsequent filtration tlu-ough manganese dioxide 
to remove the calcium carbonate formed, and any traces of hydrogen 
peroxide not decomposed in the water. They state that two or 
three hours is necessary to ensure sterility. 

Magnesium Peroxide is sold for sterilizing mineral waters. A 
commercial preparation is stated to contain about 33 per cent, of 
the pure peroxide, the rest being magnesium carbonate. Croner^ 
obtained sterilization generally, but not always, with 0-7 to 
1 gramme jNIgOo per litre. Dr. Proskauer and others- advise the 
emplo3rment of MgOj. 

Lime. — As early as 1885 P. Frankland^ observed a removal, 
and to a certain extent a killing, or at least inhibiting, of organisms 
in waters softened with lime. 

The fault in this respect of a mere softening with a minimum 
dose of lime is that the action is only a partial removal of the 
organisms, and that only some of them are killed. It has already 
been pointed out that when sedimented for some days the mechani- 
cally carried down or inhibited bacteria rise again and develop 
in immense numbers in even the upper layers. 

Kruger* confirmed the above-mentioned after-distribution and 
multiplication in a number of waters. In a typical instance he 
added slaked lime equivalent to 14 grains per gallon of CaO, by 
which the water was rendered strongly alkaline. The average 

1 Zeitsch. Hyg., 1908, 58, 4S7. 

2 Kong. Mittheil. Leh. Uyg., 1911, 1, 390; Young and Sherwood, .7. Ind. I'.tuj. 
Chem., 1911, 3, 495. 

3 Proc. Roy. Sac, 1885. * Zeitsch. Ilyg., 1889. 



78 DISINFECTION AND STERILIZATION 

number of organisms per c.c. was, in the milimed water: 
first day 5,142, third day 21,344, twenty-third day 15,714; 
in the limed water: first day CG2, third day 824, twent^'-third day 
1,580. In the first case the reduction in the longer time is probably 
due to the well-known effect of storage. In the treated water the 
multiplication has continued, though the numbers are much less; 
therefore the excess lime, as Frankland remarks, has acted as a 
bactericide. Dr. Burlureaux of Paris is also quoted as having 
sho^^■n that bacteria are actually destroyed in the softening M'ith 
lime. Liborius* and Pfuhl' came to the conclusion that 1 gramme 
of C"aO per litre was an effective germicide for ty2)hoid organisms. 
Grether,^ Dunbar and Zurn,* on the other hand, could not obtain 
sterility with this and even larger amounts. 

Use of Excess Lime. — ^Dr. Houston-^ has taken the method up, 
and states: " I have found that quicklime (about 75 per cent. CaO) 
added to raw Thames water in the proportion of 1 part of quick- 
lime to 5,000 parts of water fO-02 per cent.) kills B. coli in five to 
twent3'-four hours." In his Eighth Report, 1912, he records 
further experiments on " excess lime " as a water sterilizer, and 
summarizes strongly in its favour, saying: "Fifteen pounds of 
quicklime, costing l|cl., would be added to 7,500 gallons of raw 
unstored Thames water. This would kill within twenty-four hours 
the B. coli, and inferentially, but certainly, the microbes also of 
epidemic water-borne disease — e.g., the typhoid bacillus. The 
water would also be improved considerably as judged by chemical 
and physical standards. The excess of free lime (about 0-007 per 
cent. =4-9 grains per gallon of CaO=a hardness of 8-8° Clark) 
would then have to be neutralized with 2,500 gallons^ of adequately 
stored water, which, according to all my experiments, would not 
contain any of the microbes of epidemic water-borne diseases. 
Rapid filtration alone would then be required to remove the precipi- 
tate of inert carbonate of lime." According to the data given, 
the initial average hardness of 15° Clark is reduced in the final 
mixture to about 5-3°, but, of course, the sulphates are left, .so 
that there would appear to be no danger of the water being rendered 
lead solvent, like soft waters generally, though this point is not 
mentioned. But " the disadvantages of the excess lime method 
grafted on to an existing purification are many and serious," 
mainly because " the mere cost of lime would probably be about 
double that of the present sand filtration." The expense, however, 

1 Zdtsch. Hyg., 1887, 15. - Ibid., 1889, 507. ^ Arch. /!//<,.. ISSC, ISO. 

* Vkrteljahr. Off. Mvd., 1898, 16, Sup., p. 138. 

•'• Seventh Research Report to the Metropolitan Water Board. 

^ 2,500 in 7,500 — that is, one-third of its value. 



THE .STERILIZATION OF WATER 70 

has been much lower in practice, and if it secures public safety, it 
is to be demanded. 

Dr. Houston's experimental colicide success with 1 part of 
quicklime added to 5,000 parts of water amounts to 20 parts per 
100,000, or 14 grains per gallon, equal to 1-2 ton of this quicklime 
per million gallons. The proportion of free lime neutralized and 
rendered inert by the carbonic acid of the water would vary from 
time to time, and the quantity required to give the effective bac- 
tericidal excess would have to be regularly tested, also the volume 
of stored water required to neutralize the excess lime. He found 
also that in crude London sewage (Barking outfall) the B. coli were 
killed by a dose of 1 part of quicklime (about 75 per cent. CaO) 
in 2,000 parts of sewage. 

The Halogens. 

Chlorine, bromine, and iodine are amongst the most powerful of 
the germicides. Their action on the organic matter in the water 
is complex, partial oxidation and chlorination taking place simul- 
taneously; loose additive or adsorption compounds are also formed, 
especially in the case of iodine. The -NH^ group present in 
protein-containing substances is especially reactive with chlorine, 
forming unstable chloramines, -NHCl, which in general possess 
germicidal powers frequently exceeding that of chlorine itself. 

In consequence of the combined action they (1) deodorize the 
gases of putrefaction — sulphuretted hydrogen, phosphoretted 
hydrogen, ammonia, and compound ammonias; (2) lessen, by 
bleaching, the colour of water; (3) decompose ptomaines and other 
organic matters; (4) form antiseptic substances inimical to bacteria, 
but in small quantities innocuous to higher life; (5) precipitate the 
albuminoids, therefore attack the bodies of organisms themselves. 
In many of these actions light is necessary, and heat is also favour- 
able. As with nearly all chemical sterilizers, unless the water first 
undergoes a partial purification, the great j)art of the reagent is 
wasted in attacking comparatively inert matters. Kronig and 
Paul in 1897 found that the disinfecting power of the series CI. 
Br, I, decreased in the ratio of increasing atomic weights, 35-4, 80, 
127, but that it varied with the kind of organism and the conditions. 

Of the halogens actually employed for water sterilizations, 
chlorine is the only one used on an extensive scale. Bromine ami 
iodine are only employed in emergencies or for special purposes, 
their cost being prohibitive for industrial operations. 

Chlorine sterilization of public water supplies is now common 
practice, and this germicide is a])))lied to the water in three forms: 
as bleaching powder, sodium hypochlorite, and as clilorine gas. 



80 DISINFECTION AND STERILIZATION 

Bleaching powder, or chloride of lime, a\ hen freshly prepared, 

approximates in composition to the formula Ca<^pi , containing 

some 33 per cent, of available chlorine — i.e., chlorine that is active 
in oxidation and in germicidal capacity. On storage, especially in 
hot, damp climates, it deteriorates rapidly; market samj^les are 
sometimes as low as 20 per cent, available chlorine. 

Sterilization of the water to be treated is usually accomplished 
by the addition of the bleaching powder dissolved in a minor 
volume of water through some suitable proportionating device 
such as a V notch with float attachment or Venturi type injector, 
or by means of a small pump with variable lift geared to the main 
water pump. 

The necessary quantity to be added to effect sterilization is 
governed by a variety of factors, discussed in detail in the litera- 
ture devoted to water purification. Polluted waters naturally 
require a larger chlorine consumption than relatively pure waters, 
since the consumption of chlorine by the non-living organic matter 
in the water is by no means a negligible factor. Waters having 
a chlorine consumption of more than 4 or 5 parts jjer million 
of chlorine or 12 to 15 parts of bleaching powder may usually be 
considered as sufficiently polluted to warrant some purification 
process prior to sterilization. A second factor of importance is 
the nature of the organic matter present in the water. It would 
appear from some experiments conducted by one of the authors 
on the Somme River water during the war that by the interaction 
of chlorine with organic matter of animal origin, although a high 
" chlorine consumed figure " may be obtained, yet sterilization is 
easily effected, whilst the same dosage of chlorine for a water having 
an identical " chlorine consumed figure " is far less efficacious in 
sterilization when the organic matter is of purely vegetable origin. 
This is doubtless associated with the formation of germicidal 
chloramines with the protein matter or their hydrolysis products 
in the former case. The importance of the time of contact as a 
factor cannot be over-emphasized. As an example, the following 
figures of Phelps, quoted by Barton, ^ are instructive : 



Available Chlorine added \ Bacteria per Cubic Centimetre after Time of 
in Parts per Million. Contact in Hours. 


; 


0-5 


1 

270 
2,100 


2 


3 1 1,000,000 
2 1,000,000 


500 
4,600 


230 
3,400 



^ La Chlnrafinn. Paris. 191 S. 



THE STERILIZATION OE WATER 81 

It will be notict^d in this case that M'ith the smaller concentra- 
tion of chlorine there is a distmct aftergrowth, whilst with the 
higher concentration the germicidal activity is not lost even after 
two hours of contact; in neither case is sterilization effected. It 
is therefore necessary, if small quantities of chlorine are employed, 
to ensure an adequate time of contact, as long as can be conveniently 
arranged. An alternative and frequently employed method is to 
add a relatively large excess of chlorine with a relatively short 
time of contact, such as twenty minutes to half an hour, and sub- 
sequently resume the excess of the reagent by some suitable dechlor, 
such as sodium bisulphite, ferrous chloride, or gaseous sulphur 
dioxide. The dosage for natural waters maj^, as has already been 
indicated, vary within wide limits according to the conditions of 
operation; thus, at Niagara Falls 06 part per million of avail- 
able chlorine has been found efficacious, 0-5 part per million being, 
however, by no means infrequent in America. 

Other hypochlorites, such as magnesium hypochlorite, " Her- 
mite Eluid," sodium hypochlorite as " chloros," containing 10 per 
cent, of available chlorine, or Eau de Labarraque, containing 2-5 per 
cent, of available chlorine, and more rarely the original Eau de 
Javel potassium hypochlorite, have been employed for water steril- 
ization. Electrolytic hypochlorite prepared by the electrolysis of 
brine solution has found a small application for the treatment of 
w^ater. In general, however, these substances are usually emj)loyed 
for special purposes, such as sanitary or medical work (see Chapter 
VI.) rather than for routine water sterilization. 

The mechanism of the action of these hypochlorites in water 
purification is by no means clear. 

We have already alluded to the interaction of hypochlorites 
AV'ith amino compounds to produce chloramines of marked germicidal 
activity. 

Albuminous substances are, however, rapidly coagulated by 
chlorine, and nia,y be precipitated from solutions. 

In addition, it has been noted that the germicidal activity of 
hyiJOchlorites in a water contaming dissolved carbon dioxide is 
greater than m an alkaline water of similar nature; lil^ewise the 
germicidal action of a definite hypochlorite concentration is lowered 
on exposure to bright sunlight. It appears reasonable to suppose 
that hypochlorous acid (K„ = 3-7 x 10'^) is the active germicide, 
rather than its salts. The acid is some ten tunes weaker than 
carbonic acid (Ki7 = 3-0 x ID"''), and would thus be liberated from 
its salts in a carbon dioxide containing water. Hy})ochlorous 
acid possesses a different absorption spectrum to that of its salts, 
is more unstable, readily decomposing with the liberation. of oxygen, 



82 DISINFECTION AND STERILIZATION 

and presumably has a different chemical structure, with ^\'hich is 
probably associated a higher germicidal activity. 

Hypochlorite treatment is frequentl}^ employed in conjunction 
with other chemicals, usually precipitants, such as ferric chloride 
in Duyk's ferrochlor process,^ or with aluminium sulphate as at 
Cheltenham in England, and with the IMerrimac A\ater in the United 
States. A few experiments have likewise been conducted with 
hypochlorite permanganate mixtures; the manganese hydroxide 
formed by reduction is, however, not so readily removed from the 
water as ferric hydroxide, and far less easily than alumina. 

For medical work (see p. 201) Dakin's and similar solutions, con- 
sisting of a solution of sodium hypochlorite with a suitable buffer 
salt, are now extensively employed. 

The Chloramines. — Chloramine, NH.2CI, jDrepared by the inter- 
action of sodium hypochlorite and ammonia in the presence of some 
colloidal material such as glue,^ was found by one of the authors^ 
to possess a high germicidal coefficient (see p. 195), and is apparently 
produced in small quantities in waters Avhen submitted to chlorina- 
tion. The idea of preparing chloramine from bleaching powder and 
ammonia without the addition of a colloid has been developed by 
Race in Canada for the purification of water on a large scale with 
a considerable amount of success. Chloramine is not formed by the 
direct interaction of ammonia, water, and chlorine gas. 

Chloramine solutions are relatively unstable, and a search for 
more stable substituted chloramines which should possess the 
necessary stabiUty for purposes of transport, but at the same time 
retain their high germicidal powers, led Dakin to investigate the 
simpler chloramines of the type — ■ 

CI— N-H 




prepared by Chattaway, Blanksma, Orton, Jones, Revett, and 
others.* 

Chlorine. — The use of chlorine gas as a sterilizing agent has now 
assumed large proportions, and may be said to be the standard 
method of water treatment. Although the method was developing 

1 Bull. Soc. Belg. de Geol. d d'll jdrul., 1909, 22, 98. 

2 Soe Raschig, Gliem. Zeit., 1U07, 31, 92(). 

3 J. Roy. San. Inst., 1920, 31, 2. 

* Proc. K. Akad. Weten.sch., Aiustcrdam, 1902, 51, 178; Proc. Hoy. Soc, 1902, 
71, 150; Chcin. Soc. Trans., 1909, 95, 145G; Zeitsch. Physikal. Chem., 1913, 82, 201. 



THE STERILIZATION OF WATER 83 

rapidly before the war, a renewed impetus has been given by the 
ready accessibility of liquid chlorine of a high degree of purity in 
steel cylinders manufactured for poison-gas purposes. In addition, 
chlorine, being a by-product of the ever-increasing electrolytic 
alkali industry, may be purchased at very low cost, manufacturers 
being generally in difficulty as to its disposal. Chlorine cylinders 
are readily transported by rail or water, and the pressures at normal 
temperatm-es, 54 pounds per square inch at 32° F. to 216 pounds at 
122° F., are not too high to cause difficulties in operation. 

In 1903 NesfiekP suggested liquid chlorine stored in lead-lined 
iron cylinders for water sterilization, and this was later on de- 
veloped by C. R. Darnell of the U.S. Army,^ and a modified plant 
on these lines was used by the Allies in the war. The water to be 
treated is raised from a sump and pixmped along a mam. Geared 
with the centrifuge pump is a small accessory pump, which serves 
to maintain a suitable pressure in a small water reservoir, the 
pressure being proportional to the speed of rotation, and conse- 
quentty to the delivery of Avater in the main. The fluid pressure 
in this reservoir actuates a valve mechanism controllmg the chlorine 
delivery from a cylinder through a supply pipe direct to the water 
in the main. The official tests carried out in the United States 
with this simple apparatus were highly satisfactory. In 1914 
Leavitt and Jackson^ developed a different type of dosing apparatus, 
in which the chlorine cylinder was set on the yard-arm of a balance. 
A sliding weight actuated by a suitable mechanism to adjust its 
velocity of travel along the yard-arm according to the water flow 
maintained the balance in equipoise ; any deviation from the mean 
position caused a corresponding increase or decrease in the aper- 
ture of the release valve of the chlorine cylinders. 

The Electro -Bleaching Gas Company's apparatus, which had at 
one time no inconsiderable industrial application, was non-auto- 
matic in character, and made use of the principle of dosage by means 
of a minor volume of water. The apparatus consisted of two 
specially designed reducing valves, the first to reduce a variable 
gas pressure down to a constant value of ca. 15 pounds per square 
inch, and the second a fine adjustment regulating valve admitting 
the chlorine through an ingeniously designed type of Venturi flow 
meter into the base of a vulcanite absorption tower. As contact 
substance coke or similar material could be employed, and absorp- 
tion by means of water was effected on the counter-current principle 

The Wallace and Tieman Companj' of Ne^v York, in which the 
preceding company is now incorporated, have developed numerous 

1 PtMic Health, July, 1903. ^ u.S. patent, 10,007,047 of 1012. 

" U.S. patuut, 1,087,008 and 1,088,232 of 1014. 



84 DISINFECTION AND STERILIZATION 

ingenious dosing apparatus, based l)()tli upon the minor volume 
of water principle and on du*ect application. In the smallest type 
of apparatus th(.» rate of chlorine tiow is measured by the number of 
chlorine gas bubbles issuing per minute from a standard orifice into 
a small volume of water, which then flows into the main delivery. 
Eor slightly larger types an ingeniously constructed pulsing type of 
meter is utilized to measure the rate of supply into the minor 
volume of water. For large apparatus a Venturi type of flow 
meter is employed, and the gas is admitted direct into the watef 
main or conduit through a silver tube terminating in an alundum 
diffuser. 

In England the Paterson Engineering Company have installed 
several chlorine dosing apparatus, utilizing the principle of the 
minor volume of water as a vehicle for conveying the chlorine gas 
into the water system, whilst the flow rate of the chlorine gas is 
measured by means of a siphon meter, either direct reading or 
integrating in its action. 

Chlorine Peroxide. — CIO2 is one of the most energetic of steri- 
lizers, and was first used for waters by Berge.^ It is prepared 
by the action of sulphuric acid on potassium chlorate, the resulting 
gas being passed into water : 

3KCIO3 + 2H2SO4 = KCIO4 + 2KHSO4 + 2C10., + H.O. 

This is easily and safely effected bj' an apparatus described by 
M. Howatson.- 

Although the solution is very fatal to bacteria, it is far milder 
in odour than chlorine or hypochlorous acid, and seems innocuous 
to animals. 

For the same reasons as with previous chemical reagents, to 
work economically it is necessary to subject the Avater to a pre- 
liminary treatment, which in the Howatson-Berge process, as 
operated at Brussels and Ostend, consisted of softening and 
mechanical filtration. At the latter place the potassium chlorate 
used in the preparation is 2 grammes per cubic metre of water, 
which would give theoretically 0-74 gramme of CIO.,, or 0-74 part 
per 100,000. Van Ermengem, in 1898, found that the canal- 
water, with 890 to 23,000 organisms per c.c, after the treatment 
in fourteen cases was sterile, and in five contained one or two 
colonies of the resistant and harmless B. subtilis or B. ramosus. At 
Lectoure, in Southern France, the town supply, drawn from the 
River Cers, and seriously polluted with sewage, has been for many 
years purified by this process. Dr. Ogier reported that the river- 

^ An account of his experiments is given in Ann. Trav. Publ. Bdg., 1898, 36U. 
- Also sec English jjatent 4,917 of 1898. 



THE STERILIZATION OF WATER 85 

water contains 21,000 organisms per e.c. before and only 7 or 8 
after the treatment with peroxide. In our own experiments it 
was found that 2 parts of chlorine peroxide per 100,000 did not 
kill B. typhosus in a vigorous pure culture in two hours, but 
that 5 i^arts killed it in half an hour. These results are comparable 
with Dr. Ogier's, but obtained under somewhat different conditions. 
The slight excess of ClOg rapidly disappears from the water. 

Bromine has been frequently proposed for sterilizing water, the 
objections being the dangerous properties of liquid bromine, and 
the taste and physiological action of the bromide produced. In 
1897 several practical suggestions were made. Altmann patented 
a solution of bromine in potassium bromide, using 4 parts Br per 
100,000 of water acting for five minutes, and removing the excess 
by ammonia. The solution has the inconvenience of bromine, and 
is more bulky; the use of a jDotassium salt has also disadvantages. 

Schumberg, of the German Army, recommended free bromine, 
6 parts per 100,000, for sterilizing water in expeditions, on ship- 
board, and in cases of suspicion, stating that sterility was obtained 
in five minutes. He removed the excess by a tablet of sodium 
sulphite and mannite, the latter probably to conceal the taste: 
later sodium thiosulphate and bicarbonate were employed. The 
method was tried in the Sudan campaign of 1898, but the diffi- 
culties of transport of liquid bromine in glass bulbs militated 
against its use. In the same year Braithwaite proposed to avoid 
this by adopting a solid mixture of a bromide and bromate, followed 
by acid sulphate of soda, to liberate the bromine, but the method 
does not seem to have been tried on a large scale. The quantity 
he reconnnended was sufficient to give 1 grain of bromine per 
quart, or 5-7 parts per 100,000, practically the same as Schumberg 
used. In our omii experiments we have found that 2 parts of 
Br per 100.000 kills 5. typhosus in less than half an hour. Schiider^ 
has come to the conclusion that Schumberg's process fails almost 
completely in the quantities suggested by him, and therefore agrees 
with the opinion expressed by L. Parkes and S. Rideal in a paper 
at the Epidemiological Society in January. 1901.- The fact, more- 
over, that there must necessarily remain in the water a residue of 
bromides, which are known to have a marked physiological effect, 
cannot be considered either natural or safe, and should preclude the 
recommendation of bromine for sterilization of water for drinking. 
A similar remark applies to iodine (which was used for the same 
purpose by AUain at Marseilles), to iodine trichloride and cuprous 
chloride, and to many other compounds that have at various times 

1 Zeitsch. 1/i/g., 37, 30fi. 

^ See also a paper by Dr. H. Frazer, Pub. Health, September, 1902, 721. 



86 



DISINFECTION AND STERILIZATION 



been proposed. Our own experiments with iodine trichloride 
showed that with 2 parts per 100,000 B. tijpliosus was ahve after 
twenty hours, but that 5 parts killed it in half an hour. 

Fluorine Compounds. — The soluble ones are strongly antago- 
nistic to moulds, and in a less degree to bacteria. The former 
character has led to their being added to brewery waters. Sodium 
silico- fluoride (isotachyol) has been found to be a powerful germi- 
cide, while Dr. Frank recommends the silico-fiuoride of aluminium.^ 
They are stated to have no injurious action on health. - 

Sterilization by Acids. 

Kitasato's results with B. typhosus in nutrient media have been 
summarized by Horrocks in the following table: 





Per Cent, of Reagent. 






Growth 


No 




Growth. 


Restrained. 


Growth. 


Acids — 








Sulphuric acid 


0-040 


0-065 


0-08 


Hydrochloric acid . . 


0-1 


0-1.58 


0-2 


Nitric acid . . 


0-1 


0-157 


0-2 


Sulphurous acid 


0-09 


0-2 


0-28 


Phosphoric acid 


0-15 


0-224 


0-3 


Acetic acid . . 


0-2 


0-255 


0-3 


Carbolic acid 


0-2 


0-258 


0-3 


Formic acid . . 


0-22 


0-278 


0-34 


Oxalic acid . . 


0-23 


0-285 


0-366 


Lactic acid . . 


0-27 


0-36 


0-4 


Tartaric acid ] 
Citric acid V 
Malic acid j 








0-338 


0-384 


0-476 








Tannic acid . . 


1-3 


— 


1-66 


Boric acid 


1-5 


2-0 


2-7 


Alkalies — 








Caustic lime . . 


0-0725 


0-0805 


0-0966 


Caustic potash) 
Caustic soda / 


0-1 


0-14 


0-18 


Ammonia 


0-148 


0-2 


0-3 


Lithium carbonate . . 


0-514 


0-6 


0-666 


Potassium carbonate 


0-560 


0-74 


0-81 


Barium hydrate 


0-65 


0-83 


1-00 


Ammonium carbonate 


0-72 


0-845 


1-00 


Sodium carbonate . . 


2-00 


2-2 


2-47 


Salts- 








Potassium iodide 


(riWt 


8-0 


9-23 


Potassium bromide. . 


S-O 


9-23 


10-37 


Potassium chloride . . 


!M 


10-6 


10-2 



In these experiments broth and gelatine media were carefully neutralized 
before adding the substances, then inoculated with B. typhosus and kept at room 
temperature, subcultures being taken at 4 or 5 and at 10 to 15 hours. 



Wasser n. Abwasser. December, 1910. 
Peiret, Public Health, October, 1908. 



THE STERILIZATION OF WATER 



87 



Very different results are obtained, however, when water free 
from organic matter is employed instead of nutrient media. Thus, 
0-096 per cent, of caustic lime to kill typhoid in strong broth is 
reduced to 0-0074 per cent., or less than one-tenth, when the broth 
is diluted with fifteen times its volume of distilled water. Similarly, 
in bouillon containing less than 1 per cent, of peptone, cholera 
vibrios are killed by 0^01 per cent, hydrochloric acid in half an hour, 
but require four times this quantity in the presence of 2 per cent, 
of peptone. It would therefore appear that chemical reagents, 
whether thej^ possess oxidizing properties or not. are more efficient 
as sterilizers when the water to be treated is comparatively free 
from organic matter. 

Our own results with some of these substances in impure water, 
inoculated with varying amounts of typhoid and kept at room 
temperature, are : 



Reagent. 


Per 

Cent. 


Time {Hours). 


Results. 


Sulphuric acid 

>> >> 
Sulphurous acid 
Caustic soda . . 


•025 

•030 

•035 
•030 
•050 


20 
[{a) k 
\ (b) 1 
i (c) 20 

20 


Killed 

Alive 

Alive 

Killed 

Killed 

Killed (alive at 1 hour) 

Alive 



The organic acids, like tartaric, citric, and acetic, also possess 
this property; and in 1893 the use of tartaric acid for purifying 
water, in conjunction with a filter, was patented, and its use has 
been suggested in Italy for sterilizing salads before consumption. 
Dr. Christmas, in 1892, showed that citric acid, although fatal to 
the cholera bacUlus when used in the proportion of 8 j)arts in 10,000, 
did not destroy the bacillus of t;y'phoid in a less strength than 1 in 
1,000. It may be that lemon juice and vmegar, as dietetic adjuncts 
in salads and uncooked shell-fish, have further been extremely useful 
in minimizing the dangers of typhoid derived from such sources. 



Metallic Salts. 
Several metallic salts have been used in emergencies, but their 
cost generally' makes continued use prohibitive. Silver salts in 
solution are bactericidal. Waters containing chlorides precipitate 
them as silver chloride, a part of A\'hich remains sus]iended and 
retains activity. In our laboratory B. coli Avas killed in twenty-four 
hours by a 0^1 per cent, solution, but the same strength failed to 



88 DISINFECTION AND STERILIZATION 

kill S. pyg. aureus in the presence of only a small quantity of eliloi'ide 
and organic matter. 

Paterno and Cingolani found 1 in 400,000 of silver fluoride 
(tachj'ol) fatal to non-sporing bacteria in half an hour. Hetsch, 
with 1 in 500,000 of silver fluoride, destroyed cholera germs, but 
not those of dysentery or typhoid; with I in 200,000 he killed 
cholera in ten minutes, tjqDhoid and dysentery in twenty minutes. 
Traetta Mosca extended this work, and found silver sulphate, 
chlorate, and perchlorate all "strong and effective for sterilizing 
water." Copper has long been known to possess bactericidal, and 
especially algicidal, powers. In 1893 Khronke^ showed that 1 in 
20,000 of cuprous chloride, together with some ferrous sulphate, 
sterilized water in six hours, after which time 1 part of lime in 
100,000 was added to precipitate the copper oxide. This was 
removed by sedimentation followed by sand filtration. 

In 1904 one of us suggested the use of copper vessels for the 
automatic sterilization of water by simple contact. Kraemer,^ 
in 1906, found that the period of contact required by copper with 
the surrounding water to produce sterility was from two to four 
hours. 

Metallic and colloidal copper kill coli and tj^^hoid in water 
after four hours. Kraemer recommended 3i square inches of 
copper strips innnersed in each quart of water five to eight hours 
for household purification. 

In 1904 and 1905 Moore and Kellerman at Washington showed 
that copper sulphate was, in the strength of 1 in 10,000, a good 
algicide and a fair bactericide, sterilit}' being obtained after three 
hours. 

Clark and Gage^ found copper sulphate rather uncertain in its 
action, sometimes as much as 8 in 1,000 being required to ensure 
sterility. The general conclusion is that copper sulphate in the 
strengths 1 in 100,000 to 1 in 50,000 is an efficient algicide, but 
only of doubtful value as a germicide. 

The methods just outlined have been ajoplied in special cases 
to the treatment of swimmmg-bath Avater, fish-ponds, polluted sea- 
water in oyster-beds, and to sewages. It is well known that oysters 
are a common vehicle of typhoid, "• and it is now customar}- to effect 
the cleansing of oysters with sterile sea-water. Not much progress 
is to be recorded in the treatment of sewage with germicides, 
although several minor plants are in operation utilizing chlorine 

1 J. Gasbeleucht, 36, 513; also Rideal's " Water Supplies," 1914, 178. 
■f^ Kramer, Amer. J. Pharm., 78, 140. 
-f* 3 Clark and Gage, J. Infect. Dis., 1906, Supp. 2, 75. 

* S83 graphical rapresentation by P. Vincey, Bull. Soc. d'Encour., 191.'}, 277. 



THE STERILIZATION OF WATER 89 

(0 to 10 parts per million) or sul2:)hur dioxide gas as sterilizing agent. 
It is found, however, that the general methods of bacterial hydro - 
l3^sis, or the activated sludge sj^stem follo^wed by adequate aeration 
and dilution of the effluent, is the most economical system of dis- 
posal, and that partial or complete sterilization is only to be em- 
ployed when circumstances indicate clearly the essential need of 
some such operation. 



BIBLIOGRAPHY. 

DzKRZGOWSKi, M. W., DzERZGOwsKi, S., and Dmitrevsky, Mlle. N.: Sur la 

sterilization de I'ean potable par les rayons ultraviolets, Arch. soc. hioL, 

1914-15, 417-439. 
Johnson, C. A.: Shell-Fish Conservation and Sewage Disposal, Amer. J. Pub. 

Health, 1914. 4, 965-968. 
- Garret, J. H.: The Effect of Copper Sulphate upon Certain Water Weeds, Pub. 

Health, 1914-15, 28, 65-67. 
Ledener, a.: The Biochemical Oxj^gen Demand of Sewages, J. Ind. Eng. C'hem., 

1914, 6, 882-888. 
Pryer, R. W.: Water Purification by Ozone, with Report of the Ann. Arbor Plant, 

.7. Ind. Eng. Chem., 1914, 6, 797-800. 
Von Recklinghausen, M. : The Ultra-Violet Rays and their Application to Sterili- 
zation of Water, J. Frankl. Inst., 1914, 178, 681-704. 
Sperry, W. a.: Water-Softening and 'Decolorization. Amer. J. Pub. Health, 

1914, 4, 1079-1082. 
Von Recklinghausen, M. : Purification of Water by the Ultra-Violet Rays: 

Principles underlying the ]\Iost Recent System for Destroying Germ Life, 

Scient. Amer. SuppL, 1915. 79, 10-12. 
Wedekind, L. L. : The General Use of Distilled Water, thereby Securing the 

Elimination of Toxins leading to Arterial Changes and the Elimination of 

Water-Borne Diseases, 3Icd. Rev., 1915, 87, 59-61. 
BiNDi, N. : Contributo alio studio della purificazione biologica delle acque coi 

raggi ultra-violetti, Riv. d'ig. e. san. publ., 1915, 26. 4-18. 
Hering, R.: Latest Advances in Inoffensive Sewage Disposal, Science, 1915, 41, 

766. 
Lederer, a.: Notes on the Practical Application of the " Saltpetre Method " for 

Determining the Strength of Sewages, Amer. J. Pub. Ilculth, 1915, 5, 354-361. 
Nelson, J. J. H.: Sterilization of Water by Chlorine. Brit. Med.'.J., 1915, i., 789- 

793. 
NESFiBfeD, V. B. : The Rapid Chemical Sterilization of Water, J. Roy. Ann;/ Med. 

Corps, 1915, 24, 146-154. 
L'action des eaux potables sur les canalizations en plonib et les dangers qui resul- 
tant. Bull, office internat. d'hyg. pub., 1915, 7, 641-645. 
McLaughlin, A. J. : The International Joint Commission's Investigation of Sewage 

Pollution of Boundary Waters, Amer. J. Pub. Health, 5, 555-559. 
Chamot, E. M., and Reafield, H. W. : Studies on the Culture Media employed 

for the Bacteriological Dunham Medium for testing the Presence of HA'drogen 

Sulphide forming Bacteria, J. Atner. Chem. Soc, 1915, 37, 160()-1636. 
M.\.soN, W. P.: Contributions of the Chemist to Potable Water Industry. ,7. Ind. 

Eng. Chem., 1915, 7, 289. 



90 DISINFECTION AND STERILIZATION 

Von Recklinghausen, M.: Ultra-Violct Rays for Water Purification, ./. N. Eng. 

Watenvorks Assoc, 1915, 29, 202-213. 
~f" Thomas, S. J.: The Use of Copper Sulphate in tlie Purification of Swimming Pools, 

J. Ind. Eng. Chem., 1915. 7, 496-499. 
DiTTOE, W. H.: The Disinfection of Water, Ohio Med. J., 1915-10, 6, 1,33-142. 
Wakeford, J. P.: Brief Notes of Experiments in Sewage Purification by Forced 

Aeration, Proc. Incorp. Assoc. Mttnlcip. and Co. Engin., 1915-16, 42, 116-128. 
Colin, H. : Sterilization de I'eau par I'acide comonique sous pression, Compt. rend., 

1915, 161, 652-655. 

Chase, E. S.: Emergency Chlorine Sterilization Plant for Public Water Supjilies, 

Month. Bull. N.Y. State Dep. Health, 1916, 3, 203-208. 
DiENERT, F.: Influence des sluges des filtres a sable submerge dans I'epuration 

des eaux, Compt. rend., 1919, 168, 127-130. 
Zausoiloff, M. a.: Sterilization of Potable Water by Tincture of Iodine, Vestnirk 

Ohshtsh. Hig. Sadeb. i Prakt. Med., 1916, 52, pt. 2, 724-728. 
Houston, A. C: The Harben Lectures, Lecture II., River Thames, ,/. State Med. 

1916, 24, 357-379. 

Bertarelli, E.: Ipochlorite permanganati perossidi nella sterilizzazione delle 

acque, Riv. d'ing. san., 1916, 12, 68-70. 
Race, J.: The Use of Ammonia in the Chlorination of Water, Lancet, 1916, ii., 71. 
Bante, G.: La sterilizazzione dell' acqua con la tintura di iodio, Med. nvova Roma. 

1916, 7, 109; also Riv. ospedal Roma, 1916, 6, 239-242. 

Tatham, G. T. p. : Some Theoretical Considerations bearing on the Performance 

of Biological Sewage Purification Plant, J. Soc. Chem. Ind., 1916, 35, 711- 

715. 
Clark, H. W. : Development at Lawrence of the Process of Purifying Sewage by 

Aeration and Growths: Activated Sludge, Science, 1916. 44, 322. 
Clark, H. W. : Development of the Purification of Sewage by Aeration and Growtlis 

at Lawrence, Massachusetts, J. Ind. Eng. Chem., 1916, 8, 653. 
Powell. S. T.: The Design and Operation of Ozone Water Purification Systems, 

J. Ind. Eng. Chem... 1916, 8, 632-636. 
Golse, J.: Controle de I'epuration des eaux par javellization api-es elimination du 

chlore actif par I'hyposulfite de soudre, J. pharm. chim., 1916. [vii.], 14, 8-13. 
Lead in Potable Water: What Amount renders the Water Unsafe for Domestic 

Purposes, Med. Oflicer, 1917, 17, 153. 
Report of Committee on Sewerage and Sewage Di.sposal of the Sanitary Engineer- 
ing Section, Amer. Pub. Health Assoc. Med. Insur. and Health Conserv., 1917- 

18, 58-62. 
Nesfield, v.: The Sterilization of Water by Chlorine and Hypochlorites, Ind. 

Med. Gazz., 1917, 52, 351-358. 
Dienert: Nouveaux perfectionnements dans la javellization des eaux. Bull, de 

Voffice internaf. d'hyg. pub., 1917, 9, 1245-1258. 
Galaine, C, and Houlberti C: Sur un nouveau dispositif de filtration rapide 

des eaux alimentaires apres leur epuration par le procede Lambert Laurent, 

Compt. rend., 1917. 164, 121-124. 
Golse: Controle de I'epuration des eaux par javellization apres elimination du 

chlore actif par I'hyposulfite de soudre, Ann. d'hyg., 1917. [iv.], 28, 102-104. 
Massy: Sur la determination de la quantite d'extrait de javel a employer pour 

epurer une eau, J. pharm. chim., 1917, [vii.], 16, 209-213. 
Peck, E. C: Nitrogen, Chlorine, and Sulphates in Rain and Snow, Chem.. Xeics, 

1917, 116, 283. 

RocHAix, A.: Recherche rapide de la contamination bacteriologique des eaux de 
boisson, Rev. d'hyg., 1917, 39, 472-483. 



THE STERILIZATION OF WATER 91 

Norton, J. F. : Analysis of Water in a Swimming Pool: Study of Bacteriological 
Condition of Water in a Y.M.C.A. Pool, where a Return System of Purification 
is Used, 3Ieta.l Worker, etc., 1917, 87, 328. 

LocHRiDGE, E. E. : The Application of Coagulant Intermittently in Excess Amounts 
at Si^ringfield, Mass., J. N. England Wafenvorks Assoc, 1917, 31, 48-53. 

Houston, A. C. : The Harben Lectures, 1916, III. River Thames, J. State Med., 

1917, 25, 3-28. 

Dakin, H. D., and Dunham, E. K.: The Disinfection of Drinking Water, with a 

Description of a New Substance for the Preparation of Stable Tablets for the 

Sterilization of Polluted Water, Brit. Med. J., 1917, i., 682-685. 
Dakin, H. D., and Dunham, E. K.: The Disinfection of Drinking Water, Amer. 

J. Med. Sc, 1917. 154, 181-188. 
Rendering Drinking Water Potable, 3Icd. Rev., 1917, 92, 198. 
Adams, F. : Halazone for Water Sterilization (Report to the Medical Research 

Committee). Brit. Med. J.. 1917. ii.. 184. 
Report of Committee on Sewage Oi>eration and Analytical Methods to the Sanitary 

Engineering Section of the American Public Health Association, Amer. J. Pub. 

Health, 1917, 8, 680-689. 
Embrey, G. : Some Experiences in the Use of Copper Sulphate in the Destruction 

of Algae, Analy.st, 1917. 42, 264-271. 
Heise, G. W. : The Interaction of Chloride of Lime with the Normal Constituents 

of Natural Waters and Sewage, Philippine J. Sc., 1917, A, 17-34. 
Steen, G. J. A. : General Discussion of Sewage Purification, with Special Reference 

to the Applicability of Biologic Purification in Our Country, Water, Bodem, 

Lucht, 1917, 7, 114-123. 
Mills, R. G., Ludlow, A. J., and Van Buskirk, J. D. : A Simple Method of Water 

Purification for Itinerant Missionaries and Other Travellers, China Med. ./., 

1918, 32, 137-145. 

Turner, C. E.: Plant and Animal Life in the Purification of a Polluted Stream, 

Scient. Month., 1918, 7, 34-45. 
Manheimer, W. a.: The Application of Ozone to the Purification of Swimming 

Pools, Pub. Health Pep.. Washington. 1918, 33, 267-273. 
Fralick, W. G. : Sterilization and Purification of Water with Isotonic Sodium 

Hypochlorite Solution, with the Neutralization of tlie Water by Peroxide of 

Hydrogen, Med. Rev., 1918, 93, 239. 
DiENERT, F., and Guillerd, A.: Concentration des germes de I'eau, Conipt. rend., 

1918, 166, 307. 
NoYES, H. A.: Sterilizing Measured Amounts of Water in Autoclave. J. Bac'eriol., 

November. 1918, 3, 537. 
Housten: Bacteriological Qualities of Roof -Collected Samples of Rain Water, 

Brit. Med. J , 1919, i., 766. 
LoEB, J.: Electrification of Water and Osmotic Pressure, ./. Gen. Physiol., 1919. 2, 

87. 
Casselman. E. J.: Prevention of Stream Pollution by Dye and Intermediate 

Wastes. Pub. Health Rep., 1920, 35, 167. 
Fair, G. M. : Sanitation of Industrial Water Supplies, J. Indu.^t. Ifi/g.. 1920, 1, 457. 
Emerson, C. A.: Sanitary Disposal of Sewage'and Trade Wastes, and Consideration 

of what Constitutes a Proper and Adequate Drinking Water Supply, Pennsyl- 

vania Med. J., 1920, 23, 186. 



CHAPTER V 
PUBLIC DISINFECTION 

The Disinfection of Rooms and Pablie Vehicles.— It has alreadj^ 
been indicated tliat methods involving sterilization of the air ol 
rooms are usually designed to carry the disinfectant to the walls, 
ceilings, and floors, on which most of the micro-organisms are found 
dej)osited; consequently more rapid and efficacious disinfection in 
rooms is accomplished by means of the disinfectant spray. Form- 
aldehyde solution is frequently used, the strengths adopted being 
from 0-5 to 2-5 per cent. There is great risk of imperfect spraying 
except with a good apparatus in the hands of an experienced 
operator, crevices and parts of the room or furniture being fre- 
quently missed by the spray. When the walls and rooms are 
exceptionally dirty, or when very special disinfection is needed, 
as in plague, both a spray and a vaporous disinfectant should be 
used. 

Fresh air, light, and frequent cleansing are the essentials to be 
aimed at in thickly-populated districts. In washing floors a strong 
carbolic soap, or, better, a cresylic preparation, is very useful. 
Curtains and bedding must be occasionally brushed and shaken in 
the open air. When sweeping floors and carpets, tea-leaves or 
dami^ sawdust should be used to prevent the difi'usion of germs 
in the dust, since micro-organisms remain suspended in the air of 
a room for a relatively short period, jirovided that the air is damp 
and quiet. 

As a substitute, antiseptic absorbents may be used ; one on the 
market, " Floorfix," was found to consist of damp sawdust weighed 
with a little sand and containing moist sugar and formaldehyde 
(about 1| per cent.). Recently the practice of oiling the floors with 
slow-drying oils, with or Avithout the addition of disinfectants, has 
been somewhat extensively adopted with, it is stated, excellent 
results. Oil paints, or well-varnished papers, are preferable for 
walls, as they can be easily washed. A very important point, 
especially in connection with hospitals, is that walls should consist 
of impervious material not aff'ording a lodging-place for the growth 
of disease bacteria. Several exhibits with this object were shown 
at the Building Trades Exhibition, 1903. Flock papers have 

92 



DISINFECTION OF ROOMS 93 

become obsolete, from their forming such a favourable nidus for 
the growth of organisms. Ordinary papers are sometimes cleaned 
M'ith bread-crumb to avoid dust, but the removal of bacteria is 
incomplete. 

Hygienic Wall-Papers prepared with various disinfectants in- 
corporated in the pulp have been suggested. Mercuric chloride 
has even been proposed to be introduced, but Its use should not be 
permitted on account of the danger of its being evolved in the dust. 
Resorcinol, 1 in 2,000, is patented by Sinclair and BroAni for this 
purpose. It has been proposed to incorporate salicylic acid with 
the plaster coating of walls ; it is non-volatile and inodorous, but it 
is very doubtful if it would be efficacious. It always communicates 
a pinkish colour, owing to the presence of iron salts. Kosinsky, of 
Warsaw, invented a portable apparatus for heating air to any 
required temperature, and forcing it at the rate of about 1,000 cubic 
feet a minute through radiating tubes against walls and other 
surfaces for drying and disinfection. It is also intended for large 
dismfecting chambers, in which the rapidity with which the air 
passes combines with the high temperature (stated in the repoit 
to be 660° F., but this is obviously an error) in bringing about the 
desired result. It is also suitable for warming buildings, and for 
removing vapour and moisture from crowded rooms — e.g., in a 
theatre, after the exit of the audience, to prevent the condensation 
and settlement of injurious moisture and dust. An official com- 
mission at Warsaw proved that a private house, the building of 
which was commenced in May, 1882, with the capacity in ground 
floor and first story of 7,000 cubic feet, was completely dried in 
fourteen days, and severe sanitary inspection proved the building 
to be completely sterilized. 

In India, accordmg to the report of the Plague Commission, the 
disinfection of houses that had contained cases has been universally 
carried out. The disease sometimes recurred in the same building, 
in one instance thirty-four do^ya afterwards, but may have been 
due to a fresh infection. Mercuric chloride was generally used, and 
in Poona was pronounced efficient if operated by British soldiers, 
while in Baroda there was frequent recurrence in houses thus dis- 
infected under the supervision of the health officer himself. Mr. 
Hankin showed that the cow-dung A\hich is so large an ingredient 
of the floors of native houses ccmtained much alkali and otiier sub- 
stances whidi ])rccipitat(> the mercury, and that the remedy was 
to be found in strongly acidifying the st)lution. Peroxide of hydrogen 
was also said to have been successful. The digging out and burning 
of the floors was dangerous to the workmen. Unroofing and exposure 
to sun and air was of service in the dry districts of Smd and the 



94 DISINFECTION AND STERILIZATION 

Punjab, but was not always practicable. All operations involving 
disturbance should have been accomj)anied by liberal spraymg. 

Roger^ found 1 in 50 carbolic acid and 1 in 500 mercuric 
chloride (acidulated with hydrochloric acid) the best disinfectants 
for mud floors in India during plague. He found that 1 in 750 phenol 
and 1 in 20,000 HgCL, are effective in destroying plague bacilli in 
test-tubes in fifteen minutes. He preferred the carbolic acid for 
practical work, as it has been seen that the effectiveness of the 
mercuric salt is reduced in much greater proportion than the carbolic 
acid; floor disinfection, of course, does not minimize the danger from 
rats. A memorandum with elaborate instructions as to cleaning and 
disinfecting school buildings was issued by the Scottish Education 
Department in 1907. Among other recommendations, they stated 
that every schoolroom should be cleansed by moist cleaning and 
disinfection at least once a year. Some rooms, particularly infant 
rooms, may require such thorough cleaning several times a year. 
Offices should be sprayed with disinfectants as often as is necessary 
to keep them free from offensive odours. 

In sjo raying walls, it is best to start from a bottom corner of the 
room, working along horizontally, and gradually extending upwards, 
in order that the wetting of walls may proceed evenly and without 
splashing ; this will ensure walls drying without patches or stains. 

Furniture and Woodwork can be \\-ashed and scrubbed, or, in 
special cases, should be washed with 1 in 1,000 mercuric chloride 
(in a few instances this may cause discoloration), or with 1 jDcr cent, 
formaldehyde (2| per cent, formalin), taking care of the hands. 
Upholstered furniture, when infected, requires very careful and 
thorough treatment; it should be avoided in bedrooms. Beeswax 
and turpentine are better than the common furniture polishes, as 
the surface is to some extent disinfected and rendered non-absorbent. 
All cracks and crevices should be carefully filled up with putty to 
prevent the lodgment of vermin or germs. 

Sinks, if made of stoneware, can easily be cleaned. Here Condy's 
fluid (permanganate) is serviceable, but strong soda is ordinarily 
better. For toilet utensils sodium hypochlorite (chlorinated soda) 
in 5 per cent, solution should be occasionally used, also for milk cans 
and pails. In the case of metal baths it should not be used too 
strong, as it removes paint. Bedsteads, in addition to scrubbing 
with soap and water, can be afterwards Avashed with chloride of 
lime and water, 10 per cent., and left in the air till the odour has 
almost (Usap})eared. Parallin oil is sometimes used, but its odour is 
very persistent. Polished floors are to be recommended in pre- 
ference to porous floors and carpets. 

1 J. IJyy., 11IU2, 138. 



DISINFECTION OF ROOMS 95 

Sick-Rooms cannot be disinfected in presence of human beings. 
All placing of saucers with chloride of lime, permanganate, etc., 
under the bed or about the room is simply illusorj^ but the 
practice of hanging up damp sheets certainly assists in the deposi- 
tion of micro-organisms from the air, thus minimizing the chance 
of infection. Similarly, fumigation by medicated lamj^s or candles, 
burning pastilles, or bro^n paper, is useless. Sufficient of the 
disinfectant to kill the micro-organisms of the aii' would make the 
air unfit to breathe. The following precautions, however, will be 
of service: 

1. Isolation. — -If possible, the other inmates of the house should 
live on a different floor. Where this, on account of poverty or 
other cause, is unattainable, contact should be carefully avoided. 

2. Clothing. — The attendants should wear cotton and linen, not 
Avoollen, garments. This is now compulsory- in hospitals and most 
institutions. The greatest personal cleanliness should, of course, be 
observed. The following is a way of removing soiled clothing from 
the room : At the bottom of a large air-tight tin trunk, such as is 
used for travelling to India, is placed a piece of felt or blanket, or 
three or four thicknesses of flannel. This is sprinkled with crystals 
of carbolic acid and covered with a linen cloth. The crystals will 
soon deliquesce and soak into the stuff. The lid should never be 
left oi^en. The soiled clothing is put in. and A\'hen full it is left 
for an hovu- for the phenol vapour to penetrate, and then carried 
out into a yard, where it is filled with boiling water containing soda, 
and washed as soon as possible. The washing must never be done, 
nor the clothes hung out to dry, on the same day as the ordinary 
house washing, nor should they be ironed or starched in the same 
room or with the same utensils. This dry method of removal of 
clothing is probably better than the usual one of plunging into a 
disinfectant solution (jDhenol or mercuric chloride), as it is easier, 
and the weight of the water and constant carriage are avoided. 

3. Excreta, vomit and sputa, according to earlier directions, 
should be received into about a pint of mercuric chloride solution, 
1 per mille, with 10 per mille of common salt and 1 per mille of 
hydrochloric acid coloured with indigo to avoid mistakes, a large 
quantity of such a solution being kept ready (see Ch. VI.). Dr. 
Fischer recommended aniline water for disinfecting tuberculous 
sputa (Ch. VI.). "Five per cent, phenol did the same in twenty-five 
hours; mercuric chloride, 1 in 500, failed. Dry heat of 100° C. 
sometimes fails, though it acted after sixty minutes. Boiling ten 
minutes or steam for fifteen minutes succeeded."' Disinfected 
excreta must not be thrown away before the agent has had time 

1 Mill/icil. Kais. Ut-iandh., 1884. 



96 DISINFECTION AND STERILIZATION 

to penetrate. If disease begins in liouses where the sick person 
cannot be properly accommodated and tended, medical advice 
should be taken as to the propriety of removing the patient to an 
isolation hospital. " Where dangerous conditions of residence 
cannot be property remedied, the inmates, while unattacked by 
disease, should remove to some safer lodging." 

4. Light and air should be freely admitted. Vallin strongly 
recommends the use of water spray in the room, as he saj's that the 
water entangles the bacteria and dust, and the dissolved oxygen 
in the water destroys them. He also approves the use in the water 
of a small quantity of resol (dimethyl-resorcin), a body proposed 
bj' M. Pabst, as agreeable and non-corrosive. A 1 per cent, solution 
of peroxide of hydrogen might also be employed for the same pur- 
pose. The sick person should be protected by a screen from this 
process, from draughts, and from too much light. ^ It is well kno\\Ti 
what benefit is derived in some lung diseases from the common 
bronchitis kettle. Dr. W. Ferguson has suggested its use as a 
fumigator in pneumonia and diphtheria by the following simple 
modification: ''Take an ordinary -bronchitis kettle, remove the 
first joint, and replace it by a common tin funnel loosely filled with 
tow. Pour on the tow 1 drachm of pure phenol, and at intervals 
more. The steam carries off the phenol."- But whatever utility 
these practices may have medicinally, we must again emphasize that 
they cannot be considered as disinfection. Curtains, hangings, 
carpets, and all unnecessary furniture should be removed. 

After-Disinfection. — Phenol, chlorine, and sulphurous acid have 
each had their advocates. 

(a) Phenol. — ^Pouring strong carbolic acid on a hot shovel is 
dangerous to the operator. Calvert manufactures a perforated iron 
cylinder delivering a mixture of 2 parts phenol and 1 part water on 
to a red-hot iron heater; the whole is compact and can be carried 
by a hook. There is also Savory and Moore's vaporizer, in Avhich 
phenol falls on a hot plate, and many others. But phenol vapour 
is not reliable as a disinfectant (Miquel and others^), and the smell 
remains persistent. The following is the substance of directions 
given at various times by the Local Government Board and other 
authorities for disinfection by chlorine or sulphurous acid. These 
agents, however, have now been largely displaced by formaldehyde 
(see p. 16). 

(6) Sulphurous Acid. — -After the removal of such articles as are 
best disinfected by heat, and the closure of windows and crevices, 
the gas in ample quantity should be evolved, the doors being 

1- DisinJeckDils, p. 407. - Lancet. LSSO, ii., 757. 

'■i bJeealao P/uirin. J., [iii.J- 2, 545. 



DISINFECTION OF ROOMS 97 

closed for six hours or more. The amount of gas required for the 
disinfection of a moderately-sized room can be obtained by burning 
1| pounds of roll brimstone in a pipkin over a small fire placed in the 
middle of a room, with an old tray or the like to protect the flooring. 
These processes should be effected by skilled persons acting under 
the directions of the Medical Officer of Health. AU M^all-paper 
should be stripped from the walls and burned, and the same room 
ought to have its ceilings and walls thoroughly washed and lime- 
whited.^ Boake's liquid sulj^hurous acid, bottle or this, are much 
more convenient (see p. 23). 

(c) Chlorine. — Three pounds of good chloride of lime and 
3 pounds commercial hydrochloric acid should be used for every 
1,000 cubic feet. This quantity is divided into several parts and 
placed in deep stoneware vessels as high as possible (since chlorine 
gas is heavier than air), and the acid allowed to drop in gradually 
by a funnel with narroAv tube. The room should then be closed 
for twent3-four hours. The operation j)resents many difficulties 
in practice, requires the removal of metals or the protection of 
fixtures with vaseline, sometimes involves much damage, and the 
subsequent opening of the room is very dangerous even when 
breathing through a towel soaked in ^ to 1 per cent, ammonia 
solution. Finally, it is not always successful, and has been virtually 
abandoned. 

In the above fumigation with chlorine there is an important 
omission. Inasmuch as the dry gas will not disinfect, it is necessary 
to generate steam by a boiler or large kettle over a good fire for some 
time before commencmg, so as to make the whole room and the 
air thoroughly damp but not too wet. 

{d) Non-volatile disinfectants can be applied by mechanical 
means. Thus bleaching powder can be used as a wash, and the 
walls, floor, and ceilmg coated by means of a brush. Mercuric 
chloride solution and formalin, or, in fact, any liquid disinfectant, 
can be spra^'ed into the room. Many forms of sprayers have been 
devised. The importance of a fine division of liquid depends on 
the fact that it enables the work to be done with the minimum 
useful amount of disinfectant, saving the expense and inconvenience 
of waste liquid. The parts containmg the disinfectant can be Ihied 
with ebonite, so that the sprayers may be used with any lic^uid 
disinfectant without any risk. The cost will vary slightly with the 
disinfectant used. Taking pcrchloride of mercmy, 1 in 1.000 solu- 
tion, it is found that an ounce of salt disinfects more than 3,000 
square feet of surface. 

Dr. Leslie Mackenzie pointed out the advantage of sprajang out 

^ Circular of Med. Off. of Ilmllh. Local (lovernment Board. 

7 



98 DISINFECTION AND STERILIZATION 

hospital Avards at intervals, and found that in a scarlet fever ward 
various minor affections disappeared after formalin spray had been 
used while the ward was temporarily emptied for a iew days. The 
" Mackenzie Spray," sold by the Thresh Company, is a pump with 
air-chamber capable of maintaining a steady jet for ten minutes.^ 
The " Invicta " sprayer is a portable tank into which air is driven 
untU a pressure of 15 pounds is recorded on the pressure gauge, then 
the disinfecting liquid is forced in with the same pump until 45 
pounds pressure is reached. The quantity of liquid is about 
H gallons; the spray will last about twenty minutes, and is con- 
trolled by a stopcock. The exit is by a tube with ball valve coming 
from the lower part. It has been improved and adopted by 
Dr. Robertson, M.O.H. for Leith,- and he reports that it is very 
successful. 

The State Board of Maine in 1900 issued a special cu-cular of 
directions for disinfection of rooms, furniture, etc., used by con- 
sumptives, in vieM' of the difficulty of killing 5. tuberculosis. Details 
are given of the employment of steam or boiling for fabrics and of 
formaldehyde gas and spray for rooms and upholstered furniture. 
Fifty c.c. of formalin poured upon a cloth in the lower part of a 
disinfecting chamber of 1,089 cubic inches capacity disinfected books 
that were standing on end in twenty-four hours, but not those lying 
flat. 

Letters. — At some asylums all letters are disinfected with dry 
steam before sending out. Rosenau at Havana treated the mails 
by clipping off a corner of the envelopes and dropping in a little 
formalin from a fine jet, then keeping them overnight in a sack or 
tight box sprinkled with the disinfectant. 

Clothes, bedding, mattresses must be removed at once in a closed 
van to a disinfecting station to be treated with superheated steam. 
Dry hot air is now only used in special cases (books, leather, and 
some other materials), and apparatus solely for this purpose is not 
often made. Occasionally, however, a baker's oven may serve, if 
not for the destruction of the spores of splenic fever, for killing the 
non-sporiferous bacteria of cholera, typhus, and diphtheria, and 
especially for animal vermin (Klein). The bodies of persons who 
have died of infectious diseases should be at once wrapped in a 
cloth soaked in 1 per cent, solution of mercuric chloride prior to 
burial or cremation.^ Adolf and Heider find that hot solutions of 
disinfectants are much more active than cold.* In Belgium, infected 
clothes are boiled in a solution of zinc chloride, or with a mixture 

1 Brit. Med. ./., 1901. 89S. 2 p^uic Health, May, 100:?. 

' See also Medical ]Vurld, December 17, 1808. * Arch. Uyg.. 15, 55. 



DISINFECTION OF ROOMS 09 

of 240 grammes zinc sulphate and 120 grammes salt dissolved in 
a ]iail of water. Commercial zinc salts cannot be used, as the 
presence of iron salts causes them to ])roduce stains on linen. At 
Aberdeen the Medical Officer of Health reports' that house, bedding, 
and clothing are dealt with, and other details are treated. A\ith 
exceptional care. The infected rooms are fumigated with sulphur, 
washed with water containing formalin- — a sufficient Cjuantity of 
which is supplied gratuitously for each case by the sanitary depart- 
ment — and the clothing and bedding are removed for steam disin- 
fection at the disinfecting station. 

Hospitals obviously need special precautions, and are generally 
provided with their own steam disinfecting plant, and in many cases 
with cremators for the destruction of infectious stools, bandages, and 
valueless articles. The polished wood floors are cleansed regularly 
with 1 in 20 carbolic acid or an equivalent of another disinfectant, 
and the walls, fittings, and utensils- are attended to in the ways 
we have indicated. 

Clothes, bedding, woollen, and other articles are most reliably 
disinfected b^- steam at a temperature not exceeding 225° F. 

Articles consisting of a porous or felt-like structure are, owing 
to the presence of the air imprisoned in the meshes, bad conductors 
of heat, as is shown by the following experiments of Whitelegge. 

A roll of blanket was kept in a hot-air oven between the tem- 
peratures of 245° and 255^ F. for eight hours. After this period the 
temperature at various depths of the roll was obtained and recorded 
as follows : 

Under 2 layers 230° F. 

„ 4 „ 22rF. 

„ 6 „ 215° F. 

„ 12 „ 196° F. 

When, however, such materials are exposed to a current of 
saturated steam, some of the steam condenses in the process of 
warming up the object; the laminae or spaces left by the steam on 
condensation provide a means for fresh steam to j)enetrate and 
condense in the deeper layers; penetration can in this way take 
place through the twelve layers in from ten to fifteen minutes. It is 
evident that current steam offers considerable advantages over a 
dry heat, unsaturated steam, or a mixture of steam and air. This 
principle is the basis of modern steam disinfectors. .Steam dis- 
infectors are generally of one of two types — low-pressure or high- 
pressure disinfectors. 

1 Public Hecdth. July, 1903, 584. 

^ See an article by Dr. Lovii.'* I'arkcs, ihid.. .riiiw. 1!)();$, r.-ld. 



100 DISINFECTION AND STERILIZATION 

Although steam at low pressure penetrates bulky articles more 
slowly than steam at high ]iressure, and a somewhat longer time of 
contact is required to ensure proper disinfection, yet the greater 
simplicity and lighter construction of the low-pressure types offer 
advantages which are not present in the somewhat more efficient 
type. 

When a steam disinfector is installed in a school, hospital, A\ork- 
house or similar building, the following points should be attended to : 

1. The same attendants should always work themachme. When 
a new attendant is put in charge, care should be taken to instruct 
him how to work the machine properly. 

2. A recording thermometer or thermograph has a great advan- 
tage over the usual thermometer fitted, since it offers definite proof 
of negligence on the part of the employe or unsatisfactory A\'orking 
of the machine. 

3. When the machine is situated in the building itself, care should 
be taken to ensure that only the proper attendant has access to the 
entrance and exit doors of the disinfector. 

4. The attendants collecting the infected clothes should pass 
their overalls through the machine before removing the disinfected 
articles, and should also wash their hands with some disinfectant 
solution. 

5. The room in which the entrance door of the disinfector is 
situated should be frequently sprayed with disinfectant solution. 

The public laundry is occasionally, although rarely, responsible 
for the spreading of infectious diseases, either indirectly from in- 
fected clothes sent to the laundry or direct from one of the operators 
in the laundry. Sir Thomas Oliver^ finds that in some cases the 
number of laundresses subject to pulmonary tuberculosis was in the 
proportion of 1 to 11. Although disinfection may be accomplished 
in the process of boiling for certain materials, others, such as silk 
and woollen goods, cannot be boiled, whilst in any case the after- 
process of " doing up " and sorting all increase the risk of infection. 
Oliver advised that all bundles of clothing, as soon as they are 
opened at the laundry, should l)e immersed in some disinfectant 
of controlled strength, and this suggestion was approved of by the 
Laundry Journal (February 10, 1910). 

In the post offices of the French Government, dry sweeping and 
sprinkling with water are forbidden, while rooms with tiled floors 
are flushed with water every day. Parquet floorings, it is ordered, 
are to be wiped over daily with hot turpentine, sprinkled with damp 
sand, and swept. Once a week the floors are sprinkled with a dis- 
infectant. It is further advised that tables, desks, and telephone 

^ " Diseases of Occuimtion." 



DISINFECTION OF ROOMS ' " 101 

apparatus should be wiped with cloths dipped in a similar disin- 
fectant. Systematic disinfection is also required in museums, 
churches, and public libraries. In these it is a frequent practice, 
as at the Chicago Public Library, to use an ozonizer in conjunction 
with the ventilating system ; we have, however, previously pointed 
out that the risks of aerial-borne infection are very small, and that 
ozone, although very effective for removing odours and generally 
for " freshing up " the air, would, in the concentrations neces- 
sary for sterilization of the objects with which it came in contact, 
act on the mucous membrane and cause sore throats. In libraries, 
the chief source of infection, as showTi by M. Cazal and Chatrin, is 
to be found in the handling of books previously exposed to the 
proximity and contact of an infected person. Stringent enforce- 
ment of regulations in England under the Public Health Act of 
1875 has done much to minimize this evil, especially with respect 
to circulating books in infectious houses. It might be mentioned 
that the moistening of the finger with saliva for the purpose of 
turning over the leaves in a thin-leaved book is a particularly per- 
nicious practice. There is no good method of disinfecting books 
without affecting the bindings. 

Stables, pigsties, and cowsheds require to be regularly cleaned, 
and to be periodically disinfected, like rooms, with removal of the 
animals, to prevent disease occurring. It is of little use to be per- 
petually deodorizing with powders. Dryness, ventilation, and 
cleanliness are better safeguards. 

For cattle-markets and fairs a cresol disinfectant is probably 
the best. A description of the chief ones is given in Ch. XII. 

Slaughter-houses are particularly difficult to disinfect on account 
of the large amount of albuminoid matters present. It has already 
been noted that it is almost impossible to sterilize blood in the cold. 
Mercuric chloride and phenol are unsatisfactory because of their 
action on albumin: chlorine and sulphurous acid are rarely to be 
recommended; wood charcoal only serves to deodorize, and does 
not disinfect. Copper sulphate is one of the most useful agents in 
these places, but cleanliness and rapid removal of offal are the first 
considerations. Cunliffe and Barlow subject the refuse to heat and 
destructive distillation. Slaughter-houses for infected or suspected 
animals are usually situated near seaports, and require special 
methods of isolation and extra precautionary measures. 

In the Diseases of Animals (Disinfection) Order of 1900 the mode 
of disinfection to be adopted in the case of glanders or farcy and 
foot and mouth disease was prescribed as follows: 

The place or thing, or the part thereof required to b(> disinfected, 
shall be thoroughly coated or washed witli : 



102 BISINFECTION AND STERILIZATION 

(a) A 1 per cent, (minimum) solution of chloride of lime con- 
taining not less than 30 per cent, of available chlorine; or (6) a 
5 per cent, (minimum) solution of carbolic acid (containing not less 
than 05 per cent, of actual carbolic acid), followed by a thorough 
sprinkling with limew^ash; or (c) a disinfectant equal in disinfcctive 
efficienc}^ to the above-mentioned solution of carbolic acid, followed 
by a thorough sprinkling with limewash; and these alternative 
modes of disinfection were authorized generally for othei orders 
in which disinfection with limewash or a solution of carbolic acid 
and limewash is prescribed. 

Vehicles. — In cases of supposed infection, Sanitary Inspectors 
are authorized to disinfect without charge, and give a certificate. 
Cushions and removable fittings are sterilized in a steam oven. 
Formerly all exposed woodwork was washed with carbolic soap, 
and carbolated oil was smeared over metal-work with the view of 
disinfecting it and also protecting it from chlorine, -VA'hich was then 
evolved inside by one of the methods given on p. 97, and the 
vehicle was shut and left so for an hour. Sulphurous acid or 
formalin is now used, and a longer time is allowed. 

A systematic disinfection of railway carriages under a uniform 
system is urgently needed. At the International Congress of 
Hygiene, Brussels, 1903, it was resolved that: (1) Fittings should be 
arranged to facilitate cleaning and disinfection, with the suppres- 
sion of loose textile materials, and easy removability of cushions 
and furniture. (2) Cleaning of surfaces by damp cloths and removal 
of dust by a vacuum apparatus were recommended. (3) l^isinfection 
must be regular and frequent, apart from any incidence of excep- 
tional disease, and must include (a) complete disinfection of remov- 
able furniture; (6) washing of surfaces and spraying with antiseptics, 
or efficient fumigation wdth formaldehyde or other effective agent; 
high-pressure steam at 110°, or dilute hypochlorites, were effective, 
but were liable to cause damage. (4) Special conveyances are 
required for the sick and for dead bodies; the latter should be in 
sealed coffins, and for long distances should be embalmed. (5) An 
International Commission should be appointed to fix, by methodical 
experiments, standard methods and regulations to be adopted. 

With reference to cattle and luggage waggons the Congress 
resolved that the former ought to be disinfected after each journey, 
and the latter after they had carried putrescible or suspected sub- 
stances, with in each case a previous thorough cleaning. See the 
valuable reports of Redard, Csatary, and Adolph Freund of the 
practice on French, Hungarian, and Austrian railways. The latter 
showed that after the most careful cleaning with very hot water 
there remained an organic film which required repeated irrigation 



DISINFECTION OF VEHICLES 103 

with an active disinfectant. He prefers hypochlorites in dilute 
solution, and uses simple spraying apparatus. 

The C.P.R. cars are subjected to systematic disinfection on the 
lines recommended by the Brussels Congress. The car is stripped 
of everything movable, then swept and brushed out, finishing with 
vacuum cleaning. The car is then washed both inside and outside, 
and once a fortnight fumigated with formalin. 

Previoush' to the installation of the vacuum process compressed 
air was used for cleaning; this method is most unhygienic. The 
adequate washing and disinfection of pillows, sheets, and blankets 
on sleepers is still a matter of difficulty, and the present position, 
relying on inspection as to visible dirt, is far from satisfactory. 

The disinfection of ships is in many respects similar to that 
adopted for houses and public rooms ; the passengers and crew, with 
all their personal belongings and effects, are landed, while a dis- 
infectant boat is run alongside or the vessel is brought alongside 
the pier on which the necessary fitments are situated. In the case 
where a complete sterilization of the whole ship is necessary, all 
movable fixings, including bedding linen, are removed and disin- 
infected by steam (see p. 99). Saloons and cabins may be sprayed 
down with formaldehyde solution, while the steerage and men's 
quarters are washed with mercuric chloride or, better, a tar acid 
disinfectant solution. Accessible surfaces which are in constant 
use must first be washed with soda solution to remove grease. 
Bright metal- work is seriously affected by mercuric chloride and by 
sulphur fumes, and should therefore be washed M'ith formaldehyde 
or tar acid disinfectant. The hold is usually sterilized by pumping 
in sulphur dioxide through supply pipes or burning roll sulphur 
3 to 5 pounds per 1,000 cubic feet in iron pans in the hold itself. 
This is followed by drawing fresh air through. 

The New York Sanitary Officers have been making experiments 
with strongly ozonized air for this purpose. 

Special attention must be j^aid to rats, mosquitoes, and other 
disease carriers frequenting ship-holds. 

The laying of dust on roads is receiving much more attention 
than formerly. This is all the more important as the traffic on the 
roads increases, although the conversion of horse traction into 
mechanical is a change for the better as far as the question of con- 
tamination is concerned. 

The increased use of kyanized wood paving, asphalt, tar macadam, 
and similar materials on roads, tends to make the dust both less and 
less contaminated than on the older type of water-bound surface. 
The daily flushing of manholes, traps, and gullies, especially in hot 
weather, with some disinfectant solution is a valuable precaution. 



104 DISINFECTION AND STERILIZATION 

Permanganates and hypochlorites are frequently employed for 
this purpose. Although they are very effective smell removers, 
and are doubtless used for that purpose, yet, OAving to their instability 
in the presence of organic matter, effective sterilization of the road 
surface or the manholes never is obtained by the ordinary practice 
of municipal authorities. This is well shown in the following- 
experiment : 

Two spaces, each 27 square feet on the asphalt in Victoria 
Street, London, outside oui laboratory, were watered — (a) with 
2 gallons of water; (b) Avith 2 gallons of water containing 1 : 5,000 
potassium permanganate. The runnings from each were ladled 
into bottles and submitted to analysis, with the following results: 

Colonies per Cubic Centimetre. 

Gelatme plates at 22° C. [ j^j ^'^^s qoo 



iia) 0-001 c.c. gave numerous colonies, 



Agar plates at 37-5° C. - f"'^ the plates were crowded in 

° ^ I twenty hours. 

\{h) 0-10 c.c. ditto. 
Carbolized gelatine plates \{n) 122.200 
at 22° C. \{h) 4,830 



BIBLIOGRAPHY. 

Campbell, A. E.: Some Important Phases of Railway Sanitation, J. Amcr. Med. 

Assoc, 1914, 63, 2032-2037. 
Bennett, F. C: Practical Ventilation, Med. Times, 1914, 42, 368. 
Chapdj, C. V. : Of Wtat Value is House Fumigation after Infectious Diseases ? 

Amer. J. Pub. Health, 1914, 4, 1202-1204. 
DowLiNG, 0.: The Hygiene of Jails, Lock-Ups, and Police Stations, J. Amer. Inst. 

Criminal., 1914-15, 5, 695-703. 
Manheimer, W. a. : Floor Oil as a Dust Preventative. Amcr. Phys. Ediic. Rev., 1914, 

19, 625-631. 
Neri, F.: Semplificazionc della determinazione dell' umidita muri, nuova stufa 

per essicaraento in aria calde stagnante, Nota II. Igiene mod., 1914, 7, 337-346. 
Whipple, M. C: Further Studies in Air Washing at the International Y.M.C.A. 

College, Springfield, Mass., May, 1914, Amer. Phys. Educ. Rev., 1914, 19, 621- 

624. 
Cooke, D. L. : Car Ventilation. Trans. Amer. Soc. Vent, and Heat. Eng.. 1914, 20, 

253-278. 
Douglas, R. L. : Ventilation of Telephone Booths, including Other Applications of 

Small Unit Sets, ibid., 330-336. 
Franklin, M. W.: Air Ozonation, ibid., 1914, 20, 337-364. 
Larson, G. L. : Recent Tests on Recirculation of Washed Air, Metal Worker, etc., 

1915, 84, 675-677. 
0l,sen, J. C, and Ulrich, W. H. : Ozone in Ventilation : An Exposition of Faulty 

Methods of Investigation heretofore Emploj-ed, Scient. Amcr. Supjj., 1915, 

79, 34. 



DISINFECTION OF VEHICLES 105 

Gbhbmann, a.: Auti-Spitting Signs and the Control of Expectoration, Illinois 

Med. J., 1915, 27, 132-134. 
WiNSLow, C. E. A., Kemball, E. (et al.): Some Results of the Eirst Year's Work 

of the New York State Commission on Ventilation, Amcr. J. Puh. Health, 

1915, 5, 85-118. 

Sampirtro Galligo, J.: Higiene y patologia del submarino, Clin. Mod., 1915, 
14, 210-225. 

Whipple, M. C. : The Results of Studies upon the Dust and Bacteria Content of 
Air of Cities, Amer. J. Puh. Hecdth, 1915, 5, 725-737. 

Greeley, S. A., Hering, R. {et al): Report of the Committee on Refuse Collection 
and Sewage Disposal, Amer. J. Pub. Health, 1915, 5, 933. 

Abbott, A. C. : Ventilation in its Relation to Air-Borne Diseases, Science, 1915, 
U.S., 42, 358. 

Sweet, E. A.: Sanitation of Railway Coaches, Virginia Med. Semi-Month., Rich- 
mond, 1916, 21, 235-240. 

Crowther, T. R.: The Sanitation of Railway Cars, Puh. Health Rep., Washington, 

1916, 31, 2135-2147. 

Allen, J. R.: What We Do and Do Not Know about Heating, Trans. Amer. Soc. 

Heat, and Vent. Eng., 1917-18, 24, 271-277. 
Alt, H. L. : Relation of Hot Water Service Heating to Various Types of Buildings, 

ihid., 261-269. 
Gaub, I.: Co-operative Sanitary Improvements for the Landlord, Puh. Health 

Mich., 1917, 5, 551-553. 
Latjr, F. : Regeneration des atmospheres confines, Rev. d'hyg., 1917, 39, 233-240, 

421. 
McBride, R. S., and Reinicker, C. E.: Gas Mantle Lighting Conditions in Ten 

Large Cities in the United States, Washington, 1917, Govt. Print. Off., 37 pp., 

8vo. (Technol. Papers, Bureau of Standards, No. 99). 
Cassel, J. D. : Heating, Ventilating, and Electrical Equipments of the Philadelphia 

School Buildings, High and Elementary, Trans. Amer. Soc. Heat, and Vent. 

Eng., 1917. 23, 281-295. 
Allen, J. R. : Hot Blast Warm Air Heating Comparison of Pipe Coil Heaters and 

Cast-iron Sections for Warming Air, 3Ietal Work, etc., 1917, 88, 69-72. 
Mussulman, S. ¥.: The Cleaning and Disinfection of Live Stock Cars, J. Amer. 

Vet. Med. Assoc, 1918, n.s., 6, 85-96. 
Rosenberger, R. C: A Bacteriological Study of Cigars, N.Y. Med. J., 1918, 

107, 865. 
The Aridity of Heated Bedrooms. Boston Med. and Surg. J., 1918. 178, 721. 
Reckford. F. F. D. : The Relation of Fresh Air and Housing to Health, N. Y. Med. 

