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f '

By AMY ELIZABETH POPE

ESSENTIALS OP DIETETICS

A QUIZ BOOK FOR NURSES

ANATOMY AND PHYSIOLOGY FOR NURSES

A MEDICAL DICTIONARY FOR NURSES

PHYSICS AND CHEMISTRY FOR NURSES
(with Anna Caroline Maxwell)

PRACTICAL NURSING

DIETARY COMPUTER

MANUAL OF NURSING PROCEDURE

ASISTENCIA PRACTICA DE ENFERMOS
(SjMtniah Edition of Practical Nimixig)

CON LA COOPBRAaON DB AnNA CAROLINE MaXWBLL

Physics and Chemistry

for Nurses

Amy Elizabeth Pope

Gr«diiAto ol the School of Nartiiii of the Pratbytorian Hospital,

in the City of New York ; Spodal Diploms ia Bdaoadoa

from Teaohon College, Golumbie Uoivertity, New

York ; Formerly Inttniotor in the School of Nnrt-

ing, Pretbyterien Hotpitel ; Inttniotor in the

School of Nnrsinl, St. Lnke't Hotpitel,

Sen Preneitoo, Gel.

Author of " Quiz Book of Nurttng," " Anetomy end Phytioloty

for NurMt," " A Medioel Diotionery for NnrMe,'' end,

with Anne MexweU, of " Preotioel Nurting^*

Smeond Edition

HmviMmd and Enlarged

tllusiratmd

G. P. Putnam's Sons

New York and London
Vhc 'RntcftetbocHev press

AMY ELIZABETH POPE
Second Revised Edition

Vbc Unfdteitecicf ^ctfib Itaw (tcft

PREFACE TO THE SECOND EDITION

The material of the first edition of Physics and
Chemistry for Nurses has been thoroughly revised
with help from Mr. Roy Theodore Nichols of the
Science Department of the San Diego High School
and author of Syllabus and Laboratory Manual of
Household Chemistry to whom my thanks are due.

Amy Elizabeth Pope.

351401

f I ■■

PREFACE

Instruction in hospital-housekeeping is gradually
attaining a well-deserved place in the curriculum of
schools of nursing. Since for nurses to have a proper
understanding of methods of cleaning, laundry work»
cooking and diet is of infinite value both to the hospi-
tal and to the nurses, especially those nurses who wish
to prepare for executive positions in hospitals and for
social-service work.

To provide a f otmdation for such knowledge, by
explaining the principles of the chemical and physical
properties upon which the various actions that occtir
in cleaning, cooking, digestion* metabolism, etc.,
depend, was one reason for compiling this book. A
second purpose was to explain important chemical and
physical processes constantly referred to in physiology,
materia medica, and the other studies included in the
school of nursing curriculum.

Also, the book contains many important applica-
tions of the chemical and ph3rsical processes described
to disinfection, cleaning, cooking, and other procedures
of interest to nurses.

In compiling this work, I have consulted all avail-
able books of chemistry and physics published within
recent years, but those which were most frequently
referred to are mentioned in the bibliography at the
end of this volume, one or more of which books on

vi Preface

each subject should be in every school-of-nursing
reference library. The majority of experiments here
described^ I have seen performed in the Household
Chemistry Class at Teachers College, Coltmibia
University, New York, or in the Domestic Science
Classes at the State Normal College, Santa Barbara,
California.

There are probably more experiments given than
there will be time for pupils in the majority of schools
to perform, but the book has been compiled with the
intent that any or all of the experiments can be omitted
without interfering with the value of the lessons. In
fact, many of the experiments described were inserted
to give the students a knowledge of how the facts they
demonstrate were ascertained and to illustrate facts
referred to, rather than that the experiments should
be performed, except by those who are especially
interested.

The tests for food adulteration and the illustrations
of calorimeters were taken from the different U. S.
Department of Agriculture publications mentioned in
the text, with the kind permission of the Secretary
of Agriculture.

Amy E. Pope.

CONTENTS

PAGS

CHAPTER I
DIRECTIONS FOR LABORATORY WORK

Names and Nattire of Utensils and Chemicals Used for the
Experimeats Given in this Book — Necessary Care of
Utensils — Laboratory Maxims — Laboratory Methods
— ^Weights and Measures i

CHAPTER II
NATURE OF MATTER AND ITS ELEBCENTS

Chemistry and Physics Defiiled — Nature of Matter, Mole-
cules, Atoms — States> of Matter — Molecular Motion—
The Elements — Physical and Chemical Changes —
Chemical and Physical Mixtures — Chemical Affinity
^]^hesion — ^Adhesion 26

CHAPTER III
ENERGY, HEAT, AND PRESSURE

Definition of Hypothesis, Theory, Law — What is Meant by
Eneigy — Effects of Heat — Different Ways in which
Heat is Transmitted — Difference between Amount and
D^ree of Heat — Heat Units — Specific Heat — Latent
Heat — Heat of Fusion— ^Relation of Pressure and Heat
— ^Atmospheric Pressure — The Effect of Pressure upon
the Boiling Point of Liquids — ^The Effect of the
Specific Gravity of Liquids upon their Boiling Point 37

CHAPTER IV

SOME COMMON PHYSICAL PROCESSES AND THEIR

RESULTS

Bvi^xuatioQ— Condensation — Humidity — Dew — Fog —
Frost — Rain — Hail — Snow— Artificial Ice — Distilla-
tion — Sublimation — Diffusion — Osmosis — ^Dialysis . 55

. vii

viii Contents

CHAPTER V
SOME COMMON PHYSICAL PROCESSES AND THEIR

RESULTS — {Continued)

Contraction — Expansion — Vacuum — Suction — Siphooage
— Capillarity — Conduction — Convection — Some Com-
mon Practical Applications of Knowledge of the
Nature and Action of these Processes. ... 71

CHAPTER VI
THE ETHER, HEAT, AND LIGHT

The Ether — Absorption, Radiation, Reflection, Refraction,
and Polarization of Heat and Light — Color of Light
and of Objects — Finsen Light — Phosphorescence and
Fluorescence 84

CHAPTER VII
ELECTRICITY

Theories Regarding the Nature of Electricity and Electrifi-
cation — Conductors and Non-Conductors — Different
Methods of Generating Electric Currents — Nature
and Action of Chemical Cells and Batteries for Generat-
ing Currents — ^Electrolysis — Electroplating. . 102

CHAPTER VIII
ELECTRICITY AND MAGNETISM

The Dynamo — Different Kinds of Magnets->— Magnetism —
Induction Coils — Transformers and Other Electrical
Appliances — ^Electric Currents as a Source of Heat
and Light — Measurement of Electricity — Static
Electricity — Physiological Action of Electricity —
Cathode Rays — X-Rays — Radio Rays . . .117

CHAPTER IX
SOUND — SHEARING — SPEECH

Origin of Sound — Some Important Differences Between
Sound and Light Waves — Transmission of Sound —
Why Sounds Are Heard — Causes of Differences in
Sounds — Methods of Intensifying Sound — ^Echoes . 138

Contents ix

^ PAOB

CHAPTEk X

CHEMICAL REACTIONS. VALENCE. RADICALS. CHEMI-
CAL FORMULiE AND EQUATIONS

Nature and Causes of Chemical Reactions — Nature of

Valence — Radicals — Chemical FormulaB and Equations 147

CHAPTER XI

MAIN DIVISIONS OF CHEMISTRY. CARBON. HYDRO-
CARBONS AND THEIR DERIVATIVES

Definitions of Organic and Inorganic Chemistry — Char-
acteristics of Oi*ganic Compounds — Isomers — Carbon
Oxids — Hydrocarbons and Some of their Important
Derivatives — ^Alcohols — ^Aldehyds . . . .157

CHAPTER XII

OXYGEN

The Occurrence and Nature of Oxygen — Nature of Oxida-
tion, Spontaneous Combustion, Oxids, Fireproof
Material, Fire Extinguishers, Products of Qddatioii . 169

CHAPTER XIII
FUELS AND ILLUMINANTS

The Nature and Origin of the Substances Commonly Used

for Fuel and Lighting ...... 181

CHAPTER XIV
SOLUTIONS. ACIDS. BASES AND SALTS

Different Kinds of Solutions — Different Kinds of Adds —
Characteristics of Acids — Tests for Acids — Properties
of Bases and Alkalies — Neutralization — Different
Kinds of Salts — Alkaloids and their Salts — Nature
of Pats-— Saponification — Nature of Soaps. . 191

Contents

PAOB

CHAPTER XV

WATER

City and Country Water Supplies — Ground Water —
Springs — ^Wells — Classification of Foreign Substances
Found in Water — Methods of Purifying Water — ^Hard
and Soft Water — Methods of Softening Different
Kinds of Hard Water— Objections to the Use of Hard
Water 206

CHAPTER XVI
THE CHEMISTRY AND METHODS OF CLEANING

Souroe and Composition of Some Common Detergents —
Nature of Origin of Material Used for Utensils and the
Action of Cleansing Agents in Common Use on these
and on Paint, Varnish, and Wax .... 234

CHAPTER XVII
TEXTILES

Classification and Origin of Textiles — ^Effect of Detergents
on Different Kinds of Textiles — Methods of Removing
Stains — ^Textile Tests — Printing and Dyeing — Nature
ofDyes — ^Fading of Colors 260

CHAPTER XVIII

THE CHEMICAL CONSTITUENTS OF THE HUMAN BODY

AND OF FOOD

Classificationt Nature, and Uses of the Substances Compos-
ing Animal Bodies and Plants — ^Tests for Proteins,
Starches, Sugars, Salts — Origin of Food Material . 376

CHAPTER XIX

KATUBE AND NUTRITIVE VALUE OF SOME OF THE

COMMON FOODS

Classification of Foods— Nature, Digestibility, and Nutri-
tive Value of the more Common Foods and Beverages
— Nature and Action of Condiments and Spices • 307

Contents xi

PAGB

CHAPTER XX
THE CHEiaSTRY OF COOKING

The Actkm of Heat, Acids, and Sodium Chlorid on Protein —
Sdubilities of Proteins — ^The Changes Caused in
Meats by Cooking — ^The Action of Heat and Adds on
Starches and Sugars — Solubilities of the Carbohydrates
of Food — Comparative Thickening Power of Different
Starches — ^MeUiods of Making Doughs and Batters
Light — ^The Nature and Action of Pectin . . 345

CHAPTER XXI

THE SPOILING, PRESERVATION, AND ADULTERATION

OF FOOD

Causes for the Spoiling of Food — Nature of the Oiganisms
that Cause the Spcaling — Chemical and Physical
Changes that Occur in the Decomposition of Food
Substances — Conditions Necessary to Prevent Con-
tamination and to Preserve Food — Some Common
Forms of Food Adulteration 365

CHAPTER XXII
CHEMISTRY OF DIGESTION

The Nature of the Changes Occurring in the Digestion of
the Various Food Stuffs— The Oxgans in Which These
Changes Occur — ^The Factors and Conditions Influenc-
ing Digestion — Nature of Enzymes, Zymogens, and
Kinases 387

CHAPTER XXm

THE CHEMISTRY OF ABSORPTION AND METABOLISM

Changes that Occur in Pood Substances during Absorption
— Nature of Metabolism — Composition of the Blood
— Changes that Occur in Pood Substances during
Metabolism— Some Causes and Results of Defective
Metabolism— The.Fuel Value of Poods— Food Require-
ments • •••••••• 404

xii Contents

PAGS

CHAPTER XXIV
THE URINE AND URINE ANALYSIS

Origin of Waste Matter in the Body and the Channels
through which it is Eliminated — Quantity of Urine
Voided — Composition of Urine — ^Foreign Substances
sometimes Pound in Urine, their Origin and Signifi-
cance — Nature of Urine Analysis — ^Methods of Deter-
mining the Quantity of Total Solids in Urine — ^Tests for
Acetone, Diacetic Add, Albumin, Glucose, Indican,
Bile, Blood, and Pus 416

Glossary • • . . 437

Index of Subjects . . . ~ • ' • . ' . 431

Indbx of Experiments 443

Physics and Chemistry for Nurses

Physics and Chemistry for

Nurses

CHAPTER I

DIRECTIONS FOR LABORATORY WORK

Names and Nature of Utensils and Chemicals Used for the
Experiments Given in this Book — Necessary Care of Uten-
sils — Laboratory Maxims — ^Laboratory Methods — ^Weights
and Measures

Laboratory work, properly performed, is of the
greatest assistance in gaining an understanding of
chemical and physical action, but when carelessly
done, it is a waste of time and material and is often
dangerous. To get the best results, the student
must,' from the beginning of her class work, be famil-
iar with the nature and the use of her apparatus and
chemicals and know how to work with and care for
all her utensils; therefore, this first chapter should be
read with attention.

Names and Nature of the Principal Utensils Required
for fhe Experiments Given in this Book

Pro. 1. Bbaesi.

Beakers ore made d
thin highly annealed
glass and can be used
lor boiling liquids in if
wire netting is placed
between them and the

Fig. 4. Cbucibls.
This is made of
fused silica. It will
stand a very high
temperature; even
dry solid substanocs
can be heated in it.

Fig. a. Bom-y.
Used to hold cold sub-
stances and to collect
gas. As it is of thick
glass, it cannot be used
tor boiling liquids.

Fig. 5. Evaporating Dish.

Liquids can be heated in porce-
lain evaporating dishes, if wire
gauze is placed between the
dishes and the flame.

Pio. 7. Flask,

Flasks being of thin

paas, liquid can be boiled

in then if wire netting

u put between tbemtuid

tMflaSM,

Pig. 8. Eklsnhbtsk

Tlask..

This is made of the

same intiH of jjLus a9

the flask ahown u Pig. 7*

Pig. 9. Funnel.

Fig. 10. Graduated Measures.

Fig. II. Iron Stand,

r**

Fia 12. Petri Dish.

Fig. 14 PtATiNUM

Wire in Glass

Rod.

Fig. 13. Pipette.

A pipette made as de-
scribed on page 15 will
answer the purpose for
class work.

Pig, 15. Spatula (Horn).
Metals being injured by many chemicals, bom

spatulas are used tor mining dry substances, and
glass rods for etirriag liquids instead of spoons.

Fig. 16.

(a) slide, lb) cover glass for use with micioscc^te.

For description of microscope, page 98.

Pic. 18. Tbisils
Tube.

Pic. 19. Trianglk.

Pig. 17.
(o) Test tube.
ib) Testrtubo holder. ,
(e) Tect-tube nek. ^

Pic. 31. Wates Baib.

Fra. 23. Wiu Gavh.

Pig. 36. ScALKs.

-tales, as(&), are not highly enough sensitized for this purpose ; they are,
however, necessary for heavier material

(Pifs. 33~36arementioaedlastasthey wiUnot be found in the iodividnal
equipment, tbeie being, usually, only a limited nuQiber of theaa arfirkw tof

6 Physics and Chemistry

In addition to the articles illtistrated, there will be
needed fpr each individual equipment:

A small asbestos mat.

Stoppers, preferably of rubber, to fit a test tube, a
flask, and a heavy glass bottle. The test-tube stopper
should have one hole through the center. There
should be two stoppers for the flask and bottle, one
with one hole and the other with two holes through it.
These holes must be exactly the size of the glass
tubing that is used.

Glass and rubber tubing about }i inch in diameter.

A piece of glass about }^ inch thick and 3 inches
square.

A tin or enamel dish about 2}^ inches deep and
io>^ inches in diameter.

Forceps.

Scissors.

File for cutting glass.

Glass rod. A fairly good substitute for the solid
rods usually bought can be made as described on p. 14.

Filter paper.

Litmus paper, blue and pink.

Thermometer, chemical.

A piece of copper wire about 9 inches long.'

Bunsen Burner

This burner was so called after the inventor, a
German chemist, named Bunsen, The principles of
its arrangement have been adapted to nearly all
forms of gas-stove burners.

Experiment i . Object : To study the Bunsen burner.

Procedure : Take the burner to pieces and examine

' This list does oot include the apparatus for xnOk testing, see
page 385* nor tlie articles required for ttriaalysts.

Directions for Laboratory Work 7

its different parts. Pot the parts together again and

omnect the burner with the gas pipe. Turn on and

light the gas; to do so, turn on a full current of gas

and hold the lighted match about two inches above

and to the ade of the top of the burner, then regulate

the flow of gas so that there

will be no waste. Close

and open the air holes and

notice the difference in

the flame. Extinguish the

flame by pinching the tube.

Light the gas at the air

holes. Extinguish the flame

and relight the gas in th^

usual manner. Arrange

the air holes so that there

is a yellow flame. Do this

by turning the small outer

tube. Hold a piece of glass

tubing in the flame.

How long does it take to
get the tubing soft enough
to bend?

Is the flame luminous, i. e., does it give light?

Is there a deposit formed on the glass tubing?

Is there mudi or little air entering the air holes of
the burner?

Arrange the air holes so that the flame becomes
blue.

In what way does this arrangement differ from that
required for a yellow flame?

Is there a deposit on the tubing?

How long does it take to get the tubing soft enough
to bend?

Fig. 37. Parts OP A BuNSBN
Burner.

(a) Air holes.

(w) Wing top. This is
used when a wide flame is
needed.

8 Physics and Chemistry

Is the flame more or less luminous than the yellow
flame?

Is there more or less air entering the air holes than
there was for the yellow flame?

Which flame will be the best for cooking over?

Mention two objections to the other flame for
cooking.

State a reason why the wrong kind of a flame some-
times occurs in a cooking stove.

Why does the gas sometimes strike back and bum
in the pipe?

The pupils should endeavor to answer the preceding
questions before reading the following paragraphs.

When the gas is turned on it flows through the tube»
and, as it passes the holes at the bottom of the tube,
which are provided to supply air, it will, if the
holes are open, draw the air through them. The
result is a blue flame, which is hot, but non-luminous.
This is often spoken of as the Bunsen flame. It is
the flame used for laboratory work, unless otherwise
specified, and it is also the correct flame for cooking
over.

If the air holes are closed, there will not be sufiident
oxygen admitted to the tube to unite with all the
carbon of the gas, consequently, some of the latter
will be separated in the flame by the heat and, at the
same time, its temperature will be raised to a white
heat and thus it will become luminous. If anything
is held over the flame, this unoxidized carbon will be
deposited upon it. This is often spoken of as sooL
The flame will not be as hot as the non-ltuninous blue
flame, because there will not be as much oxidation
(the combining of oxygen with a substance) going on,
pn account of the comparative smalln^ss of the m

Directions for Laboratory Work 9

supply. If too much air gets into the tube, it and
the gas will unite to form an explosive mixture and,
if this is ignited, the force of the explosion will cause
the flame to strike back to the opening where the gas
enters the tube.

Natoie of the Bimsea Flame

Experiment 2. Object, to study tiie nature of the
Bunsen flame.

Procedure: Secure a non-luminous flame and notice
that it has three distinct color zones.
Hold a piece of bright copper wire in
the tip of the outer zone. Notice the
discoloration that occurs. Hold the dis-
colored part of the wire near the base
of the central zone. Observe that
the discoloration acquired in the tip
of the outer zone disappears. Why
does it do so?

Experiment 3. Take a piece of tub-
ing, bent as in Pig. 29, and hold one
end with its opening in the tip of the
lower zone. After a few minutes ap- Pio. aS. Parts
ply the flame of a lighted match to *JVq^*^
the opening of the free end of the -^ ,,■. "^[^
tube. Explain the resiUt. jucing flame.

The dark zone at the bottom of the
Same is dark because of the gases issuing from the
burner. In the middle zone, due to the heat, these
gases are rapidly uniting with the oxygen of the air,
but there is still a large quantity of gas present un-
combined with oxygen. In the outer zone are the
exceedingly hot products of combustion and some

10 Physics and Chemistry

uncombined oxygen that is being separated £rom the
air. Due to the presence of this tincombined oxy-
gen, anything that will unite readily with oxygen, as

copper does when it is heated,
will become oxidized (i. e., it
will unite with oxygen) when
held in the outer zone of the
flame. This zone, therefore^ is called
the oxidizing flame. In the central por-
tion of the flame the hot tmcombined gases
will remove oxygen from a substance and this
part of the flame is therefore called
Fig. 29. the reducing flame, reduction being
Shape of tube ^jj^ ^ord used by chemists to denote
or Experiment ^j^^ removal of oxygen from a sub-
stance. Though there is a larger
quantity of uncombined gas in the lower than in the
central zone, reduction will not take place there, the
heat not being sufEcient to allow of the removal of
oxygen by the gas.

Precautions Necessary in flie Use of Utensils

Do not leave empty vessels of any kind over a flame.

When about to heat anything in glass or porcelain
utensils, place the burner in position, light the gas, and
regulate the flame before putting the utensil over it.

Use a low flame at first.

Never heat glass or porcelain utensils that are wet
in parts not in contact with the contained liquid.
The reason why they may break if this is done will
be seen in the sections on expansion and contraction.

Always rotate test tubes in the flame imtil all por-
^ons that are to be heated are uniformly hot.

Directions for Laboratory Work n

When heating liquids in a test tube, hold the tube
slantwise as in Fig. 30.

Put a piece of wire gauze between the flame and
glass beakers and flasks and porcelain dishes, except
crucibles. The wire spreads the heat and thus pre-
vents any one part
of the utensil be-
coming much more
highly heated than
another. The rea-
son why this is nec-
essary, like many
of the other pre-
cautions essential
in the care of glass-
ware, will be found
in the sections on
contraction and ex-
pansion. Crucibles
can be placed in a
triangle directly
over the flame, if the heat is applied gradually.

After removing flasks, etc., from the fire, place
them on a warm asbestos pad, never on a cold
surface.

Clean all utensils thoroughly after use and always
be sure that they are clean before use, otherwise,
experiments may be spoiled.

Numbering test tubes. — In order to avoid confusion,
it is often necessary to niunber test tubes, etc. Thia
can be done by cutting Dennison's labels into small
pieces (about ^ inch square), numbering these, and
sticking them on the utensil or with a wax pencil.

Pig. 30. Manner of Holding Tbst

Tubs.

12 Physics and Chemistry

to Remember about Chemicals

They are costly, do not waste them.

Many chemicals are inflammable; do not bring
those which are near fire.

Be careful not to inhale vapors.

Remember that many chemicals are very corrosive,
so do not spill any and do not put the bottles away
wet on the outside. Never lay a stopper on the table,
but hold it between two fingers with the point pro-
jecting behind the hand. If a strong add is spilt on
the flesh or clothing, wash with water and apply
ammonia or other dilute alkali at once.

Unless otherwise directed, when mixing strong
adds — as concentrated nitric, hydrochloric, and sul-
phuric — ^with a diluent — e. g., water — ^add the add
to the diluent.

Remember that many chemicals combine to form
explosive mixtures and, therefore, be careful not to
form the habit of bending over your work, and obey
all precautions given in the instructions.

Laboratoiy Maxims

Be accurate, be methodical, be careful, be dean,
be observing, remember that though the results of
some experiments are very pronounced, others are
difficult to discern.

When performing experiments, keep your notebook
at hand and record, at once, wdghts and measures
and everything of importance observed.

Be on the alert to see, smdl, and hear, but do not
taste unknown substances tmless directed to.

Directions for Laboratory Work 13

Laboratory Methods

The Preparatioii of Glass Tubing

To cut 8^8 tubing. — Make a scratch on the tubing
where it is to be divided with a triangular file; take
the tube in both hands with the thumbs almost to-
gether, as in Fig. 31, opposite the scratch, and push

Pig. 31. Manner of Holding Glass Tubs While

Breaking it.

slightly upward with the thumbs. If the tube does
not break readily, make the scratch deeper, do not
use force. When cutting hard glass or heavy tubing,
put a handkerchief or piece of doth between the tubing
and the hands,
in case the glass
should splinter.
After glass is
severed in this
way, the sev-
ered ends shotild
be rotated in a
flame for a few
minutes in or-
der to remove
sharp edges.

Bending g^ass tubing. — Necessary precautions:
Heat and cool the tubing slowly, therefore, coat the

(a)

Pig. 32.
Good bends. (6)

A poor bend.

14 Physics and Chemistry

bend with soot by holding it in the yellow flame and
do not lay the tubing on a cold surface while it is hot.
Rotate the tubing while heating it, especially at first,
so as to prevent cracking by uneven heating. Apply
the heat continuously and do not attempt to bend
the tubing tmtil the heat has rendered it perfectly
pliable. Then remove from the flame and bend,
being careful while doing so to keep the bend round;
if the curve is so sharp that the tubing is flattened at
any point the passage of liquid or gas will be inter-
fered with, also such bends are brittle and break easily.
Procedure: Use a wing-top burner. Secure a
yellow flame. Keep this flame for thin-walled tubing.

Fig. 33. Holding Glass Tubing in the Flamb.

but for that with a thick wall, change to a colorless
flame as soon as the tubing is slightly coated with
soot at the part which is to be bent. Hold the tubing
between the thumb and fingers and rotate it in the
flame until it is pliable; then remove it from the flame
and bend it into the required shape. It is well to
keep the tube on an asbestos mat while bending it.

To draw out glass tubing. — Rotate the central
portion of the tubing in the flame until it is soft.
Remove from the flame. Then make traction on both
ends until the points are of the desired diameter.

Let the glass become perfectly cold and then cut it

Directions for Laboratory Work 15

as previously directed. Tubing prepared in this way
can be used for pipets.

To make g^ss stirring rods. — Heat and draw the
tubing as directed in the preceding paragraph, but

Fig. 34. Glass Tube Dsawn to a Point, Ready to Cut. ]

instead of cooling and cutting the point, draw the
glass apart and fuse the ends in the flame tmtil there
is no opening. This will result in two tubes eadi
closed at one end. If a bulb is wanted at the end of a
rod» rotate the closed end in the flamb until it is soft,
remove it from the flame, and, at once, blow into the
open end. Continue blowing until a bulb the desired
size forms. Such rods are fairly good substitutes for
solid glass ones.

Ffltering

Filtering is a process by means of which finely
divided solids are removed from liquids. It consists

h c

Fig. 35. Folding Filter Paper to Fit Funnel.
(a) Filter Paper, (b) first folding, (c) second folding.

in making liquids pass through a substance that is
sufficiently porous not to interfere with the passage of

i6 Physics and Chemistiy

liquid matter, but dense enough to prevent or Impede

the passage of solids suspended in the hquid. The

methods of filtering will be discussed in Chapter XV.

In the laboratory,

filtering is usually

done with filterii^

paper. This is

folded as shown in

Fig> 35> s^d placed

in a fumiel. When

folding the paper,

be careful not to

press it at the point

or it will tear.

Place the paper in

the funnel with

three thicknesses

on one dde and

one on the other.

Do not allow the

paper to project

above the tunnel

and fit it into the

Fig. 36. PiLTBMNG. funnel in such a

manner that its

entire surface is supported, otherwise the weight of

the liquid may tear the paper. When the Hquid to

be filtered is thick, it is usually better to moisten the

paper with distilled water before pouring in any of

the liquid. Also, it is well to pour the Uquid down

the side of a rod held with its point upon the single

layer of paper, as in Fig. 36.

To Introduce a powdered substance into a narrow
necked flask or a test tube. — Fold a strip of paper as

Directions for Laboratory Work 17

shown in Fig. 37, place the powder in one end of the
trough thus made; introduce the paper into the tube,
turn the paper so that the powder will be deposited
where desired; withdraw the paper. Slide heavy
pieces in carefully; a
flask is easily broken.

Weighing

When weighing chem-
icals, put them on a
piece of paper or in
some utensil, as a watch
crystal, beaker, etc. ; do
not put them on the un-
protected pan of the
scales for many chemi-
cals will corrode or
otherwise injure the pan.
The weight of this pa-
per or utensil must be
either noted, recorded,

Fig. 37. Putting a Powdek
INTO A Narrow-Necked Flask.

(a) Paper trough with pow-
(6) Powder deposited in

and afterward deducted

from the total weight of ^^^

utensil and chemical, or flask.

else an object of equal

weight must be placed in the other pan. The weights

are put in the center of the right-hand pan.

Pupils should form the habit of handling weights
with forceps,for when small amounts are being weighed,
even moisture from the fingers will interfere with an
absolutely correct result.

i8 Physics and Chemistry

Measuring

Liquids are measured in graduated glass measures,

pipets, and burets.

When using measures, hold the measuring
glass so that the lowest point of the meniacus '
is on a level with the eye.

To use a pipet, hold it between the thtunh
and the middle finger of the right hand; placa
the pointed end in the liquid and the other
end in the mouth and suck up the liquid
nearly to the top of the tube, but be very
careful not to draw it into the mouth; while
removing the tube from the mouth, quickly
place the index finger over the top. Then,
by slightly releasing the pressure of the fin-
ger over the opening, either allow the num-
ber of drops required to escape, or, if the
pipet is a graduated one, allow the liquid to
drop from the tube, back into the botUe, un-
til the top of its column is on a line with the
mark of the quantity required. Then hold
the pipet over the utensil into which the
liquid is to be put and release the finger over
the opening; the pressure of the air entering
the tube will force the liquid from it.
When using a buret, pour the liquid to be

Pig. 38. measured into the buret tube, place a recep-

BuBET tacle under it, and, carefully, release the

pressure of the stop cock on the rubber tubing

until the amount of liquid required has passed into

the receptacle.

■ The upper surface of a fluid column, as that of mercury in a
thermometer. The lowest point, «. e,, in the center, is considered
the correct height of the column of liquid.

Directions for Laboratory Work 19

List of Chemicals, Solutionsi and Reagents Needed

for Experiments

Acetic add. CH3COOH. Commercial acetic acid
is about 36%. Glacial acetic add is 99%.

Acetic anhydrid. C4H6O3.

Alcohol, amyl. CjHixOH.

Alcohol, ethyl. CaHjOH.

Alum. KAICSO^),.

Ammonltmihydroxid. NH4OH. This as purchased
is about 28%. Known also as ammonia water.

Ammonium molybdate solution. (NH4)aMo04.
This is prepared as follows: Add 25 gm. of molybdenum
oxid (M0O3) to 100 cc. of NH4OH and stir the solu-
tion tmtil the powder is dissolved. Cool and add
250 cc. of nitric add.

Ammonium oxalate. (NH4)aCa04.

Barium chlorid. BaCl,.

Benzoic add. CyH^Oa.

Borax. NaaB407. loHaO.

Boric add. HjBO^.

Caldum carbonate. CaCO^.

Caldum chlorid or chlorid of lime. CaCla.

Caldum sulphate. CaS04.

Carbon disulphid. CSa. This is very inflammable.
It is only required for Experiment 75.

Chloroform. CHCI3.

Copper sulphate. CUSO4.

Fehling's solution. This is prepared as follows:

Solution A: Dissolve 34.64 grams of copper sul-
phate in 400 cc. of distilled water. When this is dis-
solved, add enough water to make 500 cc. of solution.
Solution B: Dissolve 180 grams of Rochelle salt in
500 cc. of sodium hydroxid solution, 10 %.

20 Physics and Chemistry

Ferric alum. KPe(S04)a. i2HaO.

Fibrin. Dried blood fibrin can be obtained from
dealers in chemical apparatus.

Hydrochloric add. Known also as mtuiatic acid.
HCL The concentrated solution is 40%. For the
dilute solution add i volume of the concentrated add
to 4 volumes of water.

lodin. I. Tincture of.

Lead acetate. (CH3 COO) a Pb.

Litmus powder.

Logwood, tincture of.

Mercuric chlorid, corrosive sublimate, or bichlorid
of mercury. HgCU.

Millon's solution. Make as follows: Dissolve 5cc.
of merctuy in 95 cc. of concentrated nitric add and,
when action ceases, add twice the voliune of cold
water.

Nitric add. Known also as aqua fortis. HNO3.
Concentrated nitric acid is 70%. For the dilute solu-
tion add I volume of the concentrated add to 4
volumes of water.

Oxalic add. (COOH)a.

Pancreatin solution. This can be made by dis-
solving 2 grams of the.commerdal pancreatin in 300
cc. of warm — not hot— water. Or it can be prepared
as follows from the fresh pancreas of a pig: Free the
pancreas from fat as far as possible; mince it, weigh it,
put ia into a flask, and add three times its wdght of
distilled water and its own wdght of alcohol. Shake
the flask vigorously and then let it stand for three
days at room temperature, shaking it occasionally.
Then strain the solution first through muslin and
afterward through filter paper. Measure the filtrate
and, for every liter, add i cc. of strong HCL Let

Directions for Laboratory Work 21

this stand for a week and then filter. Pour the filtrate
into a flask that can be tightly corked. It will keep
indefinitely, the alcohol acting as a preservative.
The solution contains trypsin and amylopsin, but no
lipase. See Chapter XXII.

Pepsin solution. This can be made from the com-
mercial pepsin. The percentages required are given
in the experiments, Chapter XXII., and the solution
should be prepared on the day that it is wanted, as
it does not keep.

Potassitmi fenocyanid or yellow prussiate of potash,
K.FeCfiNe.

Potassium permanganate. KMn04.

Potassium thiocyanate or potassium sulphocyanid.
KSCN.

SaUcyHcacid. CfiH.OH.COOH.

Silver nitrate. AgNOj. Solution 2%.

Soap solution. Make as follows: Shave and dis-
solve 50 grams of white castile soap in i liter of hot
water. Filter the resulting solution.

Sodium carbonate. NajCOj.

Soditun chlorid. NaCl.

Sodium hydroxid. NaOH.

Starch solution. Blend one teaspoonftd of starch
with one tablespoonful of cold water and then add
slowly, while stirring, 250 cc. of boiling water. Boil
the solution for three minutes. This should not be
prepared long before it is required for use.

Sulphuric acid. HaS04. Concentrated 94%. For
the dilute solution add i volxmie of the commercial
add to 4 volumes of water.

Tumeric paper.

22 Physics and Chemistry

Points to Remember when Making Solutions

When diluting the adds, add the acid to the water
and use cold water.

When dissolving solid substances, use boiling water
unless otherwise specified. Two important excep-
tions are pepsin and pancreatin; for these use warm,
but not hot, water.

When calculating the amount of a chemical to use
remember that i per cent, means one part in one hun-
dred. Therefore to make a i per cent, solution use I
gram or i cc. of the substance to be dissolved to loo
cc. of water or whatever solvent is to be used. For a 5
per cent, solution, use 5 grams or 5 cc. in 100 cc.
For a 10 per cent., use 10 grams or 10 cc. in 100 cc.
For a :^ of a I per cent, use i gram or i cc. in 1000 cc.
For a ^ of a I per cent, use 2 grams or 2 cc. in
1000 cc. of solvent.

Unless otherwise specified the strengths of the solu-
tions for the experiments are to be as follows: Dilute
adds, diluted according to the directions already
given; concentrated axtmionia; 10% solutions of the
other hydroxids and the salts.

Mbtric Wbigbts

MHUgram
Centigram

.001 of a gram
.01 " " "

Gram

Principal unit

Decagnun
Hectogram
Kilogram
Mynogxam

10 grams
100
' 1000 " •

10,000 -

Directions for Laboratory Work 23

Comparative Values of Apothecaries* and Metric

Fluid Measures

Minims CuMc

Minims CiOnc

Flnid Cnhie

Fluid Cubic

Ctnli-

Caai*

Ounces Centimeters

meters

X-0.06

35-1.54

9 — 59.30

3Z— 63Z.00

2 -0.13

30— Z.90

3 — 89.00

33 — 650.00 .

3 -o.x8

35-a.z6

4- ZZ8.40

33 — 680.00 .

4-0.34

40 —3.50

5- Z48.00

6- Z78.00

34— 7Z0.00

5 -0.30
-0.36

45-3.80

35— 740.00
30- 769.00

50-3.08

7- 307.00

1 7-0.43

8 -0.50

55^3.40

8- 336.00

37- 798.50

9— 360.00

38— 838.00

9-0.55
zo —0.60

Fluidrams

zo— 395.70

39— 858.00
30- 887.35

I, - 3.75

zt- 335.35

zz —0.68

zj- 4.6s

Z3— 355.00

31- 917.00

Z3-0.74

z}- S.60

Z3- 335.00

3«

Z3 -0.80

zf- 6.5Z

Z4- 4x4.00

or —946.00 !

Z4-0.85

3- 7.50

is'^ 444.00

z quart

Z5 -0.9a
X6-Z.OO

3— ZZ.35

48 -Z4 19.00
56 — X055.00
04 — Z893.00
73— 3za8.oo

4-Z5.00

or -473.XI

Z7-Z.0S
Z8-Z.I3

5 - Z8.50
6—33.50

z pint J

17— 503.00

Z9-I.Z7

7 —36.00

x8— 533.00

80—3265.00
96 — 3839.00

30-Z.35

19— 563.00

Flnidounce

30— 59X.50

XZ3— 33x3.00

I — 30.001

138—3785-00

COMPARATIVB values op APOTHECARIES' AND METRIC WEIGHTS

Grains Grams

Grains

Grams

Grains

Grams

Drams Grams

ilf— 0.00065

-0.Z30

- Z.70

3-XX.65

^ — 0.00ZOZ

-O.Z95

- X.75

— X.83

4-15.50

A-0.00Z08

—0.360

5-X9.40
6-33.30

A -0.00x30

-0.334

— X.87

«| —0.00x35
A — O.OOZ63

—0.400

- X.95

_ 7-37.30

-0.460

- 3.00

Ounces

£-0.00x80

-0.530

— 3.X0

X- 3T.Z0
3 - 03.3O

A — 0.00303

—0.600

— 3.X6

tfl— 0.003X6

—0.650

— 3.30

3 - 93.30

A -0.00359

-0.7x5

— 3.35

4- X34.40

A -0.00370

-0.780

- 3.30

iz ;ii:is

iS -0.00334

-0.845

- 3.40

A —0.00360

-0.907

- 3.47

7- 3Z7.70
S— 348.80

9— 380.00

A -0.00405

-0.973

- 3.55

A — 0U>0433

Z5.3

;-x.ooo

— 3.60

A -0.00540

- X.040

- 3.73

XO- 3ZX.0O

1 -0.00648

— I.X03

- 3.80

XX- 343.Z4

-0.008 zo

-X.Z60

- 3.00

X3- 373.33

— O.OZO8O

— Z.340

- 3.35

X4- 435.50
x6- 497 >6o

— O.OZ396

-Z.300

- 3.40

— 0.0Z63O

-Z.360

«S

- 3.65

34- 746.40
48 — 1493.80

\ -0.03Z60

-Z.435

- 3.75

} -0.03340
1 —0.04860
t -0.065

-Z.460

Drams

ZOO-3XXO.40

-X.S5
-X.63

X- 3.90
3- 7.80

Physics and Chemistry

COMPARATIVB VALUES OP AVOIRDUPOIS AND METRIC WEIGHTS

Pomndt

1.77a

- 14.17$

z ■" 38^50
2- 56.700
3"i 85.050
4 -1X3^00

?-X4i.7S
■•Z70.ZO
7-19845

8 ■■336.80

9 -ass.iS
zo«> 383.50
ZZM3ZI.84

Z3 —340.30

X3 -368.54
Z4 -396.90

X5 -425.35

Pounds,
I - 4S3.60
a — 907.X8
3.3 » 1000.00
3 —1360.78

9
10

■»z8l4.37
■■3367.96
-3737.55
-3Z7S.X4
-3638.74

—4083.33
-4S3S.9«

Comparison of Centigrade and Fahrenheit

Thermometric Scales

Cbkt. Pabr.

Cknt. Pahr.

Cbkt. Pahr.

zoo — 3Z3

63.3— 144

34.4-

X3.3- 8

98.9—310

61. z — 143

33.3-

Z4.4- 6
Z5.6- 4

97.8- 308

60 — Z40

33.3-

96.7-306

58.9- Z38

3Z.Z-

Z6.7- a

95.6-304

57.8 -Z36

30 —

Z7.8—

94.4- 303

56.7 - Z34

Z8.9-

Z8.9- a

93-3-300

55.6- 133

Z7.8 —

30 - A
3Z.Z— 6

93.3— Z98

54.4- 130

Z6.7 —

9I.Z— 196

53.3— Z38

Z5.6 —

33.3— 8

90 -194

53.3-136

Z4.4-

«!

23.3— xo

88.9— 193

51. Z— 134

13.3-

34.4- Z3

36!7- xo

87.8— Z90

50 -133

Z2.3 —

86.7- x88

48.9 -Z 30

ZI.Z —

85.6- z86

47.8 -zz8

zo -

37.8- Z8

84.4 -Z84

46.7 -z 16

8.9-

38.9— 20

83.3 -z83

45.6- z 14

7.8-

30 - 33

83.3- z8o

44.4-112

6.7-

3Z.Z- 34

33.3- 36

8z.z— X78

43.3-110

5.6-

80 -Z76

43.3 — 108

4.4-

33.3- 28

78.9-174

41.1- 106

3.3-

34.4- 30
35.0- 32

77.8-173

40 -104

3.3 —

76.7 -z 70

38.9 -103

z.z —

36.7- 34

37.8- 30

75-6 -z68

37.8 — zoo

—

74-4 -l^

36.7- 98

1.1 —

38.9- 38

73-3 -X64

35.6- 96

3.3 —

40 - 40

73.3-163

34.4- 94

3.3-

4Z.Z- 42

7Z.l-z6o

33.3- 92

42.3- 44
43.3- 46

22 "'5?

32.2— 90

68.9-156

3Z.Z— 88

6.7-

44.4- 48
45.6- 50

67.8-154

30 - 86

7.8-

66.7-152

38.9- 84

8.9-

46.7- 52

65.6-150

37.8- 83

10 -

47.8- 54

48.9- SO

64.4 -Z48

36.7— 80

zi.x-

63.3 -Z46

35-6- 78

23.3-

Directions for Laboratory Work 25

Method of Converting One Scale into Another

1. To change a Fahrenheit reading into centigrade:
Subtract 32 from the given degree (the freezing point
in the Fahrenheit scale being this much higher than in
the centigrade scale), mtiltiply the remainder by 5, and
divide the result by 9. Thus:

2i2*^F.— 32«i8oX5«900-§-9«ioo*^ C.

2. To change a centigrade reading into Fahrenheit:
Mtiltiply the given degree by 9, divide the result by 5^
and add 32 to the remainder. Thus:

ioo^C.X9 =900-5-5 = 180+32 =2i2**F.

CHAPTER II

NATURE OF MATTER AND ITS ELEMENTS

Chemistry and Physics Defined — Nature of Matter, Molecules,
Atoms — States of Matter — Molecular Motion — ^The Ele-
ments — Physical and Chemical Changes — Chemical and
Physical Mixtures — Chemical Affinity — Cohesion — Adhe-
sion.

Chemistry and physics defined. — Chemistry and
physics are very intimately related since they are
both concerned with the study of the Aattire of matter,
especially inanimate matter, and with the changes
which matter may be made to undergo. Chemistry,
however, is more particularly devoted to the study of
the composition of matter and is therefore often de-
fined as the study of the composition of matter, and
physics being more especially concerned with the
properties and activities of matter has been defined as
the study of the properties of matter and as the study of
matter in motion.

Nature of matter. — ^By matter is meant anything
which possesses weight and which occupies space*
All matter is composed of inconceivably small par-
ticles called molecules and molecules are composed of
still smaller particles called atoms.

Molecules. — ^A molecule is said to be the smaUesi
part of a compound that can exist by itself and main'-

Nature of Matter and its Elements 27

tain its identity. Thus a molecule consists of two
or more atoms. The atoms composing a molecule
may be all of the same element, e. g,^ all hydrogen or
all oxygen, etc., or they may be of different elements,
e. g., a molecule of water consists of two atoms of
hydrogen and one of oxygen.

Atoms. — An atom was formerly defined as the
smallest particle of an element that can exist and
atoms were thought to be absolutely indivisible, but
it has been shown that atoms of elements are made of
still smaller particles to which the name electrons
has been given and a definition used for an electron
is a unit or atom of negative electricity. Atoms do
not, however, separate in ordinary chemical reac-
tions and they are still generally regarded as being
indivisible.

Compounds and elements. — ^A compound is a sub-
stance made up of two or more elements; an element
is a substance which cannot be di\aded into simpler
substances by any known means. For example,
water is a compound of hydrogen and oxygen, but
hydrogen and oxygen have never been subdivided and
are therefore considered elements.

States of matter. — Matter is generally described as
existing in three physical states, viz., solid, liquid and
gaseous. All matter, however, cannot be classified as
belonging strictly to any one of these three states and
thus we speak of semi-solids and semi-liquids. Neither
is the ordinary physical state of any kind of matter
a fixed unchangeable thing, for by increase of tem-
perature, solids can be liquefied and liquids vaporized
(i. e., made gaseous), and by putting gases under
pressure in a low temperature, they can be changed
to liquids and a low temperature will solidify liquids.

28 Physics and Chemistry

A very great change of temperature is not necessary
to transform the physical state of some substances,
but only very excessive changes will alter that of
others.

One of the great differences in the nature of matter
in its different physical states is the dissimilarity of
the motion of its molecules.

Molecular motion. — It is the belief of scientists
that the molecules composing all matter are constantly
in rapid motion, but that differences exist in the kind
of motion possessed by the different forms of matter.
Thus, in solids, it is thought, the molecules oscillate
with great rapidity about certain fixed points, but
are held in their relative position by their attraction
for each other or, as this is called in physics, cohesive
force. However, even in solids, as will be discussed
in the section on diffusion, the molecules sometimes
break away. In liquids, though the molecules tend
to ding together, they have no fixed position, but
move about freely; thus liquids can adjust themselves
readily to the shape of any vessel into which they are
put, and when different liquids are poured into a
vessel, they soon become mixed, as they would not
do if their molecules were fixed and motionless. The
movement of gas molecules is very marked and they
exert no cohesive force whatever upon each other,
but, on the contrary, they tend to separate and fly
apart indefinitely, spreading in all directions. One
evidence of this is the rapidity with which the odor
of a gas (e. g, amimonia) will be perceived at a distance
from an open vessel containing even a solution of the
gas. The odor of the gas cotdd not become thus
diffused if the molecules were stationary in the vessel
for there would be no odor were there not some

Nature of Matter and its Elements 29

molecules of the gas present in the air that is in*
haled.

Until the idea of molecular motion was conceived,
scientists found it impossible to explain many com-
mon phenomena, such as pressure of gases, evapora-
tion, contraction, and expansion.

Number and condition of elements. — ^There are
about eighty-three elements known at the present time.
Of these, eleven are ordinarily gaseous — the principal
gaseous ones being oxygen, hydrogen, nitrogen, and
chlorin — ^two are liquid — ^mercury and bromin, and
the others are solid.

Symbols. — ^In order to facilitate the explanation
of the composition of chemicals and of chemical re-
actions, chemists have adopted symbols to represent
the elements. These symbols consist of the initial
letter of either the Latin or the English name of the
element, or when there are two or more elements
having the same initial letter, of the initial and one
other letter. For example, C stands for carbon, CI
for chlorin, N for nitrogen and Na for sodium, the
Latin name of which is natrium. A number placed
slier a symbol shows that there are as many atOBis of
the element as the number designates; thus HaO
(water) signifies that in each molecule of water there
are two atoms of hydrogen and one atom of oxygen.

Atomic weight. — ^Atoms of the elements are believed
to have fixed weights, but, as it would take about
200,000,000 hydrogen atoms placed side by side to
form a line one centimeter in length, their weight can
be calculated only as relative to some fixed standard
that is given a supposititious weight. For example,
hydrogen, which, was formerly used as the standard
was given a supposititious weight of one, called by some

Physics and Chemistry

writers one microcrith, ' and the weight of each of the
other elements was determined by fibnding the weight
of the amount that combined with a definite weight
of hydrogen. Lately, oxygen has been chosen as a
standard because as more elements unite to form de-
finite compounds with it than with hydrogen it is
easier to compare their weight with it than with the
latter. The atomic weight of oxygen, however, is
sixteen.

Molecular weight. — In studying chemistry, one
hears constantly not only of atomic weights, but also
of molecular weight. By the weight of a molecule
is meant the stun total of the weights of all the atoms
composing it. Thus, the molecular weight of calcium
carbonate (CaCO,) will be lOo because, as shown by
the symbols, it is a compound consisting of i atom of
calcium, which weighs 40, one atom of carbon, which
weighs 12, and three atoms of oxygen each one of
which weighs 16; thus 40+12+48 = 100.

The following table gives the names of the elements,
their derivation and atomic weights. It is of course
not necessary to memorize any of the weights, and
only, the elements marked with an asterisk need be
remembered.

A Table of the Elements

Blembnt

Symbol

Atomic
Wbight

Natueb

WiiBRR Found
IN Naturb

^Aluminittm
(Aluminum)

37.1

A white metal that
is very light, stiff, and
strong. It is a good
conductor of neat
and of electricity.

In many soils and
rocks, where it exists
in the form of ozids
and salts.

> The microcrith is defined as the weight of one atom of hydrogen.
It is not any definite weight and is so infinitely small that it
cannot be compared with sach weights as grams and grains.

Nature of Matter and its Elements 31

▲ntimon

itimony
(Ut.5/fMif«)

Symbol

Am*gon
Arsenic

^Barinm
Beryllium
^Bismuth

Boron
"^Bromin

Cadmium
Canium

^Calcium

'Carbon

Cerium
Quorin

Cbromium

Atomic
Weight

i20.a

A
As

Ba
Be
Bi

B
Br

Cd
Cs

Ce
CI

39-9
7S.0

137.4

9.1

208.5

II.O

79.96

1x2.4
132.9

40.1

12.00

140.25
35.4$

Naturb

A bluish-wbite,
hard, brittle, solid.

52.x

Gas.

A steel-gray brittle
metallic^ooldng sub-
stance.

A pale-yellow

metal.
Metal.

A grayish-white
crystallme solid.

Resembles silicon.

A dark red liquid
about three times as
heavy as water. Its
vapor has an offen
sive odor and is very
irritating to the eyes,
throat, etc

Resembles zinc.

A white metal.

al.

Silvery-white met<

A solid that is
amorphous in char
coal; crystalline in
diamond and graph-
ite. Its comi>ounds
are numerous and oc
cur as gases, liquids
and solids.

Resembles iron.

A greenish-yellow

f[a8. It has a pecu'
lar suffocating odor,
and, if inhaled, i>ro-
duces a severe irrita-
tion of the respira
tory tract. It has a
strong affinity for
hjrdrogen and it com
bmes readily with
many metals.
A hard metal.

Whsrs Pound
IN Naturb

Occurs in nature
chiefly as a sulphid
called stibnite, but is
found also as an ozid
and as a constituent
of various complex
minerals.

In the air.

In various ores. It
occurs most frequently
in the form of salts
and other compounds
the majority of which,
unlike pure arsenic,
are highly poisonous.

In minerals.

In beryl and in
various mmerals.

Occurs in certain
localities in uncom-
bined state, and also
as an oxid and sulphid.

Chiefly in borax and
boric acid.

In sea salt and the
salt ot various springs
and salt deposits.

In sine oree.

Chiefly in mineral
springs.

In various com-
pounds as marble,
limestone, fluorspar,
phosphorite, gypsum,
etc.

In all organic matter
and a few inorganic
substances as dia-
monds, calcium car-
bonate, sodium car-
bonate, etc.

In a few rare min-
erals.

In sea-water and in
salt-deposits in the
forms of chlorids.espe-
cially those of sodium,
potassium,and magne*
sium. It is never
found free in nature.

In chromite
^chrome iron ortt.

Physics and Chemistry

Blbicbmt

Symbol

Atouic
Wbicht

Natuks

Whbrb Pound
IN Natubs

Cobalt

59.0

A reddiah or white
metal (some of its
■aits are blue).

Ooeors chiefly in
combination with
arsenic and sulphur.

Colambium

94*0

Metal.

In columbite and a
few other rare mia*
erals.

♦Copper

(L«t. Cuprum)

63.6

A reddish colored

Pree and in varioot

metal.

ores.

Coronittxn

Not
Imown

Gas.

In the sun.

Crvpton
Brbmm

80/0

A very inert gas.

In the air.

Z66.0

A metal-like solid.

In some rare metals.

Pluoria

Z9.0

Gas, resembles
chlorin.

In a few minerals,
chiefly fluorspar.

Gadolinittm

156.0

Solid.

In a few minerals.

Gallittm

70.0

Metal.

In some sine blends.

Germanittm

72.5

Metal.

In the metal argy-
rodite.

Glaciniini

9.03

Metal.

In beryl and a few
minerals.

♦Gold {Aurum)

i97.a

Metal.

Pree and in ores.

Helium

4.0

A light gas.

In the atmosphere.

♦Hydrogen

Z.008

A very light gas.

In water and in
many other com-
pounds both organic
and inorganic.

Indtitm

1x3.6

Metal.

In zinc ores.

♦lodin

126.97

Purplish-black
crystals which vapor-
ize at ordinary tem-
peratures, giving ofl
a violet-vapor ofun-
pleasant odor.

lodin occurs free in
sea-water, from which
it is absorbed by cer-
tain sea-planta, so that

it is found in their

ashes. Also it is found

in salt springs and

beds and in Chili salt-

peter.

Iridium

X93.0

Metal.

In a rare mineral
called iridosmin.

♦Iron {Penum)

55.9

Metal.

A common constit-
uent of rocks and
soils. It is assimi-
lated by plants and
animals and is essen-
tial to their life.

Krypton

8Z.8

Gas.

In the atmosphere.

Lanthanum

X38.9

Metal.

In a few rare metals.

♦Lead {Plumbum)

206.9

Metal.

Occurs chiefly as a
sulphid called galena.
In a few metals, as

Lithium

7.03

Silvery-white alka-

li metal.

lepidolite. and, in the
form of carbonates
and chlorids. in some
mineral waters.

24.36

White metaL

It is a constituent
of many rocks, also
salts of the metal are
found in sea-water
and salt-deposits.

♦Mangmnete

55-0

A hard gray metal
somewhat like iron.

In some iron ores

and minerals and as

a dioxid called pyro^

lusiU,

Nature of Matter and its Elements 33

Blsmskt

Symbol

Atomic
WncHT

Naturs

Whxrx Found
IN Naturb

^Mercury

aoo.oo

A heaTjr vlvery

It occurs chiefly as

{Hydrargymm)

liquid.

a sulphid called cin*
nabar, and in globules
of metal inclosed ia
the cinnabar.

MotybdcAum

96.6

A metal-like ele-
ment.

In molybdenite.

X43.6

In a few rare mia«
erals.

Neon

20.0

An inert bm.

In the air.

Nickel

sa.7

Metal.

In metallic ores. It
is usually found com-
bined with arsenic or
sulphur.

In the air and ia

^Nitrogen

14.04

Gae.

many organic and in-

organic substances. It

is an essential con-

stituent of all living

matter.

X9X.0

MetaL

In platinum and
iridosmin.

*0z7fea

16.00

Coloileis, odorleu,
tasteless gas, slightly

It occurs free in the
air; in the combined
state, it forms | of
water and enters mto
the composition of all
organic^ and nearly all
inominic, compounds.
Free and in com-

106.5

A iilver-w h i t e

metal.

bination with other
metals, especially gold
and platinum.

*Photphonif

3I.0

A yellowish, waxy,
soft solid.

In the form of vari-
ous phosphates. P.
occurs in many or-
ganic and inorganic
substances.

^Platiiiiuii

194* S

A grayish-white
metal of high luster,

Chiefly alloved with
ffold and what are
known as the plati-

very malleable and

ductile.

num metals. «. «., rho-
dium, pallidium, and
osmium.

^PotMeitim

39*X5

A soft alkali metal.

In many rocks, min-

{KMum)

It decomxxMes water
very vigorously and
the heat evolved in
the chemical reaction
is sufficient to ignite
the hydrogen set free.

erals, and organic
compounds. It is
never found free ia
nature.

PrmModrmittm

143*5

In a few minerals.

lUdiam

335*0

• • •

In pitchblend.

Rhodium

zoa.9

White metal.

Usually in conaeo>
tion with platinum.

Rttbidtttm

S5.5

Metal.

In certain mineral
springs.

Rtttheaitun

X01.7

MetaL

Associated with
platinum.

Samftriom

OfB

XS0.3

In a few rare aita«

erals.

^fff|f^i^«H

43*97

« • •

In a few mtaarale.

Physics and Chemistry

Sdenium
^Silicon

•Silver

(Lat. Argtnium)
•Sodium

(Lat. NaiHum)

Strontium
•Sulphur

Tantalum
Tdlurittffi

Terbium
Thallium

Thorium

Thulium
•Tin {Stannum)

Titanium
TttDstten

(Wotframtum)

Symbol

Atomic
Weight

Naturs

78.87

A non-metallic
toUd.

a8.4

A non-metallic
solid substance that
occurs in both crys-
talline and amor-

107.66

A lustrous white
metal.

33.05

A soft alkali metal
that resembles potas-
sium.

87.6

An alkaline earth.

32,60

A paie*yellow crys-
talline solid.

Z83.0

A black Mwder-
like solid.

125.0

A silver-colored

IS9.0

• • •

204.1

A soft white metal
bel6nKing to the
same class as alumin-
ium.

231.9

A gray metallic
powder of the nature

of cerium. (Oxids

of these two elements

are used in the pre-

paration of Welsbach
mantles, becaiue of
the intense light giv-
en out by a mixture
of these oxids when
they are hieated.)

171.O

• . .

II9.O

A soft metal that
melts at about 235*
P. and is very mal-
leable.

48. z
Z84.0

Resembles silicon.

A very hard, brit-

tle, nearly infusible

metal.

Whskb Found
IN Natu&b

In some minerali
and sulphur.

Next to oxygen, sili-
con is the most abun-
dant element in na-
ture; it is never found
free, but its com-
pounds constitute a
large portion of the
earth's crust. It is
senerally prepared
from quarts.

Free and in many
ores.

It is never found
free, but its com-
pounds are numerous
and widely distri-
buted. They occur in
rocks, sea-water, salt
deposits, and organic
matter.

^ In the metals stron-
tianite and celestite.

Free, especially in
the neighborhood of
volcanoes, and in the
form of sulphates and
sulphids in a variety
of minerals and many
organic substances.
In a few mineriUs.

In a few minerals.

In many ores, in the
minerals known at
p^ites, and in com-
bination with sulphur.

In a few rare min-
erals.

In a few rare min*
erals.

It occurs chiefly at
the oxid called cassi»
teriU or Hnstont,

In soil and rocks.

Chiefly as ferrous
tungstate in the mia*
eral wolf raa.

Nature of Matter and its Elements 35

Element

Symbol

Atomic
Weight

Natukb

Whssb Found
IN Natuue

Uranium

238.5

A rare metal be-
longing to the same
dasB as tungsten.

A crystalline me-

In pttchblend and a
few minerals.

Vandium

St.7

In a few minerals.

tallic substance.

Victorittin

Metal.

In earth.

Xenon

Z3(t.O

Gas.

In the air.

Ytterbium

172.6

A solid substance.

In a few minerals.

Yttrium

89-0

An earth metal.

In a few minerals.

♦Zinc

65.4

A heavy bluish
metal.

In a few ores.

Zirconium

90.6

A solid that occurs
in both crystalline
and amorphous
forms.

In a few rare min-
erals.

Physical and chemical changes. — Eveiywhere in
nature change is constantly taking place. Matter
is being continuously broken down, complex sub-
stances reduced to simple ones, and these simple sub-
stances are as constantly being built up, sometimes
into very different combinations from their original
form. All life and growth are dependent upon such
changes. According to their nature these changes
are classed as physical and chemical; physical changes
being those which do not affect the identity of the
substance and chemical changes those which do alter
its composition. Chemical changes are usually ac-
companied by ph3^ical, either as a cause or effect.
When cane sugar is dissolved in water, a physical
change has taken place, because if the water is evap-
orated, the sugar will be obtained in the same form
as it was originally, but, if cane sugar is boiled with
acid, it will be changed to quite a different substance,
viz., glucose; this, therefore, is a chemical change.
The freezing and vaporization of water are physical
changes, because if the ice is melted or the steam con-
dense, water, similar to that frozen or vaporized,
will be obtained. If a substance (e. g.^ a piece of

36 Physics and Chemistry

wood) is btimed, a chemical change is perpetrated,
for by no known means can the ashes which remain
and the gases which have passed into space be put
together again to form a piece of wood like unto that
which was burned.

Physical or mechanical mixtures and chemical
compounds. — ^When two or more substances of a
different nature are mixed together, but do not enter
into direct combination with, or change the nature of »
each other, the mass is called a mechanical mixture^
but when the substances combine, forming matter
of a different nature, the result is known as a chemical
compound.

Chemical aflinity. Cohesion, Adhesion. — One
cause for both the stability and change of matter
is chemical affinity. By this is meant the attraction
that certain elements have for one another which causes
them to combine, and which holds them together when
combined. The reason for this attraction has not been
proved, but it is thought that it may be at least
partly due to electrical charges. This will be further
discussed in Chapter X. In physics, the attraction
which holds molecules of a like nature together is
spoken of as cohesion and that which holds substances
of tmlike character together is called adhesion.

Surface tension. — ^The predominating reason for
such phenomena as the spherical shape of drops of
liquid and the separation of immiscible liquids, as oil
and water, is the cohesive force of the molecules of the
liquids which draws them together. When manifest
in such ways it is known as surface tension.

CHAPTER III

ENBKGY, H£AT, AND PRESSURB

DefimtttQ of Hypothesis, Hwoiy, Latv^WKat is Meant by
EDexcr-Bffects ol Heat— Different Ways in which Heat it
Transmitted — Difference between Amount and Degree oC
Heat— Heat Units— Specific Heat— Latent Heat— Heat o!
Posion— Rdation o£ Pressure and Heat — ^Atmospheric
Pressure— The Effect o£ Pressure upon the Boiling Point
of Liquids— The Effect of the Specific Gravity of Liquids
i;qx3n their BoiLing Point.

The changes that occur in nature, either chemical
or physical, are not carried on in a haphasard manner,
but are controlled by absolute, often unalterable,
forces. In referring to or describing these forces of
nature, the scientist often speaks of them as laws.
There are, in fact, three words often used by scientists
in this connection, viz., hypothesis ^ theory ^ law.

Definitions of above terms. — An hypothesis is
sometimes defined as a suggestion^ the truth of which
has not been proved, that is advanced as a reason
for, or as a cause of, some fact or law. An hypothesis
is also often spoken of as a working theory, because
an unproved suggestion or idea of what may bo the
cause for certain effects — in other words an hypothe*
sis — is often the first step in the work of discover-
ing hidden forces of nature or of the application of
these forces to practical inventions. By theory is

38 Physics and Chemistry

meant a long-standing hypothesis for phenomena that
accounts jot them so satisfactorily thai it seems to be
true, though its validity ha^ never been proved. When
a theory has been tested in every known way and is
proven to be invariably accurate it is called a law.

The following laws and hypotheses, which are a
few of those frequently referred to in physics and
chemistry, will be often alluded to in this or following
chapters.

Atomic hypotheses. — (i) All elements are made up
of minute, independent particles called atoms, (2)
All atoms of the same kind of element are alike,
atoms of different kinds of elements are different.
(3) All atoms combine by wholes to form compotmds;
atoms are never divided in chemical reactions.

Law of definite composition. — The composition
of chemical compounds is not altered by changes in
their phsrsical state; e. g,, water, whether it exists in
liquid, solid» or gaseous form, consists of H^O.

Law of the conservation of energy. — Energy can
be changed from one form to another, but it cannot
be either created or destroyed. For example, radiant
energy from the sun produces chemical energy in
plants which causes them to grow. This energy,
which binds the atoms of the plant constituents
together, remains locked in the molecules and is
known as latent or potential energy, but, when the
plants are used for food, the energy is liberated from
as much of their substance as is oxidized in the body
tissues and appears in the form of heat energy and
mechanical energy. Or, for another example, the
plants that have decayed and in the cotirse of time
turned to coal, contain, stored in their substance, the
energy, derived from the sun, which furthered their

Energy, Heat, and Pressure 39

growth, and when the coal is set on fire this stored
energy is transformed into heat, light, or electrical
energy; and though energy thus used may seem to
have come to an end, it has simply assumed some
other form and exists somewhere. Thus the amotmt
of energy in the universe remains unchanged.

Law of the conservation of matter. — Matter can
be changed from one form to another, but it cannot
be either created or destroyed. For example, a
house may be burned, but the elements composing it
are still in existence, some in the fonn of ashes, some
as gases that have passed into space. The oxygen
of the air, which maintained the combustion, united
with some of the carbon and hydrogen in the burning
matter, forming thereby carbon dioxid (CO a) and
water (HaO) ; this will be absorbed by plants and by
them changed to the substances they need for their
growth, and while doing this they will give off oxygen
and thus the oxygen will be returned to the air once
more. If the plants die, the elements of which they
are composed may be scattered, but they will still
exist.

Laws of boiling. — (i) Under a given pressure, every
liquid has a definite boiling point; for example water
boils at 100^ C, alcohol boils at 80® C, mercury
boils at 350^ C. (2) When the boiling point is reached
the temperature remains constant unless the pressure
is increased.

Law of Boyle. — ^The volume of a gas varies inversely
with the pressure that is put upon it; i. ^., when a gas
is under heavy pressure, it will occupy but a small
space, but when pressure is released, the gas will
expand and thus increase its volume.

Law of Charles* — ^Every true gas expands -^ of its

40 Physics and Chemistry

volume^or each degree centigrade that its temperatare
is increased and it contracts rkr of its volume for
each degree centigrade that its temperature falls.

Laws of liquid pressure. — (i) Pressure in liquids
is proportional to the depth alone and is not influenced
by the size or shape of the vessels which contain
them. (2) At any given depth the pressure is equal
in all directions.

Laws of pressure in gases. — (i) Pressure in gases
increases with depth, but is not proportional to it.
(2) At any given depth the pressure is equal in all
directions.

Difference between the use of the terms gas and
vapor. — ^The word gas is usually applied to matter
like nitrogen, oxygen, and hydrogen which can be
liquefied only under high pressure, and the term vapor
is used to express the gaseous state of matter that is
liquid under ordinary conditions, e. g., water, alcohol,
ether. The term aqueous vapor is often applied to
vapor derived from water. Vapors and gases are
governed by the same laws.

Energy

By energy is meant the power to produce motion^ or,
in other words, the power to perform work. Energy
manifests itself in several forms, — ^for example, we have
heat, light, mechanical energy, electrical energy, and
chemical energy, — and one form can be made to produce
another form, or, in the words of the law of the conser-
vation of energy, energy can be changed from one
form to another. Heat, for example, or chemical
action can be made to produce an electric current and
an electric current will produce heat and promote
chemical activity in matter.

Energy, Heat, and Pressure 41

When a body is at work its energy is spoken of as
kinetic energy (from the Greek kinema — motion).
When a substance containing the power of work within
itself or of causing motion in other matter is appar-
ently at rest, its power is spoken of as kUerU or potential
energy.

A body possesses energy only because it has re-
ceived energy in some form and it possesses only
as much as it has received. Nearly all the available
energy upon earth is derived primarily from the sun.
The most obvious example of the sun as a source of
energy is that given under the law of the conservation
of energy. As there stated, the sun provides the
energy which causes plants to grow, and plants pass this
energy on to man and other animals who use plants
as food, or when substances derived from plants, as
wood, coal, etc., are burned the energy they liberate
is used to run machinery, produce electric currents
or perform other work. Other examples of the sun as
a source of energy will be seen in the sections on
radiation and reflection.

Heat

As can be seen in the laws and hypotheses on page
39, heat and pressure are two important factors in
causing changes in matter.

Definition. — Physics and physiology give somewhat
different definitions for the term heat. A definition
given in physics is the molecular motion of a body,
for heat is due to the vibration of the molectiles of
matter, and the greater the degree of vibration, the
more intense the heat, and, conversely, the more
intense the heat, the more rapid the motion. It is
because heat increases molecular motion that it

42 Physics and Chemistry

changes the state of matter, for when moleculax
motion increases it may overcome the cohesive
force of the molecules which holds them together. A
definition in physiology is the sensation perceived upon
contact with hot matter due to the stimulation of certain
nerve endings by the rapidly moving molecules of nuUter.
The difference is in description, not in heat.

Sources of heat. — ^These are (i) the sun; (2) chemi-
cal energy, e. g., the heat produced (a) by combus-
tion, (b) by the oxidation that goes on within the
body and other forms of slow oxidation, (c) the heat
evolved during certain chemical reactions, as the
slaking of lime ; (3) electrical energy; (4) mechanical
energy, e. g., (a) friction (machinery, for instance,
becomes hot while working when its parts rub upon
one another, thus causing friction), (b) percussion
{e. g., when a nail is hammered, both nail and
hammer become hot) ; (5) pressure, see page 48.

Experiment 4. Object, to show the rapidity with
which heat can be produced by chemical reactions.

(a) Add some sulphuric acid to about four drams
of cold water and keep a thermometer in the beaker
while doing so and for a short time afterward. Note
the temperature.

(b) Add water to some quicklime and note the
temperattu^ while the lime is slaking.

Effects of heat — ^The more important effects of heat
are: (i) Change of size — ^heat expands matter; (2)
change of state — e. g., ice is melted, water is vaporized ;
(3) change of temperature; (4) chemical change —
e. g.f sugar is changed to caramel, glucose, etc.; (5)
electric change — e, g., the production of an electric
current by the heating of two different metals at
their jimction.

Energy, Heat, and Pressure 43

How heat is transmitted. — The way in which heat
is transmitted from one place or body to another
depends upon the form of matter transferring the
heat. Thus heat passes through solids by the pro-
cess known as conduction; it is transmitted through
liquids, mainly, by the process of convection, and
through the ether by radiation.

Difference between fiie amount and degree of
heat. — ^The amount of heat in a body and the degree
of heat of a body, or in other words the temperature
of a body, are not dependent upon each other; e. g,,
the temperature of 8 ounces of boiling water will be
the same as that of 2000 ounces of boiling water, but
there will be a much larger amount of heat in the
vessel containing the 2000 ounces than in that holding
the 8 ounces. The degree of heat of a body is ascer-
tained by the thermometer and is recorded in degrees;
the amount of heat in matter is ascertained by the
use of a calorimeter and recorded in calories — a calory
being the amount of heat necessary to raise i gram
of water i degree centigrade, or what is known as the
large calory, i kilogram of water i degree centigrade.
The calory is spoken of as the heat unit. In Great
Britain the amount of heat is often recorded in what
is called the British Thermal Unit or B. T. U. By a
B. T. U. is understood the amount of heat required
to raise the temperature of i pound of water i degree
Fahrenheit. A large calory is about the equivalent
of 4 B. T. U.

Spedflc heat. — By this is meant the amount of heat
which is required to raise the temperature of a given
amount of any substance I degree centigrade (or any
other degree taken as a standard) 05 compared with
that required to raise an equal quantity of water to the

44 Physics and Chemistry

same temperature. It requires i calory of heat to
raise the temperature of i gram of water i degree
centigrade; therefore the specific heat of water is
said to be I. The specific heat of the majority of
substances is less than that of water. As a rule the
denser a substance is, the lower its specific heat; i. e.f
it takes less heat to raise its temperature. Thus:

The specific heat of gold is 0.032

copper is 0.093

«l

gla^ is 0.19

earth is 0.2

««

air is 0.237

steam is 0480

ice is 0.504

alcohol is 0.604

water is i.

hydrogen is 3409

In some connections, the specific heat of substances
is often spoken of as their heat capacity as it practi-
cally signifies the capacity that they have for
absorbing heat.

Value of high heat capacity of water. — ^The large
amount of heat that water can absorb and the slow-
ness with which it parts with its absorbed heat is of
great value to man. For instance, the land by the
seashore becomes hot quicker and to a greater degree
than the water while the sun is shining upon them, but
the land parts with its heat more rapidly and becomes
cooler than the water during the night. This, as
will be seen in the section on convection, gives rise
to the breezes that constitute one reason for the more
even temperature and the greater coolness in summer
of countries near large bodies of water than those of
the same latitude in the interior. Another reason

Energy, Heat, and Pressure 45

for this is that, during the summer, the water of the
oceans and large rivers and lakes, etc., is constantly
absorbing heat which in winter unless frozen it slowly
parts with.

Conmion uses to which the capacity of water to
absorb and part with a large amount of heat is put is
the use of steam and hot water for heating houses,
the use of hot-water bags, and the like.

Relative heat of bodies. — The relative heat of
different kinds of matter cannot be alwa3rs judged by
touching substances, because the degree of the sensa-
tion of heat experienced depends not only upon the
degree of heat in the substance, but also upon the
speed with which it absorbs and parts with heat when
in contact with the hand; e. £., if a piece of iron and a
piece of wood are heated to the same temperature,
the iron will seem hotter to the touch than the wood
because it gives up its heat more readily, but if the
iron and wood are both equally cold, the iron will feel
colder than the wood, because iron absorbs heat more
rapidly than wood and will take heat from the hand.

Latent heat« The heat of fusion* — The examples
usually used to explain latent heat are the liquefaction
of solids and the vaporization of liquids. When pieces
of ice are heated their temperature rises until o^ C.
(32^ F.) is reached, then the ice begins to melt and
its temperature does not increase until the melting
is accomplished because the heat is used to overcome
the cohesion of the molecules of the matter and to
move them apart, this being necessary for melting.
Heat absorbed in this fashion without causing rise
of temperature is said to be UUent and that used for
the liquefaction of solids is often spoken of as the
heat effusion.

46 Physics and Chemistry

Heat is always necessary for the liquefaction of
solids, but the amount of heat required varies with
different kinds of solids. It requires 80 calories of
heat to melt i gram of ice at o^ C. without raising the
temperature.

The latent heat of steam. — ^As stated under the
laws of boiling, when water reaches a temperature of
100® C. (212® F.) the temperature ceases to rise unless
the steam is put under pressure. One reason for this
will be found on page 51; another reason is that at
100® C. water is converted into steam — i. c, vapor-
ized — ^and heat is required to further the process. It
requires 536 calories of heat to change i gram of water
into steam. In other words a gram of water must absorb
the amotmt of heat reckoned as 536 calories, or a liter
of water 537,000 calories, before it will be vaporiased.

Why the heat used for the fusion of solids and the
vaporization of liquids is said to be latent — ^When the
term latent was first applied to the heat used to cause
fusion or vaporization, heat was thought to be a
weightless fluid that disappeared in matter dtiring
liquefaction or vaporization and passed out once
more when the liquid solidified or the vapor condensed.
It is now known, however, that not only was this
conception of heat wrong, but that, though the heat
is not raising the temperature of the water, it is not
quiescent, for it is at work increasing the molecular
motion of the matter, thus breaking the cohesion that
holds the molecules together, causing them to separate
and keeping them apart. It will be remembered
that cohesive force is stronger in solids than in liquids
and that it does not exist in gases. As heat used in
liquefying and vaporizing is doing work, the terms
heat of fusion and heal of vaporization arc now con-

Energy, Heat, and Pressure 47

sidered more accurate than the expression UUerU heat,
though this latter term is still much used.

Recovery of the heat of fusion} etc. — ^Just as much
heat as is used in matter in promoting the molecular
motion that causes the changes described in the pre-
ceding paragraph passes from the matter as it resumes
its original form; thus, for every gram of water that
freezes, 80 calories are liberated, and for every gram
of steam that is condensed, 536 calories are set free.

How water, cream, etc., are cooled by melting ice. —
When ice is put into a pitcher of water, it cools the
latter not only because the ice and the water from it
are colder than the water in the pitcher, but because
the ice takes the heat it needs for melting from the
water. In making ice cream, etc., the cream is frozen
because the ice takes the heat it needs for melting
from the freezer and its contents. Salt is added to
the ice because it hastens the freezing in several ways:
(i) It hastens the melting of the ice, because the
salt molecules attract the ice molecules and this helps
in the separation of molecides th^t is essential for
liquefaction, and the quicker liquefaction occurs, the
more rapidly will heat be taken. (2) The salt, being
soluble in water, absorbs the latter and takes the heat
it requires for the process from the cream, etc. (3)
The lowest temperature of unfrozen water is 32® P.,
that of an unfrozen, saturated salt solution is about
6** P. ; thus the brine produced as the ice and salt melt
is much colder than the water of melted ice would be.