J., 1918, 107, 976-978-. 
Bas,s, F.: Recent Progress in Ventilation, Amer. J. Puh. Health, Concord, N.H., 

1918, 8, 434-436. 
Pierce, W. D.: The Control of the House-Fly and Related Flics, Proc. Class Sludij 

Entomol. Dis., Washington, 1918, 180-186. 
Cory, E. N.: The Control of House Flies by the Maggot Trap, College Park. Ind., 

1918, Maryland State College of Agriculture, 22 pp., 12. 

Redway, J. W.: The Du.st Problem in School Buildings, Med. Times, 1918, 46, 

258-260. 
Selter, H.: Final Disinfection of Sick Rooms, Deutsch. Med. Wochcnsch., July 31, 

1919, 45, 846. 

Reed, C. I.: Wliy is Poor Ventilation Harmful? Discussion of Fundamental 
Psychologic Bases of Current Views, Amer. J. Pub. Health., September. 1919, 
9, 668. 



CHAPTER VI 

PERSONAL AND INTERNAL DISINFECTION 

The " last liiie of defence " includes the precautions taken by the 
private individual. These may be considered to include cleanli- 
ness of the person and purification of the clothing, the importance 
of cleanliness of the home having already been dealt with. 

In the transference of disease by direct contagion in those cases 
where it is evident that milk or water is not the intermediary, it 
is usual to look for some article that has been exposed or may have 
been exposed to direct contamination. 

Dr. Park of the New York Board of Health and Professor 
Hildish of Yale have found that the small paper money notes 
current in the U.S. and Canada frequently contain pathogenic 
bacteria. Dr. Basquet of Bordeau proved that tram, railway, 
and omnibus tickets frequently serve as carriers of disease ; metallic 
coins are also not free from this defect. C. E. Winslow^ has shown 
that internal bacteria are frequently transferred to the exterior of 
the body, and thus a direct route of infection is provided. Under 
such circumstances typhoid fever and similar diseases may, for all 
practical purjooses, become a contagious disease. This point was 
first suggested by Sedgwick and Winslow,^ and subsequently deduced 
by Notter^ on investigating the casualties from enteric fever among 
the British troops in South Africa. For this reason disinfection of 
the skin is frequently advocated. 

In fever cases it is now generally customary to sterilize the hands 
by washing in a 1 per mille solution of mercuric chloride with a 
little salt and hydrochloric acid (p. 95), and rinsing them with plain 
water before washing with soap. In cases of very great danger the 
clothes are afterwards disinfected by steam. Although many other 
antiseptics have been proposed for the hands, mercuric chloride 
seems still to be one of the best; it should not be diluted beyond 
1 in 1,000. The same solution should also be used by nurses and 
attendants when leaving the room ; a convenient way of preparing 
it is to dissolve one " soloid " in a pint of water, taking care to stir 

1 ,/. Med. Research, 190.'J, 10, 3. 
- Trans. Amer. Public Health, 1902, 28, 288. 
3 Rei>ort 1903, App. iii., 131. 
106 



PERSONAL AND INTERNAL DISINFECTION 107 

well till all has dissolved. Infectious matter is particularly liable 
to remain under the nails. 

The disinfection of the hands and instruments in surgery has 
been the subject of numerous investigations. Reinecke and others 
prefer alcohol, which, however, is hurtful to the hands. Dr. R. E. 
Weir^ pronounced chlorine to be less injurious and equally efficient. 
He places " a large pinch " of bleaching powder in the palm of the 
hand, then a crystal of washing soda " about 1 inch wide," and a 
little water, rubs the resulting cream (sodium hypochlorite and 
calcium carbonate) for three to five minutes over the hands and 
arms, and washes off in sterile water. 

Professor Mukulicz finds from a series of tests that it is impossible 
to render the hands perfectly aseptic. He first disinfects his hands 
as far as possible with alcohol and mercuric chloride, and then draws 
on a pair of cotton or linen gloves j^reviously sterilized by boiling. 

Regarding the value of alcohol as a disinfectant for the hands, 
Salzwedel and Eisner- maintain that alcohol is of use in prej^aring 
the hands for operations, not merety because of its hardening effect 
on the epidermis, but also as an active antiseptic ; they consider it 
intermediate betw^een carbolic acid and corrosive sublimate. The 
hands, after washing with soap and water, should be well soaked 
in 80 per cent, acidulated spirit before operating. 

E. C. Hansen^ states that epidermal bacteria, especially in cases 
of suppurating eczema, are, when moist, killed in one minute by 
absolute alcohol, and in most cases by 50 to 60 per cent, alcohol. 

This statement is also supported by G. N. Brockhart^ and by 
A. Fabludowski," ^vho finds that the value is considerably increased 
by the addition of tannic acid, and that the hands can be sterilized 
by two minutes' immersion in the liquid. 

Glycerol, when heated to 120°, is. according to iheBrifish Journal 
of Dental Surgery. 1916, most effective for rendering instruments, and 
especially rubber tubing, sterile. The rubber is said to be rendered 
extremely elastic and supple by this treatment. 

Thoroughly drying the cut and painting with a solution of 
Stockholm tar or Burgundy pitch in alcohol, ether, or acetone, is 
among the other treatments suggested. 

Sterilizing the skin with iodine has been investigated in some 
detail by Groslich,^ Routier,'^ Porter,^ Stretton^ and others with 

1 N.Y. Med. Record, April 3, 1S97. 409. 

- Berlin. Clin. Woch., June 4, li)()(). '^ Zcilt^ch. (jcs. Brunc. lilOS, 31, oO. 

* Monatsli. jmikt. Demat., 1911. 52, 1- ^ Deutsch. Med. Wochenschr., 1911, 405. 

6 A. Grossich, Zentr. Chirurg., 19US, No. 4 ; Prescriber, 1909, 42. 

' Routier, Semaine Medicable, January (5, 1909. 

8 F. W. J. Porter, Brit. Med. J., February 6, 1909. 

» J. Lionel Stretton, ibid., August 14, 1909; Prescriber, 1909, 165. 



108 DISINFECTION AND STERILIZATION 

favourable reports. Waterhouse/ using a 2 per cent, solution in 
rectified spirit, and Bogden- a 1 per cent, solution in benzene, have 
recorded its similarity in connection with surgical operations. Lance 
recommends it as an application for the bites of animals and insects, 
and Brewitt'' advises a solution of iodine in benzene and paraffin 
for subjects with sensitive skins. Turner and Catto* use a mixture 
of iodine tincture and methyl alcohol with good results. Heussner's 
solution of iodine in benzene has been used with success by Levy 
and Horrmann,'' and by the various medical units in the European 
War. The coloration of the skin caused by such tinctures is their 
chief disadvantage, but such can be removed by a solution of 
sodium thiosulphate. 

None of these give absolute immunity, so that, in case of acci- 
dental puncture during a fost-mortem or operation, or in handling 
contagious matter, such as dead meat, skins, or evacuations, it is 
probably safest to wash immediately with mercuric chloride, dry, 
and at once cauterize, and thus combine the two precautionary 
measures. When, unfortunately, the abrasion has not been noticed 
at the time, this treatment should still be resorted to. Afterwards, 
hypodermic injections of an antiseptic have been recommended, and 
cinnamic acid, styrol, phenyl-propionic acid, ^-naphthol. and betol 
are used for this purjDose ; phenol, or any other reagent which coagu- 
lates the blood, is, of course, inapplicable. For ordinary bites and 
scratches similar treatment may be adopted; the part should be 
afterwards protected by antiseptic gauze or wadding. Burns and 
scalds are liable to septic poisoning if the epidermis is broken, so 
that, they also should be protected, but not cauterized. Wasp- 
stings and insect-bites have caused death. The best remedies are 
liquor plumbi subacetatis or Goulard's extract, and the old- 
fashioned hartshorn and oil. 

Zinc peroxide, "Ectogan," is said to be often useful in the 
treatment of ulcers. 

Disinfectant Soaps and Ointments. 

In spite of increased knowledge of disinfectants, little attention 
seems to have been paid by soap manufacturers to this subject, so 
that soaps which were introduced many years ago still find favoiir 
with the public, although their efficac}' as germicides is very small. 
This has arisen partly from the fact that it is seldom that disinfec- 

' 11. F. Waterhouse, Lancet, April 16, 1910. 

- A. Bogden, Zentr. Ghirurg., January 15, 1910. 

^ Brewitt., Munch Med. Wochenschr., February 8, 1910. 

* Turner and Catto, Lancet, March 18, 1911. 

5 Munch. Med. Wochenschr., 1911, 1130. 



PERSONAL AND INTERNAL DLSINFECTION 100 

tant soaps are properly tested as to their germicidal action upon 
specific organisms under conditions which approximate to their use 
in practice, and partly owing to the fact that there are many dis- 
infectants which have valuable properties as such, but A\hich are 
totally unfitted for use in conjunction with soaps. 

The conditions which obtain when a disinfectant soap is used 
are very different from those of ordinary disinfecting. As a rule, 
the time of contact is much shorter, and the volume of water or 
vehicle much less. As the time of contact is short, so it is necessary 
that the percentage of active ingredient should be high. As the 
volume of water used per unit weight of clismfectant soaj^ is usually 
much less than is recommended when a liquid clismfectant is em- 
ployed, this will assure a higher percentage strength of the active 
ingredient if it is present in the soap in anj'thing like reasonable 
proportions. On the other hand, it is important to note that, 
unless the disinfectant emploj^ed is readily soluble in water, actual 
contact of the infected parts with the disinfectant cannot be attained 
in the limited time given to washing. In coal-tar soaps and those 
containing oils which are not very soluble in water, although the 
disinfectant is emulsified by the soap, the actual laving of every jDart 
of the infected area by the active ingredient for the necessary time 
to effect the death of the micro-organism is by no means certain. 
Organisms differ very markedly in their resistant power. Manj- 
of them form spores which are especially difficult to kill, so that 
even when a soap contains an approved disinfectant, the latter must 
be present in quantity above that required for the fatal dose for the 
most resisting spores. 

It is of extreme importance to the soap manufacturer that he 
should not only carefully select his disinfectant and ascertain its 
purity and efficiency, but should also devote especial care in admix- 
ing this ingredient in the right proportion, the exact amount of the 
medicament being stated on the wTapper of each piece. 

The disinfectant power of warm 2 per cent, soda solutions is 
considerable, even without the presence of any fatty acids, and 
they can be used with advantage for scrubbing floors, mantelpieces, 
and furniture. At 60° C. a contact of five minutes ensures the 
death of most organisms. i 

The stock or basis of a medical soap or ointment is by no means 
unimportant. It is necessary that the medium in itself should 
produce no disturbing action ; therefore in many of the best-kno\\ n 
brands great care is devoted to the attainment of chemical neu- 
trality — i.e., that the fatty acids and alkali shall be combined in 
molecular proportions, since free fatty acids are said to induce in- 
^ Simon. Zeilsch. Ilyij., 1903, IMi); also Kiirpjiiwoit, loc. cit., 300. 



110 DISINFECTION AND STERILIZATION 

flammation, while any large excess of alkali is known to be irritant. 
Raw materials are carefully selected as neutral, uncoloured, and 
almost inodorous glycerides. It is probable, however, that such 
expensive precautions have been too far insisted on, as even a 
chemically neutral comjiound of a fatty acid with an alkali is de- 
com230sed in contact with water, a portion of the potash or soda 
being set free. F. Krafft and A. Stern, ^ in confirmation of Chev- 
reul's early work, have found that soap in a large quantity of hot 
water gives a precipitate of the sodium salts of palmitic and stearic 
acids, while sodium oleate, not being so readily decomposed, remains 
in solution along with free alkali. An olein basis would therefore 
seem preferable to the employment of a harder fat. At the same 
time, since for disinfectant soaps the chief condition is that the agent 
should be rapidly disengaged in sufficient quantify in contact with 
the surfaces, a softer and more easily dissolving soap is directly 
indicated. 

The alkali of commercial soap is, of course, soda, but potash or 
soft soap figures in several Pharmacopoeias as " Sapo kalinus," 
" viridis," or " mollis." It is generally made with linseed oil {B.P 
olive oil), has a pale brownish-green colour, and is reckoned to be 
specially beneficial in some skin diseases. It would be useful to 
determine whether an admixture of a potash soap with the ordinary 
soda soap would produce a basis giving greater activity when used 
in such proportion as not to give too great softness to the product. 
E. W. Lucas has already shown^ that a mixture of 1 pai't potash 
soap to 5 of soda soap solidifies, and can be advantageously em.- 
ployed as a basis for liniments. The solubility of drugs in a potash 
soap does not appear to have been investigated. The chief objec- 
tion to commercial soft soap is that, not having been " salted out " 
or separated, as soda soaps are, it retains, besides a large and very 
variable amount of water, all the glycerine of the original fat, and 
in addition the saline impurities of the alkali used, some of which 
may interfere with the action of the medicaments. To meet this 
objection, Miiller and Graube^ have prepared a "pure soft soaj]," 
which they term "Savonal," by saponifying olive oil in the cold 
with alcoholic potash (which contains almost exclusively potassium 
hydroxide, most of the impurities being insoluble), and neutralizing 
the resulting solution by careful addition of fatty acids obtained 
from a portion of the alcoholic soap by precipitation with hydro- 
chloric acid. The alcohol is then distilled olT in a water-bath, when 
" Savonal " in an unctuous condition is left. It will be noticed 
that the glycerine is still left in. A really pure soap, if necessary, 

^ Ber., 27, 1747. - B.V. Conference, 1894. 

^ Pharm. Zn'f., 1807, 540; Nniivemix Remedcs. 13, 4;{7. 



PERSONAL AND INTERNAL DISINFECTION HI 

could be quantitatively prepared by saturating alcoholic potash 
with the washed fatty acids, also dissolved in alcohol. By testing 
measured portions, using phenolphthalein as an indicator, the 
relative amounts of the two solutions could be obtained. Heat is 
avoided as much as possible, on account of the production of odour 
or colour. A liquid is prepared b}^ adding " a few percentages of 
glycerine " and enough distilled water to make up the specific 
gravity 1-050 to 1-055; this is used as a medium for many drugs. 
Among the strengths given are : Phenol, naphthol or resorcin, 5 per 
cent. ; salo 15 to 10; cresol, 0-25 to 2; chrysarobin, 10; iodine, 1 to 2, 
with 10 per cent, of potassium iodide.^ 

Many of these antiseptics will not dissolve to a clear liquid in 
the aqueous soap. If the alcohol were not all distilled off he 
solubility would be often increased, the product approximating to 
many of the official Linimenta. 

Wunscheim states that phenol, orthocresol, Ijsol and creolin 
have less disinfecting power in glycerine soap solutions than in 
aqueous soap solutions of the same strength.' 

LTnna and others are of opinion that medicaments are more 
easily absorbed if the soap is " superfatted," or contams an excess 
of the fatty menstruum; but however preferable for toilet pur- 
poses as more emollient to the skin, these soaps seem not to be so 
suitable as vehicles for many drugs as those containing a moderate 
excess of alkali. The presence of free oils or fats is distinctly 
inimical to antiseptic action. Koch was the first to point out that 
carbolic acid dissolved in olive oil, or " carbolized oil," possessed 
no antiseptic properties. Lenti^ concluded from his observations 
that fatty substances are unsuitable vehicles for disinfectants, as 
they impeded the germicidal action of mercuric chloride, phenol, and 
several other bodies. 

J. Bosisto states that an ointment containing simj^ly the volatile 
oil of eucalyptus is inferior to the fresh leaves as used in Australia.* 
E. Sage^ says that neither vaseline nor lard is a suitable solvent for 
a preparation of cocaine, and that the idea of the superiority of 
such a preparation to one containing the hydrochloride, dissolved 
in a little water and rubbed up with fat, is fallacious. Dr. Bres- 
lauer's experiments with mercuric chloride, boric acid, silver nitrate, 
etc., admixed with oil, vaseline, lanoline, and other excipients, 
])rove that while the lanoline gave the best results, the presence of 
the free oil or fat in all cases strongly militated against the germicide, 
various bacilli surviving in oil far longer than in aqueous solutions. 

1 Year Book Phann., 1900, 209. 2 chem. Zentr., 1901, i., 408. 

^ Union Pharmucentiqiic, 35, 58. * Pharm. J., [iv.], 2, 224. 

5 Ibid.. 3, 28. 



112 DISINFECTION AND STERILIZATION 

It would seein, therefore, that the presence of water was necessary 
to the antiseptic and even to the full medicinal action of ointments 
(Avhich would explain the above result with wool fat or lanoline, 
containing as it docs about 25 per cent, of diffused water), and that 
it would be preferable to mix in a mortar an aqueous solution of 
the drug with the fatty basis shortly before being used, as these 
moist ointments in many cases do not keep well. A. St. Onge* gives 
a table of the ]iroportions of water, alcohol, and glycerine, which he 
found miscible with various fats. 

Dr. Baldas^ found no pathogenic organisms in crude oils of 
commerce, but proved that if they were introduced, they could 
remain in the oil and retain their virulence for two months unless 
the oil were heated. He remarks that this should lead to great 
care with regard to the oils used in medicine and surgery. 

Vicario noticed, in 1891, that fixed oils frequently contained 
germs. Cutting oils employed for lubrication in lathe work are 
often badly contaminated, leading to sickness of the operatives. 
From these and other observations it has been recognized that oils 
and fats used in ointments and soaps must be sterilized by heat; 
usually this is done in course of manufacture. 

It must be remembered that soaps themselves have considerable 
antiseptic power. The early experiments of Max Jolles^ have 
shown that in the case of tjrphoid bacilli the disinfecting action is 
more marked at 4° to 8° C. than at ordinar}^ or higher temperatures, 
therefore that with cold water soaps would be more active than 
with hot. When rags infected with the germs were treated with a 
soap solution the effect was very marked, even a 1 per cent, solution 
being injurious to the germs in fifteen minutes, and a 6 per cent, 
solution resulting in their entire destruction. A 3 per cent, solution 
was fa.al in one hour, and in 1 per cent, no germs remamed capable 
of development after two hours' immersion. B. coli communis was 
less easily destroj^ed; at low temperatures a 2 per cent, solution was 
fatal in six hours. According to Harz and Von Miller, a solution of 
1 in 1,500 or 1 in 2,000 of soapy water is fatal to all injurious plant 
parasites. 

There is no doubt that prolonged contact with soap renders 
surfaces practically sterile, but, under common circumstances, 
ordinary soap fails to be effective. 

Reithoffer' refers to the different behaviour of various germs to 
soap solutions. Thus anthrax bacilli are easily killed in weak 
solutions (?), but typhoid and cholera germs are far more resistant. 

1 Zeitsch. ocstcrr. Apoth. Verein, 34, 712; Year Book oj Phcrmacy, 1897, p. 210. 

2 Qiorn. Real. Soc. Ital. Ig., February, IDOL 

3 Zdtsch. IJyrj., 18i)5, 130. ^ Arch. Jlyg., 27, H. 4. 



PERSONAL AND INTERNAL DISINFECTION US 

He notes that in Behring's opinion the disinfectant power of a soap 
is dependent on its alkalinity. Experimenting with common soft 
soap, with scented almond soap, and with a patent potash soap, 
Reithoffer found that they all had a high degree of disinfecting po^^■er 
against typhoid bacilli, B. coU, and the cholera organisms, but their 
action is very feeble against pus cocci. Staphylococcus pyogenes 
aureus will remain unchanged for an hour or more in 18 to 20 per 
cent, soaj) solution, whilst a 10 per cent, solution of the same soap 
will kill typhoid bacilli in one minute. Experiments with carbolic 
and lysol soaps showed that although the power as tested on cocci 
was slightly higher than the simple soap, yet it was much weaker 
than was a solution of the disinfectant without the soap. From 
these observations it may be concluded that in surgical practice 
the use of a disinfectant soap is inefficient, the better plan being 
to wash first with soap, and afterwards to apply an antiseptic 
lotion. 

Beyer^ has shown that in the case of hosjiital clothing with 
various surgical stains, soaking the garments in solutions of various 
soaps for one or two days failed in every instance to kill cholera, 
typhoid, and pyogenic organisms. He attained success with lime- 
water in from twenty-four to forty-eight hours, but woollen goods 
were spoiled. In this case, if the soap had been supplemented 
by a good antiseptic, more favourable results might have been 
attained. 

Reichenbach," investigating the germicidal power of the alkali 
salts of the fatty acids, found that the palmitates had the strongest 
bacterial action. The potassium salts of the saturated fatty acids 
are comparatively strong bactericides, but the unsaturated acids, 
^\■ith the exception of elaidic acid, are not. 

With reference to medicinal agents used in soaps, acids and free 
halogens are obviously incompatible, the former being neutralized 
by the alkali, or precipitating the fatty acid, the latter combining 
at once with the fat. A hypochlorite of K or Na is compatible to 
a certain extent, but the disinfectant action is much less than that 
of free chlorme. The oxygen compounds of bromine and iodine do 
not seem to have been studied in this resj^ect. A vast number of 
organic bromo- and iodo-com])oun(ls have been introduced; some 
of them seem to be useful, but most are irritating; the majority 
have very unpleasant odours. 

Fluorides and silico-fluorides are strongly antiseptic and non- 
poisonous (p. 86), and were patented under the name of " Salufer." 
They might be used in conjunction with soap, as Thompson states 

^ Forlschritt dcr Medicin, No. 1, 1897. 
' Zeitsch. Hyg. Infekt.- Krank., 1908, 290. 

8 



114 DISINFECTION AND STERILIZATION 

that a solution of sodium silico-fluoride is not irritating, and " is 
stronger than 1 per 1,000 solution of HgCIo," and it is obviously 
comi^atible with soap. 

Sulphur. — Sulphur and alkaline sulphides blend well with soap, 
and have long been known as useful in skm diseases. Sulphur, 
even in the form of " milk of sulphur," is very slow in its action, on 
account of its insolubility. The alkaline sulphides are caustic, 
having been used from Roman times as deisilatories ; and recently 
ichthyol and sjahagnol have been suggested as convenient means for 
admmistering sulphur in soaps. Most of these gradually evolve 
HoS, and therefore yield an unpleasant odour, hence are not 
popular, although this gas is a prominent feature of their antisej)tic 
action. 

Boric acid in soaps would be converted into sodium borate, and 
would have little efficiency. It is added to destroy alkalmity. 

Metallic Salts. — ^These can only be introduced into soap in ver}' 
small quantities, as nearly all, except the salts of Na and K, are 
precipitated in an insoluble form, and on washing disappear from 
the water in the curd, which can have little effect or value. 

Various oleates, or solutions of metallic oxides in oleic acid, more 
or less weU defined as compounds, have been introduced into the 
Pharmacopoeias. They mix well with unguents, and are said to be 
more readily absorbed and less irritating than older remedies. 
Hence it has been proposed to incorporate them with soaps. But 
since the efficiency of soap depends upon its solubility in water, the 
curdy precipitate, as mentioned above, is probably inert ; since also 
most oleates of metals are insoluble in water, the question arose as 
to how far an oxide or an oleate could be made soluble for use in 
ordinary washing. As an example, some zinc oleate, B.P., was 
dissolved in a minimum quantity of soda; to the hot clear solution 
10 grammes of yeUow soap were added and incorporated. When 
cold, the soap separated from the mother liquor, which was strongly 
alkaline, and contained practically all the zinc. This process not 
working, zinc hydrate was prepared and boiled Avith soda to form 
a sodium zincate as neutral as possible. Yellow soap was then 
dissolved in the filtered solution, boiled down, and allowed to set. 
It formed a soap of good washing qualities, not unduly alkaline. 
On using with water in the ordinary way, the zinc was found to be 
in solution, showing that there Avas no separation of insoluble zinc 
oleate. It would therefore seem that metallic oxides dissolved in 
soda or potash might give better results than the oleates.^ 

In most arsenical soaps the amount of arsenic present is ahnost 
1 (See J. Hoc. Chiiin. Ind., 1901, 498. 



PERSONAL AND INTERNAL DLSINFECTION 115 

iiihnitesimal, and quite insufficient for antiseptic or disinfectant pro- 
l^erties, although the small quantity with constant use might have 
some effect on the skin. 

The powerfully antiseptic action of mercury salts suggested their 
employment in medicated soaps. It was difficult, however, to 
prevent the production of the insoluble mercuric oleate, which has 
little or no germicidal action, and also prevents the formation of a 
good lather ; while any surfaces on which a mercurial preparation is 
used are liable to become blackened by HgiS. and organic matter is 
apt to reduce and throw the mercury out of action. One form of 
mercurial soap contains mercuric chloride, ammonia-mercuric 
chloride, together with /i-naphthol, eucalyptol, and methyl salicy- 
late. The salts are incorporated with a neutral soap in a dry state 
in the process of milling,, and are therefore possibly present un- 
changed. It is claimed that they are active at the moment of 
decomposition, as in washing, though afterwards converted into 
oleate. 

The double iodide of K and Hg has even stronger germicidal 
])0wers than HgCl.,. In certam proportions it is easity incorporated 
in the soaj) stock, and one of us has found that when dissolved in 
warm water there is no separation of any insoluble mercury com- 
pound. The strength recommended is 1 to 3 of Hglo and 1 to 3 
of KI in 100 of soap. It is said to be effective in a proportion of 1 
part of Hglo to 4,000 of water. A soap of this kind, which is on the 
market, has been found by analysis of some samples to have the 
following composition in the three grades sold : 



Nominal Strength. 


KI. 


TT T Biniodidc, 
^ ••=• KHgl,. 


3 per cent. 
1 

i „ .. .. 


2-25 

0-94: 

0-45 


2-39 , 3-4 
0-63 0-9 
0-26 0-37 



More potassium iodide is therefore present than is sufficient to 
form the double salt. Potassio-mercuric iodide has the advantage 
of being compatible with strong alkalies, as is shown in the prepara- 
tion of the Nessler test; moreover, it does not precipitate albumin, 
and is not easily reduced. Organo-metallic compounds containing 
mercury are frequentty strongly germicidal, and have been incor- 
porated in various soaps. Schrauth^ has stated that only those 
organic mercury compounds are suitable where the mercur}- is 

^ J. Soc. Chon. ind., I'Jll, 3«2. 



116 



DISINFECTION AND STERILIZATION 



combined directly to the carbon atom. He found the most suit- 
able to be the alkali salts of hydroxi-mercury, carboxylic acids, 
and certain halogen hj^droxi-mercury benzoates Schrauth and 
Schoelleri have confirmed the view that some mercury organic 
compounds have strong germicidal action, and that the disinfecting 
power is by no means proportional to the ionization of the mercury 
salt, as was formerly supposed. They find that by the influence of 
substituting for a hydroxi group united to the mercury by iodine, 
or cyanogen, the power is decreased, while a mercury atom united 
A\ith both of its valencies to the benzene nucleus has no germicidal 
power. Obviously, mercurial soaps should not be used popularly 
or indiscriminately. We can conclude that with regard to metallic 
soaps, as it is known that a metal in the form of oleate is readily 
absorbed by the skin, if an internal effect is wished for, an oleate 
soap will succeed ; but if a local antiseptic or disinfectant action be 
required, oleates or other insoluble salts are practically useless, and 
means must be taken to obtain a mixture like the mercuric iodide 
soap or the zinc soap mentioned above, which yields the metal in a 
soluble form to water. The latter use of soap is obviously the 
natural one, the former more properly belonging to an ointment or 
liniment. 

In a series of bacterial tests in our laboratory comparison was 
made with a curd soap containing 32 o per cent, of water and GO -8 
per cent, of fatty anhydrides, using for the experiments a 2 per 
cent, sterilized solution. Inoculation with active bouillon cultures 
gave results which may be summarized in the tables, + indicating 
growth and - sterility : 

I. — Bacillus Coli Communis in Vigorous Growth. 





Curd 
Soap. 


A Scented 
Curd 
Soap. 


Carbolic 

10 
per Cent. 


New Disinfectants. 


BgL, 


Forma- 
lin 


Time. 


A. 


B. 


'Spcr 
Cent. 


0-4 per 

Cent. 


5 minutes . . 








• 


_ 


+ 


15 










- 


4- 


25 „ . . 










- 


+ 


30 ., . . 


+ 


+ 


+ 


+ + 


- 


- 


] hour 


+ 


+ 


+ 


+ ! + 


- 


•- 


U hours 


+ 


+ 


+ 


+ 


+ 




2i „ 
3i „ 


+ 
+ 


+ 
+ 


- 


+ 
-t- 


+ 
( Much 1 
\ attenuated / 






4 


" 


~ 


" 


■ 









1 J. Soc. Chem. Ind., 1910, 1328. 



PERSONAL AND INTERNAL DISINFECTION 
II. — Staphylococcus Pyogenes Aureus. 



117 



Time. 


Curd 
Soap. 


Scented 
Curd. 


,, , ,. New Disinfectants. 
Carbolic •' 

10 

per Cent. 

1 ^- "" 


Ugh 

3 per 
Cent. 


Forimi- 

lin 
0-4 per 
Cent. 


10 minutes . . + + 

20 „ .. + + 

:w ., .. + 

Between 1 \ 
and 4 hours / ~ 


- ! + 
, + 


+ 

Attenuated 


_ 


+ 

+ 



The relative amounts of disinfectants present in the solutions of 
the same strength (2 per cent. ) would be : 

Carbolic acid 2 per cent., or 1 in 500 of phenol. 

A 00') per cent., or 1 in 1,663 of disinfectant. 

B 0-03 per cent., or 1 in 3,332 of disinfectant. 

Hgl,, 05 per cent., or 1 in 2.000 of Hgl.,. 

Formalin 0-008 per cent., or 1 in 12,500 of formaldehyde. 

It will be seen that in these experiments the formaldehyde was 
used in unduly small quantity, but the results are good. Para- 
formaldehyde and lime-water added to a soap just before solidifica- 
tion is the basis of a patent.^ 

Carbolic and Cresylic Soaps. — -An ordinarily stated commercial 
strength of these soaps is 10 per cent., but it is frequently much less. 
The odour of all forms is very pronounced, and often constitutes an 
objection. Several varieties are advertised as "of delicate odour " 
and " not unpleasant in any boudoir," etc. ; but, although the homo- 
logues of cresol have a higher disinfectant power than phenol, they 
will still, if in effective proportion, manifest their distinctive odour, 
so that a soap of the tar order, however disguised with eucalyptus, 
gaultheria, or other scents — which in themselves, however, have 
little disinfectant value — -cannot be free from a more or less tarry 
Of lour. A large number of " toilet " soaps are advertised in con- 
junction with the names of various disinfectants, and contain such 
an infinitesimal quantity of the various reagents as to be quite 
useless in a germicidal sense; they are, in fact, objectionable, as 
conveying the feeling of a fallacious immunity.- "" Carbo-sapol " 
contains 50 per cent, of Calvert's No. 5 carbolic acid, 25 per cent 
yellow soap, and 25 per cent, soft black soap. 

^ J. Sac. Chem. Ind.. 190S, 138. 

- The percentage of ph'uoloids should alway.s be stated on tlic packages of 
these soaps. 



IS 



DISINFECTION AND STERILIZATION 



Professor Mikulicz, of Breslau, uses a spirit soft soap for disin- 
fection of the liands. This owes its eflficac}' mainty to the alcohol, 
as the alkalinity of the soft soap in solution is not high. A liquid 
ethereal antiseptic soap for this purpose is now manufactured in 
America, and is also employed as a parasitic dressing. 

Essential Oils. — The disinfectant power of the essential oils has 
been much over-rated, and to be at all effective they require to be 
used in such quantities as are liable to cause serious irritation to the 
skin, many of them having a blistering action as powerful as turi^en- 
tine or mustard. When desired as perfumes, the amount added 
should be minute, an over-strength having caused many soaps, 
otherwise well manufactured, to lose favour. When such ingre- 
dients are added to the crutching-pan, it is always desirable to 
neutralize the free alkali at this stage by the ammonium-salt 
process, or to postpone the addition of the oils until after the 
operation of fitting. Such has been the reaction against perfumes 
that prominent brands are advertised as " unscented," and others 
as " delicately scented." 

Volatile disinfectants, such as phenol, camphor, thymol, etc., 
suffer considerable loss if introduced in crutching in the ordinarj'- 
manner or added during remelting, so that the quantity present 
becomes uncertain ; it seems, in fact, desirable that all such medicinal 
soaps should be milled or plotted, as the machines are very con- 
venient for regulating the amount of disinfectant added. 

The cakes should evidently be packed in tinfoil (except in the 
case of mercury soaps, when oiled paper or thin gutta-percha should 
be used), and should be kept in a cool place. It has been proposed 
to coat the surface of the tablet with a film of gelatine or wax. 

In a series of comparative experiments made in 1806, using 
2 per cent, solutions and broth cultures at 37° C. of two representa- 
tive organisms with the usual precautions, one of us found that oil 
of cloves when present in a soap had little antiseptic action. 





Time required to Kill the Organism. 


Organism. 




Carbolic 


Clove Oil 


Clove Oil Biniodide 


Biniodide 


Curd 


Soap, 


Soap, 


Soap, Soap, 


Soap, 




Soap. 


3 Pounds 


3 Po^inds 


7*5 Pounds 0-5 


1-0 






per Cwt. 


per Cwt. 


per Cwt. i per Cent. 


per Cent. 


R. coli commu- 


lietween 


Between 2 


Alive after 


Between 


Less 


Less 


11 is 


2 and 4 


and 4 


hours 


2 and 4 


than 15 


than 15 




hours 


hours 




hours ' minutes. 


minutes . 


S. 'pyogenes au- 


Organi.sin alive after (i hours Between 


Under 15 


reus 


15 and 20 
minutes 


minutes 



PERSONAL AND INTERNAL DISINFECTION 



110 



The carbolic and two clove-oil soaps have therefore an antiseptic 
action equal to, but not exceeding, ordinary curd soap. In the case 
of S. pyogenes aureus, the limit of time required to produce disin- 
fection was not reached, but as both the strength and the time much 
exceeded those which obtain in j^ractice, it was not considered 
necessary to prolong the experiments. The time had also much 
exceeded that required by the biniodide. 

A comparison of the amount of antiseptic present in the case of 
the carbolic and mercurial soaps would point to the a 'priori proba- 
bility of the above results, since — 

The 2 per cent, solution of carbolic soap contained 0-052 

per cent, phenol. 
The 2 per cent, solution of mercurial soaps contained 0-01 

and 002 per cent, of mercuric iodide respectively. 

Solutions of 1 in 10,000 and I in 5,000 of mercuric iodide are 
kno^\^l to possess decided antiseptic properties, but a solution of 
1 in 2,000 of carbolic acid is practically useless. 

Another series of experiments with B. coli communis and 2 per 
cent, solutions gave : 



Sterile between 1 and 3 hours. 

Alive after 3 hours. 

Sterile between \ and 1 hour. 



Alive after 3 hours. 



Curd soap 

Zinc hydrate soap [ante, p. 114) 

Carbolic soap 

Coal-tar soap 

Sanitas soap 

Terebene soap . . . . . . ?? •? ?; 

The variation in these results is influenced by the amount of 
water present. Thus, taking a dry curd soap, such as was used in 
the above experiments, in proportion corresponding to soaps con- 
taining 33 and 66 per cent, of water, the following results were 
obtained : 



Time required to 
B. coli communis 



kill 



3 per Cent. 
Dry Soap. 



Attenuated after 
1 hour 



3 per Cent, of 3 per Cent, of 

Soap containing | Soap containing 

33 per Cent, of ! 66 per Cent, of 

Water. ! Water. 



Less than 
3 hours 



3 hours 



Soaps containing active oxygen are made witli perborates and 
percarbonates.^ 

Ointments.— With the exception of vaseline, Avhich in itself is 
certainly somewhat antiseptic, and to a certain extent the prc- 
1 Wolpenstein, J. Soc. Chem. Ind., 1908, 1028. 



120 DISINFECTION AND STERILIZATION 

parations of glycerine such as " glycerinum saponatuni," the bases 
of ointments are only antiseptic in the sense that they exclude air 
and moulds and bacteria from the surface covered. Other^vise their 
virtues are simjily emollient, or dejiend on the drug, such as mer- 
cury or zinc, which is incorporated with them. 

Sulpholeate of sodium has been sugested for dissolving anti- 
septic drugs and jdelding them to the skin.^ 

Lanoline and cold cream contain water, and thus differ from 
other ointment bases. If, therefore, antiseptics are incorporated 
with them they dissolve in the water, and so come in contact with 
the surface of the wound and kill the organisms present. When oil, 
vaseline, etc., are used, as they contain no water, the antiseptic 
remains in the ointment, and only a fraction reaches the surface of 
the patient, hence the uselessness of carbolized oil as' shown by 
Koch and Breslauer. The property of formaldehyde to form con- 
densation products with fat and oils has led to its use for the pre- 
paration of antiseptic oils. Lanoform, for example, is wool fat 
heated with formaldehyde. 

Mouth Washes and Tooth Powders. — ^These are too numerous to 
be fully discussed. They are chiefly empirical mixtures which owe 
their reputation to custom or advertisement. Some people use 
only water with a little soap in it to clean the teeth, but it is of 
advantage to assist the friction with a powder, and also to use an 
antiseptic which will penetrate the crevices which cannot be reached 
by the brush. Wood-charcoal powder is excellent, but rather dis- 
agreeable. The best is said to be areca nut; it should not be used 
constantly, as it is apt to scratch and wear away the enamel. 
Prepared chalk is the best foundation for tooth jwwders, as it 
neutralizes any acid, and, being softer than the enamel, it polishes 
but does not scratch. Powdered myrrh, Peruvian bark, quinine, 
and other ingredients are frequently added. Honey, borax, various 
scents, such as orris and rose, are among other substances which are 
commonly found in dentifrices. As a mouth wash, where there is 
decay and the breath is offensive, one of the best applications is 
chlorinated soda diluted to about 1 per cent., and used occasionally. 
It is not very pleasant, but it removes all odour. Saccharin, sodium 
bicarbonate, oil of peppermint, benzoic and boric acids, tannin, 
tincture of iodine (dangerous), and tincture of myrrh are also 
occasionally met with. 

Cleansing Personal Utensils. — The regular washing and cleansing 
of private articles such as brushes, combs, and razors should always 
be insisted upon. Baibers should pass their instruments through 
some disinfectant such as 1 in 1,000 mercury sublimate or its equiva- 

1 Therap. Oaz., 1801. 



PERSONAL AND INTERNAL DISINFECTION 121 

lent in phenoloid disinfectant. For regular clients special sets of 
instruments might be kept under hygienic conditions. 

The cleansing of utensils used for eating and drinking requires 
careful attention, especially in public eating-houses and hospitals. 
0. Roepke^ gives two authentic cases in which syphilis was trans- 
mitted by the use of a common drinking-glass in a beer-hall. 

The use of the chained cup in connection with the public drinking 
fountain cannot be condemned in too strong a measure. The 
replacement by j^aper cups obtained from automatic machines or 
drinking directly from a vertical fountain of water are substitutes 
which deserve attention. 

Munch advises disinfection of bath tubs (besides disinfection 
of the urine as systematically as of faeces) used by persons who 
have or have had typhoid fever recently. He suggests that mic- 
turition during the bath is of frequent occurrence in typhoid. 

Disinfection of Clothes. — The disinfection of clothes and fabrics 
is usually accomplished by means of a steam disinfector (see ante). 
If this is not available, the clothes may be boUed with a germicidal 
solution of determined strength ; this method, however, is generally 
more costly and more liable to injure clothes. 

Disinfection of Cavities of the Body. — Several methods in use 
have been alluded to in the chemical section. The following is a 
summary of processes : 

(a) Washing out by inflow and outflow tubes with lukewarm 
water, then with a weak solution of an antiseptic, which should not 
be one with a stronglj^ poisonous action on the system. Phenol, 
resorctnol, and mercuric chloride have been absorbed with dangerous, 
and even fatal, effects. Iodine is very irritant. lodol has been 
recommended, Iflcewise betol and phenyl-propionic acid.^ Salicylic 
acid is dangerous, irritant, and not effective. A solution of silver 
nitrate in distilled water has been tried with great success; the 
objection to it is that if weak (1 in 1,000) it is almost wholly precipi- 
tated by the chloride of sodium in the fluids of the body, and if 
stronger (1 in 200) it has on some occasions caused sloughing. 
Silver preparations free from these faults have been described. 
(p. 88). Sulphocarbolate of zinc, 1 in 1,000, has the advantage of 
being mildly astringent, and seems to be safe; a sulphocresylate 
would probably be still safer, and is a stronger antiseptic. Aluminol 
(p. 254) is a useful and powerful astringent. Glycerine is irritant 
to mucous membranes, but it is useful when it is necessary to keep 
surfaces moist. On boric solutions, see p. 49. A number of the 

1 Deutsch. Med. Wochensch., 1905, 31. 

^ Klein, in Stevenson and Murphy's " Hygiene," p. 2(il. 



122 DISINFECTION AND STERILIZATION 

newer antiseptics are advocated for tliis special branch of antisepsis, 
but they await more extended and impartial surgical tr*als, as many 
of the earlier statements have not been verified by recent experi- 
ments. 

(&) Spraying. — ^Any of the former ma_\' bo used in the form of 
spraj^, the advantages being that stronger solutions may be used, 
that only the affected parts are treated, that the irritating and 
depressant action of large volumes of water are avoided, that a 
local refrigerant effect may with safety be produced, that much less 
of the medicament is required, and that the action can be watched, 
and the process repeated with facility and without shock. The 
various spray-producers nearly all act on the same principle; a 
current of air is blown by an india-rubber ball, Avith a second ball 
to render the blast steady, across the narrowed orifice of a vertical 
tube dipping into the liquid in the bottle. The strength and fine- 
ness of the sjDray are regulated by the relative size and position of 
the orifices, and the amount of liquid delivered is knoAvn by the 
graduations on the bottle. Chlorine water, with or without cocaine 
hydrochloride, has been employed, and boric sprays are frequently 
used for the throat. Solutions in ether were recommended by 
Philip Sterne as far back as 1767^ as antiseptic spray. As sprays 
said to more easily penetrate parts covered with hair, mercuric 
chloride, chrysarobin, resorcinol, and formaldehyde have all their 
special uses.- 

(c) Gargles of honey and borax, tannin, and alum have been used 
from time immemorial. This method is easily used by unskilled 
persons, but it is inferior to that of spray, as there is no certainty 
that the parts affected will be reached. It is evident that no drug 
which will be poisonous if swallowed can be employed. 

{(I) Injections of Gases or Vapours. — It is a familiar fact that if 
an abdominal cavity be wounded, septic poisoning and peritonitis 
is almost certain to supervene, and that washing out may be dan- 
gerous, owing to the intense irritation, and may even cause the 
above disastrous result. In these cases spraying is also interdicted. 
Life has frequently been saved by gaseous injections, and sulphur 
dioxide seems to be the best remedy to employ. This can be 
obtained by blowing a current of air through a tube containing 
some fragments of sulphur, and allowing the gas produced to enter 
the cavity. The part of the tube containing the sulphur is heated 
by a spirit lamp, taking care that the end of the tube is kept cool. 
Blowing air through a saturated solution of sulphurous acid or 
through a mixture of a sulphite with acid is inferior to the above, 
as the quantity delivered is uncertain. Liquefied sulphurous acid 
^ "Advice to the Consumptive." - Pharm. J.. ?1, 1040. 



PERSONAL AND INTERNAL DISINFECTION 123 

from a Boakes' bottle cannot be used for this purpose, as the cold 
produced is intense and would produce shock. Unfortunately sul- 
phurous acid, by being absorbed into the system, is recorded to 
have produced fatal effects in one or two cases. Baxter experi- 
mented specially on its effect on the virus of peritonitis^ with 
favourable results. Chlorine, bromine, and iodine vapours are 
irritant and dangerous. Many others, such as chloroform, ether, 
phenol, etc., are excluded by their narcotic action. Iodoform 
vapour has caused poisonous effects. Carbonic acid is very sooth- 
ing, and rapidly subdues inflammation, but for this purpose the gas 
must be thoroughly washed. It is only a feeble antiseptic, but 
would be a better medium for other antiseptics, such as eucatyptol, 
than air. 

(e) Inhalatio7is. — ^Chloride of ammonium is beneficial in l^ron- 
chitis and asthma. The simple breathing of the vapour of vinegar 
and hot water also gives relief. Koch proved that a number of 
essential oils Avhen inhaled with steam are inhibitory to tubercle.- 

Antiseptic Dressings usually include cotton-wool, wood-wool, or 
gauze, which act as germ excluders; they are kept moist with diluted 
soda chlorinata (p. 200), or Avith boric acid solution (p. 204); some- 
times phenol, 2|per cent., or mercuric chloride, 1 in 1,000, are used, 
but they are liable to produce ill effects on absorption. There is a 
great advantage in changing the agent every few days; even the 
most innocuous are liable to become irritating if continuously used. 
An alcoholic solution of coal tar has been much used for many years 
under the name of Wright's Liquor Carbonis Detergens. Diluted 
cresol and Sanitas fluid are useful in rotation with boric and with 
chlorinated lotions. CTlycerine is objectionable. Zinc sulphocar- 
bolate and sozal (the aluminium salt) are used as astringent and 
antiseptic lotions. Diaphtherin in 1 per cent, solution has been 
much used in Germany. Tichborne recommends^ zinc sulj^hite as 
non-poisonous and not irritating. 

Gauzes and Wools are described under iodoform, boric and sali- 
cylic acids, and zinc-mercuric cyanide. Hydronaphthol gauze has 
recently been much praised. Salicylic gauze is irritating. Thymol 
or eucalyptus gauze would seem to be the best and safest. Ben- 
zoated gauze, 5 per cent., has also been recommended. 

M. Duquaire, of Lyons, has invented an ingenious antiseptic 
paper. The material is asbestos, with about 5 per cent, of ordinary 
paper pulp, worked into soft paper and soaked in a petroleum- 
benzene solution of beeswax. The solvent having been evaporated 

^ Appendix to the Report of Med. Off. of the Privy Council, 1875. 

2 ^Marshall Ward. .7. Soc. Chrm. hid., 1893, 943. 

3 Brit. Med. J., 1890, 1064. 



124 DISINFECTION AND STERILIZATION 

off in the open air, the tissue is ready for use. When required it is 
set on fire, and is so made aseptic, and may be employed at once 
for dressing wounds. ^ 

Unfortunate!}' many of the antiseptic avooIs and dressings met 
with commercially are of uncertain composition, and insufficient 
attention has hitherto been paid to the importance of storing these 
articles in such a way that the anti.septic present shall not be 
volatilized. 

In France their sale, except by duly qualified pharmacists, is 
forbidden, but the question does not seem to have been discussed in 
England. 

Surgical instruments must be rinsed in a disinfectant which does 
not corrode steel ; the various cresol preparations are much used for 
this purpose. Those that turn turbid wath water have the dis- 
advantage that the instruments cannot be so well seen. A good 
preparation seems to be potassio-mercuric iodide, 1 in 4,000, 
or two of the soloids to a pint, for hands or instruments. 

Antiseptic Hypodermic Injections. — ^Several of these have been 
much employed recently in France, particularly for phthisis; the 
basis is olive oil, and all the ingredients are carefully sterilized by 
heating to 120° C. 

Picot uses guaiacol 5, iodoform 1, olive oil to 100; Morel- 
Lavallees' solution consists of eucalyptol 12, guaiacol 5, iodoform 4, 
olive oil to 100. 

Also solutions in olive oil of creosote 1 in 15, and eucalyptol 2 
to 4 in 10 have been suggested.^ 

A number of mercurial compounds are used specially in syphilitic 
affections. These are later enumerated and described. 

Internal Disinfection. — In the alimentary canal, and sometimes 
in other parts of the body, there are always present large numbers 
of micro-organisms, and it is probable that the process of digestion 
itself may be assisted by certain microbes. Even pathogenic bacilli 
may enter in limited numbers without producing disease. They 
are not destroyed by the gastric Juice, but rarely survive in the 
struggle for existence with the far more numerous non-disease-pro- 
ducing organisms. If they are present largely in food, Avater, or air, 
it is impossible to exclude them from the body, and difficult to kill 
them when they have entered. 

The removal of bacteria may, however, be brought about in 

hastening their elimination l)y ])urgatives, or by entangling them 

and their products by inert substances like wood-charcoal, which 

is known to have proved most beneficial in indigestion and flatu- 

1 Chem. and Dnuj.. 1890, 39. 2 Tfierap. Qaz., 1891. 



PERSONAL AND INTERNAL DISINFECTION 125 

lency — states which are probabl}^ due to, or at least intensified by, 
organisms promoting abnormal fermentations. 

It had been hoped that oxidizing agents like chlorinated soda, 
peroxide of hydrogen, potassium permanganate, and even potas- 
sium chlorate, would be capable of attacking bacteria in the alimen- 
tary canal. But the last mentioned passes right through the 
system into the urine without change, while the others not only 
disturb digestion, but are rapidly used up by the easily oxidizable 
organic matters present — i.e., they act on the food before affecting 
the far more stable bacteria. Much was expected from hydrogen 
peroxide, but results have been disappointing. Dilute chlorine 
water is said to have been given internally with great benefit in 
enteric fever, especially when the stools Avere offensive. ^ 

Sulphuretted hydrogen \\'ater and sulphites were formerly given 
with the object of destroying organisms. They are unpleasant, 
disturb digestion, and do not seem to bring about the desired 
effect. 

Internal Antisepsis. — Although it is difficult to kill the bacteria 
A\ithin the alimentary canal, it is quite feasible to hinder their growth 
by an inhibitory or antiseptic treatment, and so at the same time 
to lessen the auto-intoxication produced. If the contents of the 
stomach were undergoing fermentation by the action of yeast, etc., 
it would be quite possible to stop the process by means of i3henol, 
creosote, or an essential oil, with a dose so small as not to injure 
the coats of the stomach. But the same dose w^ould also stop or 
at least impede salivary, pancreatic, and gastric digestions. There- 
fore these powerful agents, though occasionally given in capsules, 
are not in general favour. It has been suggested that the use of 
condiments such as salt, vinegar, pepper, mustard, and spices is 
really an instinct founded on their antiseptic action, since many 
animals resemble man in this respect. The effect of mineral waters, 
too, dej)ends in a large measure on the antiseptic action of carbonic 
acid, and not on the alkali, since soda-water generall}^ does not 
contain soda in any efficient Cjuantity. 

It has been- already pointed out that acids are antagonistic to 
most bacteria. Dilute sulphuric acid has been preferred in man}- 
diseases, especially cholera, on account of the additional advantage 
of its astringent action. Sulphuric lemonade, made by the addi- 
tion of the acid, which should be i^erfectly pure, to sweetened and 
sterilized water in quantities sufficient to give a marked but 
pleasant acidulous flavour, may be emploj^ed freely, and according 
to all experience with much benefit. Excellent effects have been 
attributed to the habitual and free supply of a pleasant flavoured 
1 " Local Gov. Officer, " l'JU7, 80. 



126 DISINFECTION AND STERILIZATION 

sulphuric orangeade among the employes of the post office during 
several cholera seasons. It is cheap and innocuous, and is very 
likely to do much good. Although ordinary lemonade contains 
citric acid, it is more costly, and is inferior to sulphuric for this 
special purpose. 

The Vienna mixture for choleraic diarrhoea consists of 15 dro])s 
of aromatic sulphuric acid (sulj^huric acid 1 in 12, with rectified 
spirit, cinnamon, and gmger) to 1 ounce of sweetened water; to 
this is often added, under medical advice, 5 or 10 drops of ether and 
5 drops of laudanum. The mixture has been much used and highly 
thought of in Austria, Germany, and France, and by the English 
Local Government Board. 

For intestinal antisepsis neither phenol nor creosote can be 
employed, being too poisonous and irritating. Betol, however, 
has been successfully used, the /i-naphthol produced by its 
decomposition being comparatively non-injurious. Resorcinol, 
guaiacol, thymol, and sodium benzoate are sometimes used as 
internal antiseptics, and in cases of colitis have proved their effi- 
cacy by deodorizing the bowel discharges. Sodium sulphocarbo- 
late is also much used. The action of calomel in cases of duodenal 
indigestion seems to be bactericidal. 

Quinine and its source, cinchona bark, probably owe a great 
deal of their power in fevers to their antiseptic action. 

Several of the derivatives of guaiacol, such as benzosol, have 
been highly recommended. Pheno-salyl is a good preparation 
for washing out the bladder and urethra.^ Urotropine as a pro- 
phylactic agamst typhoid fever owes its efficacy to the generation 
of formaldehyde. 

Vaccination. — Vaccination and other preventive measures of 
inoculation are as yet foreign to the scope of tlie present work, 
but may properly be regarded as precautionary measures relating 
to j)ersonal dismfection. 

There is little doubt that chemico-disinfection plays an impor- 
tant part in the general problem of disinfection in the blood-serum, 
as we shall note when dealing with the work of Ehrlich on chemical 
spirilla and trypanosomicides, but the other important factors, such 
as removal of bacteria by means of the phagocytes, are, however, 
not as yet directly translatable into phenomenological chemical 
language. The reactions in the blood-stream caused by the adven- 
titious ingress of foreign organisms are relatively complex. One 
drop of blood contains approximately 5,000,000 red corpuscles and 
2,000 white cells or phagocytes floating in the blood-plasma. On 

' On iritostiiial autiHciitics v. Burncy Yeo, Brit. Med. J., 1899, 1250; Vaughaii 
llarloy aud Guodbody, ibid., 1890, 1254. 



PERSONAL AND INTERNAL DISINFECTION 127 

the infiltration of the foreign organisms, bacterial or protozoal, both 
the phagocytes and the bloocl-plasma attack and digest them. It is 
estimated that one phagocyte can deal with from ten to twenty 
microbes before it is poisoned by the toxins secreted by its food. 
The ordinary process of physico-chemical actions is, however, 
more perceptible in the action of the blood-plasma. From the 
blood-plasma a series of substances termed antibodies (see Chap- 
ter XL) have been isolated; these react in different manners with 
the micro-organism. Antibodies include antitoxins, which react 
specifically with the toxins of the micro-organisms; agglutin, which 
agglutinate or cause dumpings of the bacteria; substances which 
exert a direct solvent action on the germs, and appear to render 
them more easily absorbed by the phagocytes. Poisoning of the 
blood-stream may be caused by an accumulation of dead phagocytes 
and spent plasma, by the secretion of "aggressions "which paralyze 
the phagocy tical activity, or by the accumulation of bacterial toxins ; 
whilst preventive and curative measures constitute either the 
injection of dead germs so as to stimulate the production of anti- 
toxins in the plasma, a procedure frequently followed in typhoid, 
or the injection of a serum containing the antitoxin, as in tetanus 
and diphtheria. 

The Disinfection of Wounds. 

The disinfection of wounds during the European conflict has 
presented difficulties much graver than in any previous period, and 
greatly differs from earlier exj^erience. Most modern surgery has 
relied on excluding dangerous organisms and encouraging natural 
processes of repair, but such favourable circumstances could 
very seldom be reached. ^ It was found that all wounds in this war 
were already septic when ordinarily received, on account of the 
length of time before the patient is treated. The wounded often 
could not be picked up, sometimes for twenty-four or forty-eight 
hours, and the chances of rendering a wound aseptic are small after 
twenty-four hours, and nil after forty-eight. Wounds are rapidly 
infected with organisms. Many of these divide and double their 
numbers in twenty minutes, so that each organism could give rise 
to 15, 000, (JOG in twelve hours. Fii'st aid cannot often be given, so 
that the pathogenic bacteria have a long time to develop, and these 
are of the dangerous kinds derived from manured fields and from 

1 M. Tuflier {Paris Acad, de Medecine), sent by the Minister of War to inspect 
treatment of wounded, recognized that the superiority of antisej^tie over asei)tic 
treatment was incontestable. " French first aid api^lies tincture of iodine to the 
wound; this, with bandaging, is often sufllcicnt for healing simple wounds. Tetanus 
is frequent. For emphysematous gangrene they inject peroxide of hydrogen." 



128 DISINFECTION AND STERILIZATION 

populous districts. Their earliest treatment is in the " clearing 
hospitals," mobile units placed as near as possible to the field 
ambulances. In actual practice this generally means an interval 
of twelve hours, with " as many as 500 to 1,000 patients received 
in twenty-four hours, their clothes all thick with mud.""^ 

The stores of dressing and bandages recjuired were greater than 
in any previous war. In the usual procedure the skin was painted 
with iodine, the wound washed with a carbolic antiseptic and 
dressed. Every man was injected with antitetanic serum, and in 
reference to the pressure it is mentioned that in one place "after 
using 30,000 doses of tetanus antitoxin they ran tem^Doraril}^ short. " 
Besides this, other injections were in use, and the British Medical 
Association Research Committee's Section of Bacteriology, headed 
by Sir Almroth Wright and Captain Douglas,- furnished the 
Admiralty, War Office, and French and Belgian Armies with over 
350,000 doses of antisepsis vaccine. 

The soldier's greatest foe after battle is putrescence of wounds. 
An early record of this is that after Phalsbourg, in 1795, " wounds 
became so offensive as to cause nausea to those near, and to occa- 
sion the poor fellows to be deserted." Bullets themselves and other 
weapons of war are usually more or less aseptic, and do not infect 
the wound unless clothing or other matters obtain entrance with 
them. It is common experience that bullets pass through, leaving 
inconsiderable effects beyond slight local sepsis in some cases. 

Professor Aschoff noted that German projectiles as a rule caused 
greater damage than French, as the former, when striking, break 
up and expose the leaden core.^ Apart from mechanical injury, 
however, the serious infections arc not metallic, but bacterial, and 
supervene after the wounded have lain on the ground. 

In the earlier stages of the war suppurating wounds occurred m 
60 per cent, of the wounded prisoners in Belgium, which was rashly 
taken to show that " the German field dressing was not a very 
efficient preventive against sepsis."* Tetanus was very rife, and 
antitetanic serum was extensively used. Later information proved 
that tetanic infection from the soil affected the armies of the Allies 
and Germany with equal seveiity. It was noticed that tincture of 
iodine used in these wounds rendered innocuous the specific 
organisms, or at any rate made their action take a mild form. 

Bacteriological investigations showed that the prevalent causes 

1 8ir A. Bowlby, Jiril. Med. J., December 19, 1914. 

- They have departments in London at the Mount \'enion Hospital, Hamp- 
stead, and at St. Mary's Hospital, i'addington, for bacteriological investigation of 
infected wounds. 

^ Feldarzlicho Beilago, Miinch. Med. Wochenschr., No. 6. 

* Lancet, September 12, 1914, 721. 



PERSONAL AND INTERNAL DISINFECTION 120 

of mortality were a group of spore-bearing anaerobic bacteria, of 
which over ten distinct varieties have been isolated ; hence oxidizing 
agents were indicated as antagonistic to their mode of growth. 
Among generally used oxidizers has been — 

Peroxide of Hydrogen, used extensively even before the war. 
At the beginning Captain Max. Page, R.A.M.S., found that emphyse- 
mataceous gangrene could be treated successfully by local incision 
and the application of hydrogen peroxide.^ A Royal Naval report 
in October, 1914, stated that " wounds are grimed with dirt, oil, 
dust, and pieces of clothing. For suppurating wounds we found 
peroxide of hydrogen our sheet anchor in 10 or 20 per cent, solution." 
Colonel Makins, Surgeon to the Forces, says that in all cases per- 
oxide of hydrogen has been applied locally to the wound. In 
French field hospitals, when wounds have been soiled by contact 
with earth or filthy straw, a protective inoculation of antitetanic 
serum was the regulation treatment; it must he given at once to have 
any ejfect. For gangrene, injections of hydrogen peroxide were 
used. " Unfortunately they are very painful, as for preservation 
the solution is always acid." This refers to a disadvantage of 
H.2O.2, its instability. To minimize the rate of decomposition 
during storage and transit it is customary to add a stabilizing agent 
such as tannic or phosphoric acid. The commercial description 
of 10 or 20 volumes means conventionally the number of 
volumes of oxygen gas that the solution gives off when treated 
with peroxide of manganese. "Perhydrol" is a solution of 
100 volumes strength or containing 30 per cent, by weight of 
HoOo. But although increasing the strength diminishes the 
weight and bulk of transport, it is not generally advisable, as it 
increases the expense in greater proportion, and does not render 
the preparation more stable, therefore the 10 or 20 volume solution 
is the common supply. Some failures have undoubtedly been due 
to the reagent having become weaker by keeping, therefore sub- 
stitutes have been introduced in the form of soluble solid metallic 
peroxides which can be easily carried and used in definite strength. 
The choice of the base was hmited. Peroxides of sodium and 
potassium are caustic, those of barium and strontium are poisonous ; 
magnesium peroxide has proved very useful, but it is expensive. A 
preparation called " perhydrit " or " h3^erol " is mentioned as a 
compound of H2O.3 and urea, with a trace of citric acid to render it 
stable. Sodium perborate is neutral, and is strongly advocated 
as an oxidizer in some French hospitals. 

For emergency dressings viofonn (hydroxyquinoline chloro- 

1 TMnrd, August 8, 1014. 



130 DISINFECTION AND STERILIZATION 

iodide, [CgH^jS! (0H)1C1]J gauze was employed by the Germans. Only 
3 out of 400 showed suppuration in an ambulance train after this 
treatment. For anaerobic infection HoOo was recommended, 
" especially in the solid form, Avhich can be powdered on the wounds 
like iodoform ; the perhydrit of Merck and the pergenol of Byk have 
proved convenient forms." Ever^-^vhere tetanus caused high mor- 
tality, and there is unanimity as to the benefit of antitetanic serum . 
Von Behring says that 20 c.c. was generally sufficient for preventive 
treatment, whereas after spasm has occurred at least 100 c.c. should 
be given intravenously. More potency is ascribed to luminal, a 
phenyl-veronal derivative (Baj-er). " At the Hamburg Naval 
Hospital they had great success with combined antitoxin and 
salvarsan." 

Salvarsan must not be exposed to the air, as oxidation and forma- 
tion of AsgOg results, and thus requires greater care in administra 
tion than can be given in the field. 

Hypochlorites have been tried in the European war as oxidizers 
against anaerobes, and would be good and cheajD agents except for 
a quality converse to that of hydrogen peroxide solutions — that they 
are alkaline, and equally produce a certain amount of irritation. 
Dr. Chavasse, Inspector-General of the French Medical Service, 
recommended that " every wound and its surroundings should be 
painted once with 1 per cent, tincture of iodine. The tendency, 
especially among amateur nurses, to change dressings when they 
appear to be soiled should be strongly repressed (on account of 
injury through disturbance, and the danger of introducing fresh 
infection)." He also advocated moistening the dressings with 
dilute chlorinated soda. M. Hartmann stated at the Academic de 
Medecine that in his experience tincture of iodine was only useful 
when used at once; after twenty-four hours he applied hydrogen 
peroxide or strong solution of carbolic ; chlorinated soda gave good 
results. Musgrave Woodman, of the British R.A.M.C, says that 
"iodine in this war has, in my experience, failed; strong antiseptics 
are clearly indicated." The moral of these apparently discrepant 
observations is that each of these applications can do good in a 
great number of cases, but fail when the infection has had a long 
time to develop. 

A later report of the results obtained in thirty-nine cases 
of tetanus^ gives the mortality as Tl'S per cent. ; the treatment was 
2 per cent, carbolic and antitetanic scrum. Hartmann says that 
this serum saved in all cases at Besangon. In British field hospitals 
tetanus, both from bullets and shells, was treated by injections of 

1 Brit. Med. ■/.. .Tamiarv 2, lOlf), 45. 



PERSONAL AND INTERNAL DISINFECTION 131 

carbolic, antitoxin, and magnesium sulphate, but '"acute cases were 
almost always fatal whatever the treatment."^ 

Permanganate still keeps its position as a powerful and portable 
oxidizer definite in strength. Lieutenant-Colonel Rogers, from long 
experience in India, found permanganate of great value for slough- 
ing and tetanus-infected wounds against tetanus and gas-forming 
anaerobes, and that potassium permanganate solution of 1 to 4 per 
cent, cleans and heals more rapidly than 10 -per cent, peroxide of 
hydrogen. 

The disadvantages accompanying the use of the majority of 
germicides of the " peroxide " type is that their penetrative action 
is very feeble, and that the oxygen liberation. Avhen brought into 
contact with the blood-serum of the wound, is liable to be rather 
violent, causing both pain and fugacity in germicidal activity. 

Whatever may be the nature and gravity of wounds, they all 
alike become almost incurable if accompanied by tetanus. Tetanus 
toxin appears to be the most poisonous substance at present known. 
Lambert computes its fatal dose to be 0-23 milligramme (0-0035 
grain), whereas that of cobra venom is 4-38 milligrammes (Cal- 
mette), strychnine 30 to 100 milligrammes, and anhydrous prussic 
acid 54 milligrammes. Fortunately there are several agencies that 
can render it inert. It is destroyed by an exposure to 60° C. for 
twenty minutes, or to 65° C. for five minutes, and is attenuated by 
exposure to light and air at ordinary temperature. It is not harmed 
by 0-5 per cent, carbolic acid, but is destroyed by iodine trichloride, 
by peroxide of hydrogen, and by potassium permanganate. Its 
important constituent is called tetanospasmin. 

ExjDeriments have sho^A^l that if tetanus spores are thoroughly 
washed, so as completely to deprive them of their toxins, they can 
be injected with impunity into a susceptible animal, as the phago- 
cytes can then destroy the toxin-free organisms. The destruction 
of the toxins by an oxidizer has a similar effect, and the action also 
extends to other organisms of the class. Injection of oxygen gas 
by Bayeux's instrument, which measures the amount and regulates 
the rate, was found effective in cases of septic fractures.- 

Injections of magnesium sulphate are based on the investiga- 
tions of Meltzer and Auer with animals, and its use on patients in 
this war has been found successful in banishing pain and inducing 
sleep. The dose is usually i gramme in 10 per cent, solution. 

Another bacillary disease with about the same fatalit}- as 
tetanus, and primarily caused by a gas-forming anaerobic organism, 
is gangrenous cellulitis, or gas gangrene, which has attacked about 

1 Brit. Med. J., Bpcombor 19. 1!»14, 105.'?. 
- Ibid., December 12, 1914, 1021. 



132 DISINFECTION AND STERILIZATION 

I per cent, of the recent wounds of all the armies. Much work on 
the cultivation of this anaerobic organism was done by Mr. Row- 
lands and Sir Almroth Wright. In the hospital cases oedema 
rapidly increases with bubbles of gas, the limbs becoming black; 
there is generally a mixture with stre})tococcus infection, and often 
the anaerobic organism dies out and only streptococcus cultivations 
can be obtained from the wounds. Active hsemolytic change is 
shown by straining of limbs, also by the brilliant orange tint of 
serous exudations. Benefit has been claimed from the method of 
injecting peroxide of hj'drogen, though Sir Henrj^ Makins did not 
support this view. So that here antiseptics are required as well as 
simple oxidants. Commonly associated with the microbes of 
tetanus and gangrene are other pathogenic species, some not 
anaerobic, such as B. aerogenes capsulatus (Welch's bacillus), B. per- 
fringens, and B. enteritidis sporogenes ; their spores are liable to be 
present in large numbers in dust and mud. The projectile or other 
weapon may have been more or less antiseptic, but the wound 
becomes rapidly invaded by pathogenic microbes either from the 
earth or from the skin itself. Swabbing with powerful agents like 
iodine tincture or liquefied carbolic acid^ secures superficial asepsis, 
but does not reach the organisms when they have had time to 
colonize within the wound. Therefore the great need that applica- 
tions should be immediate, and this is only possible when soldiers 
have themselves the remed}^ at hand. We shall recur to the point 
subsequently. 

Dr. Rowland's bacteriological work resulted in the isolation of 
the specific bacillus of gas gangrene; a culture injected into a 
guinea-pig caused death in eighteen hours with gangrenous cellu- 
litis, from which the organism was recovered. It was first thought 
to be that of malignant oedema, but further examination at the 
Lister Institute by Martin and Arkwright made it out to be an 
allied species called the bacillus of Ghon and Sach. It appears that 
there are some ten different organisms that have been isolated from 
gas gangrene in man, all closely allied and all anaerobic spore-bearers. 
A sample of earth from a trench was examined. Shaken with water 
and the liquid inoculated into a guinea-pig, the latter died in eighteen 
hours with gangrenous cellulitis, and contained a spore-bearing 
anaerobe of the above grouj). There were the same symptoms of 
offensive odour, dark colour, and gas production. Gangrene is thus 
due to infection at the time of the Avound. For washing the wounds 
peroxide of hydrogen is one of the best antiseptics. The Lister 
Institute succeeded in preparing a suitable antitoxin. The group of 

^ See Sir Watson ChejTie's valuable review of the subject in his presidential 
address to the Royal College of Physicians, November, 1914. 



PERSONAL AND INTERNAL DISINFECTION 133 

anaerobes causing gangrene are spore-bearers, and the spores are 
especially difficult to kill by any antiseptic solution, or even hy 
boiling. Consequently, in order to sterilize infected instruments, 
etc., other measures are required: (a) autoclave at 120° C; (6) boil- 
ing one hour in 1/20 carbolic or 1/10 lysol. The last named, being 
made from cresol, has a stronger germicidal power than carbolic, 
and is similar to the British preparation, cresol soap solution (Liquor 
cresolis saponatus, B.P.C.), which can replace it with advantage. 
" Parabolic," used at the Netley Hospital, is another of the British 
equivalents to the German lysol. For field convenience, attention 
has been called to one of the earliest (it was described in the Edin- 
hurgh Med. J., 1890), and still about the simplest of portable ster- 
ilizers for dressing, etc., introduced many years ago by Surgeon 
Cathcart of the Edinburgh Infirmary. It is cubical in shape, and can 
be heated over gas or fire. Diagrams of its modern form are given 
in the Brit. Med. J. of December 19, 1914, 1056. 

For sterilizing the hands before and after operations the German 
Army used a soap containing 80 per cent, of alcohol, Avhich had been 
proved to kill staphylococci, streptococci, B. coli, and B. diphtherire 
in half a minute. The soldiers' wounds w^ere treated by irrigating 
with hydrogen peroxide, applying iodine tincture, and j^lugging with 
iodoform gauze. ^ Dr. Linkenheld fixes the tincture of iodine with 
a varnish composed of 1 part oil of turpentine with 50 parts each of 
colophony, resin, and ether;- these additions have a supplementary 
antiseptic power, but they tend to absorb the free iodine. For 
protective dressings " mastisol " is largely employed, made by Dr. 
Ottingen of Berlin ; mastic and other resins are dissolved in benzene 
with a small quantity of an ester. Cheaper is dammar dissolved 
in benzene. The resin lodges in the pores of the skin and prevents 
the passage of organisms. 

Some other curative agents for wounds have been used and 
advocated in our armies. Dr. A. Wilson states that salicylic acid 
is very successful.^ Dr. Stephens recommends sj^raying with petrol. 
Simpson and Hewlett show by their experiments that colloidal 
silver is an active germicide;* it would probably be suitable 
for wounds, and would have no irritant action. The germicidal 
power of soluble mercury compounds is well knoA\'n, but the 
commonest of them, mercuric chloride. " corrosive sublimate," has 
its irritant properties against it for the ])resent ])urpos(\ The late 
Sir Victor Horsley preferred sublimate lotion (1 of HgCl., in 1.000 of 
distilled water), using also hydrogen peroxide of 20 volume strengtli 

^ Feldarzliche Beilago, Munch. Med. WvcJiciischr., No. 1. - Ibid., No. (i. 

^ Brit. Med. J., December 5, 1914, 9D9. 
* Lancet, Decenibor 12, 1914, 1359. 



134 DISINFECTION AND STERILIZATION 

and petrol ''as a cleanser." Colonel Makins, in his already-men- 
tioned report of November 12, 1914, records that cures have followed 
under different conditions when wounds have been irrigated with 
hydrogen peroxide, painted freely with iodine tincture, dressed with 
carbolic, mercuric chloride, creolin. or lysol, and covered with mer- 
curic bicyanide gauze. Subcutaneous injections of 2 per cent, 
carbolic have been a favourite treatment in English and French 
hospitals. 

Sir A. Bowlby, in his letter to the Lancet of December 1!>. 
observes that the usual routine is to paint the skin far around with 
iodine tincture, and to wash the wound wth carbolic 1 in 20, iodine 
tincture diluted to half or a quarter strength, or strong hydrogen 
peroxide; dressings are always mercuric cyanide gauze and absor- 
bent wool. For the naval wounded at the Haslar Hospital, Surgeon 
Wildey states that he has been using with great success only two 
antiseptics ; the wounds were first cleaned with a solution containing 
1 in 1.000 of mercuric iodide (dissolved, of course, in about an equal 
weight of KI), and then treated with iodine tincture. He recom- 
mends an iodine sj^ray-producer with hook attachment fastened to 
the belt or coat for ambulance work in the field. 

R. Lambert/ as a result of a series of experiments with various 
germicides, including HgClg, KHglg, KCN, NaOCl, CgHgOH, tri- 
cresol, HgOg, C.2H5OH, and iodine, on living tissues infected Avith 
staphylococci, found that iodine was the only effective germicide, 
and did not injure the cells or tissues. 

We have seen that the pathogenic microbes with their toxins 
develop so raj)idly as to very often render cases beyond relief on 
arrival at field centres. It was important, therefore, for the soldier 
to carry carbolic or iodine, which could be packed into the wound 
at once, so as to stop growth of bacteria before the patient reached 
the base hospital. Surgeon Lenthall Cheatle, of the Haslar Royal 
Naval Hospital, mentions some other portable remedies. He soon 
learnt in the Boer War that '"wounds should receive disinfectant 
treatment as soon as possible after infliction. Lord Lister gave mo 
a powder of zinc merciu-y cyanide, but wind and rain made it im- 
practicable. Therefore I made the powder into a paste by mixing 
it with 1 in 20 carbolic dyed with J per cent, rosaline, and found it 
wonderfully successful. The paste was mounted in collapsible 
metal tubes, and was squeezed out on the wound and on surrounding 
skin, on which it retained its position for days. I found that all 
shell wounds in South Africa were septic, except those to which the 
cyanide and carbolic paste had been applied almost immediately 
after the injuries, when it dealt cfTcctually with the spore-bearing 
' J. Amcr. Med. Atisuc, 191G, 67, 13UU. 



PERSONAL AND INTERNAL DISINFECTION 135 

anaerobes. I now use also a mixture of equal parts of 1 in 20 carbolic 
and 1 in 500 of mercuric chloride in alcohol, coloured with rosaline. 
The dj'e indicates the persistence. No case of mercurial or carbolic 
poisoning has occurred. The solution can be carried by the soldier, 
and is better than iodine, more efficient and less irritating."^ 

Everj^ combatant should therefore be provided with portable 
emergency means of at once sterilizing wounds.- Suitable for the 
purpose are "friable ampoules," brittle tubes, hermetically sealed, 
of glass, 6 millimetres diameter, and 6 to 7 millimetres long, con- 
tracted near one end, with a file-mark on the neck. There is a small 
cotton brush by wliich the wound can be painted, and the whole is 
enclosed in a little cardboard box. The entire apparatus is not 
much larger than a pencil. By a private agency many thousands of 
these ampoules have been sent into the firing-line at a small cost. 
with very great benefit.^ 

Dr. Highet* says the " asepto " should be placed in a small glass 
capsule packed in a gauze pad. When occasion arises, the capsule 
is broken, the gauze becomes saturated with the solution, the wound 
is swabbed with it, and is used as a first dressing. " The whole 
should be packed in impervious j)aper, so that if the capsule be 
accidentally broken the solution will be absorbed by the gauze and 
still be available. Such capsules are being made uj) for general and 
Voluntary Aid Department use." 



BIBLIOGRAPHY. 

Berggren, T.: Breathing and the X-Ray Discoveries of Dr. Halls Dally. Atncr. 

Phys. Educ. Riv., 1916, 31, 513-521. 
Leavitt, S.: The Pillow as a Health Factor, Aleinist and Neurol., 1917, 38, 439- 

441. 
ViTOUx, G. : Les sections d'hygiene corporelle, Rev. d'hyg., 1917. 39, 398-40r). 
Skillern, P. G., Junr.: Dichloramine-T in Wounds, Ann. Surg., 1919. 69, 498. 
LusK, W. C. : Disinfection of Vitalized Tissues and Healing of Wounds with 

Chinosol and Salt, Ann. Surg., 1919, 69, 494. 
Pratt, E. F.: Paraffin Treatment of Wounds, Brit. Afed. J., 1919, i.,243. 
Berkeley, C, and Boukney, V. : Proflavine Oleate in Treatment of Open Wounds, 

Brit. Med. J., 1919, i., 152. 
i'.VLMA. J. DE S.: Tannin, Gelatin. Borax Film Treatment of Wounds, Cor. El. f. 

schtvciz. aerzte. May 3, 1919. 619, and Jidy 5, 1919. 70. 
PuGH. W. S. : Personal Hygiene, Education, and Sanitation Aboard Shij>, U.S. Nav. 

Med. Bull., 1919, 13, 254. 

1 Brit. Med. J., December 12, 1914, lOOCi; and December 2(). 1119. 
- These means should also be at hand in civil life, and their use taught in the 
first-aid classes that are now so common and serviceable. 
'' Lancet, Noveml)er 7, 1914, 1115. 
* Brit. Med. J., December 2B, 1914. 1120. 



136 DISINFECTION AND STERILIZATION 

Delfino, v.: Hygiene for Working Classes, Sevuira Med., 1919, 26, 407. 
Abmaingaud: Hygiene for Elderly Men, Bull. Acad, de Med., 1919, 81, 711. 
Stowell, T. E. a.: Acriflavine Emulsion as Dressings for Wounds, Br,'t. Med. J., 

1919, i., 244. 
Tubby, A. H., Livingston, G. R., and Mackie, J. W. : Acriflavine used as Paste 

and in Solution in Treatment of Gunshot W^ounds, Lancet, 1919, i., 251. 
VoGT, E.: Practical Observations on Disinfection of Hands by Gocht Method, 

Dcutsch. Med. Wochenschr., 1919, 45, 903. 
Latouche, p. : Vincent's Boric Acid Hypochlorite Powder in Treatment of Wounds, 

Arch, de med. et phann. mil., 1919, 71, 189. 
Donaldson, R. : New Method of Wound Treatment bj' Agency of Living Cultures 

of Proteolytic Spore-bearing Anaerobes introduced into Wound. Edinburgh 

Med. J., 1919, 22, 3. 
Gumming, J. C. (Mil. Surgeon): Sputum-Borne Disease Transmission, with 

Epidemologic and Bacteriologic Research, 1920, 46, 150. 
Jones. H. A. : Acute Nepliritis by Absorption of Household Disinfectants, Boston 

Med. and Surg. J., 1920, 182, 68. 



CHAPTER VII 
NON-BACTERIAL PARASITES 

Animals. 
An obvious difficulty in dealing with parasites is that many agents, 
when powerful enough to extirpate the intruders, may also inflict 
injury on higher life; this clearly imposes limitations both as to 
materials and methods, and especially applies to internal parasites. 
Incidentally it may be mentioned that neither drying, smoking, nor 
salting of food secures safety against the ova of organisms like 
trichina, tapeworm, etc. Nothing but thorough cooking will do so. 

Pediculi, or lice, causing the disease phthiriasis, are of three 
distinct species — P. corporis, capitis, and pubis, living respectively 
on the body, head, and genitals. The first kind hide in the clothes, 
and are easily dealt with by removing these cautiously over a sheet, 
boiling them for half an hour with soap and water, and ironing, 
particularly attending to the seams, where the eggs or " nits " are 
laid. Baths with soap and water and rubbing zinc ointment on 
the parts most affected complete the cure. 

For treating P. capitis, "white precipitate " ointment (Unguen 
tum hydrargyri ammoniati, 1 in 10) is frequently used, but has the 
common danger of mercurial applications — that the mercury may be 
absorbed and cause salivation and other objectionable effects. In 
place of this, the following safe and thorough method should be at 
once adopted: The hair is well saturated with 'paraffin" (kero- 
sene) oil twice a day for three days, wTapping in cloth for the first 
twenty-four hours. This will kill both the vermin and their eggs. 
It is never necessary to cut the hair. At the end of each twenty- 
four hours the hair should be thoroughly washed with soap and 
water, and any skin sores treated with a little zinc ointment, which 
is allowed to remain unmoved for about twenty-four hours before 
the next application of kerosene. 

Pediculus pubis, the " crab *' louse, is the most difficult to destroy, 
and often requires a mercurial unguent. The best is Oleatum 
Jnjdrarcjijri, which does not salivate unless used in excessive quan- 
tity (Martindale), but its use should be carefully watched at frequent 
intervals. Oleum staphisagri(v (the expressed oil of stavesacre 
seeds, Delphinium slaphisayria), mixed with 6 to 12 parts of olive 

.137 



138 DISINFECTION AND STERILIZATION 

or almond oil, is said by the Medical Press and Circular, ii., 85, 551, 
to effectually kill pediculi of all kinds, but it is very poisonous, and 
the above treatment is much jireferable. 

In institutions, steam-disinfecting machines are employed for 
killing all parasites in clothing ; ten to fifteen minutes of full heat are 
necessary. Vermin and their eggs can be killed by careful heating 
in an oven (Klein). 

Scabies, or itch, is caused by a minute insect, the Acarus scahiei. 
A\'hicli bores under the ejoidermis. It has been treated successfully 
by rubbing the patient all over with strong soap, followed by a hot 
bath for at least an hour, then applying sulphur ointment. A more 
effectual application is beta-najihthol, used as follows: /3-naphthoI 
15 parts, sapo viridis (soft or potash soap) 50 parts, prepared chalk 
10 parts, lard up to 100 parts. This destroys the acarus and cures 
the injuries. 

Several other burrowing parasites are met with, especially in 
tropical countries, and if they have not gone too deep can be 
remedied in a similar manner. Mercurial ointments are often 
effectual if used carefully. 

There are many volatile substances whose odour is very ob- 
noxious to insects, and therefore drives them away; these are in- 
sectifuges, not insecticides. Camphor and many essential oils can, 
moreover, actually kill insects. A useful insect powder is made 
from pyrethrum. The vermifuge action is one reason for the 
adoption of perfumes and incense. 

Naphthalene is also much disliked by vermin, but has an un- 
pleasant smell. It is a good preventive of moth. Carbolic and 
coal-tar soaps are a popular remedy against insects, but their effi- 
ciency is not high as generally employed. Wood creosote has been 
beneficially used (with care) in many parasitic cutaneous diseases. 

The trenches in warfare often become infested with body vermin . 
Belts are manufactured containing substances of strong odour to 
be worn near the skin, and are said to keep these pests away from 
the person. Essential oils drive lice away, but the latter are only 
killed by such substances if they remain a long time in the vapour 
of the oils, and the eggs are not killed at all. Wintergreen oil appears 
to be the most active of the class; then follow camphor, bergamot, 
fennel, eucalyjotus, and rosemary.' 

According to a research by Dr. A. Zucker :- 

(a) Lice are driven away by : Essential oils; menthol; turpentine 
oil; Peru balsam; solution of carbolic acid; precipitated sulphur; 
infusion of tobacco; black pepper; fatty acids. 

1 C'hcni. and Drug., .lunc 12, 1!)15, :U; November 27. 1915. 
- Centr. Bakl., lUlS. 



NON-BACTERIAL PARASITES 139 

(6) Lice are killed by: Cresol powder (3 per cent.); sulphurous 
acid ; mercury ointment ; ether ; benzine ; benzol ; petroleum ; carbon 
disulphide; cresol-soap solution; carbon tetrachloride; solution o£ 
corrosive sublimate (1: 1,000); naphthalene; anisol; dichlorbenzol. 

(c) Inactive are: Formaldehyde; acetylene; illuminating gas. 

For the soldiers in the field the author recommends a solution of 
anisol in carbon tetrachloride (1 : 9), and naphthalene or cresol 
powder. Clothes are best disinfected by exposing them to heat — 
e.g., in a steam apparatus or by ironing them. For disinfection of 
rooms, Dr. Zucker prefers sulphur dioxide obtained by burning 
sulphur in a stove constructed for this purpose by Professor von 
Walther, Dresden. 

Ringworm is caused by a fungus. Trichophyton or Tinea ton- 
surans. Citrine or red precipitate ointments, well rubbed in, will 
usually cure it. The juice of the herb Siegesheckia orientalis is 
recommended as a topical application (Martindale). Dockrell has 
also had considerable success with a plaster containing hydro- 
naphthol.^ 

Flies have in late years been proved to be carriers of all kinds 
of contagion. Dr. Halford Ross, of the Lister Institute, points out 
that " the decision against fly-breeders granted by Lord Justice 
Warrington in the Court of Chancery in the summer of 1914 placed 
a legal handle in the power of public health officials when such may 
be needed in dealing with persistent offenders." One of the earliest 
campaigns against the danger was initiated by the Bermondsey 
Borough Council on the advice of their medical officer, Dr. Brown. 
The municipality of Stockton-on-Tees started a similar ^\'OTk early 
in 1915. The Local Government Board urged other local bodies to 
follow suit, and recommended instructions to householders. Kitchen 
refuse must, as far as possible, be burnt. Dust-bins should have 
tightl^'-fitting tops, and all collections of refuse near houses should 
be disinfected or removed weekly. The fly requires at least ten 
days to mature, and lays its eggs in garbage, so that if accumula- 
tions of refuse are dealt with once a week it cannot multiph'. 

The most active extirpation should take place in spring, before 
the few flies that have survived the winter have begun to breed. 
In liouses these yet dormant survivors will be found behind pictures, 
curtains, etc., and a broom with a towel wrapped round it dipped in 
■■ paraffin oil " (kerosene) is an excellent cleanser. After taking the 
above precautions during 1914 a committee of Surbiton residents 
stated that " by the freedom Av^e enjoyed from flies throughout the 
whole summer we proved that the hoiise fly is a local pest remaining 

I Lanccl, 191U, ii., SU. 



140 DISINFECTION AND .STERILIZATION 

in the neighbourhood in which he was hatched. 80 that if the in- 
habitants of any particular district suffer unduly from flies it is 
largel}^ their own fault." 

Some fly-papers contain soluble arsenic compounds, and are to 
be condemned as dangerous to higher animals. Sticky fly-papers 
are not recommended. A better remedy is formahn mixed with 
sweetened milk, and placed in saucers with bread for the flies to 
aUght on. Besides those that are killed by the liquid, a mere trace 
of the vapour is very offensive to all insects. E. B. Phelps^ reports 
favourably on a 1 per cent, solution of sodium salicylate as an 
insecticide. According to a pamphlet issued in 1915 by the Medical 
Officer for Westminster, rooms in which there are many flies may 
be cleared by (1) pouring 20 drops of carbolic acid on a hot 
shovel; (2) burning cones of Persian insect (p;yTethrum) powder on 
a plate. The cones may be made by moistening the powder and 
allowing it to dry. In both cases the fumes stupefy the flies, which 
fall and can be swept up and destroyed. 

For sprinkling refuse 2 per cent, carbolic, new slaked lime, or 
chloride of lime, may be used. 

Carriers of special diseases are the phlebotomus fever fly, the 
hen flea, and some of the deadly mosquitoes.- Fleas spread bubonic 
plague, and also the parasite of " kali-agar " of India and the 
Mediterranean, and are suspected of other dangers. Rats are also 
plague-sjDreaders ; they can be exterminated by " Danysz Virus," 
which was discovered some years ago at the Pasteur Institute, Paris. 
It is harmless to man, domestic and farm animals, and birds. 
There is also a " Liverpool Virus." Phosphorus paste and various 
sugar mixtures made up with extract of squills are among the weU- 
known vermin destroyers. 

Infection by Flies and Insects. — During recent years there has 
been a gradual cumulation of evidence that the common house fly 
[Musca domestica) is responsible for the transmission of diseases, 
although a plague of flies has from time immemorial been regarded as 
a visitation from the gods. It is especially active in the transmission 
of internal diseases such as "residuary" typhoid fever, cholera, 
and diarrhoea; while Nuttall and Jepson^ have collected evidence 
pointing out that it may also act as a carrier for anthrax, diphtheria, 
ophthalmia, tuberculosis, smallpox, staphylococcus infection, swine 
fever, tropical fever, and eggs of parasitic worms. The experi- 
ments of Buchanan,* Firth and Horrocks,'"' and Graham Smith" 

1 Bull. U.S. Public Health, December, 1911. 

- See " Insects and Man," by C. A. Ealand, M.A. (Grant Richards), and " Our 
Insect Enemies," Wood (S.P.C.K.). 

3 Reports to Local Gov. Board, 1900, No. Ifi. * Lanrd. 19(»7. ii., 21G. 

5 Brit. M>d. ./., 1902, 930. ^ Local Gov. Board Report, 1911, No. 53, 34. 



NON-BACTERIAL PARASITES 141 

have definitely shown that the fly can convey organisms from in- 
fected sources to objects upon which they walk, feed, or rest, and 
that the organisms adhere to the external parts of the flies; and, 
further, that the organisms so deposited are capable of infecting 
the substances, such as milk or syrup, upon which the flies are feeding. 
NicoU^ considers that the house fly aids in the spreading of infection 
from intestinal worms. 

Jackson^ has found over 800,000.000 bacteria on one fly, while 
Esten and Mason^ found an average of over 1,000,000 per fly on 
414 flies investigated. In carrying out a " kill that fly " campaign 
it is useful to j)ublish leaflets with recommendations to minimize 
the fly nuisance by destruction and elimination of their breeding- 
grounds. 

Among such may be mentioned stable manure, spent hops, 
ash-pit refuse, dirty bedding, waste vegetables, paper, rags, milk, 
foodstufi^s (especially sugar and sweetmeats), fruit, and meat. 

The Councils' Journal of December, 1908, gives the following list 
as the principal breeding-places for flies in a manufacturing toAvn: 

**Ref use-heaps and " tips." 

*Sewage-230ol3. 
**8tables, manure-pits, and " depots." 

Dairies, cowsheds, and cow-middens. 

mikshops. 
*Slaughter-houses and butchers' shops. 

Pail-closets, privies, and ash-pits. 

Domestic refuse receptacles (movable). 
*Hide and sldn brokers' yards. 

Triperies. 

Bone works (boiling and other). 
*rried fish and chip shops. 

Knackers' yards. 

Marine stores. 

All offensive trades under the Public Health Act, 1875. 
*Jam factories. 
*Confectioners' shops and manufactories. 

Spent hop accumulations. 
*rarmyards. 

Gut-scraping deposits. 

Fish offal deposited in ash-pits by hawkers and others. 

Poulterers' refuse and offal. 
**Restaurant kitchens and basement cooking-places. 
*Kitchens of tenement dwellings, etc. 

Any accumulation of decomposable refuse. 

Those asterisked (*) are the Avorst. 

^ Loc. cit. - Boston Med. and Surg. J., 1908, 159, 4.1. 

3 Bull. Agricult. E.rp. Station, Conn., 1908, No. 57. 



142 DISINFECTION AND STERILIZATION 

Flies should be kept nway from infants und invalids, while every 
active member of the community should take steps entirely to 
eliminate this insect from the globe. The rapid multiplication of 
the domestic fly makes this a matter of some difficulty. The number 
of ova produced by a single fly in a season has been variously esti- 
mated at from two to five hundred milUons. while under favourable 
circumstances the maggots hatch in less than twenty-four hours, 
and complete their growth in from five to seven days. The pupa 
remains in this resting condition also from five to seven days, so that 
the life-cycle is completed in from ten to fourteen daj'S, according 
to the temperature, humidity, and other circumstances. 

In sharp contradistinction to the common flies w^e have examples 
of certain flies acting as specific carriers for certain specific diseases. 
This is particularly the case in the protozoid diseases. The disease 
malaria has been shown to be transmitted bj^ mosquito to man. 
At the Canal Zone of Panama the species Anophelene albimanus has 
been shown to be the propagator. Both in America and in Italy 
bovine malaria has been sho"wn to be propagated by the ticks 
Ripicephalus annulatus s. Boophilus bovis. Yellow fever produced by 
Paraplasmaflavigenium has been conclusively shown to be propagated 
by the mosquito Stegomyia fasciata, and by no other means, and in 
particular by no other mosquito. The sleeping sickness of Tropical 
Africa is produced by the Trypanosoma ga^nhiense carried by the 
tsetse fly Glossina palpalis; while Stephens and Fantham have 
isolated in Rhodesia a similar trypanosome, Tr. Bhodesiense, 
carried by Glossina morsitans. 

The general prophylactic measures taken against these diseases 
consist in : 

(1) Immunisation of the subjects exposed to the diseases. 

(2) Treatment of the subjects when infected. 

(3) Destruction and elimination of the intermediate host. 

The first method is obviously not by its nature so suitable a 
preventive measure as the third, whilst the second can only be 
regarded as the penalty of non-appreciation of proper methods of 
protection. 

During the last twenty years or so active steps have been taken 
to destroy both mosquitoes and the tsetse fly. This work has been 
encouraged by the Governments of all the Powers, more especially 
the Italian in Italy, the British and German in Africa, and the United 
States in Mexico and the Canal Zone, Panama, where the late General 
Gorgas accomplished an epoch-making work and made the canal 
a possibility. For subduing yellow fever and lowering, if not entirely 
eliminating, the malarial incidence in a district where these are ram- 
pant, the follo\ving plans of procedure should be drawn up : 



NON-BACTERIAL PARASITES 143 

1. In country districts and around the towns, jungle brush and 
grass should be cut away from around each house and burnt. 

2. All houses should be provided with a continuous supply of 
water ; if this is not available, all drinking barrels and cisterns should 
be made mosquito-proof by screens. One of the authors, when 
engaged in this problem of sanitation at Guayaquil, Ecuador, 
noticed that although this source of breeding, which is well recog- 
nised as one of the most prolific, w^as well known to the authorities, 
there was no method of ensuring that the orders issued by the health 
authorities had been carried out. Weekly visits by duly authorized 
inspectors are essential at the commencement of any such work, 
and are continually required where a native population has to be 
dealt with. 

3. Pools and marshes should be as far as practicable drained or 
filled up. 

4. Open water which is not running should be oiled with crude 
petroleum or compounds such as saprol. It is necessary to repeat 
the operation about twice a week. Wind also frequently ruptures 
the oil film. 

5. Running water should be guarded against stagnation at anj' 
point. Concreted channels are preferable to dug ditches, where 
grass can grow and produce little patches of still water. 

6. Gutters from houses should have a direct fall or should be 
dispensed with. 

7. Houses should be screened, both windows and verandah, 
the doors preferably Avith a double screen. The copper gauze used 
for screening work should have a fine mesh, and be constructed of 
electrolytic copper; small traces of impurities such as iron cause 
rapid deterioration in the damp, warm, tropical climates. 

8. District inspectors should be instructed to search for breeding- 
places and be provided with disinfectants for killing the larvae. 

9. Quinine should be taken daily, preferably in a soluble form. 
Tablets occasionally get hard and nearly insoluble on keeping. 
A United States Commission appointed to study yellow fever and 
malaria at Vera Cruz reported in 1904^ that sulphur dioxide was the 
best of the gaseous insecticides for destroying mosquitoes, and that 
formaldehyde was not successful for the purpose. As preventives 
against bites, naphthalene and eucalyptus oil in paraffin have 
been used successfully. Quarantine and fumigation of ships, 
trains, and baggage arriving from infected or suspected places 
must be rigidly enforced. 

The blowfly, while as liable as other flies to transmit disease, is 
pecuHarly objectionable in time of war. It often laj's its eggs in 
1 Bidl., 1905, No. 14. 



144 DISINFECTION AND STERILIZATION 

the nostrils, ears, and wounds of men and animals lying in the open. 
During the first hot weeks of August, 1914, several soldiers were 
found to be in a terrible state from maggots in their wounds. For- 
tunately, the occurrence of cold weather at once kills the flies. 
The Homalomyia canicular is is often mistaken for the common 
house fly, with which it is associated. 

A great many of the State Boards of Health^ in the United States 
have published from time to time official bulletins recommending 
certain procedures to be adopted in the campaign against flies. 
They practically all include the recommendations indicated above, 
and, in addition, screening of houses by means of door and window 
gauze screens; also the use of sun-blinds over shop windows is 
sometimes advised. Professor Newstead, of the Liverpool School 
of Tropical Medicine, recommends the application of 2 ounces of 
Paris green in a gallon of water to either stable manure or ash-pit 
refuse to destroy fly larvae. He finds that 99 per cent, are destroyed 
by this method. 

Mites. — The harvest mite lies among long grass. It can be 
dislodged from its host by treatment with paraffin or petrol, and 
is not dangerous to the majority of persons or animals. The itch 
mite [Acarus) burrows a long tunnel in the skin in which it deposits 
its ova. It prefers portions of the body in which the skin is 
soft — e.gr., the wrists of washerwomen. It can be killed by wash- 
ing frequently with soap and hot water, and sulphur treatment. 
The soap and hot water soften the skin and make it more permeable 
to the sulphur ointment, the grease of which suffocates the insect, 
M-hile sulphur is a direct poison. Hot baths containing salt, 
1 ounce to 4 gallons of water, are also recommended. A practical 
method used in the bush is said to consist in the application of 
tobacco juice to the skin, and holding a lighted match near the 
tunnel. The mite apparently comes out of its hiding-place, and is 
poisoned by the nicotine in the juice. 

Fleas. — The Put ex irritans, while annoying, has not yet been 
conclusively shown to convey any disease. The rat flea of Great 
Britain lays eggs in rubbish; the larvae are easily killed at 70° C. 
and 40 per cent, humidity if exposed, but when buried in the rubbish 
are not affected. The adult flea has a preference for human blood, 
but rat's blood is necessary to stimulate the sexual organs. In the 
absence of a suitable pabulum it can only live one month, while in 
rubbish it can exist for over seventeen months. Dog fleas can 
be removed by a bath with carbolic soap and quassia chips in water. 

The generally accepted theory that plague is mainly, if not solely, 

1 E.g., State Board of Health, Maine, U.S.A., 1909. 



NON-BACTERIAL PARASITES 145 

communicated to man from rats through the agency of rat fleas 
has led to active measures in the extirpation of rats and of the rat 
lleas. 

The work of Hossack,i Kitasato,^ and others^ has shown that 
plague transmission is unhappily not confined to the rat and the rat 
flea, but that other insects, such as dog fleas — possibly also human 
fleas — and the bed bugs are other modes of infection. 

As a general practice, the use of a disinfectant \\'hich combines 
both pulicidal and germicidal powers is advocated. 

Where bubonic plague is present, travellers should not be allowed 
to leave the infected area without a certificate of inoculation with 
Haffkine serum. All baggage should be disinfected. Trains should 
be likewise inspected, and washed out with disinfectant solution. 
In infected ports, ships should not come alongside, otherwise rat 
fenders must be provided. 

Lice, which have been the cause of the devastation of Servia and 
Montenegro in the European War, are best destroyed by agents such 
as petrol, paraffin, benzene, xytol, or turpentine, while discarded 
clothes should be burnt and buried. 

Bed bugs, which are also carriers of typhus, are, according to 
Dr. Shipley,* removed by a painter's flare passed along the cracks 
of woodwork, while houses are disinfected by hydrocyanic acid gas 
or sulphurous acid. 

Sheep Dips. — Among the various parasites which afflict sheep 
may be mentioned the tick Iscodes, the " scab acarus " Psoroptes, 
and the maggot Lucilia. The one which causes the greatest amount 
of damage is the scab-producing mite. Occasionally also are found 
a red louse, Trichodectes spherocephalus, and a wingless fly, the 
" ked," Melopliagus ovinns, while of bacterial or protozoic diseases 
one of the most important is foot rot (?) . Attempts to eradicate these 
parasites were made by rubbing the affected parts with preparations 
such as mercury or mercury salts incorporated with lard or copper 
as copper oleate. Zinc salts were also occasionally used. These 
were soon found to be practically useless, for not only did the more 
popular meicury ointment rapidly produce symptoms of poisoning, 
but unhatched eggs and places where the irritation had not 
developed were not noticed. 

Arsenious oxide solution was one of the earliest dips to which 
some astringent such as zinc sulphate was added. Lime, soda, and 
sulphur preparations were found to be a cure for scab, but was found 
to lower the price of the wool, probably OAving to the effect of the 

1 Reported, The Statesman, Calcutta, August 18, 1909. 
^ Sixteenth Intern. Med. Congress, Budapest, 1909. 
3 J. Hyg., April, 1902, 129. '' Brit. Med. ■/., 1914 

10 



146 DISINFECTION AND STERILIZATION 

alkali on the wool fibre. The chief defects accompanying the use 
of an alkaline dip are said to be (a) an increase in adsorptive power 
of the Avool for dyes, entailing a heavier expenditure in dyeing; 
(6) a decrease in the elasticity of the fibre, making it difficult to spin; 
(c) actual solution of the wool in the dip ; and {d) a shrinkage of the 
wool, making the operation of scouring both difficult and tedious. 
Nowadays arsenical dips are made of the alkali salts of arsenious 
acid, arsenic sulj^hide, free sulphur, and arsenious acid. These are 
efficient, and also stimulate the skin and are also a safeguard against 
reinfection. QuibeU/ in a good resume of the subject, gives the 
folloAving as the composition of a typical arsenic sheep dip : 

Arsenic trioxide . . . . . . . . 21-90 

AlkaH 2-86 

Moisture B-70 

Sulphur 68-54 

One pound is diluted with 11 gallons of water. 
The only other land of sheep dips used on a large scale are the 
carbolic acid dips, which are efficient parasiticides, but do not exert 
any prophjdactic action, as is the case with the arsenic dips. These 
dips are of varjdng composition ; emulsions, semi-solutions containing 
less hydrocarbon oils, and true solutions of carboHc or cresylic acids 
are used. The emulsified parasiticide has been found superior to 
the non-emulsified form, having the same tar acid content ; this has 
also been shown by one of us to hold true for their action on bacteria. 
Mixtures of tar acid and arsenical dips, the former frequently com- 
pounded with sulphonated castor oil or soaps, are found to be very 
effective, while more or less successful experiments have been con- 
ducted on using tobacco extracts and soluble mercury salts. ^ 

Disinfection and Preservation of Hides. — Owing to the frequent 
jDresence of anthrax organisms in hides, and also owing to the occa- 
sional sporadic outbreaks of foot and mouth disease, it has been 
found advisable to disinfect skins and hides. Older methods include 
the use of 5 per cent. carboHc acid solution, sulphur dioxide, and 
pickling sodium arsenate in salt. The carbolic acid and sulphur 
dioxide methods injure the skins, while the use of sodium arsenate 
gives unsatisfactory results. The American Leather Chemists 
Association^ have obtained good results with a 0-1 per cent, solu- 
tion of mercuric chloride. The disadvantage associated with this 
substance is the fact that it forms insoluble compounds with the 
albuminous compounds in the hides, and such insoluble compounds 
no longer exert any marked germicidal action. The association 
J " Sheep Dips," J. Soc. Chem. Ind., 1907, 12()G. 
- ,Sco J. Soc. Chcm. hid., 1907, H««. 
■^ J. Amcr. Leather Chem. Aitiauc., 1910, 5, 507. 



NON-BACTERIAL PARASITES 147 

found that the addition of 0-5 per cent, salt solution, and thus de- 
pressing the concentration of mercuric ions, prevented this precipita- 
tion. In hides which have been treated Avith sulphur and Hme, the 
formation of insoluble mercuric sulphide m the interstices of the 
hide material makes its subsequent removal a matter of difhculty. 
Sulphuric acid has also been recommended. Kohlstein and Schat- 
tenfroh^ advise the treatment of the hides -with 2 per cent, hydro- 
chloric acid in 10 per cent, brine solution. Seymour Jones- suggests 
using formic acid or some other organic acid instead of svdphuric 
acid, so that disinfection and curing can go on together. He has 
also suggested a method of soaldng the hides in mercuric chloride 
solution containing 1 per cent, of formic acid, and subsequently 
washing with lime. This method as well as Kohlstein and Schatten- 
froh's acid salt process have been favourabty reported on.^ 

Hailer* has shown that 0-5 to 1 per cent, caustic soda at 
15° to 20° C. destroj'S the spores of B. anthracis in hides after 
seventy-two hours' contact. This treatment was found more 
effective than 5 to 10 per cent, sodium chloride. 

Cupramonium hydro.xide and copper alkali tartrate form the 
basis of some patented hide and sldn disinfectants. Various methods 
have been suggested for preserving hides. The most frequent and 
probably the most efficient is common salt. Picric acid has been 
much used in the East Indies, while clay and sodium sulphate or 
dry alum have been used. Refrigeration has been attended Avith 
the production of a loose porous leather. Drying or smoldng may 
result in the formation of a gluey or partially tanned hide. 

Recently the Departmental Committee on Anthrax appointed 
a sub-committee to inquire as to the practicabilit}' of disinfection 
of wool and hair.^ As reported by the Departmental Committee, 
" manufacturing processes do not kill the living organisms (anthrax 
spores) which cause anthrax, and the disease occurs and continues 
to occur in every process from the entr}' of the raw material into the 
factory to the production of the finished goods. The danger to be 
guarded against is different from that usually met by means of 
regulations applied in factories, and the committee finally came to 
the conclusion that this is not a suitable or effective method of 
dealing with the problem, and, further, that anthrax can onl}' be pre- 
vented either by preventing the disease among animals or by the 
destruction of the organisins in wool and hair. In these circum- 

1 Collegium., 1911, 248. 

'■^ Leather Trades licvicic. 1UU8, 41, 540. 

^ Brit. Hoc. d'Encour, 1913. 

* Arbeit. Kais. Gcsundh. Chan. Abstr., lllUi, 10, 985. 

° Departmental Comuiittoo on Anthrax: Vol. I., Report of the Uieinfcction 
Sub-Committee, 1908. 



148 DISINFECTION AND STERILIZATION 

stances it was decided to endeavour to find a process by means of 
which anthrax spores in wool can be destroyed, and for this purpose 
a sub-committee was appointed to go into the whole question. The 
difficulties of disinfection of wool and hair are very great, and it was 
recognised that the prospects of finding a practicable process were 
unpromising, having regard to the failure of many jorevious efforts 
to find a successful method. The sub-committee has, however, 
surmounted every difficulty successfully, and their experimental 
work and its results are fully described in the accompanying rejiort." 
This report details a large number of experiments carried out, and 
also a final successful process of disinfection. 

The degree of the infection of the materials j^laces them in the 
following approximate order: (1) East Indian goat hair; (2) East 
Indian wool; (3) Persian wool; (4) mohair and other goat hair, 
including cashmere; (5) Egyptian wool; and (6) alpaca. The cause 
of failures hitherto has been due to the combination of the drastic 
treatment required to ensure destruction of highly resistant spores, 
often enclosed in dried or semi-dried blood-clots entangled in the 
material, and the ease wdth which the raw substances are damaged, 
rendered useless, or their value lowered for subsequent manufacture, 
or the cost of the latter increased. This important point was dealt 
with by conducting the tests on a commercial scale, the results being 
checked of course in the laboratory, the treated materials being 
submitted to the various manufacturers for working up into their 
finished products; reliable data was thus obtained as to the infliction 
of any damage, and at the same time the working cost of the different 
treatments was controlled. 

As regards the choice of a disinfecting agent, steam invariably 
causes damage; although the United States Government have pro- 
posed the issue of regulations requiring the exposure of possibly- 
infected wool for fifteen minutes at 212° F., it is found that even the 
brief steaming that would be necessary to sterilise the wool after 
the first scouring process — five to eight minutes at 212° to 214° F. — 
caused obvious damage. 

Phenol and cresol compounds are not sufficiently powerful against 
spores, although their efficiency is increased by heat; chlorine dis- 
infectants rapidly cause damage; mercuric chloride, besides being 
deficient in penetrative power, is too poisonous. The bulk of the ex- 
perimental work was conducted with formaldehyde as the disinfecting 
agent, and the final successful process consists of a hot treatment 
with formaldehyde after special washing and scouring. This method 
consists essentially of four stages, which are described as follows: 

Stage I.- -Prelhninary Ircahnml. consisting of agitation (by means 
of rakes which thrust the wool through liquid as in scouring 



NON-BACTERIAL PARASITES 140 

machiner}^) for twenty minutes in a solution of soap in water 
(preferably also containing an alkali-like sodium or potassium 
carbonate) at a temj^erature of 102° to 110° ¥., assisted by squeez- 
ing through rollers. The protection afPorded to the spores is by this 
means removed; the s^iores are rendered susce]itible to the action 
of the disinfectants and the wool is cleansed. 

Stage 2. — Disinfecting treatment in which the material is agitated 
by similar means for twenty minutes in a 2 to 2 1 per cent, solution of 
formaldehyde in water at a temperatvu'e of 102° F., assisted by 
squeezing through rollers. In this stage the bulk of the anthrax 
spores is destroyed, those only surviving which are embedded 
in remnants of blood-clots which in a few instances ma}^ have 
escaped complete disintegration during Stage 1, but A\hich become 
saturated Anth formaldehjxle solution. 

Stage 3. — Drying in a current of air heated to 160 F. The 
moisture in the wool is driven off, and nearly all the surviving 
spores in any blood remnants are destroyed. 

Stage 4. — Standing for some days to ensure by the progressive 
action of the formaldehyde which remains in the blood remnants 
the complete destruction of the few w^eakened spores which have 
survived Stage 3. 

The strength of the formaldehjde solution is recommended to be 
maintained between 2 and 2| per cent. ; there is apparently no gain 
by increasing the strength above 2i per cent. ; a reduction of the 
formaldehyde below 2 per cent, is unsatisfactory as regards greatly 
increasing the period of treatment required to ensure disinfection. 
The authors of the method are satisfied that in practical work the 
subsequent successful disinfection of the anthrax depends upon the 
thoroughness of the first mechanical washing, and although the 
experiments were conducted on an extensive scale, they were to 
some extent necessarily handicapped with inefficient machinery. 
In actual practice the preliminary washing and squeezing would be 
done by specially constructed scouring plant, which, while avoid- 
ing any damage to the wool, would adequately break doAvn any pro- 
tective covering of the spores, M'hich are then destroyed in the second 
stage. The third and fourth stages of drying and standing -would 
act as checks, ensuring the sterility of the anthrax spores. 

As already stated, infected wool and animal hair, besides grease, 
earthy matter, and excrement, is frequently soiled mth dried blood 
adhering to the material. Highly resistant anthrax spores deeply 
buried in hard dried blood-clots formed the infected test material 
in all these investigations. 

An exposure of twenty minutes in the formaldehyde solution at 
a temperature of 102^ F. kills all unprotected anthrax spores; 



150 DTSTNFFX'TION AND STERTLTZATTON 

this somowliat surprising conclusion is vouched for by Professor 
Delepine, who worked in co-o]ieration with the committee as an 
indejiondent investigator. 

No damage to the treated test materials submitted to the manu- 
facturers was reported, and only differences equal to those occurring 
within the ordinary range of variations in such materials were ob- 
served; a further satisfactory point is that the danger to the opera- 
tives is reduced to the minimum, the raw material being entirely 
manipulated b}^ machinery after entering the plant. The only 
possible sources of contamination would be at the opening up of 
packets of raw materials prior to treatment and the waste liquor 
from the scouring machinery. With regard to the former, experi- 
ments were made in the direction of an attempt to disinfect unopened 
parcels, but were not successful. The second source of danger can be 
dealt with and the Anthrax Committee in their rej^ort advocate the 
sterilisation of all such waste liquors before being allowed to pass 
into the drains, although they do not indicate what treatment is to 
be adopted for such effluents. 

The cost of the disinfection treatment is modified by the fact 
that part of the process — i.e., Stage 1— to a large extent displaces the 
usual preliminary cleaning and shaking in the worsted, woollen, 
and felt trades, and the recovery to some extent of the formaldehyde, 
thf disinfectant used. Further, as pointed out, the whole process 
is highly technical and requires skilled supervision; it would be 
advisable to deal with the matter at a large central station for safety 
and economy ; no steps should therefore be taken by interested manu- 
facturers until a decision has been reached on these points. The 
estimated cost of treatment, calculated on pre-war prices, lies between 
0-54 and 0-82 penny per pound of the various untreated materials. 

It is interesting to note that this is one of the first attempts by 
a Local Government Board in England at the systematic disinfection 
of raw materials coming into the country. 

Domestic and Farm Animals. — To keep down parasites, general 
cleanliness and avoidance of overcrowding are essential. Walls 
should be thoroughly lime-washed with fresh-slaked lime and water, 
and gone over with a rather weaker wash at intervals of not more 
than three months. It is often overlooked that the inside of roofs 
and beams should be similarly treated, since they are equally a 
harbour for vermin M'ith the walls. The lime-Mash is rendered more 
lasting in effect if about | per cent, of crude carbolic acid or 
similar disinfectant be added in the mixing. 

Against fleas and lice, which are a pest to all animals, pyrethrum 
powder is effective. Dr. R. S. MacdougalP recommends " creohn- 
1 Stephen's " Book of the Farm," 1909. 



NON-BACTEEIAL PARASITES 151 

ated water, a 10 per cent, solution," also stating that sawdust 
soaked in a solution or emulsion of naphthalene placed in the nests 
of birds Avill give them peace. If pine-wood shavings or wood wool 
are placed in a nest, no lice or fleas will live in it, on account of the 
aromatic odour. ^ It is said also that bracken makes a good lining, 
as it is disliked by insects. 

For Phthirius inguinalis, the crab-louse in animals, a remedy is 
found in stavesacre ointment. For Acari (mites), that so frequentl}- 
infest birds, a 2 per cent, solution of carbolic is a preventive as 
well as a curative. Chloroform water (1 to 6) is also of service. 
Other remedies are sulphur ointment and benzene (used very care- 
fully). Fowls can be dusted with sulphur. Worrall found Izal 
effective against sheep acarus. 

Mange is due to the parasite Sarcoptes scabiei and other species. 
It is treated by a lime and sulphur wash made as follows : 25 pounds 
of flowers of sulphur, 12i ])ounds good quicklime. Triturate to a 
smooth cream. Transfer to a boiler, make up to 20 gallons with 
water, boil and stir half an hour. Make up to 100 gallons. 

A powerful insecticidal soap is described by Gouthiere and 
Ducancel.- Quinoline bases are made to combine with fatty acids 
(oleic, sulphuricinic. etc.) and with resins, Anth or without the addi- 
tion of copper compounds. To these soaps, toxic salts such as 
arsenites or arsenates of lead, sodium, iron, etc., may be added. 
Or mixed soaps may be obtained b}^ neutralising the basic substance 
with a mixture of fatt}" acid and arsenious or arsenic acid. 

For Warble fly in cattle, equal parts of Archangel tar and paraffin 
oil are as effective, with less injury to the hide, as the old composi- 
tion of train oil, sulphur, and spirit of tar.^ 

Favus is a fungus affection which is now rare in man, but frequent 
among domestic fowls, also attacking dogs, cats, and rabbits: it is 
verj^ common in rats and mice. It is caused by AcJiorion Schoen- 
leinii, and is exceedingly contagious. The Board of Agriculture 
(Leaflet 67) prescribe washing with warm water and soft soap, and 
then rubbing in an ointment of vaseline containing 5 per cent, of 
silver nitrate. A 10 per cent, solution of carbolic acid has also 
proved curative. 

Worms in fowls can easily be expelled by a dose of thymol — 1 
grain made up into a dough pill and administered morning and night. 
Similar good results have sometimes been obtained b\- the use of 
3 grains of santonine given in the same way.* 

^ Leaflet 57, Board of Agric. and Fish., p. 5. 

2 Fr. pat. 444,021, 1911 and 1912. 

^ J. Roy. Agric. Soc, 1913, Annual Report of the Zoologist. 

* Leaflet 58, Board of Agriculture. 



152 DISINFECTION AND STERILIZATION 



Plants. 

It has been estimated that insect and fungoid pests reduce our 
vegetable and fruit crops by at least 25 per cent, in value every year.i 
The best preventive is to keep the cultivation area as clean as pos- 
sible, and to use soil dressings and fumigants freely at the proper 
times. Vegetable debris should on no account be allowed to accii- 
mulate; it is even unsafe to dig it into the ground, but is better to 
burn it as soon as possible and restore the ash to the land. Attend 
to the sujjpression of weeds (especially those allied to the culti- 
vated plants), as these also harbour vermin and fungi. 

To combat the lower forms of animal life, a knowledge of their 
habits is necessary. The most effective procedure is to destroy 
their eggs, but unfortunately these are protected by their natural 
coverings, so that agents strong enough to penetrate the envelopes 
will almost certainly injure the plant which is their host. When, 
on the other hand, the eggs are laid on bark, on walls, or in soil, they 
can be strongly treated. A number of species, however, breed in 
stagnant water, and some in clear lakes and streams. 

Although the mature forms of a few insects {e.g., turnip fly and 
weevils) are actively injurious, as a rule they are only destructive 
in the larva state — as caterpillars, grubs, or maggots. This is 
usually the longest period of their lives, lasting in many cases for 
more than one season. In the pupa or chrysalis stage they are more 
difficult to destroy, as they are envelojaed in a tough jacket, occa- 
sionally in a cocoon, and hidden in the earth or in some obscure 
place.. Wire-worms, leather-jackets, and various larva? spend 
months, and even years, in the soil, and do enormous damage to 
roots. But insects may pass the winter in either of their three 
states: (1) As larvae, still feeding on what remains of vegetable 
matter, or even lying dormant in the soil ; (2) as pupae or chrysalides 
in a condition of quiescence; or (3) sleeping in the perfect form in 
some sheltered place. The last indicates that all possible shelters 
for hybernating flies should be searched out and, as far as can be, 
syringed. Immediately after such croj)s as peas have been gathered , 
the ground should be dressed with a preparation capable of killing 
the larvae which have dropped off the crop fully fed and purposing 
to remain in the soil till next spring. Most of them can be killed 
by lime and soot forked in, but for certainty another dressing of 
lime must be given in winter, digging or ploughing in deeply. 

In infested hop-land and fruit-land, where the plants are per- 
manent, besides constant hoeings and the application of caustic 

' Lloyd's " Practical Gardening," seventh edition, j>. 13. 



NON-BACTERIAL PARASITES 153 

materials in May and June, the soil immediatelj^ round the plants 
should be treated in the autumn Mith lime and soot, or earth, sand, 
or ashes saturated with kerosene at the rate of 4 or 5 pints to the 
bushel. See Board of Agriculture Leaflets 2 and 19 (weevils^) 14 
(raspberry moth), 62 (sawfiy " slug-worms "). In 19 (pea and bean 
weevils) and 22 (diamond moth caterpillars), dressing infected plants 
with 2 to 6 bushels per acre of a mixture of 1 part Ume to 3 parts 
soot is also prescribed. For " surface caterpillars " (Agrotis), 
Leaflet No. 33 recommends dusting thoroughly with fresh soot alone, 
and sprinkling a mixture of 3 or 4 of finely powdered lime to 1 
of soot close to the infested plants. Quicklime is still the most 
effective agent known against club root or " finger and toe " in 
turnips, cabbages, and other cruciferous root crops, due to a slimy 
fungus, Plasmodiophora Brassica'. A dressing of 5 to 7 tons per 
acre is given in autumn either six or eighteen months before the 
sowing. According to Leaflet 77, the latter interval is the better, 
vrith. a corn crop between. 

Light soils require discretion in the use of lime, but for heavy 
ones a good proportion is 1 ton per acre every winter. Unless it is 
at once dug in, it loses its strength or causticity by absorbing CO2 
from the atmosphere. Ordinary hme may be applied at any time 
from the autumn to the sjoring within a few weeks of planting or 
sowing. "Gas lime," though less caustic, contains tarry and sul- 
phuretted compounds, therefore is more potent against insects and 
fungi, and especially \\dre-worms. But it is for some time injurious 
to plants, hence after using it the soil cannot be cultivated for a 
considerable interval. When the recommended close of \ c"^^'^- P^^ 
rod (1-85 pounds per square yard) is applied in the late autumn or 
early spring, the interval must be at least two months.- Common 
salt has been used for the same purpose in the proportion of 7 pounds 
per rod for autumn and half that quantity for spring dressing, 
well dug or forked in. But we may remark that salt, sodium 
chloride, is not generally favourable to land plants; they require 
a preponderance of soluble potassium compounds. A top dressing 
of kainit (which is a potash mineral), 3 to 5 cwt. per acre, has been 
found effective against " surface caterpillars " (Agrotis), pear midge, 

^ Curtis says " nothing but boiling M'ater and turpentine seems to affect the 
mature weevil," so the object must be to kill the grubs and to trap the ])erfect 
insect with tarred boards. Pu.shing a light wide framework with boards well 
tarred on the under surface fastened on it, so as to come just over the plants, has 
been found to catch many destructive insects, which, being disturbed, jump up 
against the tar. Many acres may be got over in a day (Leaflet 3, Board of Agric, 
p. 4). Blossoming fruit bushes should be .shaken over tarred boards or sacks 
uoaked in kerosene (see J. Ro;/. Agric. Soc, 1913, 388). 

~ Lloyd's " Gardening," pp. 13, 16. 



154 DISINFECTION AND STERILIZATION 

wooll}^ aphis, cranefly grubs, and others, besides being a good 
manure. 

In reference to " eel-worm " {Tylenchus), which causes failure in 
clover and other crops, Miss Ormerod reported in 1897 that sulphate 
of potash at the rate of 1 cwt. per acre stopped the disease in oats ; 
and, again, that at Rothamstead on an eel-worm-infested clover 
field " a mixture of sulj)hate of potash 3 cwt. and sulphate of soda 
1 cwt. per acre w^as applied on April 3; the disease ceased, and the 
clover made a very vigorous growth." 

Many preparations safer than gas lime are sold, such as 
"Vaporite," "Kilogrub," " Fumisoil,"' "Cliffs Manurial Insecti- 
cide," and others. Some kinds, when mixed with the soil, gradually 
evolve vapours and act partially by virtue of these, but principally 
as contact poisons. 

A well-informed correspondent, however, \^Tites: "At our trial 
ground we have conducted experiments AAith various commercial 
soil sterilizers, several of which consist princi^jally of crude naph- 
thalene, and others of hydrocarbons^ emulsified with soap. Our 
results have been uniformly unsatisfactory." We have not up 
to the present in our own practice found any substance of this 
class that has been recommended in any of the horticultural and 
agricultural jiapers which gives uniformly satisfactory results. 
The gradual liberation of active vapours is only vigorous in porous 
ground. But the most effective Avay of clearing insects from soil 
is to pour carbon disulj)hide into holes about 1 foot deep and 2 feet 
apart, 2 ounces in each, the holes being then covered and the vapour 
left to act. This method has been successful in France against 
Phylloxera ; it is, however, expensive, and very dangerous from the 
inflammability of the bisulphide (a sjjark would cause an explosion) 
and its poisonous action on higher animals.^ 

Nitro-explosives in cultivation for making soil porous were first 
introduced in the United States, and it was thought also that the 
nitrous fumes Avould get rid of insect pests; but Professor Durham 
found^ that plants put in on the site of explosions were infested 
with slugs a fortnight later, although the fumes had been seen 
issuing from amongst the roots. 

The plumber's blow-lamp is used as a garden tool in France for 

^ Kerosene (" paraffin ") is, of course, a hydrocarbon. 

^ E.vperiinents might be made with thiophosgcnc, CSCI.2, prepared by the action 
of chlorine, and then stannous chloride, on CSo. It is a red, mobile, strongly fuming 
liquid " of sweetish taste," which attacks the mucous membrane. It boils at 
about 160° F., is hardly inflammable, and is only slowly decomposed even by hot 
water. For a number of trials by the Roy. Agric. Soc. with lime, soot, vaporite, 
CS2, etc., see report of the zoologist, J. Roy. Agric. Soc. 1913. 

^ J. Roy. liort. Soc, August, 1914, 7. 



NON-BACTERIAL PARASITES !•'>•'> 

destroying tho M-00II3' aphis (Schizonevra lanigera), turnip fly, posts 
like the raspberry weevil which fall to the ground when disturbed, 
ants' nests, etc. 

Acids are germicidal to wire-worms; the following figures indi- 
cate the concentrations required to kill by five minutes' contact. 
It is interesting to note that the concentrations are by no means 
equivalent in the hydrogen-ion concentrations in solution. 

Acid. Concentration per Cent. 

HCOOH .. .. .. .. M6 

. . 2-4 

. . 0-28 

. . 0-24 



CH3COOH 
CgHsCOOH . . 
C6H4(OH)COOH 
H,S04 
NaHS04 



0-42 
1-8 



Gaseous insecticides such as hydrocyanic acid and sulphuretted 
hydrogen (this is apt to injure plants), and the vapour of volatile 
liquids like carbon disulphide, benzene, formalin, and nicotine, are 
employed in confined spaces, as in greenhouses, by fimiigation. 
Fumigation with hydrocyanic acid has been extensively used in 
America against insects in fruit trees, San Jose scale, etc. In Eng- 
land it seems to be the only remedy for black-currant mite, Phycop- 
fiis ribU, but in other respects Leaflet No. 1 (published 1894, re- 
vised 1901) of the Board of Agriculture and Fisheries says " fumiga- 
tion with hydrocA'anic acid, as largely used for scale attack abroad, 
has not met with the success which at one time was thought likely. 
Further experiments may, however, show it to be useful as regards 
the cleaning of young plants." Nicotine is the strongest insecticide 
that can be used with safety under precautions that bear in mind its 
\ery poisonous nature to higher animals. In a strength that will 
kill all lower animal life it is quite harmless to vegetation ; its vapoiir 
will not injure the bloom of the most delicate fruit, nor the perfume 
or colours of flowers.^ Incidentally it may be mentioned that it 
does not kill bacteria, but these produce only a few diseases of 
])lants. although certain species (chiefly Bacillus amylobacter) cause 
wet rot of potatoes, also rot of onion bulbs, and tho pink decay of 
wheat. ^ 

Nicotine has a high boihng-point (250° C. ), and easily oxidizes, 
hence to vaporize it alone would be diflicult and wasteful. There- 
fore it is mixed with a more volatile substance which will carry 
off its vapour without change, and evaporated from a metal dish 
over a small lamp. It is cheaper to buy the fumigating liquids 
ready made, as they arc manufactured in bond from duty-free 

1 G. E. Williams, J. Hoy. Hort. Soc, September, 1902. 
^ Dr. Fream's " Agriculture," Roy. Agric. Soc, 1912. 



15G DISINFECTION AND STERILIZATION 

tobacco. They should be purchased of guaranteed strength; an 
example of quantity and cost is | ounce per 1,000 cubic feet, costing 
4kl. Another method is often practised, by mixing it or tobacco 
juice \\'ith combustible fibrous material such as rags or paper, 
adding a little nitre to promote combustion, igniting the dried mass, 
and allowing it to smoulder away in a greenhouse. Some simply 
burn dry tobacco leaf in the ordinary manner. Both these methods 
are unreliable, and likely to injure plants.^ Another compound, 
'pyridine, is produced which is distinctly injurious to plant life. 

In fumigation the house should be kept tightly closed for six 
hours; then open the door and windows, and do not enter till the 
house is thoroughly ventilated. 

The small amount of nicotine contained in tobacco accounts for 
the high price of the preparations, but on the other hand for fumi- 
gation a little goes a very long way, while for efficient spraj-ing the 
dilution with water may be often more than 1,000 times. As an 
instance, Spencer Pickering, at a conference of fruit-growers held at 
the South-Eastern Agricultural College, Wye, Kent, said he had found 
that for Psylla (apple sucker) a solution containing 0-075 per cent. 
(1 part in 1,333) of nicotine was in all cases efficacious, and that the 
occurrence of slight rain A\'ithin a few hours of spraying did not 
nullify that effect.^ 

When it is required to apply nicotine directly to the plant, other 
substances are usually mixed with the solution, causing it to adhere 
to the leaves; the mixture is then diluted Avith Avater. A syringe 
Avith a fine nozzle is used, or, better still, a spraying apparatus. 
So applied, it brightens the foliage, does not stain, and will not 
injure the roots or retard the groAvth of the plants so treated. 

The importance of addition agents necessary to cause the wash 
or spray to adhere to the leaves of the plants can scarcely be over- 
emphasized. We are indebted chiefly to Pickering and his re- 
searches on the stability of oil-Avater emulsions for drawing atten- 
tion to the role played by surface tension in these cases. It is 
evident that a suitable spray should possess the folloAving de- 
siderata : firstly, it must spread the suspension of the fungicide over 
the Avhole of the leaA^es and stem, and not collect in small globules 
or roll off — i.e., it must wet the plant; and, secondly, the suspension, 
when once deposited on the plant surface, must not be washed off 
by any accidental shoAver. 

The first of the conditions involves a study of the surface tension 

^ G. E. Williams, nt supra. He justifies at length the condemnation of the 
combustion procedure. 

2 See also Pickering and Theobald's " Fruit Trees and their Enemies," and the 
eighth and tenth reports of the Woburn Experimental Farm of the Roy. Agrio. 
Society. 



NON-BACTERIAL PARASITES 157 

of the spray ; spraj's with low surface tension will spread more easily 
than those possessing a greater surface energy, which will tend to 
keep the wash in the droplet form. The surface tension of sprays 
can be adjusted by the addition of substances such as soaps or 
saj)onin, which lower the surface tension, so that an effective spread- 
ing will be obtained. The recent work of Langmuir, Harkins. and 
others (see Chapter IX.) has indicated that this effect may not be 
entirely physical in its action, but is pseudo-chemical in behaviour, 
and the use of addition agents which will form loose adsorption 
compounds with the cell wall of the plant may prove effective 
spreading agents. The second point — viz., the subsequent adher- 
ence of the suspension to the plant surface — ^2:)resents greater difificul- 
ties. It is evident that the fungicide must be slighth' soluble to 
prove eflfective, but must not be washed off by rain falling on the 
leaves. To accomplish this end, attempts have been made to coat 
or protect each particle with substances like glue or gelatine, whicli 
\\'ill adhere to the plant surface more firmly than the unprotected 
particle; in other words, the surface energy of the area of contact 
between the plant surface and particle must be very much less than 
the sum of that between plant surface and water and the particle 
and water. The preparation of an ideal wash thus entails the pres- 
ence of two addition agents : one in the suspension medium which 
will ensure the spreading of the medium carrying the particles of 
fungicide over the surface of the plant, and a second one protecting 
or coating the fungicide particles ensuring a firm adherence to the 
leaves. It is possible that one agent could perform the two functions, 
provided that it contained suitable chemical groupings within its 
molecule to form adsorption compounds with the plant surface and 
with the fungicidal particles. 

A dressing to destroy eggs, etc., of insects on the bark of trees 
or on old walls or fences is made by adding J pound of tobacco, 
i pound flowers of sulphur, and | j)eck of lime to 3 or 4 gallons of 
water, and stirring well at intervals for six to ten hours; syringe 
with the clear liquid. Some moths, such as Zeuzera pyrena, which 
infest fruit-trees, deposit their eggs to a considerable depth in the 
crevices of the bark, hence old or rough bark (also lichens and moss) 
should as far as is safe be scraped off before syringing. 

Caustic alkaline washes are most successful in cleaning the trees 
of an orchard (also bushes) in winter and destrojing pests, the best 
time for the spray being about the middle of February, as then it 
will kill the majority of the eggs. Prcparafion : Dissolve 1 pound 
of commercial caustic soda and 1 pound of crude potash (carbonate) 
separately in water; mix and add \ ]i()un(l soft soap, and make up 
with soft soaj) to 10 gallons. It has been said that alkaline washes 



158 DISINFECTION AND STERILIZATION 

cause the living bark to t-rack, and undermine the health of trees, 
but the Board of Agriculture (Leaflet 70) have not found this. 

There are a nuznber of spraving liquids that, altliough less power- 
ful than nicotine, are often of service {e.g., for apple sucker, Psylla). 
Soft soap is itself useful; some recipes containing it are: (1) 5 parts 
quassia chips stirred Avith 100 of hot water, then add 6 of soft soap 
and 4 pints carbolic No. 5 (for red spider and a great number of other 
pests); (2) 10 pounds quassia and 7 pounds soft soap to 100 gallons 
water; (3) 8 pounds soft soap, 2 pounds ground hellebore, 3 pounds 
kerosene, well stirred together in 100 gallons boiling water {care 
as to inflammability) ; (4) boil in 2 quarts of soft Avater 1 part of soft 
soap; while still boiling, remove to a distance from the fire or 
flames and add a pint of "paraffin " (kerosene); work the whole 
thoroughly together by means of a hand pump or syringe and add 
10 gallons of water. No. 4 is an effectual wash for green fly (aphis), 
white fly, etc., also by sj^raying during April and May to prevent 
maggot in onions ; for red spider^ add ] ounce of liver of sulx^hur per 
gallon. Quassia extract mixed Avith soap solution is a good insecti- 
cide for roses. Nos. 1, 2, and 4 above have the advantage of being 
non-caustic and non-poisonous to higher animals, which is a con- 
sideration when dealing with fruit and vegetables. Nicotine and 
other poisons can be absorbed through the skin, unless india-rubber 
gloves are worn. Repeated spraying with dilute solutions is more 
effective than a single application in more concentrated form, 
besides being safer for the tender growths of the plant. 

Particularly for root crops, it is useful to soak the seed in kero- 
sene — or, better, turpentine (Leaflet 3, Board of Agriculture)^ — before 
being sown; this keeps " fly " away from the seedlings. Spraying 
the ground, and even the seedlings, is sometimes further necessary. 

Dusting with various powders such as a mixture of tobacco dust 
and sulphur, pyrethrum, hellebore,- and others is sometimes prac- 
tised, but is neither sure nor cleanly. The only one of practical value 
is quicklime, and this injures plants. 

Parasites that have protective coverings, like mealy bug. scale, 
cuckoo spit, and " tent caterpillars," demand greater force in syring- 
ing, which is made more effective by brushing, also by using the 
liquid warm, at 110° F. (43° C). 

For the codling moth and leaf-eating caterpillars, as well as 

1 Red spider is not properly an insect, as it has eight legs, not six, and docs not 
go through the three transformations; it belongs to tlio Arachnida, or spider group. 
The wash has to be apjJicd with considerable force, to break up the web which pro- 
tects the eggs and mites. 

- Hellebore wash is used successfully against gooseberry sawlly and some other 
species: 1 (ninco of the powder and 2 ounces Hour to 3 gallons water, kept stirred, 
and sprayed. 



NON-BACTERIAL PARASITES 159 

turnip " flea " beetles, and many other intractable pests, arsenate 
of lead is used. It can be jjurchased as a paste, which, when properly 
made, remains a long time in suspension, and does not scorch the 
foliage. To prepare the spray, 1 ounce of sodium arsenate dissolved 
in 16 gallons of (preferably rain) water is mixed Avith a solution of 
3 ounces of lead acetate and 2 pounds of treacle added. Some kero- 
sene emulsion may also be added with advantage. Trials at the 
New York Agricultural Experimental Station^ showed zinc arsenite 
to be three times as effective as lead arsenate. When used in con- 
junction with lime or Bordeaux mixture it caused no injury to api^le 
foliage. But more or less spotting occurred when it was used alone 
or with lime-sulphiu- or glucose, and these also caused severe 
'"burning" of graj^e foliage; laboratory tests indicated that this 
" might be due in part to the solubility of the zinc arsenite in COg 
contained in the moisture on the leaves." Zinc arsenite or lead 
arsenate with Bordeaux mixture, soap, or glue, remained efficient 
for twenty-five days ; at the end of that period the poisonous proper- 
ties had disap23eared and the protection had ceased. It was observed 
that lime-sulphur solution does not resist wet weather as well as 
does Bordeaux mixture. Tartar and Bundy^ remark that while 
soap has been recommended for keeping lead arsenite in susiDension 
(instead of treacle), practical trials have shown that sometimes the 
foliage is considerably injured by the mixture. 

Paris green, a copper arsenite, has been employed extensively in 
the United States, and is also approved by the British Board of 
Agriculture and Fisheries, when used with care, for turnip and 
cabbage flea beetles; sawflies; " surface " and " tent " caterpillars, 
and those of the codHng, winter, and pith moth; " slug- worms " 
{Eriocanvpa), and other insects as diflicult to Idll. The wash is pre- 
pared by adding | j)ound Paris green to 100 gallons water and 
thoroughly mixing with 1 pound lime ; the whole must be kept well 
stirred. It can be bought as '" Blundell's Paste," which is more 
easily mixed with water than the powder. The Board prefer 
lead arsenate, which will kill the larvae, as Paris green sometimes 
damages the leafage. London purple is another arsenic prepara- 
tion, used with lime as above. None of these poisons must be 
used for six weeks before the fruit is gathered, green or ripe,^ nor 
where vegetables for early use are grown under the trees.' 

Banding trees with sticky compositions, better put on rings of 
grease-proof paper fitting closely to the trunk, is necessary to entrap 
those vermin that ascend the stems from the ground. It is of especial 

1 Technical Bulletin, March, 1913, No. 28. 

- J. hid. Eng. C'hcin., 1913, 5, oGl. ^ Lcallct lli, p. 3. 

* Lcafiot 4, p. 4. 



160 DISINFECTION AND STERILIZATION 

benefit in early autumn. The bands must be watched, the captures 
removed, and the composition kept adhesive, otherwise the process 
becomes ineffective. 

Fungoid Parasites of Plants. — Much valuable work has been done 
during recent years in combating and controlling the fungous diseases 
of plants. The enormous losses caused by them in French vineyards 
led to their extensive study, and to experiments proving that certain 
salts of copper (especially the famous " Bordeaux mixture " and 
its varieties), sulphur in various forms, and alkalies were beneficial, 
and there seemed to be a prospect of the eventual control of the 
troubles caused by fungous diseases generally. 

Sulphur in the form of " flowers of sulphur " has been largely 
used for hop mildew. Dusted over the plants, it leads to the sIoav 
formation of .SO2, which in hot weather can be smelt where the 
powder is widely used. But at ordinary times it often fails, 
therefore it has been generally replaced by copper salts. A special 
use is described in Leaflet 64, Board of Agriculture. If wilting of 
the leaves of trees suggests root rot (caused by the fungus Rosellinia 
necatrix), an examination should be made at once; if white mycelium 
is found, the roots should be exposed and covered with sulphur, 
and this should also be mixed with the soil used for filling in, which 
should be fresh and free from mycelium. The infected soil is 
removed and sterilized by adding quicklime or gas lime. 

The fungicidal activity of sulphur is to be attributed to the forma- 
tion of thio -acids with atmospheric moisture under the influence of 
light, the primary reaction being in all cases the formation of hydro- 
gen sulphide and sulphur dioxide according to the reaction — 

3S + 2H2O =^?=i 2H2S + SO2. 

Although the equilibrium point of this reaction is at normal 
temperature on the left-hand side, yet the small quantities of the 
products formed are withdrawn from the sphere of action by secon- 
dary reactions. Ground crystals of sulphur adhere to the plant sur- 
face better than flowers of sulphur, yet the latter are more reactive 
with moisture and generally possess an insignificant quantity of 
various thio-acids adsorbed on their surfaces. 

Lime-sulphur washes prepared by the solution of sulphur in lime- 
water consist essentially of mixtures of calcium penta- and hexa- 
sulphide ; these readily undergo decomposition into disuljihide and 
free sulphur, which reacts as above. The calcium disulphide also 
reacts with the atmospheric carbon dioxide with the production of 
free sulphur and calcium thiosulphate. 

(Sulphur vapour is a good destroyer of mildew and other diseases 
of plants under glass. Campbell's vaporizer is a vessel heated by a 



NON-BACTERIAL PARASITES 



161 



lamp; the stem of the fumiel outlet is loosely closed by a hollow 
glass ball, which rises and falls so as to allow the vapour to escape, 
but at the same time prevents the boiling sulphur catching fire from 
the entrance of hot air; 6 ounces of sulphur is sufficient for 10,000 
cubic feet. Potassium sulphide ("liver of sulphur ") spray, in the 
strength of ^ ounce to the gallon of water with | ounce soft soap, 
is the best remedy for gooseberry mildew, and for cucumber and 
melon leaf blotch. 
^ Copper Salts. — The most successful fungicides which have 
achieved a wide j^opularit}' are those containing copper salts in suit- 
able form. It is estimated that over 12,000 tons of copj^er are used 
annually in France to combat the Phylloxera on the vines. 

Bordeaux mixture is essentially cupric hydrate suspended in water, 
and is made by precipitating a solution of copjDcr sulphate by 
(usually) milk of lime. If too little lime is added, free copper sul- 
phate will be left in solution and will injure the plants, while if the 
solution is too strong in lime it is also harmful. Since the theoreti- 
cal proportions are: crystallized copper sulphate (CuS04,5H20) 249, 
quicklime (CaO) 56, it will be seen by the following standard recipes 
that a decided excess of lime is prescribed by experience. The 
Eleventh Report of the Woburn Experimental Fruit Farm (Royal 
Agricultural Society) says: "' No direct fungicidal action is possible 
without the risk, and indeed almost the certainty, of some damage 
to the plant. " But in instances of apparent scalding, the appearance 
is really due to the destruction of the fungus by the fungicide, so that 
the supposed injury is actually a benefit. In any case the fungus must 
be antagonized, and does far more harm than the chemical remedy. 

Modifications of Bordeaux. Mixture. 







Bordeaux 




Burg 


indii 


" Oil pram." 


Woburn 
Winter 






Mixtures. 




Mixtures. 
















Tl ash. 




A. 


B. 


c. 


D. 


E. , 


F. 


G. 


H. 


Crystallized copper sulphate, 


















98 per cent, (pounds) 


12 


8 


12 


12 


20 


12 


— 


15 


Copper carbonate (ounces) . . 


— 


— 


— 


— 


— 


— 


10 


— 


Quicklime (pounds) . . 


8 


8 


6 


10 


— 


— 


— 


o 


Washing soda (pounds) 


— 


— 


— 


— 


25 


15 


— 


— 


Caustic soda (pounds) 


— 


— 


— 


— 




— 


— 


20 


Liq. amnion, fortiss. (pints) 


— 


— 


— 


— 


— 


— 


o 


— 


Treacle (pounds) 


— 


— 


— • 


10 


— 


— 


— 


— 


" Paraffin " (solar dist.) 


















(pints) 


— 


— 




— 


— 


— 


— 


50 


Water (gallons) 


100 


100 


100 


100 


100 


100 


100 


100 



A, B, E, and H are given by Wrightswn and Newsham, whilst C. D, F, and G 
are from Leaflet 2:J. Board of Agriculture. A is " for potatoes "; B " for fruit- 
trees "; and C. 1). E, and F for general use. 11 



162 DISINFECTION AND STERILIZATION 

To make Bordeaux uiixturo, dissolve tlie eopper salt in 80 gallons 
of the water in a wooden or earthenware vessel (iron would be 
attacked); slake the lime and make into a cream with the other 20 
gallons of water ; strain this and pour it into the copper solution with 
constant stirring. A stronger wash composed of 30 pounds copper 
sulphate and 15 pounds lime to the lOOgallons water is recommended 
for vine mildew, Peronospor a viticola. 

Mixture D, which adheres better to the leaves, especially in 
showery weather, is prepared by making the cream of lime as before, 
but with hot water, stirring in the treacle, heating if possible till 
the lime and treacle have combined, and pouring the lic{uid into the 
copper solution. The result is a green solution of copper sucrate, 
which precipitates copper carbonate on exposure to air. 

For Burgundy mixture, dissolve the copper salt in 90 gallons of 
water, the washing soda separately in 10 gallons; add the latter to 
the former with agitation. 

For " Cupram " (G), add the ammonia to 4 or 5 gallons of water 
and throw in the coj)per carbonate little by little, stirring vigorously 
till dissolved; then dilute with the rest of the water, when a clear 
blue solution is formed which never clogs the nozzles of the sprayers. 
It can be made u]i and kept in the concentrated form in stoppered 
glass vessels and diluted when Avanted, whereas the other mixtures 
deteriorate after a few days. It is particularly suited to sprayers 
and work under glass. 

The wash H cleanses bark, removes moss and lichen, and is 
strongly fungicidal. Applied early in February, it destroys a number 
of parasites, such as woolly aphis (" American blight "). 

The other sprays should be applied at the end of June and re- 
peated in about three weeks. The average quantity is 120 gallons 
per acre. The lower side of the leaves must be sprayed, as well as 
the upper. 

With regard to potato disease, the report for 1913 of the botanist 
to the Royal Agricultural Society states that while the usual kind, 
due to Phytophthora mfeMans, is cured by Bordeaux mixture, for 
other kinds, "wet rot" from Bacillus amylobacter and "black 
stalk rot " from Bacillus melanogena, no curative measures are 
known at present. Tomatoes under glass are sometimes attacked 
by Phytophthora ; then a temperature of 75° F. checks it. 

The effect of copper or other antiseptic agents is not to destroj' 
spores, which indeed live through the application. But when the 
spores germinate, the delicate young hypha? find themselves in a 
medium which is fatal to them, and the disease is thus remedied. 

Sulphate of iron (ferrous sulphate or cojjperas) is a remedy for 
some species. The canker fungus, Nectria ditissima, in its white 



NON-BACTERIAL PARASITES 163 

stage can be killed by brushing ^vith a solution of this salt — 1 pound 
to a gallon of soft water, which will also destroy lichens and moss. 
In all cases, wounds in trees must always he at once coated with tar 
to prevent spores entering. A new destructive grass parasite, 
Cladotrychium gra minis, was first noticed in 1908 in Kent. By 
watering the soil with ferrous sulphate, | pound to the gallon, the 
spread of the disease is checked.^ For brown rot of fruit, Sclerotinia 
fructigena, the trees and also the ground should be thoroughly 
drenched with this solution : Sulphate of iron 25 pounds, sulphuric 
acid 1 pint, water 50 gahons (not placed in an iron or zinc vessel, 
as the acid would act on it). A spray of the same should be used 
in January or February before any leaf-buds begin to sirell. When 
these are expanding, and at intervals as required, the trees should 
be sprayed with Aveak Bordeaux mixture. This treatment must be 
followed for at least two seasons. 

Soft-soap mixtures are sometimes of value against fungi, as, for 
example, the fungus Eutypella prunastri which seriously injures fruit- 
trees, and is recognized by horizontal clustered cracks in the bark 
(see figure, Leaflet 87, Board of Agriculture). To prevent the spores 
germinating on the bark and entering the wood, paint the entire 
stem with a mixture made thus: Reduce soft soap '' to the consist- 
ency of thick paint " by adding a strong solution of washing soda; 
add 1 pound of powdered quicklime to every 5 gallons of the prepara- 
tion, and thoroughly mix. This generally lasts one season. 

The carbolic family of disinfectants have generally uncertain 
value as fungicides. Cyllin soap is found by many rose-growers to 
prevent mildew. 

Seed sterilizing. — Fungous diseases of grain crops are generally 
caused by spores of the fungi becoming mixed with the seed, and 
then germinating with the latter and producing a mycelium (thread 
growth) which attacks the young plants. The commonest are 
rust {Uredo), mildew [Puccinia), smut [Ustilago), and bunt iTHletia).'- 
Itis always desirable to treat the seed before sowing with a " steep " 
or "pickle," the most usual kind being a solution of sulphate of 
copper, " bluestone." The grain may be poured into a vessel (not 
of iron or zinc) containing a | per cent, solution, and stirred up fre- 
quently for twelve to sixteen hours. In this countrythemorecommon 
method is to sprinkle the dry grain with a 10 per cent, solution 
of the copper salt, 2 pounds in 2 gallons of soft water sufficing for 
J cwt. of corn (Fream). The liquid is distributed over the seed 

^ ,7. Board of Agric, November, 1913. 

- The report of the botanist to the Royal Afjricultural Society for lilKJ records 
that travelling threshing-niachines are often contaminated with s].(res of burnt 
fungus. 



164 



DISINFECTION AND STERILIZATION 



spread on the barn floor, and the whole well mixed up with a wooden 
shovel or rake, and afterwards turned over two or three times. 
As it dries, a thin coating of the sulphate is deposited on the grain. 
Fream states that this treatment is less successful against smut than 
it is against bunt. " Seed wheat is thus dressed on most farms to 
protect the crops against bunt, which gives a fishy taste to the flour, 
yet wheat sometimes suffers as much from smut as barley and oats, 
which are never dressed "■ — ^because the process prejudices their 
germination. They are treated by Jensen's hot-water method, 
which depends on the fact that if seed be immersed for five minutes 
in water at 127° to 133° F., its vitality is not impaired, but smut is 
prevented. Leaflet 92 (Board of Agriculture) gives the folloAving 
directions : About 10 gallons of boiling water are placed in a tub, and 
cold water added (about an equal quantity) tiU a temperature of 
130° to 135° F. — not over nor under — is reached. One bushel of 
seed in a sack or closed basket is dipped for five to seven minutes, 
then removed and spread out to dry. We must emphasize that there 
is a chance of recontamination by spores during the desiccation; 
this is less if it is done on a drained floor which has just previously 
been sterilized by hot ivater and allowed to cool and become partially 
dried. There is not the same danger in the copper and formahn 
methods, in which some of the disinfectant remains on the seeds. 
For treating seed oats or barley the same leaflet states that a similar 
dipping for ten minutes in 1 pint of 40 per cent, formalin to 36 gallons 
of water has of late years been used with great success, this 
quantity, costing about 2s., being sufficient for 40 to 50 bushels 
of seed. 

In each of these processes the vitality of a certain percentage of 
the grains is destroyed, but only of those that would tend to produce 
weak plants. The loss in copper treatment may be diminished by 
dusting with powdered lime after steeping. Chloropicrin in the 
proportion of 20 c.c. per cubic metre of space has recently been 
proposed as a parasiticide in grain stores- The following data 
for certain salts indicate the relative concentrations necessary 
to destroy barley seeds on prolonged contact : 



Salt. 


Concentration. 


Salt. 


Concentration. 


CuClg 
HgClo 
CcIW., 

AgNOg 

ZnCio 

TiCig" 


lin 7X108 
1 in 3X 108 
lin 1X108 
1 in ix 10" 
1 in 46,000 
1 in 12,000 


Ba(N03)., 

MnCl., 

Borax 

Cal, 

CaB^rg 

CaCU 


1 in 4,200 
1 in 1,000 
1 in 1,000 
lin 1,000 
1 in 1,000 
1 in 2G0 



NON-BACTERIAL PARASITES 165 

In testing for seed vitality the sowing method is usually adopted ; 
care, however, must be taken to ensure the removal of the fungicide 
before planting out. It seems probable, however, that in the near 
future the somewhat tedious sowing method will be supplanted by 
the electric " blaze " current method, in which vitality is indicated by 
the response of the seed to electrical stimulation. 

Weed Killers. — -We shall have occasion to note that many germi- 
cides function through their plasmolytic action on micro-organisms. 
This conception has been extended to plant life, for whilst most 
plants are destroyed by drastic treatment such as by 5 per cent, 
sulphuric acid, 1-5 per cent, of sodium arsenite, or 1-75 per cent, 
of calcium sulphide, it is possible to differentiate between plants 
possessing relatively thick cell walls and those, such as Ginapis 
arvensis (common charlock), in which the cell walls are comparativelj' 
thin, and thus more susceptible to poisons. The following strengths 
of solutions have been suggested for the selective removal of charlock 
from growing crops : 3 per cent, copper sulphate, or 10 to 12 per cent, 
of ferrous sulphate, using 40 to 70 gallons per acre. 

SdH Sterilization. — -RusseP at the Rothamstead Experimental 
Station has shown that by treatment of soils with mild germicides 
such as chloroform, toluene, or carbon disulj)hide in suitable con- 
centrations it is possible to selectively remove or at least diminish 
the protozoan population of the soil. The immediate result is a 
great increase in the number of soil bacteria, and especially the 
nitrogen-fixing organisms. 

The following concentrations of volatile antiseptics and disin- 
fectants are stated to be sufficient to exert the selective action : 



(J^H^CHg-FCSa 


0-09 per cent. 


CgHg 


. . 0-16 per cent 


Cyclohexane . . 


017 „ 


CCI3H .. 


.. 0-23 „ 


Ethyl ether . . 