The greater the amount of salt used, the quicker
the cream will be frozen, but if it is frozen very
quickly, it will be of a coarse, granular texture. The
usual proportion of salt to ice used is one part salt to
three of ice.

48 Physics and Chemistry

Some other practical applications to which the
reqtiirement of heat for fusion and vaporization are
put will be given in the sections on evaporation and
condensation.

Pressure in Gases

How pressure is increased. — ^To understand how
gases and vapors can be made to produce increase of
pressure, it is necessary to realize that the molecules of
which matter is composed are not» even in solids,
packed excessively tightly together and that the tight*
ness with which they are packed is less in liquids than
in solids, while gas molecules tend to separate and fly
apart. Another point to remember is that molecular
motion is increased by heat and lessened by cold.

Bearing these things in nund, it can be realized
that when a gas is restricted within a given space,
the moving molecules strike and cause pressure against
each other and against the walls of the vessel confining
them: If the space is large in comparison to the amount
of gas present the pressure will be slight, but if, by
any means, the size of the space is lessened, the moving
molecules will come more in contact with each other
and the sides of the vessel and thus produce increased
friction. If the gas is heated, the movement and
consequently the friction and pressure will be still
further increased, and the friction will increase the
heat. Thus pressure produces heat and heat produces
pressure

Comparative relation of pressure and heat. — ^When
steam, for example, is put under pressure, as in an
autoclave, there is a definite relationship between the
amount of pressure exerted and the degree of heat
obtained. The amount of pressure exerted is usually

Enei^, Heat, and Pressure 49

expressed as being so many pounds to the square inch
of soifaoe exposed to the pressuie. The approximate
comparative relation c£ the amount of pressure and
degree of heat can be seen in the following table':

Pounds pxcssoxe to -
the sqaaie inch Teoipeimtiife

I loa* C

5 108* •*

! 10 115.6* •*

15 iai4* "

20 126^* "

30 I34-6* "

In some strongly constructed boilers a pressure of
even 200 pounds to the square inch can be obtained;
in fact, so great is the pressure exerted by steam » even
exceedingly strong boilers can be shattered by al-
lowing the temperature to increase* and thus raising
the pressure, above the degree that the boiler was
constructed to stand.

Atmospheric pressure. — Since the pressure of gases
increases with depth, the pressure of the atmosphere
is greater at sea level than in high mountains. At a
height of three miles, the pressure is only about one
half that exerted at sea level. Below sea-level, the
air increases rapidly in density and, therefore, it
naturally exerts much greater pressure. It is esti-
mated that thirty-five miles below the sea the pressure
must be a thousand times greater than that at the
earth's surface.

The barometer. — Torricelli, an Italian physicist, was
the first individual to measure atmospheric pressure.

> It will be remembered that steam not tmder pressure has the
same temperatore as boiling water, i, «., loo* C, or 212* P.

50 Physics and Chemistry

He took a glass tube, about one meter in length and
five millimeters in diameter, closed it at one end, and
completely filled it with mercury. Then, putting
his finger over the opening, he inverted that end of
the tube into a pan containing mercury. Then he
withdrew his finger and found that the mercury re-
mained at a considerable height in the tube. This,
by other experiments, he proved to be due to the
pressure of the air upon the surface of the mercury
in the dish.

A common form of barometer is now constructed
on the same principle as the Torricellian experiment.
It consists of a mounted tube at the lower end of which
is a bulb or crook of exceedingly thin glass for the
mercury reservoir. The pressure of air upon this
causes the mercury to rise 760 mm. in the tube when
the barometer is at sea level and the temperature at
zero centigrade (i. ^., 32® F.). Calculations that need
not be given here show that if the mercury is raised
to 760 mm. (or as it is sometimes expressed 76 cm.)
in the tube, the atmospheric pressure is fifteen pounds
to the square inch at sea level, when the temperature
is zero centigrade.

Common causes other than altitude that produce
changes in atmospheric pressure. — Disturbances in
the atmosphere, such as those produced by variations
in temperature, winds, and humidity alter the degree
of pressure in a locality. Heat reduces pressure be-
cause it causes increased movement and expansion of
the air, thus making it less dense. When pressure is
thus reduced, currents of air from cooler regions pass
in; if they do so quickly, there is a wind; if there is
much humidity in the air, the cool currents will cause
the vapor to condense and there will be rain or snow,

Energy, Heat, and Pressure 51

etc. Aqueous vapor is lighter than dty ain When
the atoaospheric pressure is low, the mercury in the |
barometer tails. These facts show why a falling f
mercury is looked upon as presaging a storm«

Effect of pressure upon boiling point Nature of
boiling. — A liquid is said to be boiling when bnbblos
of \-apor f<MTn within it. Bubbles cannot forhi in a
liquid while the atmospheric pressure at the surf4ux>
is greater than that of the vapor as there is no nx)m
for their expansion, but the pressure of the vai)or that
is formed from the water increases as its tem{)eratun'
rises because its molecular motion increases and whon
a temperature of loo® C. (212** P.) is reached* if the
liquid is water, the pressure of the vapor is as grt^at
as that of the air on the surface and the bubbles rise
to the top. After a liquid begins to bubble its toni-
perature cannot rise higher imlcss the steam is put
under pressure for the reason given on page 46» and
because the bubbles increase the surface at which
evaporation takes place and this causes loss of heat*
Consequently, to make water boil violently is simply
a waste of fuel, for the larger the bubbles, the greater
the loss of heat by evaporation and thus there is no
rise of temperature. The temperature of flowing
steam (i. e,^ that not under pressure) is the same as
that of boiling water.

Experiment 5. Object, to show the effect of at-
mospheric pressure upon boiling point.

Articles required: A flask about half full of water,
a cork with one hole in it — ^the cork must fit the bottle
perfectly, — a thermometer that will fit into the hole
in the cork, a Bunsen burner, an iron stand, wire net-
ting, a towel, and, unless the cold water faucet is in
a good light, a pitcher of cold water and a basin.

Physics and Chemistry

Procedure: Boil the water in the flask for about
ten minutes, then put the cork, with the thermometer
in the hole (the thermometer must extend into the

water), into the
fiBsky and at once
turn out the
light, grasp the
upper part o f
the neck of the
flask with the
folded towel and
run cold water
over the upper
part of the flask,
above, not over,
the part con-
taining the wat-
er. See Fig. 39.
Watch the ther-
mometer.

Fig. 39. Manner of Pouring Cold

Water Run over Flask in Order

TO Reduce the Pressure above

THE Water within it.

What happens?

Why?

Endeavor to answer these questions before reading
the following paragraph.

Explanation of experiment The air in the flask
was heated, as well as the water, while the latter was
boiling, therefore it expanded and, consequently,
passed from the flask and its place was taken by the
steam produced as the water boiled. When the flask
was held under the cold water, the steam was con-
densed and thus there was a partial vacutun above
the water; this being the case, the pressure was, of
course, reduced and the vapor, having less pressure
to overcome, bubbled at a lower temperature.

Energy, Heat, and Pressure 53

It is because the pressure on high mountains is less
than at sea level that water boils there at a lower
temperature than it does in lower altitudes. At the
top of Mount Blanc, water boils at 84® C.

Why pressure makes it possible for some bodies to
float — Due to the fact that the pressurQ.pf ibqtdds is
equal in all directions, upwards as well as downwards,
any body that does not weigh more than the amount
of liquid which it displaces will float since its weight
is not more than that of the amount of liquid that
would otherwise have been in that part.

The nature of specific gravity or density and its
influence on floating bodies. — First what is specific
gravity or density? These two words are used inter- )
changeably to signify the weight of a substance asi'
compared with that of another substance which isj
taken as a standard. Distilled water is the standard
usually employed, especially for liquids. A liquid in
which solids heavier than water are in solution or
suspension will, of course, have a higher specific
gravity than water. Naturally, the greater the den-
sity of the liquid, the heavier the body that will be
able to float in it. It is impossible for people to sink
in the Great Salt Lake of Utah.

How the specific gravity of liquids is ascertained. —
The specific gravity of such liquids as water, milk,
sugar solutions, acids, urine, blood, and the like is
usually gaged with a hydrometer. This consists of a
glass cylinder on one end of which is a bulb containing
mercury or shot and on the other a slender stem within
which is a scale (see Fig. 23). The scale varies slightly
in different forms of hydrometer. The scale of an
instrument intended for measuring the density of
liquids lighter than water is usually marked in such

54 Physics and Chemistry

a manner that when the instrument is put into dis-
tilled water, it sinks until the mark i is on a line with
the water, and when put into pure alcohol, it sinks
until the mark loo is reached. The scale of another
variety of hydrometer is marked so that the instru-
ment will sink to I in distilled water and the markings
above the i indicate weights less than i and those
below that point show densities greater than that of
water. Thus the instrument will not sink to as great
an extent in milk, blood, and other dense liquids as
in water. The principle involved is that a floating
body sinks until it displaces its own weight. Deter-
mination of the sp. g. of a liquid is of value in testing
for its purity.

Experiment 6. Object, to show the effect of spe-
cific gravity on the boiling point of liquids.

Procedure: (a) Ascertain the specific gravity of
tap water, boil, and notice the temperature at which
boiling occurs, (b) Add three tablespoonfuls of salt
to the water, cool, ascertain the sp.g., boil, and note
the temperature at which boiling occurs, (c) Take
equal parts of water and alcohol, find the sp.g., boil,
and note the temperature.

Prom this experiment it can be realized that liquids
with a lower sp.g. than water boil before the tempera-
ture reaches loo® C, while those of greater density
than water have a higher boiling point than the latter.
For example:

The boiling point of ether is 37*C.

" "alcohol 95% 79"

" " water loo "

" " " " spts. of turpentine. . 130 "

" " phosphorus 290 "

M " •• " mercury 357 "

CHAPTER IV

SOlfE COIOCON PHYSICAL PROCESSES AND THEIR

RESULTS

Evi^mratioii — Condensatkm — ^Humidity — Dew — Fog — Frost-
Rain — ^Hail — Snow — ^Artificial Ice — ^Distillation — Sublima-
tion — ^Diffttaon — Osmosis — Dialysis

Evapormtioii compared with vaporizatioii. — Evapo-
ration, like vaporization, is a process in which liquids
pass to a gaseous state, but the term vaporization is
used when the formation of vapor takes place through-
out the entire mass of the liquid and evaporation when
it occurs only at the surface of the liquid. In order
for vaporization to occur, a liquid must be heated to
its boiling temperature, evaporation takes place to
some extent at all temperatures, but is, of course, in-
creased by a high temperature.

Why evaporation takes place. — ^As the molecules
composing a liquid are in constant motion and their
attraction for each other, which holds them together,
is only fairly strong, some of the molecules at the sur-
face escape from the liquid into the air. Many of
these are drawn back again by the attraction of the
molecules at the surface, but more molecules escape
than fall back and thus after a time all the molecules
of the liquid escape and move more quickly and fly
apart and thtis become gaseous.
• k 55

56 Physics and Chemistry

' Factors which influence the rate of evaporation. —

Important factors in influendng the rate of evapora-
tion are: (i) The nature of the liquid. To see this»
expose in separate dishes a little water, alcohol, and
ether. It will be seen that the liquids which have the
lowest boiling point evaporate the quickest. (2) The
temperature of the liquid. Heating a liquid, by increas-
ing the rate of molecular motion, hastens evaporation.
(3) The amount of surface exposed. Evaporation
takes place from the surface of a liquid, consequently,
the greater the extent of free surface, the more rapid
the rate of evaporation. (4) Pressure. In order to
pass into the air, the molecules from a liquid must
overcome the pressure of the air upon the surface of the
liquid, if therefore there is no air, as in a vacuum,
evaporation will occur much more rapidly at a low tem-
perature than under ordinary circumstances. For this
reason, vaccutun pans are used in the preparation of
condensed milk, much of the nutrient of which is lost
if it is subjected to a high temperature. (5) The
amount of vapor already in the air, i. e., the degree of
humidity under ordinary conditions of temperature
and pressure, the atmosphere can hold only a certain
amount of vapor; for this reason, evaporation will not
take place as quickly on a damp, as on a dry, day; e. g.,
wet dothes dry more slowly on a damp day. (6) The
rapidity with which moist air is driven away from
around the evaporating liquid — e. g., on a windy day,
clothes will dry more quickly than when there is no
wind, and fanning a moist surface hastens its dr}dng.
Result of ev^K)ration on temperature. — ^A surface
from which evaporation takes place and the air arotind
it are cooled by evaporation. Thtis the air is cooled
after rain while the moisture is evaporating. The

Physical Processes and their Results 57

evaporation of sweat from the stirface of the body is
one of nature's principal means of preventing body
temperature becoming too high, and bathing the body
with water or alcohol while exposed to the air, so
that evaporation will take place rapidly, is a means
often employed for reducing body temperature in
fever. As stated, page 51 , it is due to evaporation that
the temperature of boiling water remains at 212^ F.
and it is because of the evaporation of water in the
lower part of a double boiler that the temperature of
food in the upper part keeps relatively low.

Why evqK)ration causes cold. — One reason for this
is that it is the hottest molecules that move the fastest
and consequently it is the hottest ones that escape
first into the air. Another cause is that mentioned
under vaporization, viz., liquids must have heat in
order to become vaporized and they take it from the
most available source.

Liquids, such as ether and alcohol, which evaporate
more rapidly than water create a greater degree of
coolness than the latter during evaporation since the
wanner molecules escape more rapidly, and, also, a defi-
nite amount of heat being required to produce evapor-
ation, the more rapidly the work is accomplished, the
more rapidly the heat will be taken. Certain sub-
stances, as ethyl chlorid, which evaporate very quickly
win, if sprayed on a part of the body, cause it to freeze
in a few seconds.

Evaporation of solids. — ^As a rule, solids become
liquefied before being vaporized, but there are a few
solids that will pass into a gaseous state and disappear
without forming any visible vapor. For example,
wet clothes that are htmg out in winter and become
frozen will lose the ice that formed upon them and

58 Physics and Chemistry

become qtiite dry, though the temperature is too low
for actual melting to have occurred. Also certain
solids, such as camphor, will volatilize and, disappear
without apparently liquef3dng. A few other solids,
such as arsenic and iodin, will, if heated, be converted
at once into vapor. Iodin so treated is called re-
sublimed iodin. (See page 65.)

Condensation

Nature and cause of condensation. — Condensation
is the process by which gaseous matter is changed to
liquid and the changes that occur are exactly the
opposite of those which take place in vaporization;
viz., due to the application of cold, molecular motion
becomes less and less, the particles become packed
closer together, and the heat of vaporization which was
employed in keeping them apart passes from the
matter.

A common use of the heat given off in condensation.
— Heating houses by steam is a common use to which
the heat given off in condensation is put. The steam
generated in a boiler passes through the pipes with
which the rooms are supplied and there condenses ; thus
the pipes, which radiate the heat they receive to the
room, are heated, not only by contact with the hot
steam, but also with the heat liberated during con-
densation. The water thus formed passes through
pipes provided for the purpose, back to the boiler
where it is once more converted into steam.

Liquefied gases. — ^Aqueous or water vapor is as
easily changed to water as water is to vapor, but gases
such as oxygen and hydrogen can be liquefied only at
extremely low temperatures and under great pressure,
and, as soon as the pressure is released, the liquid

Physical Processes and their Results 59

expands and the natural form of the gas is sesumed.
Such volatilizing matter takes the heat that it re-
quires for the process from anything with which it
comes in contact; for this reason, men, who have not
taken proper precautions, have had their hands frozen
while repairing tanks containing liquefied gases.

Artificial ice. — The use of ammonia in the making of
ice is a common practical application of the alter-
nate condensation of gas and vaporization of the
liqmd obtained by condensation. Ammonia gas is
generally used for the purpose in preference lo other
gases because it is easily condensed' by pressure at
ordinary temperatures to a liqmd which boils, and
consequently, vaporizes at a low temperature. The
principles of an ice-making machine and the process of
making ice are as follows : There are two large tanks
containing coils of pipes. The coils in the two tanks
are connected by pipes to which a pumping machine
is attached. In one tank ate large cans which are
filled with pure water and surroimded with brine,
this is generally made of calcium chloride or sodium
chlorid and water. The coil in the other tank is
surrounded with water. The ammonia gas is com-
pressed by a compression pump and, as a result of
this process, becomes very hot. This hot compressed
gas is then passed through pipes that, usually, are out
of doors and over which cool water is allowed to run.
This process reduces the temperature of the gas below
its critical temperature (that at which it remains in
gaseous state) and it becomes liquid. The liquid
anmionia, which must not be confused with aqua
ammonia, is carried in small pipes to the tanks of
brine. Here it is passed through a needle valve into a
large pipe. This releases the pressure and allows the

60 Physics and Chemistry

liquid to assume its gaseous state. As has been
previously said, the heat necessary to produce this
change is taken from the surrounding medium, hence
the temperature of the brine is reduced below 32** P
and the water in the cans is frozen. The gas from the
pipes is then passed over the compressors again and
the process is repeated.

t Refrigerators and cold-storage rooms are sometimes
cooled in much the same way as ice is made, the essen-
tial differences being that the cans of water are omitted
from the brine tank and the brine, after being reduced
to a temperature of about 16** P. is pumped into pipes
that extend from the tank to coils of pipes in the
ceilings of the places to be chilled. The brine is kept
in circulation between these pipes and the tank where
it is cooled; thus the pipes are kept constantly cold
and they keep the place in which they are situated
cold in just the same manner as ice would.

The air of cold-storage rooms and theaters is some-
times cooled by forcing evaporating ammonia or
carbon dioxid through pipes within the room. The
principle is the same as in making ice, the essential
difference being that the heat for the volatilization
of the gas is taken from the room instead of from
brine. The pipes in which the volatilization takes
place may become as cold as 6** P.

Humidity

The term humidity is used in referring to the mois-
ture of the atmosphere. The moisture of the atmos-
phere is the result of evaporation from bodies of
water, moist earth, snow, or ice.

When there is as much moisture in the air as the
latter can hold it is said to be saturated. How much
moisture the air can hold without becoming saturated

Physical Processes and their Results 6i

depends upon the temperature. Naturally, as warm
air is expanded and its molecules are thus farther
apart than in cold air, warm air will hold more mois-
ture than cold air without becoming saturated.
Cooling of the air, especially when it is saturated, is
likely to result in condensation of the vapor and con-
sequent forming of dew, fog, rain, etc., which, depend-
ing upon the temperature and where and how the
condensation occurs.

Absolute and relative humidity. — ^By absolute
humidity is meant the amount of aqueous vapor which
the air contains expressed in the number of grams of
moisture per cubic foot, or other specified amount, of
air.^ By relative humidity is tmderstood the amount
of vapor that is present in the air expressed as a per-
centage of the amount that the air will hold without
the moisture being precipitated in the form of dew, rain,
etc. — i, e, without becoming saturated. When air is
saturated, the relative humidity is said to be loo per
cent. How much moisture there can be in the air
without its becoming saturated will, as stated in the
preceding paragraph, depend upon the temperature.

The degree of humidity is ascertained by the use of
an instrument called a hygrometer.

Effect of moisture on comfort and health. — The
estimates given for the most desirable relative degree
of humidity vary between 50 and 70 per cent. A
higher per centage than seventy-five makes both cold
and heat harder to bear, and it, when the temperature
is high, increases the danger of heat prostration and
sunstroke, because, for the reasons given under evapo-
ration, it interferes with the evaporation of sweat from
the body. Very dry air is also exceedingly injurious
for it acts as a mental irritant and it parches the

62 Physics and Chemistry

membranes of the eyes, nose, throat, and lungs, and
thus lays a foundation for catarrh and bacterial infec-
tion. It has been found that steam-heated dwelling
houses often have a relative humidity as low as thirty
per cent, when the hiunidity out of doors is seventy-
five per cent.

A common device to keep the atmosphere of arti-
ficially heated rooms moist is to have bulbs, or other
water plants growing in wide shallow basins of water.
The constant evaporation that occurs helps very
considerably in keeping the air moist.

Nature of dew, frost, fog, clouds, rain, hail, snow. —
When moisture in the air comes in contact with a
surface cooler than the air, the moisture will condense
upon it. The earth, grass, flowers, etc., are likely to
become cooler than the air at night, for though they
absorb heat diuing the day, they radiate it very
quickly after the sun goes down, consequently the
vapor in the atmosphere condenses upon them as
drops of water. This is known as dew.^ When the
cooling that occiurs is so great that not only the ground
and plants, but also the air above them, become colder
than the higher strata of air, the moisture in the colder
portion condenses on all the particles of dust and the
like suspended in the air and the result is known as
fog. Naturally, fogs occur most frequently near large
bodies of water and following days in which heat has
caused a large amount of evaporation or where, as in
parts of California, the hot air of neighboring deserts
becomes so expanded that its pressure is reduced to
such an extent that the moist air from the Pacific,

> The oollectiog of drops of water on the outside of a pitcher
containing ice water, when it is in a warm place, is the result of
the same cause as dew.

Physical Processes and their Results 63

where the presstire is greater is forced in to take the
place of the hot dry air. When this air becomes at all
chilled, the moisture condenses and envelops the land
in mist or fog. Another factor influencing the amount
of fog likely to occur in a place is the amount of dust
for vapor condenses readily upon the chilled dust.

Clouds, like fog, consist of masses of vapor con-
densed into minute droplets, but clouds are higher in
the air.

When the condensation of water in the douds
reaches the point of saturation the water falls upon
the earth in the form of rain imless (i) the tempera-
ture of the air in which the clouds are, is below freez-
ing point, when the water falls as snow or (2) if the
raindrops are whirled by the wind through regions of
different temperatures some of which are below freez-
ing point the drops of water fall as the small balls of
ice known as hail.

Distmatioa

Nature of distillatioiit — If the vapor of a boiling
liquid passes into a tube or pipe and is collected in a
reservoir surrounded with ice as demonstrated in
Fig. 40, the vapor will condense. This process is
known as distillation.

Fractional distillation. — Since, as shown in experi-
ment 6, liquids of different specific gravities have
different boiling points, one with a lower boiling
p>oint than other substances in a compound can be
extracted by keeping the latter at the boiling temper-
ature of the liquid desired. For example, alcohol
can be extracted from water by distillation, if the
solution is kept at 80® C, the boiling point of alcohol.

Physics and Chemistry

The extraction of a Uqtiid from a compound in this
way is spoken of as fractional distillation.
Destructive distOlation. — When certain solid or

Fig. 40. Distillation.
(a) Flask containing 50% Alcohol,
mometer.

(b) Ther.

liquid substances, as coal, wood, and petroletun are
heated in closed vessels out of contact with the air,
they break down into simpler substances some of
which can be easily vaporized, and, therefore, distilled.
This is termed destructive distillation. The term
dry distillation is sometimes used, for destructive dis-
tillation of solid substances.

Physical Processes and their Results 65

Sublimatioii

Nature of sublimatioiL — In the section on the evap-
oration of solids it was stated that there were certain
solids which passed into a gaseous state without
any visible formation of liquid. If the vapor arising
from these substances is collected and condensed it
win solidify. This form of distillation is known as
sublimalian and the condensed products are called
sublimates. Sometimes chemicals that will, when
heated, interact to form new compounds are sublimed
together. This is the manner in which the well-
known disinfectant, bichlorid of mercury is prepared.
The chemicals used in its preparation are mercuric
stdphate (HgS04) and sodium chlorid (NaCl).
When proper proportions of these substances are
heated together, the mercury and chlorin tmite in the
proportion of one part mercury to two parts chlorin
and sublime while the sulphate and the soditim unite
to form a non- volatile, substance — sodium sulphate
— ^which remains behind. Thus HgS04+aNaCl =
NaaS04+HgCla.

Dififusion

Nature of diffusion. — ^When two or more gases that
have no chemical affinity for each other are introduced
into a room, vessel, or other space, the gases quickly
spread and intermingle so that in a short time each
gas is uniformly distributed throughout the whole
space; just as it would be were it the only gas present.
This Spreading of gases is known as the diffusion of
gases.

Common proof of the diffusion of gases. — ^The
f

Physics and Chemistry

rapidity with which odors from strongly scented
matter become distributed is a very common proof
of the diffusion of gases.

Experiment 7. Object, to observe the diffusion of
gases.

Articles required: Two drinking glasses, the same
shape and size, two swabs, a piece of stiff, smooth
paper slightly larger than the open ends of the glasses,
ammonia water (NH4OH) and hydrochloric add
(HCl).
Procedure: Wet the interior of one glass with

ammonia, using a swab for the pur-
pose, and cover the glass with the
paper, swab the inside of the other
glass with hydrochloric add, invert
this glass over the first one and then
remove the paper, being careful not
to separate the glasses while doing so.
It will be noticed that, shortly after
the paper is removed, the glasses
become filled with a white cloud.
This is ammonia chlorid, derived by
the combining of the ammonia gas
from the ammonia water and the
hydrochloric add. ThusNH,+HCl«
NH4CI.

Diffusioii of liquids. — If two liquids,
for example lemon jtiice and water, are put into a glass
they will, after a short time, become thoroughly mixed,
even though they are not stirred. The diffusion of
liquids, however, will not take place as quickly as did
that of the gases, since the molecules of U quids are
not in such rapid movement as those of gases, and
diffudon is dependent upon molecular motion.

Pig. 41.
Glasses in Po*
siTioN FOR Dif-
fusion EXPERI-
IIEMT.

Physical Processes and their Results Gj

Diffusion of solids. — It has been found that if a
mass of lead is placed upon a mass of gold, molecules
of the latter will after a time be found scattered
through the lead. The diffusion of solids, however,
at ordinary temperatures is rare, but it is common
at high temperatures.

The phenomenon of diffusion is considered one of
the strongest proofs of molecular motion.

Osmosis

Nature of osmosis. — ^When matter diffuses through ) •,
a membrane the process is spoken of as osmosisS '
Substances having a crystalline form, as sugar, will
readily go into solution and osmose through mem-
branes, but matter that is colloidal (as glue) or amor-
phous (i. €.y not crystalline, without definite shape)
is not capable of osmosing. It is for this reason that
animal foods, vegetables, and starches
must be digested and thereby made
soluble, before they can be absorbed.

Experiment 8. Object: To study
osmosis.

Articles required: 2 gold-beater's
bags or fish bladders, 2 one-hole rubber
stoppers, 2 pieces of glass tubing of
small caliber (^ inch in diameter)
about 9 inches long, concentrated
sodium chlorid, water, two jars or
wide-necked bottles.

Procedure : Pill a bag with salt solu-
tion, fit a cork, with a glass tube in-
serted in the hole through its center, j^^^ Jith^em-
into the open end of the bag, and tie it brane Bag Se-
in place. Suspend the bag in a jar of cured in Place.

68 Physics and Chemistry

water, as in Fig. 42. Arrange a duplicate apparatus,
but put the sodium chlorid into the jar and the water
into the bag.

After some hours it will be noted that the so-
lution has risen in the tube of apparatus i, show-
ing that water must have enteral the bag, but
that the solution has risen in the jar of apparatus 2,
showing that water has passed from the bag into the
jar.

Experiment 9. Object: Same as experiment 8.

Procedure: Have a carrot, instead of the membrane
bag, and syrup, instead of salt solution. Scoop out
the interior of the carrot, fill the cavity with a thin
syrup; insert the cork with the tube inserted in the
hole through its center at the top of the cavity letting
the tube extend about an inch into the syrup. Sus-
pend the carrot in a jar of water. Some of the syrup
will pass into the water, but a much greater amount
of water will osmose into the syrup; enough, in fact, to
cause the syrup to rise in the tube.

Facts shown by experiments. — ^These experiments
prove that when two solutions of unequal concentra-
tion are separated by a membrane a force is exerted
which causes them to pass through the membrane,
the less concentrated one doing so more readily than
the other. This fact is of interest to nurses who
prepare salt solution for intravenous infusion; for if
too much salt is used (1. e., more than enough to make
the solution stronger than 0.9 per cent.) fluid will be
extracted from blood corpuscles and they will become
shnmken and shriveled. If, on the other hand, the
solution contains too little salt (less than 0.6 per cent.)
it will enter blood corpuscles and cause them to swell
and perhaps rupture. If a little defibrinated blood

Physical Processes and their Results 69

can be obtained from the slaughter house, ' this effect
can be easily demonstrated as follows: Put about 5 cc.
of blood into each of four test tubes, to one of these
tubes add an equal amount of water to another an
equal amount of a 0.2 per cent, salt solution, to the
third physiological salt solution (t. «., 0.9 per cent.)
and to the fourth, add the same quantity of 5 per cent,
salt solution. Notice the difference in the color that
occurs in all the tubes, except that with the phy-
siological salt solution, due to the action of the salt
solution on the blood corpuscles. The disintegration of
the red corpuscles is spoken of as hemolysis and blood
in which hemolysis has occurred is said to be laked.

For further study of the action of liquids of differ-
ent concentration upon the blood, prepare a drop of
the contents of each of the tubes for examination
under the microscope. To do this smear the drop
over the center of a clean glass slide. Place this so
that it can be viewed with the microscope and note
the difference in the shape of the blood-cells in the
different smears.

The blood can be also prepared for examination as
follows: Wash the finger with alcohol, prick it with a
sterile needle, put a drop of blood thus obtained on
each of four sterile slides. To one drop, add a few
drops of water and to each of the others a few drops
of one of the different percentages of salt solution.
Mix the blood and diluent with a platinum tip.

A cause of edema. — ^Another fact of interest to
nurses that the osmosis of fluid towards the location

' WheQ blood is stirred rapidly as soon as it is shed, the fibrin
collects on the stirring implement. Blood thus treated is said
to be delibrinated and it will not clot, for the fibrin^ which has
faeaa removed, is essential for the clotting of blood.

70 Ph3^ics and Chemistry

of the more concentrated solution explains is that,
when the kidneys fail to eliminate salt, as is often the
case when they are diseased, and the salt passes into
the tissues, edema or dropsy results, one reason being
that, on account of the excess amount of salt in the
liquid in the tissues, the passage of fluid from the
blood exceeds its absorption.

Dia^s

Nature and use of dialysis. — Since all substances
cannot pass through animal membranes, chemists
often make ttse of what is known as a dialyter (a jar
with a parchment bottom) to separate non-crystalline
from crystallizable substances when the former are
present in a solution in a finely divided form. The
process is known as dialysis.

CHAPTER V

SOME COMMON PHYSICAL PROCESSES AND THEIR RESULTS

— (ConUnued)

Contraction — ^Expansion — Vacuum — Suction — Siphonage— Cap-
illarity — Conduction — Convection — Some Common Prac-
tical Applications of Knowledge of the Nature and Action
of these Processes.

Contraction and Expansion

It is a well-known fact that even solid substances
are expanded by heat and contracted by cold. For
instance, railroad rails are laid with spaces between
their ends to allow for the expansion that occurs during
the heat of summer; it is difficult when the hands are
hot to put on kid gloves that can be drawn on easily
when the hands are cold. Liquids cannot be expanded
to as great an extent as gases since high degrees of
heat and cold change their state, i. e., change them to
vapor or solid — but that some change is made can be
easily seen if a graduated flask containing water is
held over a flame, for the water will be seen to rise in
the flask. The degree to which gases are expanded
by heat and contracted by cold is stated in the law of
Charles — j4t of their volume for every degree centi-
grade that their temperature changes. The expan-
sion of gases can produce great force as is demonstrated

V 71

72 Physics and Chemistry

by explosions. For example, the dynamite used to
blast out rock, etc., does so because a small amotmt of
solid d3maniite is converted by heat into large quan-
tities of gas which, by the heat produced as the result
of the chemical interaction of the constituents of the
dynamite, becomes very greatly expanded and forces
apart even huge rocks that interfere with its expansion.

Reason for expansion and contraction. — The change
in the size or volume of matter as the result of heating
is due to increase in the velocity of molecular motion
by the heat in consequence of which the molecules
jostle each other farther apart, thus increasing the
voltune of the matter. Cold, on the contrary, lessens
molecular motion and, consequently, contracts the
majority of substances.

Peculiarity of expansion and contraction in water.
— Fortunately for mankind, water, when cooled, does
not act in quite the same way as most substances; it
contracts tmtil a temperature of 4®C. is reached; but
after it attains this temperature, it begins to expand,
and consequently its weight grows less in proportion
to its bulk. For this reason, when ice forms in lakes,
rivers, etc., it floats to the top. If the ice did not do
this, bodies of water would freeze to the bottom and,
if deep, could not be thawed, even in summer.

Why glass and porcelain-ware break when heated
or cooled quickly. — If glass and porcelain utensils
are heated and cooled slowly they will stand wide
variations in temperature without breaking, but, on
the contrary, if they, especially glass ones, are heated
or cooled quickly, particularly if the heat is directed
against one point or if, when hot, they are placed upon
a cold stand, they are Ukely to break. This is because,
in such cases, the expansion or contraction is xmeven

Physical Processes and their Results 73

and a crack occurs where resistance is offered to the
change in condition.

If when pouring a hot liquid into a glass utensil, the
liquid is poured over, as well as into it, there is less
danger of its breaking and thin glass is broken less
readily by heat than thick glass. The reason in both
instances being that all parts of the utensil are brought
more nearly to the same temx)erature at once.

The thermometer. — The thermometer is a practical
application of the expansion and contraction of
liqtiid by heat and cold. A thermometer usually
consists of a glass tube of capillary bore with a bulb
that is filled with mercury at one end. When making
a thermometer, the bulb and part of the tube are
filled with merctiry and the instrument heated until
the mercury boils and expels the air from the tube.
After this the top of the tube is sealed. When the
tube is cold, the bulb is placed in boiling water and
the point to which the mercury rises is marked 212,
if the thermometer is marked with the Fahrenheit
scale, or 100 for the centigrade scale. The bulb is
next placed in a vessel of melting ice and the point at
which the mercury stops is marked 32 for the Fahren-
heit scale and o for the centigmde. The space be-
tween the freezing and boiling points is divided into a
number of equal spaces, the size depending upon the
kind of scale.

Vacuum, Siphonage

Vacuum. — ^By a vacuum is meant a space from
which all air has been exhausted and which contains no
material substance,

A vacuum is usually created by means of some form

74 Physics and Chemistry

of pump, fan, or piston which will by pressure or other
means remove air or other matter from a cavity.

To maintain a vacuum it is necessary that all
apertures to the cavity be absolutely sealed, the
slightest crevice will allow air, etc., to enter because of
(i) the tendency of gases and liquids to diffuse equally
in all directions; (2) the fact that, when a vacuum has
been created within a space or cavity, there is no
pressure within it to oppose the entrance of any form
of matter; (3) the pressure of the atmosphere upon the
matter that is afforded entrance.

The creation of a vacuum, is an essential principle
in the raising of water from a lower to a higher level
and in drawing fluids from and into cavities, it is the
power that is being more and more used for the re-
moval of dirt and dust from buildings and streets. Its
chief values for the latter purpose is that the dust,
etc., are removed without being scattered or inhaled
and, in buildings, carpets and the like are not sub-
jected to the same amount of wear that they are by
other modes of cleaning. The creation of a partial
vacuum is one of the resources utilized in the ventila-
tion and heating of buildings as will be seen in the
section on ventilation.

Siphonage. — If a curved tube with one end longer
than the other is filled with water and this not allowed
to escape until the short end of the tube is inserted in a
pail of water the water will flow from the pail, through
the tube, though at first it must flow upward. Such
forcing of water over an elevation is known as siphon-
age. It is maintained by the pressure of the atmosphere
on the water in the pail and the unbalanced pressure
of the water in the tube. This difference in pressure
is the result of the difference in the length of the two

Physical Processes and their Results 75

arms of the tube and the greater the difference, the
greater will be the pressure and the greater the force
of the flow of water. It is important to remembei
this when using siphonage for therapeutic purposes;
force being sometimes desirable, but often very tm-
desirable.

When a rubber tube is used
if a syringe can be obtained,
the tube can be filled after one
end has been put into the
water, otherwise, a funnel can
be inserted in one end of the
tube and, holding the latter so
that its free end is on a level
with, or a little above, the fun-
nel, as in Fig. 43, the water,
or whatever liquid is required,
poured into the funnel until it
appears at the opening of the ^
free end of the tube. Then,
simultantously, the funnel ts
lowered into the pail of liquid
and the free end of the tube
over the vessel or part into or Pig 43

over which the liquid is to run.

This must be lower than the pail in order to obtain the
necessary unbalanced pressure of water in the tube.
Two necessary precautions are: Not to allow the
water to escape from the tube while inverting it ; to pre-
vent the tube being compressed on the rim of the pail.

Capillarity
Nature of capillari^ and reason for name. — If a

tube of small diameter is placed in a Uquid that will

76 Physics and Chemistry

wet its interior, the liqtiid will rise somewhat higher
in the tube than the level of the liquid on the outside,
and the smaller the diameter of the tube, the
higher the liquid will become. If the tube is placed in
mercury or other liquid that will not wet it, the liquid
will become depressed, rather than elevated. The
force causing a liquid to rise in a tube is known as
capillarity or capillary aUraction (from the Latin
ca/>t7/am= hair-like) because it is only perceptible
in tubes of small diameter.

Cause of capillarity. — The molecules of a liquid
have an attraction for each other which holds them
together (cohesion) and also an attraction for the
molecvdes in the sides of a tube which they wet (ad-
hesion — see page 36). If the force of cohesion is
stronger than that of adhesion the molecules of the
liquid will be pulled down, but when adhesion is the
stronger force the liquid clings to the sides of the glass
and rises in the tube.

It is due to capillarity that oil rises in the lampwick ;
that a piece of muslin or other tubular fibered fabric
will become wet throughout if a small end is left in a
liquid; that gauze in a wound will act as a drain.
Capillarity plays an important part in the flow of sap
through plants and in the distribution of moisture
through the soil.

Conduction

It was stated in a preceding chapter that heat was
transferred from one body or part to another by
either one of the three processes conduction, convec-
tion, or radiation.

The term conduction is used also in connection

Physical Processes and their Results 77

with the transmission of dectricity, nerve impulses,
and sotmd.

Nataxe of conduction. — Conduction as applied to
heat, has been defined as the transfer of molecular
motion from a mass of molecules vibrating with a given
intensity to another nuiss vibrating with less intensity.

Experiment 10. Object, to study the method of
heat conduction.

Procedure: (a) Hold one end of a piece of metal
wire, preferably copper, in a flame. How long can
you hold it thus before the end between your fingers
becomes too hot to hold?

(b) Hold a teaspoon by the handle and keep its
bowl in boiling water. How long does it take for the
handle to become too hot to hold?

(c) Fill, to % its capacity, a large-sized test-tube
with water, hold the tube, at the lower end, in the
fingers and heat the water in the upper part by holding
it in a flame. Notice how much longer it takes for
the water in the bottom of the test-tube and even for
the glass of the tube to become hot than it did for the
wire or the spoon.

(d) Refill the tube with cold water and, holding it
by the upper end keep the lower part in the flame.
Notice what a very much shorter time it takes for the
water to be heated in this way, which is convection,
and not conduction. This will be discussed in the
following section.

Explanation of experiment — The heat of the flame
caused the molecules of matter within it to vibrate
violently and these molecules, by striking against
those in the part of the spoon, wire, etc., held in the
flame, furthered the increase of molecular vibration
that had already been increased by the heat. The

78 Physics and Chemistry

vibration of the molecules in this part of the metal
started those above them vibrating and these set
the masses above them vibrating and so on.

As seen by the experiment, metal is a better con-
ductor of heat than glass or water. This is because
the molecules are packed more closely together in
metal than they are in the other two substances used
and thus they can influence each other more readily.
Metals are the best heat conductors, but all solids
are better than liquids and liquids than gases. The
following table gives the rdative heat-conducting
value of a few common substances. The one having
the highest value is, for convenience, marked loo.

Silver loo Mercuiy 1.7

Copper 74 Granite 0.53

Aluminium 35 Limestone 0.52

Brass 27 Ice 0.21

Zinc 26 Glass 0.2

Tin 15 Water 0.124

Iron 12 Felt 0.038

German silver 84 Air 0.005

A few of the common applications of a knowledge of
the relative heat-conducting power of matter to house-
hold purposes. — A common application of this knowl-
edge is seen in refrigerators, ice-houses, and fireless
cookers. The walls and doors or covers of these
appliances are made with double walls that have a
space between them. The space is filled with air or
other non-conducting matter. An improvised fireless
cooker is sometimes made by taking two boxes, one
considerably smaller than the other, and filling the
space between the two with some such porous, poor
heat-conducting material , as sawdust , wool , or shredded
paper. It must be possible to dose the covers of the

Physical Processes and their Results 79

two boxes securely and a cushion, stuffed with the
same kind of material as that between the boxes, is
placed between the covers. If ice — in a bowl or basin
— is placed in the inner box, the latter can be used as a
refrigerator or if, instead of ice, a covered pot of
boiling food is placed in it, the food will continue to
cook.

The walls of all such appliances must be air-tight
for they will be valueless if air is allowed to enter or
leave the space, since this would start convection
currents, and though air is one of the poorest heat
conductors known, it distributes heat very readily by
convection. If, however, air currents are prevented,
the temperature of the refrigerator or cooker will
change very slowly.

The thermos bottle, which consists of two bottles
blown one inside the other, is made on the same
principle as the refrigerator, but the space between the
bottles is a vacuimi, the air being pumped out before
the bottles are sealed together at the top. Naturally,
heat cannot be conducted through a vacuum and thus
it is only around the cover that heat can pass or enter
a thermos bottle and thus hot liquids put into them
will remain hot, and cold ones cold, for several hours.

Flannel and other loosely woven woolen material
owe their value for warm clothing largely to the air
which is held within the meshes of the material, this
interfering with the escape of heat from the body.

Convection

Definition. — Convection has been defined as the
transmission of heal by the transfer of the heated body
itself.

8o Physics and Chemistry

Nature. — In experiment lo, it was seen that if the
upper part of a test-tube filled with water was held
in the flame, the water at the bottom of the tube did
not become warm for a long time, but that if the
bottom of the tube was held in the flame, all the water
soon became heated. The reason for the first fact
was explained under conduction. The reason for the
second is that as heat expands matter and consequently
makes it lighter in proportion to its bulk than that
which is cold, the heated water in the bottom of the
tube became lighter than that at the top and, just as a
cork, being lighter than water, will, if thrust to the
bottom of a basin of water, rise and float, the lighter
water rises above that which is colder and conse-
quently denser and heavier. This results in the
pressing down of some of the colder water toward the
source of heat. Some of that pressed down at once
becomes warmer than that directly above it and rises
with the same results as before. Thus, there is a
constant movement in the water and in time it all
becomes heated by, as stated in the definition, the
transfer of the heated matter itself, or, in other words,
by convection. This transmission of heated matter
occurs not only in water, but in all fluids, both liquids
and gases.

Convection currents in nature. — ^Winds are con-
vection currents produced by differences in the density
and pressure of the air. Such differences are usually
the result of differences in temperature due to unequal
heating of the earth and air by the sun. When air in
any locality is heated it rises and, the atmospheric
pressure near the earth being reduced, air from colder
regions passes in. This movement of the air con-
stitutes a breeze or, if there is enough difference in the

Physical Processes and their Results 8i

temperature to promote rapid motion, a wind. The
land bordering on large bodies of water will, usually,
during the day become hotter than the water, conse-
quently the air over the land becomes warmer than
that over the water and rises and the colder, denser
air from the water moves forward over the land.
This constitutes what is known as sl sea breeze. If,
as usually occurs at night, the air over the land cools
before that over the water, the air passes from the
land toward the water thus giving rise to the so-called
laTtd breeze. The trade winds, that make life in the
tropics endurable during the hot seasons, are the
result of the movements of the hot air, which, rising,
passes to the north and south leaving space for the
entrance of cooler air from the latter places.

The various ocean currents that are of such impor-
tance to the climate of many regions of the globe are
convection currents due largely to different densities
of the water, resulting from its unequal cooling and
heating in different parts, and to the rotation of the
earth.

Ventilation. — ^The two chief forces depended upon
in the ventilation of buildings are convection and
the creation of a partial vacuum.

A good illustration of a combination of these two
processes is seen in the open fireplace. The fire heats
the air in and around the fireplace thereby making it
h'ghter and causing it to rise through and from the
chimney. This creates a partial vacuum in the
chinmey and fireplace which the colder and, conse-
quently heavier air from outside and from the room
is forced in to fill. The same forces are at work also
when radiator pipes are the source of heat and open
windows the means of ventilation. The heat radiated

82 Physics and Chemistry

from the pipes causes convection currents in which the
heated air rises and is forced, so great is the pressure
of heated gases, even through cracks around windows
and doors, thus the air pressure in the room is reduced
and the colder air is pressed in.

The locations where the greater amount of hot air
will naturally escape and cold air enter can be seen
by, on a cold day, opening a window at the top and
at the bottom and holding a candle in front of first one
and then the other opening. It will be seen that, at
the lower opening, the flame is forced inward by the
incoming air and, at the upper opening, it is forced
outward by the outgoing air.

Knowing these facts, it will be easily appreciated,
that, if it is too cold outside to open a window wide,
it is better to open it slightly at both top and bottom.
A very important reason for an opening at the top of
the window is that the air exhaled in respiration,
being warmer than the air in the room, and gases that
may escape combustion when gas is burned tend to
rise.

The openings for the entrance and exit of air should
never be placed directly opposite each other, for then
two things will occur, (i) a wind or draught may be
created and (2) the air passes directly from one open-
ing to the other and thus that in parts of the room not
in the direct current is little affected.

Artificial ventilation. — In cold climates, in order
to sectire good ventilation in large buildings without
risk of draughts from ox>en windows, different forms
of artificial ventilation are now in common use. The
various methods by which ventilation is thus affected
are classed under three headings, (i) extraction or
vacuum system, (2) propulsion or plenum system*

Physical Processes and their Results 83

(3) vacuum-plenum system. Ventilation by any of
these methods is usually effected with the aid of fans
or pumps placed in chimneys or ventilating shafts.
In the vacuum system, air is withdrawn from the
building as the result of the vacuum created in the
shafts and the pipes leading to the rooms, by means of
the pumps, etc., and air from outside is, consequently,
forced, by atmospheric pressure, into the pipes and
ventilators provided for the purpose and from thence
into the rooms. In the plenum system it is in the
shafts in communication with the outer air that a
vacuum is created and the air, which is forced into
these by the weight of the atmosphere, is propelled,
by fans or other apparatus, into the rooms. The
entrance of this additional air forces some of that
already in the rooms to leave through the apertures
provided for the purpose. The vacuum-plenum
system, as the name implies, is a combination of the
other two methods.

One means of discovering if artificial ventilation is
proceeding as it should is to hold a handkerchief
in front of the ventilators; if everything is in order,
the handkerchief will be sucked toward a ventilator
through which air should leave the room and it will
be blown into the room by the incoming air at a
ventilator intended for such purpose.

CHAPTER VI

THE ETHER, HEAT, AND LIGHT

The Ether — ^Absorption, Radiation, Reflection, Refraction, and
Polarization of Heat and Light — Color of Light and of
Objects — Finsen Light — Phosphorescence and Fluorescence.

Radiation

Nature of radiation. — The process of radiation
was so named because heat and light transmitted in
this way pass from their source in straight lines or
radii. One proof that this is true of heat is demon-
strated by holding a screen between the individual
and the source of heat, since the direct heat then
ceases to be felt. That any heat is then perceived
is due to convection currents in the air. Likewise,
if an object through which light rays cannot pass is
held between the eyes and the light, the latter can
no longer be seen and that there is any lighting of a
locality screened from the direct rays of a light, is due,
as will be seen later, to reflection.

The Ether

In order to understand radiation it is necessary to
know of the existence of the ether. For various
reasons, among others, the transmission of heat and

The Ether, Heat, and Light 85

light through the millions of miles between the sun
and the upper strata of air and the nature of radiation,
scientists concluded that there must be something
besides air permeating all space, not only that above
the air but also that existing in all matter, and to this
invisible, intangible something they gave the name of
ether.

Nature of ether waves. — ^All matter, but more
especially that in which molecular motion is pro-
nounced enough to cause sensible heat, will, by means
of its molecular motion, start waves in the ether that,
though not precisely similar, are likened to the
series of circular waves that arise when a stone is cast
upon the quiet surface of a pond. These waves
spread out in all directions and, the hotter the body
starting the vibrations, the more rapidly will the
waves be formed and the greater will be the number of
short waves (t. e., those in which there is only a short
distance between successive waves).

Length of ether waves. — Ether waves started by
very hot bodies, such as the sun, vary greatly in length.
Some, for example those made use of in wireless tele-
graphy, are miles long and others are only about
asolouo part of an inch. As the longer waves
produce electric effects, they are termed electric
waves. Waves which measure only a few thousandth
part of an inch are capable of increasing molecular
motion in matter and consequently of raising their
temperature; they, therefore, are called heat waves.
Waves that are as short as js^ part of an inch
aflEect the endings of the optic nerve in the eye and
are therefore called light waves. Waves that are less
than ^5^ part of an inch do not affect the sight,
but they do affect the chemicals upon a photographic

86 Physics and Chemistry

plate and they cause many chemical changes in nature,
therefore, they are called chemical or actinic waves or
rays.

Origin of color. — Light waves have different lengths
and difference in length results in different colors.

TABLE SHOWING THE WAVE LENGTH OF DIFFESENT COLORS OF

LIGHT:

Color Wavelength* Color Wavelength

Red .0007 mm. Green .00053 mm.

Orange .0006 mm. Blue .00047 mm.

Yellow .00058 mm. Violet .0004 mm.

Only the molecules of very hot bodies vibrate
with sufficient rapidity to produce waves of a length to
affect the optic nerve, i.«., light rays. The tempera-
ture of a body must be raised to 525** C. before waves
short enough to be visible as light appear. When this
temperature is reached, a red glow is seen and as the
temperature is increased, though long waves are
being generated, shorter and shorter ones (those
that give rise to the different colors) are produced
until, between a temperature of 860^ C. and 1200^ C,
waves of all colors are being generated and con-
sequently a so-called white heat or light is reached for,
when all colors of the spectrum' are present in a com-
bined state, a white light is produced. This is the
case with sunlight. The sun, being t he hottest of all
bodies, produces waves in the ether of aU^possible
lengths ; thus, in the sunlight, as already stated, there
are waves that will give rise to electric effects, heat,

* A millimeter (mm.) equals 0.3937 of an inch.
' The colors seen when light waves are refracted by passing
through a prism, etc.

The Ether, Heat, and Light 87

light of all colors, and chemical reactions. That
the sunlight contains all the colors of the spectrum is
seen when it undergoes refraction, as in the rainbow
and in passing through prisms, see page 100.

In one sense, aU ether waves are heat waves, since
waves of all lengths will increase molecular motion in
bodies and thus raise their temperature.

Retention of heat. — ^Light waves can penetrate
many substances easily that the longer heat waves
pass through only with difficulty and this is of great
value to man. For instance, light waves pass
through the glass of hot-beds and conservatories
and through snow, paper, etc., covering plants, they
are partly absorbed by the earth and plants the
molecular motion of which is thereby increased and
heat produced which, as it does not readily pass
through the plant covers, remains and furthers the
growth of the plants. Also, the light waves pass
readily through damp air, smoke, and the like, but the
heat waves only do so slowly and with difficulty; for
this reason, clouds and smoke at night serve to
maintain the warmth that the earth acquired during
the daytime. Thus a clear night is likely to be cooler
than a cloudy one. The fruit growers of California
bum smudge fires in their orchards when there is
danger of a frost, because heat and also a heavy low-
lying smoke that prevents the escape of heat from the
ground results from these fires.

How the air is heated. — Heat being the result of
molecular motion, it cannot, it is believed, exist apart
from matter and consequently ether waves are not
themselves hot, though, by increasing molecular
motion in all matter which they strike, they are the
cause of heat.

88 Physics and Chemistry

Ether waves would pass through absolutely dry
air without producing any decided heating effect,
but moisture and solid matter, as dust, in the air will
give rise to heat. Moistiire also serves to hold the
heat and to transmit it in all directions. Also, as
stated in the preceding paragraph, it helps the earth
to retain the heat it acquires during the da3rtime and
yet, it acts as a screen between the earth and the
sun's rays. On high mountains, above the clouds,
where there is little moisture, people will suffer in-
tensely from the heat formed in their own bodies by
the impinging upon them of the ether waves, while
the air surrotmding them is cold. These effects of
moisture are among the several reasons why the tem-
perature of places near large bodies of water are more
tmiform the year round than those not so situated.

Effect of different kinds of matter upon ether waves.
— ^When ether waves strike any medium other than
ether, any one of three things may happen ; they may be
wholly or in part (i) reflected; (2) transmitted {i.e,,
allowed to pass through the substance) ; (3) absorbed.

Opaque, translucenti and transparent objects. —
Such substances as metals, wood, etc., which do not
permit the passage of light rays are said to be opaque.
Those which allow some light to pass through their
substance, e.g., ground glass and paper, but do not
permit objects on their farther side to be seen, are said
to be translucent. Objects, such as dear glass, through
which light ray^ pass freely and allow objects on their
farther side to be seen are said to be transparent.

Reflection

Nature of reflection. — ^Ether waves may be reflected
or thrown back from matter which they strike in

The Ether, Heat, and Light 89

two ways; one of these is termed regular reflection
and the other diffuse reflection. The straight
beam of light that is seen striking back from a mirror
upon which a ray of light falls on entering through a
small aperture into a darkened room is an example of
regular reflection. Diffuse reflection is the scattered,
diffuse or irregular throwing back of light that occurs
when light waves fall upon a rough or unpolished
surface.. It is due to the diffuse reflection of light
waves from dust and moisture in the air and from
objects upon the earth that there can be light all
about us and not only in the direct path of the light
rays. The phenomenon, popularly known as "the
sun drawing water" is produced by the reflection of
light, from sunbeams coming from behind a cloud,
by dust and moisture in the air. The light of dawn
and twilight are due to reflection of the sunlight by
moisture and dust in the air which catch the light even
before the sun appears or after it disappears below the
horizon. The colors of sunset also are due to the
reflection of light waves by the clouds and particles
in the air. The colors are seen in the evening because
the atmosphere is then denser than earlier in the day
and thus more light waves are absorbed and, as the
light waves then strike the clouds from below, their
reflection is facilitated.

Why we see objects. — ^We see objects because they
reflect light waves which fall upon them back into our
eyes so that they strike upon the retina and form a
picture there, as upon the sensitive plate of a camera,
and thus stimulate the optic nerves which then
transmit their impressions to the center of sight in
the brain.

Differences in the power of absorptioni reflection,

90 Physics and Chemistry

etc. — Matter varies greatly in the degree of absorp-
tion, radiation, and reflection of which it is capable
and it is useful to have some knowledge of these
differences. For instance, one without such knowl-
edge might think that asbestos would be a good
protector to put behind a stove, but asbestos, though
itself non-combustible, absorbs and thus has its
molecular motion increased and is thereby heated by
ether waves and therefore it would be likely to
scorch paper or wood behind it. A highly polished
tin or zinc mat, on the other hand, reflects so many
ether waves, instead of absorbing and being heated
through by their action, that it will protect a wall
behind it. White paint reflects more heat and light
waves than dark paints, which is one reason why white
or light colored paints, papers, etc., make a room
lighter than dark colors and why black and dark
colored clothing is warmer than white and light colors.
Rough, dull surfaces absorb and radiate heat better
than smooth polished surfaces and thus radiator
pipes are alwajrs rough, to have smooth ones would
entail a great loss of heat. Bright smooth surfaces,
as mirrors and polished metal, are the best reflectors,
but practically all bodies reflect some light waves,
were this not the case, we would not see them, for, as
stated in a previous paragraph, we see objects because
of the light which they reflect into our eyes.

It is trying to the eyes to read what is printed or
written on glazed paper and highly polished black-
boards, because so much light is reflected from the
shining surface that the words are obscured. An
intense reflection or glaring light from any source is
harmful to the eyes and the new method of artificial
lighting, in which the light is thrown upon the ceiling.

The Ether, Heat, and Light 91

in order that it may be diffused and a more even, less
concentrated, lighting be accomplished, is an attempt
to obviate such defects.

The differences in the power of absorption, reflec-
tion, etc., are thought to be due, at least in part» to
differences in the molecular motion of matter.

Origin of the color of bodies. — ^The color of objects
depends upon the ether waves which they absorb
and reflect; e.g., grass is not green, but it appears to
be green because it reflects green waves and absorbs
those of other colors; a paint or dye appears to be a
certain color because it reflects the wave of the
particular color it appears to be and absorbs all other
waves. Matter that does not absorb one set of
wave lengths more than another, but reflects them all
equally, appears white, and matter that absorbs
practically all the ether waves incident upon it appears
black.

Number of colors. — ^Though sunlight, when re-
fracted by passage through a prism, appears to be
separated into but seven distinct colors, many hun-
dreds of colors are possible. One reason for this
is that waves of more than one length are reflected
by the majority of the chemicals used for dyes and
paints and other objects and if w£^vcs of different
lengths are reflected, but not in suflSdent number or
quantity to cause white light, a different shade or hue
of the predominating color — i.e., the wave length
reflected to the greatest extent — can be obtained.
As will be seen later, mixing paints alters the degree
of absorption and reflection of waves and thus gives
rise to different colors and shades.

Reason for changes of color under artificial lights. —
Artificial lights, not being as hot as sunlight, do not

92 Physics and Chemistry

produce all the wave lengths that the latter does and
different kinds of artificial lights vary in the lengths
of waves that they produce. Consequently, as
objects have not the color, but essentials for color,
they may not be the same color by artificial light as
they are by sunlight, or by electric light as by gas
light, for the particular wave or waves may not be
present to be reflected.

Reason for the fading of colors. — The chemical
rays of the sun and certain chemicals used for bleach-
ing cause changes in the nature of the pigments used
for dyes and paints which lessen their power of
absorption of light waves, and thus more waves are
reflected and this gives rise to the presence of a
greater amount of white light, in consequence of which
the color is lighter. The object is then said to be
faded or bleached.

Why color is perceived. — In order that color be
perceived by the brain it is necessary for the retina
to be stimulated in some way by the color rays enter-
ing the eye. How it is stimulated is not known,
but one theory advanced is that the retina contains
a compound chemical substance which is acted upon
by the incoming color waves in some way, as yet
unknown, so that chemical changes are brought about
which produce the sensations that give rise to the
color sensations which we perceive.

Color blindness. — ^About 4 to 5 per cent, of men
and I per cent, of women have defective color vision.
As a rule, this defect consists in not being able to
distinguish some one or, more frequently, two colors,
but occasionally there is an inability to distinguish
any color and individuals with this disability can
distinguish form, light, and shadows, only. Any

The Ether, Heat, and Light 93

defect of color vision is spoken of as color blindness.
The cause of the condition is unknown. Some
authorities consider it due to a lack of some chemical
substance in the retina and others to defective forma-
tion of the nerve-endings that should be affected by-
color.

Complementaxy colors. — ^When certain color waves,
as red and green, yellow and blue, green and violet
stimulate the retina at the same time, they produce a
sensation of white. The pairs of colors which do
this are called complementary colors. It is because
yellow and blue waves produce a sensation of white
that we use bluing to improve the color of white
clothing that has become yellowed.

Reason for colors produced by mixing different
colored pigments. — The results obtained when colored
lights fall upon the retina are not the s&me, it will be
observed, as when paints are mixed; for instance,
when yellow and blue paint are combined we get a
green color, because yellow pigment absorbs all
colors except yellow and some green while blue absorbs
all colors except blue and some green, and mixing
the two pigments causes the absorption of all color
waves except green. A white paint added to another
lessens its power of absorption, hence more waves
are reflected and a lighter color results. On the other
hand, the addition of a so-called black pigment to a
colored paint increases its power of absorption and the
color appears darker.

Color of transparent objects. — The color of trans-
parent objects depends upon the light waves they
transmit — L e., allow to pass through them. All
light waves pass through white glass, but if a color-
ing matter that will allow the passage of red waves

94 Physics and Chemistry

only is added to glass in the process of its manu-
facture, then onlj' red waves will pass through.
Blue glass absorbs all color but blue waves and a
little green and it transmits the blue and green.
Yellow glass transmits yellow waves freely, green
and red to a slight extent, but blue and violet not
at all.

The power of colored glass to absorb some waves
and transmit others is made use of in heliotherapy.
By looking at the table on page 86, it will be seen that
the waves which give rise to a red color are nearest
in length to those that have the greatest power to
produce heat in matter and, therefore, if red glass is
placed between a patient and the sun's rays the
waves passing through will have a heating effect,
but those which produce chemical reactions and,
consequently, so-called sunburn are shut out. Violet
rays, being nearest chemical waves in length, the
waves that pass through violet glass produce chemical
reactions but have not such a heating effect as those
which pass through red glass. The waves that pass
through yellow and green glass give rise to slight
heating and slight chemical effects. Thus yellow
or green glass placed between a patient and the sun's
rays will prevent sunburn and intense heating.

Ultra-VioIet Rays. Finsen Light

When light is passed through a lens made of quartz

r or certain other substances, all ether waves are ab-

) sorbed except those which give rise to violet and ultra-

l violet rays. The latter, partly, it is thought, by the

chemical reactions that they promote in the tissues,

are often very effectual in the treatment of such

The Ether, Heat, and Light 95

diseases as lupus. Ultra-violet light is obtained also
by electrical means in somewhat the same manner as
the X-rays, which will be discussed later.

The ultra-violet light was named Finsen light in
honor of Niels Ryberg Finsen, the Danish physician,
who first advocated its use in the treatment of
disease.

Refraction

Nature of Refraction. — Ether waves of all lengths
can be refracted, that is, bent from their course, in
thesameman-
ner, but as it
is the light
waves that
give the most
obvious re-
sults of their
refraction
they are the
ones that we
will consider.
The ref rac- Fig- 44- Linb Bent toward and away
tion of lieht from the Perpendicular.

waves occurs ^**^ Perpendicular line, (b) Line bending

toward the perpendicular, (c) Line bending
when they away from the perpendicular,
pass oblique-
ly from a medium of one density into that of another
density. If the medium into which the waves pass is
of greater density than that in which they are — tf.g.,
when they pass from air into glass or water — they are
bent toward the perpendicular, but when the meditun
into which they pass is of lesser density than that which

Physics and Chemistry

they leave — e.g., when they pass from glass or water
into air — they are bent from the perpendicular. It
is because the light rays coming from an object placed
under the lens of the objective of a microscope are
diverged, as in (b) Pig. 46,
and thus enter the eye at a
wider angle than the direct
rays would, that the image
of the object is magnified.
CauM ai refraction. —
The cause of refraction is
that ether waves travel at
different rates in media of
different densities: for in-
stance, light waves pass
through water atonlythree-
fourths the speed with
which they travel through
air, and when a ray of light
strikes a body of water ob-
liquely all portions of its
front will not enter the
water at the same time
and the part which enters first becomes retarded before
that entering later. In Fig. 45 the short parallel
lines represent the wave front of a beam of light enter-
ing obliquely from air into water; one part (a) reaches
the water before (b) and, as it then travels more
slowly than that part of the wave which is still in the
air, it only reaches (c) while (b) is going to (d) ; thus
the beam is bent. It is because of refraction that a
stick held partly in the air and partly in water looks
as though it were bent. Rays of light entering from
one medium into another perpendicularly are not

Pig. 45. The Bending of a
Beau of Light Entbrino

FBOIl THE AlH INTO WaTBR. ,

The Ether, Heat, and Light 97

bent. It is due to refraction that the rays o£ light
which are reflected by objects into our eyes both
perpendicularly and obliquely come to a focus on
the retina. The cornea, lens, and humors of the
eye serving to cause refraction.

When the suxface of a refracting medium is convex
— >.«., thicker in the center than at the edges — light

Pio. 46. (a) Showing how refraction by a convex auifaco
will bring light rays to a focus, (b) Showing how light rays
will be diverged on pngeing from a medium of greater into
one of lesser densi^.

rays come to a focus quicker than when it is flat,
and the normal eye is provided with a means of
becoming more convex when looking at objects near
at hand.' When, for any reason, the eyes lose their

* It is thought, that when the eye is at rest or fixed upon distant
objects thesuspensoiy ligament (i.e., theligament that is fused to
the anterior surface of the capsule inclosing the crystalline lens of
the eye and attached at either end ta the ciliary processes be-
tween the choroid and the iris) eierts a tension upon the leng
which keeps it flattened, particularly along the anterior auiface,
but when the eye becomes fixed on near objects the dliary musde
contracts and in doing so draws forward the choroid coat and
thus relaxes the tension of the ligament, in consequence of whiiA
the anterior surface of the lens becomes more convex.

Physics and Chemistry

power of adapting themselves in this way to view
near objects or when the
eyeball is naturally shal-
low, light rays would
have to extend behind
the retina to come to a
focus and the vision of
objects near at hand, es-
pecially fine ones as the
letters of printed matter,
is blurred and indistinct.
This condition is known
as hypermetropia oi far-
sightedness. The term
far-sighted is applied to
eyes with this defect
because when it is not
very great the individual
can often see things at
a distance better than
people whose eyes are
normal. Defective vis-
ion due to this con-
dition is corrected by
wearing glasses, by
means of which the rays
are sufficiently refracted
to make up for the de-
fective structure of the eyeball or action of its refrac-
tory apparatus, as the case may be. Failure of
accommodation, due to old age, is known as presbyopia
or old-age sight.

Another defect of the eyes that interferes with
proper refraction is that known as myopia or near-

FlG. 47. MlCBOSCOPB,
e, Eyepiece, d, Draw tube.
Body tube, m, Revolving noae-
piece. o. Objective, ph, Pin-
ionhead. mh, Micrometer head,
ha. Handle arm. s. Stage.
Substage. m. Mirror, b, Base,
r, Rack, p, Pillar, i, Inclina-
tion elevation of handle ai

The Ether, Heat, and Light 99

sigkudness. This is usually due to a too great curva-
ture or too great depth of the eyeball, in consequence
of which light rays come to a focus before they reach
the retina. To obviate the blurring of vision due to
this condition concave lenses — i. e., those thinner in the
center than at the edges — are worn, because they cause
rays of light to diverge before entering the eye and
thus it takes them longer to come to a focus afterward.

,-l

8 C

Fig. 48. DiFTBBENT TvFEs OF Lenses.
A, Double convex, b. Plane convex, c. Concave
convex, d, Double concave, e, Convex concave.
P, Plane concave, c, Prism convex. B, Cylin-
drical convex, t. Cylindrical ct

Light is divei^ed by a concave lens because the mid-
die of the wave is retarded less than the edges, as the
lens is thinner in the center than at the edses.

Astigmatism. — Still another cause for defective
refraction in the eyes is the condition known as
astizTnatism m which the curvature of the refractory
apparatus is not equal in all parts. This makes it
necessary for the ciliary muscles to be constantly in
action while the individiial is reading, focusing for
the lines of letters that run in different directions.
This soon results in eyestrain. Cylindrical lenses,
which have a plane surface in one axis and a curved :

100 Physics and Chemistry

surface in the axis at right angles to it, are worn to
correct the condition.

Prism glass. — Glass with a rough surface will be
often seen in windows that open on to a court or
narrow street or passage. This is called prism glass.
It improves the light in a room because the prism-
like projections on its surface refract the light waves
passing through it, causing them to penetrate farther
into the room than they naturally would.

The rainbow* — ^When light waves enter drops of
water or glass that is cut in the manner of the beveled
edge of a mirror or of a prism, these of di£Eerent lengths
suffer unequal refraction and thus they become
separated and the di£Eerent colors are discernible.
The rainbow, which is due to the refraction and re-
flection of light in drops of water in the a:r, is an
example of this kind of refraction of light waves.

Nature of polarization. — By polarization is meant
making light vibrations take place in one direction.
The streak of regularly reflected light striking back
from a mirror is an example.

How light can be polarized. — Light is polarized
by reflection from a flat, highly polished surface, as a
mirror, by refraction and by passage through such
substances as the mineral tourmaline and iceland
spar. As these substances cause polarization, it is
thought that their electrons must vibrate in one
particular direction and that only waves that will
vibrate in the same way can pass through them.

Light is often polarized from a mirror in order to
thoroughly illuminate body cavities. It is polarized
by a special apparatus known as a polariscope^ in

The Ether, Heat, and Light loi

pathological work, for the detection of glucose in
fluids, such as the tuine, for when polarized light
falls upon glucose it is rotated to the right and the
degree of rotation will depend upon the amount of
glucose present and thus it is an easy and accurate
way of determining the quantity of glucose in a
solution. Levulose, on the contrary, turns polarized
light to the left. Also, there are a number of other
substances that turn it to either the right or left in
varying degrees and thus it is used in many varieties
of scientific work, especially as a means of identifying
substances which rotate it.

Phosphorescence and Fluorescence

Phosphorescence. — Certain substances, after being
exposed to a strong light, will emit light in the dark.
This property is termed phosphorescence and matter
which possesses this power is said to be phosphorescent.
Paints which are luminous in the dark contain some
phosphorescent material, usually baritun chlorid.
A certain class of bacteria, called photogenic^ produce
this quality in matter, especially fish, in which they
produce decay.

Fluorescence. — Certain substances, such as the
mineral fluorite, fluoresdn, platino-cyanid of barium,
uranium glass, and solutions of quinin sulphate,
have the power to change the length of ether waves,
and thus of changing heat waves to light waves and
vice versa to a marked degree, and of reflecting color
waves different from those thrown upon them. Sub-
stances which do this are said to he fluorescent. This
name was given, because the mineral fluorite was the
first substance in which the property of fluorescence
was noted.

CHAPTER VII

ELECTRICITY

Theories Regarding the Nature of Electricity and Electrification
— Conductors and Non-Conductors — Different Methods of
Generating Electric Currents — Nature and Action of
Chemical Cells and Batteries for Generating Currents —
Electrolysis — Electroplating.

Derivation of name. — The term electricity was
derived from the Greek work electron ^axnher,
because the first record of electrization was in connec-
tion with this substance. This record, which was
made by the Greeks, some 500 years before
Christ, was to the effect that if amber was rubbed
with a dry doth it would attract light objects to
itself.

Experiment 11. Object: To study electrification.

Procedure: (a) Rub a glass rod for a few minutes
with a dry woolen doth or a piece of silk and then
drag it through some small pieces of paper scattered 00
the table.

If the rod is rubbed long enough, under statable
conditions, see page 107, it will attract the pieces
of paper towards itself.

(b) Hang this rod by a piece of silk thread to a
wire bar or stirrup, dectrify another glass rod in thf
same manner as the first rod and hold it against the

Electricity 103

free end of the suspended rod, the latter will swing
away from it; i.e., it will be repelled.

(c) Rub a piece of sealing wax with silk and hold it
near the suspended glass rod, the latter will swing
toward it; i. e., it will be attracted.

(N. B. Be careful while doing this experiment
not to let the part of the rod that is to be used come
in contact with the hand or other object. The reason
for this will be seen later in the section on conductors.)
In the same section it will be also explained why this
experiment is seldom successful in wet weather.

There are two things to be learned from this ex-
periment: (i) Friction will produce electrification.
(2) Substances of similar material electrified in the
same way repel each other, but electrified objects of
different material or of the same material differently
electrified may attract each other. This is because
there arc two kinds of electrification — *. e., of electric
charges — and one of the laws of electrical action is:
Like charges repel each other and unlike charges
attract. The two kinds of charges have been arbi-
trarily named positive and negatioe, and a positively
electrified body is often defined as: An electrified
body which acts toward other dectrifi^ bodies cls
does a glass rod that has been rubbed with silk.
Likewise a negatively electrified body is said to be:
One which acts toward other electrifi^ed bodies as does a
stick of sealing wax which has been rubbed with flannel.

But one kind of electricity. — ^Though the expres-
sions negative deUricity, positive electricity, static
electricity, current electricity, etc., are constantly
used, there is but one kind of electricity. For this
reason, it has been suggested that the terms negative
Md positive electrification or negative and positive

104 Ph3rsics and Chemistry

electric charges be used instead of negative and
positive electridty. By static electricity is meant,
that which is not flowing, as, for example, when it is
passing over a wire. In the latter case it is known as
current electricity, or, more correctly, an electric current.
The difference, however, lies, not in the electricity, but
in the manner by which it is made manifest.

Some theories regarding the nature of electricity. —
Though a sufficient degree of knowledge, of the ways
in which electric charges and currents can be produced
and of the results of their action, has been obtained to
allow of electridty being applied in a great many
ways to the service of man, its nature is still a matter
of conjecture. Some theories that have been ad-
vanced are as follows :

The two-fluid theory. — ^When the ease with which
electridty moved over certain substances was first
realized, the idea was conceived that it was a fluid.
Or, rather, it was thought at first that there were two
fluids, one giving rise to positive and the other to
negative charges.

The one-fluid theory. — About the year 1750,
Benjamin Franklin advanced what is called the one*
fluid theory, which holds that there is but one kind of
fluid and that positive charges are the result of an
excess of electridty and negative charges of a lesser
amount. Because of this supposition, Franklin used
the plus sign (+) as a s3rmbol for positive charges, and
the minus sign (— ) as a s3rmbol for negative charges.
These signs are still used, though, according to the
electron theory, which many sdentists think is
probably nearer the truth, a positively charged body
has lost, instead of gained, electrons.

The electron theory. — ^The electron theory is based

Electricity 105

on the assumption that the atoms of all elements are
composed of electrons. It holds that each atom of an
element consists of inconceivably small positive cor^
puscles that are surrounded by thousands of still
smaller bodies called negative eUctrans. These nega^
tive electrons are, it is thought, constantly revolving
with exceedingly great rapidity around the positive
corpuscles and were it not for the attraction of the posi-
tive corpuscles, they would, it is thought, fall away.

Ordinarily, the majority of substances are in a
state of electrical equilibritun — i.e., neither positive
nor negative — ^but, it is assumed, some of the more
easily detached revolving electrons may be transferred
from one atom to another without dissociating the
atom; the only change being that the atoms of the
substance by losing some of their negative electrons
have their positive charge strengthened and the sub-
stance is then said to have an electro-positive charge.
On the other hand, the substance that gained the neg-
ative electrons has its negative charge strengthened
and is said to be electro-negative. This is what it is
thought happens in Experiment 1 1 . The friction of the
silk on the glass caused the atoms of the latter to part
with some of their negative electrons to the silk and
thus the glass became positively and the silk nega-
tively charged. On the contrary, the silk gave some
of its electrons to the sealing wax and thus it became
positively and the wax negatively charged.

The reason why the silk and other material gain
electrons in one case and lose them in another is
thought to be due to some difference in the number
and arrangement of the electrons by which certain
substances are able to take electrons more readily
from some materials than from others.

io6 Physics and Chemistry

It is believed that positive corpuscles are never
dissociated from the atoms.

Nature of an electric current. — ^As stated on page
104; an electric current is simply a flow of electricity
through some object and this flow, it is now believed
by many scientists, consists simply of a passing of
negative electrons from atom to atom, usually in one
direction, along the object.

Conductors. — ^There is a great difference in the
ease and rapidity with which an electric current pas-
ses through different kinds of matter. For example,
copper wire will conduct electricity a million times
better than water. Substances through which a
current passes readily are said to be good conductors.
Those through which it does not pass readilyare called
poor conductors, and very poor conductors are termed
nonconductors or insulators. No substance however
is a perfect conductor nor a perfect insulator.

ThefoUowing list shows the relative conducting value
of some common substances. They are mentioned in
the order of their conducting value beginning with the
most efficient. The last nine are considered insulators.

Silver

Dry air

Copper

Silk

Altuninitun

Sealing wax

Zinc

Glass

Iron

Hard rubber

Carbon" .