0-74 „ 


Hexane 


. . 0-86 „ 


Ethyl alcohol . . 


4-6 







Gruzet finds that a hydrogen-ion concentration of N 1200 is germi- 
cidal to over 99 per cent, of the soil bacteria. - 

In the near future an extension of this method to the farm is to 
be anticipated. 

A report by the Minister of State for External Affairs, Melbourne, 
in 1914, observes that in Australia, on the whole, " the losses through 
animal and insect pests are, except in rare cases, insignificant. By 
the enactment of drastic laws they are being entirely stamped out 
in some districts and diminished in others." Similar laws are 

1 See ./. Hoc. Chcm. hid., 11)1:5, 32, li;{->. 
- Hoil Science, 3, 199, 289. 



166 DISINFECTION AND STERILIZATION 

enforced in France and many other countries. In 1890 the In- 
telligence Department of the English Board of Agriculture was em- 
powered to conduct investigations and publish a series of reports on 
injurious insects and fungi, " so as to give timely notice as to their 
appearance and the measures for restricting their ravages." 
More than 300 leaflets on different brainches of the subject have since 
been gratuitously distributed by the Board from 4, Whitehall Place, 
and contain valuable information and illustrations; of one of them 
as many as 35,000 copies were issued. The reports on investigations 
at the Woburn Experimental Farm of the Royal Agricultural Society 
are likewise very valuable; so are the records of similar work in Ire- 
land, on the Continent, and in America. See especially a pamphlet 
of forty-one pages " on the effect of spraying with disinfectants 
on plant growth."^ Miss Ormerod's " Manual on Injurious Insects 
and their Prevention " gives detailed descriptions, and Dr. Fream's 
"Agriculture," chapter xviii., has about the latest list of insect 
pests. 

BIBLIOGRAPHY. 

GoRGAS, W. C. : Anti-Mosquito Work at Panama, Proc. Roy. Soc. Med., 1913-14, 7, 

Occas. Lect., 31-40. 
Crul, R. H.: The Rat, a Sanitary Menace and an Economic Burden, Pan-Avitr. 

Snrg. and Med. J., 1914, 19, 5-7. 
Shipley, A. E. : Cockroaches, Brit. Med. J., 1914, ii., 1007. 
LiCEAGU, E.: How War has been Waged in Mexico against the Mosquito, Amcr. 

Soc. Trop. Med., 1914, 9, 88-93. 
Perrow, M. G. : The Attack on the House Ely, Virginia Med. Scmi-Munlh., 

1914-15, 19, 551-554. 
BiSHOPP, E. C. : A Point to be Considered in Utilizing the Duck as a Mosquito 

Destroyer, Amer. J. Trop. Dis., etc., 1914-15, 2, 7(37. 
Wrightson, W. D. : Mosquito Eradication and Prevention, with Special Refer- 
ence to the Malaria-bearing or Anopheles Mosquito, Amer. J. Trop. Dis., 

1914-15, 2, 738-752. 
BiSHOPp, F. C, Dove, W. E., and Parman, D. C: Notes on Certain Points of 

Economic Importance in the Biology of the House Ely, J. Econ. Entoinol., 

1915, 8, 54. 
Headlee, T. J. : The Control of Mosc^uitoes in a Limited Locality, J. Econ. Entoniol., 

1915,8,40-47. 
Williamson, M. J.: A Description of the Cyanide Process for the E.xtermination 

of Bugs, J. Roy. Army Med. Corps, 1915, 23, C23-62C. 
Doty, A. H.: The Extermination of the Mosquito, J. Amer. Med. Assoc, 1915, 

69, 183()-1838. 
Kenloch, J. P.: An Investigation of the Best Method for Destroying Lice and 

Other Body Vermin, Brit. Med. J.. 1915, i., 1038-1043. 
The Destruction of Ely Larvao in Horse Manure, Med. Officer, 1915, 14, 31-33. 
Blanchard, R.: La lutte contro les poux, Paris, 1915, 8 pp., 8vo., Bidl. No. 3, 

Liguc Sanitaire Frangaiso. 



^ U.S. Department of Agriculture, Bulletin No. 7. 



NON-BACTERIAL PARASITES 167 

Blanchard, R. : La lutte centre la mouclie, Paris, 1915, 5(j pp., 8vo., Bull. No. 5, 

Ligue Sanitaire Frangaise. 
Bacot: The Improvement of Fly Spraying Fluids and the Control of Experimental 

Trials, Brit. Med. J., 1916, ii., 801. 
McCoRMiCK, L. M. : Urban and Rural Control of the Fly Problem, Amer. J. Pub. 

Health, 1916, 6, 1206-1211. 
MuTO, A.: Nuovo metodo di sterilizzazione entomopp.rassitario, Ann. d'ig.. 1916, 

26, 493-508. 
Phelps, E. B. : Fly Poisons: Studies on Sodium Salicylate, a New Muscicide and 

on the Use of Formaldehyde, Pub. Health Rep., 1916, 31, 3033-3035. 
Creel, R. H., and Fraget, F. M. : Cyanide Gas for the Destruction of Insects, 

Pub. Health Rep., 1916, 31, 1464-1475. 
Phelps, E. B., and Stevenson, A. F. : Exjierimental Studies with Muscicides and 

Other Fly-Destroying Agencies, Washington, 1917, Covt. Print. Off., 37 pp., 

8vo., U.S. Pub. Health Serv. Hygienic Lab. Bull., 108. 
Battle, J. T. J.: Some Unusual Migrations of Mosquito Pupae, Charlotte {X.C.) 

Med. J., 1917, 75, 77. 
Britton, W. E.: Recent Anti-Mosquito Work in Connecticut, J. Econ. Entoniol., 

1917, 10, 109-111. 
Richardson, C. H. : The Responses of the House Fly to Certain Foods and Other 

Fermentation Products, J. Econ. Entomol., 1917, 10, 102-109. 
Bertarelli, E.: I.ie istrusioni francesi per la destruzione dei ratti, Riv. d'ig. esan. 

pub., 1917, 28, 105-122. 
Bertarelli, E.: Per la distruzione de e mosche, ibid., 129-133. 
Campbell, S. A. : The Bat as an Eradicator of the Mosquito, Med. Rev. of Rev., 

1917, 23, 492-494. 
Maxwell-Lefroy, H.: The House Fly, 31 ed. Officer, 1917, 17, 167. 
Moore, W. : Toxicity of Various Benzene Derivatives to Insects, J. Agric. Research, 

1917, 9, 371-381. 
Redway, J. W. : The Common House Fly and the Problem of Getting Rid of It, 

Med. Times, 1917, 45, 215-217. 
BiSHOPP, F. C: Fleas and their Control, Washington, 1917, Govt. Print. Off., 

16 pp., 8vo. 
Felt, Ephraim Ellis: Household and Camp Insects, Albany, 1917, Univ. State 

of N.Y., 84 pp., 8vo. 
Headlee, T. J. : The Mosquito Question : Migration as a Factor in Control, Scient. 

Avier. Suppl., 1918, 85, 214. 
Thibault, J. K.: Vegetable Powder as a Larvicide in the Fight against Mosquitoes, 

J. Amer. Med. Assoc, 1918, 70, 1215. 
Walter, E. V.: Experiments on Cockroach Control, /. Econ. Entomol., 1918, 424- 

429. 



CHAPTER VIII 

WOOD PRESERVATION 

The subject is very complex on account of the multitude of j^ro- 
cesses and the great variety in methods of procedure. In common 
with many other branches, it has been overburdened with patents, 
which have led to contradictory and unreliable statements. 

Among destructive agencies to which wood is exposed, that of 
fire is beyond our province. It is sufficient to say that in some 
patents, ostensibly put forward as preservative, which soak the 
timber in solutions of inert salts- — e.g., alkaline silicates'- — these have 
only value as making the material less inflammable, other partial 
preservation only occurring when heat is applied in the injection. 
On the other hand, methods like creosoting increase the inflamma- 
bihty, and cause a dense and acrid smoke to be evolved in burning. 
Hence creosoted sleejaers have a special danger in railway tunnels. 

As to the action of air, although it is well known that the sub- 
stances which constitute the main framework of plants — lignin and 
cellulose — when pure and dry, are very j)ermanent, yet damp wood 
is apt to be considerably weakened by oxidation ; this is decreased 
by such organic applications as have an avidity for oxygen them- 
selves. In green wood the changes in the fibre are promoted by 
vegetable ferments or enzymes existing in the juices. These 
substances are coagulated and rendered inert by all effective 
methods of preservation. At the same time, seasoned timber 
can be treated so much better than green, and wood should be 
seasoned for at least six to twelve months before treatment. 

Water swells, and to a certain extent softens, the fibre, and can 
assist the penetration of oxygen and of many vegetable and animal 
destructive agents, hence waterproofing is the real basis of a large 
number of processes. Thus in Enrodi's (1913) "the wood is im- 
mersed in molten waxes and cleansed with a solvent." This would 
be expensive, and only applicable to special purposes. Lerach (1908) 
claims to preserve wood from splitting and rotting by coating Avdth 
plaster (calcium sulphate), resin oil, and benzine varnish (10 j)er cent, 
colophony in benzine). A cheaper process uses a mixture of asphal- 

^ J. Soc. Chcm. Ind., 1913, 946, 
168 



WOOD PRESERVATION 169 

turn with mineral oils " to stop up the open wood cells." But by 
itself waterproofing is not usually sufficient . 

The same may be said of simple mechanical sterilization by dry 
or moist heat. Dry heat makes the wood shrink or warp, and in 
jures the fibre. Moist heat (steam) properly applied kills any organ- 
isms in the wood, and also extracts its putrescible juices, which are 
the chief food of moulds or insects. To exclude such enemies per- 
manently we must use at the same time an agent which will be 
poisonous to them. 

In some cases, however, waterproofing is almost all that is 
demanded. Seidensehnuri remarked that phenolic compounds are 
not necessary; " old sleepers only contained neutral oils;- lubricating 
oil has no preservative action; pure neutral anthracene oil is good." 
The Santa Fe test,^ with a crude "non-antiseptic" petroleum 
(Bakersfield) proved the preservation of timber for a number of 
years b}^ mere waterproofing. In the same year the Engineering 
Record, N.Y., stated that waterproofing, rather than preserving 
from decay, is the chief object in saturating MOod-paving blocks 
(probably because, owing to Avear and tear, thej' have to be renewed 
so often). 

" Vulcanizing," according to Howard's U.S. patent of 1909, con- 
sists in heating the wood gradually in vacuo up to 250° F., then with 
steam at 230" F., finally raised to 380° F. Later Walhs-Tayler* 
describes "vulcanizing or Haskinizing " as roasting Avood, which 
has been previously dried by steaming, to a temperature high enough 
to coagulate its contained albumins (given as 71° to 94° C), and to 
resolve some of the fibre and sap with the production of wood creo- 
sote. 

Many impregnating patents have claimed a large number of 
inorganic solutions as germicides or preservatives which are neither ; 
the substances are of little or no use, beyond that some of them give 
the small and inadequate protection of a coagulating effect. Early 
instances of the numerous almost useless prescriptions are acetates 
of aluminium and lead Avith glycerine, and sulphites.'^ Later ex- 
amples are: Avaste sulphite liquors (1913); salts of magnesium, 
aluminium, or iron;^ " preservation " by soaking in ammonia for a 
fortnight, AA'hen it is washed away.'^ Among complicated patents 
of doubtful utility are, in 1907, Effendi's " pectic acid," Ellis's 
"copper carbolate," Soc. Anon, per Conserv. del Legno (combined 

1 Chem. Zeit., 1909, 33, 701. - Wo shall examine this statement later. 

3 Rei>ort N.Y. Railway Age Gazette, August, 1910. 
* J. Roy. Soc. Arts, 1914, 62, 28(i. 

5 Patents 17,814, 1887: :J.3r)(). 18!):}; 14,.'->99, 1894. 

6 J. Soc. Chem. Ind., 1908, 1021; 1909, 1250. ^ /^/rf^ 1911, 1214. 



170 DISINFECTION AND STERILIZATION 

processes and apparatus). Others employ sulphur or sulphides, 
which arc of little value for the purpose — e.g., Deditius' German 
patent of 190G, sulphuretted petroleum: Chisholm, 1909, Hme poly- 
sul2:)hides (these injure metallic bolts, nails, etc.). 

In Russia brine is frequently used for impregnating railway 
sleepers, as much cheaper than creosote, though not comparing with 
the latter in efficiency.^ 

The use of metallic salts has some danger of their decomposing 
into basic compounds and free acids, the latter acting harmfully 
on the wood tissue. To avoid this, the temperature should be suffi- 
cient to coagulate albumin, and not high enough to injure the 
wood — i.e., between 60° and 98° C. This simple precaution has 
actually been claimed as a novel invention by a French patent. 
No. 376,798 of 1907. English patent 19,241 of 1906 neutralizes 
by alkaline solutions which are at the same time antiseptic, contain- 
ing, for example, cresols, naphthols (as wash waters from petroleum 
and resin-oil refineries), fluorides, or silico-fluorides. Beaumartin 
in 1911 steeped wood in copper sulphate, then in lime-water, which 
precipitated the copper as hydrate. This was converted by treat- 
ment with carbonic acid water into cupric bicarbonate, which was 
soluble and preservative, while not being injurious to the wood. 

It must be remembered that as a rule chemical substances mani- 
fest their activities in solution, and are almost quiescent in the solid 
state. Therefore all the recipes for injection of emulsions of solids, 
or for their precipitation within the wood, involve loss or absence of 
activity. 

In the most effective treatment, a preservative Uquid is made to 
enter the lower end of the wood, to follow the natural course of the 
sap and replace it, at the same time acting on j^utrescible substances 
so as to prevent putrefaction, destroying organisms that may be 
present, and rcnd(>ring the material unsuitable for the entry of fresh 
ones. The liquid may be either (1) made to enter by a head of fluid; 
(2) forced in by additional pressure; (3) drawn in by encasing the 
top with india-rubber or leather and establishing a vacuum above, 
while the lower end dips in the preservative liquor; or (4) the timber 
may be enclosed in a strong cylinder which is exhausted and filled 
with liquid several times. A possibly cheaper but less efficient 
method was patented by Nelson in 1909. Timber is heated to 100°C., 
so as to convert the contained moisture into vapour; the A\hole is 
then at once covered by the (cold) preserving liquid, which con- 
denses the steam, and the contraction sucks in the preservative, but 
the sap is not replaced. 

The second of the above methods is the quickest, but the first 

1 J. Sue. Chan. I ltd., I'JIO, 1311. 



WOOD PRESERVATION 171 

is said to give the most uniform penetration. The progress of the 
operation should be tested at intervals. If it has been properly 
conducted the timber is proof against insects and against the myce- 
lium of disintegrating fungi such as Merulius lachrymans (dry rot). 
Where wood has been akeady attacked by this organism, care must 
be taken not to spread the spores, and the most potent remedy' is to 
spray with a hot 1 in 250 solution of mercuric chloride (corrosive 
sublimate). The parts of the syringe must not be made of copper, 
brass, or iron, as these metals precipitate mercury. But barriers 
to the use of this salt for sterilizing wood are not only its cost, but its 
poisonous nature to higher life. Marked salivation has been suffered 
by the inmates of rooms where the wood has been so treated. A 
similar objection of toxic danger applies to arsenic, which figures in a 
few 2^atents — e.g., Somermeier's of 1914. Wallis-Tayler, in the 
paper already quoted, mentions a saccharine solution' or Powellizing 
process as suitable for the treatment of green Avood, the solution 
consisting mainly of sugar with a small percentage of arsenic. But, 
as we have remarked elsewhere, although arsenic is so powerful 
a poison to higher animals and insects, it has little effect on lower 
forms of life. • 

Impregnating with solutions of finorine compounds has been 
recommended as effective and cheap ;^ they are included in several 
wood-preserving patents, such as the one of 1906 which we have 
described earlier. Brase's of 1908 j^reservcs sleejoers with a mixture 
of zinc chloride, a fluoride, and tar. F. Bub's of 1913 is somewhat 
similar. Nowotny in 1913 asserted that sodium fluoride and acid 
zinc fluoride, ZnF2,2HF, are stronger antisejitics than coj^per sul- 
phate, also that their freedom from colour and odour gave them an 
advantage over creosote.^ The latter point would only be of im- 
portance in rare cases such as ornamental work. But soluble 
fluorine compounds, although preservative and germicidal, and 
possibly useful as adjuncts in other treatment — e.g., when mixed 
with nitrophenols* — are, by themselves, neither sufficiently powerful 
nor lasting for wood preservation, and have the objection that they 
are precipitated by lime and by some other metals, and so rendered 
inert. Malenkovic's patent of 1908' has this fault of insoluble 
deposition that we have condemned above. 

1 Soe also Suchard, ./. Soc. Chem. Ind., 1911, 364. 

- .Seventh Internat. Congress of Appl. Chem., London, 1909; the same paper 
mentioned attempts to use the strong fungicidal properties of organic dinitro 
compounds ; they have not been economically successful (see J. Soc. Chem. Ind., 
1909, 711; see also a full report by Teesdale, Proc. Anier. Wood Preservers' Assoc, 
1916 and 1917). 

3 -/. Soc. Chem. Ind., lOl.'J, Hid. •* Nowotny, Ocst. Chem. ZciL, 191li, 15, 100. 

° J. Soc. Chem. Ind., 1908, 1114. 



172 DISINFECTION AND STERILIZATION 

Formaldehyde, acetone, and some allied bodies, ingredients in a 
few of the proposed mixtures, ^ are negatived by cost, volatility, and 
feeble action on moulds. 

The only metallic salts that are jiractical germicides for this pur- 
pose are, in increasing order of power, those of zinc, copper, and 
mercury, and we have already given the objections to the last. 

Zinc chloride is more powerful than the sulphate, and at the same 
time more acid in its character. A 2 per cent, solution was patented 
in 1838 by Sir W. Burnett for preserving timber, hence the method is 
called " Burnettizing." It is usually conducted by first steaming, 
then impregnating with a 2 to 2 J per cent, solution of zinc chloride 
under a pressure of 7 to 8 atmospheres. On the Continent it is 
commonly termed Pfister's process. The sleepers on the Hun- 
garian State Railways were treated with this reagent forced in by 
steam pressure, but the distribution was found to be somewhat 
irregular.^ In the zinc-tannin or Wellhouse process, treatment in a 
partial vacuum follows the preliminary steaming; a small percen- 
tage of glue is added to the zinc chloride, and after impregnation for 
two and a half to six hours at 100 to 125 pounds per square inch, the 
timber receives a final treatment with a 0-5 per cent, solution of 
tannin under the same pressure for two hours. ^ 

According to tests made by the Austrian Postal and Telegraph 
Bureau* with pine, fir, and spruce poles, acid zinc fluoride is more 
efficacious than creosote. Dilute solutions were very quickly 
absorbed, variations of temperature below 50° C. having no effect. 
Another product for treating timber is mentioned, called " belHte," 
which is a mixture of sodium fluoride, dinitrojohenol, and aniline. 

Investigations carried out by the United States Forest Service 
seem to indicate that railway cross ties are somewhat weakened 
by the process unless carefully conducted. They also found that a 
light injection of creosote greatly added to the effectiveness of the 
zinc chloride treatment. 

In the determination of the amount of zinc chloride in treated 
wood, E. Bateman notes'^ that extraction by leaching also gets out 
organic substances, while incineration drives off some zinc. The 
Wellhouse method is to destroy the wood \vith potassium chlorate, 
nitric and sulphuric acids; and then to determine the zinc with 
ferrocyanide. VV^e have found sulphuric acid alone, as in the ordinary 
Kjeldahl, sufficient and less dangerous, driving off the excess of acid. 

The U.S. Department of Agriculture^ test the penetrative power 

^ Baekeland's French patent, 1908; Pages Caraus et Cie., 1909, etc. 

2 Dingler's Polytcch. J., 271, 230, and 278, 22. 

3 WaUis-Tayler, loc. cit. * Genie Civil. 58, 4().5. 
6 J. Soc. Chcm. Ind., 1914, 138. 6 Circular 190, 1911. 



WOOD PRESERVATION 173 

of zinc chloride treatments by immersing discs of the treated wood 
into a 1 per cent, solution of potassium ferrocj^anide for ten seconds. 
The excess of liquid is removed by a filter-paper and the block then 
dipped into a 1 per cent, solution of uranyl acetate and allowed to 
dry. Untreated wood will appear dark broA\ii treated white 
This method, it is claimed, will detect 0-2 pound of zinc chloride 
per cubic foot. The method is not suitable for red oak. Modifica- 
tions may be introduced for the determination of the penetration 
of copper, iron, and mercury. 

Copper Salts. — ^Kyan was the first to systematically use sulphate 
of cojiper for injecting timber to kill destructive fungi, hence the 
process is called " Kyanizing." This salt is less caustic and more 
antiseptic than zinc chloride, but it is more expensive. It was the 
earliest agent used, and it is still found effectual, although the corro- 
sion by galvanic action of any iron nails, screws, or bolts embedded 
in the treated wood is a serious disadvantage, and iron tubes cannot 
be used in the injecting apparatus. A strength of 1 per cent, is 
somewhat stronger in efficiency than the 2 per cent, zinc solution, 
but at the same time more deleterious to higher animals. 

The Hasselmann process uses a mixture of cupric, aluminium, 
and potassium sulphates heated to 118"^ to 127° C. under a pressure 
of 35 pounds to the square inch. The alum is added to prevent 
the precipitation of copper by lime in the water. 

Finely divided cojijoer^ suspended in various oils forms the basis 
of a number of wood preservatives. 

Ammonia precipitates zinc and copper solutions, but an excess 
of it redissolves the precipitate. Such a liquid is employed in Ger- 
lache's patent of 1909, presumably to avoid any weakening action 
of the ordinary solutions on the wood fibre; but it cannot be recom- 
mended, on account of the extra cost, and also because of the lia- 
bility of the metallic compounds to become insoluble and almost 
inert Avithin the tissue. 

A bulletin of the U.S. Deimrtment of Agriculture in 1911 on 
wood preservation methods in America states^ that there is an 
increase in the use of creosote, a decrease in that of zinc chloride, 
and that small quantities are used of corrosive sublimate, water- 
gas tar, crude oil, and refined coal tar. 

According to Wallis-Tayler, the zinc chloride process more than 
doubles the life of wood; creosoted wood lasts 25 to 50 per cent, 
longer than wood treated with the zinc salt, but costs three or four 

1 English patent, 22,802. 

2 Oil, Paint, and Drug Bep., August 7, 1911; J. Soc. C'hcm. Ind., 191l,10r>!) 
Out of the eighty-five wood-treating plants in the U.S., sixty-five employ ereosote 
or tar oils as a jireservative (C'lias. N. Forrest, }\' Y . Chan. Club, November, 1!>H)). 



174 DISINFECTION AND STERILIZATION 

times as irOch. The amount of presorvatives injected into 1 cubic 
foot of various classes of timber ranges from about 3 pounds of 
mercuric chloride in the case of hard woods to about 6 pounds for 
moderately hard and 10 pounds for soft woods, the corresponding 
amount of creosote oil being 3, 10, and 20 pounds respectiveh'. 
The average costs of preserving timber with zinc chloride, creosote 
oil, and mercuric chloride, are approximately lid., 5d., and 8d. per 
cubic foot respectively. 

Creosoting Processes. — ^One of the earliest jirescriptions is that 
well-seasoned timber is placed in a vessel so constructed that a more 
or less perfect vacuum can be obtained by an air-pump. The oil 
previously heated to 35° to 50° C. is allowed to enter the exhausted 
receiver, and pressure of 100 to 180 pounds per square inch is then 
applied by pumps in order to effect the better penetration of the 
antiseptic fluid. In S. B. Boulton's improved method, the exhaus- 
tion is continued after the entrance of the creosote, which is heated 
to a temperature between 100° and 130° C. The moisture in the 
wood is thus volatilized and sucked out, so that the oil subsequently 
penetrates unmixed and very thoroughly in the quantity of about 
a gallon per cubic foot. A great advantage of this jDrocess is that 
wet timber can be at once treated without being previously seasoned. 
The smell of the liquid is much disliked by the lower animals (white 
ants, etc.), while certain of the constituents have a poM^erful anti- 
septic action. Boulton and Coisne proved^ that in the course of a 
few years the lower tar acids (phenoloids) in the railway sleepers may 
completely disappear by dissolving and by volatilization, whereas 
the semi-solid constituents, such as naphthalene and the higher- 
boiling oils (above 315° C.) remained, and could preserve the wood 
for sixteen to thirt3^-two j^ears. Hence these bodies are more 
lasting in their action than the lower phenoloids, carbolic and 
cresylic acids, but the latter are of value in coagulating the organio 
matter present in the saj), and should be present in sufficient Cjuan- 
tity to accomplish this. 

Quantity and Character oJ Creosote in Weil-Preserved Timbers.^ 

— The creosote oils extracted from timber which had been in use 
many years showed an average of 32-9 per cent, of distillate below 
270° C, and 66-8 per cent, of oils of high boiling-point. The defects 
of most modern creosote preservatives are deficiency in basic oils of 
high boiling-point and the substitution for these of tar or other-wise 
viscous substances. Under proper conditions of distillation a 

^ Proc. Inst. Civil Engineers, May, 1884. For later information see Lunge'.s 
" Coal Tar and Ammonia," and Church, J. Soc. Chem. Ind., 1911, 191. 

^ G. AUeman, Proc. Ame.r. Wood Preservers' Assoc, 1914, 88; through ,7. Soc. 
Chem. Ind., 1914, 33, 832. 



WOOD PRESERVATION 175 

stable, heav}' creosote oil (specific gravitj' 1-10) could be manu- 
factured from coal tar, containing nothing which boils below 210° C. ; 
for general purposes not more than 50 per cent, of the total should 
distil below 315° C, and for wood-paving blocks not more than 35 
per cent. The quahties demanded are penetrating power, stabiUt}'^, 
and preservative and waterproofing value. All these are possessed 
in a high degree by pure heavy creosote oil. Tar has a very Ioav 
penetrating power, even when injected at a high temperature, and 
wood treated with a mixture shows a sejoaration of the components, 
oil, tar, and carbon, at the margins of the close-grain rings, the 
depth of impregnation of each constituent varying inversely as its 
viscosity. As regards stability, losses occur owing to volatilization, 
extraction by water, and crystallization in wood impregnated with 
light creosote oils. Preservative value may depend on direct anti- 
septic action or permanent adhesion of a stable oil-coating to the 
walls of the minutest cells; external filmmg without penetration is 
of little account. In the light oils the antiseptic constituents pre- 
dominate, but are volatile and largely soluble in water. The heavy 
oils are sufficiently rich in the higher homologues of cresols, both 
these and the protective oils being far more stable. Waterproofing 
also depends on the complete coating of the cell Mails with an oily 
deposit which excludes moisture. 

Teesdale, in a paper on the absorption of creosote by the cell walls 
of loood,^ found from described experiments that wood swells in 
this treatment, causing a weakening effect. 

Weiss in 1911 made a long series of tests on the different dis- 
infectants and their constituents in preventing the growth of fungi 
in wood. He concluded that :- 

1. The neutral oils of creosote are strong antiseptics, and — 

2. The middle fractions of these, boiling at 235° to 270° C, are 
the strongest. 

3. High boiling bases are strong antiseptics. 

4. The same is true of coal-tar acids, " the efficiency rising with 
the boiling-point." 

5. .Solid hydrocarbons like naphthalene and anthracene have a 
low value. 

6. Addition of filtered tar to creosote does not much affect the 
antiseptic value. 

7. Paraffin has no antiseptic value. ^ 

1 J. Soc. Chem. Ind., 1913, 23"). 

2 New York Section of Chemists Club, November, 1910, and ./. Soc. Chem. Ind.. 
1011, 190, 1348. 

^ This ha.s a bearing on Devaux'.s |>atent of 1911 {ibid., lOOl): " Paraffin or 
stearic acid, etc.,i.s dis.solved in the creosote when hot, and, cooling in the wood, go 
solid, holding in the antiseptic liquids." But they would also reduce the activity. 



176 DISINFECTION AND STERILIZATION 

8. Coal-tar creosote is much better (in the ratio of about six to 
one) than water-gas tar distillates and petroleum residues as an anti- 
septic preserver. 

The U.S. Department of Agriculture^ investigated the effect of 
mixed cresols on specimens of sap loblolly pine. The following 
fractions of the distillate of a coal-tar creosote were used, and the 
loss of weight taken over several months: 

0° to 205° C. I 250° to 295° C. 

205= ,. 250° C. ! 295° „ 320° C. 

They found that the lighter undistilled residue material fractions 
taken, separately injected, volatilized quicker than those combined 
in the original creosote. This can be explained by the outer cells 
getting filled up and sealing the inside. S. Cabot^ found that the 
higher-boiling coal-tar phenols, on exposure to air, became converted 
into tarry substances insoluble in benzene, but soluble in acetone. 
Of this tar, a part is insoluble in 10 per cent, soda, but soluble as 
an alkahne salt in water; a portion also forms with alkali, a salt 
which undergoes hydrol3'^sis on dilution ; and a third is practically 
unattacked. He concluded that the higher-boiling phenols remain 
in creosoted wood as complex oxidation jiroducts. These phenols 
have considerable preserving powers, are not volatile, and are also 
markedly fungicidal. 

In 1912 Weiss'' investigated the effect of the viscosity of the 
creosotes on the depth of penetration, and found that the depth of 
impregnation varied inversely as the viscosity. It is therefore 
essential for good penetration to work with hot preservatives, and, 
owing to the low thermal conductivity of wood, the treatment 
should not be too rapid. With the coal-tar creosote fractions, those 
of the greatest stability are the least toxic. He also showed that 
wood treated Avith saline preservatives is generally more easily 
ignited than untreated woods, but preservation makes it slow 
burning and more easily extinguishable. Coal-tar creosote and 
copperized oil had the least deleterious effect on steel. Metallic 
salts, on the other hand — e.g., zinc salts and fluorides — ^had a more 
pronounced action, while certain wood tars were highly corrosive 
owing to the presence of free acetic acid. 

Dean and Downs^ compared the fungicidal properties of coal- 
tar and water-gas creosote on Polyslictus versicolor, one of the 
common wood-rotting fungi. They foinid that coal-tar creosote 
was stronger than the water-gas product, and that the value of the 

1 Forest Service Circular 188, October 17, 1911. 

2 J. Ind. Eng. Chem., 1912, 4, 2(5G. 

=* Eighth Int. Cong. Ap^j. Chem., 1912, Section VIa. ■* Ihid. 



WOOD PRESERVATION 177 

coal tar dejaends upon the presence of tar acids and tar bases. 
Water-gas tar creosote was found to be the same as the coal-tar 
oil with the tar acids removed. 

Charitschhoff^ showed that creosotes, even when freed from all 
phenols by extraction with strong caustic soda, still exerted a 
decided germicidal and antiseptic power when tested on Merulius 
lachrymals and Penicillium glaucmn. 

A good man}^ modifications of the creosoting process have been 
called by the inventors' names, thus: 

Curtis-Isaacs : The timber and creosote are heated to above the 
boiling-point of the sap at ordinary pressure in a vessel having 
vents open to the air ; the vents are then closed, and the creosote is 
forced into the wood under pressure. 

Rueping : Compressed air is forced into the wood at a pressure 
of 80 to 100 pounds on the square inch, and then at a higher pressure 
creosote oil, without relieving the air-pressure. 

Lowry: Treatment with the oil at 77° to 82° C. at 180 pounds 
per square inch, followed by draining and a rapid vacuum treat- 
ment. 

Rutger or zinc-creosote process: An emulsion of I pound of zinc 
salt (called " dry zmc ") with |^ to 4 pounds creosote per cubic foot 
of timber is used, and is kept continually agitated. 

Guissani : Wood is heated in a mixture of melted anthracene 
and pitch to 140° C. until freed from moisture and " sap," then suc- 
cessively treated with cold, heavy tar oil, and cold zinc chloride 
solution. 

The creo-resinate process is said to be specially suitable for wood- 
paving blocks ; the wood is first heated to 121° C. in air at a pressure 
of 100 pounds per square inch, then a hot mixture of 50 parts 
creosote oil, 48 of resin, and 2 of formaldehyde is forced in, followed 
by limc-\\'ater at 100° C. and 150 ^jounds pressure. 

Although the oils are more powerful when in the concentrated 
state, much creosoting is done by steaming the dried timber before 
heating under reduced pressure, then running in the oil and raising 
the pressure to 100 to 180 pounds per square inch. Piles and wood- 
paving blocks can be readily injected with the most viscous tars to 
the extent of 15 to 20 pounds jser cubic foot. 

Many attempts have been made to diminish the cost of creosoting, 
but the result is almost inevitably to decrease the cflicienc}'.- Sucli 
would be the case with Chateau and Merklen's patent of 1907, 
impregnating with a small quantity of the agent — e.g., creosote — 

1 .7. Russ. Phys. Chcm. Soc, 1912, 44, 345. 

- See Kcmpfcr, Bull. 84, U.S. Dcpt. of Agriculture, 1911, on the lircscrvativo 
treatmont of poles. 

12 



178 DISINFECTION AND STERILIZATION 

then with a liquid like water, " which carries the disinfectant to 
all parts, thereby economizing it." 

Creosote Testing and Chaxacteristics. — Great Britain is still the 
chief producer and shipper of creosote, and should adopt a uniform 
system of testing. Tars originate from the manufacture of coal and 
water gas and coke, and give by their distillation liquids called 
collectively creosote; the word may mean a product from gas tar, 
wood tar, oil-gas tar, producer-gas tar. or coke-oven tar. Chemically 
they have great similarity in their content of aromatic hjdrocarbons ; 
we have ah-eady given Weiss's estimate of the relative antiseptic 
powers of the coal-gas oil and water-gas oil. The most imj)ortant 
difference is the absence in the latter of those oxygenated or 
phenolic compounds which occur in the former, but the water-gas 
products could be made available for wood preservation by adding 
a small percentage of crude coal-tar acids. Forrest says that a 
mixture of the water-gas and coal distillates forms the bulk of the 
creosote now used in America. 

The subject is well treated up to the date in Allen's " Commercial 
Chemical Analysis," vol. iii. There are also able papers by Charles 
N. Forrest, New York Chemist Club, November, 1910; R. Estor, 
Les Matieres Grasses, 1911, 4, 2209; E. Sage, J. Soc. Chem. Intl., 
1911, 588; and S. Collins and A. Hall, ibid.. May 15, 1914. 

Circular 98, U.S. Department of Agriculture, is on the " Quality 
and Character of Creosote in Weil-Preserved Timbers." A number 
of other bulletins deal with standard methods of testing. 

1. Specific Gravity should be taken at 60° C, as some of the pro- 
ducts are thick at lower temperatures ; Forrest's 38° and the ordinary 
15° are not so convenient as a standard. 

2. Coefficient of Expansion. — 100 c.c. at 40" C. are warmed to 
80° C. in a flask with graduated neck. Sage finds the usual increase 
of volume to be 1 per cent, for each 13-3° C. This figure is some- 
times of great importance, and it enables the specific gravity given 
at one temperature to be calculated at another. 

3. Fluidity or Condition.— Keep 100 c.c. at 15° C. for six hours, 
adding a small crystal of naj)hthalene (to avoid supersaturation) 
and stirring occasionally. Report as " fluid," " quite solid," " some 
deposit," etc., also whether it is completely liquid after keeping for 
a sj)eciflcd time at 40° C. Pastor's quoted speciflcation — '" should 
not dej)osit more than 25 per cent, of naphthalene or other product 
sohd at 15° C." — refers to difficulty in injection unless a higher tem- 
perature is used. The determination of viscosity is not so important, 
as in creosoting the presence of traces of insoluble carbon has far 
greater influence than slight differences in viscosity. 



WOOD PRESERVATION 179 

4. Solubility in Benzene. — Crude tars may contain 5 to 40 per 
cent, of matter insoluble in benzene or CS2, commercially called 
" free carbon." This would be concerned in waterproofing rather 
than in antiseptic action. Most creosotes, being distillates, contain 
little or none, and in no case should more than 0-25 per cent, be 
passed without comment. 8ome specifications say " must dissolve 
completely in benzene." 

5. Flash-Point. — Sage considers the Pensky-Marten apparatus 
more suitable than Abel's, and finds the usual point 186° to 190° C. 
It has relation to safet}' in use. 

6. Solvent Tests. — -Pitch and a great part of tar are insoluble 
in a mixture of alcohol and petroleum naphtha; creosote is mainly 
soluble. For distillates, Forrest recommends a dimethyl suljihate 
test described by Dr. Sommer as "dissolving benzene and jiyro- 
distillates, but not paraffins or olefines."^ 

7. Biological Tests with the organisms destructive to timber 
are long and difficult, but have conclusive value. 

8. Distillation. — The method is often detailed in the contracts, 
but a usual process is to distil 100 grammes in a weighed 250 c.c. 
hard glass distillation flask with the bulb of the thermometer 
opposite the end of the outlet tube. The fractions are collected in 
stoppered graduated cylinders, which are also tared for convenience. 

Water is measured in the fraction distilling under 180° C. by 
diluting Avith an equal volume of benzene to facilitate the separa- 
tion. If necessary, from the benzene solution the solvent can be 
driven off at 81° C, and the remainder separately examined. 

The main distillation is continued to 316° C, noting specially 
the volumes coming over near 205°, 215°, 220°, 245°, 271°, 300°, 
and 316° C. What remains undistilled is weighed, and is generally 
put down as " pitchy residue." Creosote does not enter timber 
easily with much pitch. 

The tar acids (and the phenoloids) are extracted from the whole 
distillate by three lots of 12 per cent, caustic soda of 25 c.c, 15 c.c, 
and 10 c.c. respectively. The soda extract is washed three times 
with ether, the ether collected and washed with 5 c.c. of soda, which 
is then added to the main soda extract; this is warmed and shaken 
till all the ether is expelled, then placed in a 200 c.c burette, cooled, 
and carefully acidified with 50 per cent, sulphuric acid. After again 
cooHng, the volume of tar acids is read off. The tar bases (pyridine, 
etc.) can be determined similarly by extraction with sulphuric acid; 
they are very antagonistic to organisms, but are volatile. 

1 J. Ind. Eng. Chem., 2, 186. 



180 DISINFECTION AND STERILIZATION 

Estor adduces two examples of French specifications for wood- 
preserving creosotes: 

French Industrial Societies. 

1. Completely liquid within thirty minutes at 40*^ C. 

2. Specific gravity at 15' C, 1-04 to 1-05; at 50^ C, 1-015. 

3. Must dissolve completely in benzene. 

4. Contain at least 10 per cent, of tar acids soluble in soda, 1-15 
sj)ecific gravity. 

5. Not to deposit more than 25 per cent, of naphthalene at 15° C. 

Campagnie des Chemins de Fer de l'Est. 

1. Si^ecific gravity not less than 1-05 at 15° C. 

2. Distillation fractions: below 150° C, less than 3 per cent.; 
150° to 235°, less than 30 per cent. ; 150° to 355°, more than 85 
per cent. 

3. At least 5 per cent, of phenols. 

4. Not more than 30 per cent, naphthalene. 

Naphthalene can be separated from the fractions boiling below 
270° C. by cooling, filtering through cloth, and pressing, and can then 
be weighed. Picric acid precipitation gives too high a result, as it 
precipitates other hydrocarbons. 

Collins and Hall^ find the best method for the assay of creosote 
is carefully to distil it, using a long (20 discs) Young's " rod and disc " 
still-head up to 271°, and then a shorter one to 316°. The naphtha- 
lene comes over between 205° and 220°, solidifies in the receivers, 
and on cooling can be weighed and the melting-point taken. They 
find crude naphthalene a splendid jDreservative for timber, but so 
much is absorbed that the expense is great. Its evaporation seems 
limited to the surface. Creosote disappears from the exposed j)or- 
tions of a post, and also from the point, but the middle part keeps 
its creosote well, as shown by tests after twelve to fourteen years. 
The more volatile portions are easily lost. While the creosote re- 
mains, the wood will be preserved. 

In the report of the Committee on Wood Preservatives (Creosote 
Oil),^ the definition of creosote oil is revised, and comprises all dis- 
tillate oils boiling between 200° and 400° C, obtained by direct dis- 
tillation from tars consisting principally of compounds of the aro- 
matic series, and containing well-defined amounts of phenoloids. 
The most important tests are for moisture, specific gravity, and 
distillation. Additional tests are for free carbon, tar acids, sul- 

^ Loc. cit. 

- Proc. Amtr. Wood Preservers' Assoc, 1014, 58-70; througli J . Hoc. Chan. Ind., 
1014, 33, 832. 



WOOD PRESERVATION 181 

phonation; the Hompol distillation tost, refractive indices, and 
specific gravities of the fractions. These tests are described in 
detail, together \Wth the apparatus employed. All temperature 
observations must be made with a standard thermometer of specified 
dimensions : length of stem from 0° to 400° C, 295 mm. ; bulb, 14 mm 
long and 6 mm. in diameter. Readings to be uncorrected. No 
recommendations have yet been formulated as to standard specifica- 
tions for creosote oils, but the specifications enforced by several 
consumers' associations are reprinted collectively for comparison. 

Leaflet No. 284 of the British Board of Agriculture, issued 1914, 
on " The Preservation of Outdoor Timber," mentions under surface 
applications that simple painting may do more harm than good, as 
the moisture is prevented from escaping, and conditions favourable 
to decay are thereby maintained. A tar coat is more or less elastic, 
and allows the contraction and expansion of wood by changes of 
temperature ; but a coating that cracks readily obviously permits the 
entrance of destructive agents. It alludes to the primordial device 
of superficial charring, in which the wood is destroyed to the de2")th of 
half an inch or so, the resins, gums, tannins, etc., contained being 
driven in front of the heat till they saturate a layer and form a 
protecting mantle to the deeper tissue, and observes that mere 
singeing or scorching will again do more harm than good, as causing 
the woad to crack and be penetrable to the dangers. The destruc- 
tion of material necessarily involves so much weakening of the 
structure, therefore " it is doubtful whether, on the whole, the char- 
ring of posts is a profitable process." 

Consequently, impregnation of wood throughout with preserva- 
tives by such processes as we have indicated is the only safe resort, 
and of these the foremost at present is the aj^plication of creosote. 
The objections stated to others, such as copper sulphate, zinc 
chloride, or corrosive sublimate, are cost, poisonousness to animals, 
liability to be washed out by water, or injurious action on metals. 
The railway companies generally specify that each cubic foot shall 
contain 1 gallon of creosote, costing at least 4d., and there is little 
advantage in increasing this quantity. One economic benefit is 
that by prolonging the life of timber for twelve to fifteen years 
it makes useful, for fencing and other purposes, much material 
that would otherwise be too perishable. Leaflet 284 gives good 
directions for the creosoting process. 



CHAPTER IX 

THE CHEMICALS EMPLOYED IN DISINFECTION 

CHEMICAL CONSTITUTION AND GERMICIDAL ACTIVITY 

This branch of therapeutic chemistry has not yet been the subject 
of any systematic treatment. Investigators in the fiekl liave been at 
once confronted with the usual difficulties that beset observers M'hen 
experiments on Hving organisms are being carried out. Confusion 
between disinfection or actual germicidal activity and antiseptic 
value has frequently arisen, and the concejit of activity and anti- 
septic value of the disinfectant has been masked by side reactions 
between the chemical investigated and extraneous matter, either 
organic, such as serum, blood, or pus, or inorganic (e.g., sodium 
chloride) present with the bacteria. Although for practical purposes 
the stability of a germicide in the presence of extraneous matter is 
usually desirable, and should be determined, yet, owing to the great 
variety of possible contaminating substances, for the purely scientific 
problem of the relationship between chemical constitution and 
germicidal activity these complications had best be avoided. 

The first point of interest in the subject is that undoubtedly 
selective action takes place ; thus not only will two different organ- 
isms show different resistances to the same germicide, but unfor- 
tunately their relative resistances to two different germicides will 
not be the same, whilst the phenomenon of gradual immunity or 
acclimatization to disinfectants introduces still another factor. 
Thus Harde and Jackson^ showed that staphylococci treated with 
1 : 200 phenol for three periods of one and a half hours each would 
then withstand 1 : 100 phenol for one and a half hours, whilst the 
untreated organisms died within three-quarters of an hour on 
immersion. Attention must be paid to the standardizing of the 
growth of a particular organism for testing purposes, and having 
defined the medium, the nature of the organism, and method of cul- 
ture, comparable results with different germicides may be obtained. 

Whilst the practical methods of testing disinfectants ^\'ill be 
dealt with later, it is important to bear the above points in mind 
when discussing the results of different observers. 

It is well known^that certain chemicals possess the power of 
1 Cotnpt. rend. Soc. Biol., 1918, 81, G35. 
182 



EFFECT OF CHEMICAL CONSTITUTION 1S3 

stimulating the growth, arresting the growth, and finally destroying 
the growth of different micro-organisms with increasing concentra- 
tions of those reagents, properties utilized in culture growing, 
antisepsis, and disinfection respectively. 

Under the usual conditions of testing where solutions are made 
use of, the germicide may be in solution or in the colloidal state in 
the medium, and any theory of disinfection which is applicable to 
ionized solutions must be also capable of extension to non-ionized 
solutions, emulsions, and other colloidal sj'stems. 

Bacterial Suspensions. — An emulsion of bacteria is not, strictly 
speaking, an emulsion at all. A micro-organism, of which the 
average diameter, excepting the ultra-microscopic bacteria, is about 
1 to 1-5 fj., is composed of a chitin envelope^ containing, in addition to 
organic compounds of high molecular weight, which consist of poly- 
peptides, lipoids, and carbohydrates, also enzymes, as well as salts, 
chiefly sodium chloride, in strength approximating to that of phj-sio- 
logical salt solutions, together wdth a cell nucleus containing the 
chromospores and chromosomes of unkno\\Ti chemical constitution. 
We must rather regard the " emulsion " as tying between a suspen- 
sion and a suspensoid in size. Practically all bacteria wdll exhibit 
Brownian movement, and may therefore be regarded as of colloidal 
diameter. The bacteria are feebly precipitated by cations ; thus 
hydrion and the polyvalent elements, iron and aluminium, as well 
as the heavy metals, mercury, copper, and silver, precipitate them, 
but they are practically unaffected by the alkali and alkaline earth 
cations. In this respect — ^namely, insensibility to a great number 
of cations — they resemble emulsoids rather than suspensoids. A 
further resemblance is sho\\Ti in that bacteria are but feeblj' protected 
from precipitation by the ordinary protective coUoids such as gelatine 
and isinglass. It is therefore more legitimate to regard bacterial 
suspensions as suspensoid nuclei coated by or containing an emulsoid. 

If we add to a suspension of bacteria serum taken from an inocu- 
lated animal, we obtain agglutin bacteria complexes. These have 
entirely lost their emulsoid properties, and exhibit the properties of 
suspensoids. 

The reaction between agglutin and the bacteria, similar to the 
reaction between toxin and antitoxin, resembles in many respects 
either the combination of a very weak acid and a weak base, the 
excess of either constituent, when equilibrium has been attained, 
being given by the general equation — 

CjCg = KC3, 

^ Cellulose, liemicclluloses, and carbohydrates of the pentosan group are, 
however, present in the cell walls of many fungi, whilst with certain aniwba the 
cell wall appears to be lacking. 



184 DISINFECTION AND STERILIZATION 

where C^, Cg, C3 are the concentrations of the reacting constituents. 
This view has been advanced and supported by Arrhenius (Immuno- 
chemie), but may also be interpreted equally well on the usual absorji- 
tion fornnila — 

p='=Aa'' 

in cases where n is near unity. Experimental evidence is not suffi- 
ciently accurate to distinguish between the two. 

Recent Mork^ has gone far to indicate that the usual adsorption 
formula has no theoretical significance, and that there is no differ 
ence in mechanism between physical and chemical adsorption for 
dilute concentrations; if concentrated solutions be used, there is a 
]3ossibility that the substance adsorbed may build up a second or 
more layers above the more firmly adhering single layer, and thus 
give rise to the " adsorption " formula. The Danysz effect must 
be regarded as a phenomenon of this kind. 

The conditions determining physical adsorption, and especially 
the influence of electrical charges on suspensoids, have been discussed 
more especially by Freundlich,- W. Gibbs,^ Pawlow,* Donnan, l^an- 
croft, and others. It may be noted that suspensioiis of bacteria 
always acquire an electric charge. 

A very sharp distinction between these reactions and ordinary 
weak acid base neutralization is the specific nature of the reaction. 
Each toxin requires its own particular antitoxin, and each bacteria 
species its own agglutin. This, of course, is characteristic of enzyme 
reaction, and the usual example cited — namely, "a key for every 
lock " — holds good. 

We can thus distinguish between the following types of action : 

1. Absorption of cations (ionic disinfectants), with simultaneous 
absorption of anions which may affect the activity. 

2. Mutual action between two colloids (reactions between emulsi- 
fied disinfectants and organisms). 

In this connection, although mutual absorption is said to take 
place, the mechanism may also be regarded as one of " protection," 
for the folloAving reasons : 

The finer the emulsion, the more efficient the germicide. This 
is directly observable under the microscope; solutions are not so 
germicidal. 

Taking the diameter of an average organism as 1-0/^ diameter, 
and assuming approximately spherical shape, we require 10,000 

1 Langinuir, J. Amcr. Chem. Soc, 1913; Williams, Proc. Roy.Soc, November, 
1919, 287. ^ KapUlarchemie. 

3 Scientific rai)or.s, 2. * Zeitsch. Physikal. Chem. 



EFFECT OF CHEMICAL CONSTITUTION 185 

molecules to coat the organism Mith a molecular thickness of the 
emulsified disinfectant; 10.000 molecules in the spherical form 
have a diameter of 0-15 /x, which is the lowest limit of direct visibiHty. 
Now the ratio of volume and weight of organism to emulsion particle 
is as 1 to 0-001 a]iproximately. Zzigmoncly has found that the 
weights of protective gelatine to gold is as 0-001 to 1. It therefore 
appears that the relationship may be of significance, and that the 
most desirable emulsoid disinfectant will be a protective colloid 
to the organism. From these considerations it is at once evident 
that an emulsion of, say, a cresol in water may be more powerfully 
germicidol than the same amount of cresol in .solution. 

3. Direct absorption of non-ionized substances in solution. 

The adsorption of phenol by anthrax and the partition of phenol 
between water and organisms has been found to obey the regular 
adsorption law.^ Alterations in the surface tension of proteins 
and sera b;v the addition of phenol and water indicate also the adsorp- 
tion of jihenol. A point to be noted, and one not usually recognized, 
"is that the degree of adsorption is dependent on the degree of curva- 
ture of the envelope. With decreasing size — i.e., increased curva- 
ture — the adsorption must get less, since in the limiting case the solu- 
tion must become uniform in composition. 

Animal charcoal has long been used as an adsorbant for micro- 
organisms, and when fresh and " active," especially those varieties 
prepared for gas masks, it undoubtedly removes micro-organisms 
and their ferments. I In the Vienna hosjDital it was found that proteo- 
lytic ferment produced by B. pyocynneus was completely adsorbed, 
and that a bacterial suspension shaken with fresh charcoal was ren- 
dered completely sterile. Methods of wound treatment were like- 
wise elaborated during the war, usually consisting of a preliminary 
washing with hydrogen peroxide, followed by dry dressings of char- 
coal changed every day. Deep wounds were s^Tinged with a 2 to 3 
per cent, suspension of charcoal. It is stated- that the method 
proved successful, and that no ill effects were observed. 

When we infjuire a little more closely into the mechanism of dis- 
infection, instead of referring it purely to "adsorption," irrespective 
of the germicidal activity of the substance adsorbed, we are at once 
confronted with a variety of hypotheses as to the nature of the forces 
involved."' 

The early experiments of de Vries on plasmolysis of jilant cells 
(especially tradescantia) and of Hamburger on plasmolysis of the 
red blood-corpuscles indicated quite clearly that many substances 

^ Kiister and Bojakowsky, Disinfekiion, IDl'i. 5, I'.KJ. 

2 Brit. Med. ./., June 19, 1917. 

* Jahreshuch. Jiir iviss. Bol., 1H84, 14. 



186 DISINFECTION AND STERILIZATION 

could not difTuso into tho interior of tlio colls, -whilst others could. 
The work of de Vrics on both non-permeable electrolytes and non- 
electrolytes was, in fact, the starting-point of the present concept of 
osmosis and the theories of solution (for which we are chiefly in- 
debted to Van't Hoff and Arrhenius). 

The peculiarly selective action of blood-corpuscles in their permea- 
bility to substances was investigated in detail by Gryns,^ Avho 
showed that the sodium salts of the following acids: HCl, HBr, 
HE, H2SO4, CH3COOH, CH.,-CH2-C00H, and the ammonium salts 
of HNO3, H2SO4. HCNS, HgPOj. were not permeable in the blood- 
corpuscles, Avhilst the ammonium salts of HCl, HBr, HI, HF, HBO3, 
CHj'COOH readily penetrated. Hedin,^ by determining the rela- 
tive lowering of the freezing-points of equal volumes of serum and 
blood on addition of equal amounts of the various salts, investigated 
whether the serum or the blood adsorbed the salt more easily. In 
the case of the alkali salts an equal adsorption was noted, and simi- 
larly with sugars, alcohols, and amino-acids and some aldehydes, 
whilst ketones, ethers, and esters were more strongly adsorbed b}' 
the blood than by the serum. 

Overton and H. Meyer, ^ in their studies on narcosis, were more 
successful than these former observers in correlating permeability 
with other physical properties. They proved that narcosis was pro- 
duced by readily permeable substances such as ether, chloroform, 
and strychnine, which also, on account of their permeability, pro- 
duced no plasmolysis. This striking result at once brought up the 
question in an acute form as to why the cell was permeable to some 
very large molecules like strychnine and impermeable to some very 
small ones such as the ions of the simple salts. Overton attributed 
this lack of permeability of certain substances in part to chemical 
reaction with the cell wall, but at the same time considered even more 
important the interesting fact that permeable substances were soluble 
in fats, fat solvents, and lipoids, and relatively insoluble in water, 
whilst the impermeable substances were relatively very soluble 
in water and lipoids. Thus special emphasis was laid upon the value 
of the partition coefficient — 

„ _ solubility in oil, fat, or lipoid 

"solubility in environment, water, or serum* 

Large values for K, the partition coefficient, would indicate a pene- 
tratable substance and an effective agent, which Avould readily dis- 

^ Pfluger's Archiv, 63. 
2 Ibid., 68. 

=» Viertdjahrschrift der Naturs fors., Zurich, 1895, 189G, 1899; Siudien iiber 
Narkose, 1901. 



EFFECT OF CHEMICAL CONSTITUTION 187 

solve in the lipoid material of the cell and affect the vitalit}' of the 

organism. 

NIT 
Thus urea, CO<^TyjTT^ penetrates into the cell AvaU with extreme 

slowness, but by replacing the hydrogens by alkyl or even aryl 
groupings the rate of permeation increases very considerably ; simul- 
taneously there is an increase in the ether solubility. 

Oxygen-free alkaloids penetrate with readiness and are fat soluble, 
but their salts do not diffuse, and at the same time are fat insoluble. 

Ether soluble basic dyes penetrate with ease, whilst the water 
soluble sulphonated dyes do not. Germicides such as mercuric 
chloride, iodine, and formic acid are appreciably fat soluble. 
Attemjits^ to convert non-trypanocidal metals such as copper or 
silver into trypanocidal agents by combining them with a lipoid 
soluble group such as acetic ester or peptone yielded, however, 
negative results. 

Numerous investigations on yeast cells, such as those of Herzog 
and BetzeP and GossP have shown a very close connection between 
antiseptic disinfecting power and lipoid or protein solubilit3^ It is 
of interest to note that lipoid soluble substances will be absorbed by 
dead as well as living cells, and thus adsorjjtion is not diagnostic 
of life in the cell. Further, that death does not always result from 
such adsorption or lipoid solution, since the aliphatic and hydro- 
aromatic hydrocarbons possess a large partition coefficient, but are 
not germicidal. The action of sodium chloride in elevating the germi- 
cidal activity of phenol and of alcohol in depressing it can be attrib- 
uted to the alteration of the —^ — partition coefficient, the former 

water ^ ' 

elevating it by decreasing the solubility of the phenol in water, and 
the latter lowering it by increasing the Avater solubilitj\ The 
germicidal power of phenol in such solutions is directly proportional 
to the activity or fugacity of the j^henol. Salts affect the germicidal 
powers of phenol to different extents ; thus in order of increasing 
activity are KNO3, KI, NH.Cl, KBr, KCl, NaCl. 

As has already been pointed out, | adsorption by the colloid 
appears to be the primary action in disinfection, and the factors 
governing this adsorption must influence the germicidal activity of a 
disinfectant J The influence of electric charge has already been noted , 
but of even greater significance is the influence of the germicide on 
the surface tension of the medium. ' It was shown by Willard Gibbs 
that in those cases where the solute lowered the surface tension of a 
solvent the solution would be more concentrated at the surface than in 

^ Archiv. Iiiternat. de Pharmacodynamie de Therapie, No. 3, 1913, 12, 73. 

2 Hoppe-Seyler. Zeit.'^ch. Physinl. Chem., 1910,67, 309; 1911.74, 221. 

Vi-oc. cj<., 1913, 88, 103. 



188 DISINFECTION AND STERILIZATION 

bulk; thiis round each luicro-nri^raiiisiu thoro will exist a film of 
medium richer in germicide than the bulk of the medium. We can 
thus postulate that efficient germicides wdll lower the surface tension 
of the medium in which the organisms are dispersed.! 

This rclationshi]) l)etween the lowering of the surface tension 
and the germicidal activity is very well exemplified in the someA\hat 
insoluble organic hydroxyl derivatives. Thus thj^mol, cami^hor. 
and menthol exert a greater depressing action than the cresols, and 
cresol than ]ihenol, on the surface tension of the water, and the same 
order is found in their molar germicidal activity. Phenol is niore 
effective than resorcin, resorcin than hydroc|uinone, this latter than 
phloroglucin and pyrogallol in both respects. 

A remarkable correlation is found in the nitrophenols and nitro- 
benzaldehydes ; in the former the para position is stronger than the 
ortho, and in the latter the converse is true. Their action on the 
surface tension of water follows in the same order. 

The hydrocarbons possessing a high lipoid water jiartition co- 
efficient have an almost negligible germicidal activity, and scarcely 
affect the surface tension of the water. 

Brow^n and Tinker have likewise shown^ that in the case of barley 
seeds immersed in dilute aqueous phenol there is a direct relationship 
between the adsorption and the surface tension. 

From the physical standpoint there are thus two criteria which 
may be applied to test the efficiency of a germicide — the partition 
coefficient between a fat or liquid and the medium, and the effect 
of the germicide on the surface tension of the medium. These facts 
alone are, however, not sufficient to account for the anomalous cases 
of permeability noted by De Vries, Hamburger, and Overton. This 
latter observer somewhat modified his earlier physical theory' by 
postulating the existence of active groupings which inhibited per- 
meability, and thus promoted plasmolysis. Ionized substances do 
not permeate with readiness, whilst substances like aniline, aldehydes, 
methyl alcohol, acetone, and phenol do. In the case of glycerol, 
succinimide, and acetamide plasmolysis will set in to commence 
with, but afterwards disappear, indicating a slow diffusivity. In 
decreasing order of diffusivity or extended period of plasmolysis 
can be mentioned gh'cerine. urea, and, slowest of all, erythrose. 

It is thus evident that the metals existing in the form of ions in 
solution as simple salts can be made to diffuse into the interior of 
the cell by means of a complex attached to the ion; thus we find 
certain organic mercurials much more germicidal than mercuric 
chloride for the same concentration of mercury. 
By simple substitution of various groupings in 2:)ermeable organic 
1 Proc. Roy. Soc, 1915, 389. ^ j^^^. cit. 



EFFECT OF CHEMICAL CONSTITUTION 189 

substances Overton^ was able to show that certain groupings retarded 
the rate of permeation very considerably, and frequently made the 
compound completely plasmolytic. In order of decreasing activity 
he noted the following: Amido-acid group, carbonyl, acetamide, 
alcoholic hydroxyl, aldehyde. 

Thus glycocoll, alanin, and leucin, containing an amido-acid 
grouping, do not penetrate the cell ai^preciably ; one hydroxyl 
scarcely hinders penetration, although CH3CH(01I)CO.NH2, lacta- 
mide, penetrates far less readily than acetamide or propionamide. 
With the introduction of further hydroxyl groups penetration is 
much slower, as is instanced by ethylene- or propylene-glycol, 
glycerol, erythrose, and the pentoses and hexoses, which do not 
penetrate at all. 

Ketone, ester, ether, halogen substitution, and nitrile groupings 
appear to have little effect on the permeability. 

Of significance is the fact that ammonia and the amines pene- 
trate with readiness, whilst the quaternary nitrogen bases do not. 
Pyridine, quinoline, piperidine, and oxygen-free alkaloids are per- 
meable, whilst oxygen-containing alkaloids usually do not j)ene- 
trate. Butschli showed that only certain dyes, such as carmine 
and haematoxyline, were capable of staining the bacterial nucleus, 
and were thus permeable. This observation has been confirmed 
and considerably extended in the development of specified reagents 
for the treatment of trypanosomic and similar infections. 

In addition to the conditions necessary to bring about surface 
adsorption, with subsequent surface reaction or penetrj?tion of the 
cell, we have the specific toxicity pf the substance or of certain groups 
in the substance to consider. Whilst the above short review of the 
former factors indicate that something, if indeed but little, is known, 
it is clear that the relationship betA\'een germicidal activity per se 
and constitution is as yet practically an unworked field. This is 
in part due to the fact that pharmaceutical preparations have usually 
an ulterior motive, such as the possession of a narcotic, sedative, 
or other activity, germicidal activity being itself usually merely a 
desirable auxiliary, and in part due to the discrepancy of results 
obtained by utilization of non-uniform methods of testing, confusion 
between antiseptic and germicidal activity, the complications intro- 
duced by the considerations noted above, as \\'ell as the ])ronounced 
selective action shown by many substances. 

Certain generalizations may be formulated, to which, how ever, 
there are the inevitable exceptions. 

In the case of the simple ionized acids, bases, and salts certain 
regularities are apparent. 

^ Loc. cit. 



laS DISINFECTION AND STERILIZATION 



J. Blake^ pointed out that in isomorphous groups the toxicity . 
increased with the atomic weight, whilst a variation in the anions of 
metallic salts had but little effect on the toxicity. In the case of the 
non-metals this relationship does not hold ; thus in the case of the 
halogens the toxicity appears to increase in the order I,, Br,, CI25 
and for the sodium halides NaCl, NaBr, Nal, and NaF. 

iihe valency of the metallic ion is also an important factor in 
germicidal activity; thus trivalent ions are more jiotent than di- 
valent, divalent than monovalent ions. [ Again, unsaturation aug- 
ments the germicidal power; thus trivalent arsenic is a much more 
efficient spiriUocide than pentavalent, as are the stibnites as com- 
pared with the stibnates. An interesting fact noted by Loeb- is 
that the presence of a divalent ion ^dll promote the activity of a 
monovalent ion, a t3'pical case of promoter action. In the case of 
ionized disinfectants such as calomel HgaClg, Dresner^ was the first 
to note that the greater the concentration of mercury in solution, the 
greater was its action on yeast cells; the observation was confirmed 
by Scheurlen and Spiro* who showed that the toxicity of certain mer- 
cury compounds decreased in the following order: HgClg, Hg(CN)2, 
Hg(CHS).2, KaHgfSaOa).}, this last being scarcely antiseptic. It 
remained, however, for Kronig and Paul^ to explain these results 
in the light of the ionic theory. These observers showed that in the 
case of simple salts the germicidal activity, as measured by the agate 
method (see ChapterXIII.), was directly projiortional to the ionic 
concentration of the cation. A very large number of experiments 
were carried out, and this rule was found to hold in practically all 
jcases, especially for the following germicidal ions : Hg, Ag, Aii, Cii, Fe. 

Thus they found the germicidal activity of mercuric chloride 
depressed by the addition of the common ion CI, as is evident by 
the following figures from experiments on anthrax spores : 

Solution. Organisms Alive after Six Minutes. 

HgCl2+ 8 

INaCl . . 32 

2NaCl 124 

3NaCl 282 

4NaCl 882 

6NaCl 803 

lONaCl 1,087 

The addition of other anions forming less dissociated salts than 
the chloride in the solution likewise brought about a decrease in the 
germicidal activity, as shown in the following table: 

* Proc. Roy. Soc, B, 1881. 14, 1299. ~ I'fliigcr's Archiv, 88, 68; 93, 246; 96, 248. 
3 Archiv. Exp. Path. Pharm., 1893, 32, 406. 

* Munch. Med. Wochenschr., 1897, 4. 

* Zcitsch. Physikal. Chcin., 21, 419; Zeilsch. Uyg., 25, 1. 



EFFECT OF CHEMICAL CONSTITUTION 



191 



Solution. 




Organisms Alive after 
Ninety Minutes. 


HgClg 1 gramme 


mol./16 litres . . 





+ 4NaCl 


• • • • • • 





4KBr 


• • • • • • 





4KCN.S 


• • • • • • 


173 


4KI .. 




431 


4KCN 


, , , , . . 


795 



Here, again, the germicidal action falls off with decreasing ionic 
concentration. Scheurlen and Sjiiro^ give the following figures for 
the iron salts AWth B. typhosus : 





Organisms Alive after — 


Solution. 


One 
Minute. 


Ten 
Minutes. 


Tivo 
Hotirs. 


Twenty- 
four Hours. 


1 per cent, ferric chloride 

1'71 per cent, potas.sium ferro- 

cyanide . . 
1'71 per cent, ferrous sulphate . . 
2*00 per cent, potassium ferro- 

cyanide . . 




600 
100 

800 




700 


800 




600 


700 




800 


800 



It is important to note that germicidal value is measured in 
these experiments, and not antiseptic power. For the hydrogen ion 
present in dissociated acids the generalization of Krcnig and Paul 
does not hold with great rigidity. The work of Horrocks and Kita- 
sato on the germicidal activities of acids indicated that their dis- 
infectant action was roughly proportional to their strength- — i.e. 
their hydrogen-ion concentration — in equal dilutions. Kahlenberg 
knd True-, HeakP and True* came to somewhat similar results with 
experiments on the toxicity of acids to the seeds of plants such as 
Lupinus alhus. Clarke""' and Stevens" found in the case of fungi that 
the fungicidal power of an acid was in several cases not propor- 
tional to the acid strength; thus acetic acid and the chloracetic 
acids were found to be more effective than h3^drochloric acid. 

These conclusions have been repeatedly confirmed by other 
observers^; Crozier came to the conclusion that the " penetrative" 
power of an acid, as measured by the colour change effected on 
the blue integumentary pigment of Cltromodoris zebra, was a function 
of its ionization as well as the possibility of union of the acid with 
one of the constituents of the cell wall ; in weak monobasic fatty acids 
this constituent is of a fatty nature. 



^ Loc. cit. 

* Amer. J. Sc, 9. 



2 Bot. Gaz., 1896, 22. 
5 Bot. Gaz., 58. 



3 Ibid. 
8 Ibid., 26. 



7 See Haas, J, Biol. C'hem., 1916, 27, 225; Crozier, ibid., 26, 217- 



192 DISINFECTION AND STERILIZATION 

Paul and Kronig/ in the course of their investigation wit li anthrax 
spores, noted that in completely ionized dilute acids there was 
scarcely any selective effect due to the anion, but Avith stronger solu- 
tions the germicidal power was by no means proportional to the 
hydrogen ion concentration ; marked anion effects were noted in the 
case of hydrofluoric, nitric, hj'drochloric, and oxalic acids, which 
were all found to be abnormally strong germicides. 

Norton- not only showed that the addition of a common ion 
generally lowered the germicidal activity of an acid[ as is to be antici- 
pated on Kronig and Paul's hypothesis of ionic activity, 'but that 
the addition of other salts frequently raised the germicidal strength ; ' 
he regards the anions as positive catalysts, and the undissociated 
molecules as negative catalysts for the rate of germicidal action 
(see Chapter XII.). These results are also, of course, caj)able of a 
tentative explanation on the salting out effect or partition coefK- 
cient theory of Overton. In addition it should be noted that for rela- 
tively concentrated solutions the differences between the thermo- 
dynamic and actual concentrations may be quite marked (see p. 187). 

The activity of the hydroxyl ion is some five times less than that 
of the hydrogen ion; thus Kronig and Paul showed that the strong 
alkalies KOH, NaOH, LiOH were practically equally effective, the 
feebly dissociated ammonium hydroxide being far less germicidal, 
its antiseptic i:»ower being only one-seventh that of caustic soda. 
For non-ionized disinfectants the joroblem is somewhat complicated 
by other factors such as penetration or impermeability to the cell 
wall, which we have seen is partly governed by the j)ossession of a 
high lipoid-water partition ratio, a marked depression on the surface 
tension of the medium, and the absence of certain specific groupings. 

O. Loew adopted the theory that the organism itself, especially 
in the cell wall, possessed certain groupings with which the disinfec- 
tant reacted; this point of view merely supjolements Overton's 
theory that the disinfectant may possess certain groups which 
react with the organism; the nature of the groupings postulated 
by these different observers is, however, somewhat different. 
Loew confines himself to the amido, — NHg, and aldehyde grouj)ings 
which are the active groups in the living cell organism and in proto- 
plasm to which the disinfectant molecule must attach itself. These 
groups are extremely reactive or labile, especially A\'ith other amido, 
aldehyde, or hydrogen groupings. Thus hydrazine, NH, — NHo, 
possesses a higher germicidal power than NH3, phenyl hydra- 
zine, CgHj.NlI.NHa, than aniline, CgHg.NHg. Phenyl urea, 

NH 
CO<CvrxT^ r FT ^^ ^^ antiseptic as sublimate, but dij)henyl urea, 

^ Luc. cil. ' J . Inject. Dincudcn, I'JIO, 18, 2. 



EFFECT OF CHEMICAL CONSTITUTION 193 

CO<^T^TTT ■ ri^xT^ possesses scarcely any antiseptic action. Likewise 

an increase of activity has been noted in the following substances, 
the last being least active : 

Unsaturated compounds with these groupings are likewise 
more reactive than saturated ones; thus a marked decrease in 
germicidal activity is noted in the following : 

ICiCI > IHC:CHI > CHI3. 

The work of Emil Fischer on the activity of various organisms 
on the sugars went far to support Locav's theory of specific chemical 
groupings in the organism to which the reactant attached itself. 
This point of view was strongly emphasized and extended by Ehrlich 
in his work on tryj^anocides (see later). 

A path to the solution of the problem of correlation of chemical 
activity and these factors has, however, been indicated by a study 
of the relationship between chemical constitution and surface 
tension, esi^eciallj' by the late Lord Rayleigh,^ Milner,- Marcelin,^ 
and Langmuir.* 

It seems probable that, since the introduction of certain 
groupings such as -OH, >C0, and -COOH, or of a double or 
treble bond into an organic hydrocarbon molecule renders the 
substance more soluble in water, these groupings react with the 
water by secondarj^ valencies or oxonium linkages, whilst the hjxlro- 
carbons do not. 

CHo CHo 

I I 

CHg CHo 

I " r 

COOH COOH 

Thus if a fatty acid be distributed over the surface of the water, 
the carboxyl groups A\i.ll be immersed in the water and tend to pull 
in the hydrocarbon nucleus Avhich is not wetted. Short hydro- 
carbon chains can be totally immersed by tlie active grouping, and 
the substance becomes soluble (e.g., CH3.OH, CH3.COOH), whilst 
the reactive grouping has usually not enough energy to pull in very 
long chains {e.g., oleic acid). We have thus direct evidence that 

1 /'/(//. Mag., 1899. 48, 331. - Ihid.. 19f>7. 13, 9f). 

3 Ann. Phys., 1914, 1, 19. 

* Proc. Nat. Acad., Washington. 1917. 3, i'ni. 

13 



194 DISINFECTION AND STERILIZATION 

ihe surface films consist of orientated molecules, and tlrat solubility 
in various solvents such as lipoids, nuclein, water, or serum is con- 
ditioned by the presence of certain particular groupings in the mole- 
cule.l Overton's partition theory, the hypothesis of surface tension 
activity, and the Loew-Ehrlich theory of the presence of particular 
chemotroj)ic groupings in the organism and parasito- or microbo- 
tropic groupings in the disinfectant are thus brought into unison 
by the adoption of this physico-chemical hj^othesis of molecular 
orientation. 

The manner in which the normal metabolic functions of the 
organism are destroyed by the germicide is unknown. We have 
already noted that many physical and physico-chemical factors 
are involved in the process of disinfection, reactions proceeding 
prior to death. The view generally advanced as to the final action 
of the germicide in causing death by precipitation or coagulation of 
some protein constituent in the organism is probably not universally 
applicable to all germicides. This hj-jDothesis is, hoAvever, of utilitj' 
in that it visualizes the dynamic nature of the process. Thus a 
small concentration of the germicide within the organism will cause 
a little coagulation to take place; the metabolic activity of the organ- 
ism will naturally increase in order to reject or repeptize the coagu- 
lated material, and it appears likely that a general and not limited 
augmentation in activity will take place, giving rise to the pheno- 
menon of growth stimulation. With increasing concentrations of 
the poison all the activities of the organism will be devoted to its 
removal, and growth arrest or antisepsis will result; finally, the 
mechanism of the organism will break down and death will occur. 
This hypothesis, however, is limited to disinfectants jaermeating 
the cell wall and reacting with a protein constituent inside] but as 
we have already had occasion to note, lipoid-soluble substances 
are frequently germicidal, but it is doubtful if in every case these 
germicides coagulate proteins^ whilst still a third type of reaction is 
to be noted in many germicides, which attack the cell wall alone, and 
either combine with it or cause precipitation and flocculation of the 
organisms, thus interfering A\ith the osmotic circulation of the 
living cell. The metal ions are thus found to be the most effective 
germicides for spores.^ 

These considerations permit us to draw some interesting deduc- 
tions; thus in the emulsified disinfectants the protective action of 
the emulsion is enhanced if the emulsion contains parasitotropic 
o-roupings. Thus, although gelatine itself has but a feeble protective 
action, the incorporation in the gelatine or the conversion of part of 
the gelatine molecuk^ into a parasitotropic grouping which reacts 

1 Chick and Martin, ,/. Ilyg., 1908 



EFFECT OF CHEMICAL CONSTITUTION 195 

with eitlier a protein or cellulose constituent of the organism 
enhances the protective action, but the protective action is really 
an enemj' in disguise, for the protector then kills the organism. In 
some ways the problem is analogous to the action of mordants in 
dyeing. 

The absorption of non-ionized disinfectants can also be made 
more complete and rapid by similar means. For example, a 1 per 
cent, chlorine solution has an R.W. figure of about 2-2, but chlora- 
mine, NH^Cl, which not only oxidizes, but possesses the -NIL, 
group — a group reactive with cellulose or chitin — has for the same 
1 per cent, chlorine an R.W. figure of 6-6, being thus three times 
as strong. 






V V 



:. b I 



-^ ^\ C3- W^ ^^ 



CHAPTER X 
THE CHEMICALS EMPLOYED IN DISINFECTION— Con/mweri 

INORGANIC SUBSTANCES. 

These may be broadly classified as (a) non-metallic ; [h) derivatives 
of metals. 

(A) Non-Metallic Substances. 

Ozone. — Ordinary oxygen acts slowly by the aid of aerobic 
organisms. Its activity is slightly increased by compression, 
but it becomes extremely energetic when converted into its 
allotropic form, ozone (O3), formed most conveniently by passing 
an electrical discharge through ordinary air. Since ozone is 
decomposed by heat, by most metals, and by otherwise inert 
organic matter, the chief conditions for efficient working are: 
(1) The production of a silent electrical discharge without 
sparking; (2) keeping the gas and the apparatus cool; (3) straining 
the air, and also partially drying when it is desirable to prevent 
the formation of oxides of nitrogen; (4) parts in contact with 
ozone must be made of, or lined with, unoxidizable materials; 
(5)' the grosser organic impurities, as well as sulphuretted 
hydrogen and ferrous iron, should be removed before disinfec- 
tion. The use of ozone on a large scale for purifying water and 
sewage is now well known (see ante), and the principal types of 
apparatus for the purpose have been described by Don^ and 
by the Avriters.- In the dry state, like chlorine, it has very little 
action on micro-organisms, and therefore does not act powerfully 
on bacilli in air. Some American experiments, however, seem to 
show that 8 grammes per cubic metre of air in a room ordinarily 
closed attain disinfection in three hours (see ante); whilst Heise^ 
has found that 95 per cent, of the bacteria on the surface of a 
culture medium are killed in a similar period by concentrations of 
3 grammes per cubic metre. Its use as an adjunct to ventilation 
has often been proposed, but its irritant action on the lungs, its low 

^ Inst. Mechan. EiiyincerH, January and February, 1909; " Modern Methods 
of Water Purification," by J. Don and J. Chisholm. Edward Arnold. 

2 " Water Supplies." 

3 Arbeit. Kais. Gesundh., 1917, 50, 4IS; Chrw. Zdl., 191S, 42, 137. 

190 



INORGANIC SUBSTANCES 197 

penetrative power, and ease of decomposition are grave defects. 
All observers have found that Avhen moist it is a very powerful 
germicide. Ozonized air under pressure has been used successfully 
for destroying moulds and bacteria in brew^ers' foul casks, and has 
been introduced into wort in the later part of the fermentation " to 
destroy noxious germs. "^ On account of its rapid consumption 
by oxidizable substances, it can only be effective in disinfecting 
the surfaces of organic solids. A large plant has been in operation 
for some time at the Pittsburg Homeopathic Hospital for purifying 
the water supply, and also for sterilizing instruments, bandages, etc., 
and for dressing Avounds and ulcers. In cold storage, it would prob- 
ably be useful for destroying injurious organisms and odours, thereby 
possibly lessening the amount of refrigeration required. Many 
attempts have been made to utilize it for disinfecting, combined 
with bleaching, textiles, feathers, and other surface-contaminated 
articles, and have been only limited by questions of expense. 

Hydrogen Peroxide. — ^The earlier experiments showed that this 
was a bactericide which appeared inert to enzymes^ such as diastase, 
ptyalin, pepsin, and pancreatin, and did not injure foods. It is 
also innocuous and non-corrosive. These properties suggested 
its use for killing pathogenic organisms, and those that caused change 
in articles of diet, especially milk, and also as an internal disinfectant. 
Altehoefer^ and most later observers state 1 per 1,000 of H-^Oj is 
required to destroy ]mthogenic organisms in twenty-four hours. 
In 1903 the writers found that in milk raised to 50" C, then treated 
with 0-6 gramme of HgOg per litre, and the temperature maintained 
at 52° to 55° C. for eight hours, pathogenic organisms, and even 
the spores of B. anthracis a,nd suhtilis, were killed; the milk was not 
physically altered, and kept for over a month unchanged in closed^ 
receptacles. Hydrogen peroxide thus aids j)asteurization and 
enables it to be efficient at a lower temperature. Similar results 
have been obtained by Lewin and others, and by Hewlett.^ 

Peroxide of hydrogen is j^rcsent in sanitas [q.v.). Perhydrol 
is a 30 per cent, or '" 100 volume " solution of HgO.,. The use of 
peroxide of hydrogen in medicine depends partly on its bacterial 
action. Registered names of solutions are dioxof/en (3 per cent.), 
hydrozone, glycozone (in glycerine), and jjyrozotie (dental i)raetice). 

1 Patent 22,355 of 1898. 

- The catalytic enzymes present in malt, yeast, milk, and many organic liquids, 
mutually decompose one another (Van Laer, J. Soc. Chem. Ind., 1906, 
4.39. 550; 1909, 550), but the above statement remains practically true (see also 
ibid., 1909, 1267). 

3 Cenir. Bukt., 1890, 8, 129. See also Bruns {Bed. Klin. Wucheiuich., 1900, 
19), Paneth, Bokorny and Paul, and Kronig {loc. cit.). 

* Lancet, January 27, 1906. 



198 DISINFECTION AND STERILIZATION 

Peroxides of sodium, magnesium {Iwpogen, biogen), zinc {ecioyan 
or dermogen), and mercury generate oxygen or HgOg, and have 
analogous use. It is more stable in ether than in water; ozonic 
ether is an ethereal solution containing about 1-2 per cent, of HoOj, 
which has been used in whooping-cough and scarlet fever. 

Nitric Acid and Oxides of Nitrogen. — ^The corrosive action of nitric 
acid limits its value as an active disinfectant, although, in common 
with all strongly dissociated acids, it is an effective germicide ; the 
anion appears to exert a slight specific activity in solution. Behring^ 
gives 0-26 ^^er cent, as the antiseptic concentration for anthrax 
spores in blood-serum. Paul and Kronig- place it second to hydro- 
fluoric acid in activity on anthrax spores, 1 gramme molecule per 
litre effectively sterilizing in less than two hours. Dr. J. C. Smith 
used it with success in 1780 for fumigation in a violent outbreak 
of typhus fever in the British Fleet. ^ Dismfection of rooms by 
nitrogen peroxide was carried out during the siege of Paris; forty- 
eight hours was required, and the cost was very high. Severe bron- 
chitis and several deaths from poisoning have resulted from 
breathing this gas, and nitric disinfection has been replaced by 
safer methods, except in the local destruction of bacteria, as in 
laboratories. 

According to Heinz* nitrous acid is a much stronger germicide 
than nitric acid, in spite of the fact that it is a very much weaker 
acid, a dilution of 1 : 100,000 being already toxic to algae and many 
bacteria. Its potency must be ascribed to the reactivity of the acid 
and salts Avith the -NHo group of the cell organism. 

Sulphur. — The uses of sulphur as a fungicide have already been 
referred to. The application of sulphur internally is due to its 
forming sulphuretted hydrogen in the system, and thereby destroy- 
ing or enfeebling micro-organisms and higher parasites; it possesses 
the further advantage for internal uses in that it is a phagocytic 
stimulant. 

Sulphur dioxide disinfection is still a subject of controversy, 
but certain of the unfavourable results adduced have been due to 
faulty application. Some of the discrepancies may be explained 
by the observations of Klein and Wynter Blyth, that while most 
pathogenic microbes do not thrive in an acid medium, some organisms 
thrive well in weak acids; therefore sulphur disinfection, though 
generally successful, may sometimes fail. Spores are not generally 
killed bj^ it, while species like B. antliracis are extremely resistant 
to sulphurous acid. The dry gas has very little effect on micro- 

' " Tiifektiou u. Disiiifektion." - Loc. cil. 

2 Vallin. "Desinfectaiits,"1882, p. 205. * " Handbucli tier Exp. Path.," 1900. 



K 



INORGANIC SUBSTANCES 199 

organisms, but it destroys all vermin, and therefore is of special 
value in combating insect-borne diseases. As to its effects on the 
lungs, about 5 per cent, in the air has produced fatal results, but 
^ per cent, can be tolerated for some time, and a larger amount with 
the protection of a wet towel alkalized with washing soda. For 
the uses of sulphur dioxide in room disinfection, see Chapter V. 

According to Buchholz, sulphurous acid is a relatively strong 
bactericide, stronger than sulphuric acid. This must be attributed 
to the possession of an aldehyde-reacting grouping. 

Sulphuric acid, like acids generally, by virtue of its dissociation 
into hydrogen ions, is antiseptic, and in some cases disinfectant; 
0-05 per cent, (which is a palatable strength) is fatal to Sp. cholercB 
in fifteen minutes. Stutzen found that this strength disinfected iron 
pipes, cleaning out rust and sediment without sensibly attacking the 
metal. With 0-04 per cent., Ivanoff destroyed cholera organisms 
in Berlin sewage, and Avith 0-08 per cent, in that from Potsdam. 
In our laboratory we found that 0-035 per cent, kills B. typhosus 
in thirty minutes, and 0-07 per cent, in fifteen minutes, in impure 
water infected ordinarily with typhoid ; but with very heavy infec- 
tions the latter strength requires forty-five minutes. One of the 
writers recommended 0-09 per cent, as having advantages over 
heat sterilization m dealing with the drainage from hospitals and 
other infected areas; the acidity would speedily be ''neutralized on 
mixing with the bulk of the sewage.^ In the Lienur process a much 
7 stronger sulphuric acid is used for sterilizing sewage, combined with 
the recovery of ammonia. 

Sodium bisulphate has been introduced by one of the wi'iters 
and Dr. Parkes as a means of sterilizing drinking-water for armies 
in the field and for travellers. Fifteen grains of NaHS04 to a pint 
of water in fifteen minutes destroys B. typhosus and enteritidis, 
Spirillum cholerce, and internal parasitic worms. In effervescent 
tabloids yielding a slightly acid solution it was used with success 
in the South African and Russo-Japanese Wars, and has been exten- 
sively used in the European War. Kenwood and Hewlett found 
that one tablet per pint of water killed B. typhosus and <S'. pyog. 
aureus in two minutes." 

Persulphates give off oxygen when moist, and are useful as hand 
disinfectants.^ 

Carbon disulphide, if it were not for other properties, would be 
a valuable disinfectant. As well as its alkaline compounds, the 

^ British Association, 1901. 

^ Martindale's " Extra Pharmacopoeia," 1908, p. 932. 

'^ Lancet, 1905, ii., IIOU. 



200 DISINFECTION AND STERILIZATION 

xanthates, it has been found useful against fungi, such as the vine 
phylloxera. For this 23urpose it would appear that it may be 
supplanted by chlorpicrin, which was found by Moore^ to be over 
280 times as effective, requiring a dose of only 0-5 pound per 
1,000 cubic feet of space. Ckeandi Bey's lamp burns it safely for 
generating sulphur dioxide. 

The Halogens. 

Chlorine, bromine, and iodine act as disinfectants in several ways. 
They can combine directly Avith organic substances or replace the 
hydrogen in them, precipitating albuminous substances and render- 
ing them imputrescible, killing organisms by combining with and 
coagulating protoplasm, removing their food or rendering it unsuit- 
able, acting to them as irritants or direct poisons, also producing 
substances which have that effect. 

Chlorine and the hypochlorites, like other oxidizers, are consumed 
by otherwise inert organic and inorganic matters present, but in 
ordinary disinfection leave behind them as substitution compounds 
which maintain the germicidal powers, the chloramines, hydrazine, 
and the chloroproteins.- In dilute solution the R.W. coefficient 
is 2-18 for 1 per cent, of available chlorine; this is increased to 6-30 
by the addition of an equivalent of ammonia. It remains near 
this level for twenty-four hours, and even after seventj^-two hours 
has an enhanced value. Therefore, since the coefficient of chlorine 
itself averages 220 units, that of ammonia less than 0-7, and ammon- 
ium chloride nil, that of the chief product, chloramine, NH2CI, must 
be over 600 units; hence, this substance, but for its instability, 
would probably be the most valuable of disinfectants. It has a 
pungent odour, hitherto often mistaken for chlorine or hyj)ochlorous 
acid, and gives the blue reaction with potassium iodide and starch! 
With excess of ammonia, as in sewages, it gradually disappears, form- 
ing a salt of hydrazine, which still has a germicidal value (R.W. 
coefficient of the base at least 24). The action of chlorine on nitro- 
genous organic compounds gives compound chloramines, many of 
which are insoluble ; they have a tendency to become fixed on cellu- 
lose, and in this way attack the envelopes of organisms. Chlorine 
in the free state has been generally disused in disinfection, with 
the exception of water sterilization (see p. 80), on account of 
difficulties in practice. Preparations must be tested as to the 
amount of "available chlorine." Chloride of lime, or "Calx 
chlorinata," about 33 per cent, available chlorine, has some advan- 
tages from being solid, but is quickly deliquesced and decomposed 
by air, takes some time to dissolve, and gives a quantity of insoluble 
1 J. Econ. Entomd., 1918, 11, 357, 443. 
- Rideal, J. Roy. San. Inst., 1910, 31, 2. 



INORGANIC SUBSTANCES 201 

waste. There is in many respects a preference for sodium solu- 
tions: chlorinated soda, or Eau de Labarraque (often called 
Eau de Javel, which was originally the potash salt), about 
2-5 per cent, available chlorine; Chloros, 10 per cent, available 
chlorine; and the electrolytically prepared hypochlorites, up to 
11-5 per cent, available chlorine. Her mite fluid, used successfully 
at Poplar, employs magnesia as an adjunct in the electrolysis, 
and contains free hypochlorous acid, 4-2 ]3er cent, available chlorine. 
The effective strength for local disinfection is 0-35 X)er cent, avail- 
able chlorine, which kills non-sporing organisms in five to ten 
minutes, and anthrax and enteritidis spores in one and a half hours. 
Chloride of lime has the objection that it leaves the surface for a 
long time damp from the presence of sodium chloride. The same 
salt imparts its bitter taste and increases the hardness when it has 
been applied to the purification of drinking-water, while the sodium 
preparations tend to soften the water and are not sensible in the 
flavour. 

Hypochlorous Acid. — For medical purposes various modifica- 
tions of the original Dakin's solution have been prepared. These 
preparations all owe their germicidal activity to hypochlorous acid 
liberated by the action of a slightly stronger acid from bleaching 
powder or sodium hypochlorite. In order to ensure that the 
hydrogen-ion concentration of the solution shall not change in 
storage, thus obviating the danger of a too acid or alkaline reagent 
being brought into contact with living tissue, and at the same time 
minimizing the rate of decomposition of the acid, a buffer salt — e.g., 
a borate — is added to the solution.^ It would appear that hypo- 
chlorous acid itself exerts its germicidal activity by the formation 
of substituted chloramines with the nitrogenous constituent of the 
tissue according to the general reaction : 

>NH + HOCl -> >NC1 -f HoO. 

Amongst the many preparations containing free hypochlorous 
acid and a buffer salt may be mentioned eupad, a powder consisting 
of equal weights of bleaching powder and boric acid ; eusol, prepared 
by the solution with the subsequent filtration of 25 grammes eupad 
in a litre of water. 

For medical purposes, in addition to their uniformity of ccmi])0- 
sition, these stabilized solutions of hypochlorous acids possess other 
advantages in that they are h?emolytic, do not dissolve dead tissue, 
are non-irritant, and have a high penetrative ])ower. Dakin'- 
suggests the following mixture as suitable: bleaching po\Ader, 

1 H. D. Dakin, Brit. Med. J., December 4. 1915. 

2 J. Soc. Chem. Ind., 1915, 919. 



202 DISINFECTION AND STERILIZATION 

200 grammes mixed with water (10 litres) containing 140 grammes 
sodium bicarbonate, and the following liquid made neutral Avith 
from 25 to 40 grammes of boric acid. Excess boric acid is to be 
avoided. Staphylococci were found to be killed in tAvo hours by 
1 : 500,000, whilst these organisms in blood were destroyed by 
1 : 1,000 to 1 : 2,000. 

Pastes have likewise been prepared on the same principle; thus 
Monziols^ suggests a paste of the following composition : 10 grammes 
H3BO3, 15 grammes talc, 2 grammes chloride of lime \nth a little 
water. It is claimed that it will sterilize the hands in three minutes. 

Dr. Cash, from experiments on anthrax and tubercle, main- 
tained that the quantities of chlorine, bromine, and iodine required 
for disinfection under the same circumstances were nearly in the 
ratio of their atomic weights. Iodine is, however, a more imme- 
diate poison to j)rotoplasm than chlorine. 

Bromine is a powerful disinfectant, a saturated aqueous solution 
having a carbolic acid coefficient of 64, but its use is obviously 
limited by its danger. In 1897 Altmann patented a solution of 
bromine in potassium bromide with five minutes' contact and 
removing excess by ammonia ; the potassium salt has disadvantages. 
Braithwaite introduced a dry mixture of sodium or potassium 
bromide and bromate with sodium bisulphate, which with mois- 
ture liberates bromine. Schumberg, of the German Army, about 
the same time recommended free bromine in thin sealed tubes for 
the same purpose,- in the proportion of 60 parts per million with 
five minutes' contact, removing excess by thiosulphate. Braith- 
waite advised about the same amount, 57 parts; Schiider^ and 
others have stated that this treatment is insufficient to sterilize 
and the presence of residual bromides is against the process.* It 
was tried in the Sudan campaign of 1898. The writers found that 
20 parts per milfion of bromine sterilized B. typhosus in less than 
half an hour. 

Iodine owes many of its uses to its germicidal action, as in para- 
sitic diseases, a saturated solution of iodine having a carbolic acid 
coefficient of 100. Grossich,^ in 1908, adopted the tincture as a 
cutaneous disinfectant before operation, the surface being previously 
cleansed by a 1 per cent, solution of iodine in benzene.^ Instead 
of tincture. Chassevanf suggested the solution in iodoform, as it 
does not, like the former, cause desquamation; its use is specially 

1 Compt. rend. Soc. Biol, 1918, 81, (100. 

2 Zeitsch. Hyg., 1900, 53. ^ Ibid., 37, 306. 

* See also Parkcs and Rideal, Trans. Epidem. Soc, 1901, 20; Frazer, Public 
llpxdth, September, 1002. ^ Centr. Chirurg., No. 4. 

^ Bogden, ibid., January 15, 1910. ^ Lancet, March 20, 1910. 



INORGANIC SUBSTANCES 203 

advised prior to hypodermic injections. ^ During the Sikhim and 
Thibet expedition iodine (in some cases as tincture), followed by 
sodium sulphite, was successfully employed for sterilizing drinking- 
water; and Lieutenant Nesfield recommends triple tablets of 
(a) iodide and iodate, {b) citric or tartaric acid, followed after tMO 
minutes' contact by (c) sodium sulphite, and states that, used in 
this way, 3-8 to 5 parts per million of free iodine sterilizes the 
organisms of typhoid, cholera, and dysentery. The \mters, in 
1905, confirmed this result as regards distilled water infected with 
20,000 per c.c. oi B. typhosus; the (a) and (6) tablets, used as 
directed, gave 4-75 parts of iodine per milHon. 

Fumigation of sick-rooms with iodine, sometimes in conjunction 
with other disinfectants, b}^ burning prepared candles or lamps has 
been tried, but apart from the fact that the method is unsatis- 
factor}^, no chamber can be disinfected while occupied. 

Iodine trichloride was introduced by Von Langenbach for ster- 
ilizing the hands and instruments and for other surgical uses. The 
^Titers find that 50 parts per million are required to kill tj^^^hoid 
in thirtv minutes. A saturated solution of iodine trichloride in 
water has a carbolic acid coeificient of 94. Its activity is but little 
impaired by the addition of albumin or salts. 

Iodine cyanide is said by Robert to be universally destructive 
to lower forms of life, and is suggested for preserving biological 
specimens. 

Fluorides. — ^Hydrofluoric acid is one of the most germicidal of 
the acid group of disinfectants. Paul and Kronig stated that 
sterility in anthrax spores was produced in less than tAvo hours by 
a concentration of 1 gramme per litre. The specific activity of the 
fluorion is noted by the fact that fluorides are powerful antiseptics, 
but not germicides. This activity can in part be accounted for 
by the fact that it is a siaecific reagent for calcium, which is to be 
found in cell nuclein. 

As food preservatives they are only moderately efficient, and 
are not innocent physiologically, as they hinder pancreatic digestion. 
Sodium silico-fluoride [salufer) and boro-fluoride have been tried. 
Effront introduced the use of hydrofluoric acid and its acid salts 
for checking injurious fermentations, and J. Brand^ states that a 
0-5 per cent, solution of acid ammonium fluoride is largely used for 
disinfecting rubber hose in breweries.^ Fluorides form the active 
principle in certain mouth washes. 

1 Brit. Med. J., February and August 14, 1909; Lancel, April IG. 1910. 

2 Zeitsch. Brauw.. 1904, 27, 115. 

3 See also Hehner, Anali/.'it, 1902, 173; Richmond, " Dep. Comm. on Preserva- 
tives," Appendix XXXII.; Thresh and Porter, " Preservatives," 1906, p. 873. 



204 DISINFECTION AND STERILIZATION 

Halide Acids. — HCl, HBr, HI are relatively strong germicides, 
their activity being proportional to their dissociation ; the anions 
appear to exert but little selective action. 

Cyanogen and Hydrocyanic acid (a, weak acid) are more destruc- 
tive to insects than to lower organisms. Fumigation of fruit-trees 
with hydrocyanic acid is extensively practised in America, and is 
considered better than spraying. For greenhouses zinc capsules 
containing sodium cyanide are made ; they are placed in a vessel of 
dilute sulj)huric acid, when the zinc dissolves, while the op/rator 
has time to retire. 

Boric acid, which is feebly dissociated, is not a disinfectant, but 
has a power of restraining bacteria which act injuriously in foods. 
Rideal and Foulerton found that 1 in 2,000 of a boric mixture 
containing 3 parts of H3BO3 and 1 part of crystallized borax keeps 
milk sweet for twenty-four hours without appreciable effect on 
digestion. Koch noted the relative antiseptic concentrations for 
anthrax spores Avere 1/2,000 for borax and 1/1,250 for boric acid. 
The British Departmental Committee, already referred to, recom- 
mend that the only preservatives allowed to be used in cream, 
butter, and margarine be boric acid or mixtures of boric acid and 
borax in proportions of 0-25 per cent, of H3BO3 for the former, and 
0-5 per cent, for the latter two. Its carbolic acid coefficient is less 
than 0-1. 

Carbonic acid seems to have a certain amount of disinfectant 
action, since " aerated " beverages have been shown to be in many 
cases sterilized, and carbonic acid under pressure preserves food. 

H. Colin^ shows that both time and pressure are required to 
effect sterilization by carbon dioxide. Thus, water contaminated 
with B. typhosus was sterilized in twenty hours at 10 atmospheres, 
in eight hours at 15 atmospheres, at from three to four hours at 
20 atmospheres, and from three to six hours at 25 atmospheres of 
carbon dioxide. 

B. Goli was found more resistant, requiring more than five days' 
contact at 25 atmosj)heres. The B. cholercr, was easily destroyed 
in ten hours at 10 atmospheres, and ordinary Seine river- water 
almost completely sterilized in a few hours at 25 atmospheres. 

B. Metallic Derivatives. 

The Alkaline Metals. — The ions of the alkaline metals exert but 
little selective effects on micro-organisms. Blake- noted an increase 
in physiological activity with increasing atomic weight, but 

1 Compt. rend., 1915. 161, 052. 
- Proc. Roy. Soc, LSitl, 14, 304. 



INORGANIC SUBSTANCES 205 

C. Richtet^ gives the equivalent toxic ratios for lithium, potassium^ 
and rubidium as 1-1 to 05 to 1-0. 

In the sim^Dler salts the additive effects of the relatively inert 
anions and cations can be noted in the increasing activity displayed 
by NaCl, NaBr, Nal, NaF. Strong brine is 2:)reservative but not 
disinfectant, and the practice, formerly frequent, of washing out 
milk cans and other utensils with it is not a safe one. Lode^ showed 
that 50 per cent, salt solution does not kill spores of moulds. 

The hydroxides in the form of alkaline Ij'es are to be classed 
amongst the most ancient of disinfectants. They effect sterility 
in the proportion of not less than 2 to 5 per cent., and the carbonates 
in from 5 to 10 per cent, concentration. At 60° C. a contact of 
five minutes ensures the death of most organisms,^ hence washing 
soaj^s which undergo partial hydrolysis in their solutions possess a 
slight disinfectant value (see p. 108). Caustic soda has even been 
suggested for destroying B. antkracis in hides (see p. 147). The 
germicidal activity of these solutions is proportional to the hydroxyl- 
ion concentration,* which has a specific germicidal activit}' of about 
one-fifth of the more active hydrogen ion. The feebly-dissociated 
base ammonium hydroxide has but slight value as a germicide. 

The Alkaline Earths. — Of the alkaline earths, lime, as quicklime, 
is the only compound which has been used extensively as a germi- 
cide. Its activity is to be attributed to its caustic and hygroscopic 
properties when dry, and to the presence of hydroxyl ions when in 
solution or suspension. No definite evidence for any specified 
activity of the calcium ion is on record. 

Quicklime is fatal to bacteria when it comes in contact with 
them in an almost dry condition, and has been much used where 
there is a considerable space and bulk of material to be dealt with. 
It is not safe, however, to trust entirely to the old method of burying 
infected bodies in lime, as on disinterring the live spores may again 
be diffused, unless a long period has elapsed. The disinfecting 
power of milk of lime and whitewash has been much overrated; 
as to milk of lime, Liborius^ stated that 74 parts per million of CaC) 
destroyed typhoid bacilli, and that 246 parts per million were 
required for cholera organisms, while 2 per cent, of dry lime was 
needed for cholera discharges, Avith in each case " a few hours' " 
contact. When lime is added to scAvage, a great number of bac- 
teria are carried do"WTi, but are not killed, and the supernatant 
liquid is not sterilized. 

1 Compt. rend., 101, OGT. - Chem. Zentr., 1902, i., 1122. 

3 Zeitsch. Ilyg., 1903, :}49. 

* Strictly the "activities" or therinodynamic concentrations and not tlio 
actual concentrations should be employed in all cas(>s where comparative^ ilata 
are required. For dilute solutions the two are alniost identical. 

5 ,/. Hoc. (Vicm. Ind., 1915. (V.]2. ■ 



206 DISINFECTION AND STERILIZATION 

The Heavy Metals. — Some metals in the free state are antago- 
nistic to germs. Dievert^ states that agitation with granulated 
zinc kills B. typhosus and coli in a few hours, and Baeyer's method 
of treating polluted waters with zinc dust, charcoal, and lime causes, 
according to Margosches,- practical sterilization. Rankin^ shows 
that clean strips of aluminium, zinc, or copper in air-free Avater do 
not reduce the number of coli, while, when air is bubbled through 
there is a great reduction after one hour. Except with copper, 
peroxide of hydrogen was produced, but the amount of this and 
the metal dissolved is too small to account for the germicidal 
effect, which is ascribed to the oxide and metal together. Metallic 
iron has long been used for purifying water, as in Anderson's* 
process; in this case electro-chemical action, resulting in the forma- 
tion of flocculent hydroxides, comes largely into play, but Frank- 
land proved that the metal itself was to a certain extent bacteri- 
cidal. 

Old Hindu writings direct water to be kept in vessels of copper; 
among modern observers, Nageli, Galeotti, Israel, and Klingman 
hold that there is formed a colloidal solution that renders the water 
toxic to many algae and bacteria. In 1904 the U.S. Department of 
Agriculture reported that 1 square centimetre of bright copper per 
100 c.c. of water was sufficient to exterminate uroglena and some 
forms of spirogyra, and Kraemer showed that the same treatment 
destroyed colon and typhoid bacilli in four hours, while colloidal 
copper was quickly fatal to these organisms. For household puri- 
fication he recommended the use of strips of copper about 3i square 
inches to each quart (2 square centimetres to 100 c.c.) immersed 
in the water for about six to eight hours. In a similar way Rideal 
and Baines^ obtained sterilization of B. typhosus, B. coli, and Sp. 
pyog. aureus in less than twenty-four hours. Bassett Smith^ found 
that in a bright copper vessel B. typhosus was still living at twelve 
hours, but dead at twenty-four hours, and that of ordinary water 
organisms, 1,020 per c.c. at first, only 8 per c.c. (none of them 
liquefying) were left after twenty-four hours. He also found that 
clear iron or zinc was nearly equal to copper in first effect, but soon 
lost the power by oxidation. 

CoUoidal Metals. — For medical purposes a great number of 
colloidal metals have been proposed, especially those in which the 
ions of the metals are powerfully germicidal, such as mercury ; silver, 
collargol, argofermeni^ syrgol, albargin^ lysargin ; copper, cupriase, 
and copper oxide, cuprase; arsenic, and others. 

1 Compt. rend., 136, 707. - Leipz. Monatsh. Textil, 1901, 6. 

3 Proc. Roy. Soc, litlO, B. 82. * J. Soc. Art.f. February 14, 189G. 

5 J. San. In.^t., 1904, 594. « J. PrevcnI. Med., Julv. 1904. 



INORGANIC SUBSTANCES 207 

The colloidal metals themselves, prepared by electrical disper- 
sion or by chemical reduction methods, are too unstable for practical 
work, being rapidly precipitated by electrolytes m vitreo or in the 
blood-serum. It is thus necessary to protect the colloidal metal 
with some suitable protective colloid. Protective colloids, such as 
protalbic and lysalbic acids, are the most used, owing to their great 
protective powers, but it is customary not to isolate these materials 
in the pure state, utilizing instead proteins and nucleins. Less 
efficient as protecting agents are gelatine and the starches which 
occasionally find application. The importance of the nature of the 
protective colloid employed cannot be over-estimated, since it 
is highly probable that the colloidal metal is germicidally operative 
by a gradual decomposition into ions, which are the active germi- 
cides. The rate of this gradual ionic disintegration or chemical 
solution is governed by the protective colloid. The function of a 
protective colloid appears to be twofold: first, a peptizing action 
on the colloid which ensures a high dispersivity essential for the 
economic utilization and the uniform distribution of the agent; 
and, secondly, a coating action on the sol, through which the reagent 
and the ion have to travel before the latter can become germicidally 
active. A well-protected colloidal metal is non-toxic, oAving to the 
very slow release of ions through the protective agent, whilst an 
^ unprotected sol is usually extremely toxic. This difference in the 
degree of protection would seem adequately to account for the 
anomalous results obtained with colloidal arsenic from different 
sources.^ Thus the protective agent should be varied with the 
power of the patient to excrete toxic ions, since, naturally, the ionic 
concentration should be raised as high as is compatible Avith safetj- 
to the health of the individual. 

Both colloidal mercury, silver,- and gokP have been used Avith 
success for disinfection in vivo; they maj' be injected intravenously, 
intramuscularly, or hj-podermically in the j)eripheral zones of the 
infected region. 

Copper salts have a distinctly poisonous action on lower organ- 
isms, partly from their property of coagulating albumin and com- 
bining with many of the constituents of the tissues. Kroncke 
considered cuprous chloride to be the most active of the salts; he 
treated Elbe water containing 40,000 to 50,000 organisms per c.c. 
with 50 per million of cuprous chloride and 20 parts of ferrous 
sulphate, allowed six hours' contact, then agitated A\ith 10 parts of 
lime. After settHng and filtering through sand, the water was 
sterilized, clear and colourless, and free from iron and copper. 

1 See Sorev, Compt. rend. Soc. Biol., 1918, 81, 563. 

2 Marshall, Brit. Med. J., June, 1915. ^ M. Pollard, Lancet, May. 1915. 



208 DISINFECTION AND STERILIZATION 

Schumberg^ corroborated the sterilitj' at the end of the six hours. 
The eflficiency of soluble cupric salts is generally dependent on their 
percentage of copper,- but the sulphate is commonly used as most 
convenient. For disinfecting sewage effluents, American investiga- 
tors conclude that copper sulphate " is not so efficient as chlorine 
compounds, is more seriously affected by carbonates, and is much 
more expensive."^ Disinfection of excreta and morbid products, 
even with considerable quantities of copper salts^ — t.g., 5 to 10 per 
cent, of the sulphate — is not reliable. Copper soap washes for trees 
and Bordeaux mixture (copper sulphate and lime) for vines are 
well known; Chuard* estimates that 2,000 tons of copper are thus 
consumed annually in France, and expresses anxiety as to the 
result of its accumulation in the surface soil, and with a view to 
reducing the quantity states that a J per cent, aqueous mixture 
of the oxychloride is as adhesive and effective as the usual 2 per cent, 
paste of the sulphate. 

Mercury Salts. — ^Mercuric chloride, " corrosive sublimate," has 
long been recognized as one of the most powerful of disinfectants, 
and a 1 per 1,000 solution is a kind of standard for comparisons. 
Apart from cost, points limiting its utility to special purposes are 
(1) its poisonous effect on higher animals and plants; (2) its pre- 
cipitation by so large a number of substances, such as hard water, 
alkalies, and numerous salts, metals, sulphides, and many organic 
bodies, causing its action to be liable to great variations and incon- 
veniences. It will often form a pellicle over organisms without 
killing them, and it is inapplicable to the disinfection of sputum, 
excreta, and the like, since it produces a coagulum which prevents 
further penetration. Sodium chloride is sometimes added to increase 
the stability, but considerably diminishes the germicidal power. 
The Local Government Board recommended for disinfecting pur- 
poses: Mercuric chloride, i ounce; hydrochloric acid, 1 fluid ounce; 
aniline blue (a colouring for safety), 5 grains; water, 3 gallons 
(1 in 962). Kronig and Paul's work in 1897 showed that mercury 
salts follow a general rule that the germicidal power depends on 
the metallic ion, and is in proportion to the degree of ionization, so 
that a 1 in 500 solution of mercuric chloride is much less than twice 
as active as a 1 in 1,000 solution; moreover, the chloride is more 
active (in equivalent solutions) than the bromide, and four times 
more active than the cyanide, which is almost unionized. Solutions 
of the oxycyanide have been used in surgery, have a sHght alkaline 

1 Chcm. Zentr., 1900, ii., 203. 

2 Green, Zeitsch. Hyg., 1893, 495; Ridoal and Baines, loc. cit. 

3 U.S. Gool. Survey, Water Supply, Paper 229 of 1909, p. 32; also Bull. U.S. 
Dept. of Agric, No. 100, 1900. * Compt. rend., 1910, 150, 839. 



INORGANIC SUBSTANCES 209 

reaction, and only slightly precipitate albumin; in a strength of 
1 in 1,500 it is antiseptic, does not readily attack instruments, nor 
irritate sensitive parts. Mercuric iodide, dissolved in potassium 
iodide, is a powerful disinfectant, and is made up in tablets as 
" Iodic hydrarg." It is less affected by albuminoids and less 
irritant than the chloride, and can be incorporated in soaps. 
Mercury zinc cyanide, Lister's antiseptic has the disadvantage of 
being of variable composition.^ A great number of organic mer- 
curial compounds introduced into medicine and surgery owe part 
of their effect to an antiseptic or ""germicidal action. Suhlamin, 
mercuric ethylenediamine sulphate (43 per cent. Hg), is easily 
soluble in water, is much less irritant than mercuric chloride, does 
not coagulate albuminous solutions nor precipitate soaj:), and is a 
valuable hand disinfectant. Proiedyl, according to Drs. Aufrecht 
and Feibes, contains about 96 per cent, water, 1 per cent, salicylic 
acid, 0-2 per cent, mercury, and about 3 per cent, gelatine. 

Silver Salts. — -Silver nitrate stands next to mercuric chloride in 
germicidal power, and has the same limitations in use, with the 
additional one of being precipitated by chlorides. The WTiters 
found that in distilled water 1 in 1,000 killed B. coli and *S'. 'pyog. 
aureus in twenty-four hours, but a small quantity of chloride or 
organic matter prevented the effect. Martindale gives 1 in 2,000 
for killing in two and a half minutes. Among other silver salts are 
the citrate, Urol, recommended as a non-irritant antiseptic dusting 
for wounds;^ actol, the lactate for antiseptic mjections; argentide 
(silver iodide), used as a precipitant and germicide for water; 
tachiol, silver fluoride, easily soluble, and said to be a powerful non- 
toxic bactericide, specially suitable for use in the urinary tract (1 
in 1,000 to 1 in 5,000). Chiefl}' with the object of avoiding irritant 
action, incompatibility with chlorides, and coagulation of albu- 
minoids, a large number of organic preparations of silver have been 
introduced, which will be enumerated later. 

Zinc Salts. — Zinc chloride, Burnett's fluid, formerlj- in high repute 
as a dismfectant, is not reliable m its effect, and ranks below copjaer 
sulphate and mercuric chloride. The sulj)hate is still less active. 

Aluminium Salts. — Aluminium chloride, chloraluni, was classed 
by Miguel between zinc chloride and copper sulphate. Alsol, a 
solution of alummium acetotartrate, is recommended in treatment 
of eye diseases. 

Iron salts, especially ferrous sulphate, were at one time in vogue 
\ for sanitation, but are comparatively meffective. 

1 Trans. Chem. Soc, 1892, 66tj. ^ pjiarm. CentralblL, 38, 460. 

14 



210 DIvSINFECTION AND STERILIZATION 

Permanganates and Manganates were first introduced as Condys 
red and green fluids. Like oxidizers generally, they are largely 
consumed by otherwise inert matters before attacking organisms, 
and as complete disinfection cannot be ensured unless an excess 
of reagent remains, evidenced by the pink colour, which is not 
always visible owing to the brown oxide of manganese produced, 
their use may be very costly, and the result is frequently im- 
perfect. The writers carried out an experiment in street watering 
of two similar areas of ordinarily soiled asphalt roadway, (a) with 
water alone, (6) with permanganate solution 1 in 5,000 (six times 
the amount then customary), and examined the liquid from the 
surface. The permanganate was almost immediately decolourized. 
The sample [b) "was nearly inodorous, on keeping became much less 
foul than (a), and the reduction in the number of organisms was 
96 per cent., but the survivors included a large proportion of dan- 
gerous forms. ^ For polluted water Rosenau recommends adding 
permanganate drop by drop till the pink colour persists for twenty- 
four hours. " Pinking " of wells was many years ago adopted by 
Hankin in India as a precaution against cholera. Permanganates, 
used in various ways, are still being patented, chieflj' for water 
purification. 

Arsenic Salts. — The inorganic salts of arsenic have but a limited 
application as germicides on account of their toxicity. The organic 
arsenicals, on the other hand, A\'hich permit of sIoav liberation by 
hydrolysis of arsenious ions within the organism, are amongst the 
most potent of the trypanocides and spiriUocides yet discovered. 
Trivalent arsenious derivatives are more germicidal than the pen- 
tavalent compounds; thus arsenious acid was found to be three 
hundred times as germicidal as arsenic acid on isolated organisms, - 
trypanosomes were destroyed by concentrations of 1 : 20,000 of the 
former, but 1 : 100 of arsenic acid was required. FriedenthaP 
found arsenious acid a stronger disinfectant than boric acid. Simi- 
larly sodium arsenite was much more antiseptic for yeast cells than 
the sodium arsenate.* Green and KestelP find instances of selective 
action of the arsenites on micro-organisms; thus to a 0-05 per cent, 
solution -B. suhtilis, cohform organisms and three out of four strains 
of cocci were found sensitive; B. putridium was found insensitive. 

Arsine is apparently much less active than arsenious acid, as 
instanced by its action on infusoria." 

1 Ridoal's " iSewage," 1900, p. 177. 

2 Joachimoglu, Biochciii. Zeit., 1915, 70, 144. 

3 Biochem. Zeit., 1919. 94, 47. 

* Joachimoglu and i'^ricdbcrgcr, Biuchoii. Zeit., 1U17, 79, 130. 

5 ti. Africa. J. iS'c/., 1919. 15, :5(i(t. 

" I'^iilmor, Arch. E.cp. Fulh. I'harm., 1917, 82, 44. 



INORGANIC SUBSTANCES 211 

Arsenic, like cyanogen, has more effect on higlier than on lower 
forms of life, and is the basis of valuable insecticides, such as the 
sheep-dip solutions of arsenious oxide or sulphide in soda, frequently 
associated with tar products or nicotine (see p. 145), and the copper 
compounds, Paris green (aceto-arsenite), and others, used for spray- 
ing or dusting trees. In the latter case the actions of arsenic and 
copper are combined, and the fineness of the powder is of great 
importance. 

Antimony. — The antiseptic and germicidal powers of the stib- 
nites and stibnates are much more feeble than those of the corre- 
sponding arsenicals. In this case also the derivatives of trivalent 
antimony are more powerful tlian the i:)entavalent comj)ounds. 
Colloidal antimony and stibnous acid, Sb{0H)3, exert a definite 
but weak germicidal action, a 30 per cent, emulsion of the latter, 
trixidin, having been used with success as a spirillocide. The thio- 
stibnate, NagSbSj, is likewise stated to be trypanocidal. Behring^ 
found that the double fluoride of antimony and potassium was 
nearly as effective as mercuric chloride. 

Bismuth. — A number of compounds containing bismuth oxide 
have been prepared and utilized as internal astringents and dis- 
infectants. Their antiseptic power is, however, low, and they 
possess but little, if any, germicidal activity. Their action is in 
most cases confined to a protective action. Amongst the more 
usual preparations of this type may be mentioned hismona, a 
colloidal bismuth oxide, and bismuthose, containing the oxide in- 
corjDorated ^^'ith albumin. The organic derivatives are enumerated 
later (p. 278). 

Osmic acid was found by Koch and Klein to be powerfully 
bactericidal; it is very poisonous and a strong oxidizer. The 
former stated that an extremely dilute solution of potassium auri- 
cyanide, 1 part in 2,000,000 checked the growth of B. tuberculosis, 
whilst Behring noted that anthrax was destroyed m vitreo by a 
concentration of 1 in 1,000,000. 

Chromic acid, although a powerful oxidizer and instantly 
coagulating albumin, is excluded by its cost and j)oisonous and 
corrosive nature from the list of useful disinfectants or of pre- 
servatives j 2h per cent, solution kills 2^. coli in two and a half 
minutes. 

^ " Iufcktiou unci Di.sinfoktion," Leipzig, 1897, 



212 DISINFECTION AND STERILIZATION 



BIBLIOGRAPHY. 

Sc'i£OTTELFUS, M. : Die Chlor-Krcsole als Desinfektioumettcl, I'rakt. Dcsinjckl., 
1915, Heft 61-64. 

Dakin, H. D., and Cohen, J. B. (ei al.): The Antiseptic Action of Substances of the 
Chloraminc Group, Proc. Roy. Soc, 1916, 89B, 232-250. 

Dakik, H., and Carlisle, H. G.: Rejiort on tlie Use of Sodium Hypochlorite Pre- 
pared by the Electrolysis of Sea-Water for Disinfecting and Antiseptic Pur- 
poses in H.M.S. Aquitania, J. Roy. Army Med. Corps. 1916, 26, 209, 227. 

Thurn, J. K.: Carrel-Dakin Solution, Electric Med. J., 1917, 77, 502-506. 

GiLMOUR, C. H.: Daufresne's Latest Improvements of Dakin's Solution, Canrerf. 
J. Med. and Surg.. 1917, 42, 35-40. 

Fralick, W. G.: Isotonic Hypochlorite Solution, Med. Times, 1917, 65, 192-195. 

Barratt, M. T. : The Dakin-Carrel Antiseirtic Solution, Dental Reg., 1917, 71, 237- 
240. 

Dakin, H. D. : On the Oxidation of Amino-Acids and of Related Substances with 
Chloramine-T, Biochem. J., 1917, 11, 79-95. 

Dubard: Procede de desinfection des mains par I'emploi combine de I'hypo- 
chlorite de magnesie et d'un vernis antiseptique, Arch. Med. Pharm. Mil., 
1916-17,66,503. 

Baird, a. p.: Chlorazene, Calif. Edect. Med. J., 1917, 38, 264-266. 

Krauss, R. B., and Crede, E.: Dichloramine-T and Chlorinated Eucalyptol, 
1, 2, J. Amer. Chem. Soc, 1917, 39, 2720-2722. 

Horn, D. W. : Bleaching Powder in Place of Permanganate in Fumigation, A7ner. 
J. Pub. Health. 1918, 8, 161. 

Dakin, H. D., and Dunham, E. K. : Solvents for Dichloramine-T, Brit. Med. J., 
1918, i., 51. 

Krauss, R. B.: The Preparation of Chloramine-T and Chlorinated Eucalyptol, 
1, 2, J. Amer. Pharm. Assoc, 1918, 7, 46, 49; also Amer. J. Pluirm., 1918, 90, 
16-21. 

Hawk, P. B., Da Custa, J. C, Smith, C. A., Rehfuss, M. E., and Schoonmaker, 
• G. D.: Chemical and Clinical Study of Chlorlyptus, a New Chlorinated Anti- 
septic, Thera-p. Gaz., March, 1920, 44, 156. 

Simpson, M. J., and Hewlett, R. T.: Experiments on the Germicidal Action of 
Colloidal Silver, Lancet, 1914, ii., 1359. 

Brennan, J. A. C. : Clinical Experience with Silvol, a Now Silver Preparation, 
Louisville Mo7ith. J. Med. and Surg., 1914-15, 31, 335. 

WiRGLER, H.: Ueber ein neues Silberkolloid Disjjaragen, Miinch. Med. 
Wochenschr., 1915, 62, 857-859. 

Marshall, C. R., and Killoch, G. B. : The Bactericidal Action of Collosols of 
Silver and Mercury, Brit. Med. J., 1915, i., 102-104. 

TiMOFEYEFF, G. Ye, and Kraotsoff, V. A.: How to Obtain Colloidal Silver by 
Paal's Method, Khartow Med. J., 1916, 21, 60-67. 

Fressinger, N.: Notions recentes sur les injections intravoineuses de colloidaux 
artificials, Rev. Gen. Clin. Therap., 1916, 30, 121-125. 

Geenet, H.: L'Or colloidal en thcrapeutique regies a observer dans son emploi, 
Arch. Med. Pharm. Mil., 1916-17, 66, 482. 

BouYGUES, I.: Traitement du typhus exanthematique et du typhus recurrent par 
I'or et I'argent a I'etat colloidal, Presse mcd., 1916, 24, 391. 

Schamberg, J. F., KoLMER, J. A., and Raiziss, G. W.: A New and Superior Mer- 
curial Germicide: Preliminary Report, J. Aincr. Mcd. Assoc, 1917, 67, 1458- 
1460. 



CHAPTER XI 
THE CHEMICALS EMPLOYED IN DISINFECTION— fon^mweti 

ORGANIC SUBSTAATCES: ALIPHATIC DERIVATIVES. 

Hydrocarbons. — ^The saturated hydrocarbons of the paraffin or 
petroleum series, such as heptane, C^Hj^, and the petrols, 
C^llio,Cgii^ji, possess no distinct germicidal power, but have long 
been used as insecticides in horticulture. 

Acids. 

The antiseptic power of the aliphatic acids, as well as the 
dissociation constant, generally decreases with increasing molecular 
weight. 

Formic acid, HCOOH, has a higher antiseptic power than the 
next homologue, acetic acid, due not only to the greater dissociation, 
but also to the aldehyde grouping, although Kitasato's results, as 
summarized by Horrocks, gave acetic acid a slightly higher activity 
in nutrient media, probably owing to interaction of the aldehyde 
grouping mth - NHo groups in the medium. He states that with 
B. typhosus the amounts per cent, in cases of (1) groAvth. (2) growth 
restrained, (3) no growth, were respectively: Formic acid, 0-22, 
0-278, and 0-356; acetic acid, 0-2, 0-225, and 0-3; with Sp. cholerce: 
formic acid, 0-11, 0-167, and 0-22; acetic acid, 0-1, 0-153, and 0-2. 
But very different results were obtained in water and most organic 
solutions. In our laboratory it was found that-B. typhosiis is killed 
by 0-5 per cent, of formic acid in less than fifteen minutes, and by 
0-1 per cent, in about thirty minutes, and the R.W. t\q3hosus 
coefficient of formic acid is many times higher than that of acetic 
acid. We have also found the preservative action to be higher; 
with vegetable substances 1 per cent, of formic acid was found to be 
equal in effect to 5 per cent, acetic acid (time of trial two months). 
Raw fish were mounted in 0-53 per cent, formic, in 5 per cent, 
acetic, and in 0-3 per cent, boric acids, heated for twenty minutes 
at 80° C, and the jar closed with cotton-wool; the last was browTiish; 
disintegrated, and uneatable, though not distinctly putrid, in a 
week ; the first tA\'0 kept sweet and of a natural character for three 
months. Experiments with a bread pulp infected with a mixed 
mould growth proved that 0-1 per cent, of formic acid is sufficient 

•213 



214 DISINFECTION AND STERILIZATION 

to entirely inhibit the growth of moulds for several days even under 
the most favourable conditions of culture. But in the destruction 
of the spores formic acid is less effective than formaldehyde. 
Lebbin^ efficiently preserved different classes of foods by 0-15 per 
cent, of formic acid, and specially recommends it for fruits and 
s>Tups. The Avriters, Lebbin, and others, have proved that in the 
quantities mentioned above it is physiologically harmless, the taste 
is more pleasant than acetic acid, and the odour is not noticeable. 
B. H. Smith- preserved vegetables with formic, salicylic, and benzoic 
acids in unprotected jars. Under conditions in which the untreated 
samples became mouldy and sour in two days, 0-1 per cent, formic 
acid preserved them for seven days, 0-3 per cent, for twelve to 
eighteen days, 0-5 per cent, for twenty-five to thirty-four days, 
0-7 and 1 jier cent, for forty-five to eighty-five days, and 2 per 
cent, for over eighty-five days. He states that 0-1 per cent, 
of benzoic acid kept his samples for eighty-five days, while with 
the same quantity of salicylic acid it was sour in nine days. 
In ordinary preserving practice, as we have seen, the articles 
would have remained good for the longer time with the lesser 
quantities of formic acid, which, even if it must be applied in a 
somewhat higher proportion, is for physiological reasons pref- 
erable to salicylic or benzoic acids. The chief formic acid pre- 
servatives used in commerce, mainly for fruit preparations, are 
werderol and fructol, 10 to 14 per cent, formic acid, " 1 to 1 j per 
cent, of the liquid to be added "; and alacet (made synthetically 
from carbon monoxide and sodium hydroxide at the Nitritfabric, 
Kopenick), about 50 to 60 per cent, formic acid, " use 0-3 per 
cent, of the liquid." The result in the three cases would be 
about 0-14 to 0-18 per cent, formic acid. In an investigation of 
these products, Croner and Seligmann' find that inhibition of 
moulds, yeasts, and acid-forming organisms begins at 0-15 peT- 
cent, formic acid, that sterilization i.s effected in twenty-four hours 
bj^ 0-2 per cent., and in ten to thirty minutes by 1 per cent. 

Only the free acid is germicidal, although the salts do not 
favour the growth as do the alkaline acetates. Sodium formate 
increases the solubility of many antiseptics without lessening 
their power, and therefore figures as an adjunct in a number of 
patents. 

Acetic acid is one of the most anciently used preservatives; 
aromatic vinegar, and a more or less concentrated acid containing 
essential oils, had a partially justified reputation against infection. 
The authors found that R. coli is killed by 5 per cent, acetic acid in 

1 Chem. Zeit., 19()(i, 30, 1009. - J. Amcr. Chem. Soc, 1907, 1236. 

^ Zeilsch. Hyg., 1907, 56, 387. 



ALIPHATIC DERIVATIVES 215 

five minutes, by 2-5 per cent, in fifteen minutes, while with 0-5 
and 0-1 per cent, it is ahve after forty minutes. 

Pyroligneous acid, or crude wood vinegar, owes its antiseptic 
power chiefly to the presence of creosote and formaldehyde. 

Propionic acid has been tested comparatively by Duggan^ with 
the highly resistant 5. subtilis. He gives as the strengths necessary 
for killing : Formic acid, 7 per cent. ; acetic acid, 9 per cent. ; pro- 
pionic acid, 12 per cent. ; numbers proportional to the molecular 
weights. According to A. C. Jordan,^ 0"1 per cent, of butyric acid 
in broth-tubes infected -with vigorous cultures oiB. typhosus c&used 
them to remain sterile; S. pyog. aureus required 0-2 per cent. 

Valeric acid is a feeble antiseptic, but has been introduced, in- 
corporated with a little creosote, as an internal antisej)tic called 

geosote. 

\Qleic acid and the fats, lanoline, etc., have no antiseptic power in 
themselves, but when applied to the skin may prevent infection by 
the exclusion of germs. Vicario, however, observed that fatty 
matter sometimes already contains germs, and Baldas^ proved that 
B. coli and typhosus, S. aureus and albus retained their virulence in 
oils for two months; therefore, ointment bases require to be ster- 
ilized by heating to 100^ or preferably to 120° C, as various bacilli 
survive in oil far longer than in aqueous solution. In fatty media 
antiseptics and disinfectants are, as a rule, much less active than 
in water, hence the ineffectiveness of carbolized oil, as shown by 
Koch and Breslauer. Lanoline and cold cream contain water, so 
can enable agents in aqueous solution to come in contact with 
organisms. Some metallic oleates are parasiticide, as cupric oleate 
in ringworm and favus,* mercuric oleate for pediculi; zinc oleate 
is said to cure chronic eczema. According to Reichenbach,-' of 
the alkaHne earth salts of the fatty acids, the palmitates are the 
strongest in bactericidal action. The potassium salts of the 
saturated fatty acids are strong bactericides, whilst unsaturated 
ones, with the exception of elaidic acid, are not (see Chapter VI.). 

Oxalic acid is an irritant, corrosive poison, and is said to be 
antiseptic. Its solutions certainly inhibit the growth of organisms, 
whilst the oxalates only allow slow growth to proceed. Its toxicity 
is to be ascribed to the precipitation of calcium oxalate within the 
micro-organism . 

Acids like tartaric, citric, and malic have the general power of 
inhibiting the growth of bacteria, which prefer a neutral to an acid 

^ Amer. C'hem. J.. 7, f>2. - Practitioner, September, 1902, 297. 

^ Giorn. Roy. Soc. Hal. d'Ig., February, 1901. 

* Lancet, 1907, i., 510, ^ Zcil-scli. IIi/(j. Infikt. Kruhkh.. l<J(iS. f9, 29('. 



216 DISINFECTION AND STERILIZATION 

medium, but thoir effect is much less tlmn that of mineral acids 
(see Chapter X.). and, as is well known, their solutions quickly 
become mould}'^ in warm weather. Several algse, such as spirogyra, 
are very sensitive to these acids, a concentration of 0-1 per cent, 
citric acid proving effective in thirty minutes. 0-05 per cent, maleic 
or tartaric acid being algicidal within twenty-four hours. According 
to Low, even aspartic acid will kill algae after several days' contact. 
Citric acid Avas formerly recommended for sterilizing water. Christ- 
mas, in 1892, stated that cholera organisms were killed by 0-08 per 
cent, and tyjahoid by 0-10 per cent. Kitasato's figures for tartaric, 
citric, and maleic acids in nutrient media are, in per cents. : Growth, 
0-338; growth restrained, 0-384; no growth, 0-476. 

Aceto-acetic acid is slightly germicidal, concentrations of 0-1 per 
cent, being markedly antiseptic; succinic acid is slightly antiseptic. 

The influence of spatial arrangement is to be noted in fumaric 
and maleic acid; the latter is antiseptic for Penicillium glaucitm, 
whilst the former is not. 

Acid Peroxides. ' 

Acetyl peroxide and benzoyl-acetyl peroxide are stated by Freer 
and Novy^ to be strongly germicidal, as solutions corresponding to 
0-005 to 0-01 per cent, of active oxygen ( =0-037 to 0-074 per cent, 
of the former, or 0-056 to 0-112 per cent, of the latter) destroyed all 
known disease-producing bacteria, and even spores of B. mesen- 
tericus (which are not killed by 5 per cent, phenol), within a minute, 
while hydrogen peroxide solution containing 0-05 per cent, of active 
oxygen was without action on many bacteria, even in sixty minutes. 
Benzoyl peroxide had no oxidizing action, and was without effect 
on bacteria. A solution of acetyl peroxide was introduced under 
the name acetozone, but the title is now applied to a more stable 
and convenient mixture of the benzoyl-acetyl compound A\ith in- 
fusorial earth, said to be useful in typhoid, dysentery, and cholera.^ 
Alphogen or alphozoue, succinyl peroxide, is said to be a powerful 
germicide,'^ a solution of 1 : 5,000 killing B. typhosus in one minute. 

Alcohols. 

Tt lias long been known that "wood spirit." crude methyl 
alcohol, in a dilution of as low as about 5 per cent, can kill 
insects and most micro-organisms, and preserve perishable organic 
materials, owing to the tar products that it naturally contains. The 
alcohols themselves arc only efficient in a very much higher strength 
by coagulating albumin and (when absolute) by withdrawing water. 
Fowler gives the R.W. coefficient of absolute (ethyl) alcohol Avith 

1 Arn.er. Chem. J., 1902, 27, 161. 

2 Lancet, 1904, ii., 1160; Brit. Med. ,/., 1907. i., 634. 
•■' Brit. Med. J., 1905, i., 1150; Lancet, 1905, i., 367. 



ALIPHATIC DERIVATIVES 217 

B. typhosus as 0-03;^ Wirgin- has tested methyl, ethyl, butyl, and 
amyl alcohol, with anthrax spores and S. pyog. aureus, and concludes 
that the disinfectuig power is low, that it increases with the molecu 
lar weight, and that there is scarcely any action on dry spores. 

Tsukamoto has compared the various alcohols in their action on 
infusoria; in this case also their lethal powers increase with the 
number of carbon atoms. ^ The minimum concentrations required 
were found to be for methyl and ethyl alcohol 2 to 3 per cent., for 
jDropyl alcohol 1 per cent. Normal butyl alcohol was found to be 
more active than the iso-, and this more than the tertiary alcohol. 
Amyl alcohol 0-01 per cent, and allyl alcohol 0-005 to 0-01 per cent, 
were found to be strong disinfectants for these micro-organisms. 
The tertiary alcohols are very weak germicides ; thus propyl alcohol 
is a stronger disinfectant than tertiary butyl, and butyl stronger 
than tertiary amyl alcohol. 

It has been suggested to add alcohol vapour in steam disinfection, 
but Siege* finds no advantage. Hand disinfection "sdth alcohol is 
not reliable.^ Hansen*' found that epidermal bacteria, especially 
in suppurating eczema, when moist, are destroyed in one minute 
by absolute, and in most cases by 50 to 60 per cent, alcohol (see 
Chapter VI.). In many cases a 55 per cent, alcohol solution exerts 
the maximum germicidal activity. 

Glycerol in strong solutions (25 per cent, and upwards) is anti- 
septic, but in weaker ones it rather promotes the growth of bacteria. 

The esters such as ethyl acetate, ketones such as acetone and 
pinacone, exert little if anj' direct germicidal action. 

Thio Derivatives. 

The replacement of oxygen by sulphur in organic alij)hatic com- 
pounds brings about a slight enhancement of the antisejitic powers. 

According to Low, methyl sulphide has but little action on algse 
and diatoms. Methyl mercaptan in concentrations of 0-1 per cent. 
Avill destroy certain organisms such as diatoms, but small infusoria 
are not aflected by it. 

/NH.C3H5 

Thiodin or Tiodine, C==S has been claimed as a power- 

\NH2(C2H5)I 
f ul germicide, but no comparative data are given. It would ])robably 
compare unfavourably with the more usual germicides. It is pre- 

^ See Hewlett's " Bacteriology," 1908, p. 341. 

2 Chem. Zentr., 1903, i., 50; Zeitsch. Hycj., 1904. 46, 149. 

3 See Richardson, Med. Times Gaz., 1899, 2, 70o. 
* Chem. Zentr., 1902, i., 130. 

5 Goenner, Harrington, Boston Med. J.. Max '21, 1903. 
« Gentr. Bakt., 1907, 466. 



\ 



218 DISINFECTION AND STERILIZATION 

pared from thiosinamine anrl othyl iodide, the former being used 
hypodermically for lupus. 

Allyl isothiocyanate, mustard oil, has figured in a number of 
patents, and is capable of killing man}^ organisms, but not economi- 
cally. 

The xanthogenic acids are stated to be disinfectant and strong 
preservatives.^ 

Ichthyol and its derivatives are dealt with in a subsequent 
section (see p. 279). 

Aldehydes. 

Substances containing the aldehydo grouping — C^_ are 

germicidal when the grouping is labile or active ; in aldehydo sugars 
no action is to be observed, whilst the simpler aldehydes are bj' no 
means indifferent germicides. 

Formaldehyde is found in commerce as the 40 per cent, solution, 
formalin, and is antiseptic and germicidal, being official in the 
British, German, Austrian, Belgian, and Japanese pharmacopoeias. 
Formalin diluted ten times is used for embalming and for preserving 
bodies for dissection and museum sjoecimens, but for antiseptic work 
generally a much weaker solution is sufficient. The uses of formal- 
dehyde in food preservation and room sterilization have already been 
referred to. One of the Avriters and Dr. Foulerton have proved that 
1 in 50,000 of formaldehyde ( = 1 in 20,000 of formalin) suffices to 
keep milk sweet for twenty-four hours even in A\'arm weather with- 
out injury to health.- Apparently because experiments with larger 
doses showed effects on nutrition, the British Departmental Com- 
mittee on Preservatives in 1901 recommended " that the use of 
formaldehyde or formalin or preparations thereof in foods or drinks 
be absolutely prohibited." And yet its agency in the preservation 
of foods is as ancient as that of salt. The disinfectant and preserva- 
tive power of wood smoke is in part due to formaldehj'de, which is 
present on the surface of smoked provisions. H. WilP gives forma- 
lin a very high place among brewery disinfectants, and notices, like 
other observers,^ that it is more powerful against bacteria than 
against yeasts and mould fungi. Limits recorded as preventing 
development are: Sarcinse and bacteria 0-003 to 0-031, yeasts 0-007 
to 0-062; moulds 0-031 to 0-125 per cent. In faintly acid solution 
it appears to be slightly more effective than M'hen neutral.^ 

^ Lewin, Virchow's Archiv, 1878, 78. 

2 Pub. Health, May, 1899; Lancet, 1899, 1427, 1071. 

3 Zeitsch. Brau., ]"90;j, 28, 330, 347. 

4 Kinzcl, Slater and Rideal, Lancet, April 21, 1904. 
^ Annali di Farm., 1899, 8, 325 



ALIPHATIC DERIVATIVES 219 

Advantages of formaldehyde in disinfection are: (1) That it can 
be easily applied in the form of gas or vajiour for fumigation ; in the 
liquid condition as spraj^, wash, dipping, or in higher dilutions as an 
antiseptic ; or in the solid form as its polymers or mixtures; (2) that, 
unlike mercuric chloride and many other agents, it is not throwTi 
out of action by albuminous matter or by other chemicals; (3) that 
it is effective in strengths that are not irritant or poisonous, and do 
not injure fabrics or metals. Rosenau states that in quarantine 
stations large quantities of bulbs, roots ^ nuts, fniits^etc, coming 
from plague or cholera infected regions are disinfected by immersioTi 
in a 5 per cent, solution of formalin, which does not injure the food 
value and retards decay. In surgery formaldehyde and its prepara 
tions have been of wide service. Salter^ states that it rapidly kills 
the fungus of ringworm. As pigment or sjway (1 to 2 per cent, 
formalin) it has been successful in diphtheria; in such strengths it 
quickly kills other non-sporing organisms, including, according to 
E. Blake, the staphylococcus of eczema. In most cases a | per 
cent, solution is sufiticient. Geronzi found that the addition of 5 per 
cent, of sodium carbonate to the 5 per cent, formalin which he suc- 
cessfully used for obstinate ear disease increased the tolerance and 
enhanced the germicidal power- fc/., however, ante). 

Bokorny^ has noted a very interesting case of selective action 
with formaldehyde : a 0-05 per cent, solution destroys yeast, but not 
the enzymes; 0-1 per cent, destroys zymase; and 1 per cent, destroys 
the cell, but not invertase; it is thus possible to prepare an inverting 
but non-fermenting yeast. 

Paraform, paraformaldehyde, trioxymethylene, or trijormol, 
is a solid polymer, only slightly soluble. Although its germicidal 
power is rather low, its R.^V. carbolic acid coefficient being about 
0-7, it is the basis of many internal disinfectants, mostly of German 
origin. Its antiseptic power, it is stated, is equal to that of 
/:J-naphthol. These are so compounded as to liberate formaldehyde 
slowly, and act rather as an internal antiseptic, preventing the 
growth of organisms — e.g., staphjdococci or coliform organisms — 
than as a germicide. 

Formaldehyde forms a white solid crystalline compound \\i\\\ 
ammonia, known as hexamethylenetetramine, and this forms the 
active ingredient of a large number of disinfectants. Home of these, 
together with those containing formaldehyde or its solid polymer, 
trioxymethylene, may be mentioned : 

^ Guy's Hospital Gazette, October, 189G. 

- Arch. Ital. d'Otologia, 1903. 

3 Allgem. Brau. llopf. Zeit., 1918, 58, 1093. 



220 



DISINFECTION AND STERILIZATION 



Formaldehyde Disinfectants. 



Forinol, Formt/sol, 
McthyluL Stersol. 



Hexamethylenetetramine 
Disinfectants. 

Per se as. 

Holzeti, Camolin, Aminoform, Cystogen, Cystamine.. 
Formin, Uritine, Urotropin. 



With Inorganic Derivatives. 

Fni'inaldehyde in sodium glyceruborate Di-iodide- — Novoiodin. 
- — Boroform. Triborate — Borovertin. 

.\1 uminium silicate — Dreiaform. Dichromate — Chromojnrm. 

Acid phosphate — Hexamitrine. 
Perchlorate. 

Antimonyl tartrate utilized 
trypauocide. 



Iodoform — Ekaiodform. 
Acetamide — Formicin . 



With Aliphatic Derivatives. 

Dibromiodo — Chrysoform. 
Hexamethylenetetramine 1 molecule, 

sodium acetate 2 molecules — 

Cystopurin. 
Iodoform — lodoformin. 
Anhydromethylene citrate — Helmitol. 
Aluminium acetocitrate — A cetoform. 
Bromethylate — Brotnaline. 
Sodium citrate — Forininrol. 



With Aromatic Derivatives. 



Phenol — Ph e nylojorm . 
Phenol — Carboformal. 
Phenol — Phenyform. 
Resorcinol — Polyjormin . 
Resorcinol — Resorci noform . 
Guaiacol — Guaiaform, Geo form. 
Acetylated guaiaform — Engvform. 
Thymol — Thymoform. 
Thymol — Thymoloform. 
Cresols and potash — Lysoform. 
Creosote — Creofor'm, Creosoform. 
Tar — Empyroform. 
Pitch — Pittylene, PixmetJiylenale. 



Resorcinol — Hdraline. 

Guaiacol. 

Salicylate — Saliformin. 

Salicylsulphonate — Hexal and Neoliexal. 



Sulphonate. 

Eugenol — Eugenoform. 



Lactose — Steriform and Stcrisol. 

Dextrin — Dextroform. 

Milk sugars — Formamint. 

Starch — A mylojorm . 

Starch and io&mG—AmyloiodoJorm 



Carbohydrates. 

Milk sugar, sodium sulphate, chloride, 
and sulpliate — Bonal. 



Casein — Proteol. 

Gelatin — Collaform, Glutoform, Olntol. 
Chlor o methyl menthy 1 ether — Forma n . 
Menthol and trioxymethylene— TAo/a- 

forin. 
Terpenes and allied substances. 
Condensed with haematoxylin — Lysav, 

AUmatein. 
Ichthyol and sulphuric acid — Ichtho- 

form. 



Miscellaneous. 

Al bu m i n s i 1 ver — A rgaldin . 
Camphorate — Amphotropin. 



Nucleate — Nucleohexal. 



ALIPHATIC DERIVATIVES 221 

„ T^ Hexamethyleketetramine 

FORMALDEUYDE DiSINFECTANT.S. DlHINFECTANTK 

Tannins. 

Ciuchotaanic acid — Chcmojorm, Quiiio- 

form. 
Tannin and phenol — Tanninphcnol- 

mcthane. 
Dibromtannin — J'annohrominc. 
Tannin and thymol — Tannothymol- 

methane {Tannothymal). 
Gallotanuic acid — Tan no form. 
Tannin creosote — Tammicrcosojorvi,. 
Tannin guaiaool — Tannoguaiaform. 

The higher aldeh3'des are by no means so active as formaldehyde, 
the germicidal activity sinking with an increase in the molecular 
weight, but many antiseptic solutions have been j)repared with 
acetaldehyde and its polymer (CHgCHO).^ as the active base. 
Acetaldehyde in sufficiently concentrated solutions is germicidal 
to anaerobic organisms, whilst it has been stated that algse are killed 
after twenty-four hours' contact with a 0-02 per cent, solution. 

o r* IT 

Amidoacetal, CH2.NHo.CH<^q"p-tt^ will destroy diatoms and in- 
fusoria in a concentration of 0-1 per cent, within fifteen hours. 

Acrolein, although toxic, ajDjDcars to possess no germicidal ac- 
tivit}', and is scarcely of any value as an antiseptic.^ 

According to Conradi,- chloral hydrate is germicidal to B. typho- 
sus, and it is exceeded in activity by bromal hydrate. Butyl chloral 
hydrate is a stronger germicide than bromal or chloral hydrate. 

Acetone chloroform, C(CH3).2(CCl3).OH, or chloretone, is not only 
antiseptic, but a good disinfectant. 

Amines and Amides. 

The methylamines, CHgNH.^, (CH3).^NH, (CH3)3N, are gaseous 
compounds, very soluble in water at ordinary temperatures, 
yielding powerfully alkaline solutions of an objectionable fishy odour. 
Klein found that a 1 per cent, solution is an effective germicide. 
Ethylamine,^ C2H5NH2, possessing similar properties to methylamine, 
has a carbolic acid coefficient of 1-27. 

Amylamine, (C5Hii)NH2, produced in the destructive distillation 
of animal matters, is antiseptic, but seems to j)ossess no special 
advantage. 

Ethylenediamine, C2H4(NH2)2, has been used in combination \\ith 
mercuric sulphate in sublamin as a hand disinfectant. It possesses 
the advantages of being easily soluble in water, docs not coagulate 

^ Lewin, Arch. exp. Path. Pluirm., 43, 301. 

2 Zeitsch. Bakt., 1, 47, 145. 

^ Morgan and Cooper, Eighth Int. Gong. Appl. Chem., 1912, 8, 150. 



222 DISINFECTION AND STERILIZATION 

albuminous substances nor precipitate soap, and is much less irritant 
than mercuric chloride. Its carbolic acid coefficient is low (0-03 to 
0-4). 

IsDamylamine has a carbohc acid coefficient of 2-8. 

Heptylamine, in which the partition coefficient ^ i^x^ft 

^ water solubihty 

is high, was found by Morgan and Cooper to have the remarkably 

high coefficient of 24-3. 

Amides. — Loew and Bokorny^ investigated the effect of a number 
of amides and amido compounds on alga?. They showed that algi- 
cidal powers were, in general, dependent on the presence of NHg 
groups, although, as we shall have occasion to note, these regulari- 
ties do not obtain in the aromatic series. 

TVIT TVTT 

Urethane, ^^<^q(j"^ has no action on algae; urea, CO<l-^jj^ 

NTT 

was algicidal after several days; whilst guanidine, HNC-<-vj-tt^ 

destroyed the algae withm a few hours. 

IVTT P TT 

Ubaldi^ noted that C!0<CatttY,^tt^ was inactive, but states that 

NH ^ ^ 

1 per cent. ^0<^^tt^/-i tt was as antiseptic as sublimate. 

/NH-CH^ 
Hydantom, Q0( \ and creatine, HNC<i^^2 ^nnw 

on the other hand, exerted no algicidal activity. 

Chloroform, CHCI3, in solution is a strong antiseptic, whilst its 
vapours are actively germicidal ; but its action on animals confines 
its use to preserving medicinal infusions. A 5 per cent, solution 
in spirit is sold as a preservative. 

Bromoform, CHBrg, is a similar, but more expensive, less vola- 
tile, equally soluble, and less stable compound. 

Iodoform, CHI3, is a yellow crystalline powder of persistent and 
disagreeable odour, and is much used in hospitals for dressings, etc., 
in the form of gauze, or as a fine j)owder for dusting wounds, and in 
bougies -with cacao butter or in emulsion of 10 to 50 per cent, with 
glycerine water and gum tragacanth. It owes its germicidal and 
antiseptic powers to the gradual Hberation of iodine by the alkaline 
wound secretions. Iodoform itself gives rise to iodoform poisoning, 
owing to the too raj)id evolution of iodine. A great number of 
organic iodine derivatives have accordingly been prepared, which 
are intended to liberate the iodine contained therein at a slower rate 
than iodoform. 

1 J. pr. Ckcm., 36, 272. '^ Ann. Chim. Farm., 14, 12'J. 



ALIPHATIC DERIVATIVES 223 

During the period of the war both pastes and impregnated gauze 
containing bismuth subnitrate (1 part), iodoform (2 parts), and 
paraffin wax were used extensively. The germicidal action is due 
partly to the liberation of iodine by oxidation, and partly to the 
nitric acid formed by hydrolysis of the bismuth subnitrate.^ P^ven 
when used over large exposed areas, cases of iodine poisoning appear 
to have been very few in number. 

Organic Iodine Derivatives. 

Aliphatic Derivatives. 

Dibromo-di-iodohexainethylenetetramine — Chrijsoform. 
Ethylene periodide — Di-iodoform. 
lodoformin ethyliodide — lodoformal. 
Trioxymethylene iodoform — Eka-iodoform. 
Hexameth^denetetramine iodoform — lodoformin. 
a-y-di-iodopropane-/^-ol — lothion. 
lodomono-isovalerylurea — lodival. 

Aromatic Derivatives. 

7 

Tetraiodopyrrol — lodol. 

Di-iodo-^j-phenolsulphonic acid — lodozol. 

Di-iodothymol — Aristol. 

Iodized thymoloform — lodothymoloform. 

Di-iodobutylcresol ioditle — Eiirophen. 

Tri-iodometacresol — -losophan. 

Mono-iodocresol — Traumatol. 

Methylene disalicylic iodide — Formidm. 

Di-iodosalicylic methyl ester — Sanoform. 

o-iodoanisol — lodoanisol. 

/)-iodoxyanisol — ■Isoform. 

Tri-iodoiJhenacetin — lodophenin. 

Iodine and guaiacol in sodium iodide — lodocol. 

Tetra-iodophenolphthalein — losophen. 

Mono-iododihydroxybenzene formaldehyde — 

C6H3(OH)J.HCHO,2HoO. 

Tannins and Miscellaneous. 

Dihydroxy-iodide methyl gallol — lodogullicin. 

Bismuth oxyiodogallate — Ibit. 

Tetra-iodopyrrol — lodol. 

Iodized albumin — lodolen, lodalbacid, lodalbin, lodigons. 

Iodized gelatine — lodylojorvi. 

Iodized casein and bismuth — lodomenin. 

lodlecithin . 

Iodized gluten — lodglidin. 

Iodized peptone — Beiyoii.. 

Quinine iodine substituted derivatives — Chiniodiiie. 

^ Chaiiibur.s and (jarrafc, Lancd, March ;}, 1917. 



224 DISINFECTION AND STERILIZATION 

Quinoline. 

3-iodo-4-hydroxoquinoline-l-sulphonic acid — Loretin. 
Quinoline chlorometliyl iodochloride — lodolin. 
lodochlorhydroxy quinoline — Vioforni. 

Miscellaneous. 

Iodized arachis oil — lodin. 

Iodized sesame oil — lodipin. 

Calcium monoiodobehenate — Sajodin. 

Iodine and camphor combined with white clay — Isapogen. 

A few attempts have been made to preimre other organic iodine 
derivatives Avhich should liberate iodine slowly in the tissues, be 
antiseptic, and facilitate granulation. Ethylene tetraiodide or 
di-iodoform, Cgli, which forms the basis of a few iodoform substitutes, 
liberates iodine even more rapidly than iodoform itself. More suc- 
cessful are alkjd ammonium iodide iodine addition compounds; 
good results have been obtained with substances such as tetra- 
methyl ammonium periodide, N(CH3)4l.l2. The unsaturated fatty 
acids, their salts and esters, have likewise been used as vehicles of 
iodine in such compounds as Upojodin, C19H37CI : CT.COOCgHg.^ 
Sajodin^ a derivative of iodobehenic acid, (C22H4202l2)2Ca. Both 
iodohion (di-iodohydroxjqoropane, C3H5I2OH), and archiodin^ mono- 
iodoisovalerianyl glycocoU urea have been suggested as substitutes 
for tincture of iodine. 