Porcelain

Dilute sulphuric add

Shellac

Water

Paraffin

Human body

Oils

Linen

Cotton

Wood

Electricity 107

Moist air is a much better conductor of electricity
than dry air, which is why Experiment ii is not
likely to be jmccessful when the humidity is very
high. Dry air, being more rarefied than moist air, is
a very poor conductor, thus in dry air a substance
retains its charge for some time. A common example
of the favorable influence of dry air on electrification
is seen also when brushing the hair in cold, dry
weather. For the crackling sound that occurs and
the flying of the hairs apart are due to electrification ;
and that the hairs fly apart, but cling to the brush,
shows that like charges repel each other and unlike
charges attract each other. Glass, sealing wax,
silk, etc., were used for the experiments because,
being poor conductors, they retain their charge for
some time. Metals wotdd not serve such a purpose,
since, being good conductors, they lose their electrifica-
tion unless it is being continuously produced as for an
electric current. If the hand is rubbed over the
electrified rod, the latter will lose its charge, which
will be imparted to the hand, and the same thing will
happen if the rod comes in contact with metal or any
substance that will act as conductor.

How an electric current is produced. — ^In order to
start and maintain an electric current along a conduc-
tor some external force is necessary. This is generally
obtained by the use of an electric cell or battery or of a
dynamo. The force obtained by use of a cell or battery
is the result of chemical action, and that obtained with
a dynamo is, as will be seen later, due to some form
of mechanical action or of heat.

Chemical batteries. — Chemical electric batteries
consist of two or more cells and the essential parts
of a cell are:

io8 Physics and Chemistry

A jar An electrolyte

Two electrodes A conductor

The electrodes. — ^These are two flat plates or bars
of metals or other substance by which the current
enters and leaves the electrolyte. The electrode at
which the current is started is known as the anode
(from the Greek an » in and hodos^SL road) and the
electrode by which the current has been supposed to
leave the cell is known as the cathode (from the Greek
cath^ away and hodos^a, road).

Zinc is very generally used for the anode of battery
cells for two reasons: (i) It is easily acted upon by
liquids that are convenient to use for electrol3rtes»
and this chemical action provides the energy necessary
to procure the electric current; (2) As zinc is dissolved
by the acid its atoms part with their negative electrons,
leaving them with the undissolved metal. The neces-
sity for this will be seen later. Since the anode
thus becomes negatively charged, it is spoken of as
the negative electrode and is represented by the
minus sign (—) .

A cathode for a chemical cell is generally made of
either copper or carbon; these substances not being
acted upon by electrolytes that dissolve zinc. As will
be seen later, when a cell is in action, the cathode
acquires a positive charge and it is therefore often
referred to as the positive electrode and it is repre-
sented by the plus sign {+).

Electrolytes and electrolysis. — ^An electrolyte is a
solution that conducts and is decomposed by elec-
tricity. The process that occurs in an electrolyte
is spoken of as electrolysis.

The electrolytes generally used for chemical batteries

Electricity 109

are sal ammoniac and sulphuric add, but solutions
of any inorganic adds, bases, and salts will undergo
electrolysis.

Nature of electrolysis. — It is thought that when
inorganic adds, bases, and salts are dissolved in water
a portion of their molecules become separated into
two or more parts, called ions, which move about
in the solution independently of each other and of
other atoms and molecules (hence their name, which
is derived from a Greek word meaning wanderer).
Ions, are tmlike other atoms and molecules in that
they have an electrical charge; in fact, a common
definition for an ion is an atom or radical having an
electric charge.

When a substance undergoes electrolysis, one of
the ions resulting from the dissodation will have a
positive and one a negative charge. According to the
electron theory, this is because the atoms of the ele-
ment or elements forming one ion gave up some of
their negative electrons to the other ion in the process
of decomposition. The ion losing the electrons is, of
course, the positive ion and the one gaining electrons,
the negative ion. When sulphuric add (HaS04) is
thus decomposed, the hydrogen ions are the positive
ions and are said to have or carry a positive charge
and the sulphate ion (SO 4) has a negative charge.
When soditun chlorid(NaCl) is dissodated, the sodium
(Na) has a positive charge and the chlorin (CI) a
negative charge; when soditun hydroxid (NaOH) is
dissodated, the sodium (Na) has a positive and the
hydroxyl ion (OH) a negative charge, and so on.

Positive ions are called cations, because they go to
the cathode and, like a positive charge, they are
represented by the (+) plus sign. Negative ions are

no Physics and Chemistry

called anions, because they collect at the anode and
they are represented by the (— ) minus sign.
Arrangement of a simple cell.— The simple cell,
often used in laboratories
for the purpose of observ-
ing the action that occurs
in chemical batteries, is
known as a Galvanic or
Voltaic cell; because Gal-
vani. an Italian anatomist,
in 1786, was the first to dis-
cover that a continuous
current of electricity could
be procured by chemical
means, and Volta, an Italian
physicist, in 1800 invented
an arrangement similar to
this form of cell. It is ar-
ranged as follows: A strip
of zinc and a strip of cop-
per, each having a piece of
copper wire soldered, or
otherwise attached to their
upper end, are fixed, one
on either side, in a jar con-
Pig. 49. Voli«cCbll. ^"^""^ ^'^"^^ sulphuric
(a) Anode or positive pole - . ^^ ^•"'•°''- '^'' «1«^-
(e) Cathodeor negative pole +. trode, electrolyte, and con-
ductors are known as the
electric circuit, since it is through these things that
the electric current passes. When the wires attached
to the electrodes arc joined, the circuit is said to be
made or closed and when the wires are disconnected
the circuit is said to be open or broken.

Electricity 1 1 1

Chemical action that occurs in a cell. — ^When the
zinc (Zn) and the sulphuric acid (HaS04) come in
contact, the zinc begins to dissolve gradually and
the HaS04 to split into H and SO 4 ions. The
atoms of the dissolved zinc thereupon tmite with the
sulphate ions, forming the salts known as zinc std^
phate, and the hydrogen appears in the form of
bubbles first on the zinc strip and, after the circuit
is closed by connecting the wires, on the copper plate
or cathode.

Theories of electric action. — ^The manner in which
the electric ctirrent passes through the circuit has not
been as satisfactorily ascertained as the nature of the
chemical action and, at present, there are two theories
regarding this. They are about as follows:

Theory i. As the zinc goes into solution in the
acid, the atoms separated from it leave some of their
negative electrons behind in the undissolved portion
of the metal ; thus, this soon acquires a negative charge,
and the solution surrounding it, which contains the
dissolved zinc, becomes positively charged. This
part of the solution repels the hydrogen atoms, which
are also positively charged, and, consequently, they
I fly to the copper pole. Of course, as already stated,

j the zinc unites with the SO 4 and becomes electrically

neutral — i. e., neither positive nor negative, but,
while the circuit is closed, there is always enough
imunited positive zinc in the solution to repel the
hydrogen atoms. When the hydrogen ions reach the
' copper they part with their charge and collect as bub-

bles of hydrogen gas upon it. As the copper electrode
receives the charge from the hydrogen ions it becomes
positively charged. The electric current thus started
passes up the copper plate over the wire conductors

112 Physics and Chemistry

to the zinc electrode, down this to the electrolyte, and
back to the copper electrode, and so on.

Theory 2, which has been formulated since the
electron theory of the nature of electricity was ad*
vanoed, considers that the current leaves the cell from
the zinc pole or anode and not, as has always been
supposed, from the cathode.' It holds that, due to
the force generated by the chemical action, the
negative electrons left behind on the zinc electrode
by the atoms of the metal which goes into solution
in the acid, as described in Theory i, fly up the
electrode and over the wires to the cathode, and sq on.

If the two wire conductors are disconnected, thus
breaking the circuit, chemical action in the cell soon
ceases. The reason for this, it has been assumed, is
that, when the current ceases, the zinc acquires such a
strong negative charge that it holds on to the positively
charged zinc atoms and keeps them from going into so-
lution, and, at the same time, the copper pole acquires
such a strong positive charge that it ceases to take the
positive charge from the hydrogen. As soon, however,
as the circuit is closed, the flow of the current is re^tab-
lished and the chemical action proceeds as before.

The wire conductors connecting the two electrodes
need not be short, as in the cells used for demonstra-
tions in the laboratory but for example the cells
of a battery are often put in the basement of a house
and the wires extend from this to a plate behind the
bell push button at the front door. One of the wires,
on its way to the front door, extends through the
kitchen or other room where it is connected to the
bell apparatus. The essential parts of the latter

^Scientific Ideas oj Tfhday^ Chailes R. Gibson, Seeley, Service
ft Co.. Chapter v.

Electricity 1 13

are: a bar of soft iron which is attached to the hammer
that strikes the bell, and another iron bar, called an
eUcUromagnet, that is in connection with the wire
conductor and becomes magnetized when the electric
caitTQftt passes thr ough it.

Each of the two wires at its terminal behind the
ptish button is attached to a small strip of metal.
This is where the circuit is open and closed. Ordi-
narily, the metal strips do not come in contact and
the circuit is open, but when the button is pressed
the metals come in contact and the circuit is closed
and the current at once passes through the wire. As
it passes through the electromagnet it, as previously
stated, magnetizes it, whereupon it, since magnets
attract iron, draws forward the bar to which the bell-
hammer is attached and causes it to strike the bell.
So long as the button is pressed and the circuit thus
kept closed, the cvurent passes through the circuit
and this type of a bell continues to ring. As soon,
however, as pressure on the button is released, the
circuit is opened and the bell ceases to ring.

Electric batteries. — ^The current generated in one| |
cell would not be sufficient to force its way over a | 4
long conductor, such as described in the preceding'
paragraph, and therefore, for such purposes, a battery,
consisting of two or more cells is used. The different
cells are connected by a wire extending, usually,
from the cathode of one cell to the anode of the other.

The principle of the cells of batteries in common
use is the same as the simple cell just described, but
carbon is often used for the cathode and sal ammoniac
for the electrolyte. Sal anmioniac is usually pre-
ferred to sulphuric acid because the latter, unless some
means is taken to prevent it, causes polarization; ix.^

114 Physics and Chemistry

the hydrogen gas which collects on the cathode, being
a poor conductor of electricity, prevents the passage
of the ctirrent, according to Theory i, to the cathode
and, according to Theory 2, from the cathode. If the
current is stopped in this way, the restdts will be the
same as though the circuit were broken, and the battery
is useless until the condition is rectified.

Dry cells. — The so-called dry cdls (they are moist
rather than dry) are used for so many purposes that
require only a small current of electricity that a few
words of description may not be out of place. A dry
cell consists of a zinc cylinder (this acts both as a
case for the cell and as the anode) lined with a moist
paste made of strong sal ammoniac and plaster of
Paris or other porous substance and containing in the
center a rod of carbon and manganese dioxid. The
top of the cell is sealed with wax or pitch to prevent
evaporation of the moisture from the paste. There
is a wire connected to the zinc cylinder and also one
to the carbon rod. Two great advantages of dry cells
for many purposes are that they are comparatively
small and contain no liquid to be spilled. The action
of a pocket flash lamp is obtained by means of one or
more small dry cells, which are contained in its cylinder.

Storage batteries. — Storage batteries or, as they
arc also called, secondary batteries or acctuntdators
arc much used for operating telephones, fire-alarm
circuits, furnishing power for electric automobiles
and the like. Also they are used in power houses to
store excess electricity generated by the dynamo,
thus providing a reservoir to draw upon when an extra
amount of current is required.

A common form of storage cell consists of perfo-
rated plates of lead, the perforations of whicb are

Electricity 115

filled with a paste of red lead and litharg e mixed with
sulphtiric add. These plates are kept in a suitable
receptacle, covered with sulphuric add. They are
charged with electridty by sending a current through
them from an outside generator — e. g., a dynamo.
This current dissodates the HaS04 and the hydrogen
ions move to one set of plates and change the paste in
them to a spongy metallic lead. These plates then act
as a cathode. The SO 4 ions, at the same time pass
to the opposite plates and change the paste in them
to lead peroxid. This set of plates acts as an anode.

When the circuit is closed, some of the lead peroxid
is decomposed and gives rise to an electric current,
just as occurred in the galvanic cell.

These batteries are known as secondary batteries,
because a primary current is used in their manu-
facture. This name is really more appropriate than
that of storage batteries; for these batteries do not
store electridty, but rather the electric energy has
been changed to latent energy, which, when the
circuit is closed, is, by chemical action, transformed
once more to dectrical energy. This action is analo-
gous to that which occurs in plants and coal, as
described in Chapter II. When the peroxid of lead
has been all used, the battery can be recharged by
allowing a current of electridty to pass through it
as when it was made. Thus these batteries can be
used for a long time.

Electroplating. — Some of the cheaper metals are
often coated with more expensive metals by means
of a process known as electroplating. This process,
though different in some respects, is similar to that
which occurs in a voltaic cell. The electroplating
of spoons with silver is a good illustration of the

ii6 Phjrsics and Chemistry

method. The apparatus used for this purpose con«
sists of a tank across which copper rods are placed.
These rods, which act as conductors, are connected
with wires attached to the battery. The spoons are
hung from the rod connected with the wire from the
cathode of the battery, and bars of silver are suspended
from the bar connected to the anode wire. Enough
electrolyte is used to cover the spoons and silver
bars. The electroljrte in silver plating consists of
cdlver salts, such as silver nitrate. When the electric
current is turned on, the silver salts are decomposed,
the freed silver passes to the spoons, which thus be-
come coated with the metal. At the same time, the
silver bars, which act as anodes, are being slowly
dissolved in the solution and, imiting temporarily
with the nitrate ions, they provide fresh salts.

If a gold plating is wanted, gold bars will be used
for the anode and gold salts for the electrolyte. For
a copper coating, copper bars will be used for the
anode and copper salts for the electrol3rte.

The chief difference between the action in electro-
plating and that in a galvanic battery is that, in the
former, the electric current is essential for the dissolv-
ing of the anode, since there is no chemical action
between it and the electrolyte, and in the galvanic
cell, the chemical action between the electrolyte and
the anode starts the electric current.

CHAPTER VIII

ELECTRICITY AND MAGNETISM

The Dynamo — Different IQnds of Magnets — Magnetism — In-
duction Coils — ^Transformers and Other Electrical Appli*
ances — ^Electric Currents as a Source of Heat and Lights-
Measurement of Electricity — Static Electricity — Physiologi-
cal Action of Electricity— Cathode Ra3rs — ^X-Rays — Radio
Rays

The Dynamo

The electric current produced in a chemical cell or
battery is not suitable for operating lighting and
heating appliances, motors and the like. For one
reason, the current would not be sufiSdently strong,
and, for another, the anode and electrol3rte of a
battery would have to be constantly renewed, if the
circuit were kept closed for hours at a time. It has,
therefore, been only since the invention of the dynamo
that it has been possible to use electricity to any
extent for such purposes.

The dynamo is an apparatus in which the mechani-
cal energy from a steam- or water-driven engine, or the
heat energy developed in engines fed with gas, gasoline,
or sintiilar fuel, is transformed into electrical energy.
In other words, as the result of the force of steam or
water power or of heat, the dynamo is started and kept
in action and this action gives rise to an electric ctu:«

ii8 Physics and Chemistry

rent which, according to the electron theory, is a
streaming of negative electrons along the wire con-
ductor leading from and to it.

Magnets

Magnets. — One of the essential features of djmamoSy
electrical motors, and many other electrical appliances
being an electromagnet, it seen:is well to say a word
here about magnets, magnetism, and electromagnets.

Natural magnets* — In various parts of the earth,
there is found an iron ore that will attract small par-
ticles of iron and steel.' Such ore has been named
magnetite (because it was found first near Magnesia
in Asia Minor), natural magnet, and lodestone,
meaning leading stone.

Artificial magnets. — ^When iron and steel are rubbed
on a natural magnet, or on steel that has been rubbed
by a natural magnet, they will likewise attract steel
and iron. Metals that have been thus treated are
called artificial magnets. Cobalt and nickel also
can be magnetized to a slight extent, but iron and
steel are the only substances that assume strong
magnetic properties.

Magnetic properties. — ^The chief properties or char-
acteristics of magnets are: (i) Induction, i, €., the
power to induce magnetic properties in unmagnetized
steel and iron, even at a distance. (2) Magnetic
attraction, u €., the power to attract iron and steel.
(3) Polarity.

Polarity. — If a long narrow magnet, either natural
or artificial, is suspended by a fixture at its center in a
manner that will allow it to turn freely, it will be found

> As will be seen in Chapter XVI., steel is a form of iron.

Electricity and Magnetism 119

that the magnet will always come to rest pointing
approximately north and south. Also, it will be
found that when a magnetized bar is put in the midst
of iron filings, the latter will collect around the two
ends of the bar and few if any filings will attach them-
selves to the sides. If, however, the bar is broken in
the center, the broken ends will attract the filings.
The ends of a magnet have been named its poles and
the two poles are known respectively as the norths
seeking or north pole and the south-seeking or south
pole. This property of forming poles is spoken of as
polarity.

Just as electrically charged bodies repel those with
a similar charge and attract those with an unlike
charge, so the north pole of one magnet repels the
north pole of another magnet and attracts its south
pole, and vice versa.

Why magnetite was called lodestone. — ^The earth
is a magnet and, like all magnets, it has its north and
south poles. The north-seeking pole of the magnet
was so named because it is attracted by the north
magnetic pole of the earth, and the south-seeking pole,
because it is attracted by the south magnetic pole.
Thus, the north pole of the long narrow magnet, con-
stituting the needle of a mariner's compass, points
toward the north magnetic pole, and the degree of
inclination of the needle shows the direction in which
the ship is going. It was for this reason that mag-
netite was named lodestone^ which means leading stone.

Cause of magnetism. — It is thought that each
molecule of iron and steel is a magnet at all times,
but that, ordinarily, the molecules are not lying in
any definite position and that, therefore, one molecule

OQutralia^ the effect of th^ others, When the iron

120 Ph3rsics and Chemistry

is stroked by a magnet, however, all these small
molecular magnets are foroed to turn with their north
poles all in one definite direction, and when the mole-
cules are thus placed their combined effect is strong
enough to act.

This theory accounts for at least three truths about
magnetism: (i) Only the poles of a magnet show mag-
netic attraction (naturally this would be the case
when the molecules are in position, for then the south
poles of one line of molecular magnets are in appo-
sition with the north poles of another line, and thus
they neutralize each other) ; (2) if the bar is severed,
the severed ends act as magnets; (3) if a magnet is
heated to red heat, it will lose its magnetic properties;
presumably, because the heat increases molecular
movement to such an extent that the molecules lose
the position they were made to asstime by the magnet,
and they then once more neutralize each other.

Experiment 12. Object: To study magnetic fields
and lines of force.

Procedtire: Sprinkle some iron filings upon a piece
of paper and place this over a magnetized bar. Then
gently tap the paper. The filings will arrange
themselves in curved lines extending from one pole
to the other, these lines will run side by side as seen
in Fig. 50, and will not cross each other. This is
because the magnetic influence is not confined to the
immediate vicinity of the magnet, and the filings
coming within the field in which the magnetic force
extends become magnetized. The area in which the
magnetic force is felt is spoken of as the magnetic field
or the fi^ld of force, and the attraction which tends to
arrange the iron filings in the curved lines is spoken of
as the lines of force.

Electrici^ and Magnetism 121

This property of magnets is of great value, for the
action of the electromagnets in dynamos, motors, in-
duction coils, and other kinds of electrical apparatus
is largely dependent upon it.

It was Michael Faraday, an English physicist, who,
about the middle of the nineteenth century, discovered
that a current of electricity
could be induced in a wire by
moving it in a magnetic field,
and who devised the appliance
that was the forerunner of the
dynamo and many other elec-
trical devices in use at the
present time.

Electromagnets. — Soft iron
is more easily magnetized than
steel, but the latter maintains
its magnetic properties for a
long time, while the former P'«-S'- ItONPoiNGa

, ., c- I. • . OM Paper over Bar

soon loses them. Soft iron is ,, o „,

MAGNET, S B O W I N C

very readily magnetized by magnetic Fieu> and
electricity, but it ceases to be Lines of Force.
a magnet as soon as the cur-
rent stops. Iron magnetized in this way is called
an electromagaet. A common type of electromagnet
consists of a core of soft iron or iron wire wound with
insulated wire. The iron becomes magnetized by the
cturent passing through the wire.

A ample form of electromagnet and the method of
its action were referred to in the description of the
electric bell, page 113. Another similar form of electro-
magnet is that inserted in the framework of the front
door in some apartment houses, in sudi a way that,
when it is magnetised by the closing of the circuit, it

122 Physics and Chemistry

draws the door catch back, allowing the door to be
opened. The circuit is closed by the pressing of a
button in an apartment. A large numb^ of electrical
appliances and motors are operated in much the same
way.

Galvanic and faradic currents. — By a galvanic
current or galvanism is meant a current obtained from
a chemical cell or battery; by a faradic or induced
current is understood a current that is induced in a
conductor by the action of a magnet or an electrified
body that is not connected to it.

The current produced by dynamos and induction
coils are examples of induced currents. Induced
currents are known also as secondary currents.
Induced currents that flow first in one direction and
then in the other along the secondary coil are called
alternating currents. Those that flow in one direc-
tion only are called direct currents.

Induction coils. — ^The essential parts of an indue-
tion coil, see Fig. 52, arc a core of soft iron (c) around
which are wound a few turns of coarse copper wire.
This wire, which is known as the primary coil, is con-
nected into the circuit of a battery (b). At its
connection with the battery, it is in contact
fine steel spring (d), at the end of which is a piece
soft iron. This acts as a current interrupter. Over
the primary coil is wound what is known as the sec*
ondary coil. This consists of a great many turns of
fine copper wire. The ends of the secondary coil ter-
xninate in what are known as the spark points (sp).
When the circuit is closed, the current flows through
the primary coil, magnetizing the iron core. This
attracts the spring, ptdling it back, which breaks the

circuit, The core thereupon looes it$ magnetism, th^

Electricity and Magnetism 123

spring falls back, and the current is remade. This
cycle is repeated so long as the coil is in action, thus
the current is being continuously interrupted, though
only momentarily. This is of importance in the

o o-

J. d—.-O

Fig. 52. Diagram Showing Paxt of an Induction

Coil.

(b), Battery,
(c), Primary ooiL
(D), Spring.
(s, p), Spark points.

action of the apparatus. The magnetic field created
by the current in the primary coil induces a current
in the secondary coil which, as the wire composing
it is much longer and finer than that of the pri- .
mary coil, is much stro nger than that in the latter. ^^ .
The reason for this will be seen later. When the
current is suflSciently strongs spark points pass be*

124 Physics and Chemistry

tween the secx)ndary terminals (s, p). Induction coils
form essential parts of many kinds of electrical ap-
paratus. The various varieties of faradic induction
machines used in electrotherapy are modifications
of it.

Electric Currents as a Source of Heat and Light

Heat effects of electric currents. — ^Whenever an
electric current passes along a wire conductor, the
latter becomes heated. The degree to which it will
do so depends upon two things — viz., the strength of
the current and the amount of resistance offered by
the conductor to the passage of the current. The
amotmt of resistance will depend largely upon : (i) The
kind of wire used, some metals being poorer conductors
and thus offering more resistance than others. (2) The
length of the wire; the longer the wire, the greater
the resistance. (3) The circumference of the wire; the
greater the circumference of the wire, the easier it
will be for the current to pass and thus the less
will be the resistance. (4) The temperature of the
wire; less resistance is offered by a cold, than by a
hot, wire.

Since resistance to a current causes heat, wires
that will offer the least resistance are used for service
wires and those intended to carry a current wanted
to produce mechanical or chemical results; since, if
heat is not required, to have any unnecessary energy
expended as heat means a loss, as there will be then
just that much less energy left to accomplish the
work for which the current is intended. On the other

Electricity and Magnetism 125

hand, where heat is required, means ate taken to
secure a varying amount of resistanoe» the amount
depending upon the intensity of heat required. For
instance, in the electric furnaces used to reduce ores,
material is used that will offer tremendous resistance
to the current, and an excessively high temperature,
3000^ C and over, is attained. Of course, the greater
the resbtance provided, the stronger must be the
current used. Iron and platinum wire will offer more
resistance than copper and will therefore become
hotter.

The heating element of an electric flatiron usually
consists of a coil of fine wire. This is placed within
a hollow iron casing which it heats. Electric warming
pads consist of coiled wire enclosed in asbestos cloth
and coverefl with flannel. Electric stoves are heated
by a coil of wire embedded in enamel that is baked to
the iimer side of the metal serving for the top. In
electric broilers and toasters the heat is radiated from
coiled wire fastened to the framework. The various
other heating appliances in common use are made in
these or similar manners, the heating principle of the
majority being some kind of fine wire that is so coiled
that a long piece can be used in a small space.

Electric lights. — The two common forms of electric
lights are the incandescent electric lights and the arc
Ught.

Incandescent lights. — Since a high degree of heat is
necessary to produce light, two requirements of the
wire filaments used as the lighting element of incan-
descent lights are that they offer a high degree of
resistance to the current and that they are melted
only at temperatures considerably above that at which
they become incandescent. Tungsten, tantalum, and

126 Physics and Chemistry

a carbon filament — made by carboni2dng a special
kind of cotton thread — ^answer these requirements.
Until lately carbon filaments were almost tmiversally
used, but the metals tungsten and tantaltim, though
more fragile and expensive, stand a higher temperature
than the latter and can be arranged so that they will
give a stronger light without the use of any extra
current. They are, in fact, more than twice as efiBicient
as the carbon lamp. Filaments of both these metals
offer less resistance than carbon and therefore it is
necessary for them to be longer than those made of
carbon, and they are therefore differently arranged
as can be seen by comparing a tungsten or mazda
lamp with one that has a carbon filament. The
longer the filament, the brighter the light will be.
The lighting filament is encased in a glass ^lobe from
which air has been exhausted and which is filled with
gas. If air were present, the filament would be
oxidized and rendered useless. The two ends of a
filament are connected to platinum wires which are
sealed into the small glass tubes that project from
the screw into the bulb. Platinum is used for this
purpose because it is one of the few substances that
is contracted and expanded at the same rate as glass
by changes in temperature, and the glass would be
broken were it in contact with a substance that did
otherwise. The platinum wires are separated from
each other by insulating material and are connected
in the screw to separate pieces of metal. The screw
fits into a socket provided with similar pieces of metal
to which the two service wires (that from the anode
and the cathode of the electric machine) are connected.
As the metals of the screw and lamp come in con-
tact when the switch is turned, the circuit is then

Electricity and Magnetism 127

closed and the current flows through the lighting fila-
ment, which is almost instantaneously heated to
incandescence.

Arc lights. — ^The lighting principle of the arc light,
formerly much used for lighting streets, large buildings,
and other purposes requiring a powerful light, con-
sists of two carbon rods. These are in contact when
the current is turned off, but as soon as it is turned on
it passes through an electromagnet which magnetizes
an iron bar from which the upper carbon is suspended
and this pulls the carbons about three-eighths of an
inch apart leaving a space that is known as the arc.
At the same time, the upper carbon is heated to a
white heat and, when this happens, it gives off in-
candescent particles which jump across the arc.
The lower carbon also becomes heated, but the upper
carbon always serves as the anode, the current passing
from it to the lower one and out. The incandescent
particles, likewise, pass from the anode tothe cathode "^
and, consequently, the upper carbon becomes dented '
in the center and the lower one becomes cone-shaped.
Both carbons wear away, but the upper one more
quickly than the lower. As this happens the gap
between the two increases in size and they must be
brought nearer together. On street lamps this is
usually done automatically by electro-magnets but
in some kinds of apparatus it must be done by hand.
Long tungsten filaments in gas-fiUed globes are now
being largely substituted for arc lights.

Meaning of Terms Used in Connection witib tiie
Measurement of Electricity

Electromotive force. — ^This term is used to signify
the pressure of electricity. A powerful current will

128 Physics and Chemistry

k\ 'have a high electromotive force and a weak one a low
^ electromotive force.

Unit. — In connection with measurement, this word
is used to denote a quantity assumed as a standard of
measurement.

Volt. — The volt (so called after Alessandro Volta,
an Italian physiologist and physicist, 1745-1827) is
the unit of electromotive force, it is the force neces-
sary to cause one ampere of ctirrent to flow against
I ohm of resistance.

Ordinary galvanic and storage cells furnish between
I and 2 volts; batteries may furnish 20 or more volts,
according to the number of cells. A very much higher
voltage can be obtained by use of the dynamo. That
employed on the trolley-car circuit is about 550 volts;
that furnished houses is between no and 220 volts.
' Ohm. — ^The ohm (named after George Ohm, a
German electrician, 1 781-1854) is the unit of electric
resistance. As stated on page 106, even the best con-
ductors offer some resistance to an electric current.

Ampere. — The ampere (called after Andr6 Maria
Ampdre, a French physicist and mathematician, 1775-
1836) is the unit of electro-current strength. It is
the amotmt of current afforded by one volt of electro-
motive force against one ohm of resistance. In other
words amperes denote the quantity of current that has
been driven through the conductor by the pressure of
the volts. A miUiampere is the thousandth (o.ooi)
part of an ampere.

Watt — The watt (named in honor of James Watt,
a Scotch physicist, 1730-1819) is the tmit of electric
power. The number of amperes multiplied by the
niunber of volts will give the ntunber of watts. A
current of 10 amperes at' 100 volts' pressure gives

Electricity and Magnetism 1^9

1 .000 watts or I kilowatt. A current of 10 amperes at
1 10 volts' pressure will give the same ntmiber of watts
as a current of 5 amperes at 220 volts' pressure because
the product in both cases is the same; thus 5X220
»iioo watts and ioXiio«iioo watts.

Formerly the lighting capacity of electric or other
kinds of lights was compared with the lighting ca-
pacity of candles, and an electric lamp was labeled as
being of a designated candle-power, but electric lamps
are now graded according to their watt consump-
tion — i. e.^ according to the amount of electrical power
or energy that they use, and, as previously stated,
this is found by multiplying the ntmiber of amperes,
or, in other words, the amount of current, by the
ntmiber of volts, i. e,, the amount of force necessary
to overcome the resistance offered to the passage of
the current by the conductor and lighting filament.

The current used on a i6-candle power carbon
incandescent light on a iio-volt circuit (i. «., a circuit
that offers an amount of resistance that requires no
volts of electromotive force to overcome) is about J^
ampere and on a 220-volt circuit about X ampere.
Such a light, therefore, would now be said to have a
55- watt power since 1 10 -J- J^ = 55 and 220 4- >^ = 55.
A 25-watt tungsten light or a i6-watt gas filled globe
will replace a 55-watt carbon incandescent light; *. «.,
it will give as bright a light without requiring any
extra energy.

Electrical power, commonly spoken of as electricity,

is sold on the basis of what is termed a kHatuaU hour;

which is the amount of electrical energy that would

exert a power of 1000 watts for one hour, or one of 100

watts for 10 hours, or of 50 watts for 20 hours, etc.

It is the quantity of current and the amount of force
9

130 Physics and Chemistry

necessary to overcome the degree of resistance offered
to the passage of the current that are the principal
factors in determining the amount of fuel necessary to
use in producing the current.

Electrical Measuring Instruments

Instruments for measuring the magnitude of the
current are called ammeters; those for meastmng the
electromotive are called voltmeters.

The appliances installed in houses for measuring the
amoimt of electrical power used are called galvano-
meters or wattmeters; they are, practically, combined
ammeters and voltmeters. There are different types
of these, but the e ssgntial pa rts in all kinds are a
coil of wire, a magnet, a magnetic needle, and a
dial. The main service wires and those from which
the house wires are distributed are connected to the
coil and all the current entering the house passes
through it. As soon as the circuit is closed by turn-
ing the switch for a light or other purpose, the current
begins to flow, and this induces a magnetic field within
the coil. This causes the deflection of the needle,
which is suspended in the center of the coil, and thus
the pointer on the dial is moved. The greater the
mmiber of lamps, etc., in action, the greater will be
the magnitude of the current entering; consequently,
the stronger will be the magnetic field created, and the
greater the deflection of the needle.

Fuses

When an electric current is very strong, and under
certain other conditions, the conducting wires of cir-
cuits and electrical appliances can become so highly

Electricity and Magnetism 131

heated that not only may they set fire to any combusti-
ble substance in their neighborhood, but, also, the
wires themselves may be melted. To obviate these
dangers, fuses are used. These are made of metals or
metal alloys that melt at a comparatively low tem-
perature and, by melting, break the circuit. This
accident, which is often spoken of as blowing out the\
fuse, may be caused by too strong a current, or as the ,
restdt of placing unusual resistance in the path of a ;
current, as, for example, by attaching an appliance j
that is wired for a current considerably different,
either stronger or weaker, from that of the house /
attachments, or by getting water between the pieces > ^
of contact metal in the socket and screw — ^water J '
being a very poor conductor of electricity offers much
more resistance to a current than metal.

Fuses, especially those used in houses, are encased
in fireproof material.

Transformers

A transformer is a special variety of induction coil
by means of which the strength of a current can be
changed. For example, when buildings a long dis-
tance from the power house are supplied with elec-
tricity, a current must be sent along the main service
wires that would be of too high voltage to introduce
into the majority of buildings with safety; therefore a
transformer is placed where the service wires for the
building or buildings and the main wires connect.
Sntiall trapsformers that can be attached to the electric
light sockets in the same way as lamps or other
appliances are often used in houses when a weaker
current is needed for any purpose as, for instance,

13^ Physics and Chemistry

running electrical toys. It is important, before tising
new electrical appliances, to ascertain if they have the
same watt power as the lamps. The reason for this
was given in the section on fuses.

Rheostat '

The rheostat is an appliance placed on some kinds
of electrical apparatus to control the amount of current
passing to them. This, in the case of heating appli-
ances, means also a control of the amount of heat, i j

There are di£Eerent kinds of rheostats, but the
variety generally used on household electrical appli-
ances consists of series of coils of wire in a small case.
Projecting from the interior of the case is what is
called a contact arm. This can be moved from right
to left, and vice versa. When its knob is opposite the
word law, it is shutting off part of the current and the
temperature of the appliance will be at its lowest;
when the knob is opposite the word full, all the current
is entering the apparatus and its temperatiire is
raised.

Static Electricity

The term static (from stasis a Greek word signif3dng
standing) is, as previously stated, applied to electricity
that is not flowing along a conductor — for example,
that made manifest in Experiment ii by friction.
Static electricity has been defined as electricity in a
state of tension. It is, however, as stated in the pre-
ceding chapter, exactly the same kind of electricity as
that of the electric current, which we have been con-
sidering; the difference being, not in the electricity,
but in the conditions under which the electrification
is produced.

Electricity and Magnetism 133

The chemical battery and the dynamo, as shown in
the preceding pages, are, so long as their circuit is
closed, and they are prepared for action, driving a
constant stream of electrons along their conductors.
Machines such as the Winchester static machine,
which is much used in electrotherapy, cause their

Pic. 53. Faradic Induction Machinb.

poles, by friction or other means, to become differently
charged — i. e., they cause one pole to assume an elec-
tro-negative and the other an electro-positive charge.
If the poles are then brought into apposition, or if
any substance that will act as a conductor is placed
between them, an electrical discharge takes place,
and the poles then attain a state of electrical equi-
librium, and there is no further discharge until one
pole is once more made to acquire a positive and the
other a negative charge.
Thus static electricity is said to manifest itself by

134 Physics and Chemistry

attractions and reptilsions (this was demonstrated in
Experiment ii) and in more or less violent discharges,
a discharge bringing about a state of equilibrium.

Nature of lightning. — Lightning is a discharge of
electricity between two clouds or between a cloud
and the earth, due to one cloud acquiring a positive
and the other a negative charge, or, if the discharge is
between a doud and the earth, the difference in charge
is between them.

Physiological Action of Electricity

When electricity is applied to the animal body,
nerve stimulation results; this induces muscular
contraction, which increases metabolism, improves
muscle tone, and stimulates the circulation of the
blood and lymph. By these means body nutrition
and tone may be much improved.

When an individual takes hold of, or is between
and in contact with, the electrodes, as the padded
poles on the end of the rheophores' are called in
electrotherapy, he becomes a part of the circuit.

Cathode Rays

When the terminals of an induction coil are sealed
into a glass tube from which all air has been expelled,
invisible radiations, called cathode rays, are found to
be emitted by the cathode terminal. These fill the
tube with a brilliant yellowish fluorescent light.
Cathode ray^ are not, like light rays, reflected, re-

' The circuit wires of a battery used in electrotherapy are so

Electricity and Magnetism 135

fracted, or polarized, but they are repelled by nega-
tive electric charges, and several experiments have
shown them to act in every way as negative electric
chai|[es; they are therefore thought to be streams of
electrons shot ofi from the cathode terminal.

X-Rays or Rdntgen Rays

In 1895, Conrad Wilhelm Rontgen, of Wurtzbtirg,
Germany, discovered that if the cathode rays struck
upon the walls of the vacutun tube in which they
were generated or upon a platintun screen or other
obstacle placed within the tube, a new kind of rays
resulted. These he named X-rays^ but they are now
often spoken of as Sdntgen rays. X-rays, like
cathode rays, are neither reflected, refracted, nor po-
larized, but, unlike cathode rays, they are not de-
flected by a magnet nor repelled nor attracted by
electric charges; thus, they do not possess the char- ">
acteristi gjof e ither light or of electric charges. It is '
thought that they are simply irregular pulses or vi-
brations in the ether caused by the sudden stoppage of
the flying cathode rays, but this has not been proved.

X-rays effect the same chemical changes in a photo-
grapher's plate as light and hence can be used for
taking photographs. A peculiarity of X-ray photo-
graphs is that there is only a faint outline of the softer
tissues, while hard substances, as bone, stand out
clearly. This is because the rays have the power of
passing through, not only the glass walls of the tube
in which they are generated, but also, though in
varying degrees, such substances as the tissues of the
body. As hard matter, such as bone and metal, is
more or less impervious to these rays, the outline of

136 Physics and Chemistry

fractures or of abnormal growth upon the bone will be
clearly defined in a photograph, and, if present, any
dense, foreign substance, as a needle or bullet, will
show. Pus and other exudations in a part will ob-
scure the outline and produce a faint shadow, and thus
it is possible to detect abscess formations and the
like by means of X-ray photographs. Bismuth is
very impervious to these rays, and, if it is swallowed
with food, the course of the latter through the stomach
and intestines can be followed. This has greatly
facilitated the study of the mechanism of digestion
and is often of great assistance in diagnosing the
nature of gastric and intestinal disturbances.

X-rays are used also for therapeutic purposes in
the treatment of such diseases as lupus, cancer,
chronic ulcers, and exophthalmic goitre. The exact
nature of the action of the rays on the tissues and
abnormal deposits, which often results in the allevia-
tion or cure of such conditions, is as yet not well tm-
derstood, and neither is it known if the X-rays have
any direct effect upon micro-organisms in the tissues.

The flttoroscope. — ^This is a device used for making
examinations with the X-rays. It consists of a taper-
ing light-tight box, one end of which is provided with
a cuff which will fit closely around the face of the
examiner, and the other with a screen of cardboard or
similar substance covered with fluorescent matter such
as calcium tungstate and barium-platino-cyanide.
If a portion of the body is placed between the X-ray
tube and the fluoroscope screen, a view of the bones
and of any foreign substance, such as would be photo-
graphed, will be seen, if present in that part. The
need for the fluorescent material is that the X-rays
do not themselves affect the optic nerve in a way to

Electricity and Magnetism 137

give rise to vision, but the light which the rays cause
the fluorescent material to emit does.

Radio-Rays

In 1896, Henry Becquerel of Paris fotmd that ura-
nitun and certain of its salts and other compounds
emitted ra3rs that acted in much the same manner as
X-rays, and, in 1898, Madame Curie of Paris found
that thorium did likewise, and she fotmd later that
a substance contained in pitchblende, in very small
quantities, which she named radium^ possessed the
same properties to a very much greater degree. Sub-
stances which have this property are said to be radio-
active.

The rays emitted by radioactive substances are of
three kinds, and have been named alpha, beta, and
gamma rays.

The alpha rajrs, which have very little penetrating
power, are atoms of the gaseous element helium.
The beta rays are thought to be negative electrons
and thus they correspond to the cathode rays. The
gamma rays, it is thought, are the same as the X-rays;
they are produced by the beta rays striking against
solid particles.

Radium and its salts, chiefly the bromid and sul-
phate, are tised in the treatment of abnormal condi-
tions such as cancer, for the rays emitted by radium
are capable of producing energy and destroying tissue,
but they aSect abnormal tissue as cancer, to a greater
degree than normal; thus, with care, the normal tissue
will not be injured while the unhealthy growth is
decomposed. If raditun is put into water and allowed
to remain for some time, the water will become
charged with the emanations of the radium.

CHAPTER IX

SOUND — ^HEARING — SPEECH

Origin of Sound — Some Important Differences between Sotmd
and Light Waves — ^Transmission of Sound — ^Why Sounds
Are Heard — Causes of Differences in Sounds — Methods of
intensifying Sotmd — Echoes.

Origin of sound.— Sound can be produced by any
object that will start wave-like motion in matter that
is capable of stimulating the auditory nerves. Objects
produdng sound are usually in a state of vibration.

Three points of difference between light waves and
sound waves. — If an electric bell is suspended in a
glass bell jar to which an air ptimp is attached and the
circuit of which the bell forms a part is closed, the
strike of the bell hammer will be both seen and heard.
If, however, all the air is removed, by means of the air
pump, the bell hammer will be seen, but not heard, to
strike. This demonstrates one of the great differ-
ences between light waves and sound waves — viz.,
light waves, being vibrations of the ether, will occtu*
in a vacuimi, but sound waves, being caused by vibra-
tions in matter, cannot occur in a vacuum.

A second point of difference between light waves and

sound waves is the rate at which they travel. Light

travels, it will be remembered, at the rate of 186,000

13S

Sound — Hearing — Speech 139

miles a second. The rate at which sound travels
varies considerably in different kinds of media, but it
takes about five seconds to travel one mile in air.
It is for this reason that thunder is heard after the
flash of lightning is seen, though, as the lightning is

Pig, 54. The Beginning of a Series of Sound
Wavbs Started by a Ringing Belu

merely the spark occasioned by the discharge of
electrons and thunder the waves arising in the air as
the result of the vibration occasioned by the discharge,
both phenomena originate at the same time. Thus
the distance of the electrical disturbance can be
estimated by counting the number of seconds that
elapse between the flash of light and the sowid of the
thunder; for, as light travels so quickly, the flash is
seen the instant it occurs and, if it is posable to count

140 Physics and Chemistry

five before the thunder is heard, the electrical dis-
charge must have taken place a mile away.

The third important difference between light and
sound waves is the nature of the waves. That of
light waves has been already discussed. Sound
waves, like light waves, are produced by vibrations,
but the vibrating body giving rise to sound causes the
molecules of air, or other matter, surrounding it to
become compressed; these molectdes then rebound
and there is more space between them than there was
before they were compressed. At the same time,
they cause compression of the molecules by which
they are surrotmded, and these, in turn, act in like
manner, and so on; thus, sound waves consist of series
of alternate spherical compressions and rarefications.
The conduction of sound is analogous to the con-
duction of heat in as much as the molecules do not
move onward, but simply by their own motion
produce movement in the molecules by which they
are surrounded.

Sound transmitted by matter in its three phjrsical
states. — ^Air is the usual meditun for the transference
of sound, but it has been found to travel through
denser media more rapidly and to a greater distance
than through air. For examples: The vibrations of
the paddle wheel of a steamer in motion, when the
ear is under water, can be heard a mile away; if a long
stick of wood with one end held against the ear is
scratched with a nail, the sound will be heard by the
person whose ear is in contact with the wood, though
not by others standing equally near the source of the
sotmd; the sound waves caused by footsteps, etc.,
will pass a much greater distance in the ground, than
in the air, which is why Indians put their ears to

Sound — Hearing — Speech 141

the ground when listening for distant sounds; other
conditions being similar, distant sounds will be heard
more distinctly at the seashore than at high altitudes
where the air is less dense.

For sound waves to be transmitted by liquids and
solids, however, the sounding body must, as a rule,
act directly upon them — for example, sound waves
would not induce waves in a stone wall, but would be
thrown back from it, as will be seen later.

The mechanism of hearing. — Though sound waves
in the air will not themselves induce waves in another
medium, they wiU start bodies that are specially
arranged vibrating and thus transmit sound. It is
upon this power that hearing depends. For example,
when a person speaks, his vocal cords, by their vibra^
tory motion, cause compression of the molecules of
the surrounding air and thus give rise to sound
waves that pass by conduction, as already described,
to the hearer's ears. On entering the ear, the waves
impinge upon the drum membrane that is stretched
across the opening between the external and the
middle ears and start it vibratinjr. This membrane
transmits its motion along the three small bones
which stretch across the middle ear and connect with
the membrane that separates the middle and the
inner portions of the ear. The vibrations of this
membrane produce waves in the Uquid within that
part of the inner ear known as the cochlea. These
waves cause movement of some of the fine fibrils
stretched within the cochlea and thus stimulate the
auditory nerves over which impulses are conducted
to the center in the brain where sounds are interpreted.

The telephone. — The telephone is an example of
a more complicated means of transmitting sound. A

142 Physics and Chemistry

telephone, omitting details, may be said to consist of:
(i) a box-like portion known as the transmitter — this
has a mouthpiece in front and a diaphragm at the
back and a portion of it is filled with granular pieces
of carbon into which the electric circuit wires enter;

(2) wires, which are in connection with others from
the electric current generator and from the receiver;

(3) the receiver, $. f., the part from which the sound
is heard. The structure of the receiver is similar to
that of the transmitter. When a person speaks into
the mouthpiece of the transmitter, the sound waves
produced start the diaphragm at the back of the
transmitter vibrating; this causes fluctuations in the
electric current that correspond with the sound waves
produced by the voice, and, though transmitted from
one wire to another at the central station, these cause
the diaphragm in the receiver to vibrate and give rise
to sound waves in the air in the receiver similar to
those started in the transmitter by the voice of the
speaker.

The phonograph. — The phonograph is still another
example of the manner in which sound waves can act
upon and be reproduced by different media. Records
are made by talking, singing, etc., in front of a cone at
the back of which is a membranous diaphragm. The
latter is set in motion by the sound waves produced
by talking, etc., and transmits its motion to a sharp-
pointed instrument, known as the stylus^ which is
attached to its under surface. While the record is
being made a wax-coated disc or cylinder is kept
rotating under the stylus and the latter cuts into the
wax the impressions of the wave forms received from
the diaphragm.

The essential parts of phonographs used to repro-

Sound — H earing — Speech 143

duce sounds are the same as those on which the records
are ntiade, and when a record is placed and made to
revolve under the stylus, the latter passes in the
traces made by the other stylus and, by so doing,
moves the diaphragm, causing it to produce the same
form of waves as those which made the tracings on the
record and it thus gives rise to similar sounds.

The cones of the phonograph being different in
every respect from the human pharynx, there is,
however, a var3dng amount of difference in the tone
of sounds reproduced by phonographs.

Difference in sounds. — The differences in sotmd
are classed under three headings — ^viz., pitch, quality,
and loudness.

Pitch. — By pitch is meant the position of a sound
in the musical scale. The pitch is said to be high
when the note is up toward the treble and low when
it is down toward the base. The greater the nimiber
of vibrations per second, the higher will be the pitch
of a sound. The difference between the pitch of male
and female voices is due primarily to the different
size of the larynx and vocal cords in the two sexes,
the larynx being larger and the cords longer in men
than in women. A boy's larynx resembles the female
larynx and therefore his voice is similar. The so-
called breaking of the boy^s voice, which occurs at
puberty, is due to faulty neiu-o-muscular control
brought about in part by the very rapid growth of the
larynx and vocal cords which takes place at that time.

Quality, tone or timbre.— The quality, known also
as the tone or timbre, of sound constitutes the various
characteristics other than pitch by which one person's
voice can be distinguished from another's and one
type of musical instrument from another. Na-

144 Physics and Chemistry

turally, this depends largely upon the nature of the
part or instrument in which the sound is produced.

Differences in the nature of the material of which
musical instruments are made and in the size, shape,
and position of their different parts and the tension of
their strings will completely alter the nature of the
sounds that they can be made to produce.

Differences in voices are due chiefly to differences in
the size and shape of the vocal cords, larynx, pharynx,
and mouth, and in the degree and kind of control that
the individual has of the muscles that enter into the
formation of, and surround, these parts. The muscles
being pliable and elastic, the shape of the pharynx
and other parts concerned can be altered in speaking
and singing, and the methods of doing this most
effectively constitute one of the most important
fundamental principles of voice culture.

Also, differences in the sounds of different letters
and words are due to differences in the degree of ten-
sion and in the position and- movements of the vocal
cords and of the muscles of the pharynx, mouth, and
tongue during articulation.

Loudness. — Loudness or intensity of sound depends
chiefly upon the degree of force exerted by the vibrat-
ing body and the nearness of the hearer to the source
of the sound. It is also greatly influenced by the
density of the medium transmitting the sound (see
page 140), the presence of reflectors, and the concen-
tration of sound waves (see page 145).

Noise. — By a noise is meant a loud sound that is
disagreeable to the hearer. A noise is usually the
result of lack of regularity and rhythm of the vibra-
tions giving rise to the soimd.

Reflection of sound. — Sound waves, like light and

Sound — Hearing — Speech 145

heat waves, can be reflected or thrown back by objects
upon which they strike. Thus, the presence of a
sounding board behind a speaker makes it easier to
hear him, since the reflected wa\'es ser\*e to reinforce
or strengthen the original waves. The walls of a
room, if they are not too far from the speaker, act in
the same way, and thus it is usually easier to hear
in a room than in the open air. If, howe\^r, the walls
of a room or hall are more than fifty-six feet from the
speaker there may be an echo. The reason for this
is as follows: The sensation of sound persists for
about ii^ of a second, and as sound waves, under
ordinary atmospheric conditions of temperature and
pressure, travel at the rate of about iioo feet per
second, or 100 feet in the tenth of a second, if the
walls are not more than fifty-six feet from the speaker,
the waves can reach the walls and be thrown back
to the audience before the sensation caused by the
original waves has ceased. If, however, the hall is
so large that the reflected waves do not reach the
audience before the original sensation has ceased and
yet is not large enough to prevent reflection, the
reflected waves will produce a secondary sensation
like unto the first and this is what constitutes an
echo. The nature of the reflecting surfaces greatly
influences the reflection of sound. Sound waves are
reflected much more strongly from smooth, hard walls
than from those which are carved or hung with dra-
peries. For this reason, draperies are sometimes
used to prevent echoes.

Megaphone. Stethoscope. Ear-Trumpet. — These
are three examples of appliances used to intensify
sounds by concentration of the sound waves and» to
some extent, by reflection.

146 Physics and Chemistry

The megaphone, a hollow, cone-shaped appliance,
starts the waves produced by anyone speaking into
it in one direction and thus keeps them from spreading
as widely as usual; this greatly intensifies the sound
and increases the distance that it travels in the direc-
tion in which it was started.

The stethoscope is an instrument used for distin-
guishing sounds produced within the body. Stetho*
scopes vary in their structure, but usually consist of a
tube on one end of which is an enlarged portion con-^
taining a very delicate diaphragm and on the othet
end one or two projections that fit into the ears of the
listener. The portion containing the diaphragm is
placed over the part of the patient's body that is
being examined, and the impulses of the sounds pro-
duced by the heart, lungs, air in the cavities, or
whatever is causing sounds in the part of the body
being examined, start similar vibrations in the dia-
phragm of the stethoscope, and the waves produced
in the air in the tube by these vibrations, being con-
fined "within a limited area, are so intensified that
even slight abnormal differences of sound can be
distinguished.

The concentration of sound waves by the ear-
trtunpet so increases their force that they are able to
produce vibration in the membranes and small bones
of the ear when, as the restdt of disease or injury, these
parts have become so stiffened that they are not acted
upon by less forcible waves.

CHAPTER X

CHEMICAL REACTIONS. VALENCE. RADICALS.
CHEMICAL FORMULAS AND EQUATIONS

Nature and Causes of Chemical Reactions — Nature of Valence—
Radicals — Chemical Formulae and Equations.

Chemical reactions. — By a chemical reaction is
meant the chemical changes that take place be-
tween certain substances when they are brought
together.

Agents which promote chemical reactions. Cata-
lyzers. — Certain elements have such a strong aflSnity
for each other that, if brought into contact, they will
unite, sometimes even leaving other elements with
which they are already in combination to do so.
Many other elements, however, especially when
already combined, do not unite thus readily, and
the help of agents, such as light, heat, electricity,
is necessary to promote chemical action. As a rule,
solution facilitates — in fact, is otten necessary for —
ch^lical reactions, and there are many chemical sub-
stances and ferments that, in some unknown way,
hasten them, but do not themselves enter into the
reaction; such substances are called catalyzers ^ and
the action is termed catalysis. The action of cata-
lyzers will be demonstrated in Experiment 13.

148 Physics and Chemistry

Reason for chemical reactions. — In the preceding
paragraph it was stated that some elements have a
very strong affinity for each other, and in Chapter II
it was said the chemical affinity meant the electrical
attraction between different atoms. Thus, the prop-
erty and action that were named, before their nattire
was understood, chemical affinity and chemical union
are, in reality, electrical attraction and electrical union,
and the quality which causes certain elements to com-
bine more readily than others is thought to depend
upon the niunber and arrangement of the electrons
of their atoms which give their ions, see page 109, a
stronger or weaker negative or positive electrical
charge.

Valence or Combining Power

Nature. — It has been found that each of the ele-
ments has the jDOwer to hold a definite number of
atoms of another element or elements in combination.
This capacity is known as valence, and valence has
been defined as that property of an element which
determines the number of atoms of another element
that it can combine with. The valence of an element
is measured by the niunber of hydrogen atoms with
which one atom of the element combines to form a
molecule. Hydrogen and all elements that combine
with hydrogen atom for atom are called monovalent
or univalent elements; those which combine witlj^wo
atoms of imivalent elements are called divalent or
bivalent; those which combine with three, trivalent;
those which combine with four, tetravalent; those
which combine with five, quinquivalent. Some ele-
ments, under differing conditions, are able to exert

Valence 149

different valences; thus there are such compounds
as PeCla (ferrous chlorid) and PeCl, (ferric chlo-
rid). Such elements are said to exert a variable
valence. In chemical reactions, elements that have
the same valence replace each other atom for
atom.

In order to explain the nature of valence, it is likened
to arms or bonds and the atoms are picttu^d as hav-
ing a varjring number of arms with which they can
hold on to each other. Thus, atoms of the tmivalent
elements, such as hydrogen, sodium, potassium, are
considered as having but one arm, each atom of any
one of these elements being able to hold on to — com-
bine with — only one atom of another one-armed ele-
ment; but the oxygen atom, for example, has two
arms — is divalent — ^and can therefore hold on to two
univalent or one-armed atoms, but only one divalent;
likewise, the atoms of a trivalent element, having three
arms, can hold on to three univalent atoms, or one
univalent and one divalent, but only one trivalent,
and so on.

Valence due to electrical charges. — ^These arms are
of course merely figurative, the real agent controlling
the combining of the atoms of, at least, many of the
elements* is the electrical charge of the ions of the
elements. For instance, when a hydrogen-containing
compotmd is decomposed in water or other dissoci-
ating liquid — see page 109 — the hydrogen will have
what is said to be one positive charge and, for this
reason, it will imite with one atom of an element the

' It has not been proved that this is true of the atoms com-
posing the molecules of oxiganic substances which are not
decomposed by the electric current.

ISO Physics and Chemistry

ion of which has, what is reckoned as one negative
charge, or, if the negative charge of the ion is stronger,
i. e., if it has two negative charges, two atoms of
hydrogen will unite with it. For example, a chlorin
ion has one negative charge and it and hydrogen,
which has one positive charge, combine thus — HCl,
but an oxygen ion has two negative charges and it
and hydrogen combine thus — HaO.

Stable and unstable compounds. — ^When the atoms
of an element are combined with as many other atoms
as they can hold on to, the element is said to be satis-
fied, and unless all the elements of a compound are
satisfied, the compound is unstable; for example, the
caAon atom is tetravalent and, therefore, to be
satisfied, it must be combined with four monovalent
or two divalent, or one monovalent and one trivalent
atoms, or one tetravalent atom. For this reason^
carbon dioxid (CO a) is a stable compound, but carbon
monoxid (CO) is unstable and, as soon as it comes in
contact with any element that it can unite with, it
will do so. For another example, water (HaO) is a
stable compound, but hydrogen peroxid (HaO a) is
unstable and will very readily become decomposed
into water and oxygen.

Radicals. — In many common compounds, two or
more of their atoms are very strongly united and do
not under ordinary circumstances become dissociated
in chemical reactions, but act, in every respect, as
though they were one atom. Such a combination of
atoms is termed a radical.

The valence of some of the common elements, ions
and radicals, can be seen in the following table':

^ElemetUary Chemistry^ p. 142, HoUis Godfrey. Longmazis,
Green, & Co.

Chemical Formulas

151

Ekmeni .

Symbol

CoWMOH

Valence

EUmetU

Symbol

Common
Valence

Biomin

Zinc

Chlorin

Nitrogen

Hydrogen

Carbon

lodin

Mercury

Ions and Radicals

Potasfdtim

saver

Ammonia

Sodium

radical

NH3

Barium

Hydroxyl

Caldton

radical

Copper

Carbonate

Iron

2&3

ion

CO3

Lead

Nitrate ion

NO3

Oxygen

Sulphate ion SO4

Sulphur

Chemical Fonntilas

Definition. — By a chemical formtila is meant a
combination of symbols used to show the chemical
composition of a substance. In order to read or write
a formula correctly, it is necessary to know the sym-
bols of the elements — ^these were given in Chapter II.
— ^and to understand the meaning of certain signs
such as the following: A number placed after a sym-
bol, as stated in Chapter II., shows that in the mole-
cule there are as many atoms of the element as are
specified by the figure, but a number placed before
two or more symbols shows that there are the number
of atoms of all the elements represented by the sym-
bols following the number. For example, NajCO,
shows that there are two atoms of sodium and three of
oxygen in soditun carbonate, but sNaaCO^ implies
three molecules of sodium carbonate. Sometimes
instead of writing a number before the symbols, as in

152 Physics and Chemistry

2NAaC03, the symbols of groups of elements, of which
there are a specified number, are enclosed in parenthe-
ses. This method is more especially used when the
group of elements constitute a radical or a simple
molecule forming part of the molecule of a complete
substance. For example, the formula for glycerin may
be written C3H5 (OH) 3, there being three OH radi-
cals in a molecule of glycerin; and the formula for the
fat known as stearin, maj** be written (CiyHjsCOO),-
C3H5 showing that in a molecule of stearin there
are three molecules, each one of which consists of
CifHjsCOO, attached to one molecule consisting of
C3H5. Occasionally a period is placed before the
symtx)l of an element or group of elements, instead of
using a parenthesis, and a period is often used to
mark off an element or elements that play a special
part in a reaction; thus CUSO4.5H2O. The letter n
placed after the symbol of an element or elements
signifies an unspecified number of atoms, radicals, or
molecules, as the case may be; for instance (CeHxo-
05)n implies that a molecule of starch consists of a
number of molecules each one of which consists of
C6H10O5. When, as in the case of starch, the exact
number of simple molecules forming the more com-
plex molecule is not known the letter x is often used,
instead of the letter n.

In writing the formulae of inorganic compounds,
the symbol of the electro-positive clement, as hydrogen
and the metals, is written before that of the electro-
negative element or radical, thus, potassium hydroxid
is written KOH, and not OHK.

Different kinds of formtite. — Different groupings
of the elements are often made in writing formulae
in order to bring out some special point regarding the

Chemical Formulas 153

structure or action of the molecule. For instance,
acetic add may be written in all of the following
ways: C3H40a« this shows simply the elements and
the number of atoms constituting one molecule of the
acid; or CHjCOOH, this is to show the presence of
what is called the carhoxyl radical which is the char-
acteristic radical of organic adds; or CaHjO.OH, this
serves to show that in acetic add one hydrogen and
oxygen are always linked together; CaHjOa-H. or
H.CaHjOai are used to show that in chemical reactions
there is one hydrogen atom that is always replaced
by another element or radical;

H O
H-iv-/

H O— H

shows the manner in which, it is thought, the atoms
are linked to each other in the molecule.

A few other examples of the use of different formulae
to represent the same compound are as follows:
Water is written HaO and H-O-H ; nitrate of silver is

written AgNO, and Ag-a-N<° ; carbonic acid is

written CO,H. and C0<^«.

Formulae which show merely the elements and the
number of atoms in a molecule are called simple or
empirical formukB; those showing elements grouped
into radicals are called rational formtda; those which
show some conclusions that chemists have formed
regarding the position of atoms in molecules are called
structural or constitutional formukB. Chemists have

154 Phjrsics and Chemistry

formed such conclusions from the way in which mole-
cules act in chemical reactions.

Equations

Purpose and nature. — An equation is used to show
the nature of a chemical reaction in a concise form.
In the writing of equations, chemical symbols are
used. For example: NaOH+HCl = NaCl+HaO is
the equation for the reaction that takes place when
sodium hydroxid and hydrochloric acid are put to-
gether, and it is a concise and clear way of writing
that soditun hydroxid plus hydrochloric add forms
sodium chlorid and water.

Reversible equations, — In many chemical reac-
tions there will be sometimes some action going on
in a reverse direction; an equation to show that
such action is taking place is written as follows:
Ag-hCl ^ Aga.

By-Products

In nearly all chemical reaction there are at least
two substances formed. The most important one
of these is called the principal product, and the other
or others the by-product or by-products. In writing
an equation, the principal product is usually written
first.

Foimultt for Some Common Compounds

Acetic acid. CaH40a, or CH3COOH. '
Alcohol (ethyl). CH^O. or CaHjOH.
Alcohol (wood). CH4O, or CH3OH. ^
Aluminium chlorid. AICI3.

Chemical Formulas 155

Ammonium carbonate. (NH4)a CO3.

Ammonium chlorid. NH4CI.

Ammonium hydroxid or ammonis water. NH4OH.

Baritmi chlorid. BaCla.

Calcium chlorid. CaCU.

Calcium oxid (or lime). CaO.

Calcium hydroxid (or, when in solution, lime water).
Ca(OH)a.

Calcium hypochlorite (or hypochlorite of lime or
bleaching powder). CaOCla-

Caldtmi STilphate. CaS04.

Chloroform. CHCI3.

Dextrin. CeHioOj.

Dextrose. CeHiaOe.

Ether. (CaHs)aO.

Ferric chlorid. PeClj.

Ferrous sulphate. PeS04.

Pormaldehyd. CHaO. HcHO.

Glycerol or Glycerin. C3H5(OH)3.

Glycogen. (CeHxoOs),.

Hydrochloric acid. HCl.

Hydrogen peroxid. HaOa.

Lactose. CxaHaaOn.

Levulose. C6Hxa06.
Magnesitmi sulphate. MgS04.
Mercuric chlorid (or corrosive sublimate or bi-
chlorid of mercury). HgCU.

Mcrcurous chlorid or calomel. HgCl.

Nitric acid. HNO3.

Potassiimi bromid. KBr.

Potassium carbonate (potash, lye). KaC03.

Potassium chlorate. KCIO3.

Potassium hydroid. KOH.

Polassitun iodid. KI.

156 Physics and Chemistry

Potassium nitrate (saltpeter). ENO3.

Potassium sulphate. KaS04.

Silver nitrate. AgNOj.

Sodium bicarbonate (or baking soda). NaHCX)^.

Sodium carbonate (or washing soda). NajCOy

Sodium carbonate crystals. NaaCX)|. loHaO.

Soditun chlorid. NaCl.

Starch. CaHxoOj.

Sugar (cane, maple, etc.). CsaHaaO,

Sulphuric add. HaS04.

ii«

CHAPTER XI

MAIN DIVISIONS OF CHEMISTRY. CARBON. HYDRO-
CARBONS AND THEIR DERIVATIVES

Definitions of Oiganic and Inor:ganIc Chemistry^ — Cbaracteristics
of Organic Compounds — Isomers — Carbon Oxids — Hydro-
carbons and Some of Their Important Derivatives — Alco-
hols— Aldehyds,

The study o£ chemistry has been divided into two
main branches, viz. : inorganic chemistry, that dealing
with non-living matter such as minerals ; and organic
chemistry.

Formerly, organic chemistry was said to be the
chemistry concerned with living matter or matter
produced as the result of living processes. In the
days when this definition was given, the chemist's
work was largely analytical — i. e., the separation of
the compounds being studied into their component
parts or elements; but now, methods of synthesis —
i. e.f the building of complex substances from elements
or simple compounds by chemical reactions — are very
common and every year adds to the number of com-
pounds synthesized in chemical laboratories that it was
once thought could be made only as the restilt of the
life processes of living cells. Thus, the long accepted
definition for organic chemistry has become incorrect.

A definition that was proposed when the inade-
quacy of that hitherto used became apparent was The

158 Physics and Chemistry

chemistry of the carbon compounds^ because all
organic compounds contain carbon, but so also do a
few inorganic substances, therefore this definition,
though often used, is not very descriptive.

Some important difference between organic and
inorganic substances. — Though the supposed differ-
ence in matter which gave rise to the division of
chemistry into the two branches referred to in the
preceding paragraphs, has proved, to some extent
at least, to be non-existent, there are marked differ-
ences between the substances classed under the two
headings. Some of these are as follows: (i) Nearly
all inorganic substances are, when in solution, good
conductors of electricity, and they are dissociated by
the electric current into positive and negative ions, as
described in Chapter VII. On the contrary, very few
organic compounds are thus affected by electricity.
(2) The molecules of inorganic compounds do not
contain a large ntunber of atoms, but many of the
molecules of organic matter contain a very large
number, even thousands, of atoms and the atoms may
be combined in many different ways within the mole-
cules. For this reason, there are many organic sub-
stances, having different characteristics, that consist
of molecules made up of the same number of atoms of
the same elements. Such substances, it will be re-
membered, are called isomers. (3) Though there is
as much, if not more, variety in organic, as in inor-
ganic comjDOunds, there is exceedingly little variety
in the elements composing them, all organic substances
being composed of two or more of the following ele-
ments: carbon, hydrogen, oxygen, nitrogen, sulphur,
phosphorus, and iron. (4) All molecules of organic
substances contain carbon directly associated with

Main Divisions of Chemistry 159

either hydrogen, oxygen, or another carbon atom,
while very few inorganic substances contain carbon,
and the carbon in those which do is not combined with
the same elements that it is in the organic compounds.
Why it is possible for so many di£Ferent substances
to be formed with the same elements. — One of the
chief fundamental reasons for the production of so
many different compounds from the same elements is
that carbon atoms can combine with each other and
in doing so use only one of their valences, thus leaving
three links or arms free to combine with other elements ;
this permits of very large molecules being formed.
Also, the relative position of the carbon atoms in the
molecule may differ. This difference, the chemist
endeavors to show by certain structural formulae,
which, judging by the way in which reactions occur,
it has been conceived, may be somewhat the way in
which the atoms are linked together in the molecules.
The following are examples of such formulae:

H
H H H— C— H

H— C— H H— C— H H--C— H

I I I

H H— C— H H— C— H

Methane (CH4) I I

H H

Ethane (CaHe) Pxx)pane (CjHs)

H H

HHHHc!) HHHO H

H— O— C— C— C— C— C— C - O H— O— C— C^C--(>-C--<;--0--H

Glucose or Gmpe Sugar Practose or Fruit Sugar

(C6Hxa06) (C6HxaO<)

i6o Physics and Chemistry

H-C C— H

"-1 A-H

^H -

Benaene (C«H6)

In the first formulae the C atoms are in chains^ in
the last one they are in a ring-like form. The benzene
ring formation is often referred to in chemistry.

Carbon

Carbon is one of the most conunon elements in
nature. It is, as already stated, a constituent of
several inorganic and of all organic compounds. It
exists in the free state, as well as in combination
with other elements; also carbon atoms possess the
power of combining with themselves and, though the
element carbon is always the same, compounds of
carbon atoms can have utterly different appearances;
e, g., the dia^mond consists of nothing but carbon; yet
coke, charcoal, and graphite — ^the black substance, in
pencils known as lead — are almost, and sometimes
quite, pure carbon. Difference in pressure i^ thought
to be an important cause of different combinations of
carbon atoms; thus, excessive pressure, it is thought,
is one of the chief factors in producing the wonderful
combination of carbon atoms that results in the
diamond.

Allotropism. Allotropic forms of carbon. — The
existence of an element in more than one form with

Main Divisions of Chemistry i6i

different characteristics is known as allotropism and
the different forms are said to be aUotropic. The
allotropic forms of carbon are crystalline and amor-
phous (t. e.t without definite shape), the diamond and
graphite are crystalline, and coke, charcoal, etc.,
amorphous substances.

Carbon oxids. — Carbon unites readily with oxygen
to form CO 2 (carbon dioxid), a heavy odorless gas.
If a carbon compound is burned where there is an
instiflSdent supply of oxygen, CO (carbon monoxid)
is formed. The gas burning with a bluish flame, seen
between and directly above burning coal, is largely
CO.

,The Hydrocarbons

All organic substances will undergo disintegration,
either in the presence, or more or less complete ab-
sence, of air, but both the intermediary and final
products of disintegration produced where there is no
air differ from those arising in the presence of air.
One reason for this is that when disintegration takes
place in the air, a large portion of the carbon tmites
with oxygen, forming CO a and, of course, where there
is no air, there is no free oxygen to tmite with the
carbon. Important substances produced in nature
by the disintegration of organic substances out
of contact with oxygen are the hydrocarbons and
coal.

Nature of the hydrocarbons. — ^The hydrocarbons,
of which there are a very large number, consist
chiefly as their name implies, of carbon and hydrogen.

Classification. — ^According to the relative proportion
of carbon and hydrogen in their molecules, the hydro-

162

Physics and Chemistry

carbons are classified as belonging to the methane,
ethylene, and acetylene series. This is shown in the
following table:

Methane Series

Ethylene Series

CH4

CaH6

C3H8

C4H10

C5H12

Methane

Ethane

Propane

Butane

Pentahe

CaU4 Ethylene
C3H6 Propylene
C4H8 Butylene

Benzene Series

C6H14

Hexane

CeHd Benzene

C7H16
C8H18

Heptane
Octane

C7H8 Toluene
C8Hio Xylene

Acetylene Series

CaHa

CaH4

Acetylene
AUylene

These are only a few of the hydrocarbons known;
compounds belonging to the methane series have been
found up to Ca9H6o* In connection with chemical
formulae, such combinations of carbon and hydrogen
are spoken of as hydrocarbon radicals.

It will be noticed that the different series differ
only in the relative proportion of C and H that the
molecules contain, and that the successive substances
in each series differ from each other only in the
addition of a CHa.

Ph]rsical condition. — In general, at ordinary tem-
peratures, the hydrocarbons with less than 5 atoms of
carbon in the molecule are gaseous, those with from
5 to 16 carbon atoms are liquid, and those with a
larger number are solid.

How obtained. — Pew of the simple hydrocarbons
are found free in nature, but they occur in certain

Main Divisions of Chemistry 163

plants and as physical mixtures in petroletim and
coal tar and other complex hydrocarbon mixtures,
such as gasolene, naphtha, kerosene, natural gas, etc.,
that themselves are obtained from either petroleum
or coal tar by destructive, fractional distillation. That
the various constituents of the complex hydrocarbon
mixtures can be separated by fractional distillation is
due to the fact that they all have different boiling
points — ^the simpler the molecules of the hydrocarbon,
the lower its boiling point and thus of the temperature
at which it can be distilled, as explained in Chapter IV.
Another way in which some hydrocarbons can be pfe-
pared is by bringing together carbon and hydrogen com-
poimds that will, under existing conditions, react so that
the carbon and hydrogen wiU combine in the desired
proportions; e, g,, acetylene gas (CaHa) can be made
by mixing water and calcium carbide together. The
chemical reaction that occurs being as follows:

Calcium Water Calcium Acetylene
carbide hydroxid

CaCa + HaO = Ca(OHJa + CaHa

Source of petroleum and coal tar. — Crude petroleum
is obtained in various parts of the world from springs
and from wells dug in the earth. Coal tar is obtained
from coal bv the destructive distillation of coal.

Use of petroleum and coal-tar derivatives. — Many
of the hydrocarbons derived from petroleum and coal
tar are not only of great value in their uncombined
state, but they react with other chemicals, thereby
producing a very large ntunber of valuable compounds,
some of which are used as medicines, some as disin-
fectants, others as dyes, and others as a basis for the
preparation of various equally useful substances.

i64 Physics and Chemistry

Methane and Ethane

Two simple hydrocarbons that form bases for many
well-known compounds are methane and ethane.

Methane(CH4), commonly known as marsh gas
and fire damp, occurs free, as well as mixed with other
hydrocarbons. It is a colorless, inodorous gas that
forms explosive mixtures with air and bums. It is
the common cause of explosions in coal mines. It is
formed when vegetable matter decomposes where there
is little oxygen, and it is found rising from stagnant
pools in marshy places where it causes the appearance
of bubbles on the surface of the water. It sometimes
rises from the earth, together with similar gases, in the
neighborhood of petroleimi wells, and it is a constituent
of natural gas, coal gas, and similar mixttu^s.

Ethane (CaHe) is a gas that rises from the earth with
CH^andothergasesnearregionsinwhich there are petro-
leumsprings,anditisfounddissolvedincrudepetroleum.

Methyl chlorid, chlorofonn, etc. — ^The forming of
these compounds from methane is an example of how
this gas, ethane, and other hydrocarbons can be used
for the synthesis of more complex substances.

When methane and chlorin are put together in
diffused daylight, action takes place gradually in
which HCl (hydrochloric acid) is given off and one or
more products are obtained according to the length
of time the action is allowed to continue. These
products are the result of the displacement of one or
more hydrogen atoms by chlorin atoms as follows:

(I) CH4 + Cla - CH3CI + HQ

(2) CH,a + a, - CHaCia + HCl

(3) CHjCla + CI, - CHCI3 + HCl

(4) CHCl, + Qa - CCI4 + HQ

Main Divisions of Chemistry 165

Methyl chlorid (CH3CI) and ethyl chlorid (Ca-
H5CI), which can be made from ethane in the same
way as methyl chlorid is made from methane, are
highly inflammable, volatile gases that on striking
the skin, volatilize so quickly that they freeze the
tissue. CHCI3 chloroform (tri-chlor-methan) is the
non-inflammable volatile liquid much used as a
general anaesthetic. Other compounds can be made
from methane and ethane by using bromin or iodin,
instead of chlorin. The yellow antiseptic powder
known as iodoform (tri-iodo-methan), for example, is
CHI3.

Though methyl and ethyl chlorid, iodoform, and a
very large number of similar substances can be thus
synthesized in the laboratory, for commercial pur-
poses, they are usually made by using more complex
substances that, by chemical reactions, will produce
the same combination of elements as those obtained
by synthesis. For example, chloroform is made with
alcohol and bleaching powder (CaOCla) and iodo-
form is made by bringing iodin in contact with an
alkali.

Alcohols

Alcohols are sometimes classed with the hydro-
carbon derivatives, for they can be synthesized from
hydrocarbons, though this is not the manner in which
they are made for commercial purposes.

The chemicals necessary for the reaction that pro-
duces alcohols from hydrocarbons wiU not unite
with the latter in their natural state and it is necessary
to have a preliminary reaction that will form substances
which will react with the essential elements. The

i66 Physics and Chemistry

halogens' — either chlorin, bromin, or iodin — are
often used for this purpose. For instance:

Methane^ Chlorin Methyl Chlorid Hydrochloric acid
CH4 + CI2 - CH3CL 4- HCl

and
Methyl Chlorid Sodium Hydrozid Wood Alcohol Sodium Chlorid
ChjCl 4- NaOH - CH3OH + NaCl

In the same way ethyl or grain alcohol (CaHjOH)
can be made from ethane; propane alcohol from pro-
pane, and so on.