BIBLIOGRAPHY. 
Berg, W. N.: A Theory of Internal Disinfection with Na.scent Formaldehyde, 

Proc. Soc. Exper. Biol, and Med., 1914-15, 12, 145-147. 
RuHLAND, G. C. : Formaldehyde Fumigation a Failure, Wisconsin Med. J., 1914-15, 

13, 477-479. 
Leclair, E., and Logie, G. : Dosinfection ct desinsection, emploi d'un melange 

de vapeuLs de formol et de benzine. Bull. sc. pharmacol., 1916, 23, 40. 
HiLli, J. R. : Formaldehyde and Potassium Permanganate Fumigant, Pkurm. J., 

1916, 97, 589. 

Haury and Cordier: Desinfection par le formol et le permanganate de potasse, 

Arch. Med. Pharm. Mil., 1906-17, 508-510. 
Tanon: Experiences sur la sterilization par le formol, Lancet, 1917, ii-, 395. 
Crandall, R. p. : Barium-Formalin Method of Disinfection, U.S. Nav. Med. Bull., 

1917, 2, 519. 

Formaldehyde, J. Soc. Chem. Ind., 1918, 781a, U.S. pat. 1,279,524 (Process for 
Liberating Gaseous Formaldehyde); /. Soc. Chem. Ind., 1918, 191a, Formalde- 
hyde and Potassium Chlorate as a Disinfectant. 

1 Loeb and Veldin, Ther. Mon., 1911, 201. 



CHAPTER XII 
THE CHEMICALS EMPLOYED IN DISINFECTION— (7owf mi/ erZ 

ORGANIC SUBSTANCES : AROMATIC DERIVATIVES. 

It has long been known thcat the varieties of tar have antiseptic 
and preservative properties; hence the use of coal tar for coating 
wood, and of wood tar for ropes and sacking. Coal tar consists for 
the most joart of a mixture of " aromatic " compounds derived 
from the hydrocarbon benzene, CgHg. They are more or less vola- 
tile; many have offensive odours and act as narcotic poisons. This 
poisonous action may render them disinfectant Avhen used in suffi- 
ciently large quantities. 8ome coagulate albumin, and are caustic 
like phenol. A few are soluble in water, and these have the most 
immediate physiological power. As far back as 1573 Bishop 
Berkeley extolled the virtues of tar-water for nearly everj^ ailment : 
but its use is now replaced by more definite prejiarations. 

B}' treatment with acid and alkaline solutions in succession, the 
tars are separated into three groujjs of bodies: 

1. Hydrocaxbons, such as benzene, toluene, xjdene. naphthalene, 
anthracene, etc. These are neutral bodies, insoluble in water, 
alkalies, and acids. Most of them, however, can be emulsified by 
heating with a solution of ordinary or resin soap, with or without 
the addition of wood spirit. The more or less clear brown syrup 
turns milky and white with Avater, the hydrocarbons being pre- 
cipitated in minute oily globules, which slowly rise as a scum to the 
surface, leaving a strongly alkaline solution in the soaps. All these 
mixtures smell of tar, and are in different degrees antiseptic, but 
less so than the phenols. They are known in commerce as " neutral 
tar oils." Specifications for disinfecting powders generally demand 
their absence, and, in fact, they are looked upon generally as a 
detriment, or even as an adulteration, if present in any quantity 
in disinfectants. The hydrocarbon benzene, CgHg, and its higher 
homologues toluene, C^Hg, etc., have no antiseptic value. Farrel 
and Howies^ found that threads infected with B. typhosus were not 
sterilized by six and a half hours' exposure to benzol. Benzene soap 
has no germicidal power. - 

1 ./. Soc. Dyers Col.. 1908, 24, 108. ~ Ibid., WG. 

22.1 15 



226 DISINFECTION AND STERILIZATION 

Naphthalene, CjoHg, and anthracene, CigHjQ, when pure, are 
white crystalline solids of greasy feel and tarry odour, slowly volatile, 
insoluble in water, and feebly antiseptic. Naphthalene is used as 
an insecticide, and is sometimes employed locally in scabies as a 
10 to 20 per cent, solution in oil. It is to be avoided in cases where 
large surfaces are exposed, but has been used internally^ and as an 
antiseptic for wounds.- Its derivatives will be further considered 
(p. 252). Naphthalene has been much used as the basis of cakes 
or blocks sold very cheaply as " disinfectants " to hang up over 
sinks and in closets, and to place in the basins of urinals. Some are 
said to contain " camphor and eucalyptus." The camphor blocks 
certainly prevent the urinous smell, partly by masking it and partly 
by retarding the ammoniacal fermentation, but they are of no use 
as disinfectants. 

2. Phenols, or so-called " tar acids," carbolic, cresylic, etc. 
They are hydroxy derivatives of the aromatic hydrocarbons, and 
combine with caustic alkalies to form carbolates, etc., soluble in 
water, from which acids again liberate the phenol. The series 
includes phenols, cresols, and higher homologues; the last are 
present in the fractions of higher boiling-point, and form unstable 
compounds with alkalies which are even decomposed by water; 
hence their solutions turn milkj' on dilution. The}' are the basis 
of a large number of proprietary preparations, and will be described 
further under phenol, cresol, etc. 

3. Basic substances are extracted from coal tar by treatment 
with acids; they contain nitrogen, and are allied to ammonia. They 
are mostly soluble in water, and comprise pyridine and its homo- 
logues, with pyrrole, carbazol, quinoline, acridine, aniline, and other 
bases in small quantities. 

-J Phenols. 

Phenol or carbolic acid, CgH5(0H), is the simplest member of 
the group of phenols or hydroxyl-benzene derivatives, and is com- 
mercially known as carbolic acid.^ The phenols all contain hydroxyl 
united to the " aromatic " nucleus or benzene ring of carbon atoms, 
and are more or less antiseptic. Most of them coagulate albumin, 
and are therefore styptic; they are poisonous in different degrees, 
and thus, if in sufficient quantity, may be true disinfectants. The 
carbolates are alkaline, odorous, and somewhat caustic ; acids, even 
carbonic, render their solutions turbid, separating the jjlienols as 
an oily layer if the solution is moderately concentrated. Fuch 
substances, made with lime or magnesia, constitute a number of 

1 Amer. J. Pharm., 1884, G45. - Squire's "Companion," 1890, 289. 



AROMATIC DERIVATIVES 227 

the "disinfecting powders," which slowly give off the phenols on 
exposure to air, leaving behind the inert carbonates of lime and 
magnesia. The earthy bases then only act as a vehicle, and any 
undue excess of them must be considered as an adulteration. The 
pure compounds are not used, as they are deliquescent, caustic, and 
too rapidly soluble. The powders are usually valued, and sold as 
containing a stated percentage of the phenol or phenol equivalent. 
Many so-called disinfecting powders now in the market are supposed 
to contain lo per cent, of phenol, when in reality they possess only 
a trace; moreover, even the best deteriorate on exposure to air, and 
may become inert, so that their activity should always be controlled 
by analysis. 

Phenol itself is prepared from tar distillates, and in the crude 
state is a dark oily liquid containing also the higher homologues, 
cresol, xylenol, cumenol, durenol, besides neutral tar oils of less 
disinfecting power. " Synthetic " carbolic acid, made from benzene 
^and free from cresol, etc., has been sold, but its price is somewhat 
prohibitive. Pure phenol forms colourless crystals, mth a tendency 
to turn red in the light. It melts at about 40-5° C. and boils at 
181 -5° C, and therefore is not easily volatile. It can be volatilized 
more rapidly by melting and then dropping on to a heated shovel- 
not too hot, or it is liable to catch fire (Calvert). The vapour is apt 
to cause severe headache, giddiness, and nausea. Crystals of phenol 
are very hj^groscopic, and may contain up to 8 per cent, of water. 
Much uncertainty exists as to the exact melting-point of pure 
phenol, a matter of great importance in the testing of germicides 
(see Chapter XL). The most recent determination by Leroux^ 
gives 40-85° C. as the melting-point; the presence of 0-2 per cent, of 
water lowers the melting-point to 40-00° C. 

A clear, aqueous solution saturated in the cold contains between 
and 7 per cent, phenol. It is certainly antiseptic ; but as to its dis- 
infecting power, opinions have been diverse. McDougall and Calvert 
extolled it above all other disinfectants, but the latter observer, 
although he states that 1 in 200 ]irevented the ])utrefaction of meat 
juice for six days, yet acknowledges that when added in that pro- 
portion to already putrid beef juice or egg albumin, it had no effect 
on the organisms present. The vapour also ])roduced no effect 
during twenty-four hours on vaccine lymph. Miguel found that 
the vapour of phenol, "after fifteen or twenty days of action at 
20° C, is absolutely incapable of destroying the vitality of bacteria," 
and that 3-2 grammes of phenol are required to prevent growth in 
a litre of beef-tea. iJelbret^ states that in comparing phcjiol \\ith 

1 ./. Pharm. Chem., 1919, 20, [vii.|, S8. 
' Acad, de Scievcc.'<. March, lOlti. 



228 DISINFECTION AND STERILIZATION 

mercuric chloride and hydrogen peroxide by their effect on pua. he 
found that 2 per cent, phenol in the pus produced sterility in six 
cases out of fifteen, 2 per cent, mercuric chloride in two cases out of 
nine, and hydrogen peroxide only in one case out of six. Hypo- 
chlorites were found ineffective under these conditions. 

Sclieurlen A\'as the first to observe that an aqueous solution of 
phenol is very considerably increased in activity by the addition of 
salts; alcohol and caustic soda, however, when added to phenol, 

diminish its activity in conformitv with the alteration in the , I 

watci! 

partition coefficient. Pasteur and Lister strongly advocated its use 

in surgery where antiseptic action is mainly aimed at. Phenol was 

extensively used by Crookes under the sanction of the Cattle Plague 

Commission. His report estimated its value in destroying the 

infectious matter as very high (1867). 

Koch also remarks that " carbolic acid also kills, if of consider- 
able strength and acting for a long period." He observed that 
solutions of carbolic acid in oils do not possess the same disinfecting 
value as solutions in water. This is important in view of the 
frequent use of carbolized oil in surgery, and will be referred to later. 
When disinfection is required to be completed in less than twenty- 
four hours, which is generally the case, Wolffhugel and Von Knorre 
found carbolic acid useless. In Koch's later experiments silk 
threads with anthrax spores were placed in carbolic solution of 
various strengths. A 5 per cent, solution killed the spores in two 
days, whilst sporeless bacteria, obtained from fresh blood, were 
killed by 1 per cent, solution, but not by | per cent, solution, as 
proved by inoculation. "As an antiseptic, phenol solution 1 in 
850 entirely prevented the development of anthrax spores; 1 in 2,250 
caused marked hinderance. Other bacteria are less affected. The 
vapour at ordinary temperatures, even when allowed to act for 
six weeks, had no effect on spores, but at 55° C. many were destroyed 
in half an hour. After three hours there was very little germinating 
power, after five or six hours all were killed. Other disinfectants 
act similarly at high temperatures."^ 

Klein observes that phenol (1 in 400 or 500) in nutrient solutions 
had a decidedly restra,ining power, but he emphasizes the fact that 
the spores are only " stunned," not killed, because, if removed and 
inoculated into an animal, they rapidly recover and cause death. 
He continues, " as is obvious, according to the nature of the bacillus, 
the strength of the solution, and the time of action, the result 
varies. For instance, mature B. anthracis is killed by 5 per cent, 
phenol in five minutes, but is not injured by 1 per cent, in five 
1 Mitth. Kais. Ges^mdh., December 3, 1882. 



AROMATIC DERIVATIVES 229 

minutes." Other observers have found that resistant spores are 
not killed by 5 per cent, carbolic acid, and in the author's labora- 
tory anthrax spores have germinated in less than twentj'-four hours' 
incubation after four days' immersion in a 5 per cent, solution 
Crookshank obtained favourable results on the tubercle bacillus 
by inhalations of carbolic vapour.^ It is well known that certain 
organisms, especially those of the coli group, and to a lesser degree 
B. typhosus, are capable of growth in the presence of small quantities 
of phenol;- culture material containing 1 in 2,000 carbolic acid is 
sometimes employed in bacteriology for the isolation of these 
organisms. TyjDhoid and coli organisms are rapidly killed by 
carbolic acid exceeding 1 pe r cent . 

Solutions of yjhenol, aniline, or o-toluidine, which have been 
exposed to the air and light, and have consequently become coloured, 
show a slight elevation in germicidal activity.^ 

The value of phenol for hygienic purposes may be summed up 
as follows: 

1. In a strength of 1 in 400 it is a powerful antiseptic, restraming 
putrefaction when started, and preventing it for a long time "w hen 
not commenced, but in this respect it is far inferior to mercuric 
chloride. 

2. To kill bacteria with any certainty, a greater strength than 
1 per cent, must be employed. With spores, such as those of 
B. anthracis, phenol is useless, as they are apparently unaffected 
by a saturated solution. 

3. It does not absorb sulphuretted hydrogen nor ammonia, 
hence it is not a deodorant. 

4. Its persistent odour is a decided disadvantage, as tlie smell 
remains even when the quantity is utterly insufficient. 

5. For treatment of sewage it is a failure, even in proportions 
practically impossible. Moreover, it renders the material useless 
for manurial purposes. In Japan, after a cholera outbreak, the 
Government instituted some experiments to elucidate this point, 
and clearly showed that "a solution of 0-05 gramme of phenol in 
100 o-.c. of water weakened the germinating power of the seeds, and 
with a solution of 0"! per cent, only one-third of the possible seeds 
germinated, and in all cases the acid delayed the process of germina- 
tion." 

(). In surgery it is of considerable value. Lister has pointed out 
that it had a powerful affinity for the e])idermis, jienetrating d('e])ly 
into its substance, and mingling with fatty mattei- in any ])i()]ior- 

' Bacteriology, 1887, p. 151. 

- Chantenes.se and Widal, Gaz. Hcbdomadnirc, 1887. p. 14(); alh.o Ann. Inst. 
Pasteur, October 25. 1S!)(». 

" Thalhimer and Palmer, J. Inject. Dm., I'Jli, 9, 17-J. 



230 DISINFECTION AND STERILIZATION 

tion, whereas mercuric chloride required a special cleaning of the 
skin, as it could not penetrate in the slightest degree into anything 
greasy. Though it avoids the danger of mercurial poisoning, if 
used too strong it may itself be absorbed and cause dangerous 
symptoms. For aseptism (prevention), as against antiseptism 
feure), in surgery it has, therefore, a distinct field of usefulness. 

Polyhydroxybenzenes. 

Certain generalizations concerning the influence of the — OH 
groups entering the benzene ring on the germicidal and antiseptic 
powers of the compound can be made. 

Di- and Tri-hydroxybenzenes. — The antiseptic properties of the 
polyhydric phenols are less than those of phenol, whilst the toxicity 
toman increases with the number of — OH groups inserted, although 
the isomeric compounds show exceptions; thus phloroglucinol is 
less poisonous than pyrogallol. With the lower fungi, the poly- 
hydroxy derivatives are less poisonous than phenol. ^ 

Resorcinol, or "resorcin," meta-dihydroxybenzene, C6H4(OH)2, 
coagulates albumen, forming a white precipitate. It only begins 
to be toxic in very large doses, 10 to 20 grammes per day internally 
for an adult, while a 2 per cent, solution is highly antiseptic (ValHn). 
Andeer,- Callias,^ Dujardin-Beaumetz,* Lichtheim of Berne, and 
others, have experimentally demonstrated that resorcinol is a 
powerful antiseptic. Callias proved that fermentation was pre- 
vented, and many animal liquids preserved, by 1 per cent, of 
resorcinol, while to keep milk required at least 2 per cent. As to 
its internal action, Andeer, after a dose of 10 grammes of resorcinol, 
experienced vertigo, dizziness, loss of smell, and salivation, the 
symptoms disapi^earing in five hours with no after-effects. It is, 
therefore, far less poisonous than phenol. Dr. W. Murrel^ also 
reported on its internal use. Morgan and Cooper'' determined the 
carbolic acid coefficient against 5. tyjyJiosus, and found it to be 0-29. 
As an antiseptic the dose is 5 to 20 grains. Weak solutions (1 to 
3 per cent.) harden the skin, while stronger ones (10 to 50 per cent.) 
macerate and destroy it.^ Internally it has caused untoward 
effects.^ 

1 K. Yabe, Bull. Coll. Agrlc. Tokyo, 1894, 2, 73; Biernacki, Chcin. Soc. Abstr., 
1893, ii., 32; Loew, Nat. System J. Giftwirk. 
- " Ueber das Resorcin," Wurtzbvirg, 1880. 
^ "Resorcin en Therapeutiqnc," Paris, 1881. 
« Bull. Therap., June and July, 1881. 

5 Med. Times and Gaz., 1881, p. 486. 

6 Eighth Inter. Cong. App. Chem., 1912, 8, 150. 

■^ Helbing's " Modern Materia Medica," 1895, p. 146. 
8 Lancet, 1898, ii., 779, 836. 



AROMATIC DERIVATIVES 231 

Anusol is a bismuth iodoresorcin sulphonate, having a specific 
action on the rectal mucosa. It is described as a powerful disin- 
fectant and deodorant for wounds, and, when used in suppositories, 
is free from unpleasant by-effects. 

Catechol, or pyrocatechin, ortho-dihydroxybenzene, CgHj(OH),, 
like almost all products of destructive distillation, is antiseptic, 
and a more powerful germicide than resorcinol. 

Morgan and Cooper find its carbolic acid coefficent to be 0-48, 
but a 1 to 2 per cent, solution can be used as a spray in diphtheria 
and whooping-cough, and a 5 per cent, ointment in skin diseases. 
It is also used for removing dandruff from the scalp. Euresot is 
the mono-acetyl derivative. It is used in cases of acne, alopecia, 
and seborrhea, and is said to be milder and more lasting in its 
antiseptic action than resorcinol. 

The third dihydroxybenzene. hydroquinone or quinol, is the 
'most active. Its internal use in tyj^hoid has been suggested in 
doses of 3 to 8 grains. The carbolic acid coefficient is stated to 
be M. 

J. R. Duggan- investigated the relative amount of the three di- 
hydroxybenzenes required to prevent Bacillus subtilis from develop- 
ing in beef peptone. Taking phenol as 20, he finds the ratio of the 
three compounds ortho : meta : para = 20 : 25 : 30, whilst p;vTogallol is 
represented by 15. Ratios of action on pathogenic bacilli are 
different. 

Pyrogallol, or " pjTogallic acid," trihydroxybenzene, CgH3(OH)3, 
is inodorous, tastes astringent, and has less corrosive action than 
allied compounds. Its solution quickly turns bro-^-n in air, absorb- 
ing oxygen ; if an alkali be present, the action is almost instantaneous, 
the solution becoming dark bro\\'n. This projDerty leads it to lie 
destructive to "aerobic " organisms — those Avhich live in presence 
of oxygen. Bovet, of Neuchatel, first examined its antiseptic 
action,^ and found that a 2 per cent, solution prevented putre- 
faction, fermentation, and mould for some months, and that 3 per 
cent, was capable of killing bacteria. Two per cent, solutions 
have no injurious local action, and disinfect very well ; but it cannot 
be used internally, as it reduces and destroys the blood-corpuscles, 
causing haemoglobinuria. 

If the hydroxy] hj'drogen is esterified, the germicidal and anti- 
septic actions are lowered, the toxicity is also reduced. Etherifica- 
tion of the hydroxyl group — e.g., anisol phenetate — produces a 
similar dej^ressing effect. 

This is equally true for the polyhydric alcohols. 

1 D.R.P., 103,8.57; 281,097. - Amcr. Chcm. ./.. 7, <>2. 

3 Rev. d'hijg., 1879, 154. 



232 DISINFECTION AND STERILIZATION 

Guaiacol and its Derivatives. — Guaiacol, methoxy phenol or 
methyl catechol, C6H4fOCH3)OH, in odour and taste resembles 
creosote, of which it constitutes a large portion. Only 0-5 per cent, 
of it dissolves in Mater, but it is more easily soluble in alcohol, 
wood spirit, acetic acid, and in alkalies. Sodiura-guaiacol resembles 
sodium phenol. 

As the antiseptic value of wood creosote is due partly to the 
guaiacol which it contains, it is important to note that this ingre- 
dient was usually removed from foreign creosotes. 

The largest quantity (60 to 90 per cent.) exists in beech -wood 
creosote, but it also has been obtained by distillation of guaiacum 
resin, whence the name. 

Its physiological value was first pointed out by Seidel in 1880. 
It is now made synthetically from ortho-anisidine, a base obtained 
by the reduction of o-nitroanisol, formed by methylating o-nitro- 
phenol. It first excites, then paralyses, the nerve centres, and 
reduces the temperature ; therapeutically it is similar to jDhenol and 
pyrocatechol, but not so poisonous. Its carbolic acid coefificient 
(R.W.) is stated to be 0-9 (Martindale). Kenwood and Hewlett^ 
find it somewhat stronger than phenol (R.W. 1-2). 

To depress the toxicity of the — OH group in guaiacol, but at 
the same time to permit of slow hydrolysis with the liberation of 
the active germicide, a very large number of guaiacol derivatives 
have been prepared for internal treatment. These include ester 
salts of fatty acids such as eucol, guaiacol acetate ; guaiacol sebacic 
ester ; and monotol, the ester of ethyl glycollic acid . Of the inorganic 
esters, guaiacol carbonate {dnotal): phosphate, fhosplnitol; the 

/OCVH.OCH, 
phosphite, P==OCpH40CH3 and sulphate have been prepared. 

\OC6H4OCH3 
Einhorn and Heinz^ introduced a series of water-soluble salts 
stated to possess many advantages over all other guaiacol prepara- 
tions, the hydrochlorides of dialkyl-amino-acetyl-guaiacol such as 

the diethyl derivative, guaiasanol, CgH4<'Q nn^CIl N(C H ) HCI 
Amongst the aromatic preparations may be mentioned the cinna- 
mic ester, siyracol ; tannic ester, tanosol ; and benzoic ester, benzosol. 
Guaiacol ethers have likewise been prepared. Of this some- 
what smaller grou]i may be mentioned gnaianin. the glycerine 

OCH 
ether, Cc^i<Cr\A xr o '^ Avattn-soluble germicidal solid. Various 

])re]>arations of guaiacol leaving the — OH group luiprotected lia\(' 
been suggested, but the advantage of such preparations, ajmrt from 

1 J. Roy. Sun. Inat., 1900, 13. '" Arch. Fkarm., 1002, 240, 032. 



AROMATIC DERIVATIVES 233 

a possible increase in solubilit}^, from a germicidal or toxic stand- 
point is to be questioned. Thus we find gvaiaci/l, the calcium salt 
of guaiacol sulphonate, and guaiacol carboxylate or metboxy- 
salicylic acid^ claimed as antiseptics. The potassium guaiacol 
suljohonate is known as tJiiocol.- 

A fourth group of guaiacol derivatives includes derivatives of 
the — OCH3 group in the guaiacol nucleus, such as the antiseptic 

OH 
guaiacetin, CgH4<^QpTT nQQXTo and the calcium salt, calizibram. 

Guaiacol formaldehyde compounds are described under formalde- 
hyde. 

The hypodermic solutions known as Picot's, Pignol's, and 
Morel-Lavallee's contain guaiacol. It has been used for phthisis, 
administered in cod-liver oil or in weak spirit. J. J. Ridge finds 
,that a solution in olive oil, 1 part in 80, is valuable for anointing 
the skin in smallpox.^ Eugoform is an antiseptic dusting joowder 
made by the action of formaldehyde on guaiacol and subsequent 
acetylization. 

/ Creosol, or methyl guaiacol, C6H3(CH3)(OCH3)OH, is the chief 
ingredient of ordinary wood creosote. It resembles guaiacol. but 
has a higher boiling-point, is heavier, and less soluble. Its anti- 
sej)tic and germicidal power is said to be a little higher, as would 
be expected by nuclear substitution of an alkyl group. A 1 in 
150 solution kills S. pyog. aureus and B. typhosus in three hours 
(Wescott). 

In addition to nuclear alkvl substitution products of guaiacol, 

■ OH /^^ 

derivatives of guathol, ^^^i<Cp,ri tt and eugenol, CgHg. OCH3 

have been prepared, such as cetiocol or palmiacol. methyl-acetyl 

/OCOOCH3 
guathol ; and duotal, eugenol-methjl carbonate, C'6H3 OCH3 

OC3II5 
These do not appear to possess any advantages over guaiacol 
preparations, an increase in germicidal activity being most easOy 
obtained by alkyl nuclear substitution, as in creosol. 

Cresol or Cresylic Acid and the Higher Phenols. 

The higher phenols may be regarded as derivatives of phenol 
in which one or more of the hydrogen atoms of the " benzene 
ring " have been replaced by methyl or otlier fatty radicles. These 
substitution products form a homologous series of progressively 
increasing density and boiling-point and diiiiiiiishing s()]u])ility, 
of which the following are examples: 
1 D.R.P., -287: 900. - D.K.P., 132, 045. ^ Bril. Mtd. J., lOOX NC. -I.-IVI. 



234 DISINFECTION AND STERILIZATION 

Table of the Phenol Series. 



Si/iitcmatic Xamc. 



Commercial 
Name. 



Empirical 
Formula. 



Structural Formula. 



Phenol 

o-m- and /)-iuetl)yl-])hcii()l 

Dimethyl -phenols . . 
Trimethyl-phenols . . 
Tetramethyl-phenols 



Carbolic acid 
Cresols or 
Cresylic acids 
Xylenols 
Cumenols 
Durenols 



CfiHeO 

C7H8O 

CgHioO 
C9H1.2O 
C10H14O 



f'eHj.OH 

("fiH4(CH3).OH 

(•eH3(CH3)2.0H 

('6H2{CH3)3.0H 

C6H(CH3)4.0H 



Of all, except the first, several isomerides are known. They are 
all antiseptic; their relative value is not exactly known, but the 
cresols are decidedly higher than phenol. All dissolve in strong 
alkalies, giving soapy antiseptic solutions; these compounds in the 
higher members of the series are decomposed by water, yielding 
milky emulsions which slowly deposit the oil. The homologues are 
less poisonous than phenol, and are classed together as phenoloids. 

A mixture of these bodies from which phenol had been separated 
formerly constituted a waste product of the carbolic acid manu- 
facture under the name of " creosote oils," and was used for pre- 
serving timber, etc. They are difficult to separate by fractional 
distillation, and now in various mixtures they are largely used for 
disinfectants under a great number of fancy names. Some of 
them contain also the hydrocarbons, or neutral tar oils, and a few 
contain also the bases. 

The waste gases from blast furnaces, formed by the destructive 
distillation of the upper layers of coal and bituminous iron ore, 
when cooled, deposit large quantities of empyreumatic products, 
from which is manufactured on a large scale in Scotland the 
mixture called " blast-furnace creosote oil " for creosoting timber. 
It contains 20 to 35 per cent, of phenoloid bodies soluble in caustic 
soda, the coal-tar creosote oil made in London only containing 
5 to 10 per cent. Watson Smith found one sample of the pheno- 
loids obtained from blast-furnace tar to contain only 1'33 per cent, 
of phenol having a boiling-point of 182° C, while those obtained 
from Lancashire tar contained 65 per cent, of crystallizable carbolic 
acid (the phenol may have been previously separated from the 
former). The fraction that would contain cresol had 4-5 per cent, 
of phenoloids, and the fraction boiling from 210° to 230° C. con- 
sisted of a mixture of the xylenols and cresols. The " creosote 
oil" is treated with caustic soda, the insoluble hydrocarbon oils 
separated, and the soda compound decomposed by the waste gases 
from the furnace. Sodium carbonate is formed, setting free the 



AROMATIC DERIVATIVES 



235 



phenoloids. The carbonate of soda is treated with Ume, giving 
fresh caustic soda for another quantity of oil. The crude pheno- 
loids are distilled, yielding the " creosote " of commerce. It con- 
tains about 1 to 2 per cent, of phenol, a large quantity of cresols, 
and a smaller quantity of the higher homologues. The hydroxy- 
phenols, similar to those found in wood creosote, are present onlj' 
in very small quantities. 

Schulze has found in coal-tar cresols 40 per cent, meta-cresol, 
35 per cent, ortho-cresol, and 25 per cent, para-cresol. 

When fresh, creosote is almost as colourless as water, but it 
gradually darkens on keeping, slowly forming tarry products of less 
potency. In most forms it is a stronger antiseptic than crude 
carbolic acid, and has not such a caustic action on the skin. 

The Cresols. — o-, m-, /^-cresols are soluble in water to the extent 
of 2-2 to 2-5 per cent. The following table gives the physical 
projierties of these three compounds : 



Boiling- 
Point. 


Melting- 
Point. 


Specific 
Gravity. 


0-cresol (crystalline) 
29-cresol (crystalline) 
m-cresol (liquid) 


191° 

202° 
203° 


30° 
36° 

4° 


1-0053 

0-996 

1-05 



They are sold under various names (Jysol, tricresol, etc). Mixtures 
of the cresols are dissolved in fat subsequently saponified with the 
addition of alcohol. They form brown clear syrups miscible M'ith 
water to clear saponaceous fluids. With hard waters precipitation 
of lime and magnesia soaps occurs. Clear solutions are formed 
in glycerine or alcohol. Morgan and Cooper give the following 
carbolic acid values against Staph, pyog. aureus by the Martin 
and Chick method of testing : 



o-cresol 
7)-cresol 
m-cresol 



2-1 
2-4 
2-0 



The Higher Phenols. — The higher boiUng-point tar acids (phenols) 
are practically insoluble in water, and the chemical constitution 
of fractions of different boiling-points has not been definitely settled. 
Although higher phenols such as 79-cumenol are present, and can 
\\4th difficulty be isolated, yet partly h>drogenatcd i^henoloids are 
present in the complex which undoubtedly possess germicidal 
value. The chemical constitution of " tars " derived from various 
sources such as coke ovens, gas Morks, etc.. varies very decidedly 
in composition, the chief influence being the temperature of dis- 



236 DISINFECTION AND STERILIZATION 

tillation of the tar. At high temperatures " cracking "occurs, and 
it is probably during this process that partial hydrogenation of the 
benzene nuclei takes place, the hydrogen, of course, being derived 
from other rings which are converted into pitchy matter and carbon. 
Owing to their relative insolubility, emulsification has to bo 
resorted to in order to make use of their high germicidal powers. 
Various manufactured articles of this class are on the market under 
dififerent names, the preparation of a stable, fine emulsion (the finer 
the emulsion the greater the germicidal power) being the secret of 
success or failure provided that the tar acids used are sufficientl}' 
active. Emulsification can be brought about in many ways with 
fats or resin, alkali or soaps, and various oils — e.g. castor oil — with 
or without the addition of stabilizers such as saponins, gelatine, 
and isinglass. According to Fehrs,^ the emulsifying oil is not 
without influence on the germicidal power of the disinfectant, it 
being claimed that linseed oil is superior to rape oil in this respect. 
Sulphonation of the phenols and their derivatives yields soluble 
salts which are also germicidal; acetylization will also bring about 
the desired solubility. 

Homologous Phenols. — The introduction of aliphatic chains into 
the nucleus of phenols raises the germicidal activity. The superior 
germicidal activity of the cresols and the "higher boiling-point tar 
acid fractions " have been already referred to. The o- and 2:(-positions 
for the entering groups have a greater influence than rn-substitution. 

Long aliphatic chains introduced into the phenol nucleus do 
not, however, bring about a corresponding increase in germicidal 
activity. It is generally stated that the xylenols, of which the o- 
is stronger than the m-, are the most effective of the substituted 
phenols, but evidence is lacking as to the validity of the ordinary 
methods of comparative testing on account of the rapidh' decreasing 
water solubility of the higher homologues. 

When tested against staphylococci, the monosubstituted para- 
phenols can be arranged in the following order of increasing germi- 
cidal activity: amyl, isobutyl. isopropyl, propyl. 

There are several exceptions to the general rule on the jjosition 
of substitution as affecting the germicidal powers — viz., that the 
ortho compound will be stronger than the meta and the meta than 
the para. Thus, although the 1:2:4- normal-propyl cresols follow 
the rule, the iso])ropyl derivatives, when tested against sta])hy]o- 
cocci, exhibit the converse, the order being p-, m-, o-. In the iso- 
butyl cresols the order of activity is 'p-, o-, m-, whilst in the amyl 
derivatives the ortho is said to be weakest, the meta and para 
being equal in activity. 

^ C'cntr. Bull. Bukl., lUOii, 37, 730. 



AROMATIC DERIVATIVES 237 

Trlmethol, trimethyl-methoxy-phenol (2:4:5:1) has been stated 
to possess a carbolic acid coefficient of 40 (by the R.W. method) 
when properly emulsified. It is used in intestinal disinfection/ 

p-AUyl phenol has been introduced as an antiseptic under the 
name of chavosot ; tlivTiiol (^so-l^^opyl m-cresol) and similar deriva- 
tives are described under essential oils and ])erfumes. 

Oil of eucalyptus (cineole) combines equimolecularly with 
o-cresol, forming a crystalline body melting at 55-2° C. called cre- 
sineol; it has "high germicidal properties. "- 

The Aromatic Acids. 

The introduction of — COOH groups or — alkyl COOH gi'oups 
into the benzene ring yields acids of relatively low antiseptic power, 
but which increases with the molecular weight of the entering acid. 

The introduction of a — COOH group into the nucleus of a 
phenol likewise generally lowers its germicidal activity. Exceptions, 
however, are to be found in those cases where the acid thus formed 
is a relatively strong one, and an enhanced germicidal activity is 
observed which can be attributed to the hydrogen ion. Ortho 
substitution likeAvise occasionally results in the production of an 
acid stronger than the original phenol. 

Benzoic acid, CgHgCOOH. exists in gum benzoin, balsams of 
Peru and Tolu, and several aromatic gums that have been used for 
ages for embalming. It is soluble in about 400 parts of cold water, 
yielding an acid solution of pungent, disagreeable taste. It is 
strongly antiseptic both as solid, solution, and vapour, and even in 
its salts. 

Salkowski,^ in a number of exjjeriments with meat juice inocu- 
lated with putrid fluid, showed that benzoic acid, in a dose smaller 
than salicylic, prevented putrefaction. Buckholz* found that 
1 in 1,000 stopped the growth of micro-organisms. Haberkorn 
did not succeed with the bacteria of urine with less than 1 in 400. 
Jalan de la Croix, ^ in seventy-four experiments with varying quan- 
tities, showed that the least quantity that would prevent bacterial 
growth from being inoculated into a fresh liquid (beef-tea) was 
1 in 2,800. To kill bacteria he required 1 in 410, and to sterilize 
spores 1 in 50. As regards non-organized ferments (" enzjTnes "), 
Wernitz^ declares that pepsin is neutralized by 1 in 200, and others 
by 1 in 300, of benzoic acid or benzoate of soda. 

1 Eighth Int. Cong. App. Chem., 1912, 8, 150. 
- T. T. Cocking, Pharm. Conf., 1920. 

^ " Ueber die anti.se])t. Wirkimg d. Salieyisaurp iind Bcnzoesiiure," Berlin . Klin . 
Wochenschr., 1875, p. 22. * Arch. exp. Path., 1875, 4. 

5 Ibid., 1881, 13, 175. 6 Dorpat Essay, 1880. 



238 DISINFECTION AND STERILIZATION 

Martindale (Extra Pharmacopoeia) gives 0-2 per cent, benzoic 
and 0-1 per cent, salicylic acid as killing B. coli communis in two 
and a half minutes under laboratory conditions. 

Graham Brown^ stated that sodium benzoate was superior to 
quinine hydrochloride and sodium salicylate in destroying the virus 
of diphtheria ; he believed even that by saturating the human system 
with benzoic acid by repeated hypodermic injections it was ren- 
dered almost insusceptible of inoculation with diphtheria. 

In disorders of the bladder attended by ammoniacal urine, 
Gosselin and Robin- proved that benzoic acid taken internally 
rendered the urine acid, preventing the precipitation of insoluble 
phosphates and the formation of carbonate of ammonium and 
poisonous salts by the urinary bacteria, and also diminished the 
amount of urea excreted. Therefore, Ererichs introduced it success- 
fully for uraemia. They use 1 to 4 grammes per day dissolved in 
glycerine and water. 

Vallin states^ that " in most cases, to destroy definitely and 
without return germs transplanted from a sterilized liquid into 
the midst of an appropriate culture fluid, the proportion of benzoic 
acid should be 1 in 77, or even 1 in 50." This would make it rather 
more potent than phenol, cresol, or other similar compounds. It 
is not poisonous; Professor Senator, of Berlin, gave as much as 50 
grammes of sodium benzoate a day to a patient with acute rheu- 
matism without ill effect. As much as 1 ounce of ammonium 
benzoate per day can be taken without any noticeable effect, and 
is excreted as hippuric acid in the urine. Its carbolic acid 
coefficient is about 5-0 (Rideal, 1910). 

In those cases in which the odour and taste are immaterial, a 
saturated solution of benzoic acid in water delays the putrefaction 
of animal matters much more effectively than salicjdic acid. It 
has less effect on vegetable effusions. It is also useful for jjreventing 
fats from becoming rancid, as in " adeps benzoatus," benzoated 
lard of many pharmacopoeias. Added to milk, a very small quantity 
prevents coagulation.* In a series of experiments by one of the 
authors in 1899, in which molecular proportions — i.e., sodium 
benzoate 0-026, potassium benzoate 0-029, benzoic acid 0-022 per 
cent. — -were separately mixed with milk, it was found that all had a 
marked action in retarding the souring, that the free acid was the 
most energetic, but that the effect came to an end sooner than with 
inorganic salts such as fluorides, probably owing to the benzoic 
acid itself being decomposed by some of the organisms.^ Following 

1 Khh's Archiv, 8, p. 140. - Arch, gencrales de Med., 1874, 24, 5(5(5. 

^ Desinfectants, p. 202. 

* ('hem. News, 1880, 1, 130; Horn, Zeiii^ch. Chem. IndiisL, 1888, 2, 392. 

^ Richmond and Miller, Analyst. 1907. 32. 



AROMATIC DERIVATIVES 239 

a report of the Referee Board of the U.S. Board of Agriculture 
that doses of benzoates under 0-5 gramme per day were not 
injurious to health, and that even 4 grammes per day did not act 
as a poison, the U.S. Board in Pamphlet 104 of 1909 have 
announced that they will make no objection to the use of sodium 
benzoate in food provided it is plainly labelled on each package, 
both as to presence and quantity (see also p. 56). 

Benzoic acid and benzoates are ingredients in many antiseptic 
mixtures. Patented preservative mixtures containing benzoic 
acid are numerous. With regard to complex formulas it may 
generally be said that the additions are made for the purj^oses of 
solubility or disguise, or to institute a special preparation, and 
that they very rarely increase, and often seriously diminish, the 
activity of the central ingredient, which is preferably used only 
dissolved in water, as pure as possible, and in defined strength. 

Dr. Miller states that by using the following mixture he could 
completely sterilize the mouth and cavities in carious teeth: 
" Thymol, 4 grains; benzoic acid, 45 grains; tincture of eucalyptus 
3^ drachms; water 25 ounces."^ Benzoic gauze contains 4 per cent, 
of benzoic acid. 

By heating benzoic with boric, tartaric, or citric acid, double 
compound acids called benzo-boric, etc., are formed, which are, of 
course, antiseptic, and are mentioned in some of the older patents. 
Although the benzoic acid is thus rendered much more soluble, 
and its taste is in a great part disguised, it frequently crystallizes 
out, and hence these compounds are now seldom heard of. This 
separation also makes them irritant to wounds and mucous surfaces. 

Benzoic aldehyde, or benzaldehyde, CeHg.CHO, occurs with 
hydrocyanic acid in oil of bitter almonds. Angus Smith" considered 
it a little below phenol in antiseptic power. It readily oxidizes to 
benzoic acid, is sparingly soluble (1 in 30), and is of no hygienic 
use except in ointments, when the crude oil is very effective against 
eczema, irritation, and parasites, partly on account of the prussic 
acid it contains. Obviously the skin must not be broken It is 
official in the U.S. Pharmacopoeia. 

Sulphobenzoic acids, C6H4(HS03)(CO.OH), of which there are 
three isomers, made by the action of oil of vitriol on benzoic acid, 
are very soluble, and have an acid and bitter taste. They and 
their salts are antiseptic. The mixture of sodium salts is met with 
as an antiseptic under the name of sodium sulphobenzoate} The 
derivative saccharin, "gluside," or benzoyl sulphonimide, has also 

^ Chem. and Drug., 1887, 83. " Disinfectants, Edinburgh, 1809. 

^ J. Soc. Chem. fnd., 1888. 22G. 



240 DISINFFX'TION AND STERILIZATION 

a preservative power, and has been given internally to stop decom- 
position of urine in chronic cystitis.^ It has the constitution 

SO 
CgH4<^QQ2^NH. The commercial article, used for sweetening, 

is an impure sodium salt; 0-25 per r-ent. kills B. coli in two and a 

half minutes (Martindale). Von Heyden proposes as a substitute 

SO 
amidobenzosulphonimide CgHgfNHgXQQ^^NH, which, "with a 

sterilizing action equal to that of saccharin, is only half as sweet, 
without unpleasant after-taste. The sodium salt is not antiseptic."- 

Benzanilide is a weak antise2:)tic used as an antifebrile. 

Beuzosol. or benzoyl guaiacol, (C',.H-)CO.O(CgH4.0CH3), is a 
crystalline powder, colourless, almost free from taste and smell, 
insoluble in water, easily soluble in alcohol, and melts at 50° C. 
It is said to combine the effects of guaiacol and benzoic acid without 
any disadvantages, and to be very useful in tuberculosis, facilitating 
expectoration and rendering the sputum free from bacilli. Professor 
Sahli, however, remarks that the commercial article is of varying 
composition, that he found some specimens inert, and that " as 
the effect of guaiacol and creosote was due to local antiseptic 
action in the stomach, bcnzosol could not take their place." It is 
used largely in diabetes mellitus. 

Benzo-paracresol, CgH3(CgH-.CO)(CH3).OII, is an antiseptic 
prepared by the action of sodium benzoate on paracresol in presence 
of oxy chloride of phosphorus. It occurs as a crystalline powder 
almost insoluble in water, but soluble in alcohol (0-15 per cent.). 
It melts at 71° C.^ 

Benzoyl acetyl peroxiie, CgHgCO.O.OCOCHg, has been marketed 
under the name of acetyozone. as a powerful germicide. 

Benzo-naphthol, C\oH70.CO(CgH5), from /S-naphthol. melts at 
110 C\, and has also been proposed for internal antisepsis. 

Salicylic Acid. — There are three isomeric hj'droxybenzoic acids, 
CgH4(0H).C00H, of which only the ortho-compound, called sali- 
cylic acid, is of practical importance. It is soluble in about 500 
parts of cold and 15 parts of boiling Avater, in 7 of alcohol, 
3 of ether, and 50 of glycerine. When heated quickly it breaks 
up into phenol, which distils, and carbonic acid. The same decom- 
position occurs in the human system, as phenol appears in the urine. 
It is antiseptic and antipyretic. 

J. B. Duggan found that it was twice as powerful an antiseptic 

1 Lancet, 1888, i., llOo. 

2 Patent 12,743, 1895. 

3 Rev. Chim. Indudr., A])ril 1."), 1893. 



AROMATIC DERIVATIVES 241 

as the corresponding para-hydroxybenzoic acid, whilst the meta 
acid had intermediate properties.^ 

" Artificial " salicylic acid (from sodium phenate and carbonic 
acid) is somewhat more toxic in its action than the pm^e " natural " 
acid obtained from oil of wmtergi-een, due to the j)resence of ortho- 
and meta-cresotinic acids, CgH3(CH3)(OH).COOH, derived from the 
cresols obtained in the crude phenol from which the saHcylic acid 
had been prepared. It is not corrosive, does not coagulate albumin, 
and is not volatile at ordmary temperatures. 

When the saturated aqueous solution was tested with B. typho- 
sus, S. pyog. aureus and anthrax, Westcott found that in three hours 
only the former were killed. As a food preservative it is about 
equal to benzoic acid, their relative activities varying under different 
circumstances. Its physiological effect is more disttact than that 
of boric or formic acid or formaldehyde in the small quantities 
required, but there is no clear evidence that it causes injury to 
adults if the amount is Umited. The British Departmental Committee 
on Preservatives recommended restriction in that "it be not used 
ill a greater j)roportion than 1 grain per pint in liquid foods and 
1 grain per pound in solid food," or 0-0114 and 0-014 per cent, 
respectively, which practically would amount to a prohibition, 
since moulds and ferments are only rehabl}^ inhibited by 0-1 per 
cent., the amount commonly employed, though often exceeded. 
Addition of the acids to foods is forbidden in France, Austria, and 
some other countries. Traces are present in a large number of 
fruits.^ 

Among special sahcylic acid preparations the following may 
be noticed : 

Solution for Local Antisepsis.^ — Water, 1,000; boric acid, 12; 
salicyhc acid, 2. 

Antiseptic Tablets. — (1) For Thiersch's solution: 14 grains of 
resubhmed salicylic acid and 84 grains of pure boric acid, com- 
pressed into a tablet, are dissolved when required in 16 ounces of 
hot distilled water.* (2) Pastilles of sodium bicarbonate, biborate, 
benzoate, and sahcylate, with menthol, eucalyptol, and oil of 
wintergreen. One of the pastilles gives 2 ounces of a solution to 
be supplied as spray in nasal catarrh. " Strongly deodorant as 
well as antiseptic."'' 

Salicylated Gauze. — Gauze is washed with soda to remove grease, 
then in succession with water and acidulated ^\■ater, then bleached 
with chloride of Hme and weak acid, and finally well washed with 

1 Amer. Chem. J., 7, 62. - Analyst, 1903, 149. 

"* Carcano and Ccsares, Jiev. Chita. Indust., April 15, 1893. 
* Chan, and Dniy., 1891, 38. ^ Lancet, 1890, ii.; 1889, ii., 174. 

16 



242 DISINFECTION AND STERILIZATION 

water and dried. Next it is soaked in a solution of salicylic acid, 
5*6 parts; glycerine, 15; rectified spirit, 50; distilled water up to 
100 parts; drained, nearly dried by a current of sterilized warm 
air, and rolled or folded by machines previously made aseptic. 
The finished gauze is packed in cylinders freshly lined with melted 
paraffin sterilized by heat. The gauze is thus kej)t permanently 
slightly moist. ^ Contact with iron must be avoided, or purple 
stains result. 

The Salicylates. — -Owing to the powerful antiseptic and anti- 
pyretic properties of salicylic acid, a very great variety of deriva- 
tives, both organic and inorganic, of this acid have been prepared. 

Amongst the inorganic compounds are found the metallic salts, 
of which the sodium salt is most generally employed. 

Recently boro-disalicylic acid, BH0<Cr)p^xjYioOH' ^^^ been 
claimed as a strong bactericide.^ 

Amongst the organic derivatives those of the salol class are 
most frequent; these include oil of wintergreen and salol, phenyl 
salicylate, as the older and more well-known derivatives, and 
are largely employed as wound antiseptics. The esterification of 
the carboxyl group ensures the production of an ester of Ioav toxicity, 
which on hydrolj^sis will liberate the active acid and alcohol or phenol. 

Oil of wintergreen (GauUheria 2Jfocu7nbe7is) and oil of sweet 
birch [Betula lenta) consist almost entirely of methyl salicylate, 
CgH4(OH)COOCH3. It is a colourless fragrant liquid, sparingly 
soluble in water, but easily in alcohol, and also in alkalies. Specific 
gravity, 1-18; boiling-point, 222° C. 

Perier, of the hospital of St. Antoine, Paris, substituted the 
former oil for phenol in surgery, using a mixture which was perfectly 
miscible with water : Oil of wintergreen, 30 grammes ; tincture of 
quillaia, 6 grammes; water, 1 litre. Gosselin and Bergeron^ found 
that this oil, both as a solution and as a vapour, hindered the putre- 
faction of blood, and that its odour was inoffensive. It is still 
used in France as dressings, but is inferior to phenol and other 
agents in power. It does not coagulate albumin, and is comparatively 
non-poisonous, but it is found that the natural oil is somewhat 
irritant, whereas pure methyl salicylate is not so.* 

Salol, phenyl salicylate, CgH4(OH).COOC6H5, is insoluble in 
cold water, soluble in 15 parts of rectified spirit, in 3 of ether, 
and very soluble in chloroform and in oils. Antipyretic and anti- 

1 Seward Williams, Chcm. and Drug., May 27. 1893. 

2 D.R.P., 230, 725. 

^ Arch, general, de Med., 1881, p. lU. 
■* Lancet, 1898, i., 52. 



AROMATIC DERIVATIVES 243 

septic, rather stronger than methyl salic3date.i it passes through 
the stomach unchanged, to be decomposed in the duodenum into 
phenol and salicylic acid.- It is used in diarrhoea, dysentery, 
cholera, etc., as an internal antiseptic, also as an injection in gonor- 
rhoea and cystitis. It has been employed externally as a substitute 
for iodoform in skm and nasal diseases. LowenthaP has showii 
that salol will kill cholera bacilli in a paste containing pancreatic 
juice. Spirituous solutions (5 per cent.) are employed with various 
flavouring agents for mouth washes and dentifrices, toilet powders 
and soaps. When melted with camphor, salol. like many other 
substances, forms a permanent liquid which has also been used 
to replace iodoform.* 

Salophen, C6Hj(OH)(COO.C6H4.KH.CO.CH3), the salicylic ester 
of acetyl-jj-amidophenol, resembles the preceding in properties, 
but is said to have rather stronger antiseptic power. Melting-point, 
188 ' C. It has not been much used, and is expensive. 

Cresyl Salicylates. — -The three cresols form corresponding sali- 
cylates, and have been proposed as internal antiseptics. Betol, 
salinaphthol, or naphthosalol, is /3-naphthyl salicylate. Salbro- 
manilide is said to be a mixture of bromacetanilide and salicylani- 
lide. Salipyrin is a compound of antip;yTm and salicylic acid. 

Amongst other salol type compounds which have been prepared 
and had limited application from time to time may be mentioned 

salacetol, CgH4<CrY)( )( * H ( '( )( ' H S'%t'<>6-(/(, the monoglyccride and its 

.OH CH2CI 
derivatives, CgH4<^ | and protoaal — 

^COOCH— CH2CI 

/OH CHo V 

CgH / I " )CR,. 

\COOCH2— CHO^ 

Other aliphatic derivatives, including 

^6^4<.COOC3H5(OH).2 

OH 
spirosal, ^^i"^nr\Qn\j nxj qh ^^^^ glycol disalicylate, have 

recently been introduced.^ 

In benzoyl guaiacol ester, CgH4<^^,QQ;^ tt ; cmalutos, calcium 

acetyl salicylate; and vesipyrin,^ ^'e'^^'^COOC H ' "^' ^"'^^ attempts 

^ Practitioner, March, 1907. ^ jg^j^. Med. J., 1887, ii., 1438. 

'-^ Compt. rend., 107, IIGU. 4 Repertoire, 1889, p. 185. 

° D.R.P., 218,-tliG, and 227,999. ^ Thempie der Geijeivwarl, 19U0, 8, 92. 



244 DISINFECTION AND STERILIZATION 

to reduce the toxicity of the compound still further by the protec- 
tion of the phenol — OH group. 

In the aromatic derivatives -we find naphthol, resorcinol, and 
other homologous phenols substituted for phenol in the carboxyl 
group. 

Phenosalyl is a mixture of phenol, salicylic, benzoic, and lactic 
acids, made by heating them together at 140° C, adding 
menthol and eucalyptol, and, after cooling, adding four times the 
volume of glycerine. According to Sibut, it is composed of phenol 
80, salicjdic acid 10, lactic acid 20, menthol 1, melted together.^ 
It is a clear, syi'upy liquid, of sweetish taste, easily miscible ■uith 
water or alcohol, is not poisonous, and has a pleasant and non- 
persistent odour, which does not cling about the hands and clothes. 
The solutions have no corrosive action on the skin, the mucous 
surfaces remain smooth and slippery, and do not become dried up, 
as is the case after washing with carbolic acid or corrosive sublimate. 
Of course, this latter advantage belongs to the glycerine, and would 
equally pertain to phenol or mercuric chloride in the same medium. 

Professor Friinkel, - in a series of bacteriological trials, found that 
phenosalyl possessed an antiseptic power superior to phenol in 
dealing with the micro-organisms of cholera, anthrax, pneumonia, 
typhus, diphtheria, tuberculosis, Bacillus yyocyaneus, and Staphy- 
lococcus pyogenes aureus. It has been used by Duloroj^ in the ster- 
ilization of instruments, of gauze, and of different organic substances 
like blood, as well as decomposing urine and the saliva of consump- 
tives, with most encouraging results. It does not corrode nor 
discolour metals under ordinary circumstances of contact. 

A very large number of derivatives of salicylic acid have been 
introduced, and many of them patented, as antiseptics in medicine, 
as, for instance, F. Hoffmann's sodium ethylsalicylcarboxylate;^ 
Eichengriin's resaldol, an acetyl condensation product with 
resorcinol, said to be toxic to bacteria, not only in neutral but in 
alkaline menstrua (he also recommends the similar product from 
thymol). 

Phenoxyacetic acid, CgHgO.CHoCOOH, is stated to have a 
mild antiseptic action, due probably to hydrolysis with the liberation 
of phenol and acetic acid. 

Phenyl acetic acid, CgHg.CHoCOOH, is antiseptic, and was 
regarded very favourably by Klein as a strong disinfectant exceeding 
phenol in strength. A derivative of this acid, ^j-bromophenyl 
acetamide, has been introduced as a powerful antiseptic under 
the name of antiscpsiu. 

^ Year Booh Pharmaci/, 181(9, 234. - Baclcricu Kundc, Berlin, 1890. 

•^ ahem. Zcit., 1901, 36, 1045. 



AROMATIC DERTVATTVE8 245 

Anisic acid, or ;j-methoxybenzoic acid, CgH4(OCH.5)COOH, 
occurs in colourless prisms, melting at 175°, and distilling at 280° C. 
The sodium salt was recommended by Curci in 1887 as antiseptic 
and antipyretic in doses of 15 grains. It was said to be analogous 
in action to sodium salicylate, but without disturbing influence on 
digestion. 



,CH 



Cresotinic acid, CgHgC'-OH has been introduced as a germi- 
\COOH 
cide in the form of its water-soluble sodium salt and the phenyl 
ester solveol. Glyceryl tri-/j-cresotinate has been suggested as 
a ]iowerful germicide and antiseptic for internal use. 

Cinnamic acid, CgH^.CH : CH.COOH, melts at 133°. boils at 
290° ('. It is somewhat strongly antiseptic. Balsam of Peru 
contains cinnamic and benzoic acids. Piorkowski^ finds that 
proportions of the balsam up to 20 j)er cent, have only a slight 
retarding action on the growth of bacteria. A culture of B. pyo- 
cyaneus after contact with it for twenty-four hours still showed 
some growth when transferred to a nutritive medium. Cinnamein 
(benzyl-cinnamic ester, of which the balsam contains about 62 per 
cent.) does not destroy bacteria at a concentration of 1-5 per cent., 
nor does styracin at 4 per cent. Cinnamic acid at 2 per cent, 
prevents the growth of bacteria, and at 4 per cent, destroys them. 
Peru and storax balsams are parasiticide in skin diseases. 

French patent 371,091 preserves butter by enclosing it in a 
wrapper impregnated with cinnamic acid, which "prevents butyric 
fermentation." 

Hetocresol, cinnamyl-m-cresol, is weakly germicidal, but a power- 
ful antiseptic, and has been utilized for tubercular infections. 
The 0- and ;p-cresol esters are less active. The introduction of 
other alkyl groups into the esterifying phenol elevates the activity 
of the ester. 

Styracol, or cinnamyl-guaiacol, C6H5.CH:CH.COO.C6H4.0CH3, 
occurs in needle crystals ; is said to be a strong antiseptic in catarrh 
of the bladder and intestines, and in phthisis; soluble in alcohol. - 

Styrone, cinnamic alcohol, forms silky white crystals of a sweet 
taste, and having an odour like hyacinths. It is soluble in 12 parts 
of water, and easily in alcohol. The saturated aqueous solution 
has been recently used in America for the deodorization of foul 
ulcerated surfaces, and it does not cause irritation. As an antiseptic 
it is said to exceed thymol. This explains the healing properties 
long attributed to tincture of benzoin, of which liquid storax is a 
constituent. 

1 Che)n.\Zentr.,{l903, i.,'_414. - A. Haas, Sudd. Apoth. Zcit., 1895, 55. 



246 DTSINFECTTOX AND STERTLTZATTON 

/i- Phenyl-propionic acid, or hydiocinnamic acid, 

CeHj.CHa.CHo.COOH, 

is formed in the decay of albuminous matter, and. like other similar 
products, is a bactericide. 

Acetyl-o-coumaric acid, tylmarin, is another internal antiseptic, 
said to have a R.W. coefficient of 4-5. 

Gallic acid, trihydroxybenzoic acid, CgHo(OH)3,COOH, is 
astrigent and feebly antiseptic. 

Tannin, gallotannic acid, Q\^]^^Q0^,2Yic,0, is an amorphous 
powder, usually brownish, very soluble, and strongly astringent. 
It is well known to precipitate gelatine, and to form a compound 
with skins which is imputrescible (leather). It also coagulates 
albumin. Therefore it is, in some sense, antiseptic, but Gosselin 
and Bergeron,^ having added to 2 grammes of fresh blood 8 drops 
of a 10 per cent, aqueous solution of tannin, saw vibrios appear 
in the mixture on the fourth or fifth day — that is to sa}', almost as 
soon as they would without any antiseptic. Gubler and Bordier^ 
state that a horse which for many days had received doses of 20 
grammes of tannin remained with its blood unputrefied till the 
fifth day after death. 

None of the extracts of the many varieties of tannins from 
different plants have even the power to preserve their own solutions. 

8.C6H3(OH).COONa 
Sodium dithiosalicylate "No. 1," | is said 

8.C6H3(OH).COONa 
to be a jDowerful antiseptic. According to Hueppe. in a 15 per 
cent, solution the most resistant bacilli are easily destroyed in from 
twelve to fifteen minutes. In a severe case of ozaema it effected 
a complete cure in a relatively short time. In 2J per cent, solution, 
this preparation is reported to have yielded most strikingly bene- 
ficial results in the treatment of foot-and-mouth disease. 

Sulphonic Acids. 

According to Schneider^ the sulphonated phenols and cresols, 
especially the o- and m- substituted products, are stronger disinfec- 
tants than the corresponding phenols. Since the water solubility 
is increased by sulphonation, it would appear probable that the 
germicidal activit}^ of these compounds is due in part to the undis- 
sociated acid, but also to the hydrogen ions resulting from dissocia- 
tion, the acids being relatively strongly dissociated. It is thus 
to be expected that the sodium salts of the acids would be weaker 
germicides than the corresponding phenols. Schneider states that 

1 Arch. Med., 1881, IG. 2 j^,,;; Therapcul., 1873, 84, 2G5. 

3 Zeitsch. Hyg., 190G, 53, IIG. 



AROMATIC DERIVATIVES 247 

the sulphonic acid esters produced by the prolonged action of cold 
concentrated sulphuric acid on the phenol are even more powerful 
in germicidal activitj'. 

Cresol disinfectants are more germicidal in weakly acid than 
alkaline solutions, which is duo to the decreased water solubility 
caused by the salting-out effect and the decomposition of the 
soluble sodium phenolate. 

Aseptol, which originally consisted of p-hydroxy benzene 
sulphonic acid,^ has been employed both as an antiseptic and a 
germicide; the commercial article usually contains both the o-acid. 
the ethyl esters of both acids, and ethyl sulphate in addition. 

Esters. 

A few preparations have been introduced containing the phenyl 
esters of aliphatic acids, such as thymol palmitate and sodium 
cresylacetate, which, containing 25 per cent, of free cresols, is known 
under the name of cresin. CrzsosteriP is ?/i-cresol oxalic acid. 

Halogen and Nitro-Substituted Benzene Derivatives. 

The replacement of hydrogen by a halogen in the nucleus 
brings about a marked elevation in germicidal activity; unfortu- 
nately the toxicity of the phenol is raised by such replacement, 
although the introduction of but one halogen group causes 
a slight decrease. The toxicity can be compensated for by the 
simultaneous introduction of an aliphatic group in the nucleus. 
Accompanpng an increase in germicidal activity there is a decrease 
in solubility, and the substance acquires an unpleasant odour and 
irritating property. Substitution in the ^j-position is more effective 
than in the //i-, whilst ortho-substitution produces but little effect. 

p-Chloroplienol, CgH4(0H)Cl, is soluble in spirit, ether, and fixed 
oils, and practically insoluble in water. It has been used as an 
ointment (2 to 3 per cent, with vaseline) in the treatment of 
erysipelas and lupus. 

Trichlorophenol, CgHoClgfOH), has been used as a disinfectant, 
and claimed to be " twenty-five times stronger than carbolic 
acid " (Martindale). It occurs in white needles of unpleasant 
odour and pungent taste, volatile with steam. It is nearly 
insoluble in water, but dissolves in dilute alkalies, and is 
again liberated by carbonic or other acids. The calcium and 
magnesium salts have been used medically, and are not irritating. 

Laubenheiraer^ and Conrad* suggest the use of trichloro-w- cresol, 
lysocresol, as a powerful non-toxic hand disinfectant, and this sub- 
stance has been incorporated in a soap or sul])honated fat or fatty 

1 Obermullcr, Bcr., 18!)7, 40, .'502.'}. - DR. P.. 22f..231. 

3 Deutsch. Med. Wochensch., 1910, 4, lf)9. * Arch. Gynakol, 191(t, 91. 



248 DISINFFXTION AND STERILIZATION 

acid.^ ^;-Chloro-m-cresol, M'liich is stronger than 29-chloro-7)-oresol 
or 2?-chloro-o-cresol, when tested against staphylococci and chlori- 
nated xylonols, has also been the subject-matter of patents.^ Mixed 
chlorophenols prepared by the action of chlorine and hypochlorites 
on crude phenol incorporated with absorbents form the basis of 
some disinfectants. 

Tribromophenol, CgHaBrgfOH), is a white or brownish crystalline 
volatile substance, very insoluble in water, obtained by adding 
bromine water to phenol solution, when it falls as a white precipi- 
tate. It is interesting as a delicate test for phenol and as a way 
of separating it from cresol, since tribromocresol is liquid. Botli 
compounds have disagreeable odours, and are antiseptic, but too 
insoluble to be of much use. Xeroform is tribromophenol bismuth.^ 

The investigations of Bechhold and Ehrlich* have shoMTi that 
tribromophenol, bromol, is some twenty-five times and pentabromo- 
phenol some 500 times stronger as antiseptics than phenol, whilst 
tetrabromophenol is 250 times stronger, possessing, at the same 
time, only one-half of the toxicity. 

The germicidal activity of the halogen substituted phenols 
can, as has already been j^ointed out, be still further enhanced by 
alkyl nuclear substitution in addition to halogenation ; thus tri- 
bromo-m-xylenol is twenty times as powerful and antiseptic as tri- 
bromophenol, and tetrabromocresol exceeds the powerful tetra- 
chlorophenol some sixteen times in activity. Somewhat singularly 
the bromo-2?-cresol is weaker than the ortho- or meta- derivative 
when tested against staphylococci. 

The use of halogen hydroxy-aromatic acids — e.g., 6-chloro- 
3-hydroxy-2)-toluic acid — as disinfectants has been suggested by 
S. Priedel.s 

The effect of fluorine substitution on germicidal activity has 
not been investigated. 



however, is stated to be non-germicidal. 

Aromatic Iodine Derivatives. 
Nuclear substitution by iodine does not appear to produce any- 
marked increase in germicidal activity; the iodophenols are light, 
sensitive, and unstable. Traumatol, iodocresol, has been employed 

1 DR. P., 244,827, 1908. - D.R.P., 300.321; 302,013. 

3 Therap. Monatsh., 1899. 12, 64. * Hoppe Seyler, Zeitsch. Physiol. 

6 J. Soc. Chem. Ind., 1914, 807. Chem., 1906, 47, 182. 



AROMATIC DERIVATIVES 



240 



for surgical purposes. ^ Tri-iodocresol, or sorapure, appears, however, 
to be an active germicide.^ Losophan, trichloracetyl diphenyl 
dioxide, is a powerful antiseptic, but weak germicide. A feeble 
activity is likewise found to be present in yi-iodoanisol ; the 
methyl ester of di-iodosalicylic acid, or sanoform ; and sozoiodol, 

CeHoIg-^QXT • Pikrol, the potassium salt of di-iodoresorcin sul- 

phonate; loretin, SOgN/X/X 



OH N 



and nosophen, tetra-iodophenolphthalein, are weak antiseptics. 

lodocatechin and iodoterpin, CioHjoI, neosiode, represent other 
attempts to produce efficient germicides and antiseptics by nuclear 
substitution in the benzene ring. It cannot, however, be said that 
these results in the light of effectiveness of the bromo and chloro 
substituted products are in any way successful. Attempts to 
improve matters by the introduction of iodine oxygen compounds 
or substitution of nitrogen ring compounds for the benzene ring 
have been made, such as in ^-j. 



2)-iodoguaiacol, and aristol, dithymol di-iodide,'' 



CH, 



CH, 



and europhen,^ 



- 01 10 -^ 
C3H7 C3H7 



^6^2^ 



/C4H9 (iso) 
/CH, 



01 



^^6^3\QJJ 



C4H9 {iso) 



-OCH. 



and isoform, CQR^<Cjr) ^, among the former; and iodol, tetra-iodo- 

pyrrol,^pyrroldiazoI iodide, and N-a^y- tetra-iodoimidoazol amongst 
the latter. These appear to be antiseptic, and to have some slight 

1 Robin, Repertoire, 7, H. - Med. Press, 191G, 153, 377. 

•■» Noiszer, Ber. Klin. Wochenschr., 1890, 19. 

* Therap. Monatsh., 1891, 373, 379, 536. 

5 Pick, ViertdjahrschriJtJ. Derm. u. Syph., 1880, 583. 



250 DTRTNFECTTON AND STERILIZATION 

effect in treatment of tuberculosis and sypliilis, owing to the fact 
that the iodine is not so firmly attached to the nucleus. 

Aromatic nitro compounds, such as nitrobenzene, have often been 
proposed as disinfectants, but are iDrecluded by their odour, poison- 
ous action, and sparing solubility. Trinitrophenol is rapidly fatal 
in a saturated solution (about 1 per cent.) to bacteria and spores, 
but it causes yellow stains, is irritant, and very poisonous. Its 
R.W. coefficient is about 6. Cotton-wool soaked in the solution 
is used very successfully in the aseptic treatment of burns, hence 
it is recommended by H.M. Inspector of Explosives to keep handy 
for this purpose. Potassium dinitro-o-cresol, anfinonnin, 1 in 400, 
is destructive to all common injurious parasites, and does not injure 
plants. The nitro-naphthols, such as Martin's yelloAA', are described 
under the dyestuffs. 

Amido-Benzene Debivatives. 

The introduction of an — NH, group into the benzene ring pro- 
duces substances of low germicidal activity. The disinfectant 
strength can, however, be elevated in the usual way by nuclear 
alkyl substitution. 

Aniline, CgHg.NHo, has a carbolic acid coefficient of 0-57.^ 
Ewphorin, CgH5.NH.COO.CoH5, or phenyl urethane, has found 
application as a strong antiseptic. 

Nuclear substitution \\-ith a second — NH2 group loAvers the 
germicidal activity, contrary to Loew's hypothesis of active groups, 
as is noted by the following carbolic acid coefficients : 

>/i.-phenylenediamtne . . . . . . . . 0-2 

o-phenylenediamine . . . . . . . . 0-4 

2:)-phenylenediamine . . . . . . . . 0-3 

Alkyl or aryl nuclear substitution results in an elevation of the 
germicidal powers. Thus the carbolic acid coefficients of the 
toluidines are given by Morgan and Cooper- as follows : 

o-toluidine . . . . . . . . . . 1-00 

m-toluidine . . . . . . . . . . 1 -30 

2?-toluidine . . . . . . . . . . 1 -25 

Toluene-1 : 4-diamine has a coefficient of less than 0-2. The 
effect of aryl substitution is noted in ac.-tetrahydronaphthylamine, 
which has a coefficient as high as 5-3. 

The s])ecific action of the — NHg group as germicide and anti- 
septic in the benzene ring is doubtless also present, although masked 

^ Morgan and Cooper, Eighth Inter. Cong. App. Chcm., 1912. 
- Loc. cil. 



AROMATIC DERIVATIVES 251 

in thoRo aryl derivatives containing otlier groups, such as in 

o r* IT 

phenacetin and aminophenacetin, CgH4<lTvjVi^p/^^ pxr -vttt Avhich was 

shewn by Mosso^ to be a good antiseptic. The various p-amino- 
benzoic acid esters which have lately come into prominence as 
anaesthetics and the orthoforms of Einhorn and Heinz- are antiseptic 
as well as anaesthetic in action. 

As derivatives of these tyjDes may be mentioned : 

NH, NHo 



HO 



NH.COCHoNlCoHjj, 



HO 
COOC.Hg COOCH3 COOCH, 

Ancesthesin. Orthoform. Nervanin. 

The — NH2 group has like^vise been introduced into a great 
variety of other phenols and phenolic derivatives in order to in- 
crease the solubility of the substance in the form of a salt. 

The Organic CHLORAivnNES. 

Chloramine, NHoCl, was found by one of us to be an exceedingly 
strong disinfectant, but owing to its instability its utilization as 
a disinfectant, except when specially prepared, is somewhat limited. 
A search for more stable chloramine derivatives resulted in the 
discovery by Dakin,^ and by Dakin, Cohen and Dufresne* of a series 
of stable organic chloramines of great activity. Derivatives of the 

type T^/^NCl are all germicidal. 

Halazone, ^j-dichlorsulphonaminobenzoic acid,^ 

COOH 



^^0 
NCU 

a white powder soluble in dilute alkali and sodium carbonate solu- 
tions containing about 2G per cent, of available chlorine, has found 
extended application for field water sterilization. Tablets contain- 

1 Arch. Exp. Path, rharm., 32, 401. 

2 Miinchcn. Med. Wockensch.. 1897. 34, ICH. 

3 Brit. Med. ./.. 1915. i.. 318; 191(>. 87, 335. * Proc. Roy. Sac. 1916. 89B, 232. 
^ Dakin and Dunham, Brit. Med. J., May, 1917. 



252 DISINFECTION AND STERILIZATION 

ing halazone and borax or sodium carbonate sufficient to give a 
dilution of 1 in 300,000 effectively sterilize polluted water in half 
an hour. 

Of the more important chloramines which are now widely 
used for disinfectant pur])oscs maj' be mentioned chloramine-T , 
sodium toluene-p-suli^honchloramine, ^ dicJiIoramine-T. toluene-p- 
sulphondichloramine,- and chlorazine or tocklorin, the sodium 
salt of p-tolucne-monochlor-sulphamide. 

For medical purposes dichloramine-T dissolved in chlorinated 
eucalyptus {chlorcasane),^ or chlorinated paraffin wax, is finding 
extended applications. 

Dakin and his workers have showai that the introduction of a 
second NCI group into the nucleus docs not appreciably raise the 
germicidal power. Nuclear substitution by halogens, alkyl, or 
— NO., groups usually produces a slight lowering effect. Molecule 
for molecule the chloramines are stronger than sodium hjrpo- 
chlorite ; similarly the bromamines are more effective than sodium 
hypobromite. Naphthalene chloramines and sulphochloramines 
are stated to be similar to the benzene derivatives. 

Benzene sodium sulphochloramine is germicidal to staphylococci 
in concentrations of 1 : 500,000 with two hours' contact; the toluene 
derivative is about twice as strong. In the presence of serum 
the necessary concentrations are stated to be 1 : 1,500 for the 
benzene and 1 : 2,500 for the toluene derivative, this latter being 
only one-fifth of the molar concentration of sodium hypochlorite 
necessary to achieve the same results. 

B. pyocyaneus, B. typhosus, and B. coli are, however, somewhat 
more resistant than the staphylococci. 

The chloramines of the proteins have been investigated, but 
are relatively unstable, the simplest being chloramino-acetic acid, 
the sodium salt, CHo.NHCl.COoNa, of which is prepared by the 
interaction of sodium toluene-^-sulphochloramine, and glycerine. 
It is possible that the germicidal power of all the aromatic chlora- 
mines may be due to the intermediary formation of an aliphatic 
derivative of this type. 

Linked Benzene Derivatives. 

Nuclear substitution by a phenyl group, as we have seen, 
augments the germicidal activity to a very considerable degree, 
the nuclear substitution of the C4H4<^ group producing naphtha- 
lene, and its derivatives likewise result in the formation of useful 
germicides. 

1 Inglis, J. Soc. Chem. Ind., 1918, 37, 288. 

2 Chattaway, Chem. Soc. Trans., 1905, 87, 14."). 

3 Brit. Med. J., January, 1918. 



AROMATIC DERIVATIVES 

The direct linkage of two phenols — e.g., 



253 



or linkage through the groujiings — CHo — , — CHOH — , — CHOR^ — , 
where R is an alkyl group, increases the antiseptic power of the 
phenol, which can still further be enhanced by nuclear substitution 
in the usual way. Linkage through the grouj)ings • — CO — or 
— SO., — ■ results in the formation of relatively weak germicides, 
the activity of which, however, can be augmented by nuclear 
substitution. BechokU found that the halogen substituted bi- 
phenols were strong germicides when used against anthrax and 
staphylococci, but states that they were weaker than lysol. Bock- 
finds o-hydroxydiphenylcarboxylate, 



OH 



/ 



—^ VCOOH 



a good disinfectant. 

Amino- linkage through the — CO — grou]) by means of phosgene 
has resulted in the formation of many complex derivatives, the 
germicidal activities of which, however, have not been investigated. 
According to Bayer^ the compound, 



HO NH-CO-<_>-NH-CO-NH-<_>-CO-NH OH 





SO3H 



SO3H 



is both trypanocidal and spirillocidal. 



Naphthalene Derivatives. 

'3-Naphthol is official in the British (1898), Belgian, and German 
Pharmacopc«ias, the dose in the former being 3 to 10 grains in 
a cachet for internal antisepsis, especially in typhoid and iii 
cholera as a preventive. Its solubility in water is increased by 

^ Hoppo Seyler, Zeitsch. I'hysioL Chciii.., I'JUG, 46, 173. 

- Diss., Berlin, 1912. ^ D.R.P., 218,12-2. 



254 DISINFECTION AND STERILIZATION 

boric acid. Schneider observes that naphthols dissolved in alkaline 
carbonates have greater disinfectant powers than alkaline naphtho- 
lates; the former solutions contain naphthol in the free state. He 
states that staphylococci and tyi^hoid are killed in a short time 
by 0-5 to 1 per cent, of /i-naphthol alkahne carbonate solution.^ 

Ointments containing 10 to 15 per cent, are sufficient in scabies 
and psoriasis. It is also prescribed for typhoid and intestinal 
dyspepsia, and in summer diarrhcjea of children. Betol or ;3-naphthol 
salicylate is less soluble than naphthol, and is seldom used. A 
number of easily soluble beta-compounds have been introduced, 
such as /i-naphthol sulphonates, aspaprol or atrastol (the calcium 
salt), and aluminol (the aluminium salt). Helbing states that an 
aqueous solution of the latter I : 250 prevents all growth of gono- 
cocci, pus cocci, and allied bacteria. 

The sodium /i-naphtholate, microcidin, has found application 
as a germicide. Epicarin, or /!^-hydroxynaphthol-o-hydroxy-m- 
toluylic acid, and its salts have been introduced by Eichengriin- 
as soluble powerful disinfectants for dermatological purposes. 
Schering^ suggests the use of cerium hydroxide and phenol or 
/3-naphthol as germicides. 

a-Naphthol is stated to be three times as powerful an antiseptic 
as the /i- derivative; the salicylate appeared contemporaneously 
with hetol as alphol. 

The hydronaphthols, such as tetrahydronaphthol, or tetralin, 
are stated to be more powerful germicides than the naphthols,* 
and equivalent to the xylenols in germicidal activity. 

Halogen Substituted Naphthols. 

Bechhold^ finds the odourless and non-poisonous halogen sub- 
stitution naphthols more powerful than any disinfectant except 
mercuric chloride. These comjDounds appear to exert a markedly 
selective action on various organisms; thus tribromonaphthol, 
providoform, which has exceedingly little action on B. pyocyaneus, 
B. paratyphosus, or B. tuberculosis (dilutions of 1 : 1,000 being 
required), has a high germicidal value against diphtheria bacilli, 
streptococci and staphylococci, killing the latter in concentra- 
tions of 1 : 250,000. The dibromo-/S-naphthol, on the other hand, 
is selective for B. coli. Against B. paratyphosus it is stated 
that the introduction of one or two halogens, either chlorine or 
bromine, produces but little effect, the germicidal power actually 
sinking on further halogenation. Monochlornaphthol exerts but 
little selective action, its action being uniform for all organisms, 

1 Zeitsch. Ilyg., 1906, 52, 534. - Pharm. Zentr., 41, 87. 

3 D.R.P., 219,782. * D.R.P., 302,003. 

5 Zeitach. Anory. Chan., 1909, 22, 2033; Zcitdch. IJyy., 1919, 841. 



AROMATIC DERIVATIVES 255 

including tubercle. A dilution of 1 : 2,000 was found to be the 
antiseptic concentration for B. pyocyaneus ; for other organisms it 
was found weaker than the tribrom derivative. The introduction 
of a carboxyl group in the naphthol nucleus results in the formation 
of strongly antiseptic acids. The o-carboxylate is stated to be 
stronger than salicylic acid. 

Dihydroxynaphthalenes.— The 2:3- substituted compound has 
a relatively high germicidal activity. Morgan and Cooper state 
the carbolic acid coefficient to be 4-4. 

The 2 : 7- derivative has a coefficient of 2-8. 



Nitrogen Ring Compounds. 

Pyridine and quinoline contain nitrogen in the benzene ring. 
The former is volatile, mixes freely with water, and is strongly 
insecticide, but has a very unpleasant odour, which has militated 
against its use in horticulture. Tobacco smoke, indeed, ow'es its 
powers, not to nicotine, which is almost entirely decomposed by the 
heat, but to the products, pyridine and its homologues. Avhich are 
formed. Tessarini destroyed the bacilli of cholera and jDneumonia 
by tobacco smoke passed from ten to thirty minutes through a 
tube containing infected gelatine. Wynter Blyth killed the bacillus 
of nasal catarrh by 1 per cent, solution of pyridine and its homologues 
(from bone oil), or by tobacco smoke. There is proof that smokers 
and workers in tobacco enjoy comparative immunity from epi- 
demics, but pyridine inhalations {e.g., in whooping-cough and 
asthma) require care, as it is a cardiac depressant. The above 
experiments confirm the general view that disinfectant preparations 
containing the basic constituents of coal tar are to be jjreferred 
to those onh' including the phenols. 

Tobacco juice, of course, contains nicotine, and in France is 
sold as an insecticide under an official guarantee as to its nicotme 
strength. In England a solution of the pure base in water is some- 
times used as more definite. Richards' cakes for fumigation are 
nicotine and camphor; one of the ^Titers found a sample in 1909 
to contain 1-17 per cent, of nicotine, and to be completely volatile 
at a gentle heat. Solutions of nicotine containing from 0-01 per 
cent, and 0-5 per cent, are insecticidal. , 



Both quinoline, | { ( and isoqumoline, 



-N 



256 



DISINFECTION AND STERILIZATION 



are mildly antiseptic,^ the activity of which can be raised by the 
introduction of further aromatic groupings such as 



^6^6 



7 -phenyl quinoline, 



and chrysaniline, 



N 



CsH^NHs 

C 



N 



The introduction of the alkyl groups into the pyridine ring, 
as in the case of phenols, also increases the antisej)tic and germicidal 
powers ; thus dicarboxypicoline, 

COOH 



COOH 



LCH. 



N 



is stated to be a more powerful germicide than salicylic acid. 

Chinosol is potassium oxy quinoline sulphate, CgHgNO.SOjK, 
a yellow powder easily soluble in water to an acid yellow solution, 
which does not stain, has only a slight aromatic odour, is permanent 
on keeping, is non-poisonous, and does not coagulate albumin. 
It has been patented as a disinfectant, and more especially as an 
antiseptic. Klein compared its action on S. pyog. aureus, B. coli, 
and B. anthracis with that of carbolic acid, and reports that a 
solution of the latter of I in 20 strength is required to kill S. aureus 
or B. coli in five minutes with certainty, whereas chinosol does this 
in a strength of 1 in 150. Anthrax spores are not apj^reciably 
affected in forty-eight hours by 5 to 6 per cent, carbolic, whereas 
chinosol of 1 per cent, acts germicidally on them in five minutes. 
Bechhold^ found that it exceeded lysol in strength. In the WTiters' 
laboratory, B. coli was not sensibly affected after four hours in 
1 in 1,000 chinosol, while 1 in 2,000 of mercuric chloride produced 
sterility under the same conditions in fifteen minutes, so that it 
is difficult to explain the much higher powers that some observers 
have found for chinosol. Thresh and Sowden state that chinosol 
spray of not less than 1 per cent, is a reliable disinfectant.^ Houston 
did not succeed in killing B. coli in excreta by 1 in 75, and on linen 
by 1 in 62.^ On account of its acidity it acts on iron and steel. 

1 Donath, Ser., 1881, 14, 178, 17()9; Stockenam, J. Physiol, 15, 295. 

- J. San Inst., January, 1903. 

•^ Hoppo Seyler, Zeitsch. Physiol. Chem., 1900, 46, 173. 

* Practitioner, 1902, 331. 



AROMATIC DERIVATIVES 



257 



Organic Dyestuffs and theer Derivatives. 

We have already referred to the use of dyes in the staining of 
micro-organisms, to the development of the principle by Ehrlich 
in the preparation of s^'nthetic s])irillocidos. and have noted that 
water-soluble sulphonated dyes arc, as a rule, not so germicidal as 
the basic dyes, and those w liicli will exist in colloidal solution in 
water. Selective action of a particular type of dyestuff for a. 
certain organism is especiall\' evident, and much attention has 
been paid to this feature in the development of methods of selective 
staining, although the penetration of the coloured dye is not due 
in all cases to the chromophoric or auxochromic grouping, the 
former being frequently reduced by the micro-organism with the 
formation of leuco bases. 

One of the oldest dyestuffs emploj^ed as a germicide is 
methylene blue, 

S 



(CH3)2N- 



pN(CH3)Xl 



I 
N- 



which is specific in its action against malaria; the parasites, how- 
ever, are not coloured by the dye, and it is, contrary to the expecta- 
tions of Ehrlich, less effective than quinine. Lilian^ has found it 
remarkably effective against bilharzia. MichaUow^ has made the 
significant observation that living j^rotoplasm is not stained by 
methylene blue, but once the protoj^lasm begins to die, staining 
rapidly ensues. Tubercle bacilli absorb the dye, and their activity 
is impaired but not destro3'ed. Binger^ finds it to have a powerful 
inhibiting action on meningococci, being only slightly less active 
than mercuric chloride. 

The diphenyl- and triphenyl-methane dyes have long been used 
as antiseptics and disinfectants.* Malachite green and brilliant 
green (tetramethyl- and tetraethyl-diaminodiphen^dcarbinol), when 
injected into the blood, are effective agents against try^janosomes,'' 
killing them within forty-eight hours.'' Brilliant green will destroy 
pneumococci in a dilution of 1 : 30,000; phagocytes are not 
inhibited until a dilution of 1 : 2,000 is reached. A definite 

1 Lancet, May, 1902. - Petersburger Med. Wochenschr., 1899, 23. 

3 J. Infect. Dis., 1919, 25, 277. 

* Stilling, Lancet, 1871, 272. 

° Wendelsladt, Zeitsch. Ilyg., 190G, 52. 

« Brit. Med. J., 1904, ii., 1449, 1G48; Dent. Med. WocJi., 1900, 21, 4il,{. 

17 



258 DISINFECTION AND STERILIZATION 

bactericidal action of tliis dye can be noted in a dilution as great 
as 1 : 5,000,000/ although to destroy organisms such asB. subtilis 
or B. mycoides a dilution of 1 : 100,000 is required.^ 

Rosanilines. — Methyl violet and gentian violet, the methylated 
2)-rosanilines, are slightly more effective than rosaniline as germi- 
cides; thus gentian violet requires a dilution of 1 : 300,000 to kill 
B. mycoides, whilst the same result can only be obtained with a 
dilution of 1 : 200,000 of rosaniline.^ Jacobi* reports favourably 
on the use of these dyestuffs in sarcoma. 

Aniline blue (triphenylrosaniline) and toluidine blue are strong 
bactericides, and the former appears to have a slight selective 
action on malaria, as in the case of methylene blue. The parasites 
are not coloured with the dye.^ 

Pyoletannin and ethyl pyletotannin (auramine hydrochloride and 
its derivatives), 

NH 



(CH.3)2n/ /-<^\ ^N(CH3)2,HC1, 

were originally suggested by Stilling^ as antiseptics. The substitu- 
tion of the methyl by ethyl groups increases the antiseptic power, 
but they appear to be less effective than methylene blue, brilliant 
green, or methyl violet in germicidal activity. The fugitive colours 
dahlia blue and cyanin are stated to be extremely effective 
germicides. 

The introduction of the chromophoric — NO, grouping in 
phenols has, as we have already noted, a marked effect on the 
germicidal activity, but the toxicity is likewise raised. Martin's 
yellow (dinitro-a-naphthol) is germicidal, but naphthol yellow S 
(dinitro-a-naphthol sulphonic acid) is not, owing to the introduction 
of the — SO.3H group causing an increase in the water solubility. 

Diazo dyes are weakly germicidal, and the diazo grouping is 
not toxic. Chrysoidin, 

NH, 



CfiHgN = N^ ^— NHoHCl, 

exhibits the peculiar characteristic of agglutinating cholera and 
allied vibrios. 

1 Leitch, Brit. Med. J., 1919, i., 236. 

2 Crossley, J. Amer. Chem. Soc, 1918, 41, 2083. 

^ Crossley, loc. cit. * ./. Amer. Med. Assoc, 47. 

6 PhUadelphia Med. J., 1898, 13. 
^ Loc. cit. 



AROMATIC DERIVATIVES 



259 



Tetrazo colours derived from naphthalene disulphonic acid 
(3 : 6-) are strongly parasitotropic. Ehrlich showed that trypan 
red, 



SO.,Na- 



N = N-< :>— <:;>-N = N 



-SOgNa 



SOgNa- 



-SO^Na 



and its various derivatives were effective trypanocides.^ 

Trypansosan (a derivative of parafuchsin) is not only selective 
for trypanosomes, but is likewise effective against tubercle. - 

Flavine, or trypoflavlne (diamino -3:6- methyl - 2 - acridine 
chloride), prepared by Bendon, was shown by Browning and Gilmoor 
to have a marked action on trypanosomes; infections have been 
investigated in detail at the Middlesex Hospital. It kills B. coll 
and cocci at a dilution of 1 : 100,000, but only inhibits phagocytes 
at a concentration of 1 : 500, and therefore appears superior to 
brilliant green for internal use. It is approximately ten times 
as germicidal as mercuric chloride towards B. coli in serum. ^ It 
is three times as powerful as acridinium yellow. Safra7im, 
eurodin, and chrysamllne are stated to be extremely powerful 
trypanocides. 

A. Raal* asserts that strongly fluorescent bodies much increase 
the action of sunlight on organisms, whilst they are almost inert 
in the dark. A 1 in 20,000 solution of acridine killed infusoria 
exposed to sunshine in six minutes; in the dark they survived for 
twenty-four hours. Similar results were noted with quinine 
sulphate and with eosine. The inference is that the effect is caused 
by the fluorescent rays. Fluorescin has been patented as an anti- 
septic by Turpin, chiefly for toilet preparations. ° The bromo- 
fluorescins, particularly eosin, are found to have greater power 
He claims a large number of other phthalein compounds as 
disinfectants. 

The more complex azo ring compounds, such as aminoguanazol, 

HN C.NH HN C.NH 



and phenylguanazol, 



HN.C\/NH 
N.NH, 

be weak bactericides. 



are stated to 



\/NH 
N.CeH^ 



1 Ber. Klin. Wochenschr., 1907, 9-12. 

'- Roehl, Zeitsch. Ilyg. exp. Therap., 19(10, 1, 7(t. 

3 Brit. Med. J., 1917, i., 73. 

" Pharm. Zeit., 1900. 45, r)C.9. 

5 Cenir. Baht. Par., 1914, 73, 4i;}. 



260 DTSTNFECTTON AND .STERILIZATION 

Azoic acid, N.,H, is a strong antiseptic, and its organic deriva- 
tives, such as 




and 



-Na 



also possess antiseptic powers. 



Sulphur Ring Compounds. 

Cyclic tliio- compounds are feebly antiseptic, and generally 
antiparasitic in their action; thus thiophene has a marked anti- 
septic action, but the germicidal action is negligible. Nuclear 
substitution by iodine slightly increases the germicidal activity.^ 

Ichthyol and its derivatives which are powerful antiparasitics 
in their action have already been referred to. 

Quinine, Hydrocuprein, and Cuprein. 

Quinine has long been a recognized specific for malarial infections, 
and is chiefly utilized in its more soluble forms, such as ammoniated 
tincture of quinine, bromoquinine, euchinin — quinine carbonic eth}^ 
ester — or /i-naphthol and monosulphonate of quinine.^ 

Quinine has but little action on pneumococci, although quinine 
hydrochloride appears to be distinctly germicidal to these organisms.^ 
Quinine itself is antiseptic to anthrax in dilutions of 1 in 625, whilst 
a mild restraining action on B. 'paratypliosus is to be noted with 
concentrations of 1 in 19,000. 

The germicidal activity of quinine can, according to Schroeder,* 
be sensibly increased by halogenation of the vinyl group. 

The aliphatic derivatives of hydrocuprein, on the other hand, 
exert a marked selective action on pneumococci, as do other cinchona 
derivatives.^ The pneumococci germicidal power of ethyl hydro- 
cuprein (optochin) is extremely high, a dilution of 2 in 
3,000,000 being effective,^ and its activity is not lowered by the 
presence of blood-serum.'^ Although optochin has but a feeble 
germicidal action on streptococci and staphylococci, yet substitu- 
tion of the methyl group by longer aliphatic groups increases its 
activity until octjdhydrocupreine is reached, the activity then 
falling again. 

1 Spiegler, Thcrap. Mon., 1897, 67. - Weiner Med. Blatt., 1896, 47. 

3 Aufrecht, Berlin Klin. Wochensch., 1915. 52, 104. 

4 Arch. Exp. Path. Pharm., 1913. 72, 361. 

5 Cohen and Kolmer, J. Infect. Dis., 1917, 20, 273. 

^ Morgenroth and Halberstadter, Sitzungsber. Kon. Prevs. AJcad. Wiss., 1910, 
723; 1911, 30. 

"^ Wright, Lancet, December, 1912. 



AROMATIC DERIVATIVES 261 

When tested against staphylococci, ^^so-pl•opylhy(lroquinine is 
twice as powerful as optochin, *50-butyl eight times, iso-amyl, 
which is antiseptic to B. diphtherice in dilutions of 1 in 50,000 to 
1 in 100,000, and iso-hexyl some ten times to twelve times, and iso- 
heptyl some forty times ; the ^so-octylhydrocupreine being germicidal 
to staphylococci in concentrations at 1 : 80,000. With staphylo- 
cocci a slight decrease is noted in the decyl, with a subsequent 
increase in the dodecyl derivative.^ 

Salts of cuprein, CigHooN.jfOH).^, possess a similar germicidal 
activity to hydrocuprein.- 

Alkaline solutions interfere with its power; one of the \vriters 
showed that a soap contaming 5 per cent, chinosol was inferior to a 
0-5 per cent, mercuric iodide soap. F. G. Muller reports encouraging 
results, as with chinosol in leprosy.^ Cresochin^ is said to be a 
neutral sulphonate of quinoline and tricresol, which is recommended 
for washing instruments, as it does not darken the steel. 

The sulphocyanide of quinoline is stated to be a powerful 
antiseptic.^ 

DiquinoHne-o-hydroxyphenyl sulphonate, diaptherin, and hy- 
droxyquinaseptol have been introduced as non-poisonous water- 
soluble disinfectants. 

Emetme hydrochloride, which is much used in cases of dysentery, 
has powerful amoebicidal properties, but is a comparatively weak 
germicide; a 5 per cent, solution does not destroy 5. typhosus in 
fifteen minutes.^ 

Essential Oils and Camphors. 

Perfumes, composed chiefly of terpenes and their oxidized 
products, such as thj^mol, menthol, and eucalyptol, have a limited 
sanitary value. All of them are very sparingh' soluble in water, 
but impart to it a more or less antiseptic effect. Early estimates 
of their power have not been concordant, chiefly owing to their 
having been tried variously in aqueous or alcoholic solution, or 

.OH 
in emulsified form. A saturated solution of thymol. C^Ha^^CHg 

in water (0-3 per cent.) arrests fermentation and jDutrefaction (the 
0-, m-, p- derivatives are stated to be equally germicidal, but in 
toxicity the ortho- exceeds the meta- and para-). Peppermint (con- 
taining menthol and menthene) has had a high reputation, and a 

* Morgenroth, Biochem. Zeit., 1917, 79, 257. 

- Brunn and Schaeffer, Berlin Klin. Wochenschr., 1917, 54, 885. 

3 Pharm. Centr.. 37, 247. * Zeitsch. oest. Apoth. Vcr., 35, 858. 

^ J. pr. Chcm.. |ii.]. 54, 340; [ii.j, 66, 209. 

6 J. Kolnier, J. Injrct. Din., March, 1915. 



262 DISINFECTION ANT) STERILIZATION 

number of recipes for " plague-water " have it as a basis. The 
use of hops in brewing partly rests on the power of the essential 
oil to check fermentation. "Terbene," made from turpentine by 
the action of sulphuric acid, was once reputed as a disinfectant, but 
now hardly figures except in terbene soap. Among other artificial 
products from turpentine are terpin hydrate (said by Colpi to arrest 
the growth of tubercle bacilli in 0-25 per cent, strength) and ter- 
pineol (stated to kill anthrax in 1 per cent, and staphylococci in 
10 per cent, solutions in sixty minutes at ordinary temperatures].^ 
Camphor is much spoken of as a personal prophylactic, but there 
cannot be sufficient of the vapour to disinfect the air. Above 
45° C, however, its antisej)tic action is quite marked. It is an 
ingredient in many remedies for cholera and diarrhoea, and in 
several " block disinfectants," such as sanocent, caniphortar, etc. 
Eucalyptus globulus and other species, which have long been famous 
as antimalarial, are largely planted on the Continent in marshy 
districts. The essential oil is decidedly germicidal, and has been 
given with some success in typhoid, and also against tapeworm 
and threadworm. 

Greig Smith- has investigated the germicidal powers of eucalyj)- 
tus oils in great detail. It was found that the average coefficient 
of E. australiana, the cheai^est oil, was 5-^, and of E. conerifolia 
4-8, the values of which would be augmented by the addition of 
acid to the aqueous emulsion. The coefficient was found to va,ry 
with the time; thus no action was noticeable until a contact period 
of 1-5 minutes had elapsed, the 20° C. carbolic acid coefficient was 
3-1 with fifteen minutes, 3-4 with thirty minutes, and 2-8 with four 
hours' contact. Of the constituents of cineole, aromadendral was 
most active, having a coefficient of 21-1, piperitone a coefficient of 
4-1, and the residual pinene and sesquiterpene the usual values of 
0-8 and 0-5 respectively. 

It is interesting to note that Greig Smith found that the germi- 
cidal activity was proportional to the amount of iodine liberated 
from potassium iodide (see below). 

Pinol is a liquid of similar character from Pinus pnnilis. H. 
Marx^ has investigated the action of various perfumes on anthrax 
and S. pyog. aureus. Kobert* finds that the terpenes by themselves 
have in general only a weak antiseptic action. The proportions 
needed for sterilizing exceed the solubility in water, and can only 
be n^ached by a spirituous solution or an emulsion. 

But it has been recognized since Schonbein pointed out the fact 

^ H. Marks, v. infra; also Ger. pat. 207,570 of 190(). 

2 Proc. Linn. Soc. N.S. Wales. I'JIT, 47, 321. 

3 C'eiitr. BakL, 1<JU3, [i-J. 33, 7-i. ^ Chcm. Zudr., VMl, i., ilO. 



AROMATIC DERIVATIVES 



263 



about 1840 that essential oils have a disinfectant power conferred 
on them by their slow oxidation in the presence of air and moisture, 
whereby ozone or hydrogen peroxide is produced; that as long as 
air and oil are present, the ozone or hydrogen peroxide is continually 
regenerated and absorbed, forming oxidizing and antiseptic products 
which dissolve in the water along with peroxide of hydrogen. 
This is the principle of Kingzett's sanitas. In his first j^atent 
(274 of 1876), 9 parts of turpentine oil and 1 ounce of water kept 
constantly at 60° F. were treated with a current of warm air or 
oxygen for seven to ten days, when the aqueous liquid, "Sanitas 
Fluid," contains HoOo- Both these average an equality with a 
10 per cent, solution of hydrogen peroxide/ They are recom- 
mended as non-poisonous and non-corrosive oxidizers and anti- 
septics, suitable for household disinfection and for surgical opera- 
tions. The antiseptic concentrations of various essential oils are 
cited by Heinz^ as follows: 



Oil. 
Menthol 

Camphor 
Turpentine 



Organism. 

[B. diphtherise 
- Staphylococcus 
[B. tyj^hosus . . 
( Staphylococcus 
\B. cliphtheriae 
Staphylococcus 



Antiseptic Dilution. 

.. 1 : 16,000 

. . 1 : 6,000 

. . 1 : 8.000 

. . 1 : 600 

. . 1 : 30.000 

. . 1 : 15,000 



BIBLIOGRAPHY. 

Dyes. 

Flavine, Lancet, 1917, i., 159. 

Fleming, A. : The Physiological and Antiseptic Action of Flavine, with Some 
Observations on the Testing of Antiseptics, Lancet, 1917, ii., 341-345. 
Flavine, Lancet, 1917, ii., 342. 

Browning, C. H. : The Germicidal Power of Flavine, Lancet, 1917, ii., G21. 

The Antiseptic Power of Flavine (Acriflavine), Lancet, 1917, i., 888. 

The Antiseptic Power of Flavine, J. Amer. Med. Assoc, 1917. 69, 54. 

Browning, C. H.: The Antiseptic " Flavine " (Acriflavine), Lancet, 1917, i., 927. 

Browning, C. H., Gulbrausen, R., and Thornton, L. H. D. : The Antiseptic 
Pi'operties of Acriflavine and Proflavine and Brilliant Green, with Special 
Reference to their Suitability for Wound Therapy, Brit. Med. J., 1917, ii., 
70, 75. 

Browning, C. H.: The Germicidal Power of Flavine (Acriflavine), Lancet, 1917, i., 
927; ii., 021. 

Dakin, H. D., and Dunham, E. K.: The Relative Gei-micidal Kflicicncy of Anti- 
septics of the Chlorine Group and Acriflavine and Other Dyes, Brit. Med. J., 
1917, ii., ()4(»-()45. 



1 Lancet, 1890, i., 809. 



^ " Handbuch der Pathologic." 



264 DISINFECTION AND STERILIZATION 

Hewlett, K T.: The ({crmicidal I'owor of Flaviue, Lancet, 1917, ii.. 727. 

Webb, C. H. S. : A Note on the Value of Brilliant Green as an Antiseptio, Bril. Med . 

J., 1917, 1, 870. 
Baibd, a. p.: Chlorazono, Calif. Eclect. Med. J., 1917, 38, 264-260. 
Cole, A. F. : Brilliant Green as an Antiseptic, Brit. Med. J., 1918, ii., 105. 
The Antiseptic Flavine (Acriflavino). Dental Ihxj.. 1918. 72, 37-39. 
Kratjss, R. B. : The Preparation of Dichloramine-T and Chlorinated Eucalyptol- 

1, 2, J. Amer. Pharm. Assoc, 1918, 7, 46-49. 
Flavine, Lancet, 1918, i., 370. 
Flavine, Lancet, 1919, ii., 838, 1113. 
Bbonvning and Gulbbausen: Testing of Antiseptics in Relation to their Use in 

Wound Treatment. J. Hyg., April, 1919. 
Hewlett, R. T.: The Germicidal Power of Flavine, Lancet, 1919, ii., 727. 
Hawk, P. B., Da Costa, J. C, Smith, C. A., and Rehfuss, M. E.: Chemical and 

Clinical Study of Chlorlyptus, a New Chlorinated Antiseptic, Thcrap. Gaz., 

March, 1920, 44, 156. 



Miscellaneous Chemicals. 

MotJCHET, A., and Malbec: Le " Quiniodol " nouvelle poudre codee, Paris Med., 

1913-14, 15, 307. 
RuEDiGEB, E. H.: The Germicidal Power of Glycerine on Various Micro-Organisms 

under Various Conditions, Philippine J. Sc, Manila. 1914, 9B, 465-477. 
Mabciiesint, R.: L'hexal (Solfo.salicilato diesameliltetramina) come antibatterico, 

antisettico, antiputrido, Gazz. vied, di Roma, 1914. 40, 537-540. 
T, W. E.: An Investigation of the Germicidal Action of Picric Acid, Gvi/s Hospital 

Gaz., 1914, 28, 459. 
Gabdneb, L. U.: a Study of the Efficiency of the Sielig-Gould Method of Testing 

Antiseptic Solutions, Surg. Gynec. and Obst., 1914, 19, 772-778. 
Wilson, A. : The Value of Salicylic Acid in the Treatment of Wounds and Typhoid, 

Brit. Med. J., 1915, i., 331. 
RuHBAN, I.: The Use of Dahlia in Infections, A^ner. J. Med. Sc, 1915. 149, 661- 

663. 
Webeb, E.: Phobrol als desinfektionsmittel, Klin-thtrap. tochn.-schr., 1915, 22, 

187-190. 
Yemano, H. W. : Antiseptic Iodine Solution, Mil. Surgeon, 1915. 36, 522. 
Siegall, G. : Ueber Noviform, Deutsche Med. Wochen.schr., 1915, 41, 770. 
Tbebing, J.: Ueber Hyperol, Wein. Med. Wochenschr., 1915, 65, 737-74(t. 
Livingston, I., and Cock, F. W.: Ether as a Disinfectant, Brit. Med. J., 1915, 

1., 331. 
Cappell. W. L. : An Iodine Fumigator: Some of its Uses, N.Y. Med. J., etc., 

1915, 101, 566. 
Babbitt. A.: The Antiseptic and Germicidal Value of Ether, Brit. Dent. J., 1915, 

36, 220-230. 
Smith. H. Z.: The Value of Tincture of Iodine as a Bactericide, Lancet. 1915, i., 

345. 
Symmebs, W. St. C, and Kirk. T. S.: Urea as a Bactericide, and its Application 

to the Treatment of Wounds, Lancet, 1915, ii., 1327-1329. 
Lambebt, R. a. : The Comparative Resistance of Bacteria and Human Tissue Cells 

to Certain Common Anti.septics, J. Exp. Med. Bait., 1916, 24, 683-688; J. Amer. 

Med. Assoc, 1!»16. 67, 1300. 



AROMATIC DERIVATIVES 265 

Inman, a. C: On the Bactericidal Effect exerted in vitro by Ethyl -Hydrocuprein 
(Optochin) Hydrochloride on a Faecal Streptococcus obtained from Wounds, 
J. Roy. Army Med. Corps, 1916, 27, 500-503; Lancet, 1915, ii., 1398. 

BiANCHERi, A.: Sul potere disinfettante dell' aceto, Ann. dig., 1916, 26, 521-528. 

Guthrie, D. : Note on the Value of Hexamine in Aural Suppuration and in Menin- 
gitis, Brit. Med. J., 1916, ii., 455. 

Rey-Pailhade, de: Sur Taction antiseptique de I'hyposulfite de sodium. Roles 
du soufre et de hydrogene philothionique, Bull. gen. de therap., etc., 1915-16, 
168, 886-888. 

WiLBERT. M. I.: Some Fallacies regarding Phenol: a Review, with Reports of 
Observations on the Influence of Ethyl Alcohol on the Germicide and on the 
Toxic Properties of Phenol, Pub. Health Hep., 1916, 31, 1046-1054. 

Jacobs. W. A. : The Bactericidal Properties of Quaternary Salts of Hexamethylene- 
tetramine, J. Exp. Med., 1916, 23, 563-568. 

Erulkar, a. S.: Hexamine: its Use and Misuse, Practitioner, 1916, 96, 405-408. 

Wallase, T. a.: Trichloracetyldiphenyldiiodide, Long Island Med. J., 1916, 1, 
147-154. 

Atonelli, G. : Su di talura atti activita specifica del dissinfettante taurina, Biv. 
d'ig. e san. pubb., 1916, 27, 32-41. 

Smith, J. L., Ritchie, I., and Rettie, T.: On a Convenient Method of Preparing 
Eusol, Brit. Med. J., 1917, ii., 386. 

Nolan, H. D.: Antiseptics and Germicides: a Review of Some Recent Work, 
Interstate Med. J., 1917, 24, 809-816. 

Sampiato, G.: Sur potere disinfettante del periodolo, Ann. d'ig., 1917, 27, 236-246. 

Howell, E. V., and Keyser, E. V.: Hexamethylenamine, J. Ainer. Pharm. Assoc, 
1917, 6, 445-451. 

Leuerman, M. D.: Clinical Observations of a New Iodine Preparation (lodosan), 
Ajui. Otol. Rhinol. and Laryngol., 1917, 26, 574-576. 

GoRE-GiLLON, G., and Hewlett, R. T.: Acetozone as a General Surgical Anti- 
septic, Brit. Med. J., 1917, ii., 209. 

McIndov, N. E., and Sievers, A. F.: Quassia Extract as a Contact Insecticide, 
J. Agric. Research, 1917, 10, 479-531. 

Seymour, L. W.: The Treatment of Dysentery, Wounds, etc., by a Combination of 
Internal Antiseptics, Brit. Med. J .. 1917, ii-, 115. 

Moore. W.: Volatility of Organic Compounds as an Index of the Toxicity of their 
Vapours to Insects, J. Agric. Research, 1917, 10, 365-371. 

Inone, Z., and Hanaoka, K.: Clinical Experiences of Cyano-Cuprol, Sei-i-Kivai 
Med. J., 1917, 36, 17. 

Takaki, T. : The Disinfective Power of Iodine, ibid., 16. 

Macfie, J. W. S. : The Limitations of Kerosene as a Larvicide. with Some Observa- 
tions on the Cutaneous Respiration of Mosquito Larva?, Bull. Entomol. Research, 
1916-17, 7, 277-295. 

Magee, H. E.: a Comparison of Some Antiseptics in Respect to their Diffusibility, 
Action on Leucocytes, and Action on Ferment Activity, Edivhurgh Med. ,1 ., 
1917, U.S.. 18, S6-95. 

Cabanes, A.: L'antisepsie ])ar le chldvoforme. Com pi. rend , 1917. 165, 1119. 

Colin, H.: Sur les proj)riete8 antiscptiqucs de I'air nitreux, Compt. rend., 1917, 
165, 194-196. 

.TuNKiN, H. D.: Liquid Petrolatum as ati Anti.septic. Illinois Med. J., Chicago, 
1917, 32, 416. 

O'Connor, V., and Kreutzman, H. A.: The Use of Bismuth Iodoform Paste in 
Outpatient Work, J. Amer. Med. As.soc, Chicago, 1917, 79, 2010. 

Mevin, Mary, and Mann, B: Pro])aration of a Preservative from Cresol, J. Anier. 
Ckcni. Soc, 1917. 39, 2752-2756. 



266 DISINFECTION AND STERILIZATION 

Bond, C.J. : On the Hsemaglutiiiiii Reaction as a Test for the Toxicity of Various 

Antiseptic Reagents, and on the Association (if any) between the Hsemaglu- 

tinin Content of the Blood Serum and Pus and Capacity to Resist Infection, 

Brit. Med. J., 1917, ii., 751-755. 
Rettie, T.: Antiseptics: a Short Account of Work done for the Medical Research 

Committee in the Pathological Department, Edinburgh University, J. Soc. 

Chem Ind., 1918, 37, 23-26. 
Stimson, a. M., and Neill, M. H.: A New Disinfectant Testing Machine, Pub. 

Health Rep.. 1918, 33, 529-539. 
Holland, E. B.: Calcium Arsenite and Arsenate as Insecticides, J. Econom. 

Entom., 1918, 11, 354-357. 
Irving, G. : Sublimed Sulphur in Mercurialism, Brit. Med. J., January 31, 1920, 

i., 149. 
Cassegrain, 0. C. : Picric Acid, a Preoperative Disinfectant, Neiv Orleans Med. 

and Surg. Ind., January, 1920, 72, 398. 



CHAPTER XIII 
THE CHEMICALS EMPLOYED IN DISINFECTION— Con^mwecZ 

THE ORGANO-METALLIC DERIVATIVES. 

A GREAT number of organo-inetallic derivatives have recently 
been introduced for disinfectant purposes. They are chiefly 
intended for internal use, and are consequently prepared to exhibit 
the minimum of toxicity to the human organism. Some arc 
germicidal })er se, but the great majority of substances of this class 
owe their property to the fact that by hydrolysis in the system 
the active constituent is liberated at a rate sufficiently slow to 
avoid the accumulation of a lethal or toxic dose in the human 
organism, biitat the same time to ensure a germicidal concentration 
being j)resent. Attempts have also been made to prepare sub- 
stances which shall be selectively adsorbed by the micro-organism, 
and thus ensure a local lethal concentration. 

Of the organo-metallic compounds, those of arsenic and mercury 
are by far the most important, but recent research has drawn 
attention to the desirability of investigating the germicidal 
activity of the ever-growing number of other organic-inorganic 
derivatives. 

Arsenic. 

The organo-metallic derivatives of this element have achieved 
an especial prominence owing to the researches of Ehrlich, cul- 
minating in the successful synthesis of the trypanocide salvarsan. 
Ehrlich, following Loew, assumed that in the protojDiasm of the 
parasite there existed certain groupings which reacted with the 
others in the disinfectant, the chemoceptors of the organism com- 
bining with the parasitotropic groupings of the disinfectant; these 
are very specific in their reactivity, since certain strains of trypano- 
somes which react A\ith orthoquinone colours and with arsenic 
derivatives, do not react with paraquinones, whilst strains Avhich do 
react with paraquinones and not with orthoquinoncs have also 
been isolated; these, however, react normally with arsenicals. 
The conclusion must be inferred from these experiments that 
there may be several such chemoceptors in an organism icquiring 
the corresjionding parasitotropic grou])ing in the disinfectant. 

2li7 



268 DISINFECTION AND STERILIZATION 

Levaditti and Lenz^ consider tlie chenioccptors to be albuminoid 
in character. As has been previously noted, unsaturated com- 
pounds are usually more germicidal than saturated ones, and 
trivalent arsenic is found to be a strong germicide, pentavalent 
arsenic being relatively Mcak ; thus Joachimoglu" showed that 
for isolated organisms, arsenious acid, As(0H)3, was some three 
hundred times more germicidal than arsenic acid, AsO(OH)3, whilst 
trypanosomes were destroyed by the respective concentrations 
1 : 20,000 and 1 : 100. These conclusions have been confirmed by 
Fiihner on the destruction of infusoria,^ and by Friedberger and 
Joachimoglu's experiments on the relative antiseptic powers of the 
arsenites and arsenates for yeast cells* (see ante). 

Of the early organo-arsenicals, derivatives of cacodyl were first 
employed, but their great toxicity limited their application. 

Arsenic Derivatives. — Of the pentavalent aliphatic arsenic 
derivatives possessing distinct germicidal or spirillocidal powers, 
resulting in all probability from a slow hydrolysis and reduction 
of the pentavalent to the trivalent arsenic may be mentioned : 

/ONa /ONH4 

Arrhenal,' =As~CH3 and solarson, O =As^CH: CC1(C.H4)4CH3. 
^ONa \0H 

Pentavalent arsenic derivatives containing an aromatic nucleus 
are much more common; these may be divided into the two divi- 
sions in which the aromatic nucleus is linked to the arsenic directly, 
and those where linkage occurs through oxygen. Of these latter 
may be mentioned such substances as guaiacol cacodylate, 

CH3/^\0— CeH^OCHg 

and cacodyl cinnaraic acid employed by Astruc and Marco" in 
cases of tuberculosis. 

Among the former and more important derivatives we find the 
various derivatives of benzene arsonic acid, 

such as arsanilic acid (sodium arsanilate is known under the name 
of soamin) and ;?^-hydroxy phenyl arsonic acid, their salts and 
esters. The p-hydroxy- compound is, however, less spirillocidal 

^ Zeitsch. Immunitats Forschung, 2, 545. 2 Biochem. Zeit., 1915, 70, 144. 

3 Arch. Exp. Path. Pharm., 1917, 87, 44. * Biochem. Zeit., 1917, 79, 13(5. 
6 Gautier, Presse Medical, 1902, 791, 824. « J. Phurm. Chim.., 12, 533. 



ORGANO-METALLIC DERIVATIVES 260 

than the p-aramo- derivative, being some two and a half times 
less potent, the introduction of one — NH, grouping into the 
nucleus lowering the toxicity, but increasing the parasiticidal 
powers. 

In this group is included aloxyl,^ 

H0\ / V 



0=^As— < >NHo 

NaO/ ^ ^ 

and its many derivatives. Atoxyl has achieved a marked success 
in trypanosome infections, but is much inferior in germicidal 
activity to the trivalent arsenious derivatives such as salvarsan. 
Amongst the more important derivatives of atoxyl may be men- 
tioned the acetyl, phenoxyacetyl, and phthalyl derivatives, which 
are as active or more trypanocidal than atoxyl, and much less toxic. ^ 
The proprietary articles Hiktin and Hektargyr have the following 
constitutions •} 

y \ /ONa 

SO.HNH^ )— As=0 



/ \0H 

Hiktin. 

< >— S0.>— NH— < >— As4o 

\ / - \ / \0H 

Hektargyr. 

These appear, however, to be relatively weak trypanosomicides. 

Kharsin, or o-toluidinarsonic acid, is a strong trypanosomicide.* 

By reduction of benzene arsonic acid, derivatives of the ty]}& 



-As=0 can be obtained. These trivalent arsenious 



compounds are much stronger than the derivatives of the penta- 
valent acid ; thus the p-axamo- derivative is some seventy-five times 
stronger than arsanilic acid,® destroying trj^panosomes in vitreo in 
a dilution of 1 in 3,000.000. A restraining action can easily be 
observed in dilutions as great as 1 in 24.000,000. 

The p-hydroxy- derivative is some 173 times as germicidal as 
p-hydroxyphenyl arsonic acid. 

1 Ehrlich and Bertheim. Ber., 1907. 40, 3292. 

2 Neiszer, Deut. Med. Wochenschr., 34, 1500. 

3 Biochem. Zeit., 191G, 78, 191. 

* For more complex derivatives of arsenic acid and their trypanocidal activity 
see Plimmer and Thomson, Proc. Roy. Soc, 1907, 79B, 50; and Morgan, Chem. Soc. 
Trans., 1908, 93,'2144. 

s Ehrlich, £ef., 1911, 44,[^1207. 



270 DISINFECTION AND STERILIZATION 

Arsenious Derivatives. — A few substituted arsenious acids have 
been investigated, notably by Joachimoglu/ such as arseno-phenyl- 
acetic, -glycolHc and -propiolic acids, and elarson, a strontium salt of 
chlorarsenobehenolic acid. Data as to their germicidal activities 
appear to be lacking. More important are the derivatives of 
arsenobenzene, 

/ Vas 



> — As 



to which class belongs salvarsan, 



NH,.HC1 

I 1 

HO—/ ^— As 



HO— C >— As 



NH2.HCI 

Snhmrsan is a strong antiseptic in minute concentrations, 
whilst in dilutions from 1 : 1,000,000 to 1 : 500,000 it is a powerful 
germicide. The substance exerts a peculiar selective action both 
as a spirillocide and on anthrax, erysipelas, and glanders, having 
but little action on pneumococci. The selective action is even 
more pronounced in serum.- The isomeric 22'-dihydroxy-44'- 
diamino derivative is less effective than salvarsan.^ Salvarsan, 
unfortunately, somewhat readily undergoes atmospheric oxidation 
to the very toxic oxide, and much ingenuity has been exercised 
on the production of similar derivatives less subject to oxidation. 
N eosalvarsan is sodium-3 : 3-diamino-4 : 4'-dihydroxy-arsenobenzene- 
methanal-sulphoxylate. Arsalyt is methylamino-tetramino-arseno- 
benzene.* 

Laveran,' N(CH3)CH2COOH 



)— As 



NfCH^) CH.COOH 

1 Arch. Exp. Pharm. Path., 1915, 78, 1. " Zcit/^ch. Ili/g. Inject., 1914, 77. 

^ Bauer, Ber., 191.5, 48, 1579. 

4 Leiclimaun, Biochem. Zeit.. 1907, 81, 284. 

5 Dechsler, Annalen., 1907, 234, 1. 



ORGANO-METALLIC DERIVATIVES 271 

is stated to be a powerful trypanocide. According to Berthein,^ 

NHCH3 

I 

As— ^ ^OH 



As—/ >0H 



NHCH3 

is much more toxic than salvarsan and less germicidal. 

More complex derivatives, such as bis-methyl hydrazinetetra- 
aminoarsenobenzene, are to be found in the patent literature. They 
are all trypanosome reactive, but quantitative comparisons with 
salvarsan are not forthcoming. Arsenophenyl has long been used 
as a therapeutic.^ 

A few substituted arsines have been prepared, but appear to 
be relatively unstable, such as HgAs — CgHg — NHCHjCOOH 

and HgAs— C6H3<^j^ . 

The introduction of the halogens, either in the nucleus or the 
side chain, such as 



NH,— C )— Asl, and NHo— < >— Asl. 



results in the production of trjrpanocidal, but highly toxic sub- 
stances. These compounds appear to possess marked s23irillocidal 
properties. The sulphides have a very definite action on parasites, 
but do not appear to possess any marked advantages over other 
substances more readily prepared. Derivatives of the types 



NAA-/ VasS, NRr/ ^AsS.,, and (NRR<^ /As).,S3 

have been prepared. 

A greater measure of success has been attained with the metallic 
salts of the arsenicals, especially those of mercury; those of atoxyl 
are found under the names of atyrosyl and asiphyl.^ A double salt 
of methyl benzene arsonate and mercuric salicylate is the active con- 
stituent of enesol. Danysz* has noticed the interesting fact that 
the addition of silver bromide or iodide to salvarsan considerably 
augments the antiseptic action to a value exceedingly greater than 
tliat obtained by either constituent singly. 

^ Ber., 1915, 350. ' K. Kaliii, Zvitsrh. Angnc. Chcm., 1895, 25. 

^ Blumenthal, Biochem. Zeit., 1910, 28, 91. 
« Ann. Inst. Past., 1914, 28, 238. 



272 DISINFECTION AND STERILIZATION 

Mercury. 

The number of organic mercurials which have actually been 
prepared and suggested for disinfectant or therapeutic purposes 
exceeds those of arsenic. A comprehensive bibliography of the 
compounds which have been synthesized is given by F. C. Whit- 
more.^ to which tlu! reader is referred for chemical references. 

Calomel and highly ionized mercury salts rapidly precipitate 
albumin, thus entailing both a waste of disinfectant on inert 
organic matter, and ineffective ])enetration into the material to 
be disinfected. A minor objection is the action on surgical instru- 
ments. A search for organic mercurials was accordingly conducted 
with the object of obtaining a mercury-containing compound which 
would raj)idly diffuse and slowly liberate an ionized mercury salt 
on hydrolysis, a result partially achieved with colloidal mercury 
(see p. 206). The precipitated albumin mercury complex has, 
however, a germicidal activity ^^er se, and Schrauth and SchoUer^ 
incline to the view that the complex itself is the active germicide. 

Acid Salts. — -The mercuric salts of the acids, such as mercuric 
dipropionate, glycocollate, or dibenzoate,^ are but feeble germicides. 
Mercuric-^J-phenylsulphonate, 



SO3-/ >-0H 



Hg( 



S03-< >-0H 



known in the form of a double salt of ammonium tartrate as asterol, 
is somewhat weaker than mercuric chloride, and is sufficiently 
ionized in solution to attack metals and precipitate albumin. 



The mercurous sulphonate, (Hg — SO3 — (^ ^ — OH)^, or hydror- 

gyrol, is stated not to possess these defects, but is somewhat easily 
hydrolysed in aqueous solution. 

Hermophenyl,* or mercuric phenyl disulphonate, does not pre- 
cipitate albumin, a property shared by meriodin. mercuric phenyl 

/I I 

iodisulphonate, Hg . '\ 

\S03-/ )-OHg. 



1 J. hid. Eng. Chem., 1<)19, 11, 1083. 2 j^^j. ^gog, 41, 2087. 

3 Blumenthal, Biochem. Zeil., 1912, 39, 58; Zc'tsch. Iinmiin. Exp. Ther., 1915, 

41, 47. 

" Lumiere and Chevrothcr, Compt. lend.. 132, 145. 



ORGANO-METALLIC DERIVATIVES 273 

OTT 

Salts of the type Hg<^/^,TTT^ r<r)r)T?' ^nid their anhydrides, 

Hg<^pTTD^CO have been investigated by Scholler and Schrauth, 
and shown to possess a high germicidal activity.^ 

Derivatives of the Phenols. — ^A great number of derivatives of 



the type <^ ^ — OHg — ^OH have been i^repared, as well as 

those of the halogenated phenols, and have been investigated foT- 
germicidal activity by Schrauth and Scholler.- 

Those of phenol, resorcin, and naphthol are readily soluble in 
dilute acids, but somewhat easily hydrolysed. Of the cresol de- 
rivatives, the meta- is stronger than the ortho- or para-compound. 
Upsalan and providal consist of hydroxymercury-sodium-o-chlor- 
phenolate, and the dihydroxymercury derivative. The introduc- 
tion into the nucleus of a second — -OHg — OH grouping has but 
a slight effect on the germicidal activity. 

Similar derivatives of p-xylenol, and thymol, which are not 
readily soluble, have likewise been prepared. 

Carbon Mercury-linked Compounds. — The aliphatic derivatives 

of the type pxr^^Hg are exceedingly poisonous;^ those of the 
aromatic series have been found to be extremely effective spirillo- 
cides, although the hydrocarbon compounds — e.g., Hg<^p^TT^ 

are too toxic for practical utilization. Compounds of the tyise 
R=C=Hg appear to possess little germicidal activity. Scholler 
and Schrauth* have carried out an extensive series of investigations 
on the effect of substitution on sodium hydroxymercuric benzoate, 

COONa 

Hg— OH 



It itself is a powerful germicide, but can be further augmented in 
activity by nuclear substitution with halogens, aliphatic or methoxy 
groupings as in aphidol, the sodium salt of hydroxjanercuric o- 
methyl benzoate. A similar elevation is produced by the introduc- 
tion of a second — Hg — OH group, or by the elimination of the car- 
boxyl from the nucleus. 

Sulphonation, as in hermophenyl, C6H3(HgOH)(S03Na)2, or the 

^ Loc. cit. 2 Zeitsch. Hi/g. Infekt., 1916, 82, 279. 

^ Hopp'.^-Scylcr, Arch. Exp. Path., 1887, 23, 91. 
* Zeitsch. Hyg. Infekt., 1910, 1911, 66, 417. 

18 



274 DISINFECTION AND STERILIZATION 

introduction of a salt-forming hydroxy into the nucleiis as in asurol, 
hydroxymercuric sodium salicylate, or substitution A\ith an amino 
grouping, deijresscs the activity, as would be expected from the 
effect on the water solubility. Heplacement of a hydrogen in the 
amino group by an alkyl or aryl group elevates, and by an acetyl 
group depresses the germicidal activity as in toxynen, 

COONa 

I 



CH3C0NH<' j>— HgOH. 

The introduction of an — ^NOo group into the nucleus elevates its 
toxicity somewhat, but mercurophen, 

NO, 



NaO-i 



-Hg— OH 



is still less toxic than mercuric chloride. According to Schamburg; 
Kolraer, and Raizen,^ it is some fifty times as germicidal towards 
staphylococcus as mercuric chloride, the organism being destroyed 
in bouillon by a dilution of 1 in 10,000,000, whilst by the R.W. 
method (see Chapter XI.) it is stated to be 10,000 times as active 
as mercuric chloride, and has only one-fifth the serum protein pre- 
cipitating effect of this salt. In dilutions of 40,000 to 10,000 to 1 
it is employed as a hand disinfectant. Similar derivatives are 
found under the proprietary names of phenerjol, thymegol, and 
cresegal. Nuclear substitution of — Hgl, — HgBr, — HgCl, — HgS 
likewise produce substances of great germicidal activity. Internal 
linkages are suggested by anhydrides of the type 

CO 



OH O 



Hg 



but their germicidal activity would not be greater than that of 
the corresponding acids or salts. 

BlumcnthaP has investigated compounds of the type 



NH2 NH, 



Hg- 
COONaJ, COONa 

1 J. Amcr. Mid. .l-s-wr., 1917. - liiochon.. Zcit., 1911, 32, 59. 



ORGANO-METAI;LIC DERIVATIVES 275 

with pp'-^H.^ groupings. The 00/ and 7rim,' compounds have like- 
wise been prepared. They are strong spirillocides, and their activity 
can be augmented by the nuclear introduction of an — NOo, — OH, 
or NHo grouping. 

Mercury Nitrogen Linkages. — Intermediate in spirillocidal 
activity between the compounds of the type R — — Hg — OH and the 
more potent R — Hg — OH and R — Hg — R' derivatives are found a 
few compounds of the type =N — -Hg — N = , derivatives of amides 

such as Hg<^^TT.,xj^. the formamide of Liebreich, and Vollert's 

succinamide derivative, C2H4<CpQ>N — Hg — ^N-cC^^iQ^CgH^. 

Comparative data on the germicidal activity of compounds of this 
type are, however, lacking. Schollcr and ISchrauth^ have also 
reported favourably on — S — Hg linked derivatives such as 

NaOgS— S— Hg— CH^COONa and NaSOg— S— Hg— CgH^COONa. 

Silver. 

For eye infections, as well as for the treatment of infection by 
micrococci, a number of organo -argentic derivatives have been 
introduced. These include silver salts of the fatty and aromatic 
acids, such as silver citrate, itrol ; lactate, actol ; the glycollate; 
phenyl sulphonate, silberol ; the picrate ; the nitro-picrate, picrntol ; 
the silver salt of 2J-^3'droxyphenyl sulphonate, a septal ; and 
rt-quinoline and oxyquinoline silver phenyl sulphonate, argentol ; 
acetyl guaiacoltrisulphonate, eosolate. Silver salts of thio fatty 
acids, such as ichthargon or silver ichthyol sulphonate, have likewise 
been suggested. A few complex salts of the type of ethylene diamine 
silver phosphate, argenfamine, are also to be noted, but by far 
the greater number of organic silver derivatives consist of colloidal 
silver protected by some suitable colloid (see p. 207), or adsorption 
compounds of silver ions with some complex organic acid which 
can easily effect reduction of the ion to the metallic state. Of 
these substances, which are to be regarded not so much as chemical 
compounds, but as protected colloids, may be mentioned the 
caseinates, argonine, omaral (10 per cent. Ag), and protargol 
(83 per cent. Ag);- the nucleinates, so])hol, argyrol, nargol, and 
navergan, stated to be less toxic than protargol; the albuminates, 
largin, hegonon, and choleval — colloidal silver ]3rotected with 
sodium gallate and silver galactose. A report by the British 
Medical Association in 1!(06 gives the time in minutes required to 
kill S. pyogenes miretis by the following preparations : 

^ her., 1907, 40, aso. 

'■' Noiszer, Dcrnialul. Zcnlr., 1897, 1- 



276 DISINFECTION AND STERILIZATION 

Substance. (Joncentralion. Time. 

Argonine . . . . 5 per cent. . . . . 3-0 minutes. 

Protargol . . . . 2-4 ,, . . . . 3-5 ,, 

Largin . . . . 10 ,, . . . . 2-5 ,, 

Silver nitrate .. .. |-2 ,, .. .. 2-5 ,, 

The colloidal silver derivatives, such as argyrol (protected with 
gluten) and collargol, had but little bactericidal power. 

Copper, Gold, and Platinum. — A few organo-metallic compounds 
of cojjper, gold, and the platinum group of metals have been in- 
vestigated for germicidal activity. It would seem desirable to 
investigate those of copper in more detail, since germicides 
approaching the mercurials in activity could probably be prepared. 

Copper salts of the type CuBgX^, Cu^BX^, where X is a halogen, 
— CN or — CNS and B a univalent-N-alkylhexamethylene tetra- 
mine, are suggested in the D.R.P., 284, 260. 

Salvarsan derivatives, in which the copper is either Imked direct 
to the arsenic or as a double salt of cupric chloride, are said to be 
strong bactericides and sjiirillocides.^ Cupric chloride, stannate, and 
cinnamate, with lecithin ( lecutyl) , have been employed with success for 
tubercle infections.- S. Mackenzie has shown that copper alanme^ 
has a low toxicity, is soluble, and does not precipitate proteins. It 
is fatal to protozoa in dilutions of 1 : 100,000. Cwpraiin, copper 
albuminate; cuprol and cwpragol, the nucleinate; and cupriaseptol, 
copper w-hydroxyphenyl sulphonate, have likewise been prejDared. 
Double salts of gold cyanide, such as cholineaurocyanide, 
piperazine, aurocyanide, and aurocantan, have been utilized for 
tubercular infections. Crysolgan, the sodium salt of the 4-amino- 
2-aurophenol-l-carboxylate, is stated to inhibit the growth of 
tubercle bacilli in a dilution of 1 : 1,000,000. iV-alkyl-hexa- 
ni ethylene auric iodide and sulphocyanide are stated to be germi- 
cidal. The high cost of these preparations, however, limits their 
application; this is also true of the palladium compounds, chiefly 
employed as the double salts of palladium chloride. 

Aluminium. — Aluminium salts have been incorporated in a 
number of organic preparations; the germicidal activity is, however, 
not due to the presence of the aluminium, A\'hich merely performs 
the function of an astrmgent. Of these, which are both astringent 
and antiseptic or feebly germicidal, may be mentioned lutol and 
horol, the borotartrate ; acetonal, aluminium sodium acetate; 
alsol, the aceto tartrate ; acetoform, acetyl citrate of aluminium 
hexamine; morinal, normal basic aluminium sulphite and formal- 
dehyde; aluminol, aluminium-^-naphthol sulphonate; alkazal, 
1 D.R.P.. 30-), o;{0. 

^ V. Linden, Zenlr. Blochcni. Biuphija., I'Jl"), 18, 407; Thcruj). Monida., I'JlT. 
33, 13. 3 j/g^ p^^^,,.^ i,jn5_ 50^ 2. 



ORGANO-METALLTC DERIVATIVES 



277 



the potassium salicylate; sozal, aluminium-p-hydroxyphonyl sul- 
phonate; saJumin, the salicylate; tanned, a double salt of 
aluminium tartrate and tannate; gallal, the basic gallate; autol, 
aluminium borotannate; boral, aluminium borotartrate and boro- 
formate. Alformin is basic aluminium formate.^ 

Of the organo-metalloids, in addition to arsenic derivatives, 
a number of substances containing antimony, selenium, tellurium, 
and especially sulphur, have been prepared, all possessing germicidal 
or spirillocidal activity. 

Wassermann has utilized selenium and tellurium compounds 
in the treatment of spirochetes and of protozoa, such as eosine 
selenium and selenium methylene blue, 

N 



(CH3).3N- 
Other derivatives, such as 




SeCl 
are also stated to be effective. 

Antimony. 

Antimony as -well as bismuth organic compounds are trypano- 
cidal, like arsenic, but much weaker in their action. As in the 
case of arsenic, trivalent antimony compounds are more effective 
than the pentavalent derivatives. Thus, according to I'hlenhut 
and Hiigel,- antimony atoxyl, or sodium-p-aminophenyl stibnate, 
as well as its derivatives, have but little effect on spirilla; the 
sodium acetyl derivative appears to be slightly active, whilst the 
sodium-m-amino-7>-urethano-phenyl stibnate possesses a marked 
spirillocidal activity. Derivatives of trivalent antimony, such as 

NHo 



Sb- 



)— OH 



Sb— < 



)— OH 



NH, 



have been claimed as trypanocides.^ Stibacetin, like arsacefin, is 
an effective trj'panocide. Of the more important aliphatic anti 

1 Harzbecker, AUg. Med. Zentr., 1910, 85, 197. - Deut. Med., 1915, 2455. 

^ Heyden, D.R.P., 208,451. 



278 DISINFECTION AND STERILIZATION 

mony derivatives may be mentioned potassium ammonium anti- 
mon}'! bitartrate, or antiluetin, a trypanocide, and antimony salts 
of fatty acids such as ethyl antimony tartrate.^ Organic 
derivatives containing both antimony or bismuth and arsenic have 
been prepared as trypanocides by Ehrlich and Kamer.- The 
following compounds were found to be effective trypanocides : 

NH, 



Sb— (^~ 
As— <^ 


")- OH 

^— OH 
NH„ 


OH 

1 /- 
0=As— < 

1 ^- 
OH 


OH 

\ Sb = 

— ^ 1 

NO2 OH 



and derivatives of the type RAsBiCl, where R indicates an aryl 
grouping. Marcjoh or antimonyl silver bromine arseno-benzene, 
is stated by Danysz and RaspaiP to be as effective as salvarsan. 

Bismuth. 

Compounds precipitating basic bismuth salts have frequently 
been suggested as substitutes for iodoform.'' and for internal anti- 
septics. The antiseptic power of these bismuth derivatives, as 
distinct from the organo-bismuth C^ — Bi linked derivatives, is to be 
attributed to the organic residue, the bismuth oxide itself possessing 
no germicidal and very weak (if any) antiseptic activity. The 
oxide, however, performs in certain cases a useful function as a 
protective agent. 

Amongst the aliphatic compounds are to be noticed the citrate, 
malate, and lactate, as well as complex bismuth oxide derivatives 
similar to tartar emetic, such as bismutho-tartaric acid. 

Bismuth oxide and phenol; tribromophenol, xeroform ; and 
/3-naphthol, orphol ; are found amongst the phenol derivatives. 
Amongst the organic aryl acid derivatives may be mentioned 
bismuth gallate, dermatol and airol ; the tannate, tannismut ; 
bismuth oxyiodogallate. ihit or airoform ; iodylin, the salicylate; 
thioform, the dithiosalicylate ; and hefoform, the cinnamate. More 
complex are the dilactomonotannate, lactamm ; the borophenate, 
marcasol- the basic gallosulphonate ; the bisalic3'late, qastrotan ; 
the iodosalicylate, iodoyhin ; the methylene gallate, hismal ; and 
helcosol, the pyrogallate. Crurin is stated to be a double thio- 
cyanate of quinoline and bismuth ; bismutose, the albuminate and 
pei:)tonate; and jxinthismut, the nucleinate. 

1 Thomson and Crosby, Proc. Roy. 80c. , 82B, 249. ~ Brr.. 1013. 46, 3^04. 

■5 Munch. Med. Wochensch., 1916, 132, 83(). 

* Steinfeld and Meyer, Arch. Path. Pharm., 20, 40. 



Y 



ORGANO-METALLIC DERIVATIVES 



271 



Sulphur. 

The antiseptic and germicidal j^roperties of the organic deriva- 
tives of hydrogen sulphide have already been referred to. Of the 
more complex organic thio compounds, those of ichthyol stand 
prominent for the treatment of skin infections such as scabies and 
eczema. Ichthyol is a water-soluble sulphonic salt of an aliphatic 
derivative containing 10 per cent, of sulphur; its composition, 
probably complex, is unknown, but the organic sulphur may exist 
in the form of a thiozonide resulting from the direct addition of 
sulphur to an unsaturated linkage : 

— CH.^— CH=CH— CH2+S3 - — > — CH.,— CH— CH— CH.,— 



8 8 

Ichthyol substitutes have been prepared in this way, the hjxlro- 
carbon being made water-soluble by sulphonation, whilst deriva- 
tives, such as twnenol, are prepared by the introduction of sulphur 
into cracked paraffin after sulphonation. 

Of the more important ichthyol derivatives which have been 
proposed may be mentioned : 

Ichthalbin, containing egg albumin ; ichthoform, containing form- 
aldehyde, ichthargon and ferrichthol containing colloidal silver 
and iron respectively. Putinol and desichthol appear to be ichthyol 
rendered odourless by steam distillation. 

Of the other sulphur organic compounds which are weakly 
antiseptic may be mentioned iniramin 



8— < 



S— < 



)— NH, 



)— NH, 



suggested by MacDonagh^ as a substitute for salvarsan; thiuret 

C,H5N=C 8 

NH 

I 
HN=C 8 

and derivatives of thiourea ; as well as thioresorcin and sulfaminol, 

I 8 — 8 I 

-N- 

I 
H 



OH 

^ Lancet, 1010, i.. 2S(1. t;:{7; Jirit. Med. ./., 190(!. i., 202. 



CHAPTER XIV 
METHODS OF ANALYSIS AND TESTING 

Bacteriological Methods of Standardizing Disinfectants. 

That a chemical analysis of a disinfectant does not give sufficient 
data from which to determine its germicidal value is at once evident; 
for, although the activity is generally increased if we augment the 
quantity of the active ingredient present, we still have no method 
of determining which is the active substance, nor can we compare 
the relative value of different active ingredients in different ger- 
micides. 

Furthermore, the germicidal power of a disinfectant is greath^ 
affected, not only by its chemical composition, but also by its 
physical condition — e.g., whether ionized or non-ionized, emulsified 
or in solution, hot or cold. 

Many attempts have been made to derive a satisfactory test 
so conducted that the bactericidal efficiencies of disinfectants may 
be compared one with another. The preliminary work of Klein, 
Castro, and Wynter-Blyth in England; Sternberg in America; and 
Koch, Esmarch, Fraenkel, and Geppert on the Continent, showed 
to some extent the magnitude of the difficulties which had to be 
faced. 

The first method to give anything like uniform results was 
devised by Robert Koch in 1892, and is generally known as the 
thread method. The test is briefl}^ as follows: Threads loaded with 
anthrax sjDores are subjected to exposure for various lengths of 
time in the solution to be tested. After removal the}- are washed 
and placed in nutrient gelatine or used for inoculating animals. 
The germicidal value is estimated by the duration of the exposure 
necessary to cause the death of the spores. 

At a later date Delepine at Manchester has used a modification 
of this method with cultures of non-sporing organisms, such as 
B. coli and B. typhosiis.^ There are several objections to the method 
which render the results uncertain. It is frequently difficult to 
remove the last traces of grease from oft' the threads, alternate 
washings with alkali and acid followed by alcohol being the most 

efficacious. 

^ J. Roy. San. Inst., 1907, 28, T. 
280 



METHODS OF ANALYSIS 281 

A more serious error arises from the fact that when the threads 
are partially dried without any attempt being made to remove 
the organic matter of the broth emulsion, a film of dry albuminous 
matter is formed on the surface, acting as a protection to the 
organisms. According to V. Gerlach'^ the after-washing is. in the 
case of emulsified disinfectants, not sufficient to remove all the 
disinfectant, which may still be present in inhibiting quantities. 

In 1 897 Kronig and Paul suggested what is known as the garnet 
method, which had certain advantages over the thread method of 
Koch, inasmuch as the test bacteria were dried on the surface of 
little garnets of uniform size at a low temperature over calcium 
chloride, and could be washed and treated with chemical reagents 
to neutralize and prevent the carrying over of small quantities of 
the disinfectant fluid into the test culture, which occurrence, espe- 
cially in the case of mercury salts, tends to inhibit, if not destroy, 
any subsequent growth where disinfection has originally not been 
completed. 

In 1903 one of the authors, in conjunction with Mr. Ainslie 
Walker, devised a standard method for the examination of disin- 
fectants which is the original basis of the many modifications in 
use at the present time. This method was devised to take into 
consideration as far as practicable the following factors : 

1. Time. 

2. Age of culture. 

3. Choice of medium. Reaction of same. 

4. Temperature of incubation. 

5. Temperature of medication. 

6. Variations in vital resistance of same species. 

7. Variations in vital resistance of different species. 

8. Proportion of cTilture to disinfectant. 

9. Universal standard as control. 

It was suggested at the time that pure jahenol should be used as a 
control standard in preference to mercuric chloride, which suggestion 
has met with universal adoption. In making up solutions of phenol 
of any definite strength, it must be borne in mind that the so-called 
pure crystals contain at times as much as 7 or 8 per cent, of water,^ 
and are frequently contaminated by cresols,'' which may exert a 
considerable germicidal effect in the solution, although present in 
very small quantities. The purity of the crystals should, therefore, 
be ascertained by a melting-point determination (40-;")'^ C). whilst 
the stock solutions are conveniently standardized by Itromine 
titration. 

' Zeitsch. Angew. C'hem., 1901, 14 and 15. 

2 Ridcal and Walker, J. San. Inst., 1903. 

=* J. M. Wei.ss, J. Franklin Inst., December, 1912, 083. 



282 DISINFECTION AND STERILIZATION 

With regard to the keeping properties of phenol solutions, 
the evidence is somewhat obscure; it has been suggested that 
polymerization and possible alteration of germicidal strength occur 
on storage. Our own experience is that, if not too much solution 
is made up at one time, and if the solutions are kept in the dark, 
in those laboratories where tests are frequenth' being made there 
is very little possibility of sufficient time elapsing to cause any 
considerable error in testing. 

The following are the original details of the Rideal- Walker 
method : 

Materials required for Test. 

Nutrient Broth. 

Liebig's extract of meat . . . . . . 20 grammes. 

Peptone fWitte's) 10 

Salt (sodium chloride) . . . . . . 10 ,, 

Distilled water . . . . . . . . 1 litre. 

Boil the mixture for thirty minutes, then filter, and neutralize 
with normal sodium h3'drate solution, using phenolphthalein as 
indicator. In order to avoid contaminating the broth with phenol- 
phthalein, it is advisable to take an aliquot part of the filtered 
broth — say 10 c.c. — and titrate this with decincrmal sodium hydrate, 
calculating the amount of normal sodium hydrate necessary for 
the neutralization of the remainder of the broth. Add when quite 
neutral 15 c.c. of normal hydrochloric acid. This will give the 
broth a reaction of 1-5 per cent. The broth is then made up to the 
litre, filtered and sterilized. Where 2 or 3 litres are prepared 
at one time, as is customar}^, the broth is distributed in 500 c.c. 
flasks on the following day and again sterilized.^ Five c.c. are then 
run with the aid of a small sej^arating funnel into sterile test-tubes, 
which, after plugging with sterile cotton-wool, are placed in the 
steam sterilizer for half an hour or so. 

Standard Carbolic Acid. — -A 5 per cent, (by weight) stock solution 
is prepared and standardized by titration with stock bromine. 
From this solution the various working strengths are made up 
by diluting some comparatively large quantity, such as 100 c.c., 
to the desired volume ; this serves to ehminate the error introduced 
by measuring out small quantities of strong acid. 

Dilutions of the Disinfectant. — A stock solution or emulsion 
should be pre})ared in a 500 c.c. stoppered cylinder with sterilized 
distilled water — 10 per cent, if the coefficient be under 1, and 
1 per cent, if over 1. Ten c.c. of this stock solution are used in 

^ Cheap bad glas.swaro frequently contains sufticient soluble alkali to effect 
the reaetic)n. 



METHODS OF ANALYSIS 283 

preparing each of the four dihitions required for the test. Thus, 
working with a sample having a coefficient under 1, if it is desired 
to prepare a dilution of 1 : 70, 10 c.c. of the 10 per cent, stock 
solution are diluted with 60 c.c. of distilled water; and in the case 
of a preparation having a coefficient over 1, where the dilution 
required is 1 : 700, 10 c.c. of the 1 per cent, stock solution should 
be diluted with 60 c.c. of water. In prej)aring dilutions of the 
unknown, the limitations of the test must not be overlooked. The 
following is a safe rule for general work, expressing the dilutions 
as multiples of the carbolic acid dilution : 

With coefficients of 1 and under .. .. .. .. xO-1 

With coefficients above 1, but not exceeding 10 . . . . x 0-5 

With coefficients above 10, but not exceeding 20 . . x 1-0 

For example, assuming the strength of the carbolic acid control 
to be 1 : 100, when it is desired to test a sample having a co- 
efficient of 10, the dilutions to be recommended would be 1 : 950, 
1 : 1,000, 1 : 1,050, 1 : 1.100. 

The Broth Culture. — B. typhosus, grown in R.W. broth and 
incubated for twenty-four hours at 37" C, provides the test culture. 
To ensure even distribution of the bacilli in the broth culture, and 
to avoid the necessity of filtration, the culture-tube should be 
shaken and allowed to rest for half an hour before it is finally 
removed from the incubator, the temperature of M'hich should not 
vary more than half a degree from day to day. It is advisable 
to make a subculture every twenty-four hours from the previous 
twenty-four hours' culture, even if on many days no test is to be 
performed; but as this tends to attenuate the organism, it should 
be continued for not more than one month, after which a fresh 
subculture in broth should be taken from a month-old agar culture. 
By this means a culture not varying much from day to day in 
resistance to disinfectants is obtained, making the selection of 
the proper dilution of carbolic acid much easier than it would be 
if the culture from which the twenty-four-hour growth is obtained 
were older on one occasion than another. 

Apparatus required for Test. 

Test-Tube Rack. — A special rack is used. It contains two tiers, 
the upper having holes for thirty test-tubes, in two rows, each rov,- 
containing three sets of five; this tier is for the sterilized broth- 
tubes, each of which is numbered with grease pencil. The lower 
tier is for the medication-tubes — four with disinfectant dihitions. 
and one with carbolic acid control dilution, the latter being placed 
in the fifth hole. The lower tier is provided with a copper water- 



284 DISINFECTION AND STERILIZATION 

bath to keep the temporaturo of medication within the prescribed 
limit, — -15° to 18*^ C. The test-tubes being numbered in rotation, 
it will be seen that the hrst medication-tube is used for inoculating 
broth-tubes 1, 6, IK 16, 21, and 26; the second for 2, 7, 12, 17, 
22, and 27, etc. 

Inoculating Needle. — The needle used should be composed of 
thin aluminium rod. \vith a short piece of platinum wire (26 U.S. 
gauge) passed through and twisted round an eye in the end of the 
rod, or otherwdse firmly fixed thereto. The wire is made into a 
loop at the end, and bent slightly in the centre to allow of a fair- 
sized drop being taken up for each inoculation. Satisfactory 
results cannot be expected when one tube is inoculated with a full 
drop and a mere film is introduced into another. The length of 
the wire to end of loop should be about 1| inches. After a little 
practice it is easy to obtain a satisfactory drop by dipping the 
needle in the medicated culture and bringing it out with a slight 
jerk. The loop has an internal diameter of 3 millimetres. 

Test-Tubes. — The test-tubes should be of fairly strong glass, so 
as to minimize as far as possible the risk of breakage, and lipped, 
to facilitate manipulation of plugs. Five inches by | inch is the 
size recommended for use. The cotton-wool plugs for both medica- 
tion-tubes and broth-tubes should be well made, so that they can be 
withdrawn and replaced Avithout loss of time. A convenient 
method is to place a thin flat piece of cotton-wool over the mouth 
of the test-tube, with a smaller piece in the centre to form a core, 
and to push both into position with the aid of a thin glass rod. 

Dropping Pipette. — This is used for the broth culture, and is 
loosely plugged at the top with cotton-wool, and when not in 
actual use is kept in a sterile test-tube plugged at the mouth with 
cotton-wool. For greater convenience, the tube should be passed 
through the centre of the plug and fastened thereto with wire. 

In addition to the above, one or two each of the following are 
required: 1, 5, and 10 c.c. capacity pipettes; 100 and 250 c.c. 
stoppered cylinders (with inverted beakers, to safeguard against 
dust after removal from sterilizer); wire baskets to receive tubes 
for incubation or sterilization. All pipettes and cylinders should 
be sterilized. 

Technique. 

Before commencing the test it is necessary to ascertain the 
carbolic acid control dihiiion which will give the desired result — 
i.e., life in two and a half and five minutes. This is done by running 
a trial test with five dilutions of the carbolic acid only^ — say 1 : 80, 
1 : 90, 1 : 100, 1 : 1 10, and 1 : 120. Five c.c. of the control solution 



METHODS OF^ANALYSIS 285 

so ascertained are then pipetted into the fifth medication- tube, the 
other four receiving 5 c.c. of the various dilutions of the disin- 
fectant under test. To save time and apparatus, one pipette can 
be made to do service at this stage by starting with the phenol 
solution, and following on with the highest or lowest dilution of 
the disinfectant, according as the coefficient is below or above 1, 
rinsing out the pijoette in each case with the next dilution before 
measuring off the sample for test. 

The plug of the culture-tube is now rejDlaced by the culture 
pipette, which, as explained above, has a plug attached to it with 
wire at such a height that when the plug fits easily into the mouth 
of the culture-tube, the point of the pipette is half-way down the 
broth, and clear of the lumps. The first of the five medication- 
tubes is now inoculated with five drops of the culture. At intervals 
of half a minute each of the other medication-tubes is inoculated 
in turn. By the time the fifth tube has been inoculated the organism 
in the first will have been exposed to the action of the disinfectant 
for two minutes, and after the next half-minute a loopful of the 
latter is inoculated into the first broth-tube, loojofuls from the other 
medication-tubes being in turn inoculated into their respective 
broth-tubes at the rate of one every thirty seconds. By the time 
the fifth broth-tube has been inoculated from the fifth medication- 
tube, the disinfectant in the first medication- tube will have acted 
on the test organism for four and a half minutes, and after the next 
thirty seconds a loopful is introduced into broth-tube 6, and so 
on. The actual test, therefore, occupies seventeen mmutes, and 
provides for six two and a half minute periods of contact in each of 
the five medication-tubes. 

It is open to the worker, of course, to adopt any convenient 
method of manipulating the tubes and plugs. The following 
procedure is given for the guidance of the inexperienced : The 
first medication- tube is taken from the rack and the contents 
gently agitated for a second to ensure even distribution of the 
bacilli; the plug having been taken out and grasped b}^ the left 
little finger, the tube is held by the back of the left forefinger and 
the front of the second. The corresponding broth-tube (No. 1) 
is taken up by the right hand and transferred to the left between 
the thumb and forefinger, the plug being extracted and held by 
the little finger of the right hand. The tubes now being in j^osition 
for inoculation, the needle, which should have been sterilized before 
the tubes were touched, is introduced into the medication-tube, 
from which a loopful is taken and inoculated into the broth- tube. 
The needle is sterilized in the flame (jilaced to the right) and pushed 
with a movement of the thumb w ell up between the first and second 



286 



DISINFECTION AND STERILIZATION 



fingers of the right hand ; the phigs are then replaced, the medication- 
tube going back to the rack, whik> the broth-tube is subjected to a 
gentle agitation and placed in a wire basket on the right of the rack. 
This basket, containing the thirty inoculation-tubes and the test 
form giving particulars of the dilutions, etc., is now placed in the 
incubator, Avliere it is allowed to remain for fortj'-eight hours at 
blood heat, when the results are read off. A moment's consideration 
of the manner in which the test has been conducted will suffice to 
indicate where the results of each subculture should be placed 
in the table. 

The strength of efficiency of the disinfectant under test is 
expressed in multiples of carbolic acid, and is obtained by dividing 
the dilution of the disinfectant showing life in two and a half and five 
minutes by the carbolic acid dilution, which, of course, must show 
the same result. 