Methyl or wood alcohol and ethyl or grain alcohol
are the alcohols in common use. Ordinarily, the
former is made by the destructive distillation of
wood (as described in Chapter IV.), and grain alcohol
by the fermentation of glucose, see Chapter XIX.

Alcohols are said to be hydroxids of the hydrocarbons
for, as can be seen by the following formulae, they have
a hydrocarbon and a hydroxid radical.

CH3.OH (methyl-wood-alcohol).
C2H5.OH (ethyl-grain-alcohol).
C3H7.OH (propylalcohol).
C4H9.OH (butyl alcohol).
C5H1Z.OH (amyl alcohol).

The above examples have only one hydroxid radical,
but alcohols containing two or more can be made
from the higher hydrocarbons. The only one of such
alcohols that need be referred to here is glycerin or,
as it is often termed in chemistry, glycerol. This
can be made from propane and it has three OH
radicals. As glycerin, C3H5(OH)3, has three radicals
which can be replaced by other radicals or elements
in a chemical reaction it is said to be trivalent.

* The term halogen is derived from a Greek word meaning the
sea . Chlorin , iodm , bromin , and flourin were so classed because
obtained from sea salt or seaweed.

Main Divisions of Chemistry 167

Though glycerin can be made from propane, it is
ordinarily prepared from fat, of which, as \rill be seen
in Chapter XVI., it is the base.

Aldehydes

When a primary alcohol is oxidized (see page 174) it
is converted first into an aldehyde, then into an acid,
and finally into carbon dioxid and water. The
difference in the composition of an alcohol and an
aldehyde consists of a lack of two H atoms in the
latter, since the 0, in the process of oxidation, com-
bines with two H atoms of the alcohol to form water
(HaO). Thus:

Alcohols Aldehydes

CH3OH + O « CH2O + H2O
CaHsOH 4- O - CaH40 4- HaO

The aldehyde formed by the oxidation of methyl
alcohol is the disinfectant gas known as formaldehyde,
and the aldehyde of ethyl alcohol is called acetic
aldehyde. The add produced from formaldehyde is
called formic acid, and that from acetic aldehyde,
acetic acid. The chemical reactions that occur in the
oxidation of these aldehydes and adds can be seen by
the following equations :

Aldehydes Adds

CHaO + O - CHaOa + O - HaO + CO,
CaH40 + O - CaH^Oa + 20 - 2HaO + COa

The aldehydes can be made from alcohol by burning
the latter in spedally constructed lamps, or by bring-
ing the alcohol in contact with an oxidizing mixttue

1 68 Physics and Chemistry

(one that will readily part with some of its oxygen) , as
potassium bichromate and dilute sulphuric add.

Formaldehyde gas is soluble in water up to 40%.
The solution of the gas is known as formalin. The
gas can be quickly liberated from solution by the use
of certain chemicals, such as potassium permanganate,
which, when added to the formalin, oxidizes some of
the formaldehyde and in so doing produces heat
enough to volatilize the rest of it. It is often procured
in this way for the disinfection of rooms.

CHAPTER Xn

OXYGEN

The Occiirreiice and Nature of O xy g en — N ature of Oxidation,
Spontaneous Combustion, Oxids, Fireproof Material, Fire
Extinguishers, Products of Oxidation.

OccuiTence. — Oxygen is the most common element
in nature. It exists free {i.e., not in chemical combi-
nation with other elements) in the air; it, in combi-
nation with hydrogen, forms water, and, united with
different elements, it constitutes nearly one half of
the rocks and other substances forming the earth's
crust; also, it is one of the essential constituents
of animal and vegetable matter.

How obtained. — When the majority of compounds

and elements are heated they will take oxygen from

the air very readily, but, though oxygen exists free

in the atmosphere; it is not easily extracted from

it for laboratory purposes or when a large supply

of the pure gas is required. Therefore, for such

ptirposes, oxygen is usually obtained by extracting

it from some substance that contains a comparatively

large amount of it and parts with it readily. The

substances most frequently used are potassium

chlorate, manganese dioxid, and mercuric oxid.

When potassium chlorate and manganese dioxid are

169

170 Physics and Chemistry

mixed, the oxygen is liberated at a much lower tempera-
ture than it is when either of these two chemicals is
used alone, and when it is used with the potassium
no change occurs in the manganese. By what means
the manganese hastens the liberation of oxygen
from the potassiiun chlorate is not known. When
used in this way the manganese is called a catalyzer.
(See page 147.)

Experiment 13. Objects: To study (i) a method
of reducing a compound to its constituent parts;
(2) a method of liberating a gaseous clement from a
compound and collecting the gas; (3) the properties
of oxygen; (4) the use of a catalyzer.

Articles required: An iron stand with a clasp,
a large-sized, hard-glass test tube, a Btmsen burner, a
wide-mouthed bottle filled with water, a similar bottle
empty, two glass squares large enough to cover and
extend slightly beyond the mouth of each bottle,
glass tubing bent as in Fig. 55, a pan about 5^ full
of water, potassium chlorate (KaClOj), manganese
dioxid (MnOa).

Directions: Some members of the class put about
10 grams of potassium chlorate into their test tubes,
and the others 10 grams of potassium chlorate and 3
grams of manganese dioxid (mix the two chemicals
on paper before putting them into the test tube).
Connect the apparatus as shown in Pig 55, cover the
bottle filled with water with a glass square and invert
it in the pan of water, being careful not to spill the
water while doing so (because of the atmospheric
pressure on the water in the pan, that in the bottle
will not run out after the bottle is inverted). Apply
gentle heat to the part of the test tube containing the
chemical. Notice, and record, the time reqtiired to

Oxygen

171

liberate the oxygen. When the gas begins to be
evolved, insert the free end of the tubing under the
bottle ; to do so, tip one end of the bottle slightly, being
careful not to raise the opening above the surface of
the water in the pan. After the gas has displaced all

Fig. 55. (a) Apparatus for the preparation of oxygen, (b)
Shape of tube.

the water in the bottle, turn the bottle and stand it
on the table, keeping it tightly covered with the
glass square.

Partly remove the glass plate and quickly thrust a
glowing (not burning) splinter into the bottle. Re-
move at once and blow out the flame. Repeat the
process tmtil the splinter no longer ignites when thrust
into the gas.

17^ Ph3rsics and Chemistry

Use the same method with the empty bottle.
Compare results.

Into each bottle pour a little Ume water and then
shake the bottle. A milky precipitate indicates the
presence of carbon dioxid.
Experiment 14. Object: To study the result of

the union of oxygen with an
element.

Articles required: A crucible,
a triangle support, an iron stand
with ring, a Bunsen burner, a
balance, powdered zinc or iron, a
pointed glass rod.

Method : (All weights must be
absolutely accurate and shotild be
recorded at once.) Weigh the
crucible, weigh about 3 grams of
the powdered metal, weigh the
crucible and metal together and
see if the weight tallies with those
^ y ^^ I of the crucible and metal weighed
^ ^ separately. Arrange the crucible

Fia «6 Appaiulths ^^ ^^® ^^^^ ^^ ^^ ^^' 5^' support-

FOE ExpBWMBMT 14. ^^S ^^ ^ *^® tnanglc; hght the

burner and secure alow flame; put
this under, but at a distance from, the crucible. If the
zinc begins to glow or give off a white smoke, lower the
flame instantly, or there will be a loss of substance. If
a crust forms on the zinc, pierce it with the pointed
glass rod in several places so as to expose a fresh sur-
face to the air; be very careful not to lose any of the
powder in doing this, and if particles stick to the rod, tap
the latter gently against the crucible so that they will
fall back. Continue the heating for about ten minutes

Oxygen 173

and then let the crucible and its contents cool. When
the crucible is cool enough to touch, weigh it with
its contents. If the experiment has been properly
performed there will be found to be a slight gain in
weight due to the oxygen which has united with the
metal. See under Oxids, page 179.

Prom the results of these experiments answer the
following questions :

Does oxygen bum?

Does oxygen support combustion?

What became of the oxygen in the bottle during the
burning? Where did the carbon dioxid come from?

What was the difference in time required for the
liberation of oxygen when the potassiiun chlorate
was used alone and when it was used with the manga-
nese dioxid?

What is the manganese called when used in this way?

Compare what happened to the wood — a compound
— with the effect of the union of oxygen with the
metal — ^an element.

Has oxygen color?

Has it odor?

Is oxygen heavier or lighter than air? Pure air con-
sists principally of about 21 per cent, oxygen, 79 per cent,
nitrogen, an4 0.04 per cent, carbon dioxid. The atomic
weights of these elements will be fotmd on page 31.

Is oxygen lighter or heavier than pure water?
(Water consists of hydrogen and oxygen.)

Physical and chemical properties of oxygen. —
Oxygen is a colorless, odorless, tasteless gas. It is
a little heavier than air and than pure water and it is
slightly soluble in the latter.' It can be liquefied

* Fish will not live in boiled water since during boiling the
fne oxy^etit which the fish need, is expeUed.

174 Physics and Chemistry

by putting it under great pressure at a low temperature.
At low temperatures, oxygen is rather inert chemically,
for it does not combine wth many substances, but
at high temperatures, it is exceedingly active. Certain
catalyzers, however, as, for example, the enzymes
present in both animal and vegetable tissues, permit
of oxidation at comparatively low temperatures.

Oxidation and combustion. — The process of the
union of oxygen with matter, either compounds or
elements, is spoken of as oxidation. Oxidation is
always accompanied by the generation of heat. If
oxidation takes place very quickly, heat will be
evolved so rapidly that the matter may be brought
to a white heat (see page 86) or burst into flame.
When this occurs, the process is often termed coni'
bustion. When the union of oxygen with matter
goes on slowly, the heat may be developed so slowly
that it will be diflSctdt to detect it. The rusting of
iron and other metal is an example of this slow oxida-
tion, and iron rust is a form of iron oxid. Other
oxidation processes are (i) the oxidation in the body
tissues of the substances derived from food; (2) the
changing of wine, cider, etc., to vinegar and of \'inegar
and other organic acids to carbon dioxid and water;
(3) some putrefactive processes; (4) the hardening
of paint, as will be seen later, is partly due to
oxidation.

Kindling temperature. — ^As stated in a preceding
paragraph, oxygen does not ordinarily unite with
many substances at a low temperature, and the temper-
ature at which it will combine varies very greatly
with diflFerent substances, but is always the same for
each kind of substance. The temperature at which
a substance will begin to combine sufficiently rapidly

Oxygen 17s

to take fire is called the kindling temperature of that
substance or, especially in the case of liquids as the
hydrocarbons, the flash point.

Matches. — ^The various constituents of matches
furnish a good example of dijQFerences in the kindling
temperature of different substances. Formerly match
heads consisted principally of yellow phosphorus and
sulphur, and the kindling temperature of phosphorus
is so low that even a slight amount of friction caused
it to ignite; this provided sufficient heat to ignite
the sulphur, the kindling temperature of which is also
low, though not as low as the phosphorus, and the
burning sulphur heated the wood to its kindling tem-
perature. It would be too dangerous to have the
match head composed entirely of a substance that
could be ignited by friction. Even with sulphur, the
use of yellow phosphorus for match heads is danger-
ous, not only because it ignites so easily, but also
because it is excessively poisonous, therefore, its use
for matches is now forbidden by law and red phos-
phorus is used instead. This is made by heating yellow
phosphorus to about 250® C. ; it is not poisonous and it
will be ignited by friction only when it is in contact
with substances rich in oxygen, such as chlorate and
chromate of potassium and peroxid of lead. The
head of one kind of safety match contains the oxygen
compounds and the red phosphorus is on the outer
surface of the match box; thus the ignition of a
match is impossible, unless it is struck on the box.

Spontaneous combustion* — By this is meant the
sudden ignition of matter at comparatively low
temperatures when heat has not been intentionally
applied. For example, hydrocarbons, such as kero-
sene, have a low flash point, especially when they

176 Physics and Chemistry

contain certain impurities that are often present in
cheaper grades, and fires have been caused in tene-
ments in the summer time because the heat of the
rooms became raised to the degree at which the
kerosene conibined rapidly with oxygen. Painters'
rags wet with oil and turpentine, heaped together, are
the cause of many fires, because oil and turpentine
having a strong affinity for oxygen keep uniting
with it slowly and the rags, being in heaps, prevent
the escape of the heat generated by the oxidation,
so that the kindling temperature of the oil, which is
low, is soon reached and the mass suddenly bursts
into flame.

Di£Ference and similarity of the results of the
oxidation of compounds and of elements, — ^As de-
monstrated by Experiments 13 and 14, when oxygen
unites with a compound, the latter becomes dis-
sociated into simpler compounds and its elemental
constituents, but when oxygen combines with an
element, a compound substance is formed. Judging
from appearances, it might be thought that another
point of difference was an increase of bulk and weight
of the oxidized element and a loss of substance in the
compound, but it has been found that when all the
gases which escape from a compotmd as it bums are
caught and weighed, as well as the ashes which
remain, there is not only no loss of weight in the
matter btutied, but, just as in the case of the oxidized
element, a gain in weight that is equal to the amount
of oxygen that has united with the matter in the
course of combustion.

Products of combustion. — The products of combus-
tion, of course, vary according to the nature of the
matter burned, but, as already stated, all oxidation

Oxygen 177

g^ves rise to heat and all orgatdc matter, whether of
animal or vegetable origin, yields water and carbon
dioxid, for all organic substances contain carbon,
hydrogen, and oxygen. Also, there will be various
other gases combustible and incombustible, which
will pass off from the burning matter, and, usually,
there will be some uncombined carbon, mineral matter,
and other incombustible solids that wiU, for the most
part, remain as ashes, but small particles will be carried
off with the gases.

Smoke. — The hot gases, water, and other matter
arising from burning substances gradually cool as
they pass into the air and in doing so condense to
some extent, forming the doud-like matter known as
smoke. When a large amount of incombustible
matter and products of incomplete combustion are
present, the smoke will be of a dark color and,
especially when the burning material is of an oily
nature, there will be a considerable amount of matter
that will condense easily and in doing so absorb some
of the carbon and other solid substances present
in the smoke; this constitutes soot. The substances
contained in soot are not all fully oxidized and, for
this reason, if a large quantity is allowed to collect
in a chimney, it may t£^e fire, when a fire is lighted
in the stove, furnace, or fireplace.

Experiments to study the nature of combustion. —

Experiment 15.

Procedure: Arrange apparatus as in Fig. 56A,
using a hard-glass test tube for a and an ordinary one
for b. Tube c must be drawn to a point. Have small
pieces of wood in a and place lighted burner under
them. When smoke begins to issue from c, apply a
lighted match to it. There being combustible gases in

178 Physics and Chemistry

the smoke it will ignite. When the gases cease to
bum and it is impossible to relight them, remove the
charred wood from the test tube, examine it, and hold
a piece of it with the forceps in the flame.

Pig. 56A. Appakatus Used for
EXFSUUENT 15.

Does it bum with or without a flame ? See page 1 79.

Of what does this residue of the wood consist?

Test the liquid in b with litmus paper. This is
pyroUgneous add (wood vinegar) see page 193.

Experiment 16.

Articles required: Substitute a few pieces of coal
for the wood, otherwise have the same articles as for
Experiment 15, and perform experiment in same way.

Experiment 17.

Articles required: A hard-glass test tube, a test*
tube holder, about ten grams of cane sugar, a Bunsen
burner, matches.

Procedure: Put the sugar into the test tube and
hold the latter in the flame. Notice the changes that
occur in the sugar. After the sugar has turned
brown and smoke issues from the tube, apply a lighted
match to the smolce.

Oxygen 179

How do the products of the burning and burnt coal*
wood, and sugar compare?

Experiment 18.

Articles required: A wide-mouthed bottle, a glass
square, a taper or strip of wood, lime water, a beaker, a
piece of glass tubing about four or five inches in length.

Procedure: Let the taper or wood bum in the
bottle for some time, keeping the bottle covered with
the glass square as much as possible without putting
out the light. After a few minutes, put out the light
and pour a little lime water into the bottle.

Put some lime water into the beaker and blow
into it through the glass tubing.

The white substance that appears in the lime
water is calcium carbonate (CaCOj), formed by the
union of carbon dioxid (CO 2) and the calcium hydroxid
Ca (OH) a, in the water. Thus, Ca (OH) ,+COa = Ca-

COj+HaO.

Why do you get the same results from the burning
of a taper or wood and from the breath ?

Flame and incandescence. — Matter may bum
with or without a flame. If the matter is a volatile
substance, such as ether, kerosene, or alcohol, or if,
though not itself volatile, it gives off combustible
gases when heated, as do coal and wood, there will be
a flame during combustion, but matter such as solid
carbon will combine with oxygen and thereby become
so hot that it will glow, and metals and oxids may be
so highly heated that they will glow — i. e., they will
become incandescent — ^but in neither case will there
be a flame. As a rule, flame occurs only in the burning
of volatile substances.

Ozids. — ^An oxid is a compound of oxygen and an
element or radical. Thus water (HaO) is an oxid

i8o Physics and Chemistry

of hydrogen, and carbon monoxid* (CO) and carbon
dioxid (CO a) are oxids of carbon, sulphur dioxid
(SO 2) is an oxid of sulphur, and so on. There are
only two elements — ^bromin and fluorin — that will
not, tmder any drcumstance, unite with oxygen.

Nature of fireproof buildingSi clothingy etc. —
Buildings are said to be fireproof when they are
constructed of substances that are non-combustible,
or that will not bum except at excessively high
temperatures, or in the presence of free oxygen (such
are iron, concrete, stone), and of matter saturated
with oxids which have taken up all the oxygen that
they can combine with and therefore cannot bum,
btiming being nothing but the union of matter with
oxygen. Wood, clothing, and other absorbent ma-
terial can be made fireproof by being treated with
such oxids.

Fire extinguishers. — Since burning consists of the
combining of matter and oxygen, if air is excluded
from a substance, it cannot bum. Therefore, the
quickest way to check a fire is to prevent the access
of air to it. An effectual way of doing this is by the
use of a fire extinguisher containing chemicals which,
when combined, form carbon dioxid. As this gas
holds all the oxygen that it can unite with and is '
heavier than air, it will, if poured over burning matter,
act as a non-inflammable, air-proof covering. Many
extinguishers contain a flask of sulphuric acid sur-
rounded with sodiimi carbonate solution and when the
extingtiisher is tilted the acid comes in contact with the
soda and carbon dioxid is evolved. Thus: HaS04+
NaaC03«NaaS04+HaO+CO,.

■ Oxids which have but one atom of oxygen in the molecule
are called monoxids^ and those which have two atoms are called

CHAPTER Xm

FUELS AND ILLUMINANTS

The Nature and Origin of the Substances Commonly Used tor

Fuel and Lighting.

ClasEdfication of fuels. — Fuels are usually classified
as solid fuels, liquid fuels, and gaseous fuels.

The solid fuels are coal, coke, peat, wood, and
charcoal.

The liquid fuels in common use are alcohol, gaso-
line, kerosene or coal oil, and crude fuel oil.

The common gaseous fuels are coal gas, natural
gas, gasoline or air gas, and acetylene gas.

Solid Fuels

Classification of coal. — The several varieties of
coal are usually classified under three headings,
viz., anthracite or hard coal, bittiminous or soft coal,
and lignite.

Reason for differences in coal. — ^The differences
in coal are thought to be due to the stage of formation
in which the coal is when it is taken from the earth.

Origin of coal. — Coal is derived from vegetable

matter that through many thousands of years has

been undergoing decomposition out of contact with

li8i.

1 82 Physics and Chemistry

the air and, during the process, losing its hydrogen
and oxygen.

Lignite. — Lignite, a brown coal, represents a
comparatively early stage in the process of coal
formation. The word lignite is from the Latin
lignum meaning wood, and it is so called because it
still shows traces of wood structure. It contains
proportionately less ca^'bon and more oxygen and
hydrogen than the other coals, and it therefore gives
less heat than they do, because the heat value of fuels
depends principally upon the union of the carbon in
the fuel and the oxygen of the air.

Bituminous or soft coal. — This coal has passed
farther in the stage of decomposition than lignite and
has therefore lost more of its ingredients other than
carbon. The disadvantages of soft coal for heating
purposes are : (i ) that being soft and easily powdered,
it is very dirty; (2) many varieties cake as they bum,
and the caked masses require to be broken constantly
in order to allow a free draft through the fire ; and (3)
there is usually a great deal of smoke and soot from a
soft-coal fire. Bittuninous coal 3rields more heat than
lignite, but less than anthracite. Medium grades of
soft coal are considered the best coal for the manu-
facture of coke and of coal gas.

Anthracite or hard coal. — In its purest state, this
coal has lost nearly all its ingredients other than
carbon. Tlierefore it gives more heat than either
of the other two varieties. It bums with little or
no smoke, and the best varieties do not produce
any clinkers. Sulphur, a common impurity in all
kinds of coal is one of the principal causes of clinkers.

Coke. — Coke is produced by the destructive dis-
tillation of bituminous coal (see distillation, page 64),

Fuels and Illuminants 183^

It consists of free carbon mixed with varying amounts
of ash. It produces intense heat, but no flame or» if
the fire is deep, a carbon monoxid flame. See page 161 .

Peat. — Peat results from the decomposition of
mosses a;id similar plants under water. In its
natural state, it has not a high fuel value, for it con-
tains a large per cent, of water, but, of recent years,
ways of drying it have been devised that have in-
creased its fuel value very considerably.

Classification of woods. — ^Woods are classed as
soft woods and hard woods. Wood, as used for fuel,
consists principally of cellulose (C6HxoOs)2, mineral
matter, and water, and the conifer woods contain a
varying amount of resin. If there is much water,
the heat value of the wood is lessened because much
of the heat will be used in vaporizing the water; see
page 45. The wood from trees cut in winter has
less water than that from those cut at other times
because, in cold weather, there is less sap fiowing
through the trees.

Soft woods. — The soft woods most used for fuel
are pine, cedar, spruce, hemlock, poplar, willow, and
redwood. Soft woods ignite easily and are therefore
valuable for kindling, but they bum quickly and
thus, if used alone, will yield a very hot fire for a short
time, but it will reqtdre a large amount of wood to
keep up the fire. The conifers yield more heat than
other soft woods because of their resin.

Hard woods. — The hard woods most commonly
used for fuel are ash, beech, birch, sugar and black
maple, oak. A cord of hard wood and a ton of coal
are said to have about the same heat value. Weight
for weight, if properly dried, hard and soft woods
yield about the same amount of heat, but hard woods

i84 Physics and Chemistry

bum more slowly and thus last longer than soft
woods.

The mineral matter left after wood is burned con-
sists largely of potassium^ phosphorus, and calcium
compounds; thus, if the ashes are kept dry and put
into the ground they act as fertillizers, since phmts
need these salts for their growth. If the ashes are
wet, however, their value for this piupose is lessened,
for the potassium salts, which are the most important
ones, are changed to potassium hydroxid.

Charcoal. — Charcoal is obtained from wood in the
same manner as coke is from coal and its characteris-
tics are very similar to those of coke.

Liquid Fuels

The liquid fuels in most conunon use are alcohols,
gasoline, kerosene, and other so csXLedfuel oils.^

Alcohols. — ^Wood alcohol and denatured ethyl
alcohol are the alcohols used for fuel. Wood alcohol,
as stated in the preceding chapter, is made by the
destructive distillation of wood. Denatured alcohol
is ethyl alcohol plus some substance that has been
added to it in order to render it unfit for drinking.
This is used because it is cheaper than the pure alcohol,
since it is tax free, while there is a heavy tax on the
latter. Wood alcohol does not give as much heat as
ethyl alcohol and it is very poisonous. A new pro-
prietary preparation called stemo, in which the alcohol
is incorporated in a waxy substance, is now much
used instead of the liquid alcohol. Alcohol, in any
form, would be an expensive and unsatisfactory fuel

< Kerosene and similar hydrocarbon derivatives, though of aa
oil-like nature, are not true oils.

Fuels and Illuminants 185

to use for large fires, but when only a small flame is
required, as for chafing-dish cooking, it is very con-
venient to use. It is always important that the
wick of an alcohol lamp or stove should fit properly,
for if it is too small the flame may reach the alcohol
and, unless the utensil is constructed for the burning
of the alcohol directly, the results may be disastrous.

Gasoline. — This is obtained from petroleum by
fractional distillation. Gasoline has a lower specific
gravity and is more volatile than kerosene. The
latter quality makes it a more dangerous fuel, because
it volatilizes at a low temperature and the vapor,
when mixea with a certain amount of air, becomes
explosive. Quite a large amount of air is required,
however, and if the following precautions are observed
there is very little more danger attending the use of
gasoline than of any other liquid fuel: (i) The stove
must be properly cleaned and it must be always filled
before it is used; (2) the stove must be in good condi-
tion so that there will be no leakage and the wicks
must fit the burners; (3) the cover of the tube through
which the stove is filled must not be left off, nor even
loose; (4) a good quality of gasoline must be used;
(5) the light must be put out by ttiming down the
wick, never by blowing.

It is when stoves that have been partially empty
for hours are first lighted that trouble usually occurs;
because, while the stove has not been in use, the
gasoline has been volatilizing and, as the vapor has
not been burned, it has been filling the stove and mix-
ing with the air in it. As a high temperature acceler-
ates volatilization, explosions from this cause are
most likely to occur in hot weather or in a hot room.

Qualities of good gasoline. — Good gasoline has a

1 86 Physics and Chemistry

neutral reaction, a specific gravity of about .68 to
•72, and, when filtered through chamois, it leaves no
residue.

Kerosene. — Though kerosene is not as explosive as
gasoline, the same precautions are necessary in its
use and for the same reasons. It is to be remembered
that explosions occur only when the reservoir of a
stove or lamp contains definite proportions of air a;nd
vapor, or when the hydrocarbon beconies ignited,
which it can hardly do if the precautions mentioned
under ga^line are taken. Kerosene that has a
flash point below 100^ F. is not s^e for general use,
and in many cities where the temperature is Ukely
to be high at times, the law prohibits the use of a
kerosene that has a flash point below 125^ F. or 150^ F.

Kerosene stoves. — The blue-flame kerosene stoves
are usually considered the best. In the majority of
these, the oil is fed into a hollow ring at the bottom
of the burner, where it is heated to a sufficiently high
temperature to vaporize it. The vapor becomes
mixed with air in the btimer, and thus just as was the
case with the gas in the Bunsen burner, it gives a blue
flame.

Especially in oil-producing regions, crude fuel oils
that are sold under various trade names are often
used for fuel in specially constructed ranges, but only
the more refined hydrocarbons should be used in the
ordinary kerosene and gasoline stoves.

Gaseous Fuels and Illuminants

The gases generally used for fuel and lighting
ptirposes are coal gas, oil gas, water gas, nattu'al gas
(the two last named are used for lighting only in

Fuels and Illuminants 187

connection with some of the higher hydrocarbons),
acetylene gas, and gasoline or air gas.

Coal and Oil gas. — Coal gas is a product of the
destructive distillation of coal, and oil gas, of oil.
Their principal constituents are hydrogen, methane,
small quantities of other simple hydrocarbons, carbon
monoxid, carbon dioxid, nitrogen, ammonia, and a
small quantity of bisulphid of carbon.

Incandescent gas lights. — ^The nature of the coal-
gas flame was discussed in connection with the
Bunsen burner, page 9. Also, it was there shown
that the presence of free carbon in the flame increased
the light-giving properties of the gas, because the
carbon could be raised to a white heat and thereby
be rendered luminous without being disintegrated or
volatilized. As stated in the preceding chapter,
matter rendered luminous in this way is said to be
incandescent. To find a means of increasing the
amount of matter that could be made incandescent
in a flame was the object of many experiments, of
which two well-known results are the Argand burner
and the Welsbach mantle.

The Argand burner — called after the inventor —
gives a round flame in which a large amount of carbon
is liberated.

The Welsbach mantle — invented by Auer von
Welsbach — ^is made by cutting and sewing some
mercerized cotton into the reqtiired shape, using
asbestos thread for the sewing, and then saturating
the cotton with a solution of certain oxids, more
especiajly those of two rare elements known a^
thorium and cerium. In the process of manufacture,
the cotton is burned out and the liqtiid in which the
oxids were dissolved is evaporated and the oxids

i88 Physics and Chemistry

thus hardened so that the mantle, when completed,
consists of a thin, filmy cap-like structure of oxids.
This is connected with a burner that gives a non-
luminous, and, consequently, the hottest flame, and
this heats the oxids to such a degree that they give a
white luminous light six to eight times more powerful
than that produced when an ordinary illuminating
gas burner is used.

Surface combustion. — Somewhat the same principle
as that upon which the structure of the Welsbach
mantles was based is used in the surface-combustion
staves, though in the stoves heat, and not light, is
the thing desired. The stove burners are placed in
the midst of incombustible ntiaterial, such as alumina
(AlaOj) and silica (SiOa), and are so constructed that
just enough air to allow of the combustion of the gas
can enter. The gas bums without a flame and heats
the altunina, etc., to incandescence, and the heat
reflected greatly exceeds that from an ordinary gas
flame.

Natural gas. — Thjis is obtained in certain localities
by boring wells in the ground. Methane (CHJ is
its chief constituent, but it contains small quantities
of ethane (CaHe) and other simple hydrocarbons.

Water gas. — ^This gas is obtained by passing steam
through coke or anthracite coal when they are in-
tensely heated. It consists chiefly of carbon monoxid,
hydrogen, and small amounts of methane, carbon
dioxid, nitrogen, and oxygen. One great disadvantage
of water gas is that it is odorless and, consequently,
its escape from a gas pipe may escape detection.
This gas, owing to its large content of carbon mon-
oxid, is excessively poisonous; carbon monoxid
causing death by asphyxiation because it unites so

Fuels and Illuminants 189

strongly with the hemoglobin of the blood that it
is not easily displaced and, consequently, the hemo-
globin cannot unite with oxygen.

Natural gas and water gas btim with a blue flame
and are suitable for illuminating purposes only when
mixed with other gases.

Acetylene (C3H:,). This gas, as stated in Chapter
II., is, for practical purposes, produced by the inter-
action of water and caldtun carbide. It is usually
prepared in private plants for country houses that
are away from the main gas and electric lines. It is
used especially as an illuminant, but also for cooking
and heating. Unfortunately, it is exceedingly explo-
sive and not only forms explosive mixtures with air,
but, when compressed, is itself explosive. When
burned in the presence of oxygen, acetylene yields
a flame hot enough to melt iron ; thus, it is sometimes
used in a specially constructed apparatus, instead of
solder, for fastening metal joints together.

Gasoline gas. — This is another gas prepared in
private plants for country places. It is made by
allowing gasoline to volatilize in the presence of air,
the combination being regulated so that an explosive
mixture will not be formed in the pipes.

Compressed gas. — Certain of the hydrocarbon
gases are compressed and stored in cylinders that can
be shipped to country houses and institutions and
attached to their gas-supply pipes. Gas so treated
is called compressed gas.

Electricity

Electricity is rapidly replacing gas as an illuminant
and, as soon as the current can be produced more

190 Physics and Chemistry

cheaply, it will probably do so also for heating and
cooking, for it has many advantages. Two of these
are: The wires for its conveyance are cheaper to
install than the gas pipes, especially when houses
are far apart ; and it does not add to the impurities of
the air in buildings, as do other forms of illuminants.
The way in which heat and light are obtained from
an electric current was described in Chapter VIII.

CHAPTER XIV

SOLUTIONS. ACIDS. BASES AND SALTS

Different Kinds of Solutions — Different Kinds of Acids.—
Characteristics of Adds — ^Tests for Acids — Properties of
Bases and Alkalies — ^Neutralization — Different Kinds of
Salts— Alkaloids and Their Salts— Native of Pats—
Saponification — Nature of Soaps,

Solutioiis

Definitions. — ^When the word solution is used as a
verb it stands for the dissolving of a substance in a
liquid; used as a noun, it implies a liquid with some
substance dissolved in it. The liquid which is used
to dissolve a substance is called the solvent, and the
substance that is dissolved is termed the solute.
An unlimited amount of solute cannot be dissolved in a
solvent, and when the latter contains as much of a
solute as it can hold in solution at certain tempera-
tures it is said to be saturated at that temperature.
Most solutes are more soluble in hot than in cold
solvents, but there are some exceptions, e, g., calcium
hydroxid, in water, and gaseous solutes. If a solution
is saturated at a high temperature and then allowed
to cool gradually without disturbance, it will often
cool to room temperature without depositing any of
the substance from the solution. Such a solution is
said to be supersaturated. Such a solution is very un-
stable; after it has cooled, even shaking the flask in

which it is will precipitate the amount of solid that is

191

192 Physics and Chemistry

in excess of the quantity required for saturation.
Heat lessens, instead of increasing, the amount of gas
that can be held in solution, because heat increases
the molecular motion and expansion of gases more
quickly and to a greater extent than that of liquids.

Nature of matter used for solutions. — Matter in
any one of its physical states (i. e,, solid, liquid, and
gas) can be used as a solute. There are, of course,
many substances that can be dissolved only at ex-
tremely high temperattu'es, and all substances are not
soluble in the same kind of solvents. Fat, for example,
is not soluble in water or in cold alcohol, but it is
soluble in hot alcohol, alkaline solutions, ether, ben-
zene, and similar substances.

Water and alcohol are the solvents most frequently
used in making solutions. A solution for which
water is used as the solvent is called an aqueous solu-
tion, and one for which alcohol is used as the solvent
is termed an alcoholic solution,

IsotoniCi hypertonic, and hypotonic solutions. —
These terms are often used in physiology and medi-
cine when comparing the relative percentage of
salts of any kind contained in the blood and in other
solutions. By an isotonic solution is meant one that
contains the same percentage of salts as the blood;
by hypertonic, one with a higher content of salts
than the blood; by hypotonic, one with a smaller
amount of salts than the blood.

Acids

Acids are classified as organic and inorganic.
Organic acids. — ^All organic adds contain carbon
and the carboxyl or organic add radical, viz., COOH.

Solutions. Acids. Bases and Salts 193

Thus, for example, the rational formula for acetic add
is CH3COOH, for formic acid, H.COOH; for oxalic
acid (COOH)a. The following are some of the more
common important organic acids:

Acetic add CH3.CO2H Malic acid C4H6OS

Butyric '•

X1.C4X1702

Oleic

H.C18H33O,

Carbonic "

HaCOj

Oxalic *'

xi2Ca04

Citric

H3.C6HSO7

Palmitic "

H.Ci6H3t02

Formic "

H.CHOa

Stearic "

H.Ci8H350a

Lactic

H.CjHsOj

Tartaric "

Iia-C4ri406

Acetic acid is derived principally from alcohol as
the result of fermentation brought about by the
agency of a minute organism commonly called mother
of vinegar, or from the distillation of wood in the
absence of air. It is formed also in decaying fruit
from the fermentation of the fruit sugar. The sour
taste of vinegar is due to the presence of acetic add —
good vinegar containing about 6 per cent, of the apid.
The glacial form of the acid is produced by lowering
the temperature tmtil the add crystallizes. It has a
strong affinity for water and is therefore used as a
dehydrating agent (i. e, to remove water).

Carbonic acid is a weak unstable add that breaks
up into carbon dioxid and water whenever it is set
free from its salts.

Citric acid occurs in large quantities in the dtrus
fruits {i.e., lemons, grape fruit, oranges, and limes)
and slightly in quince, gooseberries, strawberries,
raspberries, currants, and cranberries.

Formic acid is fotmd in plants such as stinging
nettles, in red ants, and in a secretion in the sting of
the bee. It can be made by the oxidation of wood
alcohol.

194 Physics and Chemistry

Lactic add is formed from lactose (the sugar in
milk) when, as the result of bacterial action, it fer-
ments. The souring of milk is due to formation of this
add.

Malic acid and malates occur in apples, pears,
currants, blackberries, raspberries, quince, pineapples,
cherries, and rhubarb.

Oleic acid will be referred to in Chapter XVIII.

Oxalic acid is present in the form of salts in many
plants, such as the sorrels. It can be made by the
action of nitric add on carbohydrates and by heating
wood shavings or sawdust with caustic potash or soda.

Palmitic acidy see Chapter XVIII.

Stearic acidy see Chapter XVIII.

Tartaric acid and its salts occur chiefly in grapes.

Other important organic adds are the amino adds
and the add amides. These, of which there are a
large number, are formed both in plants and in ani-
mals. In the latter they result from the digestion
and the metabolism of protein substances.

The inorganic acids. — The more common important
inorganic adds are:

Hydrochloric or muriatic add (HCl).

Hydrobromic add (HBr).

Nitric add or aqua fortis (HNOj).

Phosphoric add (H3PO5).

Sulphuric add or oil of vitriol (HaSOJ.

Acids and hydrogen. — The molecules of all adds
have at least one atom of hydrogen that is detached
in chemical reactions, and it is upon this atom that
their add characteristics depend; losing this, they lose
their add properties. Some adds contain more
hydrogen than the detachable atom or atoms, and
when writing the formulas for such adds the replaceable

Solutions. Acids. Bases and Salts 195

hydrogen is sometimes separated by a period — thus,
H.CaHiOa. Hydrogen unites with certain elements
to produce adds; for instance, hydrogen and chlorin
unite to form hydrochloric add, hydrogen and
bromin unite to produce hydrobromic add, hydrogen
and fluorin combine to form hydrofluoric add.

Anhydrids. — Adds are formed also by the union
of certain gaseous oxids and water. For example,
nitric add, sulphuric and sulphurous add, carbonic
add, phosphoric add, are formed by the union of
water and oxids of the elements nitrogen, sulphur,
carbon, and phosphorus respectively. Such oxids are
often spoken of as anhydrids. Anhydrids are also
obtained by the abstraction of water from adds.

Strong and weak acids. — Some adds are much
•more active chemically than others; i.e., they react
more quiddy and with a greater number of substances
to form new compounds. Those which do are
classed as strong acids and those which do not as
weak acids. The important strong adds are hydro-
chloric, nitric, sulphuric, and oxalic. Tartaric and
dtric are moderately strong; and acetic, carbonict
boric, and the fatty adds — as oldc, stearic, eta
— are weak.

Properties of acids. — All adds, whether organic or
inorganic, have certain marked characteristics, viz.:
they have a sour taste; they are very soluble in
water; they contain hydrogen in loose combination
and part with it when they come in contact with
substances for which they have an afBnity. On
account of this last characteristic, adds decompose
and often dissolve many substa^nces, and they form
different compounds in the process. They act in
this way upon many metals, as will be seen in the

196 Physics and Chemistry

paragraphs devoted to salts and in Chapter XVI.
In fact, adds have such a strong affinity for basic
substances in nature and the a;nimal body that they
occur more frequently in the form of salts than in the
free state. The strong acids are very corrosive.
Their action upon metals and fabrics will be discussed
in Chapter XVI. When acids are perfectly free from
water or when they are dissolved in liquids which
do not dissociate them into ions, they do not show
add characteristics.

Tests for acids. — Certain substances that have been
named indicators are used for the detection of add
matter. The more conmion ones are: Litmus,
which is derived from a small lichen and can be
obtained in liquid or powder form or as paper dyed
with litmus; and methyl orange and phenolphthaldn
which are coal-tar products. Adds turn blue litmus
and yellow methyl orange to red, and they make
pink phenolphthaldn colorless.

Nomenclature of acids. — Acids which consist of
only one other element in addition to hydrogen are
called binary acids; those which contain three ele-
ments are dassed as ternary acids. Binary adds
are given names consisting of the prefix hydro, the
name of the second element, and the suffix ic — e.g.,
hydro-chlor-ic add. Oxygen is the third element in
the majority of adds, and many adds differ from
each other in composition only in the amount of
oxygen which they contain. When there are several
adds similar to each other save in this respect, the best
known one is given the suffix ic, e.g., chloric, sulphuric,
nitric, etc. If there is an add of the same name
containing less oxygen than that with the suffix ic, it
has the suffix ous, instead of ic; if there is a similar

Solutions. Acids. Eases and Salts 197

add with still less oxygen, it retains the suffix ous^
but it also has the prefix hypo. If a^a element forms
an add with a greater amotmt of oxygen than the ic
add, the suffix ic is retained and it has also the prefix
per. The following table of the dilorin adds illus-
trates this nomendature:

Hydrodiloric add — ^HCl
Hypochlorous " HCIO
Chlorous " HClOa

Chloric " HCIO,

Perdiloric " HCIO4

Bases and Alkalies

Definitions. — The terms bases, hydroxids, and
alkalies are often used interchangeably, but many
chemists do not consider this correct because, though
bases are alkalies, there are some substances that have
an alkaline reaction that are not true bases and
alcohols, which are hydroxids, though they resemble
bases in some respects, are not alkalies. Bases and
hydroxids are often defined as substances which produce
hydroxyl ions when dissolved in water or other dissociate
ing liquid; and alkalies as any one of a doss of compounds
which forms salts with acids and soaps with fats.

Reaction of the basesi etc. — ^The bases and majority
of hydroxids and alkalies have an alkaline reaction ; i.«.,
they change red litmus to blue, red methyl orange to
yellow, and colorless phenolphthalein to pink.

Names of some of the important bases. — ^These are:

Ammonium hydroxid or ammonia water (NH4OH).

Caldum hydroxid [Ca(OHa]. When in solution,
this is known as lime water.

Potassium hydroxid or caustic potash or lye (KOH).

Sodium hydroxid or caustic soda (NaOH).

198 Physics and Chemistry

Derivation of the term hydrozid. — The hydroxids
received their name because the elements which
form them do so by their interaction with water.
For example, if the element sodivma is dropped on
water, some of the latter will be decomposed and
the metal will at once unite with the oxygen and half
of the hydrogen, and the other part of the hydrogen
will escape in gaseous form. The reaction takes
place so quickly that sufficient heat is caused to melt
the metal, but, if the remaining water is evaporated,
the soditun hydroxid formed by the interaction will
remain as a white solid. The reaction that occurs
isasfoUows: Na+HaO = NaOH+H.

Characteristics of hydroxids. — All true hydroxids
contain the hydroxyl radical (OH) and the majority
of them consist of a metal in combination with this
radical. When bases are dissolved in water, they
dissociate into two kinds of ions one of which is
always the hydroxyl ion and the other the metal ele-
ment, as described in Chapter VII. Bases have a
soapy feeling, a brackish taste, and an alkaline re-
action. They destroy tissues by abstracting their
water, dissolving their albumin, and saponifpng the
fat. They destroy bacteria by the same means.

The action of alkalies upon albumin and fat makes
them valuable for cleansing agents, but, as will be
seen in Chapter XVI., they, like adds, cannot be used
for cleaning all kinds of substances, and when strong
basic solutions are used on absorbent material, their
action must be neutralized by the use of an add.

Neutralization

Experiment 19. Object: To study neutralization.
Artides required: An iron stand or tripod, a

Solutions. Acids. Bases and Salts 199

Bunsen burner, wire netting, an evaporating dish half
ftill of water, NaOH, HCl, litmus paper.

Dissolve a small piece of NaOH in an evaporating
dish half full of water. Add dilute HCl drop by drop
tmtil the solution will slightly redden blue litmus
paper. Place the dish on a wire netting, over the
flame and allow its contents to evaporate to dryness.
Continue the heating until the yellow color disappears
— this being due to the excess HCl that was added.
Add a little warm water and evaporate this in order
to remove all traces of the add. Test the residue
with litmus. Is it acid, alkaline, or neutral (i. «.,
neither add nor alkaline)? Taste the residue; what
is it?

Write the equation showing the reaction.

The two chemicals used for this experiment were
corrosive poisons, but, when they united, the add lost
its hydrogen atom and the base its hydroxyl radical,
these uniting to form water, while the Na and the
CI united to form a salt that was ndther add nor al-
kaline and, therefore, neutral. Thus : NaOH + HCl =
NaCl+HaO. This operation is called neutraUzaUon.

As alkalies and adds neutralize each other, adds
are used in the treatment of poisoning by alkalies and
to remove stains made by alkalies, and alkalies are
used to counteract the action of adds.

Salts

Salts and salt-like substances compose a very
large proportion of the compounds forming the earth's
crust; they enter into, and are essential for, animal
and plant tissues; in fact, they are fovmd in great
varieties everywhere in nature.

200

Physics and Chemistry

How salts are formed. — Salts may be formed by
the addition of an acid to (i) a metal, (2) the oxid of a
metal, (3) an hydroxid, (4) an alkaloid. For example :

ideua

Acid

By-Prodma

Sodium
Na

Hydrochloric
HQ

Sodium chlorid Hydrogen
NaCl + H

Zinc
Zn

Sulphuric
H,S04

Zinc Sulphate

ZnS04 + H

Magnesium
Mg

Sulphuric
H.SO4

Magnesium sulphate

MgS04 + H

liaaloxid

Acid

SaU By-Produa

Ferrous oxid
PeO

Hydrochloric
aHQ

Ferrous chlorid Water
FeClt + H«0

Hydroxid

Acid

Salt By-Produet

Sodium hydroxid
aNaOH

Sulphuric
H3SO4

Sodium sulphate

2NaS04 + aH.O

Alkaloids and their salts will be discussed later.

How salts can be dissociated. — Salts are not only
being constantly formed in nature, even in the am'mal
body, but they are also being dissociated, and they
often form new compounds after dissociation. How
easily decomposition occurs when a salt comes in
contact with a substance that has a stronger affinity
for one of its elements than those with which it is
combined, can be seen by the following experiment:

Experiment 20. Articles required: A flask; two
corks, one with one hole and the other with two holes
through the center; a thistle tube; a piece of glass
tubing bent as in F\^. 58; a bottle one third ftdl of
water; sodium chlorid (NaCl) ; sulphuric add (HaS04) ;
litmus paper.

Procedure: Put about 16 grams of NaCl into the

Solutions. Acids. Bases and Salts 201

flask, connect the apparatus as in Fig. 57. Through
the thistle tube, pour some H3SO4 upon the salt.
After action ceases, test the water with litmus paper.

The water, it will be found, is add, because the
chlorin was liberated from the sodium and the hydro-
gen from the sulphuric add, and these two gases,
which passed through
the tube to the water,
united, forming HCl.
The liquid in the flask
contains a new salt,
and it can be obt^ned
by evaporating the
liquid. Hie salt is
sodium sulphate
(Na^SO^.

Write the equation
showing what hap-
pened in the reaction.

Salts are also disso-
dated to some extent
when dissolved in „

™af— «^ =t«™« ;« P"=- 57- Apparatus Used fob
water, as shown m e«=«ment «.

Chapter VII. and the

decomposition is hastened when an electric current
is passed through the solution. The dissociation of
many salts is also hastened when their solutions are
heated. It is necessary for nurses to remember this.
An example of a very common error arising from
ignorance of the fact is the sterilizing of sodium
bicarbonate solutions. When this is done, the
patient gets very little sodium bicarbonate, the salt
having been decomposed into its ions during the
sterili^tion. If, however, as is done in many hospitals,

202 Physics and Chemistry

the qtiantity of sodium bicarbonate required for each
flask of solution is wrapped in a separate package,
sterilized by dry hecU at about 60® C. on three succes-
sive days, and added to the sterile, distilled water
shortly before use, the solution will be sterile and
the soda will not be dissociated to any extent.

Normaly acid» and basic salts. — Salts which have
neither add nor alkaline characteristics are called
neutral or normal salts. There are, however, some
salts that have add and some that have alkaline
properties. For example, any add that has more
than one replaceable hydrogen atom may be made to
form a salt with an add reaction; thus, HaS04+
2NaOH = NaaS04+2HaO. Sodium sulphate (NaaS04)
is a normal salt; but the salt formed thus, HaS04-f
NaOH = NaHS04+HaO, is an add salt, for, as can be
seen by looking at the formula, NaHS04 (add sodium
sulphate) still retains an atom of hydrogen, since there
were not suflident hydroxyl ions provided to unite with
all the hydrogen. In the same way, if a base, such as
magnesium hydroxid [Mg(OH) a], and an add, as HCl,
are brought together in such quantity that there will
be an equal ntunber of molecules of each, there will
be only half enough hydrogen for the hydroxyl ions
present, there bdng, as can be seen by the formula,
two hydroxyl ions in each molecule of the base, and the
result will be as follows: Mg(OH)a+ HCl = MgOHCl
+HaO. MgOHCl is called basic magnesium chlorid.
When theHCl is in the proportionof Mg(OH) 2+ 2HCI,
the reaction is MgCl+2HaO, and MgCl — magnesium
chlorid — ^is a normal or neutral salt.

Naming of salts. — (Read the names of the adds,
page 197.) The names of the salts are derived from
those of the bases or metals, etc., and of the adds

Solutions. Acids. Bases and Salts 203

which produced the salts. As in the case of the adds,
the suflSx usually shows the lack of oxygen or the
amount of oxygen present. A salt derived from a
binary acid generally has the suflBx id or ide, thus
chlorids are formed from hydrochloric add, bromids
from bromic add, etc. The salts of a ternary add
ending in ous have the ous changed to tie, the salts
from a ternary add with a name ending in ic have the
ic changed to ate; thus: nitrous add produces nitrites,
nitric add, nitrates; sulphurous add, sulphites,
sulphuric add, sulphates; acetic add, acetates.

Class exercise. — ^Write the equations showing
how the following salts are formed:

Sodium chlorid.

Potassium bromid.

Add sodium carbonate (bicarbonate of soda).

Carbonate of soda.

Magnesitun sulphate.

Caldtun nitrate.

Silver nitrate.

Copper sulphate.

Silver chlorid.

Alkaloids and Their Salts

The term alkaloid is derived from two Greek words
signifying aJkali-Uke, and the name was first given to
certain tmsaturated ammonia compounds of vegetable
origin which, like the alkalies, combine with adds to
form salts.

It was once thought that alkaloids were formed only
in plants, and when they werefoimd in a post-mortem
examination it was decided that the individual had
been poisoned by one of the poisonous alkaloids

204 Physics and Chemistry

derived from certain plants. It is now known,
however, that' many bacteria produce alkaloids —
ptomaines — ^in animal matter and that, after decompo-
sition of the body has set in, alkaloids from this source
may be fotmd in animal organs. Some of the impor-
tant vegetable alkaloids are morphin, strychnin,
quinin, caffein, nicotin. The majority of alkaloids
are insoluble in water, which is one reason why their
salts, and not the free alkaloids, are used as medicine.
Morphin sulphate is made from the alkaloid morphin
and sulphuric acid; strychnin sulphate, from the
alkaloid strychnin and sulphuric acid; iron and
strychnin citrate, from iron, strychnin, and citric add.

Esters or Ethereal Salts

How esters are formed. — ^Whenever an acid acts
upon an alcohol, the acid is neutralized, wholly or in
part, and a substance analogous to a salt is formed.
Thus nitric acid and ethyl alcohol combine to form
ethyl nitrate :

Alcohol Nitric add Ethyl Nitrate Water

CaHsOH + HNO3 - CaHsNOa + HaO

and acetic acid and ethyl alcohol when combined
form ethyl acetate, thus:

CaHjOH+CHjCOOH -CH^COOHCaHs+HaO

Fats

Nature of simple fats. — Fats, which in chemistry
are often spoken of as glycerids, are esters of glycerin
or, as it is often called, glycerol, and certain organic

Solutions. Acids. Bases and Salts 205

acids, known as fatty adds. The most common
of these acids are stearic, palmitic, oleic, and butyric.
Stearic add is solid, palmitic semi-solid, and oleic
and butyric are liquid at ordinary temperatures.
The fats which they form are known as stearin,
palmitin, olein, and butyrin. Glycerol, as shown on
page 166, being a triatomic alcohol, has three OH radi-
cals that can be replaced, and as fatty adds are mon-
atomic, having only one replaceable hydrogen atom,
a molecule of any one of the glycerids will consist
of one molecule of glycerin and three of fatty acids.
For example :

Glycerol Stearic Acid Stearin Water

C,H5(OH)3 + aCxSHjdOa - C3Hs(Ci8HjsOa)3 -f 3HaO

Fats will be further discussed in the chapters de-
voted to food.

Sapooification

When fat is boiled with an alkali, the glycerin
separates from the fatty adds and these unite with the
alkali, thereby forming soap. The process is called
saponification.

Saponification occurs also in the animal body, in
the small intestine under the influence of an enzyme
produced in the pancreas and the alkaline salts of the
bile and the intestinal and pancreatic juices.

Soaps, bdng formed by the interaction of acids
and a base, are analogous to salts. They will be
further considered in Chapter XVI.

CHAPTER XV

WATER

City and Country Water Supplies — Ground Water — Springs-
Wells — Classification of Foreign Substances Found in
Water — Methods of Purifying Water — ^Hard and Soft
Water — ^Methods of Softening Different Kinds of Hard
Water — Objections to the Use of Hard Water.

Water Supply

The city water supply. — A city's water supply is
brought by aqueducts or pipes from the nearest
suitable river or lake.

The water is forced into the pipes in different ways.
If the city is near a hill on which there is a lake of
sufficient size, at a high enough level to be above the
houses in the city, the pipes are arranged so that the
water will flow from the lake to the city by gravity,
and the pressure upon it by that in the lake is sufficient
to force it from the main pipes into the house pipes
and, if desired, up to a height almost to the level of
the water in the lake.

When there is no available lake, a common method

is to build a reservoir on some high land near the city

and force the water, by means of pumps, from its

lower plane to the reservoir, from which it flows to the

city in the same way as from the lake. It is often

206

Water 207

necessary to btdld an aqueduct or to lay pipes between
the site of the reservoir and the sotirce of the water
supply.

In flat countries, the water is often pumped directly
into the main pipes at the source of the supply.

Houses built on heights are often provided with
supply tanks or, as they are often called, standpipes.
This is because it requires a great deal of presstire to
raise a large supply of water to a high level, and if,
when there is not much water being used, any excess
supply passes into a reservoir from which it will flow
when the amount being provided is insufiident, it
minimizes the amount of pressure that will be neces-
sary to provide an adequate supply at all times.

The cotmtry water supply. — If people living in the
cotmtry, away from the line of the main pipes, want
running water in their houses, it must be pumped
directly into the pipes supplying each house. One
form of pump used for this purpose is the windmill
pump, in which the mechanism that produces the
pressure and suction necessary to raise the water is
operated by the wheel at the top of the mill, and
the wheel is driven by the wind. As a rule, the
water is raised to a tank that is placed considerably
higher than the faucets through which it is to flow
and with which it is connected by pipes, and thus
gravity and the pressure of the water in the tank are
the two chief forces driving the water through the
pipes. Pumps that are operated by motors driven
by electrical power or power derived from the com-
bustion of gasoline or other fuel are now much used
instead of windmill pumps, when the expense of the
fuel need not be considered. The water thus pumped
into country houses may be obtained from a neigh-

2o8 Physics and Chemistry

boring lake or river, but where such does not exist a
well is the usual source of supply.

Ground water and wells. — In order to understand
how wells and springs can exist, even in countries
where rain does not fall for months at a time, it is
necessary to know that the crust of the earth is com-
posed of several different kinds of material, some of
which are very porous and others perfectly impervious
to water. In many places, these different substances
have become deposited in uneven layers or strata
with a varying depth of porous material at the top.
The water of rain and melting snow sinks through the
porous strata until it comes to a stratum of rock or
thick hard clay that prevents its passage and then it
flows or filters along the surface of this bed tmtil it
either finds an outlet into a stream, lake, or other body
of water or else it forces its way to the surface, thus
giving rise to a spring; the common cause of this is
obstruction to the flow of the water by a mass of
impervious material. The water flowing in this way
underground is called ground water and its surface
is known as the ground-water level. The depth of
the ground water will depend upon the amount of
rain or snow that falls.

In many parts of the world a non-porous stratum
dips and then rises, forming underground valleys or
basins, and the ground water flows into and fills
them. These are known as artesian basins and a well
cut into an artesian basin is known as an artesian
well. If the non-porous material forming the basin
is higher at one side than the other and extends near
enough to the surface of the ground, the water will
force an exit, thus giving rise to an artesian spring.
The size of artesian basins varies greatly; some are

Water 209

qtiite small, but some are known to be at least a
hundred miles in circumference and very deep.

Wells can be made where there is no artesian basin,
if there is a plentiful supply of ground water at a
moderate depth. It is usual in making such wells to
dig somewhat below the surface of the non-porous
stratum.

Driven wells are now more used than the old-
fashioned open well. A driven well is made by insert-
ing a pipe, that has perforations in its lower end, into
the ground to such a depth that its point is embedded
in the non-porotis stratum and its perforations are
smrounded by ground water. The upper end of the
pipe is connected to a pump. This may be a simple
hand ptunp, or a mill-wheel pump, or a motor-driven
pump.

Composition of water. — Pure water, as its chemical
symbol — HaO — shows, is an oxid of hydrogen. Water
is, however, seldom found ptire in nature for, being
an excellent solvent, it dissolves and absorbs sub-
stances from the soil and rocks through and over which
it flows, and even rain water holds in solution sub-
stances absorbed during its passage through the
air.

Foreign substances likely to be found in water. —
These may be both organic and inorganic and they
are usually considered under three headings: (i)
Those likely to be injurious to the health; (2) those
which render water unfit for cleansing and culinary
purposes; (3) those used for medidnal purposes*

It is the organic matter that has usually to be
considered with relation to the prevention of disease;
for when there is a large amount of organic matter
present, there is usually a large number of bacteria,

210 Physics and Chemistry

and some of these may be pathogenic. As a nile,
the inorganic matter in water has no harmful effect
upon the health ; in fact, its presence in drinking water
is usually considered an advantage, but, as will be
seen later, its presence in more than small amounts in
water used for cooking and cleaning, especially th^
latter, is a very great disadvantage.

Bacteria in water. — The water of streams, rivers,
lakes, ponds, and even that of oceans contains varying
numbers of bacteria. Rain water may contain a very
large number that it has gathered with the dust in its
passage through the air. The water of wells varies
very greatly in the number of bacteria it contains;
that from a deep driven well may be practically bacteria
free, since the ground through which the water has
passed has acted as a filter, but shallow wells, espe-
cially those situated near stables, privies, or where the
drainage from sinks has access, are likely to be terribly
contaminated. For the bacteria will be carried down
and for some distance through the soil with the rain
water and other fluid matter.

Kinds of bacteria in water. — The number of different
species of bacteria occurring in water is very large.
Some varieties seem to live on the surface of water as
their natural habitat, but, as far as is known, these
are not pathogenic and neither are the several varieties
of soil bacteria found in streams and near the borders
of lakes and rivers, especially after rain. The patho-
genic bacteria most frequently found in water are those
which are habitants of the intestine, and they occur
most frequently in water that receives sewage. Many
epidemics of typhoid and cholera have been traced
to such a source.

Methods of purifying water.— Large supplies of

Water 211

water are usually purified either by storing the water
in reservoirs or by filtration.

Sedimentation. — When water is stored in reservoirs,
the solid matter, including bacteria, tends to fall to the
bottom, and even pathogenic bacteria soon die for
there is nothing in the water to provide them with
food. Also, the sun's rays, to which the water is
exposed, acts as a disinfectant. This process of self-
purification by sedimentation is constantly going on
also in rivers and lakes, and it has been found that
rivers into which the sewage of a city is emptied may
be free from pathogenic bacteria several miles from
the city though highly contaminated within a con-
siderable radius of it.

Filtration. — By filtration is meant the act or process
of passing liquids through porous solids. This process
is very frequently used for the purification of both
large and small supplies of water. It is often used
in the form of filter beds in connection with reservoirs.

A variety of filter bed frequently used consists of
successive layers of stones and of coarse and fine
gravel and sand; the whole bed being i to 2 meters
thick. Such a bed is often connected by pipes with a
reservoir.

Another method of filtering frequently used is the
passing of water through filters of unglazed porcelain,
such as the Pasteur-Chamberland and the Berkfeld
filters. These two varieties of filters are very effective,
if they are frequently baked and kept clean, otherwise
they are useless. Before purchasing unknown kinds
of filters for household use it is well to have water
which has been passed through them tested, for many
filters offered for sale are quite worthless.

Sterilization. — Though a good filter will remove

212 Physics and Chemistry

nearly all germs present in water, filtration is not to be
depended upon to sterilize water that is to be used for
surgical work or, when the presence of pathogenic
bacteria is suspected, for drinking. To be sterilized,
water must.be boiled.

Distillation. — Filtration and sterilization will rid
water of bacteria, but neither process will remove the
salts that are in solution in the water. If the water is
distilled, however, nothing with a higher boiling
point than water will distill over, and thus the salts
will be left behind. For certain purposes, e, g., dis-
solving drugs and chemicals, it is often necessary to
use distilled water, since some of the salts present in
undistilled water, may tmite with a drug or chemical
and entirely change its nature. To prove this, add
about ten drops of 2% silver-nitrate solution to some
distilled water; do likewise to some tap water. The
distilled water will remain dear, but the tap water
usually becomes more or less cloudy, because water
that has not been distilled generally contains some
chlorides, and the following reaction occurs between
the chlorid and nitrate salts :

Silver nitrate Sodium chlorid Silver chlorid Sodium nitrate
AgNOj + NaQ - AgCl + NaNO,

The silver chlorid thus formed is insoluble in water,
hence the clouding of the latter. It is for this reason
that distilled water must be used for diluting the silver
preparations often used for irrigations in the treat-
ment of gonococci infections, silver chlorid being
absolutely useless for the purpose.

Experiment 21. Object : To demonstrate the effect
of distillation as compared with filtration.

Water 213

Articles required: 2 stands; 2 flasks, one half full of
water; a cork with a hole in the center; glass tubing
bent as in Fig. 58; a dish with ice in it; wire gauze; a

Fig. 58. Apparatus Aksangbd for DisntXATtON

AND Pu,TRATION.

Btmsen burner; a funnel; filter paper; 2 beakers,
one three quarters full of water; copper sulphate.

Procedure: Color the water in the flask and that
in the beaker an equally bright blue by the addition
of some copper sulphate. Line the funnel with filter
paper and suspend it above the empty beaker. Pour
the copper sulphate solution into the funnel, slowly,
80 as not to tear the paper, and allow it to filter.

214 Physics and Chemistry

Arrange the distilling apparatus as shown in Pig. 58.
Allow the water to boil. After it has done so for some
time, it will be noticed that the vapor is passing
through the tube and condensing in the empty flask.
(The ice surrounding this flask is used to hasten the
condensation by lowering the temperature.) The
distilled water, it will be noticed, is quite colorless,
since nothing but the steam (HaO) passed into the
flask, but the filtered water is about as bright a blue
after, as before, filtration.

Mineral water. — Water that flows through localities
rich in mineral matter, such as lithia, sulphur, iron,
will often contain enough of the minerals to flavor
the water; such waters are called mineral waters.
They are sometimes used for medicinal purposes.
Their nature will be further discussed in Chapter
XIX.

Nature of the salts usually present in water. —
The mineral substances that occur most frequently
in water are sodium chlorid and different compounds
of calcitmi and magnesitun.

Hard and soft waters. — When soap is put into
water part of the soap is decomposed, and if there are
lime or magnesium salts in the water they will unite
with the fatty acids set free by the decomposition
and form a lime soap which, being insoluble in water, is
precipitated in the form of a hard curd-like substance.
The soap will form no lather and, consequently, will
be of no use until enough has been used to combine
with all the calcium or magnesium present. Waters
which contain salts of lime or magnesium are, therefore,
said to destroy soap and they are called hard waters;
waters which do not contain these salts or only very
small amounts of them are said to be soft.

* ■

Water 215

How hard water can be softened. — Sometimes
the lime and magnesitmi in water are in the form
of bicarbonates (page 202) and sometimes in
the form 6f sulphates, and as both the bicar-
bonates and sulphates of lime and magnesium
are soluble in water they remain in solution. Con-
sequently, in order to remove them and thereby
soften the water, it is necessary to do something
that will render the salts insoluble so that they will
be precipitated.

Water that contains bicarbonates can be softened
by boiling because during the boiling the salts lose
CO a and are changed from soluble bicarbonate salts
to insoluble carbonates ; thus :

Cddum Calcium

bicarbonate carbonate

Ca(HC03)a + boiling - CaCOj+COa+HaO

The calcium carbonate thus formed, being insoluble
in water, is precipitated and theprecipitate is deposited
upon the floor and sides of the utensil in which the
water is boiled. Water that can be softened by
boiling (*. «., water the hardness of which is due to
bicarbonates of lime or magnesitun) is called temporary
hard water.

Hardness due to sulphates of lime, etc., cannot
be overcome by boiling, and the hardness therefore
is spoken of as permanent, thottgh, in reality, it is not
permanent, for the salts can be easily changed to
insoluble ones, and thus precipitated, by the use of
sodium carbonate, borax, ammonia, and similar
substances. When sodium carbonate is tised the
following reaction takes place:

2i6 Ph3rsics and Chemistry

Calcittm Sodium Calcium Sodium

sulphate carbonate carbonate sulphate

CaS04 + NaaCOj - CaCOs + NaaS04

The caldtun carbonate thtis formed, being insoluble,
is precipitated; the sodium sulphate, being soluble,
remains in the water, but it has not the objectionable
qualities of the caldtun sulphate.

Temporary hardness can be rectified in the same
way as permanent, as well as by boiling; thus:

Ca(HC03)a + NaaCOj - CaCO^ + aNaHCO^

The softening of water for use in laundries. —

Carbonate of soda is the agent usually used to soften
water in laundries for the general washing, and if
the soda is dissolved before being allowed to come in
contact with the clothes and no more used than re*
quired to combine with the salts present in the water, it
will do some fabrics no harm, but, if the soda is added
to the clothes in solid form or in such amount that
some of it remains uncombined in the water, it will
adhere to the clothing and, as will be seen in Chapter
XVII., this weakens and soon destroys the fabric.

Ammonia, though too expensive for general use, is
often employed to soften water for the washing of
fine fabrics, for, as it is volatile at ordinary tempera-
ttures, even if it is used in excess, it does not remain
in the meshes of the fabric and, therefore, it is much
less likely to injure material than soda. Borax, also,
injures fabric less than soda.
Objections to the use of soap for softening water. —
i Water can of course be softened without the addition

of an alkali, if a large amount of soap is used, but
there are two great objections to this : (i) the insoluble

Water 217

calcium soap that is formed adheres to the material
being washed and discolors it; (2) a much larger
quantity of soap must be used than of soda and the
soap is more expensive than soda. It has been
estimated that it requires from 2 to 2H ounces of soap
for every gallon of water that has one degree of hard-
ness' and that about .75 grams of soda will be the
equivalent of this amount of soap. As water fre-
quently has from 5 to 10 degrees of hardness and soda
is usually only about one-third the price of laundry
soap, it will be seen that if large quantities of water
are used the difference in cost will be considerable.

Softening of municipal water supplies. — Municipal
water supplies in districts where the water is unusually
hard, are often softened by adding lime to the water.
How it does so can be seen in the following equation :

Caldum Calcium

Calcium

bicarbonate hydroxid

carbonate

Water

Ca(HC03)a + Ca(OH)a

- CaCOa +

2H2O

Objections to the use of hard water. — Some
important objections to the use of hard water other
than the waste of soap and harm to clothing already
referred to are: (i) The calcium soap, formed by
the union of the fatty acids of the soap and the lime
of the water, adheres to the sides of the sinks, utensils,
etc., and reqtdres time and frequently the use of some
substance in which calcium soap is soluble, as kerosene,
to remove it; also, it helps to block the sewer pipes
into which the water is emptied. (2) In cooking

< A water is said to have one degree of hardness when it con-
tains, per gallon, as much calcium as there is in one grain of
calcium carbonate. It is said to have two de gr ees of hardness
when it has twice this amount, and so on.

2i8 Physics and Chemistry

with hard water, a deposit of lime salts forms upon the
food and often hardens it and, in the case of tea
and broths, this prevents the withdrawal of the
extractives. It has been found in some instances that,
using the same amount of tea leaves, ten ounces
of tea made with ffurly soft water is as strong
as eighteen
ounces brew-
ed with hard
water. Also,
the h*me u-
nites with the
legumin :n
peas and
beans and
makes it so
hard and
insoluble that
the vegeta-
bles cannot
be softened.
Pig. 59. Apparatus Arranged for ^3J The fur-
ExPERiMEM aa. like coating

which forms
on boilers and kettles in which hard water is
used is a very poor heat conductor; consequently, it
takes longer to heat water in utensils so coated and this
necessitates waste of fuel ; besides, there is the expense
of having the boilers deaned to be considered and
the damage to the boilers, etc.. by the overheating of
the metal which occurs when the heat is not carried
away from it by the water; then there is the danger of
an explosion should the coating crack suddenly, for,
in such case, there will be a sudden, forcible burst of a

Water 219

large quantity of s^eam which will be generate^ when
the water comes in contact with the highly heated
metal.

Experiment 22. Object: To show differences in
hard waters.

Articles required: Apparatus for generating CO 3
— viz., a flask, a thistle tube, a cork with two holes in
it, a piece of glass tubing bent as in Fig. 60; — nitric
acid; calcium carbonate; calcium sulphate; lime
water; distilled water; 2 beakers.

Procedure : (a) Arrange the apparatus for generating
CO 2 as in Fig. 59, put about 30 grams of caldum
carbonate into the flask, place the free end of the tube
in a beaker half full of lime water; pour some nitric
acid, slowly, through the thistle tube. The following
reaction then occurs:

Calcium Nitric

Calcium

carbonate acid

nitrate

L CaCOs + 2HNO3

COa+HaO + Ca(NO,)a

The CO a passes into the lime water [Ca (OH) a].
What is the white precipitate? Write the equation.
Let the CO a continue to flow into the lime water
until the latter becomes perfectly dear. Why does
it become dear?

Write the equation.

(6) Prepare permanent hard water by dissolving
0.1 gram of caldum sulphate (plaster) in 500 c. c. of
distilled water; generate CO a as in (a). Why are the
results not the same?

Experiment 23. Object: To show some methods
of softening water and of estimating the amount of
soda necessary to use for the purpose.
• Artides required: Soap solution made by shaving

220 Physics and Chemistry '

50 grams of white Castile soap, dissolving it in i liter
of hot water and filtering it ; 2 graduated c. c. measures ;
2 small flasks or bottles; calcium sulphate; distilled
water; tap water that has been boiled for 15 minutes
or more, and some that has not been boiled.

(a) Pour about 100 c. c. of the unboiled tap water
into a small flask, add some soap solution, i c. c. at a
time, and, between each addition of soap, shake the
bottle and let it stand for one minute. Do this
until a lather that will persist for one minute is formed.
Note the quantity of soap that is used before this
occurs.

Repeat the experiment with some of the boiled
water and notice the difference in the quantity of
soap used.

Experiment 24. Object : To estimate the amount
of soda that it will be necessary to use to soften water.

Procedure: Add: (i) a few drops of saturated
solution of sodium carbonate (20%) to 100 c. c. of the
unboiled water, or, if the water is not hard, water in
which calcium sulphate has been dissolved, as in
Experiment 23; and (2) i c. c. of soap solution;
shake the flask and let it stand for one minute as in
Experiment 23. If a lather is not formed, take more
water, and add a slightly larger amount of the soda
solution, and repeat the procedures. Fresh water
must be taken for each trial as the soap that is used
would assist in the softening.

If the quantity of soda necessary to use to soften
100 c. c. of water is known it will be an easy matter
to reckon the amount needed for any ntunber of
gallons.

Anyone having the supervision of a laundry should
know just how much soda per gallon of the water

Water 221

used in their laundry is required to produce a soap-
suds, without waste of soap, and how many gallons
of water is used in their washers. Knowing this, it
is an easy matter to estimate the quantity of soda
required and to regulate the amount used and thus
prevent unnecessary destruction of clothing.

Examples of fhe Different Ways in which Water is

Held in Combination

Water of crystallization. — Certain solids, when
dissolved in water, will, if the resulting solution is
allowed to evaporate, separate out in the form of
crystals. Such crystals, when heated, will give up a
definite amount of water and in so doing lose their
crystalline character; thus showing that their crystal-
line appearance was due to water. The water which
enters into combination with solids in this way is
spoken of as the water of crystallization.

Crystals which do not give up water when heated
— quartz, for instance — do not owe their crystalline
character to water.

Mechanically enclosed water. — Some crystals hold
water mechanically enclosed and not in direct combi-
nation. To see the difference of the manner in which
the two kinds of crystals part with their water, per-
form the following experiment:

Experiment 25. Procedure: Place some crystals
of copper sulphate in an evaporating dish and some
sodium chlorld in another dish and heat both of
these over Bunsen burners. The crackling sound
that occurs when the sodium chlorid becomes hot is
due to the bursting of the crystals as the water held
within them is changed to steam and expands. Such

222 Physics and Chemistry

cr3rstals are said to decrepitate. The water in the
soditim crystals is combined mechanically, that in
the copper sulphate is water of crystallization.

Examples of formttlae representing water of crys-
tallization. — ^The amount of water that certain
crystals hold mechanically is not alwa3rs the same»
but the amount of water of crystallization is always
definite for each substance that forms crystals in this
way; e.g,^ copper sulphate and water combine in the
ratio of i molecule of the copper sulphate to 5 mole-
cules of water; therefore the formula for its crystals
is CuSO^-sHaO. Calcium sulphate combines with
water to form gypsum in the ratio of i part of the salt
to 2 of water, therefore the formula for gypstun is
CaS04.2HaO.

Efflorescence. Deliquescence

Some crystals give up their water of crj^tallization
very readily, even exposure to the air resulting in
such a loss. Such compounds are said to be efflores-
cent. Other substances have exactly the opposite
quality; they will, if exposed to the air, absorb moist-
ure from it. Such compotmds are said to be delu-
quescent.

Experiment 26. Place some oystals of sodium
sulphate in an evaporating dish; in another dish place
caldtmi chlorid. Leave these exposed to the aJr for
several hours and report the result.

Because of its deliquescent property, calcium chlo-
rid, in moist climates, is sometimes put, in open
dishes, into cupboards where there are instnunents
or other articles that are injured by moisture.

Hydrated. Dehydrated* Anhydrous.— Hydrate

Water 223

and hydrated are other terms applied to hydroxids
and to substances that contain water of crystalliza-
tion, and the terms dehydrated and anhydrous are
often applied to any substance from which water has
been abstracted; e. g., anhydrous alcohol.

CHAPTER XVI

THE CHEMISTRY AND METHODS OF CLEANING

Source and Composition of Some Common Determents — Nature
and Origin of Material Used for Utensils and the Action of
Cleansing Agents in Common Use on these and on Paint,
Varnish, and Wax.

Classification of substances used for cleaning. —

According to the nature of their action, the majority
of substances used for cleaning may be classified as
solvents, saponifiers, and bleaching agents. Clean-
ing is effected also by mechanical means; e. g., friction
or rubbing, absorption and suction.

Solvents

By a solvent is meant a liquid that can dissolve
and absorb matter of any kind. AU substances are
not soluble in all kinds of liquids and there are some
compounds that cannot be dissolved at ^U under
ordinary conditions. To remove soiling matter that
is not readily soluble, it is often necessary to add some-
thing to it that will change it to a soluble substance;
e. g,f the addition of an alkali to fat in order to sa-
ponify it and thus make it soluble in water.

Effect of the temperature of solvents upon sdling

224

Chemistry of Cleaning 225

matter. — Matter is usually more soluble in hot than
in cold liquids. Protein matter (see page 277),howt
ever, is an exception to this rule because heat coagu-
lates protein; for example, it will be diflBcult to clean
bottles and other utensils in which milk has stood if
they are put into hot water before all residue of the
milk has been removed by rinsing the utensils with
cold water. Likewise, if woven fabrics, such as
cotton, linen, etc., that are stained with matter con-
taining protein — ^as blood — are put into hot water,
the protein will become so hardened into the fiber of
the material that it will be difficult to remove it.
As there is always likely to be protein matter in the
substance soiling clothing, bedding, and the like,
such things are soaked in cold water before being
subjected to hot water, and as there is usually fatty
matter in such substance the soaking in cold water
must be followed by washing in hot water — fat being
insoluble in cold water — and the use of soap or an
alkali will be necessary.

Source, nature, and use of some common solvents.
— ^Water is the solvent in most common use. Alcohol
is often used as a solvent for the removal of stains
made by drugs, many of these being soluble in alcohol
but insoluble in water. Turpentine, a volatile oil
obtained from certain species of pine, will dissolve
paint, varnish, and, to a slight extent, fat ; it is therefore
often used to remove stains made by such substances.
Fat solvents frequently used are : ether, a very volatile,
inflammable liquid obtained by the action of strong
sulphuric add upon ethyl alcohol; benzene, a color-
less, volatile, inflammable liquid obtained by distil-
lation from coal tar; benzin, a volatile, inflammable
distillate of petroleum; gasoline, which is similar to,
X9

226 Physics and Chemistry

and derived from the same source as, benzin; carbon
tetrachlorid, a non-inflammable coal tar product;
organic acids, as citric acid, which is obtained from
lemons, and oxalic add, which is made chiefly from
wood by heating sawdust and shavings with caustic
potash or soda. Ammonia will dissolve the oxids of
copper and nickel and is therefore often added to
polishes used for cleaning these metals. Kerosene
or coal oil, a distillate of petroleum, will dissolve
several of the metal oxids, especially that of iron,
therefore it is much used to remove rust from iron;
it will also dissolve the lime soap formed, as shown
in Chapter XV., when soap is put into hard water.
Oxalic acid is another oxid solvent and both it and
kerosene act ajso, to some extent, by reduction — i, e,,
uniting with oxygen and thus taking it away from
another substance.

Alkalies and Soaps

Reason for use. — Pat is the most common constit-
uent of soiling matter and thus one of the most neces-
sary procedures in general cleaning is to render the
fat soluble in water so that it can be washed away.
Alkalies do this by saponification and soap has the
same, but less pronounced, effect as the alkalies,
because, when it is dissolved in water, some of its
alkaline constituent is set free. Soap and soap pow-
ders are more frequently used than the free alkalies
for their action is sufficiently strong for ordinary
purposes and they have not the harmful effect upon
many substances that the stronger detergents have.
Alkalies, however, are necessary for some purposes,
as shown in the preceding chapter.

Chemistry of Cleaning 227

Nature and source oi fhe alkalies most frequently
used for cleaning. — The alkalies in most common
use as detergents are: Ammonia, borax, sodium and
potassium compounds.

Anunonia. — ^Ammonia water (NH^OH) can be
made by, under spedal conditions, running ammonia
gas (NH3) into water, but its common source is the
ammoniacal liquor which is produced during the de-
structive distillation of coal in the making of gas.

Borax. — Borax is a compound of soditmi, oxygen, and
boron — a non-metallic element that resembles silicon.
Borax deposits occur in various parts of the world,
principally in the deserts. Borax is much used, not
only for cleaning, but also in many industries. It is
too expensive to use for general laundry work and
scouring, but it is used for cleaning material that
would be injured by the stronger alkalies.

Potassium and sodium carbonates. — The soft,
light-weight, silver-white, metal elements, potassium
and sodium, are never found free in nature, but their
compounds are numerous and common. The com-
pounds that are of special interest in connection
with the study of detergents are the carbonates and
hydroxids.

Potash or potassium carbonate has been in use
since early in the middle ages, when it was discovered
that after wood was burned, certain soluble salts
were found in the ashes which, if boiled in pots with
water until the latter evaporated, left a solid resi-
due that had cleaning properties. This residue was
called pot-ashes. Later, it became known as potash^
lye, and potassium carbonate. Some of the potash
used to-day is made in the old way, but its more com-
mon sources are the refuse left in making beet sugar,

228 Physics and Chemistry

the grease that is taken from sheep's wool in the
washing that precedes its being made into cloth, and
natural deposits such as exist near Magdeburg, m
Saxony. These deposits are thought to have been
left after the evaporation of primeval seas.

Sodium carbonate was, in early times, prepared
from seaweeds, but during the French Revolution
the supply of seaweed was hard to get in places where
the soda was usually prepared and as, at that time,
wood was the only source of potash, it was difficult to
procure a sufficient quantity of these detergents to
supply the demand. The Academy of Paris, there-
fore, offered a prize of 25,000 livres for the discovery
of a method of making sodium carbonate from sodium
chlorid. In 1791, Le Blanc, a Frenchman, succeeded
in doing this. He added sulphuric acid to sodium
chlorid, thereby obtaining sodium sulphate, thus:
2NaCl+H2S04 = NaaS04+HCl. He then reduced
the sulphate to a sulphid by heating it with carbon,
thus:Na,S04+2C = 2NaaS+2C0a, and, finally, by
heating the sulphid with calcium carbonate, he got the
desired compound: NaaS+CaC03 = NaaC03+CaS.

Soditun carbonate can now be obtained by easier and
cheaper methods than the Le Blanc process, but never-
theless this is still extensively used in order to obtain
the HCl, which is a by-product of the first reaction.

Potassium and sodium hydrozid can be made as de-
scribed on page 198, but, for commercial purposes, they
are prepared from potassium and soditun carbonate.
Some of the several methods used in their preparation
depend upon electrolysis. The oldest method, which is
still extensively used, consists in treating the carbonate
with calcium hydroxid, thus : Na ,00 3 + Ca(OH) a « Ca-
C03+2NaOHorKaC03+CA(OH)a-2KOH-hCaC03,

Chemistry of Cleaning 229

Soaps. — Soaps are made by causing the interaction
of a fat with an alkali. When this is done, the fat
separates into its component parts — i.e., fatty adds
and glycerin — and the adds unite with the alkali,
thereby forming the soap. This interaction may be
produced (i) by what is known as the cold process y in
which the fat is combined with dther sodium or
potassitun hydroxid and dther churned or subjected
to heavy pressure ; (2) by boiling the fat with a strong
solution of either sodium or potassitun hydroxid.
Soap made by this process is in solution in the water
and glycerin, but it may be salted out by the ad-
dition of soditun chlorid to the solution, soap bdng
insoluble in salt solutions. After the soap is re-
moved, the glycerin can be freed from fordgn sub-
stances. This is, in fact, the usual source of glycerin.
Soap made by the cold process retains the glycerin in
combination. Toilet soaps are often made in this
way.

Reasons for differences in soaps. — The various
differences in soaps depend chiefly upon (i) which
alkali is used; (2) the nature of the fat used; (3) the
addition of extra substances to the soap; (4) faulty
manufacture of the soap.

Hard and soft soap. — Soaps made with sodium
hydroxid are much harder than those made with
potassium and are classed as hard soaps, while those
made with potassium are called soft soaps.

Fats of soap. — All kinds of fat are used for soap
and various oils, e.g., fish oil, olive oil, cocoanut oil,
and castor oil. Although, as stated in the preceding
paragraph, soaps made with soda are harder than
those containing potassium, the kind of fat used
and the amount of water left in the soap cause con-

230 Physics and Chemistry

siderable variation in the degree of hardness of even
the soda soaps; e, g.^ soaps made with olive and
similar oils are softer and lather more easily than those
for which tallow is used.

Substances frequently added to soap. — Various
substances, some of which are harmless and others
very objectionable, are often added to soap.

Some of the additions that, under ordinary cir-
cumstances, are harmless are perfumes; medicinal
substances — as tar and salicylic acid; emollients —
as glycerin, almond oil, and oatmeal; disinfectants
— as carbolic; such detergents as borax, kerosene, and
naphtha. These detergents increase the cleansing
value of soap for laundry purposes and, if not present
in excess, do not injure fabrics. Other detergents
sometimes added to soap are soditun and potassitun
carbonate and rosin (the resinous substance that
remains after the distillation of oil of turpentine from
the fresh pitch of pine wood ; it is known also as colo-
phony). The presence of these substances in soap
that is used for rough cleaning is not a disadvantage,
but, as will be seen in the experiments in Chapter
XVII., even dilute alkaline solutions will injure silk
and wool and they will also destroy paint and varnish,
and solutions that are at all concentrated will injure
some of the metals. Rosin, if present in more than
very small amounts, will leave yellow spots on fabrics.
For these reasons and, also, because sodium carbonate
and potash are cheaper than even cheap soaps, it is
generally considered better to buy pure soaps and,
when required, add a stronger detergent to the water,
or, for scrubbing, to use a scouring powder.

Fillers. — By fillers are meant cheap substances
with little or no detergent properties that are added

Chemistry of Cleaning 231

to soap in order to increase its weight and hardness.
The substances most commonly used for the purpose
are the sulphates of caldum and potassitun, silicates,
and chalk. Naturally, fillers are objectionable, if
for no other reason than that the buyer is pajdng for
a substance that is valueless for the purpose for which
it is bought; there is, however, another objection,
viz., when such soaps are used for laundry purposes
the fillers often leave an objectionable sand-like
deposit in the clothes.

Substances that may be present in soaps as the
result of faulty manufacture. — Definite proportions
of fat and alkali must be used in soap-making or there
will be tmcombined in the soap some of whichever
substance was present in excess. Also, the soap must
be boiled the regulation time, if saponification is to
be complete. Unless it is, there will be both free
alkali and free fat in the soap. As already stated, a
small amount of free alkali is not always objectionable,
but free fat decidedly interferes with a soap's cleans-
ing properties.

Water in soap. — ^Well made soaps do not contain
more than about 25 per cent, water, but the cheaper
grades, especially those containing fillers, often have
a much larger amount. Such soaps are comparatively
soft and dissolve very rapidly in water; therefore, to
prevent waste, they should be dried before use. This
is done by exposing the soap to the air until it loses
its moist appearance.

Castile and olive oil soaps are made of either
castor or olive oil and sodium hydroxid.

Floating soaps are made by beating the hot soap
before it solidifies and thus making it lighter by
incorporating air.

232 Physics and Chemistry

Transparent soaps of good quality are made by
dissolving soap in alcohol, filtering the resulting solu-
tion, and allowing the alcohol to evaporate. The
cheaper transparent soaps are generally made by a
cold process and usually contain free alkali.

Glycerin soaps are nearly always made by a cold
process but do not necessarily contain free alkali,
like the cheaper transparent soaps.

Mottled soaps may owe their coloring to impurities,
but that of the good grades is the result of the addi-
tion of coloring matter that does not affect the quality
of the soap.

The so-called green soap, which is extensively used
for cleaning the skin preparatory to disinfection, is
made of potassitun hydroxid and linseed oil.

The tincture of green soap is made by dissolving
green soap in alcohol and adding oil of lavender
flowers.

Experiment 27. Object : To test for the presence of
adulterants in soap. Articles required: Several sam-
ples of soap; sulphuric acid; alcohol; acetic anhydrid.

For each test, use both a pure soap and at least
one soap known to contain the adulterant for which
the lest is made. Compare all results with that ob-
tained from the pure soap.

Test for sodium and potassium carbonate. — In
separate evaporating dishes, place some small, thin
slices of each of the soaps to be tested. To each, add
a little sulphuric acid. Effervescence shows the
presence of excess of carbonates.

Test for rosin.' — Dissolve the soaps in water; acid-
ify the solution with sulphuric acid. Filter. Remove

* Rosin is not considered an adulterant, if the soap is sold as a
rosin soap.

Chemistry of Cleaning 233

the predpitate from the filter paper and dissolve it
in acetic anhydrid. Add a few drops of this solution
to about 2 c. c. of 50 per cent, sulphuric add. A
violet color indicates the presence of rosin.

Test for fillers. — Pure soaps are soluble in hot alco-
hol; the substances used as fillers are not; therefore
the test for fillers is to dissolve the soap in warm
alcohol and filter the solutions. If fillers are pres-
ent, an insoluble residue will remain on the filter
paper.

Test for free alkali. — ^But a few small pieces of soap
into a test tube with alcohol and shake the tube until
the soap is dissolved, then add a few drops of phenol-
phthalein. A pink color shows the presence of free
alkali.

Test for unsaponified fat. — Put a few thin, small
pieces of soap into a test tube with either gasoline,
ether, or benzene and shake the tube for some minutes ;
any fat present will be dissolved by these solvents.
Then filter the solution, put some of the filtrate in a
watch crystal or Petri dish, and let this stand exposed
to the air until the liquid has evaporated. If fat is
present, it will remain in the dish.

Scouring Powders

The various scotiring powders consist chiefly of
soap, soda, and, the majority of them, silica and other
rough substances such as are used for soap fillers.

Sapolio consists chiefiy of soap and sand. Its
value as a detergent is dependent chiefly upon the
friction it produces.

These detergents are very effident cleansers, espe-
cially such powders as Dutch cleq^nser and gold

234 Physics and Chemistry

dust, but they should not be used on stuf aces that
are injured by alkalies or those that are easily
abraided.

Scooring Agents Other than Soaps and Alkalies

Scouring agents that owe their cleansing properties
to the friction they produce when rubbed upon a
stuf ace are: (i) whiting and bonami, both of which
are finely pulverized chalk, the latter being pressed
into cakes; silica, an oxid of the non-metallic element
silicon (the silver polish known as silicon contains
silica compounds and whiting) ; (3) bath brick, a form
of calcareous earth pressed into the form of a brick;
it is used chiefly for cleaning steel knives; (4) rotten-
stone, known also as Tripoli, after the country in
which it was first found, a soft stone used for scouring
and polishing metals; (5) powdered emery, a variety
of corundum, a metal of extreme hardness; it is used
for scouring the harder metals, as steel; (6) carborun-
dum, a carbide of silicon that is even harder than
corundtun. It is used for the same purposes as emery.
It is made by heating coke and sand (which is an
oxid of silicon) in an electric furnace.

Bleaching Agents

Nature of bleaching. — ^Bleaching signifies making
white by removing color or dirt by the action of the sun's
rays or by a chemical process. The chemical process
may consist in: (i) The union of the bleaching agent
with the coloring or staining matter and the con-
sequent forming of a colorless compound or of a
soluble one that can be easily removed. Sulphur

Chemistry of Cleaning 235

dioxid (SO a) and sulphurous acid' (HaSO,) (which is
made by the chemical union of sulphur dioxid and
water) act in this manner. (2) Reduction; i. e., the
removal of oxygen from the staining agent thus chang-
ing it to a colorless or a soluble substance; sulphurous
add and oxalic add often remove stains in this way
and cleansing pastes and liquids used for metals
generally containing redudng agents. (3) The libera-
tion of oxygen and the union of this element with
the coloring matter thus oxidizing and, consequently,
decomposing it. The oxidizing compounds used as
bleaches may themselves contain the oxygen — e.g.
potassium permanganate (KMnO^) and hydrogen
peroxid (HaOa) — or they may act indirectly, — e. g,,
chlorin, which is the prindpal oxidizing agent acting
in this way, has a very strong affinity for hydrogen
and unites with the hydrogen of steam, setting free
the oxygen which, thereupon, unites with the coloring
matter and oxidizes it.

Chlorin also, as it is a very active element, some-
times acts by uniting with substances in the coloring
matter and forming colorless or soluble compounds.

Chlorin compounds used for bleaching. — The em-
ployment of dilorin in gaseous form for bleaching
would be both inconvenient and dangerous; therefore,
compounds which will part with their chlorin readily
are used instead. One compound that is very gen-
erally used both in factories, for the removal of the
yellow hue characteristic of freshly woven cotton and
linen fabrics, and in laundries, for the removal o^ dirt
and stains, is chlorid of lime, known also as bleaching

'The nsual method of obtaining and using sulphurous acid
for this purpose is to hang the material, after wetting it, in a
doset that can be sealed and bum sulphur in the closet.

236 Physics and Chemistry

powder. This is made by passing chlorin gas over
moist slaked lime. As the gas passes over the lime
it is absorbed by the latter.

Though the use of a bleach in laundry work is not
to be recommended, if used with care, a small amount
of bleaching powder in solution in the water in which
cotton and linen materials are washed; will not injure
the fabric, but if solid particles of the powder come
in contact with the material or if a concentrated solu-
tion is used, or if the material is not well rinsed, so as
to be absolutely freed from all trace of the bleach, the
fibers of the fabric will be soon rotted. Therefore,
to prevent damage to fabrics by the use of chlorid of
lime two precautions should be taken: (i) the powder
is to be thoroughly dissolved in water before use
(about one pound of lime to 12 gallons of water);
(2) a substance that will neutralize the action of the
bleach should be added to the first rinsing water.
Sodium thiosulphate, commonly known as hypostdphaU
of soda is often used for the purpose, for it inter-
acts with the chlorid of lime forming sodium hypo-
chlorite and calcium stdphate both of which compounds
will be removed from the material by second rinsing.
Chlorin cannot, of course, be used for removing stains
from colored material and it cannot be used for bleach-
ing or cleaning silk and wool. See experiments in
Chapter XVII.

Sodium hypochlorite, known also as Labarrague's
solution and JcmeUe water ^ is another common chlorin
bleaching agent. This is somewhat more expensive
than the bleaching powder, but it is often preferred
to the latter for laundry purposes as it does not react
with soap to produce an insoluble calcium soap as
calcium chlorid does. The action of sodium hypo-

Chemistry of Cleaning 237

chlorite should be neutralized by the addition of some
such substance as a dilute solution of hydrochloric
add or oxalic acid to the first rinsing water.

For the removal of certain stains (see page 267)
sodium chlorid, water, and lemon juice are used.
These act as follows : The citric add of the lemon juice
unites with the sodium of the salt, setting free the
chlorin, which, thereupon, unites with the hydrogen
of the water, setting free the oxygen which unites
with the staining agent and oxidizes it. This process,
like many others, is hastened by exposing the stain,
during the treatment, to the sun's rays.

Absorbents

Material that will absorb readily, such as starch,
shredded blotting-paper, and fuller's earth are often
used, dther alone or in connection with other agents,
for the removal of liquid staining matter.

Fuller's earth, which is a form of day, is so called
because used by fullers (certain cloth workers) to
absorb the oil or grease with which woolen cloth is
sometimes treated in the manufacturing process.

After reading the foregoing pages, it will be realized
that various adds and alkalies and, for cotton and
linen materials, chlorin are, either alone or as con-
stituents of compounds, the detergents in most com-
mon use. It will be interesting, therefore, to test
the action of these things on some of the materials
used for ordinary household utensils and furnishings
and for dothing; viz., metals, marble, porcelain,
glass, paint, and cotton, linen, silk, and woolen fabrics,
and to consider briefly the source and nature of these
materials.

238 Physics and Chemistry

Metals

Before testing the action of cleansing agents on
metal, it will be well to consider the nature of the
discoloration known as tarnish^ for this and» especially
in the case of kitchen utensils, fat are usually the
two most common soiling agents of metals and the
ones that are most difficult to remove.

Tarnish. — Tarnish of metals, except that of silver
and one form of copper tarnish, is generally due to
the union of oxygen with the metal. The majority
of tarnishes are thus oxids of the metals. Nearly all
metals form oxids when heated, but certain ones,
notably iron and lead, do so rapidly at ordinary tem-
peratures if there is moisture present. Under the
same conditions, aluminium, zinc, and nickel tarnish
slowly. Copper tarnishes very rapidly if heated, even
slightly, and the CO a of the air, as wcdl as oxygen and
moisture, is responsible for the reaction; thus, the
common tarnish of copper is more often a carbonate
than an oxid of copper. The tarnish of bronze and
brass is similar to that of copper. Gold and platinum
do not form oxids in the air. Tin and silver do so
only at high temperatures, but the latter tarnishes
very readily in the presence of sulphur. The usual
tarnish of silver is therefore silver sulphid (AgaS).

There is an important difference, easily perceived,
between the oxid that forms on iron and on other
metals; viz., iron oxid (FcaOj), known as rust, forms
scales or granules which rub off, and thus a fresh sur-
face is constantly exposed to the air and the metal
may soon become much eroded. The tarnish that
forms on the other metals, on the contrary, occurs as
a thin film that adheres to the surface, dulling its

Chemistry of Cleaning 2^g

luster and causing discoloration, but, being adherent,
it prevents air getting to the metal and its oxidation
is thus soon stopped; consequently, the metals are
not permanently injured. Rust on iron is partly
ferric hydroxid [Fe(0H)3], because some moisture,
the presence of which is necessary for the oxidation
of iron at low temperatures, enters into the reaction.

As will be seen in the descriptions of the metals,
those which tarnish very readily, as iron and copper,
are often protected from the air by coating them
with a metal, lacquer, or other substance that does
not tmite readily with oxygen.

Requirements of cleansdng material for metals. —
Since tarnish and fat are the two most common forms
of soil on metal, something that will remove them is
essential for an efficacious metal detergent. Acids
and alkalies will, as previously stated, remove fat, and
certain acids, partly by dissolving and partly by re-
duction, will take off tarnish, but as will be seen in
the experiment with metals neither acids nor alkalies
can be used with all metals. The hydrocarbons, as
kerosene and gasoline remove fat and some oxids.
Whiting, silicon, and similar soft, but granular sub-
stances, are valuable, for they help to provide the
friction necessary to remove soil, and they, when metal
is rubbed with soft material, stich as chamois, help
to produce a thin film over the surface of the metal
which reflects light and thus gives luster or polish.

The majority of patented preparations consists of
different combinations of substances here mentioned
or similar ones, and good preparations contain the
ingredients in proportions and combinations that
frequent trials have shown to be most efficacious;
therefore, though it costs somewhat more to buy the

240 Physics and Chemistry

combined ingredients, it is often advisable to do so.
Preparations which contain acids should not be used
on metals that are injured by adds and those con-
taining alkalies on metals affected by alkalies. The
presence of alkalies or acids in cleaning compounds
can be determined by the litmus test. Of course,
the acids, etc., likely to be present in cleaning pre-
parations would not be as strong as those xised in
experiment 28, and in such case the effect would not
be as pronounced and might be visible only after
repeated applications. Rough granular cleansing
agents, as emery, should not be used on the softer
metals.

Suitable detergents to use for the different metals
will be mentioned in the paragraphs describing the
metals.

Silicon and whiting are nearly always prepared for
use by mixing the powder with water or dilute alcohol,
and to get the best results from these and nearly all
other kinds of cleansing pastes, the metal should be
first washed with hot soapsuds, rinsed, dried, and
the paste applied with a soft, clean cloth, allowed to
dry, and then removed by rubbing with a soft, clean
doth, or chamois skin.

Experiment 28. Object: To study the effect of
adds and alkalies on different metals.

Material required: Small (about J^ inch) pieces
of bright and tarnished metal; preferably, aluminium,
copper, iron, zinc, and tin; an inorganic add, prefer-
ably hydrochloric; an organic add such as acetic;
sodium carbonate solution 10 per cent.; ammonia
water; mercuric chlorid; evaporating dishes or test
tubes; an iron stand; forceps.

Procedure: Take three bright and three tarnished

Chemistry of Cleaning 241

pieces of each of the metals and put each i>iece into a
separate evaporating dish or test tube. To a bright
and to a tarnished piece of each metal add hydro-
chloric add; to another piece of each metal, both
bright and tarnished, add acetic add; to the third set
add sodium carbonate solution.

The interaction that takes place when some metals
are treated with adds and alkalies is so great that
visible results occur immediately; some metals are
not acted upon at all by these substances and others
are acted upon so slightly that a further test is neces-
sary to see if any of the metal was dissolved. If
it was, it will be in solution in the liquid, and the test
will consist in adding something to the liquid that
will, if the metal is present, combine with it and form
a colored compound. It will be seen that there are
some metals that, themsdves, are not affected by
adds and alkalies and that have oxids that are soluble
in dther or both such liquids.

The test is as follows: After the metals have stood
for a short time in the adds and alkalies, remove them
with forceps and test the liquids, for iron, aluminium,
and copper, by adding ammonia, and for tin by adding
mercuric chlorid.

If iron is present, a red color will develop.

If altmiinium is present, a white predpitate will
form.

If copper is present, a blue color appears.

If tin is present a white predpitate forms that
turns black when the liquid is heated.

What is formed by the action of hydrochloric add
on aluminium?

(N. B. Poods containing adds should not be put
into utensils that are acted upon by adds.)
Id

242 Physics and Chemistry

Occurrence of the metals. — ^The metals are usually
found in nature in the form of oxids or of salts though
a feWp notably gold, platinum, and copper, sometimes
occur uncombined. The metal salts, as well as some
other inorganic substances^ are called minerals, and
minerals from which tiseful substances can be ex-
tracted, espedally metals, are called ores.

The metals most generally used for household
utensils and hospital laboratory appliances are
iron, zinc, nickel, tin, copper, aluminium, silver, and
platinum.

Varieties of iron. — ^The iron of commerce is never
pure, but contains varying amounts of other elements,
especially carbon, phosphorus, silicon, sulphur, and
manganese. The percentage of these elements, es-
pecially copper, present in iron changes its nature
considerably, and the amount of carbon and the form
in which it is present gives rise to three distinct
varieties of iron which are known respectively as
cast iron, wrought iron, and steel.

Cast iron and pig iron are names given to the metal
as it comes from the blast ftimace. This contains
more carbon than the other varieties. It is hard and
brittle and, therefore, cannot be forged or welded
into shape, but must be melted and cast in molds.
It has, compared to wrought iron, a low melting point ;
i. e., 1 100^. Cast iron retains its heat better than
other forms of the metal. It becomes, if frequently
heated to redness and cooled suddenly, very brittle, as
is demonstrated by the cracking of stove covers. If
red-hot iron is covered, so that cooling takes place
slowly, it will not become so brittle.

Stoves, furnaces, and radiator pipes are made of
cast iron.

Chemistry of Cleaning 243

Wrottght iron is made by btiming out some of the
carbon, phosphorus, etc., from cast iron; thus it is a
purer form of iron than the latter. It has a higher
melting point than cast iron (1600^), but is not as
hard and, consequently, it can be drawn out into wire,
rolled into sheets, and wrought into various forms.

Steely like wrought iron, is made by extracting most
of the other elements from cast iron, but the process
is carried out in a different way. Since the means of
making steel at a reasonable price have been pro-
vided, steel has taken the place of wrought iron for
many purposes, for though, like the latter, it is, when
heated, quite malleable and can thus be forged into
shape, rolled into sheets, etc., it can be also cast in
molds and it is much harder and stronger than
wrought iron. Another exceedingly valuable prop-
erty of steel is that it can be easily tempered; i, e,,
made harder or softer as required. For example, if
steel is heated to about 170^ C. and cooled suddenly,
as by plunging it into very cold water, it becomes
exceedingly hard, but, if it is heated to about 235^ C.
and cooled slowly, it will be so pliable that watch-
springs and fine wires can be made from it. The
difference in temper is largely caused by differences
produced in the nature of internal combination of the
carbon by the different temperatures and method of
cooling. In the softer steel, the greater part of the
carbon is present in the form of graphite; in the harder
steel, the carbon is in the form of a carbide.

Galvanized iron is the name given to iron covered
with zinc. It was so named after Galvani, the dis-
coverer of the electric current, because, formerly, the
zinc coating was obtained by means of electrolysis.
At the present time, however, the more common

244 Physics and Chemistry

method is to dip the iron into molten zinc and then
pass it between rollers. As seen in Experiment 28,
when acids and zinc come in contact, the zinc is dis-
solved and poisonous zinc salts are formed; therefore,
galvanized iron cannot be used for culinary utensils,
but as zinc seems to prevent iron rusting better than
the majority of substances used for the purpose,
galvanized iron is in great demand for out-of-door
use.

The enamel ware utensils in such common use for
culinary utensils are made of iron covered with some
form of glaze. The glaze is usually obtained by dip-
ping the iron utensil into a molten solution of fusi-
ble silicate (see page 253) and drying and hardening
it in a furnace.

Enamel is not affected by acids nor weak alkaline
solutions; it is light in weight and easily cleaned.
These qualities all enhance its value for culinary
uses, but sudden cooling after heating, over-heating,
as by leaving the utensil over the flame when it does
not contain anything that will conduct the heat away,
blows, scraping to remove matter that has dried upon
the utensil, cleaning with strong alkalies, all tend to
crack the enamel glaze and when this happens, the
exposed iron rusts more easily than that which has
not been so protected.

The characteristics of iron that allow of its being
used for the various household purposes to which it
is put are: (i) its infusibility (i. e., it can be melted
only at extremely high temperatures); (2) its light
weight as compared with the majority of metals;
(3) the readiness with which it radiates heat. Two
characteristics of iron that are defects as far as such
purposes are concerned are the manner in which it

Chemistry of Cleaning 245

reacts with adds and the ease with which it unites
with oxygen and thus becomes rusty. Because of the
chemical action that occurs when adds and iron come
in contact, foods that contain adds should not be
cooked in iron utensils unless they are protected with
enamel or other substance that is not affected by
adds, and only in such case should adds be used for
cleaning ironware. To prevent iron rusting, it is
necessary to keep it dry and clean. Highly polished
steel or a well-blackened stove will not rust nearly as
quickly as soiled or dull metal.

Kerosene is one of the best substances to use to
remove rust from iron. Stove blacking, the prindpal
constituent of which is graphite, a form of carbon, is
used for polishing stoves, stove-pipes, and the like.
As steel is ver> hard, such substances as emery, car-
borundum, and bath brick can be used for deaning
and polishing it. AlkaHne solutions can be used for
scouring galvanized iron, but only dilute ones should
be used for enamel ware. Lemon juice, vinegar, and
dilute oxalic add can be used for removing stains
from enamd ware, but not from galvanized iron. A
thin paste of whiting and kerosene is excellent for
cleaning zinc and, consequently, galvanized iron.

To prevent utensils, instruments, etc., made of any
variety of iron rusting where they are stored, they am
covered with some substance — as oil or vaseline—
that will protect them from the air and, if they are
not to be used for some time, they are wrapped in
soft paper or other covering that will prevent the oil
bdng removed or dust collecting upon it.

Nickel is a somewhat rare metal element that is
used prindpally as an alloy with, or as a covering for,
other metals. It can be deposited upon the surface

246 Physics and Chemistry

of metals by electrolysis. It is often used in this way
with iron, for it will take a high polish and it will pro-
tect the iron from rust, for the tarnish that forms upon
nickel, even at high temperatures, is very superficial.
A paste made of whiting and either dilute ammonia,
alcohol, or kerosene is suitable for cleaning. Very
badly stained nickel can be cleaned by washing with:
(i) a solution of one part sulphuric acid and 50 parts
alcohol; (2) with alcohol.

Pure tini known as block tin, is a soft white metal
element with a silver-like appearance. It melts at a
temperature of 228** G. It does not form oxids readily
and is therefore often used to cover iron and other
metals which do. The tin generally used for utensils,
roofing, and similar purposes is known as tin plate and
consists of iron covered with tin, the tin coating being
applied by the same methods as is zinc in the manu-
factiu-e of galvanized iron. The low melting point
of tin is its objectionable quality for cooking purposes.
If an empty tin utensil or one lined with tin is left
over the flame even for a few minutes, the tin will be
melted.

As seen by Experiment 28, pure tin is not acted upon
by weak adds or alkalies, but it is by strong solutions;
thus it can be used for cooking fruit and the like and
it can be washed with weak sodium carbonate solu-
tion; but only weak solutions of either acids or alka-
lies should be used for cleaning it. Tin containing
impurities is sometimes acted upon by acids and
poisonous salts formed by the reaction. A soft paste
of whiting and kerosene, plus rubbing, will both
clean and polish tin.

Copper is a strong, heavy metal, but, when highly
heated, it becomes soft and malleable. It melts at

Chemistry of Cleaning 247

1084^. Next to silver, it is the best known conductor
of electricity; therefore, as it is cheaper than silver,
it is much used for electrical purposes. Copper is one
of the best heat conductors and it does not radiate
heat readily, but retains it much better than the
majority of metals. These qualities make it a very
good material for cooking utensils such as pots and
saucepans, especially for the cooking of large qtianti-
ties of food andwhen the utensils are subjected to hard
usage, for copper is practically indestrucible. Unfor-
tunately, it is heavy and hard to keep dean, and
though, as shown in Experiment 28, bright copper is
not acted upon by adds or alkalies, copper oxid and
copper carbonate, popularly known as verdigris^ are
soluble in adds and they interact with adds to produce
poisonous salts. For this reason, copper cooking
utensils, unless kept very dean, are dangerous to use.
To obviate this danger, copper utensils are often
lined with tin, but, as already stated, tin is likely to
be mdted or removed by other means and the exposed
copper tarnishes very readily and is exceedingly diffi-
cult to keep clean. Copper utensils can, however,
be retinned.

Copper is extensively used for making alloys, i.V.,
combinations of metals. Some of the more important
of these are: Brass, which consists of copper and zinc;
bronze, which is copper, tin, and zinc; German silver,
which is copper, zinc, and nickd; gun metal, which is
copper and tin.

The outer surfaces of copper appliances are some-
times covered with lacquer, consisting, usually, of
shellac, and sometimes a coloring substance dissolved
in alcohol. Lacquer is spotted by water, and there-
fore a lacquered surface should not be washed, but

248 Physics and Chemistry

sfaould be ktgt dean by nbbiiig witii a soft, dean^
dry doth.

Both adds and alkalies can be used for deamng
copper and solutions of both oxalic add and ammonia
dther alone or in combination with sudi substances
as whiting, silicon* and kerosene are much used; as
are also putty powder, rottenstone, and various
patented preparations. A hot solution of sodium
chlorid in vinegar (i part of salt to 16 of vinegar) is
very effectual in removing stains from both copper
and brass.

Alnmininm is a tin-white metal of very light wdght.
On account of this latter quality and its nice appear-
ance, aluminium is much used for cooking utensils.
It has, however some disadvantages for cooking pur-
poses, viz., it radiates heat so rapidly that food cooked
in it takes longer to become hot than when cooked in
utensils made of other metals, and it will not remain
hot in aluminium utensils for any length of time after
the latter are removed from the fire. Also aluminium
is injured by both organic and inorganic adds, by
alkalies and by salt solutions; therefore ndther fruit
nor other add food nor salty food should be cooked
in aluminium utensils, nor should milk be kept in
them, in case it should sour.

Altuninium is best cleaned with neutral soap and
water. A paste made of whiting and very dilute
ammonia can be used when necessary. Two patented
preparations, the Universal Metal Polisher and Putz
Pomade, have been found very effective in removing
from operating-room utensils stains made with bi-
chlorid and iodin and have not injured the metal.
As aluminium is so easily injured by the common
constituents of metal-deaning preparations, caution

Chemistry of Cleaning 249

must be observed in using those the effect of which
is unknown.

Silver is a heavy» rather soft» white metal, that can
be highly polished. It is not affected by organic
acids and does not oxidize at ordinary temperatures,
but the presence of even very minute traces of sulphur,
such as are usually present in the air, especially in the
vicinity of places where gas is burned, will cause the
silver to tarnish, for the sulphur will unite with it and
form a thin film of silver sulphid (AgaS) over the
surface. It is because of the sulphtir they contain
that eggs discolor silver spoons and, for the same
reason, woolen fabrics and material for the bleaching
or dying of which sulphur has been used may cause
a similar discoloration. It is therefore well, when
storing silver articles, to coat them with vaseline and
wrap them in soft tmbleached muslin or in tissue paper.

Whiting, rouge, and silicon are all much used for
removing tarnish from, and for polishing, silver.
An effective substitute consists in boiling the articles
to be cleaned in a solution of sodium chlorid and bi-
carbonate of soda (one tablespoon of each of these
salts to a quart of water) in a patented apparatus
known as a sUver-^lean pan. The salts are decom-
posed and the soda tmites with the sulphur forming a
salt that is soluble in the water. After the silver has
been boiled for three minutes, it is removed from the
solution, rinsed in water, and dried with a clean, soft
doth. In hotels and other places where a large num-
ber of articles must be cleaned daily, the polishing is
done by a polishing machine run by electricity, and
sometimes especially large articles are cleaned by
dipping them in hydrocyanic acid. The add unites
with the sulphur of the tarnish forming a salt that is

250 Physics and Chemistry

soluble in the add. This is a very quick and effective
method, but it must be carried out with caution and
the fingers must not come in contact with the add for
it is exceedingly poisonous.

Lead is a heavy, lustrous metal that owes much of
its usefulness to its softness and to the ease with
which it is melted. It tarnishes readily and is acted
upon by the majority of acids, except hydrochloric
and sulphuric, forming salts that are injurious to
health for, though pure lead is not poisonous, many
of its salts and other compounds are. A common
form of slow lead poisoning is that which painters
often contract. The usual cause of this is taking
their food in their hands while they are soiled with
paint containing lead compounds.

The majority of lead compounds are insoluble in
pure water, but soluble in water containing carbon-
ates and sulphates. Therefore, water containing
such salts, after standing in lead pipes, may contain
injurious lead compounds, but the danger, it is thought,
has been overestimated, since, if such salts are present
in water, they soon form a coating over the interior
of the pipes. However, as lead pipes are much used
in houses, it is a wise precaution, when the plumbing
is new and when water has not been drawn for some
time, as, for instance, when, a house has not been
lived in for several weeks, to let water that is to be
used for drinking or cooking flow for some minutes
before use, so as to empty the pipes of that which has
stood in them.

An aUoy of lead and tin, known as solder^ that is
easily melted, is much used for cementing severed
metal surfaces together.

Pewter is an alloy of tin and lead and therefore

Chemistry of Cleaning 251

acid food should not be put into pewter utensils nor
should they be cleaned with add-containing substances.
Platinum is a grayish-white metal of high luster.
It is a good conductor of electricity. It is very mal-
leable and ductile, but fusible only at extremely high
temperatures. It is very inert (*. e., it does not
combine readily with other elements) and there-
fore it does not tarnish and is not attacked by many
adds nor alkaline substances. These qualities make
platinum of great value for utensils tised in elec-
tricaly chemical, and bacteriological work. Platinum
is acted upon by nitric add and by chlorin.

Marble

Experiment 29. Object, to study the eflEect of
adds and alkalies on marble.

Material required: Powdered marble or caldum
carbonate (CaC03), hydrochloric add, lemon juice,
ammonia water, sodium carbonate solution 10 per
cent., 6 test tubes.

Procedure: Put a little caldum carbonate into
each of the six test tubes and add to (i), hydrochloric
add ; to (2), lemon juice, to (3) ammonia, to (4) sodiimi
carbonate solution; to (5), water. Let the five test
tubes stand. Watch results. To tube (6) add some
hydrochloric add and, when action is well established,
some ammonia water.

It will be seen as the result of this experiment that
marble is insoluble in water and alkaline solutions,
but that it interacts with, and is dissolved by, adds,
espedally n:iineral adds. Also that an alkali, by
neutralizing the add, stops the reaction. Since add
has this effect upon marble, if lemon juice, or other

2S2 Iliysics and Chemistiy

add, is spilled npon it, the suiface of the latter will
be Toug^iened unless the action of acid is at once
neutralized by the addition of ammoraa or other
alkaline substance. Marble is best cleaned with hot
soapsuds or alkaline solutions. Many stains can be
removed by rubbing tiiem with NaQ or kerosene.

Marble was formerly much used in kitchens and
lavatories, but the ease with which it was affected by
acids led to the exclusion of its use for many purposes
as soon as the means of maldng suitable porcelains
and cements were discovered. There are now a num-
ber of cements and cement-like substances used as
tiling, and in other form, for floors, table covers, sinks,
etc., that are not affected by either adds, alkalies, or
heat and that do not absorb grease — most important
qualities to be considered in judging the value of such
material for kitchen use. Tiling tinted gray, buff, or
other dull hue is much better than white for floors
and table tops, because (i) white shows every mark
and (2), if the kitchen is as light as it should be, white
causes a glare that is very trying for the eyes.

Glass

Compomtion. — Glass consists of mixtures of differ-
ent bases and various silicates (i. e,, salts of silidc
add, an add that is obtained from silicon, a form of
sand).

Crown glass, which is used for windows, consists
of silicates of soda and lime; plate glass, also used for
windows and for mirrors, consists of silicates of soda,
lime» and potassium; fUnt glass, which, as it has a high
refractive power, is much used for optical purposes,
consists of potash and lead silicates; Bohemian glass

Chemistry of Cleaning 253

which, being very infusible, is much used for chemical
purposes, is a silicate of potash and lime; the cheaper
glasses, such as are used for bottles, consist of the
same ingredients as Bohemian glass, but they contain
impurities.

Glass is made by fusing silica — ^in the form of sand
or quartz — ^with the desired bases, at an exceedingly
high temperatiure, for a nimiber of hours. The molten
mass, when clear, is made into the desired shape,
usually by blowing or pouring it into molds. It is
then cooled rapidly, in order that it may retain its
transparency, and afterward it is annealed, as this
renders it less brittle. Annealing consists in heating
the glass to a temperature just below its melting
point and then allowing it to cool slowly.

Opaque glass is made by adding some finely divided
infusible matter to the molten glass before it is shaped.
Colored glass is made by the addition of coloring
matter — usually a mineral oxid — to the molten glass;
«. g., a blue color is obtained by the use of an oxid of
cobalt; a red color by the use of copper or gold oxid.

Porcelain and Chinaware

Porcelain and chinaware consist of different silicates
of aluminiiun. These occur in certain clays. For
the finer porcelains, all impurities are removed. In
the making of dishes, etc., the clay is moistened with
water, molded into shape on a wheel, and heated in
a furnace to a strong red heat. Large portions of the
silicates in the clay used are infusible, but some are
fusible, and these, while the articles are in the ftimace,
melt, and this molten naatter, spreading through the:
mass, cements the infusible substances together.

254 Physics and Chemistry

When the articles are removed from the furnace,
they are porous, and in order to render them imper-
vious to liquids, they must be glazed. This is done
by dipping them in a mixture of molten, fusible sili-
cates and returning them to the furnace that the glaze
may harden. The glaze is practically the same as
glass.

Cleaning of glass and porcelain. — If hot alkaline
solutions are used on glass and porcelain, some of the
alkali combines with the silicates, and repeated treat-
ment of this kind will diminish the luster of the glass
or glaze; therefore, only neutral soaps or soap powders
should be used for washing good glass and porcelain
ware. This is true also of glazed or enamded sinks
and utensils. Kerosene, benzene, and whiting can
be used, and are usually very effectual for removing
stains that soap will not eradicate. Glass and glaze
are rather easily scratched, so that nothing rougher
than whiting should be used. For cleaning windows,
mirrors, and the like, a thin paste of whiting and
water with, sometimes, a little soap is rubbed over
the stuf ace of the glass ; the water is allowed to evapo-
rate, and, afterwards, the dried whiting is rubbed off
with a soft, clean, lintless doth.

and Varnishes

These substances serve two purposes: (i) they,
except water paints, protect the surfaces they cover
from the influence of air, moisture, etc. ; (2) they are
used for decoration.

Nature of paints. — Paints are classed as water and
oil paints and the water paints used in masonry are
x^fassed as whitewashes and kalsomines«

Chemistry of Cleaning 255

Whitewashes are usually either mixtures of water
and lime, boiled soap and lime, or skimmed milk and
lime, and, if colored, coloring matter. When a white-
wash is spread upon a surface it loses water by evapo-
ration and absorbs CO a* thereby becoming changed
to chalk (CaCOj).

Kalsomine consists of a finely ground chalk and
coloring matter suspended in a warm solution of glue.
It is applied while hot, and as it cools, it loses water
by evaporation and becomes dry and hard.

Since both whitewashes and kalsomines become dry
by the loss of water, they will be dissolved by the
addition of water. They cannot therefore be used on
the exterior of buildings nor can surfaces covered with
them be washed. Water paints, however, are cheaper
than oil paints and are therefore often used for color-
ing walls of new houses tor, as the plaster is apt to
crack dining the first months following structure,
due to shrinking of the wooden rafters, etc., the walls
generally need to be repainted or papered in a year
or two.

Oil paints consist of coloring matter (which usually
is composed of ground minerals), carbonate of lead
(known also as white lead) , or zinc white, or both held
in suspension in what is called a drying oU — ^linseed or
poppy oils being the ones most commonly used. *

The carbonate of lead and zinc white are bases
and, when mixed with oil, they form a soap which,
as sufficient oil is used for the purpose, is held in
solution in the latter.

The oils used are called drying oils because, espe-
dally when spread out in a thin film, they unite with
oxygen and, when oxidized, become dry and hard.

Substances that will hasten the absorption of

256 Physics and Chemistry

oxygen — as compounds of manganese — are often
added to paints to hasten the oxidation and, conse-
quently, the drying. When used for this purpose,
such substances are called driers. Sometimes, instead
of using driers which act in this manner, matter that
will readily part with its oxygen — as lead oxid — ^is
used. Spirits of turpentine, called turps by painters,
is sometimes added to paint to thin it or, especially
in the first coat of paint applied to wood or plaster,
to hasten the absorption by the surface upon which
it is spread.

Methods of cleaning painted suifaces. — ^As water
paints are soluble in all liquids, including water, sur-
faces covered with them cannot be washed, therefore
dusting with a soft, dry cloth is the best means of
cleaning them. Oil paints are insoluble in water, and
surfaces covered with them can therefore be washed
with warm water and neutral soap, or, with white
paint, bonami can be used. (N. B. — ^Bonami and whit-
ing should not be used on colored paints.) Alkalies
unite with some coloring substances and thus cheap
scouring soaps and other alkaline detergents should
not be used. Neither should coarse, hard, cleansing
agents be employed, for paint is easily scratched.

Nature of varnishes. — ^Varnishes are usually classed
as spirit varnishes and oil varnishes.

spirit varnishes consist of gum resin, such as shellac,
dissolved in alcohol; oil varnishes of fossil resin, such
as amber, dissolved in hot linseed oil. When either
form of varnish is spread over a surface, the solvent
— ^the alcohol or oil — evaporates and the resin solidifies.

Shellac is rather soft and is spotted by water, there-
fore spirit varnishes are not suitable for surfaces
exposed to weather or to rough usage.

Chemistry of Cleaning 257

Cleaning varnished snifaces. — Good oil varnish
can be wiped with a soft, damp cloth, but the surface
must be wiped dry, and water should not be allowed
to get into seams of the woodwork. If the varnish is
inferior, however, the use of a damp cloth will soon
cause yellow or white spots to appear. A weak solu-
tion of good Castile or other neutral soap can be used
to remove grease stains if the soap is washed off with
a cloth dampened in clean warm — never hot — ^water.
After such treatment, a varnished surface should be
rubbed with a soft doth moistened with a reliable
varnish polish. Too much polish must not be used
and the surface to which it is applied must be well
rubbed, for such polishes nearly all contain some oily
constituents and, if the surface is left wet, dust may
collect and be difficult to remove.

Both paint and varnish are to some extent soluble
in alcohol, therefore if the latter is spilled on furni-
ture it will cause spotting, unless its action is neu-
tralized by pouring oil over it. This should be done
before wiping off the alcohol. White spots on furni-
ture, due to exposure to heat, may be removed by
rubbing them with spirits of camphor, or equal parts
of linseed oil and alcohol.

Wax

Waxing is a very common way of treating floors.
Before wax is applied to a new floor, the latter should
be given two coats of a mixture of equal parts of pure
linseed oil and ttupentine with sufficient japan to
make the mixture harden overnight. This brings
out the grain of the wood and prevents subsequent
grease spots showing. The floor waxes commonly

258 Physics and Chemistry

sold are mixtures of beeswax, paraffin, and turpentine.
Before applying the wax, it is, if necessary, thinned
to the consistency of a paste with turpentine. It is
most important not to put the wax on in a thick layer,
for when this is done the wax takes a long time to
dry thoroughly and it collects dust. After the wax
is applied, it is left for about twelve hours to harden,
and then a little more paste is rubbed over the floor
with a soft doth. The turpentine in the paste dis-
solves any surplus wax that may be on the floor and
makes the coating more uniform. When the wax is
perfectly dry, the floor is polished with a weighted
brush and the rubbing should be done with the grain
of the wood.

For floors likely to be spotted with water, it has
been recommended that they be saturated with paraffin
by covering the floor with powdered paraffin, such as
is scattered over the floor when preparing for danc-
ing, and melting the paraffin with hot irons or to have
the floor waxed in the usual manner and sprinkle
powdered paraffin over it, and then, as in the ball-
room, allow the feet of those passing over it to force
the paraffin into the wood. This treatment gives the
floor a hard, impervious surface, which will not be
easily spotted with water.

Cleaning waxed floors. — ^After a floor is properly
waxed, the only treatment that it usually requires for
some time is an occasional polish with a weighted
brush. When the surface grows dull another thin
application of wax can be made in the same manner
as the previous one. If water is spilled, after it is
dried, the subsequent spots can be removed by rub-
bing them with wax and then with a warmed woolen
doth and a weighted brush. Oil should never be put

Chemistry of Cleaning 259

on a waxed floor as it causes the wax to become dark
and spotted. Ink stains can be usually removed by
putting a little solution of oxalic add over the spots
and allowing it to remain tmtil it dries ; the oxalic acid
unites with the iron in the ink to form an oxalate of
iron, which can be easily washed off. The subse-
quent white spots can be obliterated by rubbing a
little wax into them. There are some inks which are
made from the aniline colors and do not contain iron,
and to remove these and, also, grease spots, sodium
carbonate can be used (except on oak floors, which
are stained brown by alkalies). White spots caused
by the soda must be treated as those due to other
causes.

CHAPTER XVII

TEXTILES

Classification and Origin of Textiles — ^Bffect of Detei^gents 6a
Different Kinds of Textiles — Methods of Removing Stains—
Textile Tests — Printing and Dyeing — Nature of Dyes —
Fading of Colors.

The variotis kinds of materials used for clothing,
upholstery, and the like are classed as textiles.

Source of textiles. — Textiles are made by spinning,
weaving, and otherwise treating fibers which are ob-
tained from animals, plants, and, in a few cases,
inorganic matter.

From fibers of animal origin are made wool, hair,
and silk; the principal vegetable fibers are cotton,
flax, jute, and hemp; the chief mineral fibers are
asbestos, and the spun glass, silver, and other minerals
classed as Unsds,

Vegetable fibers consist mainly of cellulose. The
cotton fibers from which cotton materials are made
are procured from the cotton plant. Flax fibers,
obtained from the plant of the same name, are, when
woven, known as linen.

The quality and nature of woolen materials depend
both upon their source and the processes to which
they are subjected in the course of manufacture. The
wool of different animals varies greatly in strength,

260

Textiles 261

length, fineness, and softness and so does that of similar
species of animals that are reared under di£Eerent
conditions and in different climates. Also, the quality
of wool taken from different parts of an animal varies
very considerably.

The chief difference between wool and hair is the
greater fineness of the fiber of the former and its
highly serrated surface.

The fibers from which silk material is spun are pro-
duced by silk worms, from liquid which they secrete,
in much the same way as spiders spin their webs.

Both silk and wool contain protein substances; this
can be proved by Experiment 30.

Experiment 30. Procedure: Dip some pieces of
white (i) all wool material, (2) mixed wool apd cotton
material, (3) silk, (4) linen, (5) cotton,into some Millon
reagent (see page 284), and then allow them to dry.
The wool and silk will assume the red color which
always indicates the presence of protein (see page 284).
In the mixed wool and cotton material the cotton
threads can be easily discerned, for they remain un-
colored. This is one of the tests used to discover if a
material is all wool or a mixture of wool and plant
fibers.

Experiment 31. Object: To see if there is sulphur
present in the different textiles.

Procedure: Btuti a little of each kind of textile in
a flame, notice the difference in the odor from the
wool. Hold pieces of paper moistened with lead acet-
ate solution in the smoke. Hydrogen stdphid (HaS)
reacts with lead acetate to form lead sulphid (PbS)
which is black.

Wool and hair are the only textiles that contain
sulphur as a part of their actual composition, but

262

Physics and Chemistry

stilphur may be present in new materials of other kinds
for the bleaching or dyeing of which sulphur has been
used.

Ravel out threads of each kind of textile and
examine them under the microscope.

The cotton fibers, though orignally tubular, become
flattened dtuing the manufacture of the textile and,
under the microscope, show a characteristic twist
with the ends gradually tapering to a point.

Linen fibers,
it will be seen,
resemble cotton,
but they are
straighter and
more tubular
and they have
slight serrated
notches or joints
along their walls
which serve to
hold the fibers together. These teeth in the notches
are not so long as those in the wool fiber and thus,
though linen shrinks, it does not do so to such an
extent as wool.

The wool fibers, it will be noticed, are marked by
transverse serrated divisions. When woolen material
is rubbed, or subjected to hot water or strong alkalies,
these teeth-like processes become curled, knotted, or
tangled together, and this causes shrinking of the
material. If cotton fibers are mixed with the wool
in a textile, there will be less shrinking.

Silk fibers are perfectly smooth and when rubbed
they slide over each other. This sometimes causes
a slight shrinking in the width of silk textiles.

Fig. 6o. (a) Cotton fiber, (b) Wool
fiber, (c) Linen fiber. As they appear
when viewed through the microscope.

Textiles 263

Mercerized textiles. — Mercerized materials were
so called after a man named Mercer, who introduced
the process. This consists in treating the fabrics with
caustic soda or sulphuric add; the former being used
for cottons and the latter for wools. This makes the
fibers heavier and flatter and gives them a silky ap-
pearance and feel.

Artificial silks. — Various kinds of artificial silks are
made from cellulose by different processes. They
lack the tensile strength and elasticity of silk and thus
do not wear as well.

Asbestos is a silicate of magnesium and lime. It
can be sptm into a fine thread and then woven into
doth. It is incombustible.

Experiment 32 . Object : To test the action of adds,
alkalies, and chlorid of lime on different textiles.

Procedure: Put small pieces of the different textiles
into separate beakers containing: (i) concentrated
oxalic add; (2) oxalic add 1%; (3) concentrated
hydrochloric add; (4) hydrochloric add 5%; (5) hot
sodium hydroxid solution 10%; (6) cold soditmi hy-
droxid solution 10% ; (7) hot sodium carbonate solution
10%; (8) cold sodiiun carbonate solution 10%; (9)
a hot saturated solution of borax; (10) a dilute solu-
tion of borax; (11) a hot dilute solution of ammonia;
(12) a hot satturated solution of chlorid of lime; (13)
a dilute solution (10%) of chlorid of lime; (14) dry
chlorid of lime. Use colored pieces of material for
the lime tests.

Let the pieces of material remain in the solutions or,
in 14, covered with the lime for half an hour, then
remove them and cut each piece in half (be careful
not to get those from the different solutions mixed) ;
rinse one set of pieces thoroughly in hot water and

264* Physics and Chemistry

place them, and also those which were not rinsed,
where they will dry. Note and record any changes
that have occurred in the fabrics; ptdl the pieces of
material and see if their fibers have been weakened.

State which of the detergents can be used for each
kind of material and in what strength.

Why was the color not a£Eected by the dry lime?

Cotton is not much affected by alkaline solutions,
if the material is well rinsed, otherwise the alkali
becomes concentrated as the water evaporates during
drying and, as it acts for some time, it weakens the
fibers of the material.

Cold dilute add solutions do not injure cotton, if
the material is well rinsed; strong solutions either cold
or hot do, hot ones being more injurious than cold.

The action of detergents and Reaches on linen is
about the same as on cotton, but linen is more easily
affected by alkalies.

With the exception of nitric acid, dilute add solu-
tions do not injure wool. Why does nitric add affect
it? (See protein test, page 284.) A warm solution
of sodium or potassitun hydroxid will dissolve wool ;
the carbonates of these alkalies have not such an
injurious effect, but they make it hard and harsh.
Even weak solutions of chlorid bleaches injure wool.

Experiment 33. Object: To test the effect of dry
heat on wool. Pass a hot iron over a small piece of
woolen material several times and note the result.
Cover a similar piece of material with a piece of damp
muslin, and pass the iron over it. Compare this
piece with the other and with a piece that has not
been pressed.

The protein matter of wool contains considerable
water which heat causes to evaporate, thereby caus-

Textiles 265

ing loss of luster and strength of the wool fibers.
Why was the piece of material covered with the damp
cloth not affected in the same way as that pressed
without it?

Silk is affected by the same substances as wool and
in the same way except that it is not injured by moder-
ately high degrees of heat and it is injured by adds.

Some Ptactical Appiicati<m8 of Knowledge of Effect
of AddSi Alkaliesi etc., on Textiles

As the result of the foregoing experiments, it can
be seen that weak soda solutions (the strength depend-
ing upon the hardness of the water, see page 220) can
be ttsed in washing cotton and linen materials, if the
fabric is well rinsed, this care being especially impor-
tant in the care of linen. Only weak borax solutions
and neutral soaps should be used for woolen and silk
materials. The reasons why the addition of an alkali
to water used for laundry purposes is advisable were
discussed in connection with hard water.

Though it is better not to use bleaching agents in
the laundry, weak solutions of such bleaches as chlorid
of lime and Javelle water can be used for bleaching
cotton and linen, if the precautions mentioned on page
216 are taken, but neither of these substances should be
used for wool or silk, or any kind of colored material.

Woolen and silk materials should not be rubbed
hard. Woolen material must not be exposed to a
high temperature, therefore, it should be washed in
warm, not hot, water and dried at a low temperature;
it should not be dried in the driers. When pressing
woolen goods, a damp doth should be put between
the material and the iron.

266 Physics and Chemistry

Bluing

Bluing is used instead of, or in addition to, bleach-
ing, to renew the white color of fabrics that have ac-
quired a yellowish hue. That it will do this is due
to the fact that blue and yellow are complementary
colors and when combined in proper proportions are
seen as white.

The blues in most common use are: (i) Ultranmrine,
a prepared compound of the elements aluminium,
soditun, silicon, sulphur, and oxygen; (2) various coal-
tar products as indigo, indigo-carmine, and the alkali
blues; (3) Prussian blue, acompotmdof iron, carbon,
and nitrogen. Prussian blue is considerably cheaper
than the others, but it is decomposed by soaps and
alkalies and if any of these substances are left in the
clothing, or when the goods are next washed, the blue
will be decomposed and ferric hydroxid [Fe(0H)3]
produced. This will cause yellow stains in the
fabric.

Experiment 34. Object: To discover if iron is
present in blue.

Procedture: Make a strong solution, — about a
teaspoonf ul of liquid Prussian blue to a cup of water,
— ^have two strips of white muslin cut from the same
piece of material, dip one strip in the bltxing water,
then dry it by pressing it with a hot iron. Compare
the muslin thus treated with the other strip. If there
was iron in the blue the blued strip will have yellow
stains. To prove that this staining is due to ferric
hydroxid, use a test for iron. A conmion test is: to
pour a drop of (i) pure hydrochloric acid, (2) yellow
prussiate of potash over the stain. If this has been
caused by iron, a blue color will develop.

Textiles 267

The Removal of Stains from Textiles

Some important things to remember in connec-
tion with the removal of stains from woven fabrics
are:

(i) If the staining agent is allowed to become dry,
it soaks into, and hardens in, the fibers, and it is then
more diffictilt to remove.

(2) Unless the staining agent is soluble in hot water,
it will, probably, if put into hot water, be hardened
by the heat.

(3) When strong adds or alkalies are used to
remove stains, they must be neutralized and the
material thoroughly rinsed, or it will be destroyed.

(4) When the detergent used acts by dissolving
the staining matter (as when ether is used to dissolve
fat stains), some absorbent material, as a loose pad of
soft muslin, should be placed under the stained ma*
terial so that the matter will be absorbed as quickly
as it is dissolved, otherwise, it will spread and leave
a mark.

(5) When removing stains from colored materialt
always try the reagent on a seam or other part that
will not show ; for, as can be easily appreciated from
what is said in the section on dyes, colors are affected
in different ways by the various reagents.

(6) Exposure to the sun's rays hastens such chemi-
cal reactions as that which occurs when salt and lemon
juice are used to remove a stain.

(7) The sun is a powerful bleaching agent, conse-
quently the whiteness of white fabrics will be increased
by exposure to its rays, and the tint of colored ma-
terial may be injtired ; the reason for this was given
in Chapter VI.

268 Physics and Chemistry

Methods of Removing Stains

Balsam of Peru stains. — Soak and wash the stained
part in alcohol.

Bichlorid stains. — Soak the stained part in a 34 per
cent, solution of Javelle water for twelve hours. Then
soak and wash it thoroughly in hot water.

Blood stains. — If blood cannot be washed out with
soap and tepid water, soak the stain in peroxid of
hydrogen, or wash it in ammonia water.

Coffee and chocolate stains. — These can be usually
removed by washing them with hot water; if not,
place the stain over a bowl containing boiling water,
sprinkle the stain with borax, and wash it with hot
water.

Fruit stains. — These can be often removed in the
same way as coffee; if this fails, use either of the
following methods: (i) Rub the stain with a concen-
trated solution of oxalic acid; then neutralize the
acid with ammonia and wash as much of the material
as was wet with the reagents in hot water. (2) Im-
merse the stained part of the fabric in equal parts of
boiling and Javelle water and, after a few minutes,
wash it thoroughly in boiling water. Javelle water
must not be used for silk or wool or colored material.

Glue stains. — Apply vinegar to the spot with a
piece of soft muslin until the stain is removed.

Grass stains. — ^Wash the stained part of the mate-
rial in either f els naphtha soap or anmaonia and water,
ether, or alcohol. If no one of these is effectual,
spread a paste made of f els naphtha soap and bicar-
bonate of soda over the stain and allow it to remain
for several hotu^, and then wash it off with hot water.

Grease stains. — ^Wash the stained part with either

Textiles 269

vinegar, hot water a;cid soap, hot soda water, hot al-
cohol, ether, benzene, carbona, or gasolene. Remem-
ber the precautions given in section 6, page 267.

Ink stains. — Stylographic and red inks can be gene-
rally removed by washing with soap and tepid water,
especially if the washing is done while the ink is still
wet. Stains made with other inks can be usually
removed with lemon juice, salt and water, or with
oxalic add. To use lemon juice, soak the stained
part in warm water until it is thoroughly moistened,
then rub and cover the stain with salt and lemon juice
and place the fabric where the stm will shine upon the
stained portion. Make fresh applications of water,
lemon juice, and salt when required. It may be
necessary to continue the treatment for two or three
hours, then wash the part with (i) ammonia, (2) hot
water. Use oxalic acid as directed under fruit stains.

lodin stains. — Soak the stain in either ammonia,
ether, or chloroform.

Iron rust. — Use either lemon juice, salt and water,
or oxalic acid as directed for ink stains.

Kerosene. — Soak the stain in hot water. and then
cover it with a thick layer of moistened fuller's earth.
Let this remain for several hours and then wash it oflE
with hot water.

Meat-juice stains. — Wash the stain with either
peroxid or hydrogen or else with (i) cold water, (2)
warm water and soapsuds.

Medicines. — Either alcohol, ether, or ammonia
will usually remove stains made with drugs. For
drugs containing iron use the same reagents as for
iron rust.

Mildew. — Exposure to sunlight followed by hard
brushing will sometimes remove mildew. If this

270 Physics and Chemistry

fails, soak, the stained part in lemon jtiice until it is
thoroughly saturated and then place it in the sun-
light. If this is not effectual, cover the stain with a
paste made of one tablespoonful of powdered starch,
one teaspoonful of salt, and the juice of one lemon.
Allow this to remain for twenty-four hours. Repeat
the application if necessary. Mildew is a species of
mold.

I Paint. — Rub the stain with benzene, turpentine,
chloroform, or naphtha. The two last named are best
for delicate colors. Remember the precaution men-
tioned in sections 4 and 5, page 267.

Perspiration. — ^Wash the discolored part of the
material with soapsuds and, while still covered with
the suds, place the garment in the sunlight.

Scorch. — Moisten the scorched material and hang
it in the sunlight.

Tea. — See coffee.

Varnish. — Make repeated applications of alcohol,
turpentine, chloroform, or vinegar. Chloroform can
be used with the majority of colors except blue; use
vinegar for blue.

. TeztUe Tests

Experiment 35. Object : To distinguish cotton from
linen. Stain a small piece of the material to be
tested with fuchine and then dip it into ammonia.
Linen fibers will remain red, but cotton ones will part
with the dye when wet with the ammonia.

Experiment 36. Object : To distinguish cotton and
linen fibers from wool.

Procedure: Boil a small piece of the material to
be tested in a 5% solution of sodium hj^droxid. Dip

Textiles 271

another piece Into a 5% sulphuric add solution and
put the pieces where they will dry quickly. The cot-
ton fibers are not affected by the alkali and the wool
fibers are. The wool fibers are not affected by the
add and the cotton fibers are carbonized.

The Millon test (see Experiment 30) is another
method of distinguishing between animal and plant
fibers.

Experiment 37. Object : To distinguish silk fibers
from wool.

Procedure: Place the fabric in cold concentrated
hydrochloric add. Silk fibers will dissolve; wool will
merdy swell.

Dressing of Cotton and Linen Fabrics

An important thing to consider in dedding the
worth of cotton and linen materials is the amount of
dressing substances that they contain.

By dressing is meant such substances as starch,
gum, dextrin, glycerin, and various mineral derivatives
that are used in order to, in some way, improve the
appearance of the material. When the dressing is
applied to the warp, it is usually called sizing; when
it is applied to the woven material, it is termed
finishing. Some dressing is benefidal to many
textiles, even certain woolen ones, but, when large
amounts are used, it is generally to cover defects in the
material.

Experiment 38. Object : To detennine the amount
of dressing in a fabric.

If material contains a large amount of dressing, it
will lose its stiffness when rubbed between the fingers.
For this test, use some pieces of cotton and linen mate-

272 Physics and Chemistry

rial that will do so and some that are not much changed
by rubbing, in order to compare the results.

Procedure: Weigh the pieces of material and then
boil them in a 3% solution of hydrochloric acid.
Rinse them in water, each one separately, and test
the water for starch with iodin. (See page 289.) If
starch is present, in any of the pieces of material,
boil those in which it is again. When they are all
starch free, dry and weigh them. The difference in
weight will show the amount of dressing that was
present.

Printing, Dyes, and Dyeing

The difference between the dyeing and printing of
fabrics. — By dyeing is meant the saturation of the fiber s
of a textile with a coloring substance; by printing, the
impression of a colored design upon a fabric.

Printed materials can be tisually distinguished
from dyed by examining the wrong side of the
fabric, if the pattern does not show through, it is
printed.

Material naay be dyed either before o^ after it is
woven.

Dyes. — ^A few dyes are prepared from inorganic
matter, notably, khaki, which is made by adding
chrome alum to a solution of iron, but they are nearly
all procured from organic matter. In the olden days,
dyes were made principally from vegetable matter,
and a few, as cochineal, from animal matter, but, at
the present time, coal tar is their usual source. In
fact, it has been estimated, that over fourteen thou-
sand colors are secured directly or indirectly from
coal tar.

Textiles 273

Coal-tar dyes are often spoken of as the aniline
dyes, because the first ones obtained from this source
were made from aniline — a coal-tar derivative — now,
however, a large number are obtained from carbolic
acid, naphthalene, anthracene, and various other
products of coal tar.

Coal-tar dyes vary greatly in their nature, some
having acid and others basic properties as well as
other different characteristics.

Mordants and lakes. — On account of the differences
in the nature of dyes and those of textiles, all fabrics
will not be equally well dyed with the same kind of dye;
e, g., the protein matter in silk and wool will unite
with substances in some dyes that will find nothing
to combine with in the cellulose fibers of textiles of
vegetable origin. In such case what is known as a
mordant is used. By a mordant is meant any sulh
stance that wiU combine with some constituent of the
textile or which can penetrate its fibers and which also
has an affinity for the dyestuff so that it will unite with it
and thus procure live saturation of the fibers with an
insoluble colored substance. This insoluble compound
formed by the use of mordants is called a lake.

Permanence of dyes. — Even with the use of
mordants, aU dyes will not be equally permanent, and
their permanence or fastness will vary in different
materials.

The more common auxiliary causes of change of
color in material are washing, the action of the acids
of perspiration, and exposure to the sun's rays.

The following tests are ones that are frequently
used to test the resistance of dyes to such things.

Experiment 39. Object: To test the color fastness
of materials.

274 Physics and Chemistry

Test for washing fastness. — Soak and rub a small
piece of the material in boiling soap solution. Do this
several times. If the color does not run and if com-
parison with an unwashed piece of material shows
that it has not faded, the color is fast to washing.

Resistance to perspiration. — Soak a piece of the
material to be tested in 30% acetic add that has been
heated to about 99° F. and then dry it, without rins-
ing, between parchment paper. When dry compare
it with a piece of the material that has not been so
treated.

Resistance to light. — Place the pieces of material
to be tested where they will be in the direct sunlight
a considerable portion of the time for a month. Coni-
pare them daily with similar pieces that are not so
exposed. Colors that will stand such exposure for a
month are considered fast; those which have under-
gone appreciable though not very great change, are
said to be fairly fast; those which show considerable
change in two weeks are classed as moderatdy fast^
and those which are much changed, os fleeting.

The comparative permanence of the ftmdamental
colors in different materials {9 about as follows:

Brown lasts well in cotton materials, but is likely
to fade in linen and woolens.

Dark blue is generally a fast color in all the textiles,
but light blue generally fades quickly.

Black lasts well in wool and silk, but not in vege-
table fibers.

Red is fairly permanent in woolen and silk ma-
terials, but only fairly so in others.

Gray is fairly permanent in all materials.

Pink fades soon, but usually does so unifonnly
and becomes a pretty shade.

Textiles 275

Green cannot be depended upon except in high-
priced woolens and silks.

Lavender is likely to be a fleeting color in all
materials.

CHAPTER XVIII

THE CHEMICAL CONSTITUENTS OF THE HUMAN BODY

AND OF FOOD

Classification, Nature, and Uses of the Substances Composing^
Animal Bodies and Plants — Tests for Proteins, Starches,
Sugars, Salts — Origin of Food Material.

In order that the machinery of the human body
(u c, the heart, lungs, muscles, etc.) may be kept at
work, it must be provided with fuel and with matter
containing the same elements as itself which its cells
can utilize for their building and repair. The ele-
ments that the body needs for these purposes are
contained in many compounds that are very com-
mon in nature, but almost the only combinations
that the human body can utilize are those formed
in certain plants and in some of the lower animals.
Though the tissues of plants and of animals are
so unlike in appearance, the compounds of which
they are composed are so similar in their chemical
composition that they, including those constituting
the human body, are classified tmder the same
headings.

Classification of the substances composiiig plants
and animals. — The various substances that enter into
the composition of both plants and animals are dassi-

376

Chemical Constituents of Food 277

fied as organic and inorganic. The organic compounds,
are further classified as nitrogenous (those containing
nitrogen) and non^niirogenous (those without nitro-
gen). The majority of nitrogenous substances are
known as proteins and the non-nitrogenous organic
substances are classed as carbohydrates and fats. The
inorganic constituents of plant and animal tissues are
salts and water.
Table showing classification :

0x:ganic

( Proteins and a few non-
Nitrogenous < protein compounds that

( contain nitrogen

NoQ-nitrogenous \

( Carbohydrates

^''^ {^2r

Examples of proteins are: The substances in egg
which solidify when heated; the substance in milk
that forms as a scum when the latter is heated and
that which clots or curds when rennin or acid is added
to milk; the white substance which appears as a
coating on meat when it is exposed to heat.

Familiar examples of carbohydrates are starches
and sugars.

Proteins

The proteins are indispensable constituents of
animal and plant cells; without them all life would
cease.

Composition of proteins. — Protein molecules have
a very complex structtu-e, knowledge of which is still

278 Physics and Chemistry

very limited, though it has been greatly added to
lately. Proteins consist of the elements carbon,
hydrogen, nitrogen, oxygen, sulphur, and sometimes
phosphorus and iron. The more complex proteins
contain thousands of atoms of these elements. The
non-mineral elements of protein molecules are* so
combined that they form what are known as anhydrids
of amino acids. These anhydrids are formed by
reaction between the OH groups of two molecules of
organic acid with a loss of water.

acetic acid CH3.COO
Example:

acetic acid CH3.CO

H CH,.CO

->0 4" HaO
OH CHj.dO

acetic anhydrid

Amino adds. — These differ from other organic
acids chemically in that their hydrogen is replaced by
what is known as amine or the amino group or radical,
which is NHa. For example, acetic acid is repre-
sented by the formula CH j CO a- H and amino acetic
acid by the formula CH,COa. NHa. Amine is some*
what similar to ammonia — NH3 — and ammonia is
formed from it during the decay of protein-containing
compounds.

Classification of proteins. — ^A very large number of
different amino adds have been obtained both by the
decomposition of organic compounds and by S3mthesis,
and as different kinds of proteins contain different
ntmibers and kinds pf these adds it can be appredated
that there is considerable variation in the nature of the
protdn of different foods.

Certain proteins, however, have similar characteris-
tics and according to these they have been classified
as follows:

Chemical Constituents of Food 279

Conjugated
proteins

Derived
proteins

Simple proteins *

Albumins

Globulins

Glutenins

Alcohol solubles

Albuminoids

Histon^

Protamines

Nudeoproteins

Glycoproteins

Phosphoproteins

Hemoglobins

Ledthoproteins

Primary
derivatives

Secondary
derivatives

fProteans

< Metaproteins

(. Coagulated pxoteins

{Proteoses
Peptones
Peptids

Simple Proteins

Simple proteins are those which, when digested or
otherwise hydrolyzed,* yield only amino adds or their
derivatives.

Albumins and globulins. — Proteins belonging to
these two classes are found in many of the same
substances. As a rule, however, there are more
albtmiins than globulins in animal fluids, as blood,
and more globulins in animal tissues and plants.

The albumins and globulins have many characteris-
tics in common. They are both colloidal and will not
diffuse through animal membranes and, tmder the
influence of heat, certain salts (as bichlorid of mercury,
silver nitrate, etc.), and various other substances^

* By hydrolysis is meant, the spliUin^ of complex molecules due
h Ikeir ahsorpiUm of water.

28o Physics and Chemistry

their molecules tend to aggregate together to form a
coagulum. They are both soluble in dilute salt
solutions, dilute adds and alkalies, but albumins are
also soluble in distilled water and concentrated sodium
chlorid solutions and globtdins are not. The classifica-
tion of the simple proteins placed under these two
headings was based largely upon these differences in
their solubilities.

The several different kinds of albumins and globu-
lins are given different names. Thus, albumin in
serous fluids and in blood is called serum-albumin;
that in eggs, ova-albumin; that in milk, lact-albtunin;
that in muscle tissue, myogen. The globulins of the
blood are called fibrinogen and sertmi-globulin or
paraglobulin; that in muscle tissue, myosin'; also
there are a few albumins and various globulins in
plants, but as their special names are not often used,
they need not be given here.

The glutemns and alcohol-soluble proteins. —
The glutenins and the most common alcohol-soluble
protein, gliadin, form the gluten of wheat flour,
which is its principal nitrogenous constituent. Gluten
is found also in other cereals, but, as will be seen later,
that in the other cereals is not quite the same as that
of wheat flour.

Albuminoids. — These are protein substances ex-
tracted from such matter as bone, cartilage, and
similar substances. They form the basis of gelatin.

' Myosin, it is thought, does not exist as such in the living
muscle, but is formed there by coagulation after death. The
change is thought to be similar to the transformation that occurs
in fibrinogen when blood clots. Rigor mortis — the stiffening of
the body after death — is due to the changes that occur in the
proteins after death.

Chemical Constituents of Food 281

The composition of the albuminoids differs from that
of the other simple proteins, and gelatin, though it
contains nitrogen, cannot be used in the diet as a
substitute for them, since it cannot be utilized in the
body, as other proteins are, for the building of muscle
tissue.

Histones and protamines. — ^These two simple pro-
teins are not common, they have been obtained from
the blood corpuscles of some animals and from the
spermatozoa of fish.

Conjugated Proteins

Conjugated proteins are those which have a mole-
cule or molecules of matter other than mineral united
to the protein molecule.

Nucleoproteins. — ^These are compounds of simple
proteins and nuclein or nucleic acid. They are con-
tained in the nuclei of cells and are relatively abundant
in such glandular tissues as the spleen, pancreas,
and liver, the cells of such organs containing many
nuclei.