To avoid annoyance and loss of time caused by aerial contamina- 
tion of tubes, etc., it is advisable to conduct the test in a room free 
from draughts; a further safeguard is provided by spraying or 
swabbing the fioors and benches with an efficient disinfectant 
solution. Needless to add, all pipettes, etc., must be rigorously 
sterilized before use. 

The following example represents a typical test: 

Disinfectant A. Bulk Sample. 

Temperature, 18° C. 

Test organism, 24 hours' broth culture. B. typhosus. (Rawlins). 





Time of Exposure (Minutes). 




2i- ; 5 


7i 


10 ■ m 


15 


'A' 1/1,700 

„ 1/2,000 

„ 1/2,300 

„ 1/2,600 
Carbolic Acid 1/100 


-1- 
-t- 
+ 
+ 

+ 


+ 
+ 

-1- 

+ 


+ 


+ 


+ 


- 



,, ^ . . 2,000 ,^,^ 
Coefficient, -r,/,- = 18-2. 



It should be borne in mind that no table can be accepted with this 
or any other method which does not show a harmonious curve. 

It will be noticed that the conditions laid down in the method 
embrace all the factors alluded to above. Since the pubHcation 
of this method of testing there have been several critical investiga- 



METHODS OF ANALYSIS 287 

tions made of the methods of conducting the test, with the result 
that there are now a large variety of tests embracing one or more 
ideas which the investigations have brought forth. 

The following are some of the more important modification tests 
since introduced : 

The Hygienic Laboratory Method. 

This method, introduced by Professor J. F. Anderson and 
Dr. T. B. McClintic of the National Hygienic Laboratory, Washing- 
ton, D.C., in 1912, closely follows the R.W. method, and is con- 
ducted as follows: 

Media. — The broth made from Liebig's extract of beef of a 
reaction -i- 1-5 is prepared in accordance with the standard methods 
adopted by the American Public Health Association for water 
analysis. 

Ten c.c. of broth are put in each test-tube. 

Organism. — A twenty-four hours old broth culture of the 
B. typhosus originally isolated from a patient in the Johns Hopkins 
Laboratory about the year 1906. Subculturings every twenty- 
four hours on at least three successive daj^s is advised. 

A 4 -millimetre platinum loop of 23 I'.S. gauge is used, and one 
loopful taken. (This size loop is also used for transfer of the culture 
after exposure to the disinfectant.) Before being added to the 
disinfectants the culture is well shaken and filtered through sterile 
filter-paper and placed in the water-bath at 20° C. 

Temperature. — The standard temperature of 20" C. is adopted. 

Proportion of Culture to Disinfectant. — One tenth c.c. of the 
broth culture is used, added to o c.c. of the disinfectant solution 
The amount is measured with a graduated pipette. 

Incubation. — The subcultures are incubated forty-eight hours 
at 37"^ C, and the results read ofi and tabulated. 

Dilutions are made with capacity pipettes and 5 per cent, phenol 
solution is used as stock standard. 

Determination of the Coefficient. — ^Subculturesare made every two 
and a half minutes up to and including fifteen minutes. To deter- 
mine the coefficient, the figure representing the degree of dilution 
of the weakest strength of the disinfectant that kills in two and a half 
minutes is divided by the figure representing the degree of dilution 
of the weakest strength of the phenol control that kills \\ithin 
the same time. The same is done for the weakest strength that 
kills in lifteen minutes. The mean of the two is the coefficient. 



288 



DISINFECTION AND STERILIZATION 



Example. 
Name "A." 

Temperature of medication, 20° C. 

Culture used, B. typhosus, twenty-four hours' extract broth, 
filtered. 

Proportion of culture and disinfectant, 0-1 +5 c.c. 







Time Culture exposed to Action of 










Disinfectants for Minutes. 




Sample. 


Dilution. 






Phenol 












> 1 


Coefficient. 






2* 


5 


n 


10 ' 12i 16 

1 j 




( 


1: 80 














Phenol . . 


1: 90 
1:100 


+ 
+ 


+ 


+ 


- 








1:110 


+ 


+ 


+ 


+ + 


- 




• 


1:350 


_ 


- 


- 






375 650 




1:375 


- 


- 


- 






80 """no 




1:400 


+ 


- 


- 


- 




2 




1:425 


+ 


+ 


_ 


_ ' _ 


_ 




1:450 


+ 


+ 


_ 


- ! - 


_ 


4-69+ 5-91 


Disinfectant . . - 


1:500 


+ 


+ 


- 


- 


- 


2 




1:550 


+ 


+ 


+ 


- ' - 


- 


= 5-30 




1:600 


+ 


+ 


+ 


+ - - 1 






1:650 


+ 


+ 


+ 


+ + 


- 






1:700 


+ 


+ 


+ 


+ , + 


+ 






1:750 


+ 


+ 


+ 


+ 1 + 


+ 





The "Lancet" Test. 

This was originally published in November, 1907, and promi- 
nently brought forward at the Cambridge Meeting of the British 
Pharmaceutical Conference in 1910 by Professor Sims Woodhead 
and Vj. Ponder. It followed the R.W. principle, but with the 
following important departures: 

1. Number of Dilutions and Time Periods. — ^The number of time 
periods was increased, the maximum length of time during which 
the disinfectant was allowed to act increased from fifteen to thirty- 
minutes. 

2. The Organism and Medium. — ^The Bacillus coli communis was 
substituted for ihnB. lypliosus. McConck-^y's medium was used for 
subculturing. 

3. The sample of tlie mixture taken after the action of the disin- 
fectant on the micro-organism was taken by means of small platinum 
spoons of capacity 0-08 c.c. 

4. The broth was prepared as folloAvs : 1 pound minced fat-free 
bullock's heart broth macerated with cold water for two to three 



METHODS OF AjSIALYSIS 



289 



hours, cooked slowly over a small flame for two or three hours more, 
then boiled and filtered and made up to 1 litre. Ten grammes of 
sodium chloride and 10 grammes of Witte's peptone were then added, 
and the solution standardized to an acidity of + l-o of j^henol- 
phthalein. The culture obtained in the broth was first shaken and 
then filtered through a double layer of Swedish filter-paper before 
use. 

5. The coefficient was obtained b}- taking the mean of two figures : 
(a) The weakest dilution of the disinfectant Mhich kills in two 

and a half minutes. 

(6) The coefficient for the thirty minutes period obtained in 
the same way. 

6. The standard temperature lay between 62" and 67' F., 
room temperature. 

The following table illustrates the results obtained by this method : 

TABLE X. 















Dilui 


ions. 














1 


1 


1 


1 


1 


I 


1 


1 


1 


1 


1 


1 


Minutes. 


500 


600 


700 


800 


900 


1000 


1100 


1200 


1300 


1400 


1500 


1600 




•2 


•166 


•143 


•125 


•111 


•1 


•091 


•083 


•077 


•071 


•068 


•062 




per 


per 


per 


per 


per 


per 


per 


per 


per 


per 


per 


per 




Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


■^ 











+ 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


o 














+ 


+ 


+ 


+ 


+ 


+ 


+ 


+ 


n 

















+ 


+ 


+ 


+ 


+ 


+ 


+ 


10 











+ 








+ 


+ 


+ 


+ 


+ 


+ 


12i 























+ 


+ 


+ 


+ 


+ 


15 























+ 


+ 


+ 


+ 


+ 


20 


























+ 


+ 


+ 


+ 


25 





























+ 


+ 


+ 


30 





























+ 


+ 


+ 



Carbolic Acid Control. 









Percentage 


Dilution^ 








Minutes. 




















b37 


1-22 


MO 


1-00 


0^917 


0-846 


0^786 


0^73 


■^ 











+ 


+ 


+ 


+ 


+ 


5 











+ 


+ 


+ 


+ 


+ 


25 

















+ 


+ 


+ 


30 

















+ 


+ 


+ 



Room temperature, 64° F. 
MO 0^917 
Coefficient is therefore 0-143 0-077 _^ 7-7+ IbO 



19 



2i)U DISINFECTION AND STERILIZATION 

The Lancet Commission further proposed certain chemical 
tests by which to classify the " tar acid " class of disinfectants. 
This will be dealt with under that section. 

These two methods incorporate the results of all the criticisms 
levelled at the actual working operations of the R.\A'. test itself, 
which criticisms may be summarized as follows : 

Choice of Organism. — The advantages claimed for B. coli com- 
munis as a test organism over the B. typhosus are : 

1. It is non-pathogenic. 

2. Constant biological characters may be obtained by carrying 
on a culture every twenty-four hours in broth of standard com- 
position. 

3. McConckey's bile salt medium for subculturing practically 
eliminates accidental contamination. 

It has been found thati^. coli is about 10 per cent, more resistant 
than 5. typhosus in the R.W. test. 

Anderson and McClintic, who devised the Hygienic Laboratory 
method of testing, had both the R.W. and the Lancet method 
before them in making their test, and chose i^. typhosus in preference 
to B. coli on account of the greater reliability of strains in the former. 
They further found that the comj)aratively expensive bile salt 
media have a much greater restraining influence on attenuated 
organisms of the typhoid colon type, such as is the case after they 
have been exposed to the action of disinfectants. liB. typhosus is 
used and an error is suspected, an agglutination test may be con- 
ducted to prove the point. The pathogenic powers of cultures of 
B. typhosus grown for several j-ears on culture media are not so great 
as to be a deterrent from using this organism. 

It will be noted that both the modifications insist upon the 
necessit}' of filtration of the inoculated broth, while the Hygienic 
Laboratory go so far as to advise three twenty-four hours' sub- 
cultures before filtration. In regard to this point, our o\^ti ex- 
perience has led us to believe that filtration is not bj' Q,ny means 
always necessary. The necessity or otherwise of filtration rests 
in the fact whether the culture gives a smooth curve or an irregular 
one, and we find that only very rarel}' does a good vigorous culture 
give a broth containing clotting groups which are responsible for 
erratic results and consequently necessitate filtration. Filtration 
has also the minor drawbacks of increasing the risk of contamina- 
tion and relatively lowering the resistant action to disinfectants. 
The three subcultures advised by the H^-gienic Laboratory make 
the test a someAvhat lengthy one to carry out. 

Choice of Culture Medium. — The disadvantages of bullock's 
heart broth in preference to " Lemco " broth are briefly : 



METHODS OF ANALYSIS 291 

Bullock's heart broth provides a more resistant culture medium 
to disinfectants than "Lemco " broth, although in both eases the 
resistance of bacteria to phenol is the same. The followmg tests 
illustrate the retarding action of the broth : 

Disinfectant C'.A./B. W . ^^j^ Bullock's Heart Broth 

(1) .. .. 21-6 .. .. 9-0 

(2) .. .. 19-0 .. .. 100 

(3) .. .. 190 .. .. 70 

(4) .. .. 19-5 .. .. 13-0 

If the bullock's heart broth is uniform in composition there 
will be no objection to its use, although lower figures are obtained 
with it. But such factors as to whether the bullock is yomig or 
old. under- or over-fed, or whether the heart be fresh or chilled, 
influence the growth of bacteria in the broth. 

Time Factor. — -The recommendations of the Lancet Commission 
to extend the time contact from fifteen to thirtj' minutes, and to 
take the mean of the two and a half and thirty minutes figures in 
order to incorporate the effect of both time and dilution in the 
coefficient, was found bj^ the American investigators too long and 
tedious, with the result that they took two and a half and fifteen 
minutes as the requisite figures. In addition, the time allowed bj' 
the Lancet method for moculation — viz., everj- twelve and a half 
seconds for half an hour — makes the test somewhat formidable. 
The advantages accruing from the determination of the t^o and a 
half and fifteen minutes figures have to be set off against the in- 
creased amount of work to tip off the low carbolic acid controls 
in the right place, and for any test devised for practical and not onl}- 
for research work this latter item is of great significance. 

Quantity of Beoth Culture added to Disinfectant. 

Solutions. — In both the Lancet and Hj^gienic Laboratory tests 
the feeling has been expressed that the original method of adding 
5 drops to 5 c.c, and subsequent subculturing bj* means of a 
standard loop, was some^vhat lacking in scientific accuracy, and 
that it Mould be more scientific to add either : 

(1) 0-1 c.c. from a pipette to 5 c.c. of dismfectant solution, as 
in the Hygienic Laboratory method, subculturing by means of a 
standard loop ; or 

(2) A standard amount from a platinum spoon of fixed capacity, 
originally stated as 0'08 c.c., but subsequently found to be between 
0-10 and 0-15 c.c, to 5 c.c. of disinfectant solution, and subculturing 
also by means of a spoon. 



292 DISINFECTION AND STERILIZATION 

The use of a spoon for subculturing has the disadvantage of 
carrying over the disinfectant into the subculture medium, and 
acts as an inhibitor, a criticism which has been raised against the 
loop method with its much smaller cajDacity. 

The authors have carried out several experiments on the com- 
jjarison between the drop method and the 0-1 c.c. method, and 
have found that — 

(1) With jjhenol and an emulsified disinfectant of C.A./E.W. 18 
no difference in the time rec^uired to ensure death of the organisms 
could be found if 5, 6, 7, or even more drops were added. 

(2) With potassium permanganate in dilute solutions 1 in 4,200 
to 1 in 4,500 an effect was only produced when 7 drops were added 
instead of 5, the permanganate apparently being taken uja by 
the extra amount of organic matter jDresent. 

This permits an error of 2 in 5, or nearly 50 per cent, in drop 
measurement. Further 5 drops delivered from this actual pipette 
were equivalent to 0-27 c.c, and the error in dropping was a very 
small one. This point, it appears, is not of great significance. 

The Standard Bacteriological Test (Rideal-Walker Method), 
adopted by all members of the British Disinfectant Manufacturers' 
Association, is as follows : 

" The coefficient values of all disinfectant fluids manufactured 
by . . . are determined in the following manner : 

Shake the bottle or other vessel containing the disinfectant 
well before proceeding to make the dilution. Make a 1 per cent, 
stock emulsion (5 c.c. of disinfectant added to 495 c.c. of boiled 
distilled water of 15° to 80° C). From this stock emulsion prepare 
required dilutions in boiled distilled water, taking care that pipettes 
used for preparing stock emulsion as well as dilutions are, after 
emptying, always well washed out with and into the diluent, and 
that all dilutions, including stock emulsion, are well shaken before 
use. To 5 c.c. of a particular dilution add 0-2 c.c. (5 drops) of a 
broth culture of B. fifphosus grown for twenty-four hours at 37° C. 
Shake immediately after medication. Keep medicated tubes at 
temperature of 15° to 18° C, and take subcultures into 5 c.c. broth 
every two and a half minutes up to ten minutes. Incubate for 
at least forty-eight hours at 37° C.^ 

Use as a stock organism B. typhosus from a single colony on 
an agar plate culture that has been gro^\Ti at 21° to 22° C. from tAvo 
to seven days, and removed by weekly transference for several 
uninterrupted generations from the original source (the human 
body). 

Owing to the extremely important influence which the broth 
1 Rideal and Walker, J. Soc. Ind., October, 1903, p. 424. 



METHODS OF ANALYSIS 293 

has on the characteristics of the B. typhosus employed as the test 
organism in the Rideal-Walker test, particularly as regards the 
peptone, attention is clra-Rii to the fact that this is prepared accord- 
ing to the following modification of the formula of Dr. S. Rideal •} 

"Lemco." 20 grammes; peptone,- 20 grammes; sodium chloride, 
10 grammes; -water to 1 litre. Boil the mixture for thirtj- minutes^ 
neutralize with normal caustic soda (phenolphthalein indicator), 
add 15 c.c. of normal hydrochloric acid, make up to 1 litre with 
distilled Avater, filter, and finally sterilize. 

The culture employed must conform with the requirements 
laid down by the authors of the test" — viz., " life in two and a half 
and five mmutes, and no life thereafter," -uith "phenol dilutions 
not higher than 1 to 110 or lower than 1 to 90." 

It has long been the hope of the authors that a standard test 
for dismfectants should be devised varying onh* in temperature 
of operation for temperate, subtropical, and tropical use, and it 
appears likely that such a test will conform to the general end- 
point method developed in the Rideal-Walker. The following 
points, however, are those on which agreement is by no means 
universal, and on which much further information is urgently 
needed before such a test can become actually operative : 

The Stability of the Grermicide. — It is well known that with the 
emulsified tar acid disinfectants the enhancement of germicidal 
activity with the dispersity of the emulsion is by no means incon- 
siderable, and the aim of manufacturers is to produce a fine emulsion. 
Such emulsions are, however, not always stable, and may actually 
separate into two distinct layers after a short period of standing 
either in cask before dilution or after making up for actual use. 
Again, although emulsoids are not very sensitive to electrolytes, 
when they are unstable electrolytes accelerate de-emulsifi cation — 
e.g., dilution with sea- water or hard water. 

A stability- test is thus necessary to ensure the uniformity of 
germicidal action Avith these emulsified disinfectants. 

The Presence of Organic Matter. — The various types of organic 
matter which have been added to test the germicidal activitj^ of 
germicides, such as milk, blood, blood-serum, dried fseces. all suffer 
from the disadvantage of lack of uniformity. Many disinfectants, 
especially those of the oxidizing class — e.g., potassium perman- 
ganate, the halogens, ozone, and the like — suffer a remarkable 
diminution in germicidal activity. In the presence of easily 

^ Fourteenth International Congress for Hygiene and Demography. Berlin, 
1907. - Allen and Hanbury's " Eupepton." 

^ Vide Lancet, September 25, 1015, p. 717. 



294 DISINFECTION AND STERILIZATION 

oxidizable organic matter, the protein coagulating disinfectants, 
such as the salts of the heavy metals, are precipitated by non- 
living proteins, whilst the emulsified tar acids are absorbed by 
colloidal and discrete material particles. It is thus clear that the 
utilization of any particular type of organic material may un- 
favourably affect certam germicides and leave others unaffected. 

If organic matter is to be added, it should embrace all these 
various factors — i.e., it should be uniform in composition,, capable 
of oxidation, of coagulation, and exhibitive of the phenomenon of 
absorption. Such a material may possibly be fomid in the syn- 
thetic pol^Tpeptides, where in derivatives with a high molecular 
weight colloidal solutions are readily obtained. 

The Choice of Organism. — ^It is well known that many different 
strains of B. typhosus exist of appreciably different resistances 
to phenol, and that this resistance to other disinfectants does not 
var}^ jjro rata ; in fact, micro-organisms can by careful cultivation 
be immunized to quite strong solutions of any particular germicide. 
For this reason the limits or variation have been embraced in the 
modern tests. This point is of extreme importance in the case of 
the germicides of high R.W. figure, since the discrepancies obtained 
with different organisms are more serious. The ease with which 
organisms can be gro^^ai on agar and sent by post suggests the 
universal use of one organism — e.g., B. typhosus (Jolms Hopkins) 
or B. typhosus (Rawlings). Both these organisms fall within the 
limits suggested by the test, provided that continuity and regularity 
in subculturing is maintained. It would appear inadvisable at 
the. present to place closer limits on the phenol control, since the 
seasonal variation in the resistance of the organism appears to be a 
difficult factor to eliminate. 

The Choice of Culture Medium. — All the constituents of the 
culture medium — the " Lemco," peptone, and salt — have from time 
to time received their fair share of criticism, and it is certain that 
neither the original R.W. nor the Hygienic Laboratory broth is 
sufficienth' uniform when made up by different investigators to 
give reproducible results, even with a limitation of the phenol 
control periods for the organism as stipulated in the present-day 
test. From time to time the writers have endeavoured to obtain a 
uniform "Lemco," since it is well known that the " Lemco " itself, 
although more jierfect than any other nutrient medium proposed 
— e.g., blood or bullock's heart broth — is subject to variations both 
in inorganic salts, but more especially in extractives which affect 
the R.W. figure. Wright^ suggests that the cause of variation 
1 ./. Bacterid., 1917, 2, 319. 



METHODS OF ANALYSIS 295 

is due to the partial conversion of the fat glycerides into soaps 
when the media are boiled in alkaline solution. Doubtless, if the 
world's consumption of " Lemco " for bacteriological testing pur- 
poses were even approximately estimated, the " Lemco " Company 
would be prepared to set aside from their different batches material 
conforming to some agreed-upon figure for salts, nitrogen, fat, 
extractives, and hydrogen-ion concentration in a specified dilution 
under a suitable title, such as " ' Lemco ' for Bacteriological 
Purposes." A very small additional charge would cover the 
cost of analytical control and distribution through the larger 
retailers. 

The addition of 10 grammes of sodium chloride has the sole 
advantage of minimizing (see a very comprehensive paper by 
J. H. Wright/ for a verj^ detailed investigation on the problem of 
uniformity in culture media) slight variations in the inorganic 
salt content of broth, the "Lemco," and the peptone. Although 
the growth of the B. typhosus is not very sensitive to slight changes 
in electrolytic concentration, provided that this concentration is 
equal to or somewhat greater than that corresponding to physio- 
logical salt solution, small traces of electroh'tes, on the other hand, 
in an otherwise nearly salt-free medium, do greatly affect the growth 
of the organisms. For the above reason it would appear inad- 
visable to reduce the salinity of the solution down to, and certainly 
not below, that of phj^siological salt solution. The addition of 
salt to the germicidal solution does, however, as has already been 
indicated, frequently alter the germicidal activity; thus in the 
case of phenol the activity is raised, due to an" elevation in the 
chemical potential or activity of the phenol. That this is the true 
cause has been confirmed by ReicheP and Lash Millar. ^ who showed 
that phenol solutions of the same chemical activity, and conse- 
quentty of the same fugacity, as determined by a partitive method, 
were equally germicidal. Similarly, in the case of mercuric chloride 
an increase on the addition of NaCl to the germicide is occasioned 
in spite of the lowering of the Hg" concentration. This is doujbt- 
less in part due to the formation of the complex ion HgCl4, which 
appears to be more basic than Hg", although the unionized salt 
Na2HgCl4 has but slight germicidal activity."* The reaction of the 
medium is, however, a much more important factor. The rate of 
growth oiB. typhosus and of other organisms is very dependent on 
the hydrogen-ion concentration. J. Wright^ found the optimum 
hydrogen-ion concentration for B. typhosus as Ph =6 . . . Ph =7 

1 ./. BucUriol, 1917. 2, 4. - Biochem. Zeii., 1904, 22, 149. 

3 J. Phys. Chem., 1920, 24, .366. » See J. Clark, ,/. Phys. Chan., 1901. 5, 310. 

° Loc. cit. 



296 DISINFECTION AND STERILIZATION 

Schoenholtz and Meyer^ obtained as ojJtimum Pu =6-8 to Ph =7-0, 
variations in generation time being found as follows : 

P„ Generation Time at 30° C. 

5-4 41-3 

70 31-0 

7-8 33-4 

We may, therefore, assume that for uniformity in culture 
medium the h3'drogen-ion concentration should be between the 
limits Ph = 6-5 to Ph =7-0, and preferably the medium should be 
adjusted to a Iwdrogen-ion concentration of Ph=7-0, or that 
obtaining in j^ure water. 

This concentration of hydrogen-ions can be adjusted in the 
medium by the addition of either caustic soda or hydrochloric acid, 
as is necessary, but the variation in hydrogen-ion concentration 
on the addition of alkali or acid to a neutral medium cannot be 
calculated if the solution contains an unknown concentration of 
" buffer " salts. Thus, the methods of preparing media by neutral- 
ization with caustic soda to a phenolphthalein end-point, followed 
by bringing the reaction up to +1-5 Anth hydrochloric acid, is not 
satisfactory, since in the presence of large quantities of buffer salts — 
i.e., the salts of a strong base and weak acids such as are present 
in broth, peptone, and " Lemco " — the hydrogen-ion concentration 
will vary but little. 

The onh" satisfactory method of adjusting the reaction of the 
medium is bj" direct measurement of the hydrogen-ion concentra- 
tion; if a value of Ph=7 be adopted, litmus solution will acquire 
a port-wine colour such as is obtained on the addition of litmus 
solution to water containing a little free carbonic acid.- Alterna- 
tively to colorimetric methods the electrometric hydrogen electrode 
may be employed. For accurate work the hj^clrogen electrode is to 
be recommended, but unless carefully manipulated and frequently 
used, hydrogen electrodes are often a source of much annoyance 
and trouble ; for this reason it would seem preferable to use suitable 
indicators which give a marked colour change in the region Ph=6-8 
to Ph=7, and adjust the reaction of the medium by the addition 
of either acid or alkali, without anj- prior neutralization, until the 
colour change, as determined by the spotting-out method emploj'ing 
a white tile, indicates the correct hydrogen-ion concentration. 
Colorimetric methods are usually reproducible by independent 
observers to \\dthin O-l to 0-15 Ph. 

1 Proc. Soc. Biol. Med., 1919, 16, 151. 

2 For details as to the methods for the determination of the Ph of media, see 
"The Determination of Hydrogen Ions," by W. M. Clark; Williams and Wilkins, 
1920. 



METHODS OF ANALYSIS 297 

The Peptone. — The original peptone suggested for the R.W. 
test was Witte's. This was employed for the simple reason that 
the manufacturers of this material have succeeded in producing a 
very uniform product. During the period of the war and sub- 
sequently home manufacturers have devoted more attention to 
the production of a uniform peptone. The Digestive Ferments 
Company in America and Allen and Hanbury in this country have 
succeeded in producing peptones which appear to be uniform in 
composition. The work in our OA\'n and in the Lederle Labora- 
tories, New York, has conclusively shoMH that the hydrogen-ion 
concentration or the amount of buffer salts in a "Lemco " peptone 
broth is not the only controlling factor in the growth oiB. typhosus, 
since certain peptones possess more easily assimilable foodstufl's 
than others, resulting in a luxuriant growth at identical hydrogen- 
ion concentrations. It would therefore appear probable that 
some proprietary peptone on the market would have to be incor- 
porated in an international test. 

The Reaction Kinetics and Disinfection. 

The various drop methods, as well as the original thread method, 
of testing disinfectants are end-point tests, in so much as they give 
but an indirect method of determining exactly the rate of germicidal 
action. The garnet method of Ea-onig and Paul is thus a superior 
method of studying the reaction kinetics of disinfection, although 
it mil be evident that by utilizing numerous short time mtervals 
in any of the drop methods the variation in rate with the time may 
be approximated to. 

The rate of disinfection was first examined in detail by Kronig 
and PauP by the simple immersion of anthrax-loaded garnets in 
the disinfectant, and counting by subsequent incubation the number 
left alive after different intervals of time. The rate of disinfection 
or the rate of death at any time is proportional to the mumber 
left alive at that time and to the strength of the disinfectant, or 

where c is the concentration of active germicide, ?z. the number of 
micro-organisms alive at time t. 

On integration this expression becomes : 

. lOQe '^, 

h ~ ^0 *^i 

where n^ and n^ are the number of organisms alive at times t^ and 
t^ respectivel}-. 

1 Zeitsch. Hyg., 1907, 25, 2C. 



298 



DISINFECTION AND STERILIZATION 



Similar results have been obtained for various organisms with 
different types of germicides by Chick,^ Lane Claypon,- Bronny and 
Gelmour,^ Watson.* Churchmore,'^ and especially by Lee and Gilbert.® 

As typical of the results obtained in this way may be quoted 
the folloAving : 

Observers, Kronig and Paul.^ 
Organism, anthrax spores. 
Disinfectant, 0-11 per cent. HgClg. 
Temperature, 18° C. 



Time in Minutes. 


N (Surviving). 




10= <o 


2027 = No 




15 


(172 


0-096 


20 


.-)64 


0-056 


25 


382 


0-048 


30 


251 


0-045 


35 


179 


0-042 


40 


138 


0-039 


45 


101 


0-037 


50 


80 


0-035 


60 


39 


0-034 


70 


6 


0-042 


80 


3 


(V040 



Observer, Chick.* 
Organism, B. typhosus. 
Disinfectant, 0-6 per cent, phenol. 
Temperature, 20° C. 



Time in Minutes. 


iV {Surviving). 


K. 


(i-r,= ^o 


231-3 


__ 


1-5 


190-0 


0-085 


2-6 


167-0 


0-067 


4-6 


119-2 


0-075 


6-6 


77-8 


0-077 


10-5 


31-6 


0-086 


15-0 


11-3 


0-090 


20-0 


2-4 


0-102 


300 


35 


0096 



Lee and Gilbert obtained the following values for the reaction 
velocity constants with a number of micro-organisms: 



1 J. Hyg., 1910, 10, 237. 

3 J. Path. Bad., 1913, 18, 144. 

6 J. Exp. Med., 1913, 16, 221, 822. 

7 Zeilsch. Hyg., 1897, 25. 26. 



Ibid., 1909, 9, 239. 

J. Hyg., 1910, 10, 237. 

J. Phys. Chem., 1918, 12, 348. 

./. Hyg., 1910, 10, 237. 



METHODS OF ANALYSIS 



299 



Organism. 



B. typhosus . . 
Anthrax spores 
Staph, pyog. aureus 
B. coli coimmniis . . 



Disinfectant. 



Temperature. 



K. 



0'2 per cent. ] henol 
0*1 per cent HgCl2 
0*2 per cent phenol 
Electric lamp ex- 
posure (100 watts) 



37-5° C. 
20 0° C. 
00° C. 



0-067 -0-056 
0-057 -0-043 
0-0146 - 0-0132 

0-021 -0-013 



The time required for complete disinfection was also determined 
by these latter observers. These data are usually obtained in the 
usual end-point methods already described. 

In the case of phenol w-ith B. typhosus at 37-5° C. and Staph, 
pyog. aureus at 20° C. the following figures were obtained: 





T {for Complete Disinfection) Minutes. 


Percentage Phenol. 










B. typhosus. 


Staph, pyog. aureus. 


1-5 


4 





1-3 


9-5 


— 


1-2 


— 


7 


1-0 


25 


26 


0-9 


50 


— 


0-8 


— 


100 


0-7 


155 


— 


0-6 


300 


400 


0-5 


— 


1,200 



It is well known that an increase of temperature greatlj- aug- 
ments the velocity of disinfection. For most measurable chemical 
reactions the temperature coefficient of the velocity constant is 
ca 2 to 4 for a rise of 10° C. The same holds good for many disin- 
fectants — e.g., HgClo and AgXOg; for phenol and the emulsified 
disinfectants the reaction velocity temperature coefficient is much 
higher ; thus Lee and Gilbert found the follo"uing values : 



Organism. 


Disinfectant. 


Temperature Coefjicient of 
Reaction Velocity. 


B. typhosus . . . . O-Ol per cent HgClg 
,, . . . . 0-6 per cent, phenol 


3-0 
7-5 



Watson, Lee, and Gilbert^ have attempted to find out the number 
of molecules reacting with each organism by determining the time 
necessary for complete disinfection with various concentrations 

^ Loc. cit. 



300 DISINFECTION AND STERILIZATION 

of disinfectants. If this latter be in large excess Watson found that 
n log C +G<= constant, where n is the number of molecules reacting 
with a micro-organism at anj^ instant; for Stajyh. pyog. aureus 
n = 5-5, for anthrax spores and HgCU w = 4-9, ^^'ith B. 'paratypliosus 
71=3-8. For B. typhosus and phenol w=6. Thus one micro- 
organism requires from 3-8 to 6 molecules of dismfectant for de- 
struction. Attempts have likewise been made in the case of ionized 
disinfectants to determine the number of ions reacting with each 
micro-organism. Experiments with the heavj^ metallic ions, such 
as copper, silver, and mercury, which react with proteins, can 
easily be made by either electrical concluctivitj' or preferablj" bj' 
potentiometric methods,^ but it remains to be proved how many 
ions are actually required to produce death. 

We have already indicated that the mechanism of disinfection 
is relatively" complicated, and that the rate of disinfection foUows 
approximately a monomolecular reaction when the disinfectant is 
in large excess. As a result of these experiments, numerous experi- 
menters have been led to the conclusion that the micro-organism, 
can be regarded as a simple molecular species, and that disinfection 
is a simple chemical process. This is certainty not the case, as 
diffusion and osmosis, as well as phenomena such as reversible 
and irreversible chemical coagulation, play an important part in 
the operation. These actions are not the same as a purety chemical 
reaction, although due to the same chemical and electrical forces. 

They do, however, follow the same mathematical law — viz., ^=Kn 

as a monomolecular reaction. As instances where the same law 
holds approximately for widely diverse phenomena may be men- 
tioned the rate of unrestricted growth of bacteria,- the adsorjotion 
of acids by wool,^ the rates of solution of substances in water 
(diffusion) and also in acids,* the rate of precipitation of solids 
from solids,^ and the rate of evolution of gases from liquids.^ 

It is thus evident that to obtain a satisfactory monomo- 
lecular reaction curve (which incidentally was not obtained with 
0'6 per cent, phenol at 20° C. on 8. pyog. aureus, when for 
the first four minutes a constant surface diffusion expression 

1 See La Franca, Zeitsch. Physikal. Chem., 1906, 48, 481 . 

2 Lane Claypon, J. Hyg., 1909, 9, 239 ; Penfold and Morris, ibid., 1913, 12, 527; 
Slater, Biochem. J., 1913, 7, 197. 

3 See Diett. Monatsh., 1914, 35, 787. 

* See Noyes and Whitney, Zeitsch. Physikal. Chem., 1897, 23, 689; Bruner, 
ibid.. 1900, 35, 283; Zeit.sch. Anorg Chem., 1901, 28, 314; 1903, 35, 23; 1903, 
37, 455. 

5 Langley, Chem. Soc. Trans., 1884, 45, 633. 

8 Penman, ibid., 1898, 73, 515; 1903, 83, 1168. 



METHODS OF .ANALYSIS 301 

-n=K was obtained by Lee and Gilbert) does not necessarily 

indicate that the progress of the reaction actually measured was a 
chemical reaction, although, as has already been indicated, death 
is due in the ultimate analysis to a problem in chemistry. 



BIBLIOGRAPHY. 

Rideal-Walker Test. 

Walker: The Practitioner, 1902, 79, No. 413. 

RiDEAL and Walker: J. Royal San. Inst., 1903, 24. 

SoMMERViLLE and Walker: Public Health, March, 190G. 

SoMMERViLLE and Walker: Sanitary Record, November 29, 1906. 

RiDEAL and Walker: Brit. Med. J., April 6, 1907. 

SoMMERViLLE and Walker: Sanitary Record, May 9, 1907. 

RiDEAL: Fourteenth International Congress for Hygiene and Demography, Berlin 

September 23, 1907. 
Partridge: The Bacteriological Examination of Disinfectants, 1907. 
SOMMERVILLE and Walker: Sanitary Record, March 26, 1908. 
Rideal: J. Trop. Jlcd. Hyg., May 1, 1908. 
RiDEAL and Walker: Lancet, September 19, 1908. 
Hewlett: Lancet, March 13, 20, 27, 1909. 
Rideal and Orchard: Medical Officer, June 26, 1909. 
RiDEAL: Lancet, December 18, 1909. 

Hewlett: Trans. British Pharmaceutical Conference, Cambridge, July. 1910. 
SOMMERVILLE: Trans. British Pharmaceutical Conference, Cambridge, July, 1910. 
Walker and Weiss: J. FranMin Inst., July, 1912. 
SOMMERVILLE: 21 ed. Times, October, 1912. 
Walker: N.Y. Med. J., February 1, 1913. 
RiDEAL and Walker: Amer. J. Pub. Health, 3, No. 6, 575. 
Weiss, J. M. : J. FranUin Inst., December, 1912, 683. 
Sevis Woodhead and Ponder: Lancet, November, 1907. 
Rideal and Walker: Lancet, September, 1915, 717. 
W^RIGHT, J. H.: J. Bad., 1917, 2, 4, 319. 

Shoenholtz and Meyer: Proc. Soc. Biol. Med., 1919, 16, 151. 
Lash Millar: J. Phys. Chetn., 1920. 24, 566. 



SUBJECT INDEX 



ACETALDEHVDE, 221 

Acetic acid, 86, 176, 191, 213, 214 
Aceto-acetic acid, 216 
Acetoform, 276 
Acetone, 172, 217 

chloroform, 221 
Acetozone, 216 
Acetyl coumaric acid, 246 

peroxide, 216 
Acetyozone, 240 

Acids, antibacterial action of, 86 
Acridine, 226, 259 

dyes, 259 
Acrolein, 221 
Actol, 209, 275 
Adsorption, 184-188 
Agglutination, 183, 184, 258 
Agroferment, 169, 206 
Air, 3, 9 
Airoform, 278 
Airol, 278 
Alacet,214 
Albargin, 206 
Alcohols, 216 
Aldehydes, 218 
ALformant lamp, 16 
Alformin. 276, 277 
Alga}, 206, 216, 222 
Aliphatic acids, 213-216 
Alkaloids, 187 
Alkazal, 277 
AUyl alcohol, 217 

isothiocyanat e , 218 
Aljihogen, 216 
Alphol, 254 
Alphozone, 216 
Alsol, 209, 276 
Alum, 5, 49, 62 
Aluminium, 2i)6 

ions, 183 

salts, 173, 270-277 
Alumino-ferric, 62 
Aluminol, 254, 276 
Amides, 226 
Amidoacetal, 221 
Amines, 221 

Amino-benzene derivatives, 250 
Ammonia, 86, 162, 173, 192, 205 
Ammonium duoride, 203 
Amyl alcohol, 217 
Amyhimine, 222 
Analutos, 243 



Aniline, 172, 192, 226, 250 

blue, 258 
Animals, 1, 30, 150 
Anisic acid, 245 
Anthracene, 169, 175, 177, 226 
Anthrax, 17, 21, 25, 42, 45, 74, 147, 
185, 197, 202, 204, 211, 229, 241, 
245, 253, 256, 260, 262, 270, 298 
Antiluetin, 278 
Antimony atoxyl, 277 
colloidal, 211 
inorganic compoimds, 211 
organic compounds, 277. 278 
Antinonnm, 250 
Antisepsin, 244 
Antiseptic, 2 
Antitoxin, 7, 183, 209 
Aphidol, 273 
Aphis, 162 
Argentamine, 275 
Argentide, 209 
Argentol, 275 
Argonine, 275, 276 
Argyrol. 275, 276 
Aristol, 249 
Aromadendi'al, 262 
Aromatic acids, 237 
Aromatics, 5 
Arrhenal, 268 
Arsacetm, 277 
Arsalyt, 270 
Arsenates, 210, 211 
Arsenic. 146, 159 
colloidal, 206 
Arsenicals, organic, 267, 268-272, 276 

Arsenites, 165, 171, 210 

Arsenophenyl, 271 

Arsine, 210 

Aseptine, 49 

Aseptol, 247, 275 

Asiphyl, 271 

Aspaprol, 254 

Aspartic acid, 216 

Asurol, 274 

Atoxyl, 269 

Atrastol, 254 

Atryosyl, 271 

Auramines, 258 

Aurocantan, 276 

Autol, 277 

Auxochromic grou^js, 257 

Azoic acid, 260 



303 



304 



DISINFECTION AND STERILIZATION 



Bacillus aerogenes capsulatus, 132 
amylobacter, 162 

coli communis, 12, 16, 26, 45, 56, 
70, 87, 116, 204, 206, 209, 211, 
214, 252, 256, 259, 288, 290 
enteritidis sjiorogenes, 132 
melanogena, 162 
mycoides, 258 

pyocvaneus, 185, 244, 245, 252, 255 
subtilis, 17, 26, 45, 74, 197, 210, 
215, 231, 258 
Bacon, 41, 50 
Balsam, 237, 245 
Banding trees, 159 
Bellite, 172 
Benzaldehyde, 239 
Benzanilide, 240 
Benzene, 165, 179, 202, 225 
Benzo-cresol, 240 
Benzoic acid, 56, 214, 237, 238, 239, 

244 
Benzo-naphthol, 240 
Benzosol, 232, 240 
Benzoyl-acetyl peroxide, 216, 240 
Betol, 243, 254 
Bicalzit, 77 
Bilharzia, 257 
Biltong, 4 
Biogen, 198 
Biomal, 278 
Bismona, 211 
Bismuth, inorganic compounds, 211 

organic compounds, 278 
Bismutose, 211, 278 
Bisulphates, 199 
Blankets, 24, 99 
Blaze currents, 165 
Bleaching powder, 80, 200, 201 
Blight, 162 
Blood corpuscles, 185 

medium, 295 
Blowflies, 143 
Bluestone, 163 
Books, 18, 98, 101 
Boral, 277 
Borax, 204, 252 
Bordeaux mixture, 159, 161, 162, 163, 

208 
Boric acid, 5, 49, 52, 86, 202, 204, 210, 

213 
Borofluorides, 203 
Borol, 276 
Borosalicylates, 242 
Breweries, 35 
Brilliant green, 257, 259 
Brine, 170, 205 
Bromamines, 252 
Bromates, 202 
Bromcresols, 248 
Bromine, 79, 85, 202 
Bromoform, 222 
Bromol, 248 
Bromphenols, 248 



Bromxylenols, 248 
Broth, standard, 282, 283 
Bro^vn rot, 163 
Buffer salts. 296, 297 
Bunt, 163, 164 
Burgmidy mixture, 162 
Butyl alcohol, 217 
Butyric acid, 215 

Cacodyl derivatives, 268 
Calcium ions, 203, 205, 215 

peroxide, 77 
Calizibram, 233 
Camphor, 262, 263 
Camphortar, 262 
Canker, 162 
Canned food, 36, 42 
Canning processes, 43 
Carbazole, 226 
Carbohydrates, 183 
Carbolates, 226 
Carbolic acid, 86, 96, 163, 244 

control, 226-228, 282, 286 

paper, 42 

soaps, 117 
Carbon, 179 , 

disulphide, 154, 165, 199 
Carbonates, 205 
Carbonic acid, 204 
Catechol, 231 
Cavities of the body, 121 
Charcoal, 2, 120, 185, 206 
Charlock, 165 
Charqui, 4 
Chavosot, 237 
Cheese, 46, 58 
Chmosol, 256, 261 
Chitin, 183 
Chlamydomucor, 47 
Chloracetic acid, 181, 191 
Chloral hydrate, 221 
Chloralum, 209 

Chloramines, 82, 200, 201, 251, 252 
Chlorazine, 252 
Chlorcasane, 252 
Chloride of lime, 80, 200, 201 

of magnesia, 201 

of soda, 201 
Chlorine, 27, 79, 82, 97, 200 

peroxide, 84 
Chloroform, 165, 222 
Chlorophenols, 247 
Chloropicrin, 164, 200 
Chloroproteins, 200 
Chloros, 81 

Cholera, 12, 18, 64, 71, 74 
Choleval, 275 
Chromic acid, 211 
Chromophoric groups, 257, 258 
Chromosomes, 183 
Chromospores, 183 
Chrysoidin, 258 
Cineole, 237, 262 



SUBJECT INDEX 



305 



Cinnamein, 245 

Cinnamic acid, 245 

Citrates, 209 

Citric acid, 215, 216 

Cladosporium herbarum, 47 

Cladotrychium graminis, 163 

Clothes, 24, 95, 98, 121 

Coagulation, 168, 169, 174, 200, 208, 

209, 216, 241, 294 
Coal tar, 173, 175, 176, 178 
Coke-oven tar, 178 
Cold, preservation by, 45, 51, 55 
CoUargol, 206, 276 
CoUoidal metals, 207, 272, 275 

systems, 183 
Collusol, 133 
Condensed milk, 56 
Condy's fluid, 94, 210 
Copper, 4, 36, 88, 173, 206 
carbolate, 169 
oleate, 215 

organic compounds, 276 
salts, 172 
sucrate, 162 

sulphate, 88, 161, 163, 165, 170, 
173 

Copperas, 162 

Copperized oil, 176 
Corrosive sublimate, 173, 208 

Cream, 53 

Creatin, 222 

Creosote, 178-180, 244 

Cresegal, 274 

Cresin, 247 

Cresochin, 261 

Cresols, 170, 175, 233, 234, 235, 247, 
281 

Cresotinic acid, 245 

Cresylic soaps, 117 

Cresyl salicylates, 243 

Crurin, 278 

Crysolgan, 276 

Culture medium, 290, 291 

Cumenol, 235 

Cupragol, 276 

Cuprase, 206 

Cupratin, 276 

Cuprein, 261 

Cupriase, 206 

Cupriaseptol, 276 

Cuprol, 276 

Cuprous chloride, 85 

Cyanin, 258 

Cyanogen, 204, 211 

Cvclohexane, 165 

Cyllin, 163 

Cysticerci, 47 

Dahlia blue, 258 
Dakin's solution, 82 
Danysz virus, 140 
Deodorant, 2 
Dermatol, 278 



Dermogen, 198 
Desiccation, 3, 4 
Desichthol, 279 
Diaptherin, 261 
Diazo dyes, 258 
Dichloramines, 252 
Dinitrophenol, 172 
Diphenylmethane dyes, 257 
Diphtheria, 1, 7, 14, 16, 18, 261 
Disinfectant, 2 
Dithio-salicylates, 246 
Dressings, antiseptic, 123 
Dropping pipette, 284, 292 
Dry-salting, 41 
Duotal, 232, 233 
Dyestuffs, 189, 257 
Dysentery, 88 

Ectogan, 108, 198 

Eggs, 38, 46 

Elaidic acid, 215 

Elarson, 270 

Electric charge, 184, 187 

Electrometric titration, 296 

Emetine, 261 

Emulsions, 183, 236, 262 

Emulsoids, 293 

Enesol, 271 

Enzymes, 183, 197, 237 

Eosin, 259 

Eosolate, 275 

Epicarin, 254 

Erysipelas, 270 

Essential oils, 5, 33, 118, 138, 261, 

263 
Esters, 217, 247 
Ethyl acetate, 217 

alcohol, 165, 216, 217 

ether, 165, 186 
Ethylenediamine, 221 
Eucalyptol, 237, 244, 252, 261 
Euchmin, 260 
Eucol, 232 
Eugoform, 233 
Euphorin, 250 
Euresol, 231 
Eurodin, 259 
Europhen, 249 
Eutypellaprunastri, 163 
Excreta, 95, 191 
Eye, infections of, 275 

Fats, 111 

Favus, 151 

Ferrichthol, 279 

Ferrous sulphate, 162, 163, 165 

Filters, air, 11 

candle, 65 

mechanical, 64 

sand, 63 
Fish, 5, 39, 40, 48 
Flavine, 259 
Fleas, 144, 150 

20 



306 



DISINFECTION AND STERILIZATION 



Flics, 30, 139 
Fluorescein, 259 
Fluorescent substances, 259 
Fluorides, 86, 113, 170-172, 176, 203, 

209,211, 238 
Fluorine, organic compounds, 248 
Food, 4, 36 

Formaldehyde, 3, 11, 52, 59, 148, 172, 
177, 214, 215, 218, 219, 233 
compounds, 220, 221 
Formalin. U, 164,218,219 
Formic acid, 86, 187, 213, 214 
Formochloral, 14 
Fructol, 214 
Fruit, 38, 51 
Fugacity, 295 
Fumaric acid. 216 
Fungicides, 161-163, 176, 191, 200 
Furniture, 94 

Gallic acid, 246 
Gallotannic acid, 246 
Gangrene, 132 
Gargles. 122 
Garnet test, 281,297 
Gas lime, 153 

masks, 185 

tar, 176, 178 
Gastrotan, 278 
Gelatine, 185 
Gentian violet, 258 
Geosote, 215 
Germicidal activity, 185 
Glanders, 273 
Gluside, 239 
Glycerol, 217, 244 
Glycoformal, 21 
Glycosal, 243 
Glycozone, 197 
Gold, colloidal, 207 

compounds, 276 
Goulard's extract, 108 
Guaiacetin, 233 
Guaiacol, 232, 233 
Guaiacyl, 233 
Guaianin, 232 
Guaiasanol, 232 
Guanazols, 259 
Guanidine, 222 

Hair, 148 
Halazonc, 251,252 
Halide acids, 204 
Halogen naphthols, 254, 255 
Halogens, 200, 293 
Hands, 106, 133 
Heat, 10, 42, 65, 199 
Hegonon, 275 
Hektargyr. 269 
Helcosoi, 278 
Heptylamine, 222 
Hermite tiuid, 81 
Hermophenyl, 273 



fletocresol, 245 

Hetoform, 278 

Hexamethylenetetramine, 219 

Hexane, 165 

Hides, 146, 205 

Hiktin, 269 

Holzine, 16 

Homologous phenols, 236 

Hopogen, 198 

Hospitals, 99 

Hydantoin, 222 

Hydrargyrol, 272 

Hydrazine, 192, 200 

Hydrocarbons, 187, 213 

Hydrochloric acid, 86 

Hydrocinnamic acid, 246 

Hydrocuprein, 260, 261 

Hydrocj-anic acid, 155, 204 

Hydrofluoric acid, 192, 203 

Hydroformant lamp, 18 

Hydrogen ion, 165, 183, 191, 199, 205, 

296 
peroxide, 76, 125, 129, 197, 206, 

263 
Hvdroquinines, 261 
Hydroqumone, 188, 231 
Hydroxy benzenes, 230 
Hydroxyl ion, 192, 205 
Hydroxynaphthalenes, 255 
Hvdrozone, 197 
Hyperol, 129 
Hypobromites, 252 
Hypochlorites, 81, 201, 252 

Ibit, 278 
Ice, 45 

cream, 49 
Ichthalbin, 279 
Ichthargon, 275, 279 
Ichthoform, 279 
Ichth3'ol, 218, 260, 279 
Indicators, 296 
Influenza, 7 

Infusoria, 210, 217, 221, 268 
Inhalations, 123 

Injections, antiseptic hjiDodermic, 124 
Inoculating needle, 289 
Internal disinfection, 124 
Intramin. 279 
lodates, 203 
Iodine, 79, 85, 107, 187, 202, 203, 262 

aromatic derivatives, 248-250 

comijounds. 223, 224 

cyanide, 203 

trichloride, 85, 203 
lodoanisol, 249 
lodocatechin, 249 
lodocresols, 248. 249 
Iodoform, 202, 222, 243, 278 
lodoguaiacol, 249 
lodol, 249 

lodophenolijhthalein, 249 
lodoresorcin, 249 



SUBJECT INDEX 



307 



lodoterpin, 249 
lodoybin, 278 
lodylin, 278 
Iron, 206 

compounds, 183, 209 
Isoform, 249 
Isomorphous groups, 190 
Isoquinoline, 255 
Itrol, 209, 275 

Jams, 38 

Kalzen diSuser, 19 
Ketones, 189, 217 
Kharsin, 269 

Lactamin, 279 

Lactic acids, 244 

Lamps, Fliigge's, 18 
formaldehyde, 15 
hydroformant, 18 
mercury, 69 

Lanoform, 120 

Lanolm, 215 

Lard, 57 

Largin, 275, 276 

Laundries, 100 

Laveran, 270 

Lead comiDounds, 169 

Leaf blotch, 161 

Leather, 246 

Lecutyl, 276 

Leprosy, 261 

Letters, 98 

Leuco bases, 257 

Lice, 137, 150 

Light, sterilization by, 2, 68 

Lime, 38. 77, 86, 152 

Linkage influence, 252, 253 

Lipoids, 183 

London purple, 159 

Loops, standard, 287, 291 

Loretin, 249 

Losophan, 249 

Luminal, 130 

Lutol, 276 

Lysargin, 206 

Lysol, 133, 235, 253, 256 

Magnesium peroxide, 77, 198 

sulphate, 131 
Malachite green, 257 
Malaria, 257 
Maleic acid, 215 
Malic acid, 215 
Manganates, 210 
Mange, 151 

Manure, 32, 127, 141, 153 
Marcasol, 279 
Margol, 278 
Martin's vellow, 258 
Mastisol,l33 
Meat, 4, 39, 40 



Meat, frozen, 46 

Meningococci, 257 

Menthol, 261, 263 

Mercaptan, 217 

Mercurial soaps, 115 

Mercurials, organic, 190, 267, 272-275 

Mercuric bromide, 208 

chloride, 97, 171, 174, 187, 208. 
211,257 

cyanide, 208 

iodide, 209, 261 

oleate, 215 
Mercurophen, 274 
Mercury, 206, 207 

complex, 295 

peroxide, 198 

salts, 172 

zinc cyanide, 208 
Meriodm, 272 
Metallic ions, 300 
Methyl alcohol, 216, 217 

guaiacol, 233 

mercaptan, 217 

salicylate, 242 

sulphide, 217 

violet, 258 
Methylamines, 221 
Methylene blue, 257, 258 
Microcidin, 254 
Mildews, 162, 163 
Milk, 39, 53 
Mites, 144, 151 
Monomolecular law, 300 
Monotol, 232 
Morinal, 276 
Mosquitoes, 142 
Moulds, 45, 160, 172, 197, 214 

Naphthalene, 138, 174, 175, 178, 180, 

226 
Naphthol derivatives, 254, 255 
Naphthols, 170, 219, 253 
Narcosis, 186 
Nargol, 275 
Navergan, 275 
Nectria ditissima, 162 
Neosalvarsin, 270 
Neosiode, 249 

Nicotine, 155, 211, 253, 255 
Nitric acid, 86, 192, 198 
Nitro compounds, 171, 250 
Nitronaphthols, 250 
Nitrophenols, 188 
Nitrous acid, 198 
Nosophen, 249 
Nuclear substitution, 252 

Oil of sweet birch, 242 

of wintergreen, 242 
Ointments, 119 
Olefines. 179 
Oleic acid, 215 
Omaral, 275 



308 



DISINFECTION AND STERILIZATION 



Optochin, 260, 261 

Orjianic matter, testing for, 293 

Organisms, choice of, 200 

Organo-metallic compounds, 267 

Orphol, 278 

Orthoforms, 251 

Osmic acid, 211 

Osmosis, 186 

Oxalic acid, 215 

Oxides of nitrogen, 196, 198 

Oxychinaseptol, 261 

Oxygen, 196 

Oxyquinolines, 256 

Oysters, 88 

Ozone, 3, 33, 72, 196, 263, 293 

Ozonic ether, 198 

Palmitates, 215 

Parabismut, 278 

Parabolic, 133 

Paraffin, 175 

Paraform, 16, 219 

Paraformaldehyde, 13, 16 

Parasitrotropic, 194 

Paris green, 159, 211 

Partition coefficient, 186 

Pasteurization, 54, 197 

Pectic acid, 169 

Pemmican, 4 

Penetration power, 173, 175, 201 

Penicillium glaucum, 177, 216 

Peppermint, 261 

Peptones, 296, 297 

Perfumes, 261 

Perhydrit, 129 

Perhydrol, 129 

Permanganates, 210, 293 

Pcronospora viticola, 162 

Peroxides, 76, 197, 198, 216 

Personal disinfection, 106 

Persulphates, 199 

Petroleum, 169, 170 

Petrols, 213 

Phenacetin, 251 

Phenegol, 274 

Phenol, 226-229 

Phenoloids, 169, 174, 179, 234, 235, 236 

Phenols, 236, 237, 281, 286, 294, 295 

Phenosalyl, 244 

Phenoxyacetic acid, 244 

Phenylacetic acid, 244 

Phloroglucin, 188 

Phosphatol, 232 

Phosphin, 259 

Pht!ialeins, 259 

Phylloxera, 200 

Phytophthora infestans, 162 

Pickling, 41 

Picolin derivatives, 256 

Pikrol, 249 

Pinacone, 217 

Pineae, 262 

Pinol, 262 



Piperitone, 262 
Pitch, 177 
Plague, 1, 7, 26, 93 
Plant pests, 152 
Plasmolysis, 165, 185 
Pneumococci, 255, 257, 260, 270 
Polypeptides, 183 
Polystictus versicolor, 176 
Potassium permanganate, 71, 104, 131, 
210, 293 

sulphate, 173 

sulphide, 161 
Potato disease, 162 
Preservatives in food, 49 
Propionic acid, 215 
Propyl alcohol, 217 
Protargol, 275, 276 
Protectyl, 209 
Proteins, 294 
Protosal, 243 
Protozoa, 165 
Providal, 273 
Providoform, 254 
Puccinia, 163 
Putinol, 279 

Pyridine derivatives, 179, 255, 256 
Pyrogallol, 188, 231 
Pyroletannin, 258 
Pyroligneous acid, 215 
Pyrozone, 197 
Pyrrole, 226 

Quarantine, 6 
Quicklime, 161-163, 205 
Quinine compounds, 260 
Quinoline compounds, 226, 255, 256, 
261 

Rats, 140, 145 
Reaction kinetics, 297 
Refrigerators, 35 
Refuse, 139 
Resadol, 244 
Resin, 177, 181, 225 
Resorcinol, 188, 230 
Ringworm, 139 
Roads, 103 
Rooms, 13, 92 
Rosaniline dyes, 258 
Rust, 163 

Saccharine, 171, 239 

Safranin, 259 

Salacetol, 243 

Salbromanilide, 243 

Salicylates, 242 

Salicylic acid, 209, 214, 240, 241, 255 

Salipyrin, 243 

Salol, 242, 243 

Salophen, 243 

Salt, 4, 40, 56, 153 

Salting, 40 

Saltpetre, 4 



SUBJECT INDEX 



309 



Salufer, IKi 

Salumin, 277 

Saluper. 203 

Salvarsan, 130, 270. 27G, 27?^. 27!i 

Sand filtration, 63 

Sanitas, 197, 263 

Sanocent, 262 

Sanoform, 24!1 

Savonal, 110 

Scabies, 254 

Seed sterilization, 163 

Selective action, 182 

Selenium compounds, 277 

Sera, 183, 186 

Sesquiterpene, 262 

Sheep dips, 145 

Ships. 24, 35, 103 

Silberol, 275 

Silicates, 168 

Silver, 87, 206, 207 

organic compounds, 275. 276 

salts, 209 
Slaughter-houses, 101 
Smoking. 5, 40 
Smut, f63, 164 
Soamin, 268 

Soaps, 108, 225, 248, 2U5 
Sodium bisulphate. 199 

hydrate, 86, 147. 205 

hypochlorite. 130 

perborate, 129 

peroxide, 76, 129, 198 

silicofiuoride, 203 

sulphite, 51 
Soft soap, 163 
Soil sterilizers, 154, 165 
Solarson, 268 
Solveol, 245 
Sophol, 275 
Sorapure, 249 
Sozal, 277 
Sozoiodol, 249 

Spirillocides, 210, 211, 257, 275 
Spirogyra, 216 
Spirosal, 243 
Sprays, 97, 122. 156 
Stability, 293 
Stables, 101, 141 
Standard disinfectant test, 292 
Staphylococcus pyogenes aureus, 12, 16, 
18, 26, 88, 113, 117, 118. 199. 202, 
209, 215, 219, 244, 261, 262, 274, 276, 
299, 300 
Steam disinfectors, 99 
Stibacetin, 277 
Stibnates, 277 
Stibnous acid, 211 
Storax, 245 

Streptococci, 10, 259, 260 
Styracin, 245 
Styracol, 232, 245 
Styrone, 245 
Sublamin, 221 



Sublamine, 209 

Succinic acid, 216 

Succinyl ])eroxide, 216 

Sugar, 171 

Sulfaminol, 279 

Sulphides, 161. 165, 170 

Sulphochloramines, 252 

Sulphonic acids, 246 

Sulphur, 3, 23, 114, 160, 170. 198 
candles, 25 
dioxide, 22, 198, 200 
organic compounds, 279 

Sulphuretted hydrogen. 125 

Sulphuric acid. 86, 125. 163, 172. 199 

Sulphurous acid, 22. > 0. 96. 198, 199 

Surface tension, l!''5-189 

Surgical instruments, 124 

Suspensoids, 183, 184 

Syphilis, 250 

Syrgol, 206 

Tachiol, 88. 209 

Tannal, 278 

Tannin, 173, 181. 246 

Tannismut, 278 

Tanosal, 232 

Tapeworm, 262 

Tar, 171 174, 175, 176, 178, 234, 235 

acids, 178, 179 
Tartaric acid, 86. 215, 216 
Technique of testing. 284, 285 
Tellurium compounds, 277 
Temperature coefficient. 299 
Terbene, 262 
Terpenes. 261-203 
Testing disinfectants, 280-301 
Tetanus, 7, 128, 130 
Tetralin, 254 
Tetrazo colours. 259 
Thiocol, 233 

Thio compounds, 217, 260. 279 
Thiodin, 217 
Thioform, 278 
Thiosinamin, 218 
Thiostibnates, 211 
Thioureas, 279 
Thiozonides, 279 
Thiuret, 279 
Thread test, 225, 280 
Threadworm, 262 
Thymegol, 274 
Thymol, 237, 239, 261 
Tilletia, 163 
Time, influence of, 291 
Tinned food, 36, 42 
Tiodine, 217 
Tobacco, 255 
Tochlorin, 252 
Toluene, 165, 225 
Toluidine blue, 258 
Toluidines, 250 
Tooth powders, 120 
Toxins, 6, 183, 184 



310 



DISINFECTION AND STERILIZATION 



Toxjnien, 274 

Traumatol, 248 

Tribromphenol, 248 

Trichinae, 40, 48 

Tricresols, 235 

Triformol. 219 

Trimethol, 2.37 

Trinitrophenol, 250 

Trioxyinethyleiie, 219 

Triphenylmethane dyes, 257 

Trixidin,2ll 

Trypanosomes, 210, 258, 259, 269, 271 

Trypoflavine, 259 

Tuberculosis, 18, 21, 26, 54, 56, 123, 
202, 245, 250, 254, 255, 257, 268 

Tumonol, 279 
I'lirjH'iitine, 262, 263 

'I'vlinarin, 246 

Typhoid, 7, 12, 16, 18, 45, 72, 74, 78, 
85, 86, 88, 199, 202, 204, 206, 213, 
215, 216. 217, 241, 252, 254, 261, 287, 
288, 290, 292, 296, 297, 300 

Ultramicroscope, 183 
Ultra-violet light, 3, 55, 08 
Upsalan, 273 
Uranyl salts, 173 
Urea, 187, 222 
Uredo, 163 
Urethan?, 222 
Ustilago, 163 

Vaccination, 126 
Valency, 190 
Valeric acid, 215 
Vaporizers, 13 
Vegetables, 51 
Vehicles, 92, 102 
Vermin, 137 
Vesipyrin, 243 



Vinegar, 214 
Vioform, 129 
Viscosity, 176 
Vulcanizing, 169 

Wall papers, 93 
Walls, 94 
Warble tiy, 151 
Washes for plants, 157, 160 
Water, 4, 61 
Waterproofing, 168, 169 
Water sterilization, 65, 68, 71, 194, 2(X), 
251 

sterilizers, 66 
Weed killers, 165 
Weevils, 152 
Werderol, 214 
Wet rot, 162 
Wood preservation, 168-181 

spirit, 216 
Wool, 148 

Worms, intestinal. 4", 137, 151, 262 
Wounds, 108, 127 

Xanthates, 200 
Xanthogenic acids, 218 
Xeroform, 248, 278 
Xylene. 225 
Xylenols, 234 

Yeasts, 214, 218 

Zinc. 114, 206 

chloride, 171-174, 20'J 

riuoride, 171, 172 

oleate, 215 

peroxide, 108, 198 

salts, 172, 176, 177 

tannin, 173 
Zymase, 219 



AUTHOR INDEX 



Abraham, 73 

Adolf, 98 

Allen, 52 

Altmann, 202 

Andeer, 230 

Anderson, 206, 287, 290 

Appert, 42 

Arnould, 25 

Arons, 69 

Aronson, 12, 21 

Arrhenius, 184 

Astruc, 268 

Aufrecht, 209 

Balnes, 206 
Baldas, 112, 215 
Bancroft, 184 
Barton, 80 
Bassett Smith, 206 
Bateman, 172 
Bates, 55 
Baxter, 28, 123 
Bayer, 253 
Beattie, 56 
Beaumartin, 170 
Beaumetz, 25 
Beckhold, 248, 253 
Beckhurtz, 37 
Behring, 211 
Bendon, 259 
Berge, 84 
Bergeron, 242, 246 
Berkeley, 225 
Berthein, 271 
Betzel, 187 
Beyer, 113 
Beyersdorfer, 35 
Binger, 257 
Blake, 190, 204 
Bloxan, 55 
Blum, 12 
Blumenthal, 274 
Blunt, 68 
Blvth, 72 
Bock, 253 
Bogden, 108 
Bokorny, 219, 222 
Bordier, 246 
Bosc, 21 
Bosisto, 111 
Boulton, 174 
Bo vet, 231 



Braithwaite, 85, 202 
Brand, 203 
Brase, 174 
Breslauer, 111, 215 
Brewitt, 108 
Briny, 34 
Brochet, 12 
Brockhart, 107 
Brown, 188 
Browne, 9 
Browning, 259 
Bruhl, 25 
Bub, 171 
Buchanan, 140 
Buchner, 12, 69 
Buckholz, 199, 237 
Budenberg, 44 
Burgess, 72 

Cabot, 176 

Callias, 230 

Calvert, 72, 227 

Cambier, 12 

Carlson, 34 

Cash, 32 

Cassedebat, 25 

Castro, 280 

Catto, 108 

CharitschofE, 177 

Chassevant, 202 

Chassy, 73 

Cheatle, 134 

Cheyne, 132 

Chick, 235, 298 

Christmas, 74, 87 

Chuard, 208 

Clark, 88 

Clarke, 191 

Clayton, 24 

Cohen, 251 

Cohn, 12 

Coisne, 174 

Colin, 204 

Collins, 180 

Conn, 57 

Conrad, 247 

Conradi, 221 

Cooper, 222, 230, 231, 

235, 250, 255 
Courmont, 70 
Croix, 30, 237 
Croner, 20, 77, 214 
311 



Crookes, 228 
Crookshank, 229 
Crozier, 191 
Cruikshank, 27 
Curci, 245 
Curtis, 153 

Dakin, 82, 201, 251. 252 
Danysz, 140, 271, 278 
Darnell, 83 
Dayle, 82 
Dean, 176 
Deditius, 170 
Delbret, 227 
Delepine, 150, 28(1 
Demarquav, 72 
De Vries, 185, 186, 188 
Dieter, 22 
Dieudonne, 69 
Dievert, 206 
Dixon, 22 
Donnan, 184 
Downes, 68 
Downs, 176 
Dresner, 190 
Dubief, 25 
Dufresne, 251 
Duggan, 231, 240 
Dujardin, 25 
Duloroy, 244 
Dunbar, 78 
Duquaire, 123 

EfEendi, 169 

EfiEront, 203 

Egidius, 34 

Ehrlich, 38, 193,248,257, 

259, 267, 278 
Eichengriin, 244, 254 
Einhorn. 232, 287 
Ellis, 169 
Eisner, 107 
Endemann, 50 
Esmarch, 280 
Esten, 141 
Estor, 180 
Evans, 20 

Fabluflowski, 107 
Farrel, 225 
Fehrs, 236 
Feibes, 209 



312 



DISINFECTION AND STERILIZATION 



Finsen, 69 

Fiore, 42 

Firth. 140 

Fischer, 11, 30, 50, 95, 

193 
Fliigge, 9 
Forrest, 178, 179 
Foulerton, 50, 74, 204, 

218 
Fowler, 216 
iM-ank, 86 
Frankel, 244, 280 
Frankland, 9. 20, 02, 77 
Freer, 216 
Frerichs, 238 
Freund, 55, 102 
Freundlich, 184 
Freyringe, 77 
Friedberger, 26S 
Friedenthal, 210 
FroeHch, 73 
Fiihner, 268 
Fuller, 62 

Gage, 88 
Gahn, 49 
Galeotti, 206 
Gegner, 12 
Geppert, 280 
Gerlach, 281 
Geronzi, 219 
Gibbs, 184, 187 
Gilbert, 298 
Gilmour, 259 
Gosse, 187 

Gosselin, 238, 242, 240 
Graham Brown, 238 
Graham Smith, 140 
Graiibe, 110 
Green, 210 
Greig Smith, 262 
Grether, 78 
Groslich, 107 
Grossich, 202 
Gruenert, 56 
Gryns, 186 
Gubler, 246 

Haberkom, 237 
Hailer, 147 
Hall, 180 

Hamburger, 185, 188 
ilaiiiilton, 22 
Haiikin, 71, 210 
Hanna, 46 
Hansen, 107, 217 
Harrington, 51 
Hartmann, 44 
Hauscr, 12 
Heald, 191 
Hedin, 186 
Heider, 98 

Heinz, 198, 232, 2ai, 263 
Helbing, 254 ' 



Henriet, 3 
Hesse, 65 
Hetsch, 77 

Hewlett, 197, 199, 232 
Highet, 135 
Hoffmann, 244 
Hofstiidter, 65 
Horn, 22 

Horrocks, 140, 191, 213 
Horsley, 133 
Hossack, 145 
Houston, 62, 78 
Howard, 169 
Howies, 225 
Hueppe, 246 
Hiigel, 277 

Israel, 206 
Ivanoff, 199 

Jackson, 141 

Jacobi, 258 
Jeannel, 31 
Jensen, 164 
Jepson, 140 
Joachimoglu, 268, 270 
Jolles, 112 
Jones, 147 
Jordan, 34, 215 

Kahlenberg, 191 

Kamer, 278 

Kenwood, 14, 15, 16, 19:), 

232 
Kestel, 210 
Kingzett, 203 
Kirsten, 58 
Kitasato, 86, 145, 191 
Klein, 26, 32, 58, 72, 121, 

198,211,222,228,244, 

256, 280 
Klingraann, 208 
Kobert, 203, 262 
Koch, 25, 72, 111, 123, 

204,211,215,228,280, 

281 
Kohlstein, 147 
Kolmer, 274 
Kraemer, 88, 206 
Kraft, 110 
Kronig, 190, 191, 198, 

203, 208, 281, 297, 

298 
Kronke, 88, 207 
Kruger, 77 
Kyan, 173 

Labbe, 34 
Lambert, 69, 134 
Langmuir. 193 
Lash Millar, 295 
Laubcnhoimer, 247 
Lebbin, 214 
Lee, 298, 299 
Lehmann, 12, 50 



Lenti, 111 

Lenz, 268 

Lepeyrere, 72 

Lereboullet, 71 

Leroux, 227 

Letheby, 27 

Levaditti, 268 

Lewin, 197 

Liborius, 78. 209 

Lichtheim, 230 

Liebreich, 12, 275 

Lilian, 257 

Lingner, 21 

Lister, 228, 229 

Lockemann. 20 

Loeb, 190 

Loew, 11, 192, 210, 217. 

222, 250, 207 
Lowenthal, 243 
Liibbert, 15 
Lucas, 110 

MacDonagh, 279 
Mackenzie, 97, 270 
Madison Cooper, 51 
Malenkovic, 171 
Marcelm, 193 
Marco, 208 
Margosches, 200 
Marmier, 73 
Marsh, 20 
Martin, 25, 235 
Martindale, 209, 238, 240 
Marx, 202 
Mason, 141 
McClintic, 287, 290 
McDougall, 227 
McKendrick, 33 
Mehlhausen, 28, 30 
Meyer, 180, 290 
Michailow, 257 
Miguel, 209. 227 
Miller, 239 
Mihier, 193 
Miquel, 25, 72, 90 
Mohan, 44 
Monziols, 202 
Moore, 200 
Morgan, 222, 230, 231, 

235, 250, 255 
Mosso, 251 
Mouston, 256 
Muller, 110 
MuUer, 261 
Munchmeyer, 34 

Nageli, 206 
Nelson, 170 
Nesfield, 83, 203 
Newstead, 144 
Nicoll, 141 
Nogier, 70 
Norton, 192 
Notter, 106 



AUTHOR INDEX 



313 



Novy, 216 
Nowotny, 171 
NuttaU, 140 

Ogier, 84 
Ohlmuller, 74 
Oliver, 100 
Ormerod, 166 
Ostertas, 47 
Oudin. 34 

Overton, 186, 188, 189, 
192 

Page. 129 

Parkes, 24, 85, 99, 199 

Pasteur. 25, 228 

Paul, liX), 191, 192, 198, 

203, 208, 281, 297, 

298 
Pawlow, 184 
Peiret, 86 
Perier, 242 
Pfhul, 78 
Phelps, 140 
Pickering, 156 
Pictet, 45 
Piefke, 63 
Piorkowski, 245 
Pitchford, 26 
Ponder, 288 
Porter, 107 
Pozen, 22 
Priedel. 248 
Proskauer, 30, 77 

Raal, 259 
Race, 82 
Raizen, 274 
Ransome, 74 
Raschig, 82 
Raspail, 278 
Rayleigh, 193 
Recklinghausen, 70 
Regener, 75 
Reichardt, 27, 32 
Reichel, 295 
Reichenbach, 113, 215 
Reichet, 76 
Reinsch. 63 
Reithoffer, 112 
Reuss, 37 
Richtet, 205 
Rideal, 85, 204, 206 
Ridge, 233 
Riesenfeld, 34 
Ritsert, 57 
Robertson, 98 
Robin, 239 
Roche, 77 
Roepke, 121 
Roger, 94 



Rosenau, 210, 219 
Ross, 139 
Routier, 107 
Roux, 7, 25 
Rowland, 132 
RusseU, 165 

Sage, HI, 178 
Sahli, 240 
Salkowski, 237 
Salter, 219 
Salzwedel, 107 
Savarelli, 25 
Scharff, 71 
Schattenfroh, 147 
Schermg, 254 
Scheurlen, 228 
Schlossmann, 21 
Schneider, 240 
Schoeller, 116 
Scholler, 272, 273, 275 
Schottelius, 6 
Schrauth, 272, 273, 275 
Schroeder, 260 
Schiider, 85, 202 
Schultz, 34 
Schulze, 235 

Schumberg, 85, 202, 208, 
274 

Schwanz, 34 

Scranth. 115 

Sedgwick, 106 

Seidel, 232 

Seligmann, 214 

Senator, 238 

SheiTvood. 77 

Sibut, 244 
■ Siebil, 51 

Siege, 217 

Simon, 109 

Simons, 48 

Sims Woodhead, 288 

Slater, 12 

Smith, 198 

Somermeier, 171 

Sommer, 179 

Sowden, 256 
I Sparks. 45 

Stahl. 12 

Stern, 110 

Sternberg, 25, 28, 31 

280 
Stevens, 191 
StiUing, 258 
Stone, 22 
Stretton, 107 

Tankard, 52 
Taylor, 51 
Teesdale, 175 
Thenard, 34 



Thionot, 26 
Thompson, 113 
Thorner, 53 
Thresh, 256 
Tichborne. 123 
Tindal, 73 
Tinker, 188 
Trillat, 11, 12, 13 
True, 191 
Tsukamoto, 217 
Tuffier, 127 
Turner, 108 
Turpin, 259 

Ubaldi, 222 

Uhlenhut, 277 

Vallin, 25, 30, 33, 42, 72, 

96, 238 
Van Ermengem, 73, 84 
Vaughan, 39 
Vicario, 215 
Vollert, 275 
Von Heydn, 240 
Von Knome, 278 
Von Langenbach, 203 

Walker. 13, 281, 292 
Wallis Tavler, 169, 171, 

173 
Walter, IS 
Walther, 21 
I Warner, 72 
Waterhouse, 108 
Watson, 299, 300 
Watson Smith, 234 
Weir, 107 

Weiss, 175, 176, 178 
Werner, 21 
Wernitz. 32, 237 
Westbrook, 69 
Westcott, 241 
Whipple, 69 
Whitelegge, 99 
Whitmore, 272 
Will. 35, 218 
Williams, 155 
Wilson. 15 
Winslow, 9, 106 

Wirgen. 217 

Wolffhiigel, 25, 228 

Wood, 140 

Wright, 294, 295 

Wroblewski, 54 

Wunscheim, HI 

Wj-nter Blyth, 198, 255, 
280 

Young, 45, 77 

Zucker, 138 

Zurn, 78 

Zzigmondy, 185 



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DAY AND TO $1.00 ON THE SEVENTH DAY 
OVERDUE. 



\pmm mihim im^im 



JAN 



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K I AY 1 6 1955 






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Mk 1 8 1357^^ ' 



^AY 1 5 1957^' 



APR ' N iq^n 



APR 9 19B0 



LD 21-100m-12,'43(S796s) 



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HfBUc 

HEALTH 

LIBRARY 



U.C. BERKELEY LIBRARIES 



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