Nucleic acid, on oxidation in the body, yields
substances known as the purin bodies ^ e, g., uric acid.
For this reason, foods containing a high per cent, of
nucleoprotein are eliminated from the diet in diseases,
such as gout, which are characterized by the presence
in the system of a comparatively large amount of uric
add.

Glycoproteins. — ^These are proteins which contain a
carbohydrate molecule attached to the protein.
Mucin, which is a constituent of the secretions of
certain glands and of the mucous membranes of the
respiratory and alimentary tracts, is an example.

282 Physics and Chemistry

Phosphoproteins. — ^These are compounds of the
protein molecule and some phosphorus-containing
substance or substances. Caseinogen of milk (the
protein that is clotted when rennin or add is added
to milk) and vitellin, the principal protein of egg-
yolk, are two of the most important proteins of this
class.

Hemoglobin. — ^This is a compound of a protein
called globin and a pigment (coloring matter) called
hematin that unites and parts with oxygen readily.
Hemoglobin is the essential constituent of the red
blood-corpusdes of the blood, for it is due to their
hemoglobin that the corpuscles can fulfill their func-
tion of carrying oxygen from the lungs to the tissues.
Hemoglobin contains iron and this constituent is
necessary both for its formation and functioning.

Lecifhoproteins. — ^These are compounds of protein
and lecithin, a peculiar phosphorized fat. They are
contained in nerve tissue, in mucous membranes, and
probably in small amounts in other tissues. Yolk of
egg is the food material in which they are found in
largest amounts.

Derived Proteins

Such proteins are derived from simple and conju-
gated proteins as the result of digestion and they
may be also obtained by boiling simple or conjugated
proteins in add.

The primary derivatives are those which have not
undergone any great change from their original form.
Secondary derivatives are those in which the change
has been carried to a greater degree. They are not
coagulated by heat.

Chemical Constituents of Food 283

Function of food proteins. — Protein food substances
are oxidized in the body, consequently they yield
heat and energy, but their special function is to pro-
vide building and repair material for the proteins of
the body.

Non-protein nitrogenous compounds. — There are
certain nitrogen-containing compounds in both plant
and animal foods that are not proteins. They have
little or no nutritive value, but they give flavor to
the food and stimulate the secretion of the digestive
juices. Examples of these compounds are the amids
of plants and the extractives of meat.

The amids are believed to be the form in which
nitrogen compounds are transferred from one part
of the plant to another. The extractives of meat are
substances formed in the animal body in the course of
metabolism.

Tests for Proteins

Certain tests are often used to discover if protein
substances are present in compounds. Some of these
tests consist in adding something to the matter to be
tested that will, if protein be present, tmite with it
and form a colored compotmd. Others consist in the
addition of a substance that will coagulate the protein
if it be present, or in the application of heat, which
will have a similar effect. As will be seen in the
experiments connected with the study of digestion,
derived proteins do not respond in the same manner
as the undigested proteins to all of these tests.

Three common tests which depend upon the forma-
tion of colored substances are the Piotrowski, Rose, or
biuret; the xanthoproteic; and the Millon.

284 Physics and Chemistry'

Methods of Pexforming Tests

Biuret. To 3 c. c. of the solution to be tested (in a
test tube) add an equal amount of sodium hydroxid
and a drop of a 1% solution of copper sulphate. If
protein is present, a violet or pink color is produced,
which, depending upon the nature of the protein.
See page 398.

Xanthoproteic. To 5 c. c. of the solution to be tested
add about one-third of its volume of strong nitric add.
If protein is present, a white precipitate will form.
Boil the solution for one minute; the precipitate will
turn yellow and partly dissolve; cool and add enough
anmionia to make the solution alkaline; an orange
color indicates positively the presence of simple or
conjugated proteins. I

Millon. Treat 5 c. c. of the solution to be tested
with half its volume of Millon*s reagent (see page 20),
A white precipitate is formed. Boil the mixture.
If protein is present, the precipitate turns brick red in
color or disappears and leaves a red solution.

Coagulation of Proteins

The majority of proteins are coagulated by heat;
important exceptions are albuminoids, the casein of
milk, proteoses, and peptones. Heat is therefore
sometimes used as a test for the presence of proteins in
Hquids, especially tirine. When the heat test is used,
a drop or two of dilute acetic add is usually added
after the liquid has been heated, because it intensifies
the coagulation and also dissolves earthy phosphates,
which may also be present, and which are likewise
predpitated by heat.

Chemical Constituents of Food 285

Dried protein matter is not coagulated as easily aa
that containing water, and this fact has two important
bearings on the destruction of bacteria, since heat
kills bacteria by coagulating their protein constituents :
(i) Dry heat causes evaporation of the moisture from
bacteria and the soft matter surrounding them, which
is one reason why it does not penetrate as thoroughly
nor act as quickly nor at as low a temperature as
moist heat. (2) Spores cont^n much less water than
the rest of the bacterial protoplasm and are thus
much more resistant to heat.

Heat coagulation will be discussed farther in connec-
tion with the chemistry of cooking.

Proteins are coagulated also by: (i) the salts of
heavy metals, as bichlorid of mercury, nitrate of
silver, copper sulphate, lead acetate ; (2) strong solu-
tions of alcohol (solutions of alcohol between 10 and
50 per cent, will precipitate proteins, but they will
noti as do stronger solutions, form an insoluble
coagulum); (3) alkaloidal reagents, as potassium
ferrocyanid; (4) tannic add and inorganic acids.

It is due to their effect on proteins that bichlorid,
silver nitrate, etc., act as poisons and as disinfectants,
since coagulation of the protein of living organisms,
be it of bacteria or human beings, will cause death.
Bichlorid cannot be used for the disinfection of sub-
stances containing much protein matter, because
the coagulum that is formed with protein is not a
disinfectant and it forms such a hard case around the
bacteria that they are protected from the influence
of the mercury. Alcohol 95 per cent, has no germi-
cidal action but a 70 per cent, solution will destroy
vegetative forms of bacteria in from fifteen to ten
minutes or less. The failure of the 95 per cent, to

286 Physics and Chemistry

act as a disinfectant is due to the formation of
a protecting envelope, by the coagulation of the
outer protein substance of the genns through which
the alcohol cannot pass to destroy their vital
principles.

The difference of the nature of the coagulum pro-
duced by different substances can be studied by
combining the white of egg and about 300 c. c. water,
putting about 5 c. c. of this solution into several test
tubes, adding a few drops of a different coagulating
reagent to each tube and carefully examining the
comparative toughness and testing the solubility of
the precipitates in water and dilute acid solutions.

Iliough precipitation is often spoken of as coagula-
tion, a precipitate that is readily dissolved is not a
true coagulum.

The clotting of milk and blood. — ^When milk is
treated with rennin and kept at body tepiperature, a
dot or curd is formed, due to the conversion of the
soluble caseinogen of the milk into an insoluble pro-
tein called casein. Likewise when blood is shed and,
under some abnormal conditions, in the living blood-
vessels, the soluble blood protein, fibrinogen, is changed
to an insoluble protein called fibrin and forms a clot.
This change in the fibrinogen is due to the action of
a ferment called thrombin, which is formed from a
substance called thrombokinase (that is liberated
from the blood-platelets and leucocytes on their
disintegration) by the influence of the calcium salts
of the blood.

The clotting of milk will be further referred to in
connection with the chemistry of cooking.

The clotting of milk and blood is often spoken of as
coagukUian, but some authorities object to the latter

Chemical Constituents of Food 287

term being used for this reaction since it produces
entirely new protein substances.

The Carbohydntes

Classification. — ^The carbohydrates are classified
as follows:

I Glucose or dextrose
Fructose or levulose
Galactose

[Sucroses
Disaccharids < Lactose

Polysaccbarids

[Maltose

'Celluloses

Starches

Dextrins

Glycogen

Gums

Pectins

Constituents. — The carbohydrates are composed of
carbon, hydrogen, and oxygen. The proportions in
which these elements exist in the molecules of the
different carbohydrates are as follows:

Monosaocharids — C6Hia06
Disaccharids — CxaHaaOzx
Polsrsaccharids — CeHzoOsx

Polysacchaiids — Gr. poly ^ many; Lat. saccharum
'^^ sugar. — The carbohydrates of this group are con-
sidered chemically as being complexes of the simple
sugars or monosaccharids, for though, up to this
time, the chemist has not succeeded in building
cellulose, starch, etc., from sugar, these polysaccharida

288 Physics and Chemistry

are made from sugar in plants, and starches are easily
changed to sugar in the course of digestion and in other
ways that will be discussed later.

Cellulose

Cellulose is, next to water, the most abundant con-
stituent of plants for it forms much of their frame-
work. The nature of cellulose varies in different
plants and in most plants at different stages of growth.
Thus the cellulose walls that hold the starch grains
of the potato are less fibrous than the stem of the
celery plant, and that of the latter is less tough than
the cellulose of the wood of trees. The cellulose of
young plants is more tender than that of older ones,
the cell walls of most plants becoming thicker and
tougher as they grow, due to increase in the de-
position of cellulose and decrease in the amount of
water.

Celluloses are insoluble in water, either hot or cold,
and in weak adds and alkalies, but strong adds and
alkalies hydrolyze them. When celluloses are partially
hydrolyzed, they react to the iodin test in the same
manner as the starches do. Nitric add converts cel-
luloses into nitro-celluloses, which are the substances
used as bases in the preparation of such matter as
explosives, collodion, and nitro-glycerin.

Digestibility of cellulose. — Some of the lower
animals apparently digest cellulose quite readily,
but, though the more tender forms are to a certain
extent permeable to the digestive fluids of the human
alimentary canal, all cellulose is very insoluble, and
in man whatever digestion of this substance does
take place occurs in the intestine, largely as the result

Chemical Constituents of Food 289

of bacterial action, and fatty adds seem to be the
principal product yielded. Though a large portion
of the cellulose of food may thus escape digestion,
a certain amount of it is a valuble adjunct to the
diet of normal individuals, except very young children,
because it stimulates peristaltic action in the intes-
tines and thus prevents constipation.

Starch

Starch is the principal form in which plants store
their food supply. It is stored more especially in the
roots, tubers, fruit, and seeds.

Properties of starch* — Starch is insoluble in water.
When heated, starch grains swell and rupture and
prolonged exposure to heat causes chemical changes
which render them soluble. The substance thus
produced is known as dextrin. If .heated with acid
and as the result of digestion, starch is changed to
dextrose.

When dry, starch will keep in good condition for
a long time, but it is readily attacked by micro-
organisms if it becomes moist, and in such case will
mould or ferment and become sour.

Starch is obtained chiefly from wheat, com, rice,
and potatoes; and arrowroot, sago, and tapioca are
nearly pure starch.

Test for Starch

A test very commonly used to detect the presence

of starch in a substance is the iodin test. It is as

follows: A drop of iodin solution, 3%, is added to

the solution to be tested. If the material to be

290 Physics and Chemistry

tested is solid, it is boiled for a minute with water,
so that it will be in solution, and cooled before the
iodin is added. If starch is present, a blue color will
develop, due to the formation of iodid of starch.
(N. B. — The reaction will not take place properly If
the material being tested is hot.)

Dextrin

Occurrence. — Dextrin is only occasionally fotuid in
imcooked foods. It is formed when starch is heated
to about 200^ C. (the crust of bread is an example)
and when starch is boiled. It is the first product
formed in the digestion of starch.

[Test for Dextrin

The iodin test, as used for starch, is also fre-
quently used to detect the presence of dextrin in
a substance. If dextrin is present in the material
tested, the iodin will turn either purple, red, or
white. The reason for this difference in color is given
on page 398.

Glycogen!

. Nature and occurrence. — Glycogen, known also as
animal starch, is a white powder that is soluble in
water. It is extracted from liver. It is formed
in the animal body, in the liver, from glucose, and is
stored in the liver and, to some extent, in the muscles,
but that in the muscles is decomposed soon after death;
therefore, liver is the only meat that contains any
amount ot carbohydrate. Oysters and other shell<^

Chemical Constituents of Food 291

fish, however, contain as much as 9 per cent,
glycogen.

Inulin

This is a soluble starch-like substance that is found
dissolved in the sap of some plants, especially the
Jerusalem artichoke.

Pectin

Pectin substances are related chemically to both
starches and gums. It is thought that they are
formed in plants by the combining of several simple
carbohydrates. It is the pectin substances that,
under conditions which will be discussed later (page
362), allow of jellies being made from certain fruits
without the aid of gelatin. The test for pectin will
be found on page 362.

Gums

These are various viscid substances contained
in many plants and in the wood and bark of several
trees. They have the same chemical composition as
the other polysaccharids.

Disaccharids

The sugars belonging to this class are the sucroses,
lactose, and maltose.

The disaccharids were so called from the Gr. di^
double and Lat. saccharum^ sugar, because, when

292 Physics and Chemistry

hydrolyzed, one molectile of a disaccharid gives two
molecules of simple sugars or monosacchari(te.

Sucroses

The more common sucroses are cane sugar, beet
sugar, and maple sugar.

Sucrose is a common constituent of plants. It
occurs in small qtiantities in several fruits, ustially in
combination with dextrose and levulose, and in a few
vegetables. It is found in largest amotmts in the
sugar cane, beets, the maple tree, pineapple, and
carrots. It is from the three plants mentioned first
that it is usually extracted.

Sucrose is easily hydrolyzed in digestion and by
boiUng in water or other liquids, more especially acid
solutions. When hydrolyzed every molecule of su-
crose yields a moleaile of dextrose and a molecule of
levulose. Sucrose can be changed to caramel by the
application of dry heat.

Test for Sucrose

The presence of sucrose in food can be determined
by boiling a few c. c. of a solution of the matter to be
tested with an equal quantity of hydrochloric acid.
If sucrose is present, a deep red color will develop.

Lactose

Lactose, known also as sugar of milk, occurs in the
milk of all mammals. Experiments seem to show that
it is made in the mammary glands from glucose which
secretory cells of the glands take from the blood.

Chemical Constituents of Food 293

Lactose is easily changed to the monosaccharids
glucose and galactose by heating it with adds, and
in digestion. Lactose will reduce Fehling's solution,
but it requires 0.68 gm. of lactose to reduce lo c. c. of
Fehling's. As will be seen later (page 398) , one method
of determining the nature of a sugar is to ascertain if
it will reduce certain solutions and how much of the
sugar is required to cause the reduction of a given
amount of the solutions.

Maltose

Maltose or ntialt sugar is formed from starch by the
action of diastatic enzymes (see page 389) that exist
in certain plants. It is therefore an ingredient of
germinating cereals, of malt and malt products, and in
animals it is formed during digestion. It is easily
changed to glucose by heating it with adds, by the
action of yeast, and in digestion.

Maltose is the prindpal constituent that the
brewer extracts from malted grains for the making
of beer, ale, etc. In the process to which it is subjected
it is changed to glucose, and this is easily oxidized,
thereby forming alcohol and, if the process is con-
tinued, CO a and HaO.

Monosaccharids

The monosaccharids were so named from the Gr.
monos^one and Lat. saccharum^ sugar.

Dextrose

Dextrose was so named from the Lat. dexter '^
right, because it turns polarized light to the right. IV

294 Physics and Chemistry

is known also as glucose, diabetic, and grape sugar.
It is found in combination with other sugars, especially
levulose, in many fruits and a few other plants.

The disaccharids and starches are easily changed to
glucose by boiling them with adds and much of the
glucose sold is made from starch in this way. Glucose
isonly about half as sweet as cane sugar.

Normally, glucose is present in the blood in the
proportion of o.i per cent. This will be further dis-
cussed in the sections on digestion and metabolism,

Levulose

Levulose (Lat. IcBvus^left) so called because it
turns polarized light to the left, is known also as
fructose and fruit sugar. It is an isomer of glucose —
{. e., it contains the same elements in the same propor-
tions as glucose, but in a different combination. The
way in which the chemist demonstrates this difference
of arrangement is shown on page 157. Levulose is
not found in the blood, other than that of the portal
vein, being changed into glycogen in the liver. It is
found associated with glucose in fruit and in honey.

Galactose

This monosaccharid is not found in nature, it is
formed from lactose by hydrolysis.

Tests for Monosaccharids

It is often important to discover if glucose is present
in a food or other matter — e.g., the urine. The Peh-
ling's test is one very commonly used for this purpose.

Chemical Constituents of Food 295

FehBng's test. — ^Take eqtial parts of Pehling's solu-
tions I and 2 (see page 19), about 2 c. c. of each. Boil'
this, if it remains dear, add an equal amotint of the
solution to be tested, and boil. If glucose is present, a
red precipitate will form ; because the glucose by taking
away oxygen from the cupric hydroxid changes it to
the red insoluble cuprous oxid.

Other conmion tests are as follows:

Baxfoed's test — Boil a few c. c. of freshly prepared
Barfoed's reagent and add, while the solution boils,
drop by drop, some of the solution to be tested. If
glucose is present, a red precipitate of cuprous oxid is
formed, either at once or on standing.

Benedict's test — To 5 c. c. of Benedict's reagent, in
a test tube, add about 8 drops of the solution to be
tested. Boil the solution for about 2 minutes and then
allow it to cool. If glucose is present, the solution
will become filled with a precipitate either red, yellow,
or green in color, depending upon the concentration
of the sugar.

These tests aU depend upon the fact that the
monosaccharids have the same chemical construction
as the aldehydes and like them will reduce such
substances as the reagents used in these tests, thereby
changing certain soluble substances into insoluble
ones with the colors mentioned.

Moore's test — ^Boil the solution to be tested with a
little sodium hydroxid. If glucose is present, the
solution will turn yellow, due to the formation of
caramel as the result of the hot alkaline on the glucose.

Fermentation test* — Fill the long arm of a f ermenta-

'This precautioa is necessary because the solution often
deteriorates soon after It is prepared. If, when boiled, it becomes
dottdy, it Is not fit to use*

296 Physics and Chemistry

tion tube (page 19) with the solution to be tested
and add a small piece of yeast cake. The liberation
of gas (carbon dioxid), as described on page 359,
indicates the presence of sugar.

Fats and Oils

As stated in Chapter XIV., fats are esters of glycerin
and fatty adds.

They are classified as:

Pats

Fixed oils

Essential or volatile oils.

The essential or volatile oils. — These oils are so
called because they are volatilized at ordinary tem-
peratures. If a little volatile oil and a little fixed
oil are dropped on paper, the latter will leave a
mark, but the former, being volatile, will quickly
disappear.

The essential oils vary considerably in their com-
position, but the majority of them consist chiefly of
such substances as the terpenes, or camphors, or
similar substances. Thjsy are all entirely different
in their chemical composition from the fixed oils.

The essential oils are the important constituents of
spices and similar substances; it being to their oils
that these things owe their flavor. As the oils are
volatile, they can be extracted from the plants con-
taining thfim by distillation. Oil of cloves, oil of
peppermint, and other oils used for flavoring are
obtained in this way.

Nature of the fixed oils aiid fats. — The fixed oils
and fats are chemically alike and their classification is
based on their physical condition; fats being solid at

Chemical Constituents of Food 297

ordinary temperatures and oils liqtdd, but a fat when
melted is called an oil, and an oil when solidified a fat.

Fixed oils and fats are derived from both plants and
animals. They are composed of three or more simple
fats. The molecules of the simple fats, it will be
remembered, consist of three molecules of fatty add
and one molecule of glycerin.

The most common simple fats are stearin, palmitin,
and olein. The first two mentioned are solid at
ordinary temperatures, and olein is liquid, therefore
the greater the amount of olein in a fat, the lower
its melting point. The fats of beef and mutton, for
example, contain a larger per cent, of stearin than lard
and butter and are therefore harder.

Nearly all animal fats are mixtures of these three
fats, but the fat of milk (cream) and consequently
butter contains several other simple fats of which the
principal one is butyrin. Plant oils contain little or no
stearin, but many of them have several other simple
fats.

Solubility. — Fixed oils and fats are insoluble in
water, but they are readily dissolved in hydrocarbons,
ether, carbon bisulphid, chloroform, and hot alcohol.
They are saponified by hot alkalies and in digestion.

Function. — The function of fats in the body is to
provide heat and energy and material for building
fatty tissue.

Lecithins

These are substances related chemically to the
fats. They are compounds of glycerophosphoric
add radicals and a nitrogenous base called chclin.

Lecithins appear to be an active component of both

298 Physics and Chemistry

animal and vegetable cells, but they are especially
abundant in the white matter of nervous tissue and
in the yolk of eggs.

Lecithins are digested in the same manner as the
true fats. Their function is not understood, but it is
thought that they may assist in the synthesis of the
nucleoproteins.

Mineral Matter

The mineral matter of food and the human body is
spoken of also as ash and salts. It is called ash
because, being non-combustible, it is fotmd in the
residue remaining when animal and vegetable sub-
stances are burned. The compounds found in the
ash are not necessarily exactly the same as those
contained in plant and animal tissues, for during
ignition many chemical changes and consequent
transformations occur. The term salts is used be-
cause the mineral matter occurs in plant and animial
tissues chiefly in the form of salts.

The salts present in largest amounts in food and
the human body are the chlorids, sulphates, phos-
phates, and carbonates of potassium, sodium, calcium,
and magnesium.

Function of salts in the body. — ^As salts are not
oxidized in the body they do not yield heat and
energy, nevertheless they are necessary for life;
for, they are essential constituents of protoplasm;
they maintain the neutrality or slight alkalescence
of the body secretions, blood, and other fluids; they
are necessary for the maintenance of the elasticity
and irritability of muscle tissue; calcium salts are the
source of the firmness and rigidity of the bones;

Chemical Constituents of Food 299

sodium chlorid is the substance from which the hydro-
chloric add of the gastric jtiice is made ; iron is essential
for the making of the hemoglobin of the red blood-
corpusdes and for the oxygen-carrying power of the
latter and it is an equally important constituent of the
chlorophyl of plants.

Solubility of salts. — All the chlorids and the potas-
sium and sodium sulphates and phosphates are soluble
in water ; the normal phosphates of caldum and magne-
sium are insoluble in water, but soluble in dilute adds.

Common Tests for Determining the Presence of
Salts in Food and Other Matter

To about 5 c. c. of the solution to be tested add a
few drops of strong nitric add and then a few drops of
a 1% silver nitrate solution (AgNOj). If chlorids are
present, a white flocculent predpitate will appear;
because, in the presence of nitric add, the chlorin of
the chlorids unites with the silver, forming silver
chlorid which is insoluble in water and dilute acid
solutions. Write the equation for the chemical re-
action that occurs. (The nitric add does not enter
into the reaction.)

Test for iron. — To about 5 c. c. of the solution to
be tested, add a drop of nitric add and then 2 c. c. of
potassitun thiocyanate (KSCN). If iron is present,
a deep red color will develop.

Test for phosphates. — ^To about 5 c. c. of the solution
to be tested, add a few drops of (i) concentrated nitric
add and (2) ammonitmi molybdate solution, (NHJa
M0O4. If phosphates are present, a yellow predpi-
tate of ammonium phospho-molybdate is formed.

Test for sulphates. — ^To about 5 c. c. of the solution

300 Physics and Chemistry

to be tested, add a few drops of HCl and then, slowly,
about 2 c. c. of a 5 per cent, solution of barium chlorid
(BaCla). If sulphates are present, a white insoluble
precipitate of baritim sulphate is formed.

Before testing a solid substance for mineral matter,
it must be incinerated (i. e., burnt until it is reduced
to ashes') and the ash dissolved in water, or, for the
extraction of salts that are insoluble in watep (see
page 299), water plus a little concentrated nitric acid
solution. This is filtered and it is the filtrate that is
tested, since the salts, being soluble in the liqtdd for
their extraction, will be present in it in solution.

Water

Functions. — ^Water, like the mineral matter of food,
has no fuel value, but it is an essential constituent of
all protoplasm, and it enters into the composition,
not only of the fluids of animals and plants, but even
of such hard substances as bone and wood. The
water of the blood of animals and the sap of plants
is the vehicle for distributing food material through
the organism and for carr^dng away waste matter to
parts from which it can be eliminated. Water dis-
solves food so that it can be used by the body, and it
is quite as essential to life as any of the other food
materials. The plant bereft of water quickly perishes,
and, though animal life will not succumb quite so
quickly, water is as essential for the well-being of ani-
mal cells as of those of the plants; therefore water lost
from the body, as by excessive perspiration, diarrhea,
or hemorrhage, shotdd be replaced as soon as possible.

' The usual method of doing this in a laboratory is to place
the material in a crucible and put this over a flame.

Chemical Constituents of Food 301

Origin of Food Material

Photosynthesis (Gr. photos « light and synthesis
^composiHon). — Photos3mthesis is the name given
to the processes whereby, under the influence of
energy derived from the sun and chlorophyl (the
green coloring matter of plants), cells in the leaves of
green plants put together COa, which they obtain
from the air, and H3O, which they absorb from the
soil, to form sugar and starches.

The exact nature of the reactions that occur in
these processes is not known, but the following equa-
tions show how starch could be made from these
compounds:

i2CX)a + laHaO - aCeHioOs + 246 + aHaO

The manufacture of starch, however, is probably
seldom, if ever, such a simple matter as this. It is
thought that sugars of the monosaccharid type are
formed first and the more complex sugars and
starches made from these. This could happen as
follows:

6C0a + 6HaO - C6Hia06 + Oia
C6Hia06 — HaO - CbHioOs

but, even in the manufacture of simple sugars, it is
considered that certain preliminary steps, in which
formaldehyde and peroxid of hydrogen are formed,
may be usual. Thus

Fbmial- Rydrogtn
dehydo peroxid

COa + jHaO - CHaO + aHaOa
6CHaO - C«HzaO«

302 Physics and Chemistry

Metafitasis (Gr. meta « beyond and histanai » to
place). — In addition to sugars and starches, plants
must make cellulose (which constitutes the basis of
their own structures), fats, and proteins. Cellulase
is chemically very similar to starch. Fats and proteins
have the same elements as starch, but in very different
proportions, and proteins contain in addition N, S,
and sometimes P and Fe. These elements plants
obtain from the earth in salts, such as nitrates, sul-
phates, etc. Still less is known of the processes that
occur in the making of fats and proteins than of those
by which sugar and starch are formed, but it is thought
that these substances are made from starch and that
the latter is broken down into simpler substances
before S3mthesis occurs. The forming of proteins
and other complex compounds, including the destruc-
tive processes necessary for their formation, are
spoken of as metdstasis.

Photosynthesis takes place only in the green leaves
of plants and in the daylight or under strong electric
lights, but metastasis takes place in all parts of growing
plants and in the darkness as well as in the light.

It is through their leaves that plants absorb the
CO a which they require for their food and a small
amount of water enters in this way, but by far the
greatest amount of their water supply is obtained
from the soil, being absorbed by the surface cells of
their roots and root-hairs. This water has in solution
salts, including the nitrates, etc., required for the
manufacture of proteins.

The nature and purpose of sap. — ^The sap of plants
consists of water holding in solution the salts absorbed
from the earth and the food material that was made
in. the principal food factory — the leaves — some of

Chemical Constituents of Food 303

which must be carried to the storehouses — ^the roots,
seeds, fruits, or flowers — ^f or storage and some to all
the cells of the plants for their nutrition. Thus,
sap is to the plant what blood is to the animal,
and, like blood, it must circulate throughout the
organism.

The forces which cause the circulation of sap. —
The factors which cause the movement of sap in
plants are still but imperfectly understood, but
five important forces are: (l) the avidity that
protoplasm has for water; (2) the life processes
of the plant; (3) osmods; (4) evaporation; (5)
capillarity.

Due to the avidity that protoplasm has for water,
it will absorb water until it is saturated; therefore, as
the water in the cells of the leaves evaporates or is
used up in the life processes of the plant — e. g,, the
manufacture of sugar — ^the uppermost cells absorb
water from those beneath them, and these, in turn,
take it from those which they overlie, and so on. This
constant evaporation and absorption of water acts
very much as a suction pump and it assists the factors
upon which osmosis depends, see page 67, in causing
the fluid in the soil to osmose through the root-hairs
and roots and pass up the stem to the leaves, flowers,
etc.

In warm, bright weather, evaporation and the
chemical processes going on in the leaves occur much
more rapidly than in cold weather, consequently the
sap rises more rapidly and to a greater extent tmder
the former conditions.

The sap must descend, as well as ascend, for the
stems and roots need to be nourished and, as already
stated, most of the nourishment is formed in the

304 Physics and Chemistry

leaves. Less is known, however, of the forces
which cause the sap to descend than of those which
produce its ascent, but it is known that it descends
through the large outer cells that, in the tree, con-
stitute the bark. This is why removing its bark will
kill a tree.

Source of salts in the soil. — It was stated in a
preceding paragraph that plants got their nitrogen
and mineral supply from the soil. This being the case,
the soil must be constantly losing its supply of such
matter and it must be as constantly renewed if plants
are to grow in it. This is done by the use of fertilizers.
Many compotmds of the salts necessary for fertilizing
the soil are now prepared by the chemist, but, until
recently, animal excreta and decaying vegetable
matter were the only fertilizers to be had and they are
still very much used.

To understand how animal excreta can supply
the soil with mineral matter it is necessary to realize
that animal excreta contain not only salts eaten
in food, but also, especially the urine, salts formed
in the body by chemical reactions occurring in
metabolism.

The protein in plants and in animal excreta does not
exist in the form of nitrates, but when decaying
vegetable matter and manure are spread over the
ground they, by the influence of bacteria, undergo
decomposition, and their protein matter is slowly
formed into ammonia compounds, some of which,
uniting with oxygen, and in other wa3rs, are broken
down to nitrates and other nitrogen salts which are
capable of going into solution in the soil water and
being absorbed by plants.

Another way in which bacteria supply plants and

Chemical Constituents of Food 305

the soil with nitrogen is that various species are able
to absorb nitrogen from the air and some of these
species enter the roots of such plants as peas, beans,
clover, alfalfa, and they live and multiply in little
tubercles that develop on the roots in consequence of
the invasion of the plants by these organisms. The
bacteria, as they deVfelop in these nodules, in some
unknown way, combine the nitrogen they absorb so
that it is available for plants. It is thought that
perhaps the bacteria after absorbing the nitrogen
secrete a nitrogenous substance, some of which is
absorbed by the plant cells while a portion osmoses
into the soil. The nitrogen supply of the soil in
which such plants grow is thus increased, instead of
diminished, as it is when used for the growth of other
plants. The soil nitrogen supply is still fiuther
increased when the roots of such plants are allowed
to rot in the ground.

The food cycle. — ^As shown in the preceding pages,
plants and animals, including man, are absolutely
dependent upon each other for their sustenance, and
there is a continual cycle in progress by which one
form of life supplies the other with matter for their
life and growth. Animals eat plants and, when these
are oxidized in their bodies, they eliminate CO a and
other waste matter that plants can use for their food
and development. Man supplies CO, also by burning
plants, as wood, and plant products, as coal, oil, and
gas.

Effect of plant life upon the atmosphere.— Plants
not only supply man and other animals with food, but
they also keep the air pure by extracting CO a and
supplying oxygen. One source of the oxygen supply
can be seen in the equations on page 301. Oxygen is

3o6 Physics and Chemistry

freed also in the making of fats for, as can be seen in
the following formulas of some of the simple fats,
there is less oxygen in fat than in sugar and starch:

Stearin— CjHjCCisHjsOa),
Olein— CaHsCCisHjjOa),
Palmitin— CjHs(Cx6H3xOa)j

In some metastasis processes COa is liberated;
therefore plants eliminate a small amount of CO,,
especially at night when photosjmthesis is not taking
place.

CHAPTER XIX

NATUSB AND NUTRITIVE VALUE OF SOME OF THE

COMMON FOODS

Oasstficatioa of Poods — ^Nature, Digestibility^ and Nutritive

Value of the more Commoa Foods and Beverages —

Nature and Action ol Condiments and Spices.

Animal Foods

The more common animal foods include the ilesh
of mammalia — generally spoken of as meat — birds,
fish and other sea-food, eggs, milk, and honey.

Nutritive value of animal foods. — ^With the excep-
tion of honey, milk, liver, and shellfish, there is little
or no carbohydrate found in animal foods. The
reason for the absence of carbohydrate in meat is
that that which is present in the living animal is
drained off with the blood when the animal is slaugh-
tered, or else changed to lactic acid and other products
of the decomposition of glycogen and glucose shortly
after the death of the animal. Consequently the
only solids provided by the majority of animal foods
are proteins, fats, and mineral matter.

Animal foods arc usually a more expensive form of
nutriment than vegetable foods, but, as can be seen
by looking at the table on pages 340-344 they contain

307

308

Physics and Chemistry

more protein than other foods, and animal protein is
more thoroughly digested and absorbed than vege-

FiG. 6i. Cuts of Beef, i, neck;
2, chuck; 3, ribs; 4, shoulder clod; 5,
fore shank; 6, brisket; 7, cross ribs;
8, plate; 9, navel; 10, loin; 11, flank;
12. rump; 13, round; 14, second-cut
round; 15, hind shank.

table protein. Also, the flavor
of meat, the stimulating effect
of the meat extractives on the
glands which secrete the gastric
juice, the many uses of eggs and
milk, all make animal foods very
desirable articles of diet for the
majority of people.
Comparatiye digestibility of
animal foods. — ^The following list of the comparative
digestibility of common animal foods is one to be
found in several books on dietetics. The foods are
mentioned in the order of their digestibility, be-
ginning with the most digestible.

Nutritive Value of Foods 309

Milky oysters, soft-cooked eggs, sweetbreads, white
fish, chicken, lean beef, scrambled eggs, mutton, squab,
crisp bacon, fowl, tripe, lamb, corned beef, veal, ham,
ducks and game^ salmon, mackerel, herring, roast
goose, lobster and crabs, pork; smoked, dried, or
pickled fish and meats.

Pig. 62. Cuts of Veal, i, neck;
2, chuck; 3, shoulder; 4, fore shank;
5, breast; 6, ribs; 7, loin; 8, flank; 9,
1^; ic, hind shank.

Meat

Factors which influence the digestibility of meats. —

In general the amount of fat and connective tissue
and the length and strength of the muscle fibers which
make up the muscular tissue (i. «., the lean part of
meat) are the determining factors of the digestibility
of meat. If there is a large amount of connective
tissue or if the fibers are long and coarse, the meat will
be tough and, unless the condition is ameliorated in
the cooking, difiicult to masticate and otherwise
digest. The fibers in certain cuts of meat are coarser
than those in others, but the consequent toughness
can be often rectified by proper cooking, and as a rule

310

Physics and Chemistry

these cuts contain more nutximent and extractives
than the more tender ones.

The fibers of the flesh of young animals are shorter
and, consequently, the meat is more tender than that
of older animals, but an excess of fat in lamb and a
lack of extractives in veal make these meats, especially

Fig. 63, Cuts op Lamb and Mutton.
I, Neck; 2, chuck; 3, shoulder; 4, flank; 5,
loin; 6, 1^.

veal, less easy to digest than beef
and mutton. The large amount of
fat in pork interferes with its diges-
tion. Bacon, however, is usually
comparatively easily digested, partly
as the result of the action of the salt
used for its preservation upon the fat. With the ex-
ception of bacon, salted, pickled, and dried meats
are not as easily digested as fresh meat for the
fibers are hardened by the preservatives and by
drying.

Structure of meat. — Meat is ntiade up of muscle
fibers held together with connective tissue. Within
the fibers are the so-called meat juices which consist
of solutions of proteins, nitrogenous extractives, and
^ts in water. The extractives, which consist chiefly

Nutritive Value of Foods 3"

of substances such as creatin, xanthm, proteoses, and
peptones, ' give meat its flavor and they stimulate the
secretion of the digestive juices, but the greater part

Fig. 64. Cuts of Pokk. i. Head; a,

shoulder; 3, ribs and back; 4, middle cut; 5,
belly; 6, h*"*' ^ l-^i"*

of these substances are absorbed from
the intestine and excreted by the
kidneys without undergoing oxidation
and thus they have no real nutritive
value. Nevertheless, the flavor of
meat depending upon these extrac-
tives, their preservation is one of
the important considerations in the cooking of meat.

Birds

The flesh of birds is similar to that of meat, but the
musde fibers are shorter and therefore, especially in
young birds, the flesh is more tender. Chicken,
turkey, and squab are all easily digested, but ducks
and geese have too much fat, and the majority of

' Proteooes and peptones are not present in living muscle, but
ensymes in the tissues, ia the presence of the lactic acid, which
accumulates in the body after death, cause the hydrolysis t^
■ome of the simple proteins, thereby giving rise to these derived
pntdng.

312 Physics and Chemistry

birds classed with game are too rich in extractives to
be a suitable food for all invalids who are able to have
chicken and squab. The presence of extractives,
within limits, increases the digestibility of a food
because they stimulate the secretion of digestive juices,
but large amounts are to be avoided when there is
any gastric disturbance.

Fish

Fish are usually classed as scaly or vertebrate fish
and shellfish. The latter class includes the moUusks
and crustaceans.

Nature and nutritive value of the scaly fish. — These
fish contain more water and rather more mineral
matter, especially the phosphates of calciiun and
potassitmi, than meat, also they contain more gelatin,
but less fat and extractives. Consequently, pound
for pound, fish have not quite as much nutritive ma-
terial as meat, but they are more quickly digested, with
the exception of a few kinds in which the per cent,
of fat is above six, — e. g., eels, salmon, turbot, herring,
and codfish, the fibers of which are coarser than
those of the other white fish. Salting and drying fish
hardens the fibers and thus preserved fish are not as
quickly or as perfectly digested as fresh fish.

MoUusks. — ^The moUusks most frequently used
for food are oysters, clams, mussels, and scallops*
They have not a very high nutritive content; oysters,
for example, contain about 88.3 per cent, water, but
they are valuable for their flavor, and oysters, raw or
properly cooked, are quickly and fully digested. The
flesh of the other mollusks, especially scallops and
mussels, is tougher and therefore not as digestible as

Nutritive Value of Food 3^3

oysters. As can be seen in the table, page 340, the
moUusks contain glycogen.

Crustaceans. — ^The crustaceans usually used for
food are lobsters, crabs, and shrimps. The fibers of
the flesh of the crustaceans, especially lobsters, are
coarse and consequently these foods are neither easily
nor perfectly digested.

Milk

The milk secreted by any of the mammalian class
of animals is suited to the requirements of their young
and, as these differ, the quantitative composition of
the milk of different animals differs also.

The two milks most frequently compared are human
milk and cow's milk, the latter being often substituted
for the former in infant feeding.

The percentage composition of average samples of
each milk is as follows:

Casein' Lact
Water ogen albumin Fat Lactose Ash,

Human milk 8741 1.03 1.26 3.78 6.21 0.31

Cow's milk 87.17 3.93 0.53 3.64 4.88 0.71

' Digestibility and nutritive value of milk. — ^As can

be seen by comparing the composition of milk with
that of other foods (page 340), milk, though a liquid,
contains less water and more solid matter than some
vegetables, and, usually, it is one of the most per-
fectly digested foods so that there is little or no waste.
The high calcium content of milk makes it a particu-
larly valuable food for children who need calcium
for the hardening of their bones.
As shown in the accompanying table, there is more

314 Physics and Chemistry

caseinogen and less albumin in cow's milk than in
human milk, and this is an important difference when
cow's milk is used for infant feeding, since the soluble
caseinogen is changed by add and by the gastric
rennin into an insoluble substance, casein, which
forms a solid curd, and lact albumin undergoes no
such change. When milk is heated above 150^ P.
the caseinogen will not be clotted by rennin. The
reason for this is not known, but it is thought that it
is due to change in the nature of the calcium salts by
the heat, the calcitun salts being, it is supposed, neces-
sary for the change. The reason for this supposition
is that caseinogen will not change to casein upon the
addition of rennin to milk if the calcium salts have
been changed by combining with oxalates. This can
be seen by the following experiment.

Experiment 40. Procedure: Into each of three
test tubes potir about 5 c. c. of milk; heat that in tube
2 to a temperature of 150^ P., and maintain this tem-
perature for a few minutes ; add i o drops of ammonium
oxalate solution to the milk in tube 3 and then, to the
milk in all three tubes, add about 10 drops of rennin
solution. Stand the tubes in a water bath and keep
the temperature about 40° C. for 30 minutes.

Only the milk in tube i should be affected by the
rennin.

Certified milk. — By certified milk is meant milk:
(i) that is drawn from cows that have been declared
disease-free by an authorized inspector; (2) that is
drawn and kept under conditions laid down by the
Board of Health; (3) that does not contain a larger
number of bacteria than the law of the State permits;
and (4) that contains the percentage of fat required
by the State law. The detsdls of the law requirements

Nutritive Value of Foods 315

vary in diflferent States. New York State requires
that there be less than 30,000 germs per cubic centi-
meter of milk and that these be non-pathogenic, that
the milk contain an average of 4 per cent, fat, that it
be kept and sold in sealed, sterilized bottles and sold
on the same day that it reaches the city.

To prevent the multiplication of germs in milk it is
most important that everjrthing coming in contact
with it be absolutely clean and that it be kept at a
temperature of or below 40° P.

Pasteurized milk. — By pasteurized milk is meant,
milk that is heated sufficiently to destroy non-spore-
bearing bacteria. Milk pasteurized by what is known
as the holder method is brought to a temperature of
i45®P.,andlield there for thirty minutes; that pasteur-
ized by what is known as the flash method is gradually
brought to a temperature of 160® P. and the tempera-
ture maintained for one minute. In both methods
the milk must be cooled as quickly as possible, and it
is just as important to keep pasteurized milk cold as
fresh milk, since spores are not killed at a temperature
of 145® P. or even 160® P. and they will develop into
bacteria unless the milk is kept at a low temperature.

Experiment 41. Object: To test the comparative
effectiveness of the holder and the flash methods of
pasteurization.

Procedure: Into each of twelve sterile test tubes
put about 5 c. c. of fresh milk, plug the tubes with
sterile absorbent cotton, and put six of the tubes into
one water bath and six into another. Have the water
in both baths cold. Raise that in one to 145^ P.,
and maintain it at this temperattire for thirty minutes.
Raise the temperature of the water in the other bath
to 160^ P. And let it remain thus for one minute.

3i6 Physics and Chemistry

Chill the milk in both tubes as qtiickly as possible
by standing them in cold water and, as soon as they
are cool, put them in the ice-box. After twenty-four
hours, and every succeeding day, taste the milk in a
tube from each test. In which set of tubes did the
milk remain sweet longest?

There is a considerable difference of opinion as to
whether the digestibility and wholesomeness of milk
is increased or decreased by pasteurization. Some
authorities contend that pasteurization is beneficial
because it kills disease-producing germs and prevents
the caseinogen forming a clot in the stomach. Others
consider that it is better to use certified milk than
pasteurized milk because: (i) they think the change
in the salts which prevents the forming«>of casein is
not beneficial; and (2} the bacteria which cause the
fermentation of lactose and consequent production
of lactic acid are more easily killed than other varie-
ties which they, when present, prevent multiplying.
Some of these varieties, often present, cause changes
in the proteins of milk that give rise to substances
that are injurious, especially to children, but which,
unless present in excess, do not advertise their pres-
ence, as does lactic add, by souring or otherwise
flavoring the milk.

Sterilized milk. — By this is meant boiled milk.
This is not suitable for infant feeding because of the
changes caused in the salts by the high temperature
and the loss of nutriment in the scum that forms on
the top of the milk when it reaches a temperature of
about 170^ F. The chief constituent of this scum is
lact albtunin, but it also contains some salts, casein-
ogen, and fat.

Evaporated and condensed milk and cream. — These

Nutritive Value of Foods 3^7

are prepared by heating the milk or cream in a vacuum
pan until a large portion of the water is evaporated
and germs are killed, and then putting the liquid into
sterile cans and sealing these at once.

Desiccated milk. — This is milk that has been eva-
porated to a dry powder. It is prepared for use by
adding water to it.

KoumisSi matzooni artificial buttermilk. — ^These
and similar preparations are fermented milks. In
some preparations the fermentation is produced by
the use of yeast, in others by that of pure cultures of
lactic acid, producing bacteria. In any case, the
substance fermented is the glucose, and the curding
of the protein is caused by the lactic acid resulting
from this fermentation. These milks are quickly
digested and are often used by those suffering
from impaired digestive power. They are used also
in the treatment of intestinal putrefaction, for it
is believed that the lactic add inhibits the action
of the putrefactive bacteria always present in the
intestine.

Whey. — This is the watery, straw-colored liquid
that separates from the curd formed in milk by rennin
or acid. Whey consists of water, lact albumin,
lactose, and mineral matter.

Cream. — Cream is the name given to the fat which,
in the form of an emulsion, rises to the top of milk
when it is allowed to stand. The top layers of cream
will contain more fat and less protein than those
nearer the surface of the milk. Cream is also separa-
ted from milk by the use of the centrifugal separator,
and that obtained in this way is much richer than
that obtained by gravity and it can be better freed
from entangled caseinogen. The fat of cream being

3i8 Physics and Chemistry

in the form of an emulsion, is digested more easily
than other fats.

Butter and its substitutes. — ^Butter is made by
agitating cream, usually in utensils known as chums,
and thereby causing the particles of fat to ding to-
gether in masses. The melting point of butter is low
and it is thus one of the most easily digested of animal
fats. When foods are fried in butter, however, their
digestion is interfered with, because fat is not digested
until it reaches the intestine, and if carbohydrates
and proteins are encased in a hardened fat envelope,
the digestive juices of the mouth and stomach cannot
attack them properly.

Renovated or process butter is made by melting
rancid butter, removing any disagreeable odor and
taste by various means, and churning the butter with
some new milk to which, usually, cultures of bacteria
that will develop an agreeable flavor have been added.
The great objection to the use of renovated butter
is that the germs which produce rancidity sometimes
develop injurious substances in the butter.

Margarini oleomargarini and the majority of other
artificial butters are made from meat fats with,
usually, a little butter or milk to improve the flavor.
These substances can be sold at a lower price than
good, fresh butter, and though not as good from any
dietetic standpoint as fresh butter, they will, when
properly prepared, keep better than butter and they
are more wholesome than renovated or old butter.

Cheese. — Cheese is made by coagulating the casein-
ogen of milk. Usually this is done with rennin. As
a rule, there is a considerable, though very varying,
amount of fat entangled in the casein. As can be
seen by studying the table on pages 340-344, cheese

Nutritive Value of Foods 319

contains less water and more protein than the major-
ity of foods. As it is such a concentrated food, it
cannot be eaten in large amounts, especially by per-
sons of sedentary habits, and it is very likely to cause
gastric disturbances in those whose digestion is im-
paired, but it has been found that 95 per cent, of
the fat and 92 per cent, of the protein are ultimately
absorbed by the average healthy adult and that cheese
stimulates the secretion of the digestive juices. As
many cheeses are cheaper than eggs and meat, cheese
is a valuable source of protein food for healthy adults
of restricted means. Cooking cheese renders it less
digestible since it hardens the casein.

Eggs

Eggs, though lacking carbohydrates, are a particu-
larly valuable food, for they contain easily digested
proteins, more lecithin than other foods, and an abun-
dance of mineral matter, especially phosphates and
iron, and the iron is in a particularly assimilable
form.

The protein of the white is chiefly albiunin, that
of the yolk is partly albumin, but largely vitellin — a
phosphoprotein; part of the fat is in the form of
lecithin. The sulphur present in egg, both in the
white and yolk, will sometimes give rise to flatulence,
because, especially when a person is constipated, the
sulphur is likely to unite with hydrogen and form
hydrogen sulphid, a light ill-smelling gas. When
silver comes in contact with eggs, its stirf ace blackens,
due to the union of the sulphur with it and the con-
sequent formation of silver sulphid which remains
as a covering on the metal.

320 Physics and Chemistiy

Honey

This is a mixttire of sugars prepared by bees from
substances they extract from the exudations of various
plants. Genuine honey consists chiefly of Icvtdose
and glucose, with a small amoimt of sucrose and about
17 per cent, water. The quality and flavor of honey
depend largely upon the nature of the flowers from
which the bees secured their food material. As honey
consists so largely of invert sugars, the greater portion
of its substance is ready for absorption and does not
undergo digestion.

Plant Foods

Classification. — ^The plant foods in common use
are classified as cereals, vegetables, fruit, nuts, ftmgi,
and sugars.

Cereals

This class of foods includes plants of the grass
family such as wheat, rye, oats, barley, rice, and com.
The composition of the cereals varies, but they are all
rich in carbohydrates and mineral matter, and cooking
does not entail any loss of nutriment.

Wheat — ^Wheat, especially in the form of fiour, is
one of the most universally used of the cereals. There
are several varieties of wheat, and the fiours and
breakfast foods made from them differ because of
this and, more especially, as the result of different
methods of preparation. The protein of wheat is
chiefly gluten, a sticky, tenacious substance which is
a compotmd of gliadin and glutenin. The elasticity

Nutritive Value of Foods 321

of gluten and its power to hold the gas produced in
dough by yeast, baking powders, etc., is influenced
by the proportions of gliadin and glutenin that it
contains — ^about 65 per cent, of gliadin to 35 per cent,
of glutenin is usually preferred for bread flour. Spring
wheat (i. €., that sown in spring and maturing in the
late summer) contains more gluten and less starch
than winter wheat (that sown in the fall and maturing
in the early summer) and is preferred for making
bread, but winter wheat is the best for pastry.

Oatmeal. — ^The meal of oats is also much used for
food. Oatmeal contains more protein, fat, and min-
eral matter than other cereals. The protein consists
of a substance called avenin, which is somewhat simi-
lar to the legumin of peas, and a small amotmt of
gliadin. As oatmeal does not contain gluten, it
cannot be used for bread-making.

Barley. — ^Barley contains a relatively large amount
of salts, fat, and cellulose, but less protein and digesti-
ble carbohydrates than the other cereals. Its salts
are soluble in water and hence are easily extracted.
This is one reason why barley water is so much used
for diluting top milk for infant feeding.

Sprouted and dried barley, generally known as
malt, contains a ferment called diastase which converts
starch to sugar.

Com* — Com is a widely used cereal both in its
natural state and ground into meal and starch. Its
protein has not all the characteristics of a true gluten
and thus its meal has to be mixed with rye or wheat
flotu" for bread-making. Starch is one of the most
valuable products of com. The nutritive value of
com compares favorably with that of wheat. When
eaten in its natural state, com occasionally causes

322 Physics and Chemistry

irritation in the intestines on account of its cellulose
exterior, which may resist digestion, but it is stated
that analysis of feces has shown that young com,
when properly cooked, is more thoroughly digested
than is generally supposed.

Rice. — Rice is very extensively used for food. It is
poor in proteins and fat, but rich in starch; it contains
a fair amount of mineral matter.

Rye. — ^The composition of rye is very similar to
that of wheat. Its gluten, however, contains more
gliadin than does that of wheat and it is therefore
more sticky and tenacious and, consequently, bread
made with rye flotir is darker and less porous than
wheat bread.

Substances similar in composition to the cereals,
though not belonging to the same botanical classifi-
cation are: The grain buckwheat; tapioca, which is
prepared from the root of the cassava plant; sago,
which is prepared from the pith of the sago palm;
arrowroot, a starch obtained from the roots of several
plants grown in different tropical countries.

Vegetables

Vegetables are often classified as the roots and
tubers, green vegetables, and legumes.

The roots and tubers. — ^The vegetables thus classi-
fied are those of which the root or bulb is used for
food, e, g., potatoes, parsnips, carrots, beets, turnips,
salsify, onions.

These vegetables contain from 75 to 95 per cent,
water and they are all relatively poor in protein and
in fat, nevertheless they are of value in the diet on
account of their flavor and their mineral salts.

Nutritive Value of Foods 323

Potatoes have a higher nutritive value than the
other roots and tubers and are easily digested; they
are particularly rich in alkaline potash salts and are
thus a valuable adjunct to meat in the diet, the latter
being a source of acids in the system. Potatoes,
however, contain little iron or calcium salts and there-
fore, unless mixed with milk or egg, must not form
too large a portion of children's vegetable supply.

The carbohydrates of beets, carrots, parsnips,
salsify, and turnips are largely cellulose and sugar, and
as the latter is soluble in water there is a great loss
of nutrient in the cooking of these vegetables.

Green vegetables. — ^The vegetables often classed
as greens are those of which the stalks and leaves
are used; e. g,, cabbage, cauliflower, asparagus, French
artichokes, spinach, lettuce. The majority of these
vegetables have an even lower nutritive value than
the roots and tubers, but they are valuable for their
flavor and salts; also they give bulk to the diet, and
their cellulose causes a mild irritation of the intestinal
tract which stimulates peristalsis and thus helps to
prevent constipation.

Legumes* — ^The principal legiimes used as food are
peas and beans — of which there are many varieties —
and peanuts.

The legiunes contain more protein than other vege-
table foods, but the protein is in the form of legumin,
and this is acted upon mainly by the ferments in the
intestine; thus, legumes are not readily digested in
the stomach and sometimes, especially when the
vegetables are old and the cellulose thus hardened, a
considerable portion may escape digestion. Passing
peas and dried or Lima beans through a colander
after they are cooked, and thus removing the harder

324 Physics and Chemistry

cellulose, greatly increases their digestibility. Flatu*
lence is sometimes caused by eating a large amount
of beans, because (i) the gas hydrogen sulphid may
be formed from the sulphur they contain, and (2)
methan gas is sometimes produced, probably by the
decomposition of the bean germ by the bacteria that
are always present in the intestine.

Eggplant, cucumber,' vegetable marrow, ptunp-
kins, tomatoes, from the manner of their growtib, are
sometimes classed as fruit, though they are used as
vegetables. Their nutritive value is not high, but
they give bulk and variety to the diet and furnish
mineral matter. The cellulose of cucumbers is too
difScult of digestion to allow of the use of this plant
by invalids and small children.

Fruit

Fruits consist principally of water holding in solu-
tion sugars, small amounts of proteins, pectin, and,
in some fruits, starch; also they contain acids, essen-
tial oils and aromatic oils to which their flavor is due,
and cellulose. The cellulose in the immature fruit
is insoluble and very indigestible, but it becomes softer
and more soluble as the fruit matures. Though the
majority of fruits have not a ver>'^ high food value
they are of use for their flavor, for the bulk which
they add to the diet, for their mineral matter and
their acids. The principal acids of fruit are: malic
add, found more especially in apples, pears, currants,
berries, grapes, cherries, pineapples ; citric acid, which
occurs more especially in lemons, limes, grape fruit,
oranges, currants, and gooseberries; tartaric acid,
found chiefly in grapes; racemic acid, an add that

Nutritive Value of Foods 325

resembles tartaric add, and is found chiefly in grapes.
Acetic acid is found in fruits undergoing decay, as
it arises from the fermentation of grape sugar, but it is
not a constituent of good fruit.

Nuts

By looking at the table on page 344, it will be seen
that nuts contain comparatively little water and a
high content of protein and fat, and experiments have
shown that when nuts are not eaten in large quanti-
ties at a time or at the end of a heavy meal, they are
much more quickly and thoroughly digested than
was previously supposed. Nuts and fresh fruit form
a good combination, nuts being deficient in carbo-
hydrate and a very concentrated food, and ripe fruit
containing easily digested carbohydrate and being
bulky in proportion to the food value of its contents.

Fungi

The ftmgus in most common use is the mushroom.
Judging from the chemical analysis of the mushroom,
as shown on page 343, this fungus would seem to have
the same food value as the grieen vegetables, but it
has been found that mushrooms are neither thoroughly
digested nor absorbed, and this, of course, lessens
their nutritive value.

CondimentSi Spices, and Flavoring Extracts

By condiments are meant substances, such as the
various peppers and salts, used to flavor food.
Condiments, with the exception of sodivun chlorid.

326 ' Physics and Chemistry

spices, and other flavoring maXter, are obtained from
variotis parts of plants, some being prepared from the
stems and leaves {e. g., bay leaf, sage, sweet marjo-
nmi), others from the bark (e. g., cinnamon), others
from the buds and flowers (e. g., cloves and saffron),
some from fruit (e. ^., allspice, capsicum, juniper,
pepper, vanilla), and still others from the seeds {e, g.,
anise, caraway, celery seed and salt, coriander, mus-
tard, nutmeg).

Many of these substances owe their properties to
the presence of a volatile oil which can be extracted
and used separately. One method of extraction is
by distilling the oil with steam; oil of cloves, oil of
cinnamon, and several others are prepared in this way.
Pressure is another method of obtaining oil from
plants. The oil of lemon, from which lemon extracts
are prepared by dissolving the oil in alcohol, is ex-
tracted from lemon rinds by pressure. In some in-
stances the active principle or flavoring matter is
extracted from a substance by the use of a solvent,
e. g., vanilla extract is made by extracting the active
principle of the vanilla bean — vanillin — by soaking
the bean in dilute alcohol. Artificial, so-called, vanilla
extracts are now made, which are cheaper than, but
not as good as, the true extracts. One variety is made
by oxidizing eugenol, a substance in the oil of cloves,
with potassium permanganate.

Food value.— Condiments have no food value in
themselves, but if not used in excess they help in the
digestion of food by stimulating the flow of digestive
juices. They do this in two ways: (i) by improving
the aroma and flavor of the food, and (2) by a slight
irritation of nerve endings in the gastric mucous
membrane. If the irritating condiments are used in

Nutritive Value of Foods 3^7

excess, the irritation they produce may cause con-
gestion of the gastric mucous membrane and conse-
quent digestive disturbances.

Beverages

Caffein and theobromin beverages. — ^The caSein
and theobromin beverages in most common use are
coffee, tea, chocolate, and cocoa.

Coffee

Coffee is prepared from the berry of the coffee tree
by hulling and drying the berry and, later, roasting
and drying the seeds. Sometimes the seeds are glazed
in order to prevent a loss of the volatile substance to
which the flavor and aroma of coffee are due. The
glaze ordinarily used is prepared from sugar, and the
pure food laws of the United States prohibit the use
of other glazes unless their presence and nature are
stated on the label, but some countries permit the
use of resin, shellac, and similar substances.

Sources of coffee supply. — True Mocha coffee, which
has been always very generally considered one of the
best coffees, comes from Arabia, but much of the so-
called Mocha now sold comes from the West Indies,
Brazil, and other South American countries. Java
coffee, from the island of Java, is another favorite
coffee, but much of the so-called Java comes from
various places and may or ma}' not be good. That
coming from Bogota, S. A., is said to be most like the
true Java. More than half the coffee supply for the
world now comes from Brazil and various localities
in the northern part of South America. Other im-

3^28 Physics and Chemistry

portant sources of supply are Central America and
the West and East Indies.

Composition of coffee. — Roasted coffee contains
0.6 to 2 per cent, of caffein, a varjring amount of
caffeol — the volatile oil to which the aroma and flavor
are due — and a large amount of caffeo-tannic acid.
A cup of coffee solution, as usually prepared, may
contain from iH to 3 grains of caffein; the amount of
caffeo-tannic acid will vary according to the method
of preparing the beverage. If the coffee is prepared
without boiling, or if it is boiled but a short time and
used, or removed from the grounds, at once, it will
contain but a small amount of the acid. The caffeol
is developed during the roasting of the seeds and,
being volatile, it gradually decreases in amount after
the seeds are ground. Therefore the flavor of coffee
will be stronger if it is not ground until shortly before
use, and there will be a great loss of flavor unless the
ground coffee is kept in air-tight cans and the coffee-
pot kept covered while the beverage is being prepared.

Action of coffee constituents on the system. — ^The
caffein of the coffee acts as a cerebral stimulant. If
coffee is not taken in excess, it renders the mind clearer
and more alert and it increases the power of concen-
tration; in fact, all the higher intellectual faculties,
as reasoning, self-control, judgment, may be stimu-
lated. Through the influence of caffein on motor
cells of the nervous system, coffee improves muscle
tone, and stimulates the circulation and the respira-
tion; also, it lessens fatigue and may promote a sense
of well-being. If coffee is taken in excess, the caffein
over-stimulates the nervous system and will lessen
the powers of concentration, clear judgment, etc.
Caffeol acts as a local irritant in the intestine, thus

Nutritive Value of Foods 329

promoting peristalsis and having a laxative effect.
It will, if coffee is taken in excess, cause digestive
disturbances, as will also the caffeo- tannic add. The
latter, if much is present in the coffee, retards diges-
tion and absorption. It does not, as does the tannic
add of tea, predpitate alkaloids, albumin, and gelatin;
therefore, coffee is useless as an antidote for poisoning
by drugs the active prindples of which are alkaloids.
As caffein stimulates the respiratory center, coffee is
often used as an antidote for poisoning by drugs,
such as opium, which depress it. Also, as caffein
stimulates the vaso-constrictor and motor centers,
coffee is sometimes used to counteract the conditions
present in collapse, espedally that produced by over-
doses of drugs which depress the nervous system, as
the narcotics, anesthetics, and alcohol.

Caffein— -Free Coffees

' There are some coffees from which, by heating the

I berries tmder spedal conditions, much of the caffein

i has been removed. Some of these contain as little

as 0.3 per cent, caffein, but it is doubtful if any of
i them are actually free from it, as the name implies.

It is claimed that the other ingredientsof these coffees

are not altered by the treatment.

Coffee Substitutes

There are various preparations on the market that
consist prindpally of such substances as parched
com, baked wheat, dried peas, bread crust, and the
like, which are called coffee substitutes. Many of them,
however, contain a considerable amotmt of coffee.

330 Physics and Chemistry

Tea

Tea is made from thea, an evergreen shrub grown
chiefly in India, Ceylon, China, and Japan. The
finest qualities are made from the young, tender
leaves. The chief difference between black and green
teas is the smaller amount of tannin in the former.
This difference is due to the manner in which the
leaves are cured, those for black tea being allowed to
undergo a certain amount of fermentation before
they are dried.

The chief teas from India and Ceylon are Flowery
Pekoe, Orange Pekoe, Pekoe — ^these are made from
the smaller leaves; Souchong, Congou, and Bohea —
made from the larger leaves. The principal China
teas are Young Hyson and Gunpowder, which are
made from the smaller leaves, and Imperial and Twan-
kay, made from the larger leaves. These are green
teas. Various teas are often blended and different
blends are known by different names. English break'
fast tea, for example, consists of a mixture of teas.

The principal constituents of tea. — ^These are: i
to 4 per cent, caffein, 0.6 per cent, volatile oil — to
which the aroma and flavor are due, — and a large
amount of tannic add. Tannic acid precipitates
gelatin, albumins, and alkaloids and is strongly astrin-
gent. Due to the action of tannic acid upon alka-
loids, a strong infusion of tea is useful as an antidote
in poisoning by alkaloids; due to the astringency of
tannic add, strong infusions of tea will retard digestion
by inhibiting the flow of digestive juices. If tea is
not boiled nor the water allowed to remain more than
two or three minutes on the leaves, there will not be
much tannic add in the infusion, but, infusions strong

Nutritive Value of Foods 331

enough to tan hide into leather can be made from
tea.

Tea contains more caffein than coffee, but, as less
of the tea is used per cup, a cup of tea will not contain
as much caffein as a cup of coffee. Tea, however,
has a more immediate stimulating effect, either be-
cause of the nature of its volatile oil or because its
absorption is more rapid. If tea is taken in excess
or if it is made in a manner to extract a large amount
of tannic add, it will have more injurious effects upon
digestion than coffee, owing to the astringent nattu'e
of the tannic add, but, on the other hand, if it is
properly made, tea, probably because it contains
less extractive matter, is less disttu'bing to the
stomach.

Ndther tea nor coffee is nutritive in itself, but
the addition of cream and sugar gives them a slight
food value. The tannic add of the tea predpi-
tates the coagulable protdn of the milk, but this
does not interfere with its digestion by the gastric
juice; in fact, it is thought that milk or cream may
be desirable additions in that they lessen the irritating
action of the add in the stomach and retard the
.absorption of caffein.

Chocolate '

Chocolate is made from the ripe seeds of the bean
of the theohfoma cacao, a plant which is now grown
in many tropical countries. The seeds are fermented,
dried, roasted, and deprived of their shells, which are
known as cocoa nibs.

Chocolate contains from 0.3 to 2 per cent, of theo-
bromin, lo per cent, of starch, 15 per cent, of vege-

332 Physics and Chemistry

table protein, and 30 to 50 per cent, of a fat which is
known as cocclo or cocoa butter. There is some
tannic acid in the seeds, but this is removed in the
fermentation process. The chocolate flavor is de-
veloped in the roasting. This flavor is not pleasant,
but is made so by the addition of sugar to the choco-
late and, as a rule, vanilla or some other flavoring
extract.

As shown by the list of its constituents, chocolate,
unlike tea and coffee, is nutritious in itself, but, in
the stomach, the fat retards both the secretion of the
gastric juice and the motor action of the stomach, so
that chocolate should not be eaten or drunk in large
quantities and it does not make a suitable beverage
for invalids.

Theobromin stimulates both the cardiac and volun-
tary muscles, but has no action, like caffein, on the
vaso-constrictor centers and but little stimulating
effect upon the brain.

Cocoa

Cocoa is a powder prepared from chocolate by the
removal of a portion of its fat by hydraulic pressure.
Thus, cocoa contains a smaller per cent, of fat than
chocolate (it has 15 to 30 per cent.) and a larger per
cent, of theobromin. Considerable extra starch is
often mixed with the cocoas sold cheaply and in such
cases the percentages of both fat and theobromin are
reduced.

When preparing cocoa to drink, it should be cooked
for at least five minutes to hydrolize the starch. When
made with milk and sweetened with sugar, a cup of
cocoa will yield about 250 calories. Thus it has a

Nutritive Value of Foods 333

comparatively high food value for a beverage and
it is slightly stimtilating, but, even though it has
less fat than chocolate, it sometimes interferes with
digestion; especially in the case of invalids and of
children.

Coco-Cola

Coco-cola is a proprietary preparation that has
recently come into use. When it was first put upon
the market, it was reported to contain cocaine, but
investigation proved the report untrue. The chief
constituents are flavoring compounds and caffein. Its
action is therefore similar to that of tea and coSee.

Mineral and Carbonated Waters

As stated on page 209, in certain localities the soil
and rocks contain so much soluble mineral matter
that water flowing through the district absorbs enough
of the mineral to give it a decided flavor.

There is so much demand for such waters that they
are now bottled at the places where the springs occur
and put upon the market.

Both mineral and ordinary drinking waters are
oft^n charged with carbon dioxid gas. The carbon
dioxid used for the purpose is obtained from various
sotu'ces. Some of these are: (i) Many of the mineral
waters in their natural state contain carbon dioxid,
and this is taken from the water at the springs where
it arises from the ground, compressed in cylinders,
and then used to charge the water when the latter is
bottled. (2) Burning some form of carbon, as coke
or charcoal. (3) Collecting the by-product (CO a)

334 Physics and Chemistry

that occurs in the manufacture of lime from calcium
carbonate and that arising during the brewing of beer
and other fermentative processes.

Unfermented Beverages Made from Fruit Juices

Agreeable and wholesome beverages are prepared
by extracting the juice from fruit, sterilizing it, and
bottling it in sterile, air-tight bottles.

Fruit syrups are made in the same way plus the
addition of sugar before the sterilization. S

Imitation fruit syrups are made by combining sugars
or saccharin, artificial coloring matter, fruit acids
(e, g., tartaric, citric, phosphoric), and flavoring sub-
stances prepared from such compounds as chloroform,
nitrous ether, benzoic ether, butyric ether, etc., these,
when in special combinations, having somewhat the
same flavor as the delicate ethers and aldehydes to
which the flavor of fruit is due. The syrups used at
soda fountains are often the imitation products.

Fruit vinegars are other common flavoring sub-
stances used for beverages. They are made in about
the same way as the fruit juices, except that the fruit
is soaked in vinegar before the juice is extracted and
this vinegar is used as well as the juice.

Alcoholic Beverages

The alcoholic beverages in common use are made
byfermenting sugarsolutionswith yeast in the presence
of nitrogenous substances. The sugar may be that of
a fruit juice, or that produced by the action of the
yeast, or ferments secured from other sources, on
starch or cellulose.

Nutritive Value of Foods 335

Alcoholic beverages are usually classed as: wines,
distilled liquors or spirits, elixirs, malt liquors.

Wines

Wines are spoken of as red, white, dry, sweet,
strong, light, sparkling, fortified.

Red wines are prepared by fermenting the juice of
grapes in the presence of their skins. They contain
tannic add and are therefore more astringent than
white wines.

White wines are made from the juice of grapes the
skins and seeds of which have been removed.

A sweet wine is one that contains free sugar.

A dry wine, one that contains no free sugar, e. g.,
sherry.

A sparkling wine is one that contains CO 2, e. g.,
champagne.

A light wine is one that has a low per cent, of alcohol,
and a strong or heavy wine is one that contains a com-
paratively large amount of alcohol, but not above
17 per cent., while a fortified wine is one that contains
a higher per cent, of alcohol than 17 per cent. Since
the action of yeast is inhibited when 15 to 17 per cent
of alcohol is produced in the fermenting material,
to obtain a beverage containing more than 17 per
cent, alcohol, the alcohol must be distilled from the
fermenting material by fractional distillation — ^as
described on page 63 — or else, as is done in the making
of fortified wines, alcohol obtained by distillation must
be added. Light wines, such as claret and sauteme,
contain about 7 to 12 per cent, alcohol. Fortified
wines, such as madeira, sherry, and port, contain about
17 to 25 per cent, alcohol.

336 Physics and Chemistry

Apple and pear cider and similar beverages are
often classed with wines since they are prepared by
the fermentation of fruit sugar. They usually con-
tain from 0.50 to I per cent, alcohol.

Distilled Liquors or Spirits

These are made by distilling different kinds of fer-
mented liquors. Examples are : whiskey, gin, brandy,
and rum.

Whiskey {spiritus frumenti) is prepared by distil-
ling the mash of fermented grain, such as com, rye,
wheat, barley. To be good, whiskey must be not less
than four years old. It contains 44 to 55 per cent,
by volume of ethyl alcohol.

Gin, sometimes called compound spirits of juniper ^
is made by redistilling the distillate obtained in making
whiskey with juniper berries. It contains from 60
to 70 per cent, alcohol and some volatile oil of juniper
berries. The latter gives it diuretic properties.

Brandy (spiritus vini gallici) is obtained by the
distillation of the fermented juice of grapes. It con-
tains 46 to 55 per cent, by volume of ethyl alcohol.

Rum is the distillate from fermented molasses. It
varies in strength, but usually contains from 45 to
55 per cent, alcohol.

The Elixirs

These are aromatic alcoholic mixtures containing
varying, but large, percentages of alcohol, flavoring
substances, and sugar. Elixirs are often colored red,
blue, yellow, or green with vegetable colors.

The elixirs include the various liqueurs, cordials,

Nutritive Value of Foods 337

crimes, etc. Some of the best known beverages of this
class are: Absinth, which is prepared from spirit
flavored with wormwood and various aromatic sub-
stances and colored green with extracts from the
green leaves of wormwood, hyssop, and mint. Char-
treusei made from alcohol distilled with angelica^
hyssop, nutmeg, and similar substances. Cr&ne de
menthei made by distilling a fermented decoction of
mint, cinnamon, sage, and other spices; it is sweetened
with sugar and colored with chlorophyl. Curasao,
made by macerating and distilling the dried peel of
a variety of orange that grows in Curasao (Dutch
West India Islands) with alcohol. Maraschino —
genuine maraschino is made from Marasca cherries
which are crushed with their pits, mixed with honey,
fermented and distilled, but much of that sold is made
by distilling the products obtained by crushing and
macerating peach pits, wild cherries, cherry leaves,
orris root, and other flavoring substances with alcohol.
Vermouth, made in France and Italy from white
wines and various flavoring extracts.

Malt Liquors

The malt liquors are made from starchy substances,
usually grain. The grain is ground and boiled with
water; barley malt is added after the mash has been
reduced to the desired temperature, and as the barley
contains the ferment diastase, it changes the starch
to dextrin and some of the dextrin to maltose and
glucose. Hops also are added and they yield a
bitter principle and hypnotic substance to the liquid.
When this part of the process is completed, the liquid
is removed by filtration and yeast is added to the

33^ Physics and Chemistry

filtrate. After the fermentation caused by the yeast
has been carried to the desired degree, the yeast is
killed by heat. As the fermentation is always stopped
before all the sugars are destroyed, the malt liquors
contain varying amounts of free sugar. Also, they
contain the various products of the fermentation of
sugars, viz., alcohol (3 to 7 per cent.), adds and carboq
dioxid, and the bitter principle derived from the hops.

The principal malt liquors are ale, beer, porter, and
stout. The ordinary varieties of ale and beer are
very similar; the slight difference that exists being
due chiefly to the different yeasts that are used: beer
being fermented by bottom yeast (yeast that sinks),
and ale by top yeast (yeast which floats). True
lager beer — so called from the German lager ^ a store-
house — is beer that is stored in a cool place for several
months before use. Porter and stout are ales of
which the malt, before it was fermented, was roasted
until it changed to caramel. Stout is the richer and
stronger of the two.

Beers and ales made from xoots, herbs, etc. — Such
beverages usually consist of sugar solutions flavored
with essences consisting of extracts from special roots,
etc. (as ginger, sarsaparilla), and fermented with
yeast. They contain about i per cent, alcohol.

Action of alcohol on the system. — ^Alcohol depresses
the higher brain centers, /. «., those controlling reason-
ing, judgment, etc., but, unless the alcohol is taken in
large amotmts, the centers concerned with imagina-
tion, emotion, etc., are not particularly depressed,
especially when the drinker is where there are bright
lights and congenial company; in fact, the depression
of the higher centers often allows the others freer
play. This effect is more pronoimced when gas-con-

Nutritive Value of Foods 339

taining beverages, as champagne, are used, on account
of the stimulating effect of the CO,. But if alcoholic
beverages are taken in excess, and sometimes even
when taken in small amoimts in the absence of com-
pany or other stimulant, they are narcotic. From
the depression of the cerebrum by alcohol, after heavy
drinking, sexual desires are less under restraint than
usual, hence alcohol has been always an important
factor in the whiteslave trade. Alcohol depresses
the vaso-constrictor centers and, consequently, it
causes the blood-vessels in the skin to become dilated;
thus small doses may temporarily improve the super-
ficial circulation and lessen internal congestion.
Large doses of alcohol, however, depress this and
centers regulating other vital activities to such an
extent that, if the depression is constantly repeated,
harmful changes will be caused in the body tissues
which vnil interfere with the proper fimctioning of
the body organs and result in mental deterioration.
Alcoholic beverages, by stimulating the taste-buds
and olfactory nerves act as appetizers and induce a
psychic secretion of digestive juices. Beverages
containing less than 20 per cent, alcohol do not seem
to affect the digestive ferments, and they hasten the
absorption of other substances, such as digestive
products, water, and drugs, but vStrong solutions will
precipitate the proteins of food and, to some extent,
the pepsin of the gastric juice, and they retard diges-
tion; also, they tend to produce a coat of thick mucus
on the mucous membrane of the stomach which
interferes with absorption.

As to whether alcohol is to be considered a food or
not is still an unsettled question. An accepted defini-
tion of a food is a substance whose dominant property

340 Physics and Chemistry

in the body is to build up the tissues or to yield energy,
and though every gram of alcohol oxidized in the
body will yield 7 calories, this can be hardly called
its dominant property. Also, experiments have
shown that, though alcohol is easily oxidized in the
body and thus spares food products and body tissue
from oxidation, it is not used in the body for tissue
building. The malt beverages and others containing
sugar have, of course, a real food value on account of
their sugar. This sugar, however, is particularly
likely to undergo fermentation in the stomach and
cause flatulence.

Food maUruila (u punhued]

'Chuck iib>...
FUnk

Nwk

. Bib*

Rib roll*...

Hind qnuMr...
' Reprinted fr

18.7

Per Fer Per

Aih

S.1

Per
IS.O

JO. 3

i.i

•a

Ptr

'i
■9

■9

-I

1.1 OS

;;i
'•i
'■rs

cnmi, divida tbt Searm

n Panntri- BtiOttin. Ho.

|To Iraiulate tha psTceiiUgBi given in tb
nprcHntiog the pcrcent>aei by loo ((. i
toward the left), uid to find the amonnt of heat (caloriee) that each food inll
yield, multiply the number of ■rami of protein by 4. of fat by p. and of carLo-
hydtatei by 4. To find the amount oC protein, fat. etc. in one ounce, multiply
the number of tnioi of protein, etc., by it.ss (which ii tha number of gnun* la
one ounce), and to find the amount in one ponitd, nuUtiply by 413.60.)

Nutritive Value of Foods 341

AVERAGE CX)MPOSmON OP COMMON AMERICAN POOD

PRODUCTS— C<m/»»««rf

Food materials (as purchased)

ANIMAL FOOD — Continued

Beef, corned, canned, pickled, and
dried:

Corned beef

Tongue, pickled

Dried, salted, and smoked . .

Canned boiled beef

Canned corned beef

Veal:

Breast

Leg

Leg cutlets

Fore quarter

Hind quarter

Mutton:

Flank

Le^, hind

I^om chops.

Fore quarter

Hind quarter, without tallow
Lamb:

Breast

Leg, hind..

Pork, fresh:

Ham

Loin chops

Shoulder

Tenderloin

Pork, salted, cured, and pickled:

Ham. smoked

Shoulder, smoked

Salt pork

Bacon, smoked

Sausage:

Bologna

Pork

Frankfort

Soups:

Celery, cream of

Beef..

Meat stew

Tomato

POultZTT

Chicken* broilers

Fowls

Goose

Turkey..

Pish:

Cod. dressed

Halibut, steaks or sections. .

Mackerel, whole

Perch, yellow, dreMed.

Shad, whole

Shad, roe •....

Pish, preserved :
Cod, salt

Refuse

Per
cent.

8.4
6.0
4.7

3X.3

14.2

3.4

24. S
20.7

9.9
18.4
16.0
21.2
17.2

X9.X
17.4

10.7
19.7
12.4

13-6

Z3.2

7.7
3.3

4X.6

25.9
Z7.6
22.7

39.0
17.7
44-7
35-1
50.x

34*9

Water

Ptr
cenL

49*3
58.9
53-7
SZ.8
5X.8

2.0

o.x

68.3
54.2
56.2

39.0

5X.2
42.0

4X.6

45-4

45.5
52.9

48.0
41.8

34.8
36.8

7.9
17.4

55.2
39.8
57.2

88.6
93.9
84.S
90.0

43.7
47.1
38.S
42.4

58-5
61.9
40.4
50.7
35-3
7X.2

40.S
19^

Pro-
tein

Per
cent.

14.3
11.9
26.4
25.5
36.3

15.4
15.5
20.1
Z5.X

X6.2

X3.8

15.1

13.S
Z2.3
13.8

15.4
I5«9

13.5
X3.4

X2.0

Z8.9

X4.2
X3>0

1.9
9.1

X8.2
X3*0

I9'6

a.x

4.4

4.6
1.8

Z2.8

13.7

xj-4
x6.x

xx.i
15.3

X0.2
12.8

9.4

ao.9
x6.o

Fat

Per
cent.

23.8

X9'2

6.9
22.5
X8.7

ix.o
7.9

6.0
6.6

36.9
X4-7
28.3
24-S
23.2

X9«x
13*6

35.9
24.2
29.8
X3'0

33-4
26.6
86.2
62.2

X9.7
44.2
X8.6

2.8

.4
4-3
I.X

X.4
12.3
29.8
X8.4

4-4
4.2

4.8
3.8

Per

eeuL

X.I

z.x

SO
x.z

5.5
5.6

3.6

Ash

Per
cent.

4.6

8.9

Z.3
4.0

.8
.9

Z.0

.7
.8

.6
.8
.7
.7

.8
•9

.8
.8

.7
Z.0

4.2
5.5
3.9
4-1

3.8
3.2
3.4

1.5

X.2
Z.X

z>5

.7
.7
.7
.8

.8
.9
.7
•9
.7
1.5

Z8.5

Fuel

value

per

pound

Co/o-
rin

1.345

x.oxo

790

x.4 10
Z,270

745
62i

69s
53S
580

X,770

890

X.415

X.23S

1,2X0
I.07S

860

1.320
1.24s

X.dSO
89s

z,635
X.335
3.S5S
3,7x5

1.15s
3.07S
Z.X55

335

X20
365

x8s

305
76s

1.475
z,o6o

330

475
370

27S

335

755

342

Physics and Chemistry

AVERAGE CX)MPOSmON OF COMMON AMERICAN POOD

FRODXJCTS— Continued

Pood matertalt (m purchased)

A^fiMAL FOOD — CofUinuH

Fiah, canned:

Salmon. ••.. ,

Sardinei

Shellfish:

Oysten. *'aolid8*'

Claxnt ,

Crabi

Lobetert ,

Egga: Hens' eggs

Dairy products, etc:

Butter

Whole milk ,

Skim milk

Buttermilk ,

Condensed milk

Cream

Cheese, Cheddar. .......

Cheese, full cream

Refuse

Per

ceiU.

45.0

52.4
61.7

hii,2

ji<

roller

VBGBTABLB VOOD

Flour, meal, etc.:

fintire-wheat flour. . •

Graham flour

Wheat flour, patent
process —
High-grade and medium
IiOw<^rade

Macaroni, vermicdli, etc . . .

Wheat breakfast food

Buckwheat flour

Rye flour

Com meal

Oat breakfast food

Rice

Tapioca

Starch

Bread, pastry, etc.

White bread

Brown bread ,

Graham bread ,

Whole-wheat bread,

Rye bread ,

Cake

Cream crackers. . . . ,
Oyster crackers. . . • .
Sodacrackara ,

Sugars, etc:

Moliisos •....••<

Candy < ,

Honey

Sugar granulated.
Maple airup

Water

Ptr
eenL

63.5
53-0

88.$

80.8
36.7
30.7

6S.5

ZI.0
87.0
90.S
9t.o
36.9
74.0

27.4
34-a

XI.4
ZZ.3

Z3.0
1 3.0
10.3
9.0
X3.6
13.9
13.5

7.7
Z2.3
II.4

35-3
43.6

3S.7

38.4

35.7

X9.9

6.8

4.8

S'9

Pro-
tein

ctnL

31.8

33.7

6.0

Z0.6

7.9

5.9

Z3*X

z.o
3.3

3-4
3.0
8.8
3.5
37.7
25.9

13-8
X3.3

XZ.4
X4.0

X3.4

X3.X
6.4

6.8

9.3

Z6.7

8.0

-A

Bat

9.3

5.4
8.9

P-7
9.0

6.3

9.7
ZX.3

9.8

Pgr
cent.

X3.X
X3.X

X.3
z.x

.9
.7

9.3

85.0

4.0

8.3

X8.5

36.8

33.7

X.9
3.3

Z.O
1.9

Z.8

Z.3

x.9

7.3

•3

z.8

9.0

X3.X
XO.5

9*x

3.3

5.3

5.0

5.x

4.8
54.x
4-5
4.1
8.4

7X.9
71.4

7S.X

7X.3

74.x
75.2
77.9
78.7

211

88.0
90.0

53.x
47.x
53.Z
49.7
53.a
63.3
69-7
70.5
73.x

70.0

?6.o
x.o

X00.0

7x^

Ash

Per
cenL

3.6
5.3

i.x
3.3

•i

0.9

x.9

4.0

3-8

x.o
z.8

x.3

Z.O

3.1

-A
.z

Fuel
value

per

pound

z.z

3.Z

X.5

x.3
X.5

x.5
X.7
3.9

3.x

Calo-
fin

9x5
950

335

340

300

X45
635

3.4x0
3x0

x6o
x,430

865
3,075
I.88S

.650
.645

t635
.640

:Sa

,6oj
,630

.635
.800

.630
.6so
.67s

,300
.040

.195
.X30
.X70
.630

.935
,910

.875

.680
.420
•750

« Refuse, oiL h Bafnew iML c Flaia ooaftetltMiy aot *^t* 'Ttfirf »«%

Nutritive Value of Foods 343

AVERAGE COMPOSITION OP COMMON AMERICAN FOOD

VRODVCrrS—CtmHnued

Food material! (as pmchaaed)

VEGETABLE FOOD — Cotltintud

Vegetables a:

Beans, dried

Beans, Lima, shelled

Beans, string

Beets

Cabbage

Celery

Com, green (sweet), edible
portion

Cucttmbers

Lettttce

Mushrooms.

Onions

Parsnips

Peas (PisuM sativum), dried .

Peas {Pimm satifum), shelled

Cowpeas, dried

Potatoes

Rhubarb

Sweet potatoes

Spinach

Squash

Tomatoes

Turnips

Vegetables, canned:

Baked beans

Peas {Pisum sativum), green

Corn, green

Succotash

Tomatoes

Fruits, berries, etc., fresh b :

Apples

Bananas. •

Grapes.

Lemons

Mttskmelons

Oranges

Pean

Persimmons, edible portion.

Raspberries.

Refuse

Per
cenU

7.0
ao.o
15*0
ao.0

15-0
15*0

10.0
20.0

20.0

40.0

30.0

50.0

30.0

3$.0
35-0
25-0

30.0
50.0
37.0

10.0

Water

Per
eenL

X2.6

68.5
83.0
70.0

77.7
7S.6

75.4
ox.i
80.5
88.x

78.9
66.4

^1
74.0

Z3>o

63.6

56.6

55.2

93.3

44.2

94.3

62.7

68.9

83.3
76.1

75-9
94.0

63.3
48.9
58.0
62.5
44.8

63.4
76.0
66.x
85.8

Pro-
tein

Per
eenL,

22.5
7.x
2.1
x.x

1.4
.9

3.x

x.o

3-5
1.4
1.3

24.6
7.0

2X.4
X.8

1.4
2.1

• I
•9
.9

6.9
3.6
3.8
3.6
Z.2

0.3

1.0

.3
.6

.5
.8

X.o

Fat

x.8

•x
.2

x.x

•4

X.o

•5

1.4

.4
.Z

2.5

.2
X.3

X.o

0.3

.4
X.3

•5

.X
•4

Per Per
cent, eenL

Ash

59.6

22.0

6.9

7.7
4.8
2.6

19.7

2.6

2.5

6.8

8.0

X0.8

63.0

Z6.9

60.8

X4.7
2.3

2X.9

3.2
4.5
3.9
5.7

X9.6

9.8

I9'0

X8.6

4.0

X0.8

X4.3

X4.4

5.9

4.6

8.5
12.7

3x0
12.6

Per
eenL

3.5

X.7

X.2

.5
X.x

2.9
x.o

3-4
.8

•9

2.x

•X

2.x

X.X

•4
.4
•3
-A
.4
.9
.6

Fuel
value

pound

CetO'
Ties

Z.530
540
X70
z6o
xx$

6s
440

65
X8S
Z90
230

1.S65
440

t.505

29s

440

9$
xoo
xoo

X20

555

235
430

42s
»s

200
295

X2S

80
X50
23A
550

220

a Such vegetables as jwtatoes, squash, beets, etc, have a certain amount of
inedible material, skin, seeds, etc The amount varies with the method of pre-
paring the vegetables, and cannot be accurately estimated. The figures given
for refuse of vegetables, fruits, etc, are assumed to represent approximately
the amount of refuse in these foods as ordinarily prepared.

h Fruits contain a certain proportion of inedible materials, as skin, seedst
etc., which are properly classed as refuse. In some fruits, as oranges and prunes*
the amount rejected in eating is practically the same as refuse. In others, as
Apples and pears, more or less of the edtble material is ordinarily rejected with
the skin and seeds and other inedible portions. The edible material which
is thus thrown away, and should propwly be dassed with the waste* is hers
classed with the refuse. The figures for refuse here given rsprssSBtt M assdlT
iw CM bs MOfftainsd* tbs nnsiititlw ofdimiily ndsctod*

344 Physics and Chemistry

AVERAGE COMPOSITION OF COMMON AMERICAN FOOD

PRODUCTS— CtmiwMiI

tlHd.

t Milk ind *hdl.
c The iTBraEB of fln ■lulria of cereal coffee grain il: Water 6.1, pr
bt 3.4. carbohTdntM 71.6, and ath 4.5 per cent. Onl)' a portios of
anti, honnT, cnten iato tb* iotoiloii. The aTvms* ta
available nntticou in tht bereracB. Inlndona of canulne Coffee
Ilka (be abore eoiuaia

IUf<»e

W.ter

Pro-

Pat

A*h

valna

ncRAKa noo-CmNitaad
Fmiw. bemra.. etc, fmh •:

Ptr
etiu.

S9.*

■5.»

37-S

ia.i

37-»

(CDt.

■9

4-7

Tf
li;

S:S

;:i

S-!>

30.»

3J'7
S.3

J7.4

4B.T
J8.9

Ptr
ctM.

66.1

11
!:|

lis

30J

P<r
3.1

«!o

■4
1-7

A
'i

?2r
■g

i.iif

!-;iS

'"'S'oriS^'

feM»

10.0

Hum:

>.m!

111

51:!

||™^P0li*h«l

'••^BtT.::::::::::

bailedinioiiaru*BtST)c

CHAPTER XX

THE CHEMISTRY OF COOKING

The Action of Heat, Adds, and Sodium Chlorid on Protein-
Solubilities of Proteins — The Changes Caused in Meats by
Cooking — ^The Action of Heat and Acids on Starches and
Sugars — Solubilities of the Carbohydrates of Food — Com-
parative Thickening Power of Different Starches — Methods
of Making Doughs and Batters Light — ^The Nature and
Action of Pectin.

A KNOWLEDGE of some of the more important
chemical and physical changes that occur in food as
the result of cooking is a valuable aid in preventing
mistakes which greatly lessen the digestibility of food
and, consequently, its nutritive value; for food is of
no use to the body until it has been absorbed and it
cannot be absorbed until it has been digested. Also,
as will be seen in the following pages, mistakes in
cooking entail a loss of food in other ways.

The Effect of Heat, Acids, and Sodium Chlorid on

Protein

Experiment 42. Object: (a) To discover the tem-
peratures at which the albumin of milk and egg^ the
vitellin of egg, and the proteins of meat coagulate;
(b) to see the difference in the nature of egg-white
when it is coagulated slowly and rapidly.

345

346 Physics and Chemistry

Procedure: (a) Into separate large test-tubes put (i)
milk, (2) egg-white, (3) egg-yolk, (4) a few small pieces
of meat, and about 10 c. c. of water to keep the meat
from sticking and hardening to the glass. Place the
four tubes in a beaker of water and set this over a low
flame. Watch carefully and test the temperature of the
contents of each tube as soon as it begins to coagu-
late and every few minutes as coagulation increases.
Notice particularly the difference in the temperature
and the time required for the coagulation of the white
and yolk of the egg.

(b) Pour some egg-white into a beaker yi full of
boiling water and let this boil for three minutes. Put
some egg-white into a test tube, stand this in a beaker
containing cold water, and bring this slowly, taking
ten minutes to do so, to boiling temperature. Com-
pare the nature of the two coagula.

How would you cook a so-called sqfl-baUed egg?

How would you poach an egg?

Experiment 43. Object: To test the effect of salt
and organic acids on coagulation.

Procedtu^: Into each of seven test tubes put about
3 c. c. of egg-white. To tube 4 add J^ c. c. of 10%
NaCl solution; to tube 5 add i. c. c. of 10% NaCl
solution; to tube 6 add i drop of acetic add 1%;
to tube 7 add 5 drops of acetic add 1%. Put the
seven tubes into a water bath and keep the water just
below boiling point for five minutes. (Notice the
difference in the toughness of the egg heated alone
and that of the egg to which the add and the salt
were added.) At the end of five minutes add: To
tube I, 2 drops of 1% acetic add; to tube 2, J4 c. c.
of 10% NaCl solution; to tube 3, i c. c. of 10% NaCl;
to tube 4, 2 drops of 1% acetic add; to tube 5, 2

The Chemistry of Cooking 347

drops of 1% acetic acid; to tube 6, i c. c. of 10%
NaCl and the same to tube 7. Replace the tubes
in the water bath and leave them for five minutes.
Watch their contents carefully to detect the changes
that occur.

As the result of these experiments, state your opin-
ion as to the desirability of adding salt to the water
in which eggs are cooked.

Would you recommend the addition of vinegar to
the water?

Would acid, as vinegar or lemon juice, poured over
tough meat have any desirable effect?

Will salt rubbed over the surface of meat before
roasting help to retain the extractives in the meat?
Why? (If in doubt of the correct answer, put a few
small pieces of raw meat into a beaker containing
water and let this stand for half an hour or more and,
in a second beaker, do likewise with some meat you
have heated until the outside has been well browned.
Judging from the color of the water in the two beakers,
decide whether coagulating the protein on the out-
side of the meat tends to retain the extractives.)

What will be the result of cooking eggs and meat at
a high temperature?

From these experiments, it can be seen that if
protein is heated in a slightly acid solution or a neutral
salt solution, coagulation is accelerated, but that
larger amounts of acids (and the same is true of
alkalies} prevent coagulation.

Result of cooking on the protein of meat — ^Both
dry and moist heat coagulate the proteins of meat and
thus harden its tissue, but moist heat disintegrates
the fibers and softens the connective tissue and thtis
tenders the meat easier to masticate. Thus, cuts of

348 Physics and Chemistry

meat that would be very tough if broiled or roasted
can be made tender by cooking them in water at a
temperature slightly below boiling point. Searing
the outside of meat by exposure to a high temperature
will prevent the escape of extractive; but, if the high
temperature is maintained, the meat will be toughened,
and, if the surface of the meat is hardened, the heat
will not penetrate. It has been found that roasts are
as quickly — ^and much more uniformly — cooked at
175^ C. as at 200® C.

Solubilities of some of the common food proteins.
— These are as follows:

Albumins are soluble in water, dilute acids, dilute
alkalies, and sodium chlorid solutions.

Globulins also are soluble in dilute add, alkali, and
neutral salt solutions, but insoluble in concentrated
sodium chlorid solutions and in water.

CaseinogeUi the important phosphoprotein of milk,
is insoluble in water, dilute acids, and salts, but dis-
solves in alkalies to form a salt-like body. It is pre-
cipitated by dilute acids, but dissolves in strong adds.
It does not coagulate on boiling. It is clotted by
rennin. This is due to the conversion of the case-
inogen into an insoluble protdn called casein. The
calcitmi salts of the milk are necessary for this change
as was seen by Experiment 40.

The curd that forms when the rennin acts upon the
caseinogen entangles the greater part of the fat of the
milk so that the fluid portion which separates from
the curd — ^the whey — contains only the salts, lactose,
and lactalbumin. The presence of fat in the milk
rather interferes with the forming of a hard curd and,
therefore, when milk is curded in order to obtain
whey, it is imperative that skimmed milk be used.

The Chemistry of Cooking 349

Legumixii the chief protein of the legumes, combines
with the lime in hard water and is thus rendered very
insoluble. Consequently the legumes must be cooked
in soft water or else sodium bicarbonate must be
added to the water.

Gluten is insoluble in water, but one of its con-
stituents — ^glutenin — is soluble in very dilute acid
and alkaline solutions and the other constituent —
gliadin — is soluble in 70 per cent, alcohol.

Nucleoproteins are soluble in dilute alkaline so-
lutions, but insoluble in water and dilute salt and acid
solutions!

Gelatin is soluble in warm water and in warm acid,
alkaline, and salt solutions, but insoluble in all of these
liquids when cold.

Derived proteins and extractives are soluble in
water, dilute acid, alkaline, and salt solutions.

Mention all the practical applications you can
think of to which knowledge of the coagulation and
solubilities of proteins can be put in cooking and in
the cleaning of cooking utensils.

Are there more albumins or globulins in the meat?
(See page 270)

Why is the salt solution used for corning beef
concentrated?

How will you roast meat?

How will you make a stew?

How make broth?

Give reasons for all procedures.

Carbohydrates

Experiments 44 to 46. Object : To see which of the
common carbohydrates arc soluble in water and the

350 Physics and Chemistry

effect of letting vegetables such as potatoes stand in
water.

Experiment 44. Cut a portion of a firm potato
into thin strips and let these stand in a beaker of
water for at least half an hour. Do likewise with a
wilted potato (use a separate beaker). •

Experiment 45. Put a little bread into a beaker of
water and in a separate beaker a few strips of dry
toast and water.

Experiment 46. Put a few strips of cabbage in
(i) a beaker containing water, (2) a beaker containing
vinegar.

(Record the result of these experiments before
reading further.)

The white substance that collected in the bottom
of the beakers in which the pieces of potato stood is
starch; therefore Experiment 44 shows that starch is
insoluble in water, but that it will be extracted from
potatoes if they are allowed to stand for any length
of time in water. It will be noticed that the wilted
potato did not part with its starch to anything like
the extent that the firm one did and also that the
condition of the wilted potato was improved by
standing in water. Nearly all vegetables, soon after
they are gathered, lose water by evaporation; this
water must be replaced before the vegetable is cooked
or served, or it will be neither tender nor crisp.

Since such vegetables as potatoes lose starch while
in water, they must lose it diuing cooking and, as
shown in Experiment 45, the loss is greater as the starch
becomes dextrinized* by heat and when the carbo-
hydrate present is a sugar, as in parsnips, etc. There
will be less loss of nutrient from potatoes if they are

> The brown of the toast is dextrin.

The Chemistry of Cooking 351

cooked before they are peeled and, when baked, a
XX)tato loses practically none of its constituents except
water.

In Experiment 45, the water in which the bread
was soaked remained unclouded, but that in which the
toast stood very soon became colored, showing that
dextrin is soluble in water. That sugar is soluble
in water is seen too often to need demonstrating., ,

Experiment 46 shows the difference of the action
of water and acid on cellulose, the acid dissolving the
cellulose to a slight extent. This is why the addition
of vinegar to cabbage is thought to aid in its digestion.

To sunmiarize, celluloses and starches are insoluble
in water, dextrin and sugars are soluble.

Experiment 47. Object: To show the effect of
heat and water on starch.

Procedure: (a) Put i tablespoonful of starch or flotir
into a beaker and poiir over it i cup of boiling water.
Stir slightly. Put the beaker over the flame and boil
the contents for two or three minutes. Remove it
from the flame. Take out some of the larger lumps
and break them open.

Why was the interior of the Itmap so little affected
by the heat?

(fi) Repeat (a), but before adding the water, mix
thoroughly two tablespoonfuls of sugar with the
starch.

(d) Repeat (a), but mix the flour with melted butter
before adding the boiling water.

Why did not the starch lump in (6), (c), (d)?
Starch grains are enclosed in a comparatively soft
cellulose sac. This, when heated to boiling tempera*

352 Physics and Chemistry

ture, is softened, and the grains swell to many times
their original size, and, tmless they are well separated
from each other in some way as by cold water, sugar,
or fat, they will stick together, forming Itmips.
The grains of cereals that have a comparatively thick
cellulose sac can be prevented from lumping, even
though they are not mixed with sugar, etc., if the
water is boiling violently when the cereal is put into
it and kept boiling during the process, the bubbling
of the water preventing adhesion.

When a starch paste is made with water below
boiling temperature, the covering of the grain is un-
broken, though the grain swells considerably, and
when such a paste stands, the starch grains sink to
the bottom.

The comparative thickening power, transparencyi
and flavor of starches. — Some starch grains swell
much more than others and some will make a more
transparent paste and have a more delicate flavor than
others. This can be seen by the following experiment.

Experiment 48. Into separate beakers, put 2
grains of each of the following starches: Arrowroot,
corn, potato, rice and wheat starches, tapioca, dextrin.
To each add slowly, 40 c. c. of cold water, bring to
boiling point and boil for five minutes; stir con-
stantly. Compare the diflferent mixtures as to con-
sistency, clearness, and flavor. Boil the pastes for
five minutes longer and compare them again.

Which forms the clearest paste?

Of which paste is the flavor improved by the longer
cooking?

If, when following the directions of a recipe, you
substitute the starch specified for another, will you
use the same quantity?

The Chemistry of Cooking 353

Which of the starches used has the greatest thick-
ening power and which the least?

Experiment 49. Object: To study the effect of
heat and heat plus acid on starch.

Procedure: Heat some starch in an evaporating
dish over a low flame until it browns, dissolve ^ of a
teaspoonful of this in water. Make a starch paste, us-
ing J^ teaspoonful of starch to J^ cup of water. Divide
this into two equal portions, (6) and (c). To (c) add
I c. c. of HCl and boil for ten minutes. Divide each
of these three mixtures into two portions and test
one with iodin and one with Fehling's solution. It
will be noticed that the amount of starch used in each
case is such that there will be an equal amount in
each of the mixtures tested with Fehling's. The
reason why this is necessary can be seen on page 398.
For the same reason, it is necessary that exactly the
same amount of Fehling's solution be used in each
case.

Into what was the starch changed by heat?

Into what was it changed by heat and add?

If unable to answer these questions, see page 398.

Experiment 50. Object : To show the effect of heat
and add on sugar.

Procedure: Make a sugar solution by dissolving one
teaspoonful of sugar in 30 c. c. of water. Divide this
into three equal portions. To the portion in tube i
add 5 c. c. of lemon juice; boU this and the solution
m tube 2 for fifteen minutes. Divide the three
solutions into two parts and test for cane sugar and
for glucose as described on page 294.

It will be seen that boiling reduces cane sugar to
glucose, but that the reduction is more quickly and
thoroughly accomplished when add is present. Glu*

354 Physics and Chemistry

cose, it will be remembered, it only about half as
sweet as cane sugar.

Why is sugar, when possible to avoid it^ not added
in cooking until the cooking is nearly completed,
especially when there is add in the food?

Will you need more sugar for a baked or for a
steamed custard?

Sugar heated without liquid will, at a temperature
of i6o® C. (320** P.). melt and form a brown mass,
known as caramel, which has a slightly bitter, but
agreeable flavor. Caramel dissolved in water, milk,
or other liquid is much used as a flavoring for confec-
tions and as a coloring matter for gravies and sauces.

Methods of Making Doughs and Batters Light

Doughs and batters are made light by one or other
of four methods; viz; :

(i) The introduction of air.

(2) The addition of volatile substances to the dough.

(3) The addition of substances to the dough which
will dissociate and thereby yield a volatile gas.

(4) The production of a volatile gas as the result
of fermentation.

In all four methods the essential facts depended
upon are (i) Air and gas are expanded by heat;
(2) that gluten is sticky and expansive and thus
serves to hold the air or gas until the heat sets the
dough in this porous state. The gas obtained from
baking powder and other combinations of acids and
alkalies and by the action of yeast is carbon dioxid.

Method I. Air is generally introduced into
doughs, etc., by one of the following ways: (a) By
beating and rolling the dough as when making paste;

The Chemistry of Cooking 355

in this process the dough is alternately rolled or
pounded and folded over so as to enclose air. The
butter, or other fat, by keeping the particles of flour
apart, helps to obtain this result, (b) The addition
of well-beaten eggs to batters. This is a very com-
mon method of introducing air, for especially the
white of egg, when beaten alone, will take in and
hold for a time a large amount of air. (c) Snow is
sometimes used as a means of getting air into batters,
because the snow cr3rstals contain considerable air.

When air is introduced into batters and doughs
in the ways just mentioned, the ingredients must be
mixed quickly and the substance cooked at once, for
the air will not be held very long as is shown by the
rapidity with which the beaten white of egg loses its
frothy condition on standing.

Method 2. (a) The most common eicample of the
use of this method is the addition of carbon dioxid
gas to dough. This is the way in which the aerated
breads, much used in England, are made light, (b)
The addition of an alcoholic liquor, as wine, to a
batter helps to make it light, because the heat of the
oven volatilizes and expands the alcohol.

Method 3. The substances generally used to
obtain carbon dioxid in dough in Method 3 are
sodium bicarbonate (baking soda) and an acid. The
acid is somettn^es obtained by the use of molasses,
which contains, some free add and acid salts, or sour
milk, which contains lactic add formed by the fer*
mentation of its lactose. When the lactic add unites
with the soda, the following reaction occurs:

BkSbZue ^^^^^ Sodium LaciaU

UkaObs + CaH«OCXX)H - CjH,OOOONa + HaO 4- COj

35^ : Physics and Chemistry

Baking powders axe the form in which soda and
acid are most commonly used. These consist of
sodium carbonate and add and starch, the starch
being used to prevent interaction of the other two
constituents before the powder is wanted for use»
should it become moist.

The acids commonly used in baking powders are
tartaric acid in the form of cream of tartar (potassium
bitartrate), phosphoric add, and alum.

Experiment 51. Object: To show the action of
baking powders.

Procedtu-e: (i) Mix J^ teaspoonful of soditun bicar-
bonate and I teaspoonful of cream of tartar in a small
beaker. In a second beaker, mix i teaspoonful of
sodium bicarbonate with 30 c. c. of cold water and
stir. In a third beaker, mix 2 teaspoonfuls of cream
of tartar and stir. Combine mixtures 2 and 3. What
happens? Heat the mixture.

Explain the experiment before reading the following
paragraphs.

The effervescence that occurs in Experiment 51 is
due to the liberation of carbon dioxid gas; bearing
this in mind and that water also is formed, state what
salt will be left in a batter when baking powder con-
taining sodium bicarbonate and cream of tartar is
used. What salt will be left when phosphoric acid
is used?

As shown by the first part of this experiment, no
reaction takes place between the alkali and the acid
80 long as these substances are dry, but as soon as
water is added the two combine as described in
Chapter XIV. For this reason, baking powders will
deteriorate if they are not kept in a dry place.

Another lesson to be learned from this experiment

The Chemistry of Cooking 357

is that chemical action soon ceases and, though the
presence of the various solid ingredients of the batter
prevent the action occurring and ceasing as quickly
as in the experiment, unless the batter is cooked as
soon as mixed, the gas will escape before the heat has
done its work and the cake, etc., will not be light and
porous.

Fate of substances formed in the reaction. — As
may be inferred from the preceding paragraphs, there
are three things formed in the chemical action between
the alkali and the acids used for the purpose under
discussion; viz., CO a, HaO, and a salt. The COa
and the HjO pass off during the heating, but the salt
remains in the food.

Action of salts in the body* — The Rochelle salts,
formed when a baking powder contains cream of
tartar and the sodium phosphate occurring when the
powder contains phosphoric acid, are laxative, but,
as they are present in only very small amounts, they
have little or no effect on the system. The alum salts
that remain when any alum preparation is used are
astringent, and it is thought that even in small amounts
alum may aggravate any tendency to constipation
if people eating food containing it are so troubled.

Experiment 52. A test to detect the presence of
alum in baking powder: Dissolve about a teaspoonful
of the powder in water, add to this an equal amount of
dilute (one-third the usual strength) tincture of log-
wood, and then add an equal volume of ammonium
carbonate solution. If altun is present, the liquid will
become a dark blue or lavender color.

Method 4. Yeast is the substance most commonly
used for the fourth method of making doughs, etc.,
Ught.

35^ Physics and Chemistry

J, Nature of yeast. — Yeasts are microscopic, one-
celled plants that multiply by budding (t. e., a small
bud or swelling appears on a cell which gradually
increases in size and finally splits ofiE). There is more
than one variety.

How obtained. — Yeasts are very prevalent in the
air and, in the olden days, dough was exposed to the
air until enough yeast entered it to cause fermenta-
tion. Also some of the fermented dough of one day*s
baking was often kept to act as a "starter" or
"leaven" for the next baking. One great objection
to these modes of getting yeast was that other micro-
organisms and yeasts with undesirable character*
istics entered the dough and frequently inte|:fered
with the action of the true yeast and, in this and other
ways, spoilt the dough. For this reason, cultivaled
yeasts are now much used; e. £., compressed and dried
yeasts.

Compressed yeast. — ^This is made by sowing puro
yeasts of a desired variety in vats containing material
upon which they will thrive. The yeasts grow quickly
and in a few hotirs collect in a sctun on the top of the
material. This is removed and pressed into cakes.
This is one of the best varieties of yeast when used
soon after it is prepared, but the cells die from lack
of nourishment.

Dried yeast cakes consist of cultivated yeast mixed
with other ingredients, chiefly starch, pressed into
shape and dried at a low temperature. The drying
may kill some of the cells, but, if the cakes are kept in
a dry, cool place, the majority of them will survive
for a long time. Warmth and dampness will cause
temporary activity of the yeast and consequent
souring of the cakes.

The Chemistry of Cooking 359

The brewers' yeast, often used by bakers, consists
of the scum which grows on the top of the matter
undergoing fermentation in the making of beer, etc.

Food required by yeast — In order that they may
grow well, yeasts must be given the kind of food that
they require. The principal thing that all the com-
mon species require is sugar. This must be in solu-
tion and not too concentrated, as is shown by the
fact that^fruit cooked in a large amount of sugar, as
in the making of jam, keeps better than that stewed
in a small quantity of sugar.

Action of yeast and cause of this action. — The yeast
plants secrete at least three enzymes, one of which
facilitates the change of starch to glucose thus:
CoHioOj+HaO— C6Hxa06; another causes the fer-
mentation of the glucose and thus changes it to
alcohol and carbon dioxid, thus: CeHuOd^sCjHj-
0H+2C0a, while the third facilitates the oxidation
of the alcohol which is thereby changed to carbon
dioxid and water. (Give the equation for this re-
action.)

It will be seen that in Method 4, as in Method 3,
carbon dioxid is the agent which causes the dough to
expand.

The addition to dough of sugar and of milk (on
account of its lactose) hastens the fermentation, for
the sugar provides nourishment for the yeast and
makes, it more active. For this reason, dried yeast
will act more quickly if soaked in sugar solution before
being used. The presence of potatoes and rye flour
in dough also seems to hasten (crmentation ; the reason
for this is thought to be that their soluble proteins
stimulate enzymic action.

The temperature at whidi dough is kept is of im-

360

Physics and Chemistry

portance. Yeast is most active between 70® F. and
90° F. and it is destroyed at a temperature of 131® F.
If dough is allowed to rise too long, adds will develop
from the alcohol (acetic acid), from the butter (butjoic
add)) and from the milk (lactic add), and thus the
dough will be sour. The same thing will happen if
the dough is kept at a temperature exceeding 90® F.,
because the yeast cannot then thrive well and add-
forming spedes of bacteria which can do so will
increase in number.

Experiment 53. Object: To determine the com-
parative fermentating pbwer of yeastsi
Procedure: Make a dilute mixture of flotir and

water. Fill the long
stems of three fer-
mentation tubes
with the mixture..
To one add about
A of a compressed
yeast cake dissolved
in lukewarm water;
to another add a
piece of equal size of
a dried yeast cake
likewise dissolved,
and to the third tube
add a little brewers*
yeast. Mix the con-
tents of each tube by
shaking the tubes,
see that all the mix-
ture is in the long
stem, plug the tubes, stand them in a warm place,
and leave them for twenty-four hours. Inspect them

Fig. 65.

(a) Liquid is in the long arm of
the tube. (6) Liquid has been forced
into the short arm by the gas.

The Chemistry of Cooking 361

from time to time. As gas is formed, it rises to the
top of the liquid and forces the latter down into the
short arm of a tube. Which yeast acted the quickest?

Experiment 54. Object: To see why sugar is added
to dough in bread-making.

Procedure: Make a flour-and-water mixture as for
the preceding experiment, di\4de it into two portions;
to one portion add about a teaspoonful of cane sugar»
to both add } of a cake of compressed yeast dissolved
in lukewarm water. Put these mixtures into fer-
mentation tubes as in the preceding experiment. In
which does fermentation first occur?

Fig. 66. Apparatus Areakgbd pot Bxpbszkbmt 55.

Experiment 55. Object: To prove that it is the
same gas (CO a) that is obtained by the use of baking
powder and yeast.

Articles required: 2 beakers* a test tube with a

362 Physics and Chemistry

one-hole cork to fit; glass tubing bent as in Pig. 66;
lime water, starch paste, yeast, baking powder,
water.

Procedure: Put some of the starch paste, plus y% of
an yeast cake dissolved in lukewarm water, into a test
tube and lime water into the beaker. Arrange the
apparatus as in Fig. 66 and put it in a warm place.
Notice the condition of the lime water after twenty-
four hours. Put some baking powder in another test
tube, some lime water in a beaker, and connect the
apparatus as in Fig. 66. Then add some water to the
baking powder.

Does the lime water assume the same appearance
in the two beakers?

What gas causes the change in the lime water?

What does it form in the lime water?

Write the equation.

Pectin

As previously stated (page 291) pectin is present,
though in very varying amounts, in nearly all fruit
and in some vegetables. There is usually a larger
amount present before fruit is fully ripe than later,
and better jelly will therefore be made if part of the
fruit used for the purpose is not quite ripe, but, as
ripening improves the flavor of fruit, a portion of it
should be ripe.

Pectin can be usually esctracted from fruit by soak-
ing the latter in warm water, but sometimes it is
necessary to boil it (as shown in Experiment 56), and
this will always result in the extraction of a larger
quantity of pectin. If the cooking is continued too
long, however, the pectin will be decomposed to r^

The Chemistry of Cooking 363

dudng sugars and its gelatinizing property thus
impaired.

Pectin, in the presence of vegetable acids, is precipi-
tated or thrown out of solution by such substances
as alcohol, salts, and sugar. When a sufficiently large
amount of pectin and vegetable acid is present in a
liquid the whole solution will be formed into a thick
mass known as jelly by heating it with sug^ir. If more
sugar is used than there is pectin to unite with, the
mass will be soft and gtunmy or else the excess sugar
will crystallize.

The amount of acid present is also of importance
for the formation of a firm jelly, and when making
jellies from fruit that is not very add the juice of a
fruit that is or a small amount of dtric or tartaric
add is sometimes added.

Thus, it can be seen that to make a good jelly from
fruit, it is necessary to have proper proportions of
pectin, sugar, and add, and to cook the fruit the exact
time required. Consequently, the directions of a
reliable redpe must be followed accurately.

Experiment 56. A test for the presence of
pectin.

The common test for pectin is to add a little (about
5 c. c.) ethyl alcohol to an equal amount of fruit juice
or a water extract of the fruit. The formation of a
clear gelatinous predpitate indicates the presence of
pectin. At the completion of the experiment the
quantity of predpitate obtained from each fruit should
be compared.

Any fresh fruit can be used for this experiment, but
several should be tried, among others lemons, oranges,
and berries, and also carrots; raw fruits, both juices
and extracts, and similar cooked fruits shotdd be

364 Physics and Chemistry

tested; the juice, peel, and white part of oranges and
lemons should be tested separately.

A water extract of the fruit can be usually made by
soaking the fruit, after squeezing out the jtiice, in
warm water for about half an hour, but the pectin in
the peel and white part of oranges and lemons is hard
to extract; therefore, separate the two parts and (keep-
ing them separate) grind or cut them into fine strips,
cover these with water, heat this to boiling tempera-
ture slowly; strain, cool, and add alcohol to about
5 c. c. of the liquid. Repeat this treatment of the
white and peel (using the same portions) until a
filtrate is obtained that ceases to show the presence
of pectin.

Answer the following questions:

How many extracts were made of the white and of
the peel of the orange and the lemon before the filtrate
ceased to contain pectin?

Did you find more pectin in the juices or in the
extracts from the solid portions of the fruits?

What part of oranges and lemons causes marmalade
to jeU?

Will soaking oranges before cooking improve a
marmalade?

In which fruits did you find the largest amounts of
pectin?

Can jellies be made from all fruits containing pectin?

Is there the same amount of pectin in raw as in
cooked fruits?

CHAPTER XXI

THE SPOIUNG, PRESERVATION, AND ADULTERATION

OF FOOD

Causes for the Spdlins: of Food — Nature of the Orgsnisms that
Cause the Spoiling — Chemical and Physical Changes that
Occur in the Decomposition of Pood Substances— Omdi-
tions Necessary to Prevent Contamination and to Preserve
Food — Some Common Forms of Food Adultetatioo.

The Spoilliig of Food

Causes of the spoiling of food. — ^Food spoils becatise
it is attacked by the fungi known as molds, by yeast,
or by certain species of bacteria.

Molds

Nature. — Molds, of which there are many varieties,
are a species of fungi which, when fully developed,
consist of a mass of threads, known as myceliufn, on
which are minute sacs, known as the spore cases or
sporangia, that contain spores.

Multiplication. — Molds mtdtiply and spread be-
cause, when their spores mature, the sporangia burst
and the spores fall upon the food on which the parent
mold is growing or are blown about by the wind and

365

366 Physics and Chemistry

settle on other food, and, also, the spores are carried
by insects that have lighted upon molded food.

Experiment 67. Object: To study conditions that
favor the growth of molds.

Procedure: (i) Cut some pieces of bread into small
— ^about two inchds — squares, put several of these
together in layers, wrap them in paper, put them into a
tin box, and set the box in a warm place.

(2) Prepare some other slices of bread in a similar
manner, store them in a cool dry place.

(3) Put some pieces of bread loosely in a tin box
that has a few small holes in either side, for the drcu*
lation of air, and place the box in a cool, dry place.

(4) Repeat i and 3 with stale bread.

(5) Repeat i and 3 with fresh cheese.

(6) Repeat 5 with cheese taken from a piece that
has started molding.

(7) Place some pieces of fresh bread where it is
exposed to the air and where the sun will shine
upon it.

(8) Wrap some cereal in paper and place it in a
warm, moist place.

(9) Cut some pieces of fruit, including lemons, and
place them in saucers or evaporating dishes. Leave
them exposed to the; air.

(10) Make a little dilute and saturated sugar solu-
tions, boil them both for one minute, and then let them
stand exposed to the air in evaporating dishes.

Let these all stand for a week or longer; examine
them from time to time. Notice which ones start
to mold first; notice the difference in the appearance
of the molds.

As the result of your observations answer the fol-
lowing questions:

Spoiling and Preservation of Food 367

Is there any apparent change in the appearance of
the food? Has it grown less in quantity?

Is there any odor?

Will bread keep better where there is a free circula-
tion of air or where air is excluded?

How do temperature and moisture affect the growth
of molds?

Under what conditions must food be kept to prevent
it molding?

WiU dried food mold as quickly as that containing
considerable water?

Does the presence of a molded piece of food influence
the spoiling of the remainder of food kept in the same
place?

Does fruit acid inhibit the growth of mold?

Why will preserved fruits keep
better when a large amount of
sugar is used in their cooking?

Examine some of the different
molds under the microscope.
To do this, remove a small por-
tion of mold, with a platinum
wire or point of a penknife,
from the food upon which it is
growing and place it on a glass

slide; try to keep it in the same ^r.^^^.'L?!..^^ w*' ^

position as that in which it grew

on the food. ' Examine it with

the low-power objective of the

microscope.

Teast

Fig. 67.

SN OF M

Common Form of Mold
Magnified.

(a) Spores.

(b) Sporangium.

The nature and action of yeasts were discussed in
Chapter XX.

368 Physics and Chemistry

Bacteria

The bacteria concerned in the spoiling of food are
the various species classed as saprophytes; i. e., those
which feed on non-living organic matter and in doing
so catise it to putrefy, ferment, or decay.

Result of infection of food by molds, yeasts, and
bacterid* — ^These organisms use the food upon which
they fall for their nourishment, but they cannot do so
while it is in its natural condition any more than
human beings can assimilate the food they eat until
it has been digested. Therefore, just as happens in
the human alimentary canal, these organisms, by
virtue of enzymes which they secrete, cause the dis-
integration of food into simpler substances and from
these they remove what they require for their sub-
sistence. Some of the substances formed during the
process are gaseous and these soon pass from the
material; this is one reason for the loss of bulk and
accounts for the odors that develop. Some of the
other disintegration products are liquid and others
are soluble and go into solution in the water present;
thus food undergoing putrefaction, fermentation, etc.»
is usually softer than unspoiled food. When the
molecules of the food material are broken, they no
longer contain all the elements that they can hold in
combination and they unite with oxygen or other
elements; oxidation is thus associated with decom-^
position processes. Read the following chemical
formulas and decide which of the processes thus
portrayed are associated with oxidation:

spoiling and Preservation of Food 369

CHftOj « COa + CaHs- OH

CaHs,. OH + O - CH,. COH + HaO

CH,. COH + O = CH3. COOH

CH,. COOH + 30= 2C0a + HaO
Ammonia Carbamate Urea

COaNaHe - HaO = CONaH^

Butyric acid

C6H,a06 = 2Ha + COa + C^HgOa

Effect of changes caused by molds, etc., oa the
wholesomeness of food. — Certain molds and bacteria
are purposely cultivated in food in order to produce
the desired flavor, e. g., the molds of Stilton and
Roquefort cheeses, but in such case special cultures
of the organisms are used.

The common consequences of mold infection is the
production of a musty disagreeable flavor in the food.
As a rule, the substances formed by molds in food are
not poisonous, unless the condition proceeds to such
an extent that putrefactive bacteria are also at work,
as usually occurs in advanced stages of molding.
Consequently, when the molding is not extensive, if
the mold and the material lying directly below it are
removed, the food can be used. If it is to be kept for
any length of time, however, it must be boiled for at
least twenty minutes in order to destroy any spores
that may have fallen into it.

The substances produced by yeast are not un-
wholesome and fermentation can be arrested in the
same way as molding, but if the fermentation process
continues the food will become so acid that it will be
unpalatable.
.The substances produced by bacteria that cause

370 Physics and Chemistry

fermentation are similar to those produced by yeast,
but food in which putrefactive changes have occurred
has, when eaten, caused severe and even fatal poison-
ing. Just which germs are responsible for this so*
called ptomain poisoning is not known, but it is known
that they thrive better in the absence of air than in
its presence, and in warm places. Food which has
been in cold storage and later kept in a warm place
is particularly apt to be so infected.

Conditions and Food Most Conducive to the Life of

MoldSi etc.

As shown by Experiment 67, molds grow best in
dark, damp places where there is no free circulation
of air. Wliy moving air interferes with the growth
of molds is not wholly understood, but it is thought
that disttu'bance of their threads by the wind may
interfere with their growth and also that air currents
increase the rapidity of the evaporation of moisture
from the surface of the food and thus renders it an
unfavorable groimd for the molds. Thus, molds grow
much more rapidly in tightly closed vessels or cup-
boards than in those through which there is a current
of air; in food piled up than in that spread out; in
food filled with cavities, like bread and cheese, than
in that with a smooth surface. Though dampness
favors mold development, very moist food, as milk
and meat, are not as likely to be attacked by molds
as by bacteria. Molds, however, will grow upon food
far too dry to be used by bacteria (e. g., cereals and
dried fruit) when the atmosphere surro:unding the
food is moist.

Yeasts require food containing sugar or starchy

spoiling and Preservation of Food 371

substances that they can change to sugar. They grow
best at a temperature between 70** and 90** F. Their
growth is arrested at a temperature below 40^ F.
and they are soon killed at boiling temperattu^.

The majority of saprophytic bacteria thrive best
at a tcmperattire of 70^ to 90^ F.» and are killed by
moderate heat — 140® to 160® P. — if it is continued for
from thirty minutes to one hour, but there are some
species that thrive best at a temperature of about 140^
F. and can be killed at boiling temperature only if it
is maintained for at least one hour. The growth and
action of all species are inhibited at a temperature
below 40^ F. Bacteria grow better in darkness than
in light — direct sunlight will kill many varieties.
Bacteria, even more than yeasts and molds, require
, moisture for their development ; many kinds will not
grow in food containing less than 25 to 30 per cent,
moisture.

Practical Application of the Knowledgement of the
Requirements of Molds, Teasts, etc., to the

Keeping of Food

Since molds and bacteria prefer darkness to light,
kitchens and pantries should be very light rooms and
food cupboards and storerooms should be provided with
ventilators and they should be as light as possible
without raising their temperature. All these places
and all utensils into which food is put must be dry
and clean. ' Places where food is stored must be cold.

' Such tttensils as bread and cake boxes and cereal jars should
be frequently scalded and exposed to the air. Milk utensils
should be well aired and sterilised after use.

37^ Physics and Chemistry

Keeping Fruit and Vegetables

Such vegetables as potatoes and beets have some*
what different requirements from the majority of
f oodstuffs» for if given light and air, they will germi-
nate and sprout». therefore they are kept in the
dark, packed in bins or barrels. Carrots, turnips,
and parsnips keep better if buried in sand. For
all these vegetables, the storeroom must be cool
and dry. Winter squash, unlike the other vege-
tables, keep best if spread out in a rather warm
place.

It is most important for the preservation of fruit
and vegetables that they be kept dry while in storage.
Though, as shown by Experiment 67, some foods mold
more quickly when rolled in paper, because they are
then not exposed to air currents, soft, porous paper
wrapped around fruit that is packed in boxes seems
to prevent it molding and decaying, probably be-
cause the paper absorbs the moisture from the surface
of the fruit and prevents that in which decay has
started coming in contact with sound fruit. Grapes
are packed in sawdust for the same reasons. Drying
fruit with a soft doth also helps to keep it fresh. The
peel of fruit helps to protect it from molds and bac-
teria; thick-skinned fruits, like oranges and winter
apples, can be, with proper care, kept in their natural
state for months, but thin-skinned fruit, like cher-
ries, will not keep in good condition for any length
of time. Only fruit in perfect condition should be
stored; if the skin is bruised or broken, molds, etc.,
can easily enter and, as seen in Experiment 67,
one piece of molded food will soon infect that which
is sound.

Spoiling and Preservation of Food 373

Means of Preserving Food

The means usually taken to preserve food are (i)
sterilizing it and keeping it under sterile conditions.
(2) Keeping it in a temperature below 40** P, (3)
Drying it. (4) Adding substances to it that will in-
hibit the growth of organisms. When used for this
purpose such substances are called preservatives.

Sterilization. — Food to be preserved in this way
must be subiuitted to a high enough temperattu^, for a
sufficient length of time, to kill bacteria. It has been
found that the time and temperature necessary vary
with different foods; therefore, when preserving or
canning food, the directions of a reliable recipe book
regarding these matters should be followed. Some
foods, e. g,, peas, beans, and corn, require a very long
time — ^from one to two hours — at a temperature of
212° F., to be rendered sterile. Food will be better
sterilized if put into cold water and brought to boiling
point, than if put at once into boiling water. Sterilized
food, if it is to be kept, must be put into sterile jars,
while it is still hot, and sealed at once. The sealing
must be perfect, so that it will be impossible for germs
to enter. If, for instance, hard rubbers are used for jars
into which jam is put, the sealing will not be perfect
since the tightness with which the cover can be screwed
down depends upon the softness of the rubber.

In canning factories, tin jars are usually , used.
The fruit and vegetables, with or without previous
boiling, are put into the cans and the covers are sol*
dered on. There is a small hole in each cover, to
allow the air to escape as it becomes expanded by the
heat. The cans are placed in the heating apparatus
and left the required length of time. At the conclusion

374 Physics and Chemistry

of the sterilization, they are removed and the holes
are at once covered with solder.

Cold, — In order to preserve food by cold for any
length of time the temperature must be kept even and
below 40® F. — in fact, it is necessary for the preserva-
tion of many foods to keep the temperattu^ as low as
33® P. Even at this temperature, bacterial action,
though inhibited, is not entirely prevented and thus
food cannot be kept in cold storage indefinitely with*
out deterioration occurring.

Drying. — This is one of the most widely used means
of preserving food — ^meat, fish, fruit, and vegetables
all being preserved in this way. Some of the fruits
that are frequently thus preserved contain enough
sugar to aid in their preservation. Salt is often used,
in addition to drying, in the preservation of meat and
fish and these foods are sometimes smoked, as well as
dried, since the creosote of the wood acts as a preser-
vative by destroying germs upon the surface of the
food and by so impregnating it that bacteria cannot
grow in it.

Drying is usually accomplished by exposing the
food to heat from various sources and in various ways,
or else by submitting it to hydraulic pressure and
thus removing much of its water.

Drying toughens the fiber of foods, both those of
animal and vegetable origin, and causes considerable
loss and change of flavor. In order to minimize the
result of toughening, nearly all dried foods are soaked
in water for several hours before being cooked. This
does not, however, apply to the cereals, which are dry
by nattu'e and subjected to little if any artificial drying.

Preservatives. — ^These are often classed as legitimaie
preservatives and adulieranls.

spoiling and Preservation of Food 375

By legitimate preservatives are meant substances
that will inhibit the growth of germs, but in the
quantities used have no injurious effect upon man.
Those 'n common use are salt, sugar — used in suf-
ficient quantity to be concentrated — , spices, and
vinegar.

By adulterants are meant substances such as borax,
benzoic add, salicylic add, and formaldehyd. Some
people contend that these substances should not be
classed as adulterants for reasons that will be seen
later.

"According to the law of many of the States of
America, a food is dedared to be adulterated under
the following conditions:

"First, if any substance or substances have been
mixed with it, so as to lower or depreciate or injuri*
ously affect its quality, strength, or ptuity; second, if
any inferior or dieaper substance or substances have
been substituted wholly or in part for it; third, if
any valuable or necessary constituent has been wholly
or in part abstracted from it; fourth, if it is an imita-
tion of or is sold under the name of another article;
fifth, if it consists wholly or in part of a diseased, de-
composed, putrid, infected, tainted, or rotten animal
orvegetablesubstanceorarticle, whethermanufactured
or not, or, in the case of milk, if it is the product of a
diseased animal; sixth, if it is colored, coated, polished,
or powdered, whereby damage or impurity is con-
cealed, or if, by any means, it is made to appear better
or of greater value than it really is; seventh, if it con-
tains any added substance which is poisonous or in-
jurious to health. Provided: that the provisions of
this act shall not apply to mixtures or compounds
recognized as ordinary artides or ingredients of food^

376 Physics and Chemistry

if each and every package sold or offered for sale bear
the name and address of the mantifacturer and be
distinctly labeled tinder its distinctive name and in a
manner so as plainly and correctly to show that it is a
mixture or compound and is not in violation with
definitions fourth and seventh of this section." '

Those who contend that the antiseptic preserva-
tives mentioned on page 375 should not be classed as
adulterants base their assertion on the fact that the
preservatives are often of greater commercial value
than the foods in which they are used and that in the
small quantities in which they are used they are not
injurious to health. Those who take the opposite
view contend that even if the preservatives do them-
selves cost more than the food, they allow the manu-
facturers to use cheaper — even partly spoiled — food,
for preserving, canning, etc. Also they hold that it has
never been proved that even small quantities of sali-
cylic acid, borax, etc. , if constantly used, are not to some
extent injurious, especially to children and invalids.

A few simple experiments to detect the presence
of chemical preservatives in food*:

The chemical reagents required for these experi-
ments are as follows:

Turmeric paper Potassium permanganate 1%

Alum solution, 10% Ethyl alcohol

Iron alum (crystal or powder form) Chloroform
Sulphuric add Boric acid or borax

Hydrochloric add Ammonia water

Tincture of iodin

' Bulletin 100, U. S. Department of Agriculture.

* The majority of these experiments have been taken from
Bulletin 100, U. S. Dept. of Chemistry: "Some Forms of Food
Adulteration and Simple Methods for their Detection."

Spoiling and Preservation of Food 377

As in the tests to discover the constituents com-
posing food, the majority of tests to discover food
adulterants consist in the use of reagents that will, if
the matter sought is present, combine with it and
form a substance that will be precipitated or that
will give a special color reaction. As a rule, the tests
are better performed with the material being tested
in solution or, at least, in a semi-liquid condition.
Solid and semi-solid foods are therefore usually dis-
solved, and, if necessary, macerated in distilled water
before the reagent is added.

Salicylic Acid

Salicylic add is used for preserving condiments,
sauces, and fruit products of all kinds — jellies, marma-
lades, etc., — ^and it is a common constituent of the
various powders sold as preservatives.

Experiment 68. Put about 60 c. c. of the liquid
to be tested into a small flask, add a few drops of
sulphuric add, and shake the flask for two or three
minutes. Filter this solution into another small
flask. Add about 30 c. c. of chloroform and mix the
two liquids by a somewhat vigorous rotary motion
(shaking is to be avoided as it produces an emulsion
which is difficult to break up). Pour the solution into
a beaker. Let it stand until the chloroform settles
at the bottom and then, with a medicine dropper or
pipet, transfer as much of the chloroform as possible
to a test tube. As salicylic add is soluble in chloro-
form, it will now, if there was any present in the food,
be in the chloroform. To the chloroform, add an
equal amount of water and a small piece (a little
larger than a pinhead) of iron alum. Shake the mix-

378 Physics and Chemistry

ture and then allow it to stand until the chloroform
again settles at the bottom. If salicylic add is
present, a pmple color will develop at the top of the
liqtiid.

Benzoic Acid

Benzoic acid is often used for preserving jams,
jellies, tomato catsup, and similar articles.

Experiment 69. Extract the sample with chloro-
form according to the directions given for salicylic
acid, but, after removing the chloroform, put it into
a beaker and put this in a warm place or a water
bath. Let it stand thus until the chloroform evapo-
rates. If benzoic acid is present, it will be seen in the
form of characteristic flat crystals on the bottom of
the beaker and these, if heated, will emit the tmmistak-
able odor of benzoic acid.

Boric Acid and Borax

Boric acid — ^known also as boracic (idd — ^and its
sodium compound borax are often used to preserve
animal foods, such as sausages, butter, and milk.

Experiment 70. To prepare solid food for this
test, macerate it with distilled water, strain it through
fine white cotton cloth, and then filter the liquid thus
obtained through filter paper.

To prepare butter, place a heaping teaspoon in a
beaker, add about 10 c. c. of boiling, distilled water,
stand the beaker in a water bath until the butter is
thoroughly melted. Stir this with a teaspoon and
place the beaker, with the spoon in it, in a cold place
until the butter becomes solid. Remove the spooQ

Spoiling and Preservation of Food 379

and the butter (which adheres to it) and filter the
liquid through paper.

To prepare milk, pour about 60 c. c. into a small
flask with about twice that amount of a 10 pef cent,
solution of alum, shake the mixture vigorously, and
then filter it.

Test: Take about 5 c. c. of the liquid obtained as
described, add and mix thoroughly 5 drops of con-
centrated hydrochloric add. Dip a strip of turmeric
paper into the liquid and then hold the paper in a
warm place until it dries. If there is boric acid or
borax in the liquid, the paper, when dry, will be a
bright cherry red and a drop of ammonia will change
the red color to dark green or greenish black. If too
much hydrochloric add is used, the turmeric paper
may become a brownish red, even though there is n6
boric add in the solution; in such case, however,
ammonia changes the color to brown, just as it does
turmeric paper which has not been dipped into the
add solution.

Formaldehyd

Formaldehyd, being volatile, is useless as a pre*
servative for food that is to be kept for any length
of time, but it is often used in warm weather to pre-
vent milk souring. It is probably the most com-
monly used milk preservative at the present time,
though boric and salicylic adds are also used.

Experiment 71. Pour about 30 c. c. of milk into a
flask and an equal quantity of concentteted hydro-
chloric add. Add a small piece of ferric alum (about
the size of a pinhead) and mix the fluids by rotating
the flask between the hands. Then place the flask

380 Physics and Chemistry

in a water bath containing boiling water and let it
stand for five minutes (do not keep heat under the
bath during this time). If formaldehyd is present,
the mixture will become purple.

Copper Sulphate

Copper stilphate is sometimes added to canned green
vegetables, especially peas, to improve their color.

Experiment 72. To about a teaspoonful of the
mashed vegetable add three teaspoonfuls of water and
30 drops of strong hydrochloric add. Stir the mix-
ture with a piece of wood and set the beaker in a
water bath. Drop a bright iron wire nail (tin carpet
tacks will not do) into the mixture and keep the water
surrounding the beaker boiling for twenty minutes.
Stir the mixture frequently. At the end of twenty
minutes, remove the nail and examine it. If there
was any appreciable amount of copper in the mixture,
the nail wiU be coated with it.

Other Forms of Adulteration

The mixing of a cheap article with a more expensive
one is an even more common form of adulteration
than the use of chemicals for preservation. For ex-
ample, cheap cereals and flours are mixed with more
expensive ones; chicory, ground beans, and the Uke
are mixed with coffee; starch and saccharin are added
to jellies; cheap fruits, as apples, are mixed with rarer
ones in jellies and jams. As apples are as wholesome
as any other fruit, their addition to jams, etc., is not
considered an adulteration if their presence is stated
on the label.

Spoiling and Preservation of Food 381

Experiment 73. To detect starch in jellies, jams,
etc. In order to detect starch in any substance, the
iodin test is used, but, so that change of color may
be perceived if it occurs, it is necessary to decolorize
colored substances such as jellies. To do this, dis-
solve the material, heat it to boiling point, and add
potassium permanganate, drop by drop, until the
liquid is colorless. Then cool the mixture and add
iodin. The presence of starch is indicated by the
iodin becoming blue.

Adulteration of Cereals and Flours

Unchanged starch grains have the characteristic
structure of the seed in which they were formed, and
as the seeds of different plants vary in shape, micro-
scopic examination of starch, etc., is a means often
employed to detect adtdteration of one grain with
another, as, for instance, wheat flour with com flour,
which is cheaper.

^_ Adulterations of Coffee j

The presence of adulterants in coffee can be often
detected by examining a sample under a magnif3ring
glass. When seen under the glass, the coffee particles
appear quite different from the coffee substitutes em-
ployed. Chicory, especially, having a dark gtunmy
appearance, stands out in strong contrast to the
coffee. All the usual coffee substitutes, except chicory,
contain starch and, therefore, the iodin test is another
means of detecting adulterations other than chicory.
A weak infusion must be used so as not to obsctu'e the
color change. Still another method of testing ground

382 Physics and Chemistry

coffee is to put a small amount of coffee into a bottle
half-full of water, shake the bottle vigorously, and
then let it stand quietly. Pure coffee contains a
large amount of oil and, consequently, it will float
while the substitutes sink to the bottom of the flask.

Adulterations of Butter

The so-called spoon test is often used to distinguish
pure butter from renovated or process butter and
oleomargarin.

Experiment 74. Take a small piece of the butter
sample in a large spoon and hold it over the Btmsen
flame. If the sample is fresh butter, it will boil quietly
with the evolution of a large amoxmt of froth. Oleo-
margarin and process butter, on the other hand,
crackle and sputter as they melt and boil.

The Adulteration of Salad Oil

The adulteration of salad oil with cotton-seed oil*
is not uncommon.

The Halophen test is very often used to detect this
adulteration.

Experiment 75. Procedure: Put about 5 c. c. of
oil into a test tube and add an equal quantity of both
amyl alcohol and carbon disulphid. Cork the tube
and place it in a beaker of hot water. Leave it thus
for half an hour; keep the water hot during this time,
but do so by the addition of boiling water when neces-
sary; do not bring the tube near a flame, for carbon
disulphid is excessively inflammable. At the end of
that time, if even a small percentage of cotton-seed oil
be present, the mixture will be of a distinct reddish

Spoiling and Preservation of Food 383

color, and if the sample consists largely or entirely of
cotton-seed oil, the color will be deep red.

The Adulteration of MUk

The more common methods of adulterating milk
are: The use of preservatives, the addition of water,
the removal of a part of the cream.

The preservatives most conamonly used are formal*
dehyd and boric add. Means of detecting these have
been already discussed. The presence of preserva-
tives in milk is particularly objectionable because (i)
it is so much used for invalids and young children
who may be injured by such preservatives; (2) the
action of lactic add bacteria is easily inhibited and
the souring of milk thus retarded, but germs which
cause putrefaction are not so easily affected and the
changes which they cause in milk, while infinitely
worse, are not so easily detected. Consequently,
milk containing preservatives may also contain inju-
rious products of putrefaction. It is such substances
in milk that are often responsible for the gastro*
intestinal disturbances in children that are so common
in summer.

The presence of water in milk is determined by the
use of a lactometer or hydrometer. The spedfic
gravity of water, it will be remembered, is said to be
I and that of ordinary whole milk, as compared with
water, is 1.027 to 1.033. If the milk contains more
than 4 per cent, cream it may be slightly lower than
these figures, but much difference indicates the pres-
ence of the liquid with the lower specific gravity,
i. «., water.

The Babcock test. — ^This test is very commonly

384 Physics and Chemistry

tised for estiinating the per cent, of fat in milk. The
test depends upon the fact that the organic mattar
of loilk, except fat, is decomposed by sulphuric acid,
while, practically, the only change in the fat is that it
is set free.

The articles required for the test are: A milk test
bottle (see Fig. 66 ; this bottle has a long neck, gradu-
ated in such a way that the nimibers i, 2, 3, etc., re-
present I, 2, 3, etc., per cent, fat and the small lines
between the numerals represent -nr of i per cent.) ;
a graduated pipet; an acid measure; a centrifugal
machine; the milk to be tested; hot water; sulphtuic
acid with a specific gravity of 1.82.

Procedure: The milk to be tested is measured with
the pipet. To do this, hold the pipet between the
thtunb and middle finger, put the pointed end of the
pipet into the milk and the other end in the mouth,
and, by suction, draw the milk up above the marks
on the stem. Then, quickly, put the index finger
over the upper end of the pipet, to keep the milk from
running out. Next, hold the pipet vertically, with
the 17.6 mark on a level with the eye and, by slightly
relaxing the pressure of the finger covering the upper
end of the stem, allow the milk to flow out until it is
at the 17.6 mark. Then place the pointed end of the
pipet in the mouth of the milk bottle, holding both
bottle and pipet obliquely, remove the finger from the
upper opening and let the milk run down the neck of
the bottle. If the milk is put in otherwise, the air
in the bottle may form bubbles in the milk and cause
it to overflow. If the milk does not all leave the
pipet, blow into the upper end of the tube. Fill the
acid measure to the 17.5 mark with stdphuric acid
Md add this to the milk slowly, holding the bottle

w ■ {/)

Pig, 68. Apparatus for Babcock Milk Test.
[at MHk Bottle. (6) Pipct. (c) Acid Measure.

[d), (e), ( n Different varictiL-S of Ctntrifujpil Machines.
Id) A two-botlle Hand Machine (not in acllon).
' A four-bottle Hand Machine (in action).
An Electric Machine.

386 Physics and Chemistry

obliquely while doing so. (N. B., remember that
sulphuric add is very corrosive.) Whirl the bottle in
the centrifugal machine for five minutes. Remove
the bottle, add enough hot water to bring the fat
into the narrow neck. The fat can be easily dis-
cerned, for it is lighter in color than the rest of the
liquid, which holds the decomposed organic matter
in solution. After the addition of the water, replace
the bottle in the centrifugal machine and whirl it for
three minutes. This brings all the fat to the top.
Then remove the bottle and, holding it with the fat
on a level with the eye, note the marks opposite its
upper and lower levels. To estimate the per cent,
of fat it is necessary to subtract the number below
the level of the fat from the top reading. For example,
if the upper level of the fat is on a line with the mark
5.2 and the lower level with the mark i. 2, the correct
reading will be 4 per cent, since 5.2 — 1.2=4. This
would show that the milk tested contained 4 per cent,
fat.

CHAPTER XXII

CHEMISTRY OF DIGESTION

•

The Nature of the Changes Occurring in the Digestion of the
Various Pood Stuffs — The Organs in Which These Changes
Occur — ^The Factors and Conditions Influencing Digestion
— Nature of Enzymes, Zymogens, and Kinases.

Reason for digestion. — ^With the exception of the
monosacchaxids and the disaccharids, organic food sub-
stances are unable to pass through animal membranes
and, consequently, they are of no use to the body
until they undergo certain changes which transform
them into substances that will go into solution and
pass through the walls of the blood-vessels and lacte-
als. For it is only after food has passed into the
blood and been carried by it to the tissues that it bene-
fits the body. The various changes that food tmder-
goes in this process of preparation are classed as
digestion.

Mineral matter, monosaccharids, and disaccharids
are readily soluble in water and the two first men-
tioned are quickly absorbed from the stomach and
the intestines. Disaccharids will be absorbed un-
changed if eaten in large quantities, but, when this
happens, they are qtiickly eliminated from the system
in the urine, the tissues being unable to utilize them.

Nature of digestion. — ^The digestion of proteins and
carbohydrates consists of a process of hydrolysis — i. e.,

387

388 Physics and Chemistry

decomposition due to the absorption of, and chemical
combination with, water. The digestion of fats con-
sists of a preliminary splitting of the fats into fatty
acids and glycerin, followed by the saponification of
the fatty adds.

Results of hydrolysis and saponification. — ^As the
result of hydrolysis, complex molectdes are divided and
simpler substances thus formed; for example, one
molecule of a disaccharid (CiaHaaOn) by hydrolysis
gives 2 molecules of a monosaccharid 2(C6Hxa06).
There is only one splitting of the molecules in the
hydrolysis of the disaccharids, but the polysaccharids
(C6Hxo05)x' pass through several stages before they
are completely hydrolyzed. The substances yielded
at the different stages in the digestion of starch are
dextrins (known, according to the colors which they
give with iodin, as erythrodextrin i, 2, or 3 and achro-
dextrin, see page 398) , maltose, and glucose. The pro-
tein molecule also undergoes several splittings, thereby
giving rise to such substances as metaproteins, pro-
teoses, peptones, and amino acids. The nature and
the results of saponification whereby fats are digested
have been already discussed (Chapter XVI.).

How hydrolysis and saponification can be brought
about. — Starches, sucroses, and proteins can be hydro-
lyzed and thereby made to undergo the changes
described in the preceding paragraph by boiling them
with acid and by the use of ferments. The ferments
used to digest starch outside the body are usually
obtained from plants; one of the best known is diastase
of malt, a substa/ice that is produced during the ger-

« The X, it wQl be remembered, signifies that the molecules of
polysaccharids contain an unknown number of molecules with
the construction demonstrated by the formula.

Chemistry of Digestion 389

mination of certain seeds and that is contained in
malt. The ferments used to digest proteins are
extracted from the stomach or pancreas of animals,
especially pigs. Within the body, hydrolysis is caused
by the ferments or enzymes contained in the digestive
juices. Saponification, outside the body, is brought
about by boiling fats with alkalies and, within the
body, by an enzyme contained in the pancreatic juice
and the alkaline salts of the pancreatic and intestinal
jmces and the bile.

Nature of the digestive juices. — The digestive
juices secreted by the salivary glands, by the gastric
and intestinal glands, and the pancreas consist of
water, salts, mucin, and specific enzymes. The re-
action of the saliva is, normally, neutral or faintly
alkaline; that of the gastric jtiice, add (due to the
presence of hydrochloric acid) ; and that of the pan-
creatic and intestinal juices, alkaline. The bile,
which is secreted from the blood by the liver, consists
of water, bile salts, and inorganic salts, mucin,
cholesterin, lecithin, fat, and bile pigments.

The bile pigments are derived from hemoglobin;
it is thought that when red blood-corpuscles become
disintegrated the freed hemoglobin is brought to the
liver, where, under the influence of the liver cells,
its iron is split off and it is converted into bilirubin or
biliverdin, the characteristic pigments or coloring
matter of bile. Normally, bile has an alkaline re-
action.

Enzymes, Zymogens, Kinases, Hormones

The nature and action of these substances which
are so essential to digestion and metabolism are as
yet very imperfectly understood.

390 Physics and Chemistry

Enzymes. — ^Enzymes are protdn-containing sub-
stances, of unknown composition, produced by living
cells, both animal and vegetable. Enzymes act as
catalyzers — ». e., they hasten chemical reactions, but
they do not themselves enter into the reaction.
Nearly all the processes, both of building and of dis-
integration that take place in animals and plants are
controlled to some extent by enzymes. Enzymes are
easily influenced by temperature; those of animal
origin act best at body temperature; those obtained
from plants usually work better at higher temperattu'es
than this, but all enzymes are destroyed by extreme
heat and are rendered more or less inactive by cold.
The majority of enzymes are also very sensitive to
the reaction of the meditun in which they are con-
tained; some needing an add and others an alkaline
or neutral medium. They are all destroyed by strong
adds and alkalies. Nearly all enz3niies are spedfic
in their action — i, «., they each have their spedal work
to perform and they do only that work.

According to their action, the majority of enzymes
fotmd in the animal body have been classified as
follows:

(i) Hydrolytic enzymes — ^those which cause hydro-
lysis. To this dass belong the proteolytic or pro-
tein-splitting enzymes, the lipolytic or fat-splitting
enzymes, the amyloljrtic or starch-splitting enzymes,
and the invertases or sugar-splitting enzymes.

(2) The coagulating enzymes — such as the throm-
bin of the blood and the rennin of the gastric juice.

(3) The oxidases — enzymes in the body tissues
that are essential for oxidation processes.

(4) Reduction enzymes — ^those which remove oxy»
gen from matter.

Chemistry of Digestion 391

Zymogens. — Certain enzymes, notably the rennin
of the gastric juice and the trypsin of the pancreatic
juice, are secreted in an inactive form. This is neces-
sary because the pepsin and trypsin, being formed for
the purpose of hastening the digestion of proteins,
would, if present in the gland secreting them in the
active state, cause the digestion of the gland. Such
inactive enzymes or precursor of enzymes are called
zymogens. The zymogen of pepsin is called pep-'
sinogen and that of trypsin, trypsinogen.

Elnases. — Enzymes, or other substances, that pro-
duce the necessary change in zymogens to render
them active, are called kinases — for example, the
enzyme enterokinase of the intestinal jtiice which
activates the trypsinogen of the pancreatic jtiice.

Hormones, secretins. — Hormones are chemic sub-
stances that are produced in certain organs and then
absorbed and carried by the blood to other organs
which they stimulate. Of this nature is the secretin,
a chemic substance of unknown composition, which
is produced from a substance secreted in the intestinal
mucous membrane, called prosecretin, by the action
upon it of the acid material entering the intestine
from the stomach in the course of digestion. This
secretin, when absorbed by the blood, is carried to
the pancreas, liver, and possibly to the intestinal
glands, and produces or increases the activity of these
glands. A secretin is also produced in the mucous
membrane of the pyloric portion of the stomach,
which, being absorbed and carried by the blood to
the secretin cells of the gastric glan(^» excites them
to activity.

The names of the digestive juices, the enzymes
they contain, the action of the latter upon food, and

392

Physics and Chemistry

the organs in which the digestive processes occur can
be seen in the following table:

Organ in
WHICH Juice
IS Secrbtbd

Saltvarv
lianas

Gastric
glands

Pancreas

Intestinal
glands

Liver

DiGBSTTVB
JUICB

Saliva

Gastric
juice

Pancreatic
juice

Succus

entericus or

intestinal

juice.

Enzyme

Dile

^Ptyalin
Maltase

( Kennin
J Pepsin

L Lipase

'Amylopsin
Trypsin

Lipase or
Iteapsin

Enterokinase

Erepsin

Maltase
Sucrase
T»artaBfl

None

Action of
Bnzymb

Chaoges starch to
dextrin and maltose.

Changes maltase
to fflucose.

Curds milk.

Starts the diges-
tion of proteins.

Splits emulsified
fats, as cream, to' fat
ty acids and glycerin.

Same as ptvalin.

Continues the work
of the pepsin.

Splits fats to fatty
acias and glycerin
and aids in the sapo-
nification of the fatty
acids.

Activates the tryp-
stnogen of the pan
creatic juice, chang
inff it to trypsin.

Continues the work
of the pepsin and
trypsin.

Changes maltose
to glucose.

Changes sucrose to
glucose and fructose.

Changes lactose to
glucose and galac-
tose.

Helps in the sapo-
nification of fati and
promotes absorption.

Where Action
Occurs

In the mouth
and, for a short
time, in the stom-
ach.

In the stomach.

In the intestine.

The hydrochloric acid of the gastric juice. — The

gastric juice is the only secretion of the body that
contains a free acid. This add — ^hydrochloric — ^is
made, it is thought, from sodium chlorid (NaCl)
taJken from the blood by certain cells situated in the
middle region of the stomach. One reason for the
supposition that these special cells secrete the add
is that in the ftmdus and the pyloric region of the

Chemistry of Digestion 393

stomach, the gastric juice is less add than it is in
the central portion. In these cells, it is thought, the
NaCl is by some means broken into Na and CI and
the CI combines with H, thus forming HCl. The
per cent, of HCl in the gastric juice during digestion
is usually estimated at from 0.3 to 0.5 per cent. A
much lower or higher degree of acidity interferes with
digestion.

The prindpaj purposes of the hydrochloric add are
as follows: It activates the pepsinogen and assists in
the digestion of protdns; it regulates the passage of
food from the stomach; it acts as a kinase in that it
acts upon the pepsinogen and changes the prosecretin
contained in the mucous membrane of the intestinal
wall to secretin; it acts as a disinfectant. HCl arrests
the action of ptyalin when the food with which that
enzyme became mixed in the mouth becomes satu-
rated with the add. However, as there is little or
no add in the fundus of the stomach, the ptyalin may
continue its action on starch while the latter remains
in that part of the organ and, as the mechanical action,
which chums apd pushes the food onward, is not very
great in that region, some of the starch may remain
there for twenty minutes or more.

How hydrochloric acid regulates the passage of food
from the stomach. — ^The reaction of secretions in the
stomach, when the latter is empty, is, normally, neutral
or slightly alkaline, the HCl being secreted only after
food enters the stomach. As protein and HCl have
a strong affinity for each other, the protein of the
food and the add formed at once combine and it is
only after all the protdn has become saturated with
the add that there is any free HCl in the gastric juice.
As soon as this happens, under the influence of the

394 Pities and Chemistry

acid, the pyloric sphincter muscle, which encircles
the orifice between the stomach and the duodenum
and is usually in a state of contraction, relaxes and
some of the acid chyme^ passes into the intestine.
This makes the alkaline contents of the intestine acid
and the effect of acid on this side of the pyloric
sphincter is to cause it to contract. The pylorus
remains closed until the intestinal contents are alka-
line when it once more relaxes and the procedure is
repeated.

Factors influencing the secretion of digestive
juices. — ^Various experiments have shown that the
secretion of the digestive juices is very largely con-
trolled by (i) the nervous system and (2) secretins.
The stimulation of the parts of the nervous system
that are concerned with the digestive process is brought
about in several ways; e. g., the smeU and taste of
food — provided that they are agreeable — and the
movements of the jaw in mastication all stimulate
various nerve-endings in and around the mouth.
This results in the stimulation of certain nerve-
centers in the medulla oblongata from which impulses
pass to the secretory cells of the salivary and gastric
glands and stimulate them to secrete. The entrance
of food into the stomach also excites nerve-impulses
which stimulate the secretion of gastric juice, but the
principal sources of gastric stimulation are thought
to be the secretins formed in the pyloric mucous
membrane and, during digestion, from food. The
secretin formed, as already explained, in the small
intestine after the acid chyme enters it from the
stomach, stimulates the pancreas and probably the

' This 18 the name given to the substance resulting from gastric
digestion.

Chemistry of Digestion 395

intestinal glands to secrete and it increases the activity
of the liver.

The entrance of food into the small intestine also
causes the sphincter muscle closing the duodenal
opening of the common bile duct to relax, thus allow-
ing the passage of bile from the liver and gall bladder
into the intestine.

The kinds of food eaten influence the nature and
quantity of the digestive juices; fats, for instance,
retard gastric secretion, and sugars, condiments, meat
extracts, and alcohol increase it. The amount of the
various enzymes present in the digestive juices varies
with the kinds of food eaten, and it is thought probable
that there are specific stimuli contained in food or
produced during digestion whose action is of a kind
to arouse reflexly the secretion best adapted for the
digestion of the kind of food that is eaten.

Digestion is aided also by the contractions of the
stomach and intestinal walls. Weakness of the muscle
tissues of these organs, or any form of interference
with their mechanical action, is likely to be followed
by digestive disturbances and, frequently, by an ac-
cumulation of fermentation or putrefactive products.
These are due to bacterial action upon food that re-
mains too long within the stomach and intestines.

Action of bacteria in digestion. — After birth, there
are always a large number of difiEerent kinds of bac-
teria present in the alimentary canal. The varieties
that exist in the stomach and intestines are, tmder
normal conditions, unless present in abnormally
la;rge numbers, not only not injurious to man, but of
use, for they help to protect the body against the
invasion of harmful varieties, and they help in decom-
posing food into simpler substances, causing, in fact,

396 Physics and Chemistry

much the same kind of changes as are produced by
enzymes. Under abnormal conditions, however, as
when the mechanical action of the stomach and in-
testines are defective and food remains too long in
these organs, or when, for any reason, the digestive
power is impaired, fermentation and putrefactive
changes may be carried too far a^d gases produced,
thus causing flatulence. Also various substances
may be formed that, when absorbed into the blood,
are more or less injurious to the system. Of these
substances, the best known is indol, which is produced
in the intestine by the excessive putrefaction of pro-
teins. It is changed, it is thought, in the liver, to
indican a^d a? such is excreted by the kidneys. The
a^mount of indican in the urine is therefore ap index of
the degree of putrefaction occurring in the intestines.

Kinds of bacteria in the alimentary canal. — The
principal varieties of bacteria present in the alimen-
tary tract are those which promote fermentation and
putrefaction. The various organisms that produce
these two processes do not thrive well together and,
normally, bacteria which produce fermentation are
found in the stomach — these requiring considerable
air — and those which produce putrefaction and thrive
best without air, in the intestine. So great is the
inhibitory action of these organisms on each other
that lactobacilli — organisms that produce lactic add
fermentation — are used medicinally to lessen intestinal
putrefaction.

Products of digestion. — ^As the result of digestion,
there are found in the intestine monosaccharids, soaps,
peptones, and amino acids. Also, there will be present
varying amounts of undigested and imperfectly
digested food, nuneral matter, ajad water.

Chemistry of Digestion 397

The products of digestion, mineral matter, and
much of the water are principally absorbed from the
small intestine. The changes that occur in the soaps
and protein derivatives during absorption will be
discussed in Chapter XXIII. The sugars and pro-
teins pass directly into the blood, via the capillaries
that are contained in the villi covering the inner wall
of the intestine. These capillaries connect with the
portal vein through which these absorbed substances
pass to the liver. A small portion of the fat may enter
the circulation in this way, but by far the greater part
only reaches the blood after it has passed through the
lymphatic vessels that extend from the lacteals (the
small lymph vessels in the villi of the intestine) to
the thoracic duct which opens into the left innominate
vein between the left subclavian and the left internal
jugular veins.

Feces. — All the matter not absorbed passes slowly
through the intestine and is eliminated from the
rectum. Chemical and microscopical examinations
of feces show its principal constituents to be food resi-
due mixed with digestive juices, dead and living
bacteria, and a small amount of waste matter formed
in metabolism. The last passes from the blood as
it flows through the intestinal blood-vessels.

Experiments on Digestion

Nature of the experiments. — Many of the experi-
ments used in studjring the progress of digfestion are
the same as those described in Chapter XVIII. The
iodin and reduction tests (see pages 289 and 290) are
used in studying the digestion of starch, since if, when
iodin is added to the solution being tested, a blue

39* Physics and Chemistry

color develops, it shows that starch is still present and
that digestion has not started; the development of a
purple color shows that the starch has been changed
to erythrodextrin No. i , which is the first stage in the
digestion of starch; a red color indicates the presence
of erythrodextrin No. 2, a red-brown that of erythro-
dextrin No. 3, and a loss of color from the iodin shows
that the starch has been changed to either achro-
dextrin, maltose, or glucose; which of the three can be
determined by finding the amount of solution that it
takes to reduce 10 c. c. or other given quantity of
Fehling's solution since it takes 0.5 gm. of glucose,
0.8 gm. of maltose, and about i.o gm. of dextrin to
reduce 10 c. c. of Fehling*s solution. Consequently,
there will be a greater amount of precipitate when
the solution tested contains glucose than when it is
maltose or dextrin that is present, and a sufficiently'
accttrate judgment for class purposes can be made by
comparing the relative color and amount of predpi-
tate formed in all the tests of an experiment. Of
course, the same amount of the solution to be tested
and of the reducing solution must be used in all tests
that are to be compared.

i The reduction tests are used also to see if disaccha-
rids have been hydrolyzed, since they, like starch, are
changed to monosaccharids in digestion.

The biuret and xanthoproteic tests — described on
pages 283 and 284 — ^are much used in studying the
digestion of proteins for they give different color re-
actions with undigested and digested proteins. The
biuret reagent assumes a violet color in the presence of
undigested! proteins and a rose color in a solution of
peptones, while the solutions used for the anthro-
proteic test become orange-colored in solutions oon-

Chemistry of Digestion 399

taining undigested or only slightly digested proteins,
but this color does not develop after the proteins have
been changed to proteose and peptones.

The progress of the digestion of fats can be observed
by the use of litmus, for, as soon as the fats in a solu-
tion are split to fatty adds and glycerin, blue litmus
will become red, as it always does in the presence of
adds.

N. B. — ^The measurements for these tests must be
espedally accurate, very slight inaccurades bdng
suffident to spoil many of them. Before beginning
experiments number the tubes as described on page
II. Differences in color in many of the tests is very
slight and can be usually detected only by compari-
son, therefore all results must be kept until a test is
completed.

Experiments 76 to 78.

Object: To study the digestion of starch.

Articles reqtiired : Test tubes, test-tube racks, Bun-
sen btuner, iron stand, c. c. measures, funnels, filter
paper, ice, starch paste made as directed on page 21,
distilled water, iodin, Fehling's solution, saliva. Be-
fore attempting to collect the saliva, rinse the mouth
with water. Thinking of something good to eat,
chewing a little paraffin or moving the jaws as though
doing so, or inhaling a little ether vapor will increase
the flow of saliva. Collect the saliva in a test tube,
add an equal amount of distilled water to it and filter
it.

Experiment 76. Object : To test the action of saliva
onstardi.

Procedure: Into a tube marked i, pour 10 c. c. of
starch paste, into tube 2 pour 5 c. c of starch paste

400 Physics and Chemistry

and 5 c. c. of saliva. In tube 3 put about 5 c. c of
crackers mashed in a small amount of distilled water
and 5 c. c. of saliva. Shake the tubes containing the
saliva so as to mix the latter thoroughly with the
starch or cracker. Put all three tubes into a water
bath and keep them at a temperature of 40^ C. Af t^
five minutes pour 2 c. c. from each of these tubes into
separate tubes, divide each 2 c. c. and test one portion
with iodin and one with Fehling's solution. Repeat
this procedure every five minutes for thirty minutes.
Keep all the tests in order until the completion of the
experiment and then compare the colors.

Why did the crackers show the presence of glucose
before the starch?

Experiment 77. Object : To test the effect of adds
and alkalies on the ptyalin.

Procedure: Into each of three tubes put about i
c. c. of starch paste and i c. c. of saliva. To tube 2
add 2 c. c. of 0.4% HCl and to tube 3, 2 c. c. of 2%
NaaCOj. Put the three tubes into a water bath and
keep them at a temperature of 40** C. for twenty
minutes, then divide the contents of each tube into
two equal portions and test one portion with iodin
and the other with Fehling's solution.

Experiment 78. Object : To test the effect of tem-
perature on the enzymes of the saliva.

Procedure: Put about i c. c. of starch paste into
each of three tubes. To tube i add an equal amount
of saliva, to tube 2 add an equal amount of saliva that
has been boiled for at least three minutes, put both
these tubes into a water bath and keep them at a
temperature of 40® C. for twenty minutes. To tube
3 add saliva that has been chilled by keeping the tube
containing it between pieces of ice. After miidng

Chemistry of Digestion 401

the starch and saliva, surround the tube with ice»
leave it thus for twenty minutes. At the end of
twenty minutes divide the contents of the three tubes
into equal portions and test one portion of each with
iodin and the other with Fehling's solution.

Experiments 79 to 80.

Object: To test the digestion of proteins.

Articles required: The same apparatus, but not
the solutions, as for the experiments with starch.
Also, concentrated nitric acid, ammonia, sodium
hydroxid io%, copper sulphate solution 1%, hydro-
chloric acid 0.5% and 2%, sodium carbonate solu-
tion 10%, pepsin solution, (see page 21), fibrin. Dried
fibrin, derived from blood, can be obtained at dealers
in scientific apparatus. Meat or egg can be used
instead of fibrin, but the results are not as quickly
obtained. The biuret test cannot be used with egg^
since egg albumin sometimes gives, unlike other un-
digested proteins, a rose color.

Experiment 79. Object : To test the efifect of hydro-
chloric acid and alkali on pepsin.

Procedure: Mark tubes i, 2, 3, 4. Into each tube
put a small piece of fibrin and about 4 c. c. of neutral
pepsin solution. To tube 2, add an equal amount of
0.5% hydrochloric acid, to No. 3 add an equal amount
of 2% hydrochloric acid,' and to tube 4 an equal
amount of 10% sodium hydroxid solution. Let the
four tubes stand in a water bath kept at 40 ® C. for
twenty minutes. Watch the changes that occur in
the fibrin during this time. At the end of twenty

* Be careful not to use too much acid, for though, as this test
should show, strong acid interferes with the action of pepsin, it
will, if stronger than necessary, itself aid in the hydrolysis of the
protein.
26

402 Physics and Chemistry

minutes pour off about 2 c. c. of the fluid from each
tube into separate tubes and apply either the biuret
or xanthoproteic tests (see pages 283 and 284). Let
the fibrin remain in the remaining i c. c. of solution
until that in tube 2 is dissolved — this may require
several hours — and then filter the solutions into sepa-
rate tubes, divide each one into equal parts, and test
one portion with the biuret and the other with the
xanthoproteic test.

Account for the results.

Experiment 80. Object: To study the effect of
temperature on pepsin.

Procedure: Mark tubes i, 2, 3. Put a small piece
of fibrin into each tube. Add enough HCl to 10 c. c.
of neutral pepsin solution to make it a 0.2% add
solution. Divide this into three parts. Surrotmd
the tube containing one portion with ice and leave
it thus until it is thoroughly chilled, then pour it over
the fibrin in tube 3 and put this tube between ice.
Boil another portion for at least three minutes and
then pour it over the fibrin in tube 2, add the third
portion to the fibrin in tube i. Put tubes i and 2
into a water bath and keep them in a temperature of
40° C. for twenty minutes. Then filter the contents
of all three tubes into separate tubes and apply the
biuret test.

Experiments 81 to 83. Object: To study the action
of the pancreatic juice.

Articles required: The same apparatus used in the
experiments with the saliva and gastric juice, also
starch solution, pancreatic solution — see page 21 —
hydrochloric acid 2%, sodium carbonate solution
2%, soditun hydroxid solution 10%, litmus powder,
noilk.

Chemistry of Digestion 403

Experiment 81. Object: To test the effect of pan-
creatic solution on starch.

Procedure: Repeat Experiments 76 to 78, using
pancreatic juice instead of saliva.

Experiment 82. Object: To test the effect of pan-
creatic solution of protein.

Procedure: Repeat the Experiments with pepsin
solution, using the pancreatic solution instead of the
pepsin solution, and in Experiment 79 substitute
sodiimi carbonate solution 2 per cent, for the 0.5%
hydrochloric acid solution.

Experiment 83. Object : To test the action of pan-
creatic juice on fat.

Procedure: Into each of 2 test tubes put 10 c. c.
of whole milk and enough litmus powder to color the
milk a decided, but not dark, blue. To tube 2 add
2 c. c. of pancreatic juice. Put both tubes into a
water bath and keep them at 40® C; After a short
time, it will be noticed that the blue color of the milk
in tube 2 changes to pink. Why does it do so?

CHAPTER XXIII

THE CHEMISTRY OF ABSORPTION AND METABOLISBC

Changes that Occur in Food Substances during Absorption —
Nature of Metabolism — Composition of the Blood — Changes
that Occur in Food Substances during Metabolism — Some
Causes and Results of Defective Metabolism — The Fuel
Value of Foods — Food Requirements.

Absorption

The changes that occur in food substances during
absorption.— Of the substances formed during diges-
tion from disaccbarids, polysaccharids, proteins, and
fats, only monosaccharids are usually fotmd in the
general circulation. Therefore, it is thought that
during absorption and, probably, in the liver chemical
changes the opposite of those occurring in digestion
take place. These changes result in the transforma-
tion of the soap into fats and of peptones and amino
acids into blood proteins — the serum albumin or
globulin. The passage of these substances into the
blood IS thought to be partly due to osmotic pressure,
but both their passage into the blood and their re-
building are accomplished by the activity of cells in
the mucous membrane of the intestine. Whether
these cells form enzymes, or whether the enzymes
with which the food beca;ne mixed in the process of

4^ .

Absorption and Metabolism 405

digestion by a reverse' action aid in this synthesis,
are still debated questions.

Metabolism

Every living organism may be likened to a chemical
laboratory, whether it be plant or animal, whether it
be large and composed of millions of cells or so small
that it cannot be seen without the aid of a microscope;
for in the cells of all such organisms chemical reac-
tions are constantly taking place whereby the tissues
are built and repaired and» in the case of animals,
heat and energy are generated to keep their body
machinery in motion. The classification of such
processes in plants was mentioned in Chapter XVIII.;
those occurring in animals are spoken of as meidboU
ism. Some of the reactions occurring in metabolism
can be easily performed in any chemical laboratory,
but after a great many years of study, even the most
skillful chemists and physiologists have but an indefi-
nite knowledge of the nature of some of the processes.

Catabolism and anabolism. — The chemical reac-
tions of metabolism, such as hydrolysis and oxidation,
which result in the disintegration of complex sub-
stances into simpler compounds, are classed as catc^
holism and the changes are said to be catabolic (from
the Gr. kata-^down and metabole^ change), and the
synthetic changes in which simple substances are put
together to form complex compounds are classed as
anabolism and the changes are said to be anabolic
(Gr. ana ^ up and metabole^ change).

' A common characteristic of enzymes is that an accumulation
of the products of their action will check their activity and even
cause them to reverse the nature of their action.

4o6 Physics and Chemistry

Compositioii of fhe blood. — Since the blood is the
reservoir for the chemical supplies that the body tises
for the numerous chemical reactions constituting
metabolism, it may be well to recall its compo-
sition before going further with the study of the
reactions.

The constituents of the blood are usually classified
as follows:

Water

SoUds

Corpuscles

Proteins

Extractives'

Salts

(White
Red
Blood-platelets

Fibrinogen

Scrum globulin or paraglobulin

Serum albumin

Nitrogenous substances such as urea,

uric acid, creatin
Pats
Lecithin
Cholesterin
Glycogen
Glucose

1 Oxygen
Carbon dioxid
Nitrogen

Also, there are in the blood ferments, enzymes,
internal secretions, antitoxins, and similar substances.

The composition of the blood in the portal vein
differs at times from that in the other vessels because

' Substances, other than proteins, that may be extracted from
driod residue of blood by water, alcohol, or ether.

Absorption and Metabolism 407

it contains all the substances absorbed from the in-
testine and some of the^ the liver removes or changes
before they enter the general circulation. For instance,
glucose, over the amount necessary to provide the
blood with a content of about o.i or 0.15 per cent., is
removed by the liver cells and changed to glycogen,
which is stored chiefly in the liver, but to some extent
in the muscles.' Also, putrefactive products, such
as indol, that are absorbed from the intestine are
changed to substances less likely to injure the system
before they enter the general circulation.

Derivation of the blood constituents. — ^The con-
stituents of the blood, other than the corpuscles, anti-
toxins, and similar substances, represent: (i) food
matter absorbed from the intestines; (2) oxygen
taken from the Itmgs;' and (3) matter, useful and
otherwise, that has been absorbed from the tissues
and glands.

Fate of the food constituents of the blood. — ^There
is a constant osmosis of substances from the blood,
through the capillaries into the tissues, and this matter
is either used by the cells for their nutrition or build-
ing or else it unites with oxygen and is broken down,
just as fuel is when it combines with oxygen in a
furnace. The result of this oxidation is the same as
that which occurs in the furnace, viz., the production
of heat. In the body, some of this heat is used for
energy to keep the body machinery — ^heart, lungs,
etc. — in action as well as to provide the body with
power to perform its external work.

'After the death of an animal the glycogen and glucose in the
muscles and blood aie soon oxidized.

' This is contained principally in loose combination with the
hemoglobin of the led blood-cotpufldes.

4o8 Physics and Chemistry

Intennediate Stages in the Metabolism of Food

Products

Glucose, as already stated, is changed to glycogen
and as such stored in the liver, but in health the
blood maintains a constant content of about o.i to
0.15 per cent., and as it parts with its sugar to the
tissues the glycogen is reconverted to glucose. In
the tissues, the glucose (C6Hia06), it is thought, is
split to lactic add (C3H6O3). and then undergoes a
series of oxidations with the formation first of various
acids and finally of carbon dioxid and water which are
eliminated through the lungs. If more food is eaten
than the body requires for its heat and energy supply,
glucose can be changed to fat and stored as fatty tissue.

When metabolism of glucose is defective, as in
diabetes, much of the glucose does not undergo com-
plete oxidation and there is an acctimulation of glucose
and of adds in the body, and glucose is eliminated in
the urine.

Fat may be stored as part of the body fat; it may
be synthesized with other substances to form more
complex body constituents — such as ledthin — or, as
is in any case the final fate of fat, it is oxydized to
carbon dioxid and water and during the process yields
heat and energy. The stages through which fat
passes before it is completdy oxidized are but imper-
fectly understood. When its metabolism is defective,
diacetic add and acetone are formed.

The proteins that are eaten as food vary consider-
ably in their composition and many of them are very
different from body tissue, but, since they are aU
composed of different combinations of amino adds
and the combinations are parted in the process of

Absorption and Metabolism 409

digestion and in metabolism, the body is provided
with the same fundamental constituents as those which
compose its own substance and which its cells are
capable of putting together, not in the order in which
they were originally, but as they are needed for the
muscle tissue and other proteins of the body. Since
the proteins are the only foods containing these amino
adds, they are the only ones that can be used in the
body for the repair and building of its protein constitu*
ents. The molecules of protein not used for these
purposes are split to amino acids and these in turn are
split to form ammonia (NH3) and organic acid radi-
cals. The ammonia, it is thought, unites with carbonic
acid (COa+HjO), which is being constantly formed
in the course of metabolism, fonning ammonia car-
bonate. This, by a loss of one molecule of water,
leaves ammonia carbonate, which in turn, by a loss
of water, yields urea. This is excreted by the kidneys.

0«C Oa

Ammonia carbonate

NHa

0-C o

NH4

Ammonia carbamate
NH,

o./

NH,
Urea

4IO Physics and Chemistry

The organic add radicals left after the removal of
the ammonia group consist, like fats and carbohy*
drates of, COH and, like those substances, they may
be oxidized to carbon dioxid and water, yielding heat
and energy, or they may be synthesized to fat or
glycogen.

The nucleo-proteins — ^which are the characteristic
proteins of cell nuclei, both those of food and of the
human body — ^when metabolized, give rise to sub-
stances that are known as purin bases. These, on
further decomposition, yield uric acid. It is thought
that uric acid is formed both in the Uver and through-
out the tissues of the body. As the acid is formed,
most of it unites with alkaline substances, forming
salts — urates — which are excreted in the urine.

The formation of salts in the body. — Though adds
are being constantly formed in the body in the course
of metabolism, the body fluids, except the gastric
juice and the urine, are alkaline or neutral. This is
because the adds are either oxidized and thus broken
down to substances such as carbon dioxid and water,
which can be eliminated, or else they are neutralized
by tmiting with alkaline substances obtained from
food and carried through the body by the blood.
Many of the salts excreted in the urine, sweat, and
feces are formed within the body in this way.

Factors influencing metabolism. — That the many
chemical reactions which occur in metabolism can do
so at body temperature is due to the presence in the
tissues of various enz}mties, which are manufactured
by the body cells, and internal secretions carried
thither by the blood from the glands in which they
are secreted.

Results of defective metabolism.— As shown in the

Absorption and Metabolism 411

preceding paragraphs, broken-down body tissue and
also food substances that are not built into tissue go
through several stages of disintegration before they
are eliminated. The intermediate products, only a
few of which were mentioned, are principally adds
and nitrogen compounds. If, for any reason, meta-
bolism is defective, the final stages of disintegration
are likely to be delayed ajid abnormal compounds are
often formed, thus there is likely to be an accumu-
lation of more or less injurious substances within
the body.

Some causes of defective metabolism. — Diseases,
such as anemia, and conditions which prevent the
body getting its necessary amount of oxygen, will
result in defective metabolism, since many of the dis-
integration processes are due to oxidation. Condi-
tions of the tissues which retard enzyme formation,
or diseases of those ductless glands which are con-
cerned with metabolism, will interfere with it, as will
also disturbances of certain parts of the nervous
system, since metabolism and heat regulation, like all
other vital processes, are, both directly and indirectly,
controlled by this S3rstem.

Heat Value of Food and Food Requirements

The study of these things belongs to dietetics, but
a brief stuvey of them here may be of advantage.

How the heat value of a food is determined. — ^The
heat value of food is calculated and recorded in the
same manner as that of other substances as described
in Chapter III. It was determined by burning foods
in a form of apparatus known as a bonib calorimeter.
By this means it was fovmd that each gram of carbo-

412 Physics and Chemistry

hydrate eaten should yield to the body 4 calories;
each gram of fat, 9 calories; each gram of proton, 4

Fig. 69.

A Vaubtit of Calokiueter Used for AscEXTAunira

THE Heat Value of Poods.

calories. If proteins were as fully oxidized in the
body as they are in the calorimeter, they would have
a higher food value, but it will be remembered that

TAKEN rnOM THE REMR OF THE CHAM«ER.

1 -A DEVICE FOR THE REMOVAL Of THE KESPUtATORV
P>IIOOUCTR FROM THE RESPIRATIOH CHAMRERS.
(•IDE VIEW.)

Absorption and Metabolism 413

much of the protein leaves the body as comparatively
complex substances, urea and the like, which in the
calorimeter tmdergo oxidation.

Food requirements. — By the use of various forms of
calorimeters, by the examination of excreta by various
experiments, and by investigations of the amotmt of
food eaten by healthy individuals in different coun-
tries and engaged in various occupations, it has been
found that the amoimt of food that an individual
requires is dependent chiefly upon the rate at which
oxidation occurs in the body, and variations in this
are largely due. to differences in the muscula;r con-
traction that occurs. This, in turn, is dependent
upon such things as the mode of life, age, sex, climate:
for certain occupations and exercises entail more
muscular contraction than others; cold increases
musculajT contraction, as is shown by the phenomenon
of shivering, and it tends to induce an individual to
exercise and make active movements, while warmth
has the opposite effect; a strong person will expend
more energy in his movements than a weak person,
and a large person has a greater area of muscu-
lar surface to undergo contraction than a small
person.

As oxidation uses up the fuel and muscular con-
traction increases the rate of oxidation, the greater
the amotmt of muscular contraction an individual's
conditions and manner of living entail, the more
food will he require. It has been found, by the means
mentioned in the preceding paragraph, that a man
of average weight (about 59.5 kilograms — 155 pounds)
requires under differing conditions the following
amounts of food:

When at rest, enough to jrield 2000 calories.

414 Physics and Chemistry

When engaged in a sedentary occupation, enough
to yield 2700 calories.

When doing a moderate amount of muscular work,
enough to give 3400 calories.

When engaged in hard muscular work, enough to
give 5000 to 6000 calories.

A woman of equal size, engaged in an equally ardu-
ous occupation and expending an equal amount of
energy as a man, would require the same amount of
food, but as the average woman is rather smaller and
usually exerts somewhat less energy in her movements,
it has been estimated that women require about 0.8
the amount of food that men do.

Though children require less food than adults, they
need more in proportion to their size, because material
is required to build their bodies as well as to repair
waste and yield heat and energy. The following
estimate of the food requirements is one that is often
given:

A boy of 14 to

16 requires

about

1^500 to 3000 calories

" girl " 14 "

2200 " 2500 "

"child " 10 "

1800 " 2200 "

i« n u g II

10 "

1400 " 2000 "

II tt tt 2 •*

1200 " 1400 . "

II It II . II

2 "

900 " 1200 "

The comparative proportion in which the food prin-
ciples are used is about as follows: sufficient protein
to give about yi of the calories required, suflScient
fat to yield a like number, and sufficient carbohydrates
to make up the remaining %i of the calories. Thus
the food for a meaj intended to furnish 1000 calories
would be portioned as follows: Enough protein and
fat to give 200 calories each and sufficient carbohy-

Absorption and Metabolism 415

drates to yield 600 calories. As each gram of pro-
tein and carbohydrate furnishes 4 calories and each
gram of fat 9, this wotdd mean 50 grams of protein
(200-f-4»50), 22.2 grams of fat, and 150 grams of
carbohydrate.

CHAPTER XXIV

THE URINE AND URINE ANALYSIS

Origin of Waste Matter in the Body and the Channels through
which it is Eliminated — Quantity of Urine Voided — Com-
position of Urine — ^Foreign Substances sometimes Pound
in Urine, their Origin and Significance — Nature of Urine
Analysis — Methods of Determining the Quantity of Total
Solids in Urine — Tests for Acetone, Diacetic Add« Albumin,
Glucose, Indican, Bile, Blood, and Pus.

Origin of waste matter and the channels through
which it is eliminated. — As the restilt of oxidation
and other chemical reactions occurring in the body,
substances of no further use to the system are formed
and they must be eliminated. It is by the lymph
and blood that these substances are removed from
the tissues, and they'are extracted from the blood and
removed from the body by the kidneys, the sweat
glands, the lungs, and the intestines. Unnecessary
water, either that absorbed from the intestines or
formed in the body by chemical reactions, is elimi-
nated by the skin, kidneys, and lungs; the CO 3 passes
off chiefly through the lungs; the protein waste and
salts are excreted principally through the kidneys,
though to a slighte xtent by the skin, and small amounts
are excreted from the intestinal blood-vessels and pass
off with the feces, and when the kidneys are diseased,

416

The Urine and Urine Analysis 417

volatile protein matter may be exhaled from the lungs.
The kidne3rs are also the main channels for the elimi-
nation of foreign matter, such as drugs, toxins pro-
duced by bacteria, products of intestinal putrefaction
and defective metabolism. If there is any abnormal
exudate present in any part of the urinary organs
as the result of inflammatory conditions some of it will
be washed out with the urine, and if, as sometimes
occurs when the kidne3rs are diseased, the kidney cells
are not acting properly, substances that are normally
not extracted from the blood may be present in the
urine and, under such circumstances, there is likely to
be a smaller amount than normal of the usual waste
matter in the urine.

Thus, analysis of the urine is an aid in discovering
defective conditions in the intestines, defective metab«
olism, and diseased conditions of the urinary organs.

Quantity, Compositioni and Characteristics of Normal

Urine

Quantity. — ^The average amount of urine voided in
24 hours by a healthy adult is about 40 to 50 ounces;
by a child of

2 to 5 years, 15 to 25 ounces.

5 to 9 years, 25 to 35 ounces.

9 to 14 years, 35 to 40 ounces.

Even in health, however, the amount of urine
voided may vary very considerably. The principal
points to consider in deciding if difference in quantity
is normal or abnormal are the amount of liquid that
has been drunk and the quantity of water that haa

41 8 Physics and Chemistry'

left the body by other channels, for the system tends
to maintain its natural percentage of fluids and to
get rid of excess. Thus, if much liquid is drunk, more
will be eliminated than if only a small amount is taken,
and if an unusual amount of water leaves the body as
the result of vomiting, of watery evacuations from the
bowels, or of excessive perspiration, there will be less to
pass through the kidneys. In fever it is to be expected
that the amount of urine will be diminished, partly as
the result of the increased rate of evaporation of sweat,
due to the high temperature. When the nervous
system is depressed, as in shock, there may be either
suppression or retention of urine. In some diseases
of the kidneys, the secretion of urine is diminished,
and in diseases such as diabetes mellitus, diabetes
insipidus, and hysteria, secretion is increased; ner-
vousness also often causes an increase in the amount
of urine voided. Conditions causing a loss of fluid
from the body are usually characterized by excessive
thirst, which is another example of the body's endeavor
to maintain its normal fluid content. The sensation
of thirst is the result of the effect which the loss of
water from the body protoplasm produces on some
part of the nervous system.

Physical properties of urine. — Normal urine is a
transparent, yellowish or light amber-colored liquid
with a characteristic odor, a slightly alkaline reaction,
and a specific gravity of 1.012 to 1.030, 1.020 being
the average.

The specific gravity shows the relative proportion of
water and solid matter constituting the urine; the
greater the amount of solid matter present, the higher
will be the specific gravity. This and the means of
ascertaining the specific gravity of liquids were dis-

The Urine and Urine Analysis 419

cussed in Chapter III. Even in health there can be
considerable variation in the specific gravity of the
urine, for, as a rule, when only a small amount of
tuine is secreted as the result of loss of water through
other channels, as, for exa^aiple, through the sweat
glands, the urine will contain a relatively high per-
centage of solid matter and will have a high specific
gravity; if, on the other hand, a large quantity of
urine is excreted as the result of copious drinking or of
diminished perspiration the urine will be dilute and its
specific gravity will be low. In chronic nephritis,
however, even though the secretion of urine is dimin-
ished its specific gravity may be as low as 1.004, since
it is not only the water but also solid matter that is
not secreted in the usual amounts, and in diabetes
mellitus, though a large amount of urine is voided,
its specific gravity is high, due to the presence of
sugar.

The color of urine varies somewhat with its degree
of concentration, the color being deeper when the
amount of solid matter is in excess, and paler when
there is a large quantity of water. Any great differ-
ence in the color or transparence of urine is usually due
to the presence of foreign matter such as sugar, bile,
blood, drugs, etc.

The acid reaction characteristic of htunan urine is
due to the amount of foods that are eaten the end
products of which are acid. If urine stands for any
length of time it becomes alkaline as the result of the
conversion of the urea into ammonitmi carbonate due
to bacterial action. The same change may take place
in the urine while it is in the urinary organs when
they are diseased, and the urine is then alkaline when
it is voided.

Salts such as

«ff

420 Physics and Chemistry

The composition of urine. — ^The general composi-
tion of urine is about as follows:

Water 967. parts

SoUds:

Urea 14^30 **

(creatmin 1
xanthin I ,,

hypoxanthiQ | *

Mucus, pigments, ferments J

furates
sulphates

phosphates \ 8.770

chlorids
Gases, principally nitrogen and carbon dioxid.

The urea, which is the principal solid constituent
of the urine, is the form in which the greatest amount
of waste nitrogen derived from protein metabolism is
excreted from the body. The average amount excreted
daily, under normal conditions, is about 40 grams.
The quantity will be increased by a high protein diet
and decreased by a carbohydrate diet. It is increased
in diabetes and decreased in some diseases of the liver.

Creatinin. — Is thought to be formed in the body as
the result of the metabolism of its muscle tissue.

The uric acid and extractives such as adenin,
xanthin, and hypoxanthin vary in amount according
to the quantity of nucleo-proteins taken in the food,
therefore it is considered that they represent the
products of the metabolism of nucleo-proteins of the
body and of food. Practically all the uric acid pres-
ent in urine is in the form of salts (urates).

Traces of mucus are found in normal urine, but the
presence of large amounts is indicative of inflam-

The Urine and Urine Analysis 421

xnatory conditions of the urinary organs, especially
the bladder.

Abnormal Constituents of the Urine

The substances indicating abnormal conditions
which are most frequently found in the urine are:
Albumin, glucose, acetone, diacetic acid, indican, bile,
blood, casts, calculi, pus, and bacteria.

Albuminuria is the name applied to the condition in
which any form of heat-coagluable protein is present
in the urine, and th^ protein is designated as albumin,
though, as a rule, it is pliartly globulin. The con-
tinued presence of such protein in the urine is usually
due to disease of the kidneys or to abnormal pressure
changes in the renal blood-vessels, such as occurs in
diseases of the heart.

Glucose may be present in the urine temporarily
after the intake of a la^ge amount of carbohydrates,
especially sugars, and sometimes during pregnancy and
lactation, in concussion of the brain, and during con-
valescence from febrile diseases, but its continued
presence is always due to diabetes mellitus.

Acetone and diacetic acid are formed in the tissues
chiefly as the result of the defective oxidation of the
fatty acids arising during the metabolism of fats, but
sometimes they develop from certain amino acids
as the result of the defective metabolism of proteins.
These substances are found in the urine in advanced
stages of diabetes; when metaboUsm is retarded, as in
severe anemias; and when body tissue is metaboUzed
at an abnormally rapid rate as in starvation and in
long-continued febrile diseases. Diabetic acidosis and

4^2 Physics and Chemistry

coma are due to an accumulation of these substances
within the body.

Bile is present in the urine as the result of some
obstruction to its discharge from the liver or gall
bladder in consequence of which it is absorbed by the
blood.

The presence of pus is due to a suppurative inflam-
mation of some of the urinary organs.

Blood may be present in the urine as the result of
lesions in any of the urinary organs (this condition
is known as hematuria), or disintegrated blood corpus-
cles may be present as the result of hemolysis resulting
from a^y of the various causes of this condition,
e, £., the toxins of ccrtain> of the infectious diseases,
transfusion of blood, snake bite. This condition
is known as hemoglobinuria. In hematuria, the urine
has a characteristic smoky appearance. If the blood
comes from the bladder or genital organs it is likely
to be clotted.

Calculi or stones are the result of the precipitation
of some of the solid constituents of the urine. They
may form in any part of the urinary system and are
of various sizes and shapes. The precipitation is
usually the result of abnormal changes in the reaction
of the urine or the presence of foreign substances.

Casts consist of deposits of different kinds of sub-
stances, such a,s pus, blood, fatty matter, etc., that
have become hardened in the kidney tubules and are
washed out with the urine. They are called casts
because they retain the cast or form of the tubules in
which they were deposited. Their presence in the
urine, which is ascertained with the aid of the micro-
scope, shows some abnormal condition of the kidney
from which they came.

The Urine and Urine Analysis 423

Urine Analysis

A complete urine anal3rsis includes taking the spe-
cific gravity of the urine, testing its reaction, deter-
mining the total quantity of solids and the percentages
of the various solids, such as urea, extractives, and salts.
As a rule, nurses need to know only the tests for sub-
stances, such as albumin, glucose, acetone, and diacetic
add, which* in certain diseases, it is necessary to keep
track of from day to day, but a few other tests are
described here since it is interesting to know how
the data contained in the urine-analjrsis reports sent
from the laboratory are obtained.

The method of testing the specific gravity of liquids
was described in Chapter III. and the manner of as-
certaining their reaction was mentioned in Chapter
XIV.

I Methods of determining the total quantity of
solids. — Stir the specimen of urine, or else shake
the flask containing it, so that if any sediment has
precipitated it will become mixed with the liquid por-
tion of the urine. Then pour 25 cc, or other definite
measure, of the urine into an evaporating dish, place
this in a water bath over a flame, and let it remain
until the water of the urine has evaporated and the
residue is perfectly dry. Weigh the dish with the
residue and deduct the weight of the former from
the total. The amount remaining will be the weight
of the residue and will show the quantity of solid
matter in the amount of urine taken.

When only an approximate estimate of the total
solids is required, it is often calculated by multipl3ring
the two last figures of the specific gravity by 2.33.
Thus, if the urine has a specific gravity of 1.025, there

4^4 Physics and Chemistry

• •

wilt be 58.25 grains of solid matter contained in 1000
grains of the urine; since 25 X 2.33 « 58.25.

A test for acetone. — ^To 10 c.c. of urine, in a test
tube, add about 20 drops of concentrated NaOH and
5 drops of a 5% solution of sodium nitroprussid. If
acetone is present, the mixture becomes red and the
red changes to purple upon the addition of an excess
{i.e.f a larger quantity than there is of the mixture) of
glacial acetic add.

A test for diacetic acid. — ^Add, drop by drop, some
ferric chlorid solution to about 5 c.c. of the urine until
a precipitate ceases to form; filter the mixture, to re-
move the precipitate, and add some more ferric chlorid
to the filtrate. If diacetic add is present a deep
red color will develop. As other substances, such as
those excreted after taking salicylic add and similar
drugs, give the same reaction, the solution is boiled,
and if the color is due to diacetic add, it will dis-
appear, the add being thereby dianged to acetone,
but color due to the other substances will be per-
manent.

Albumin tests* — The heat test for albumin was de-
scribed on page 284. The Heller test, another of the
tests in common use, is as follows: Pour about 3 c.c.
of concentrated nitric add into a test tube and, with
a pipet, add, slowly, so as to avoid mixing the two
liquids, about 3 c.c. of filtered urine. A white ring
at the junction of the fluids shows] the presence of
albumin in the urine.

Tests for glucose. — Several of the common tests for
glucose were given in Chapter XVIII.

A test for indican. — Put about 4 to 6 drops of a 1%
solution of potassium permanganate into a test tube,
add between i and 2 c.c. of chloroform, then 10 c.c.

The Urine and Urine Analysis 425

of hydrochloric acid, and lastly 10 c.c. of the urine.
Invert the test tube two or three times so as to thor-
oughly mix its contents and allow it to stand for about
5 minutes. If indican is present in the urine, it will be
broken down by the hydrochloric acid and oxidized by
the potassium permanganate to indigo, which is dis-
solved in the dhloroform and gives a blue color, the
shade of which varies with the amount of indican
present, being very pale if there is only a slight
trace.

A test for bile. — One of the tests for bile very
commonly used is that known as Gfndin*s test^
which is as follows: To 5 c.c. of concentrated HNO3,
in a test tube, add 2 to 3 c.c. of urine, pouring
the latter down the side of the tube so that the two
liquids will not become mixed. If bile is present,
circles of various colors will form where the liquids
come in contact.

A test for blood (Heller's test). — ^Add enough
NaOH to 10 C.C. of tirine to make the latter decidedly
alkaline, boil this, and then let it stand. If blood is
present the a}kali converts the pigment into hematin
which is precipitated as a red deposit. As there
are other substances sometimes present in urine that
give the same reaction, filter the liquid and pour a
little acetic add over the precipitate. If this con-
sists of substances other than hematin, it will be
entirely dissolved; hematin may be slightly, but it
will not be wholly, dissolved.

A test for pus. — ^Before testing urine for pus, let it
stand tmdisturbed so that any sediment present will
fall to the bottom, then pour off as much of the
overlying liquid as possible without disturbing the
sediment, and to the latter add some concentrated

426 Physics and Chemistry

NaOH or KOH solution or some strong NH40H, If
there is pus in the sediment, it will be converted into a
viscid mass. If mucus is present, it will be curded,
but it will not assume the tough, gelatinous appearance
that the pus does.

GLOSSARY

Allojy a mixture of two or more metals of differing nature and
value.

Anhydridy an oxid which unites with water to form an add;
a substance formed from a compound, especially an acid, by the
loss of a molecule of water.

Anion, a negative ion.

Anneal, to render a substance less brittle by heating it to a
high temperature and then cooling it slowly.

Anode, the positive pole of an electric celL

Apposition, in contact with.

Arbitiarily, depending on the will of an umpire, judge, etc

Binary, composed of two elements.

Calcareous, pertaining to or of the nature of lime.

Cathode, the n^:ative pole of an electric celL

Cation, an electro-positive ion.

Caustic, corrosive.

Colloid, glutinous; resembling glue; a non-crystalline substance.

Commercial, as ordinarily furnished by dealers.

Conifers, trees that bear cones.

Decomposition, the separation of a substance into simpler
parts.

Deflsgration, sudden, rapid burning.

Deflected, bent from a straight line; turned aside.

Degeneration, changing from a higher to a lower form.

Dehydration, removal of water from a substance.

Deliquescence, see page a22.

Detttgent, deansmg.

Diaphragm, a partition, such as a membrane stretdied between
two cavities.

Dissociation, partial decomposition.

Ductile, pliant; easily stretched.

4^8 Glossary

Blmllitioii, the bubbling of a liqtiid caused by escaping gas.

Bifervetceiica, the bubbling of gas in a liquid.

Bffioreiceiicai see page 222.

ElectrolyBiSy chemic decomposition pixxluced by electricity.

Filamenti a fine thread or thread-like process.

Flltratey the liquid which passes through a filter.

Fofge, to form into shape by heating and hammering.

Fotey to melt.

Germinationt sprouting.

Habitati the natural locality of animals, plants, etc, in their
wild state.

Heliotherapy, the treatment of disease by exposing the body
to light.

Hepatitis, inflammation of the liver.

Hydrate, any compound of hydroxyl with a radical: a com-
pound containing water of crystallization. See page 233.

Hydrated, combined with water.

^ydrolysIs, chemic decomposition in which a oompotmd breaks
up as its molecules combine with one or more molecules of water.

](gnlte, to set on fire.

Incandescent, glowing, white with heat.

Interaction, diemical action in which there is double deoom-
position and combination.

Ion, an electrically chaxged atom; see Chapter VII.

Isomerism, see page 158.

Nascent, beginning to grow or exist; an active state.

Neutralize, to render inactive; to make neither acid nor alkaline.

Nitrogenous, pertaining to or containing nitrogen.

Polymer, one of a series of compounds of which the molecular
weights of the members of the series are in numbers which ara
multiples of each other.

Precipitate, to render a soluble substance insoluble and thus
cause it to oome out of solution and fall to the bottom of the con-
taining vessel; the solid thus precipitated.

Radical, see page 150.

Reaction, a diemical change.

Residue, that which remains after other substances have beea
removed.

Rhythm, harmonical; periodical.

[ Sadhnentation, settling to the bottom of a liquid.

Saoatadt notched like the edge of a saw.

Glossary 429

Temaiyi made up of three elements or radicals.

Tarpenes, hydrocarbons of the formula CioHi^; they are
derived chiefly from volatile oils and resins.

Vdatilei tending to evaporate rapidly.

Warp, the threads whidi extend lengthwise in the loom and
are crossed by the woof.

Welded, united by hammering or heating.

INDEX

Absorbents, nature and action

of, 237
Absorption, changes that occur

in tood substances during,

404
Acetone in urine, 421
Adds, amino, 276
Adds and hydrogen, 194
Adds, classification of, 193
Adds, derivation of prindpal

organic, 193
Adds, inoi^ganic, igd.
Adds, names of, 196
Adds, properties of, 195
Adds, tests for. 196
Adulteration of food, 375
Adulteration of soap, 230
Air, how heated, 87
Albumin, characteristics of,

279
Albuminoids, nature of, 280
Alcohol, action in system, 338
Alcoholic beverages, 334-340
Alcohols, classification of, 164
Alcohols, how synthesized from

hydrocarbons, 166
Alcohols, origin of the diffeieat

kinds used as fuel, 184
Aldehydes, nature and deriva-
tion of, 167
Alkalies, nature of, 197
Alkalies, reaction of, 197
Alkalies, reason for use in

deaning, 226
Alkalies, source of those fre-
quently used in cleaning, 227
Alkaloids and their salts, 203

Allotropism, meaning of, 161
Alluminium, qualities of and

methods of cleaning, 249
Anabolism, 425
Anhydrids, 195
Anhydrous, meaning of, 223
Amids, 283

Amino adds, nature of, 278
Ammonia, source of, 227
Artificial ice, 59
Astigmatism, 99
Atomic weigh^ 29
Atoms, definition of, 27

Bacteria, action in alimentary

tract, 395
Bacteria concerned in spoiling

food, 308
Bacteria in water, 210
Bacteria, why killed by heat,

bichlorid, etc., 285
Baking powders, 356, 357
Barley, 321

Barometer, invention of, 49
Bases and alkalies, differences

between, 197
Bases, names of, 197
Bases, reaction of, 197
Batteries, chemical, nature of,

107, 108
Batteries, electric, 113
Batteries, storage, 114, 115
Batters, methcxls of malcing

Ught, 2^
Beers and ales, 338
Benzoic add, test to detect to

food, 378

43X

432

Index

Birds, food value of, 31 1
Bleadung ageats, action of,

234-237, 263
Bleaching, chemistry of, 234
Blood, composition of, ^^06
Blood constituents, denvation

of, 407
Blues, different kinds of, 266
Blues, experiment to detect

iron in, 266
Bluing, nature of, 266
Boiling, effect of pressure upon.

Boiling, effect of specific

gravity upon, 54
Boiling, nature of, 51
Borax, source of, 227
Borax, test to detect in food,

378
Bone acid, source of, 227

Boric add, test to detect in

food, 378
Brass, 247

Breezes, land and sea, 81
Bronze, 247
Bunsen burner, experiment to

study, 6
Bunsen burner, nature of, 6
Burner, Argand, 187
Butter, 318

Butter, adulteration of, 382
Butter, renovated, 318
Buttermilk, 317
By-produd^ 154

Capillarity, cause of, 76
Capillarity in plants, 303
Capillaritv, nature of, 75
Carbohydrates, classification

of, 287
Carbohydrates, constituents

of, 287
Carbohydrates, experiments to

test the solubilities of, 349,

350
Carbon, different forms of, 160
Carbon, occurrence of, 160
Carbon oxids, i6z
Catabolism, 405

Cathode rays, nature of, 134
Cells, dry, iif

Cells, Galvamc or Voltaic, 1 10
Cellulose, digestibility of, 288
Cellulose, nature of, 288
Cereals, adulteration of, ^81
Cereals, composition ot, 320
Chang^ physical and chemi-

cal difference between, 35
Charcoal, origin and nature of.

Cheese, 318

Chemical action that occurs in

Galvanic cell, 11 1, 112
Chemical affinit^r, 36, 148
Chemical batteries, nature of,

107
Chemical changes, 35
Chemical formuks, definition

for, 151
Chemical formuls, different

kinds of, 152, 153, 159
Chemical reactions, agents

which promote, 147
Chemical reactions, nature of,

147
Chemical reactions, reason for,

148
Chemicals, list of, 19-21
Chemicals, points to remember

about, 12
Chemistry, definition, 26
Chocolate, 231
Circuit, making and breaking

of electric circuit, 1 11, 112,

Ii3> 122
Circuit, nature of electric

circuit, III
Cleaning, classification of sub-
stances used for. 224
Clotting of milk axid blood, 286
Clouds, nature and causes of,

62
Coagulation of proteins, 284—

286
Coal, nature of different kinds

of, 182
Coal, origin of, 181
Coal tar, origin and uses of, 163
Cocoa, 332
Coffee, 327-329

Index

433

Coffee, adulteration of, 381

Coffee substitutes, 329

Coils, induction, 122

Coke, origin of, 182

Color blindness^ 92

Color, causes of, 86

Color of bodies, origin of, 91

Color of transparent objects, 93

Colors complementary, 93

Colors, length of waves pro-
ducing different, 86

Colors, number of. 91

Colors, reason lor changes
tmder artificial lights, 91

Colors, reason for fading of,

Colors, why perceived, 92
Combustion, experiments to
discover the nature of, 177-

Combustion, surface, 188
Compounds, stable and un-
stable, 1^0
Condensation, nature and

causes of, 58
Condiments, nature and use of,
^ 32<-327
Conduction, experiments to

show heat, 77
Conduction, nature of heat, 77
Conductors, comparative value

of substances as heat, 78
Conductors, comparative value

of substances as electric, 106
Contraction, causes of, 71, 72
Convection currents, 80
Convection, nature of, 80
Copper alloys, 247
Copper, methods of cleaning,
^247

Copper, qualities of, 247
Copper sulphate, test to detect

in food, 380
Com, 321
Cotton, action of acids and

alkalies upon, 263
Cotton fibers, nature of, 262
Cream, ^18
Cream, how frozen, 47
Crustaceans, 313
Currents, seeElectxic

Deh3rdratiQn, 223

Deliquescence, 222

Dew, 61, 62

Dextrin, occurrence andnature,

290
Dextrose, see Glucose
Dialysis, nature of, 70
Diffusion of gases, experiment

to demonstrate, 66
Diffusion of gases, nature of, 65
Diffusion of fiquids, example 01,

66
Diffusion of solids, 67
Digestion, experiments on,

^.397-403

Digestion, nature of, 587
Digestion, products of, 396
Digestion, reason for, 387
Digestive juices, toctors in-
fluencing secretion of, J94
Digestive ;uices, nature ot, 389
Disacchands, classification of,
291

Distillation, destructive, 64
Distillation, experiment to

show, 212
Distillation, fractional, 63
Distillation, nature of, 63
Distilled liquors, 336
Doughs, methods of making
_ light, 354 '
Dressing in cotton and linen

fabrics, 271
Dyes, origin of, 272
Dyes, permanency of, 273-275
Dynamo, nature and uses o^

Ear-trumpet, 146

Edema, a cause of, 69

Efflorescence, 222

Eggs, composition of, 319

Eggs, experiment to study
coa^lation of, 346

Electric changes, kmds of, 103

Electric conductors, compara-
tive value of substances as.
106 ^

434

Index

Electric current, nature of, io6

Electric currents, alternating,

direct, induced, secondary,

132

Electric currents as source of

heat and light, 124
Electric currents, Galvanic

and Faradic, 122
Electric currents, how pro-
duced, 107, III, 122
Electric lights, 125-227
Electricity, derivation of name,

102
Electricity, physiological

action of, 13^
Electricity, static, 132
Electricity, theories r^;arding

nature of, 104
Electrification, experiments to

show nature of, 102
Electrolysis, nature of, 108, 109
Electromagnets, 113, 121
Electromotive force, 127
Electroplating, nature of, 116
Elements, number and condi-
tion of, 29
Elements, table of, 30-35
Elixirs, 336
Enamel ware, 244
Energy, definition of, 40
Enei^gy, different kinds of, 41
Energy, law of conservation

of, 38
Enzymes, nature and action of,

390
Enzymes, table showing action

of, 392
Equations, nature and ptupose

of, 154
Esters or ethereal salts, 204
Ethane, nature, source, and

derivatives of, 164-165
Ether waves, effect of different

kinds of matter upon, 88
Ether waves, nature of, 85
Evaporation compared with

vaporization, 55
Evaporation, factors which

influence the rate of, 56
Evaporation, why it causes

cold, 57

Expansion and oontractioa of
water, peculiarities of, 72

Experiments, see Index of
Experiments

Extractives, 283, 311

Fading of colors, 92, 267, 274
Far-sightedness, 98
Fat, metabolism of, 408
Fats, chemical composition of,

204
Fats, classification of, 296
Fats, function in body, 297
Fats, nature of, 296
Fermentation, 359, j68, 369
Filtering, method of, 15, 211
Fire-extm^sher, 180
Fish, classification of, 312
Fish, nature and nutritive

value of, 312
Flame and incandescence, 179
Flame, Bunsen, 8
Flame, oxidizing, 10
Flame; roducini, 10
Flame, study of, 7
Fluorescence, nature of, loi
Fluoroscope, nature of the, 136
Fog, 61, 62, 63
Food, adulteration of, 375
Food, causes of spoiling, 365
Food, conditions conducive to

spoiling, 370
Food cycle, 305
Food, now to prevent spoiling,

371-374
Food material, classification of ,

276
Food material, origin of, 301
Food preservation, 370, 374
Food requirements, 413-415
Foods, classification of plaiit»

320
Foods, com(>arative digesti-
bility of animal, 308
Foods, table of average com-
position of. 340
Formaldehyd, test to detect, in

food, 379

Index

435

Pormals for some common
compounds, I54-I57. '59

Fonnuke, structural, 159

Frost, nattire and cause of, 62

Fruit, 324

Fruit juices, unfermented
beverages niade from, 334

Fuel, cla&fication of material
used for, 181

Fungi. 325

Fuses, nature and use of, 130

Gas, acetylene, 189

Gas, coal, 187

Gas, comparison of terms

vapor and, 39
Gas, compressed, 189
Gas, gasoline, 189
Gas natural, 188
Gas, water, 188
Gaseous fuels, different kinds

of, 186
Gasoline, origin and fuel value,

185
Glass, cleaning, 254

Glass, composition of different

kinds of, 253
Glass tubing, bending, 13
Glass tubing, drawmg to a

point, 14, 15
Glass, why it oreaks if heated

or cooled ouickly, 72
Globulins, oiaracteristics of,

279
Glucose, metabolism of, 408
Glucose, nature and occurrence

Glucose, tests for, 294, 296,
398, 400, 403 ^

Glutenms, nature of, 280

Glycerin, how made syntheti-
cally, 166

Glycerin, how usually ob-
tained, 220

Glycerin in fat, 297

Glycerin in soap, 230

Glycerin soaps, 232

Glycogen, occurrence and
nature of, 290

Glycoproteins, 281
Gums, 291

Hail, 63

Hearing, mechanism of, 141

Heat capacity of different

kinds ot matter, 44
Heat-conducting power of

different kincb of matter, 78
Heat conduction, 78
Heat, definitions of, 41
Heat, difference between

amount and degree of, 43
Heat, effects of, 42
Heat of fusion, 45
Heat of fusion, recovery of, 47
Heat, latent, 4^
Heat, latent, of steam, 46
Heat, means of transmission.

Heat, nature and cause, 62

Heat, reflection of, 92

Heat, relative heat of bodies.

Heat, retention of, 87

Heat, sources of, 42

Heat, specific, 43

Heat value of foods, 411

Heat, value of high heat capa-
city of water, 44

Hemoglobin, 282

Hemo^^ experiments to
show, 69

Hemolysis, nature and causes
of, 69

Histones, 281

Honey, composition of, 320

Hormones, nature and action

of, 391
Humidity, absolute, 61
Humidity, effect on health, 61
Humidity, meaning of term, 60
Humidity, relative, 61
Hydration, 222
Hydrocarbons, how obtained,

162
Hydrocarbons, nature and

classification, 161

436

Index

Hydrocarbons, physical condi-

Hydrochlonc add, 194, 195
Hydrochloric acid, action in

digestion, 39a, 394
Hydrolysis, 388
Hydroxids, 196
Hypennetropia, 98
Hypotheses, at«nic, 38
Hypotheda, definition td, 38

Incandescent gas ushts, 187

Induced currents, tee Electric

Induction coils, 133

Inultn, 391

Iron, gajvanized, 343

Iron, methods of deaning, 345

Iron rust, 339

Iron, vaneties of, 343-343

330, 339, 354
Kinases, action of, 391
Kindling temperature, 174
Koumiss, 317

Laboratory maxims, 13

Laboratory methods, 13

Lactose, 393

Lakes, nature of, 373

Law of Boyle, 39

Law of Charles, 39

Law of conservation of energy.

Law of conservation of matter.

Ledthins, nature and functi<m

of, 397
Leathoproteins, 383
Legumes, 323

Lenses, different kinds of, 99
Levulose, 394
7 ' ' ' -c, 137

insen, 94

xwidesceot, 135

iflection of, 89

fraction of, 95

g, nature of, 134

nature of, 183

action of adds and

s upon, 363
Linen fibers, 363
Liquefied gases, 58
Liquid fuels, classification of,

184
Liquors, distilled, 330
Liquors, malt, 337

Magnetism, cause of, i3o

Magnetite, IiS, iiq

Magnets, nature of, 118

Mi^ets, properties of, i30

Malt, 331

Maltose, 393

Marble, experiment to study
the effect of acids and alka-
lies upon, 351

Mariner's compass, 119

Matter, itature of, 36

Matter, states of, 37

Matzoon, 317

Measurement of electricity, in-
struments used for the, 130

Measurement of electridty,

with, 137-130

Measuring, 18

Meat, factors which influence
the digestibility of, 309

Meat, faults of cooking, 347

Meat, structure of, 310

Megaphone, 146

Metabolism, causes of defec-
tive, 411

Index

437

Metabolism, factors influenc-
ing, 410

Metabolism, nature of, 405

Metabolism of food products,
408

Metabolism, results of defec-
tive, 410

Metal, tarnish of, 238

Metals, experiments to show
the action of adds, alkalies,
etc., on, 2i^o

Metals, requirements of clean-
ing material for, 339

Metastasis, 302

Methane, nature, sotm^ and
derivation of, 164

Microscope, principles of, 98

Milk, adulteration of, 383

Milk, certified, 314

Milk, composition of, 313

Milk, dessicated, 317

Milk, digestibility and nutri-
tive value of, 313

Milk, pasteurized, 315

Milk, sterilized, 316

Mineral matter in food and
the human body, 298

Molds, exi>erimcnts to study
the multiplication of molds,
366

Molds, nature and require-
ments of molds, 365

Molecular motion, 28

Molecular weight, 30

Molecules, demiition of, 26

Monosaccluuids, 293, 294

MoUusks, food value of, 312

Mordants, nature of, 273

Myopia, 98

Nearsightedness, 28
Neucleoproteins, 281
Neutralization, experiment to

demonstrate, 198
Nickel, nature and method of

cleaning, 246
Nitrogen, how obtained by

plants, 304
Nitrogenous foods, see Protein

Non-nitrogenous compounds,

283
Nuts, 325

Oatmeal, 321
Oil, adulteration of, 382
Oils, essential or volatile, 296
Oils, fixed, 296
Old-age sight, 98
Oleomaigarin, ^18
Organic and inoiganic sub-
stances, differences between,

158
Oiganic chemistry defined, 158
O^osis, experiments to oe-

monstrate, 68
Osmosis, nature of, 67
Oxidation and combustion,

nature of, 174
Oxidation, difference between

the oxidation of compounds

and elements, 176
Oxidizing compotmds used as

bleaches, 235
Oxids, nature of, 179
Oxids, uses of, 180
Oxygen, action in bleaching,

235
Oxygen, experiments to study

the nature of, 170-173
Oxygen occurrence of, 169
Oxygen physical and chemical

properties of, 173

Painted surfaces, methods of

cleaning, ^56
Paints, nature of, 255
Peat, origin and nature of, 183
Pectin, nature and use of, 291 ,

362
Pectin tests, 363
Petroleum, source and uses of,

163
Pewter, nature of, 250

Phonograph, 142

Phosphoproteins, 282

Phosphorescence, nature of,

lOI

438

Index

PhotosTnthesis, 301

Plant life, effect upon the
atmosphere of, ^05

Plants and animsds, classifica-
tion of substances compos-
ing, 276

Plants, how they grow, 301-
306

Platinum, 251

Polarity, nature of, 118

Polarization, nature of, 100

Porcelain, 253

Potassium, source and uses of,
227

Precipitation, difference be-
tween coagulation and, 286

Presbyopia, 98

Preservatives, classification of

' food, 374

Pressure, atmospheric, 49

Pressure, causes other than
altitude that produce change
in atmosphenc, 50

Pressure, comparative relation
of changes in heat and, 48

Pressure, effect on boiling
point, 51

Pressure, how increased, 48

Printing, difference between
dyeine and, 272

Prism gmss, 100

Protamines, 281

Proteins, alcohol soluble, 280

Proteins, classification of, 278

Proteins, coagulation of, 284,

346
Proteins, composition of, 277
Proteins, conjugated, 281
Proteins, derived," 282
Proteins, digestion of, 388, 392
Proteins, experiments to test

the effect of heat and add

upon, 345-347 , , ,
Proteins, function of food, 283
Proteins, metabolism of, 408-

410
Proteins, precipitation of, 286
Proteins, simple, 279
Proteins, solubilities of, 348
Proteins, tests for, 270, 283,

384, 398, 401, 402, 403

Radiation, nature of, 84

Radicals, 150

Radio-rays, nature and actaoa

« o^» 137

Rain, cause of, 62

Rainbow, 100

Reagents, list of, 19-21

Reduction, 10, 235

Reflection, nature of, 88

Reflection, result of the xe*

flection of light, 89

Refraction, cause of, 96

Refraction, difference in, 97

Refraction, nature of, 95

Rheostat, nature of, 132

Rice, 322

Roots and tubers, 322

Rye, 322

Salicylic add, test to detect In
food, 377 .

Salts, dissociation of, 200, 202

Salts, ethereal, 204

Salts, experiment to show dis-
sociation, 200

Salts, formation, 200, 410

Salts, function in body, 298

Salts, naming of, 202

Salts, nomuu, add and basic,
202

Salts, occurrence^ 199

Salts, source of, m scnl, 304

Salts, tests for, 299

Sap, forces causing dxx^ulatioa
m plants, 303

Sap, nature and purposes of»
302

Saponification, how caused,
205, 229

Sapjonification of fats in diges-
tion, 388

Scouring agents other than
soaps and alkalies, 234

Scounng powders, composition
of, 233

Secretins, nature and action ol|

39<

Index

439

Silk, acttoa of alVaKwi, adds,

heat, etc., on, 265
Silk, artificial, 263
Silk fibers, nature of, 263
Silver, qtialities of and methods

of deaning, 249
Siphonage, 74
Smoke, 177
Snow, cause of, 63
Soap, test for fillers in, 233
Soap, test for free alkalies in,

233

Soap, test for rosin in, 232

Soap, test for unsaponified fat

in, 230
Soaps, how made, 220
Soaps, reasons for mfferences

in, 230
Soaps, substances added to*

2^0
Sodium, sources and uses of,

228
Solder, nature of, 250
Solutions, definitions for terms

used in connection with,

191, 192
Solutions, list of solutions

used for experiments, 19-21
Solutions, nature of matter

used for, 192
Spedfic gravity, effect upon

boiling point, 54
Specific gravity, how ascer«

tained, 54
Spedfic gravity, nature of, 53
Spedfic gravity of urine, 418
Spedfic gravity, value of

knowle(^e of, 54
Spices, origin and food value

of, 326
Solvents, nature, origin and

uses of those commonly

used in cleaning, 224
Sound, difference oetween

sound and light waves, 138-

140
Sound, how transmitted, 140
Sound, origin of, 136
Sounds, reasons for differences

in. U3
Stains, removal of« 267-270

Starch, comparative thicken-
ing power, transparency and
flavor of, 353

Starch, digestion of, 392, 399

Starch, experiments to test
the action of heat and water
on, 351

Starch, properties of, 289

Starch, test for, 289, 400, 403

Steel, 243

Stethoscope, 146

Sublimation, 65

Sucroses, 292

Suction, nature and common
uses of, 74

Symbols, 29

Tarnish, nature of, 238
Tarnish, requirement of agents

for removal of, 239
Tea, 330

Temperature, kindling, 174
Test, acetone, 424
Test, adds, 196
Test, Babcock, 383
Test, bile, 425

Test, blood (Heller's test), 325
Test, dextrin, 290
Test, diacetic add, 424
Test, Halophen, 382
Test, indican, 424
Test, lactose, 293
Test, pectin, 363
Test, pus, 425
Test, spoon, 382
Test, starch, 289, 398, 400, 403
Test, sucrose, 292
Test tubes, manner of holding,

II
Test tubes, numbering, 1 1
Tests for adulterants in food,

377-386
Tests for adulterants m soap,

232-234
Tests for albumin, 424
Tests for dextrose or glucose,

294-296, 398. 400, 403
Tests for monosaccharids, 294,

296, 400, 403

440

Index,

Tests for proteins, 383-284,
398, 401, 402, 403

Tests to determine the pres-
ence of various salts in tood,
etc., 299

Tests to distinguish between
cotton, ]inen, silk, and wool
fibers, 270

Textile tests, 170

Textiles, expeiiments to study
the nature of, 261

Textiles, experiments to test
the action of adds, alkalies,
etc, on different, 263

Textiles, mercerized, 263

Textiles, removal of stains
from, 267

Textiles, some practical appli-
cations of knowledge of
effect of adds, etc., on, 265

Textiles, source of, 260

Thermometer, how made, 73

Tin. qualities of and methods
ot cleaning, 246

Transformers, value of, 131

Urine, abnonnal constituents

of, 421
Urine analysis, 423-426
Urine, composition of, 420
Urine, physical properties of,

418. 419
Urme quantity voided, 417
Utensils, precautions neces-
sary in tne use of chemical,
10, II

Vacuum, 7,

Valence due to electrical

chaiges, 149
Valence, nature of, 148
Vaporization, amount of heat

required for, 46
Vaporization, nature of, 40
Varnishes, nature of, 2^6
Vegetables, classification of,

32a

V^etables, green, 323

Ventilation, 81

Visible, why objects are, 89

Waste matter, origin and

elimination 01, 416
Water, bacteria in, 210
Water, carbonated, 333
Water, dty supply, 206
Water, composition of, 209
Water, country supply, 207
Water, difference between

hard and soft, 214
Water, expansion and contrac-
tion of, 72
Water, experiments to show

the softening of, 219-221
Water, fordgn substances in,

209
Water, freezing of, 72
Water, functions in the body,

300
Water, hard, 219
Water, mechanically endosed,

221
Water, mineral, 214, 333
Water, objections to me use of

hard, 217
Water of crystallization, 221
Water, purification of, 210-212
Water, softening of, 215-217
Waxed floors, how to wax and

dean, 257, 258
Wdghing, 17
Weights and measures, tables

of, 22-24
Wdsbach mantle, 187
Wheat, 320
Whey, 317
Wind, 80, 81
Wines, 335

Woods, classification of, 183
Woods, nature of different

kinds of, 183
Wool, effect of bleaching

agents upon, 236, 264, 265
Wool fibers, effect of heat,

adds, and alkalies on, 264
Wool fibersi xiatuxe of ^ 263

Index

441

X-Rays, nature and action of,

Yeasts, food requirements of,
370

Yeasts, nature of, and action,
35^-362

Yeasts, result on food of in-
fection by, 368

Zinc, 244

Zymogens, nature and action
of, 391

INDEX OF EXPERIMENTS

MUMBBt Objed of Experiment ^^^b

I. Study of the Bunsen burner 6

2 & 3. Study of the Bunsen flame 9

4. Demonstration of the production of heat by

chemical reactions 42

5. Demonstration of the effect of atmospheric pres*

sure upon boiling point 51

6. Demonstration of the effect of specific gravity

upon boiling point 5A

7. Demonstration of the diffusion of gases 60

8 & 9. Demonstration of osmosis 67, 6S

10. Study of heat conduction and convection 77

11. Study of electrification 102

12. Demonstration dt magnetic fields and lines of

force X2X

13. Stud^ of (i) a method of reducing a compound

to Its constituent parts; (2) a method ot liber-
ating a gaseous element from a compound and
collecting the gas; the properties of oxygen;
(4) the use of a catalyzer 171

14. Study of the results of the oxidation of an ele-

ment 172

I5-X8, Observation of the nature of combustion I77''i79

19. Demonstration of neutralization 198

20. Decomposition of salts 20X

21. Demonstration of the effect of distillation as

compared with filtration 212

22. Study the differences in hard waters 219

23. To show some methods of softening water 219

24. To estimate the amount of soda necessary to

soften water 220

25. To observe the difference in the manner in which

water of crystallization and mechanically en-
closed water escape from a compound when
the latter is heated 221

26. Observation of efflorescence and deliquescence. . . 222

27. Tests for soap adulterations. 231-233

443

444 Index of Experiments

BXPBRIMBIYT

NUMBSR TA

28. To Study the effect of acids and alkalies upon

metals 240-341

29. Demonstration of the effect of acids and alkalies

upon marble 251

30 & 31. To study differences in the composition of tex-
tiles 261

32. To test the action of acids, alkalies, and bleaches

on textiles 263

33. To note the effect of dry heat on wool 264

34. To see if iron is present in a blue 266

35~37' To distinguish different textiles 270

38. To determine the amount of dressing in a fabric. . 271

39. To test color-fastness of material 273

40. To note the effect of the loss of calcium salts dE

milk on clotting 314

41. To test the comparative effectiveness of the

holder and flash methods of pasteurization 315

42. To discover the temperature at which albumin

of egg, milk, etc., will coagulate 345

43. To test the effect of salt and acids upon protein . . 346
44-46. To see if the common forms of carbohydrates

are soluble in water 349

47. To see the effect of heat and water upon starch. . . 35 1

48. To note differences in taste, transparency, etc.,

of different starches 352

49. To study the effect of heat and of heat plus acid

on starch 353

50. To observe the effect of heat and add on sugar. . . 353

51. To study the action of baking powder 356

52. A test to detect the presence of alum in baking

powder 357

53. To determine the comparative fermentating

power of different yeasts 360

54. To see why sugar is added to dough in bread

making 361

55. To prove that it is the same gas which is ob-

tained by the use of baking powders and of
yeast 361

56. A test for the presence of pectin 363

57. To study conditions that favor the growth of

molds 366

58-65. Tests for food adulterants. 377-386

66-73. Experiments on digestion 399~*403

Unnalysis. ^ . .423-426

APR 2 6 1920

Quiz Book of Nursing
for Teachers and Students

Amy Elizabeth Pope

Joint Aitlmr of '*Pnictical Nnrtiiig*' and **ffooontlili

of Diototics**

Thirza X. Pope

Together wMh Chapters on Vlsltiiiff Nnrrfng

Bf lUrgarot A. Bewlej, R. N.

OndBBM of PnrigrtariaB ScImoI eC Nurfng. and of tiM SIohm Urtwiilty

Hoipital, N«« Totk CIcys iMrractorm VWdac ud Dinrid

NoaNf ia PmbytMaa Hotpica], New Yoik City*

Hospltel Phumlngt Construction, and Equipment
By Bertnuid B. Taylor, A. A. L A.

Hospital Boolc-lceepinff and Statistics

By Frederic B. Morlok

Cbkl Ckilt IB the Prasbytcriaa Hospital, Naw Yotk Ol^

Third Ediiion^ Revised and Enlarged lUustraUd
Uniform with "Practical Nursing'*

TUi book ftioui to be iisefol, in the moit practical way » to
nurses who teach, and to those who are studying under thexn. It
is, in large part, a quiz book, offering in the form of terse ques-
tion and answer essential information on jl wide range of sabjects
—the information that is essential from the nnrseVi standpoint.
Those who teadi will find these questions oi assistance when the
time they have to devote to preparation for their class work is
limited ; and those who are taking oonnes will find the book a
great hdp ; especially when studying for examinations.

A History of Nursing

By Lavinia L. Dock, R.N.

and

H. Adelaide Nattingt R.N.

4 voU* Sua, Bach fully iUustratmd

VoU. I n^ n. Th« Evolvtlom of th« Hclhoda of Cm* fw
thtt Sick from th* EwllMt TIbm to th« PovadattoB off tho
First EmiUak aad AMwIoaB Traialiitf SchooU for Nvrsoa.

Two voUi, with So IliuMtrutionM

Vols. Ill aad IV. Th* Story off Mod«ffB N«rstatf. ProMotla^
•B AcGOont of the Dev«lopiii«nt In Various Goantries ol
ths Sdoace of Traiaed Nurslad with Spadal Baf araoca to
tba Work of tka Past Thirty Yaars.

Two vols., with 75 illustrations

Bsglnniaff with ths eartteit sytlUble lacords of laiiitaiy oodss
which wsro hoilt up into liealth religions, and coming down through
tho sfas wfaerevor the care and leecne of the lick can he traced*
through the pagan dTllizations, tlie early Christian works of mercy*
the long and glofions histoiy of the religions nursing orders, military
nursing orders of the Crusades* the secular communities of the later
Middle Ages, and the reviTal of the deaconess order wUch cul-
minated in the modem reviyal under Miss nightingale* this history
Is the most serious attempt yet made to collect the scattered ncorda
of the cars of the sick and bring them all into one unified and sympa-
thetic presentation.

The story Is not told In a diy technical fashion* but pcussnts its
pictures from tho standpoint of general human interest in s subject
which has always appealed to the sympathies of men*

Both Ifiss Nutting and Miss Dock are wril known in the nursing
world; Miss Nutting* as one of the foremost educators in hospital
woik* who* as the head of the Johns Hopkins Hospital trsining
school* has so distinguished herself for practical work that she has
been called to Columbia University to take the chair of Institntianal
Management* and her collaborator as s well-known woiksr for
organisation and progress* and who* as the secretary of the In-
ternational Counctt of Nurses* has already written much on nursing
and hospital conditions.

The history is amply illustrated* and contains a copious Ubiiof*
raphy of nursing and hospital history.

Nnr York Q. P. Putnain*s Sons lohOm

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