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/■ 



THE 

CABINET 

OF 

NATURAL PHILOSOPHY. 

CONDUCTED BY THE 

REV. DIONYSIUS LARDNER, LL.D. F.R.& L.&E. . 
M.R.LA. F.R.A.SL F.L.a F.Z.& Hon. F.C.P.& Ac &c. 

▲BSISTID BT 

EMINENT LITERARY AND SCIENTIFIC MEN. 



CHEMISTRY. 



BT 



MICHAEL DONOVAN, ESQ. M.R.LA. 



LONDON: 

PRINTED FOR 

LONGMAN, REES, ORBfE, BROWN, GREEN, & LONGMAN, 

PATBRN06TBR.R0W ; 

AND JOHN TAYLOR, 

DPiPBft GOWBR 8TRBBT. 

1832. 



London : 
Printed by A. Se B. Sptttiswoode, 
New-Street-Square. 



/ 



/ ^ '< 



/-t 



THE 



CABINET CYCLOPEDIA. 

CONDUCTED BT THE 

REV. DIONYSIUS LARDNER, LL.D. F.Ra L.&E. 
HRLA. F.R.A.a F.L.a FXSL Hoa.F.CLFa kc kc 

ASaiSTSB BT 

EMINENT LITERARY AND SCIENTIFIC MEN. 



j^atural pgilo^opgii^ 



CHEMISTRY. 

BT 

MICHAEL DOKOVAN, ESQ. M.R.I.A. 



LONDON: 

PBIMTBD FOR 

LQNOMAiN, REES, ORME; BROWN, OREEN, 9t LONGMAN, 

PATKUMOtTBR-ROW ; 

AND JOHN TAYLOR, 

VFPBB OOMTBR 8TRBBT 



jma 



THE NF.W/ «0B£ 

PUBLIC U]»SAtr| 



I. *. w W V. 









». fc k b 



V 1. ». 






4, »• • fc k »• 

cue ''♦••' »■ •■ 



ADVERTISEMENT. 



The author of this treatise wishes it to be stated, 
that the following paragraphs in the original MS. 
have been expunged by the editor ; and the para- 
graphs conunencing with the words, '^ That water," 
&c. p. 66^ and ending with the words " surround- 
ing air, ascends,'* p. 67., have been substituted by 
him. 

"Another fact of the same tendency is the follow- 
ing : — If two flasks — one containing water, and 
the other containing water holding some common 
salt dissolved — be both exposed to the air when it 
is below the freezing point, with a thermometer im- 
mersed in each, the temperature of both flasks will 
sink to 32°: the salt water will continue to sink 
until it is much below the freezing point of pure 
water, and, on account of the salt, it will not freeze : 
the pure water, as soon as it arrives at 32°, has a 
tendency to freeze; but it cannot do so without 
first parting with that caloric which is the cause of 
its fluidity. Accordingly, instead of cooling below 
S2°, as the salt water did, it remains steadily at 
32°, and, at the same time, freezes; for the con- 
cealed heat, now extricated, has become sensible, 
and consequently keeps t|ie ice at that temperature ; 
although, but for this cause, the tempexalwx^ t(v>\%\. 

A3 



ADVERTISEMENT. 

have sunk in the same manner as that of the 
water did, 

■' That water does give out caloric in freezing, 
be proved by another striking experiment, — 
two thin glass vessels be procured, equal in e 
respect : let a little pure water be poured into 
and over the water a little olive-oil ; let an c 
quantity of oil, without any water, be poured 
the other ; and let both glasses be exposed td 
■ame temperature, below 32°. It will, in e 
time, be found that the water has frozen ; thai 
oil above it is still liquid, although the oil in 
glass which contains no water is irozen : and 
reason is, beeause the water, m freezing, gave 
■0 much heat as kept the oil liquid untU that su 
was dissipated." 



CONTENTS. 



PART I. 

SUBYET OF CREATION. 

CHAP.;I. 

IMTRODUCTION. - Page 1 

CHAP. 11. 

ATTRACTION OF GBAYlTATIOy. 

Quantity, of Matter {in Bodies, of equal Volume variable. * Specific 
Gravity. ..•....-•5 

CHAP. III. 

ATTRACTION OF COHESION. 

I>>vui<m of Masses of Matter. — Infinite DivisibiUty.— Practical Divi. 
>ibility.« Solids, Liquids, Airs or Vapours.— Cohesion of Liquids.— 
CrystaDisation. . . • • - - 11 

CHAP. IV. 

ATTRACTION OF AFFINITT. 

Affinity : Prod's of iu Existence. — Comlnnation. — > Distinction between 
Affinity and Cohesion. — Mechanical and Chemical Combination.— 
Affinity a general Property of Matter.— Limits to its Operation. — Its 
Energy is diflbrent in different Bodies. — Decomposition. - - SO 

CHAP. V. 

HEAT OR CALORIC. 

^^^Nsive Quality in Matter oppmed to Cohesion.— Theory of Boscovich. — 
Caloric the Cause of the Sensation of Heat — Heat discoverable in all 
^tter: experimental Prooft. — Effects of Heat: Expansion and Con. 
tnctioa— Heat suqiends Cohesion: produces Liquidity, and the 



^H Bunnu state -Cobe 

Water.— Spedflc Heal, 
Heai-Cup.*Ui^ rf 


w 

CONTBNTB. 

He Fuiion of Ice and boi 

,—Theoriei of Black ai>d 
BwUea to conduct Heat 

CHAP. VI. 


ffiog of Water" and it* 
and die Congelation a^ 

L— RadiaCion al Hat. 
Page ST- 


Produced by HemL — I 


ion»iOi Heat. — tU Chemical Influence. — Pti.- 
™ic] Rayi. — SuppoKd manpelic Influence. 91 




CHAP. VII. 




COKF 


Cn-DTION OF TBE OUT 


.E. 




^SEcr.i. 




OfAtr—ItiEUutldtj.^ 
and AiotK— ComblDit 
— Oildea,— BiliDoeo 


height, and Prcsnire-ll. 
SECT. n. 


I Bnolutioa into Oxygen 
— Acidity.- Nitric Add. 


Water, >t< KaoluHon ]i 
Neutialltj,-Mt..- 


nlo Hydrogen and OiyBSi 
Au.moqia, — VolalUily. 


1, — Rmompmitton fttini 
. A«,.e.-AlkaUI.lty-- 


Add! lod A1ka1iei,~£anhi.— Sipphire.— Mum 

— Emerald. — Gliicina, — Hyacinlh— Zireooia. 

— Lima — Cutmnate of flarjti.- Ciriionatc i 
— Eutlil are meUlIk Oxides. — Potidi, Soda, 

^^ 0;dde. — Sulpbirric Acid. — Muriatic Acid.- 


lte Mlnerali. — Minaral 
lina.- Amcthyrt—Silitm. 
— Gadollnile.— Vtuda.- 
.fStrontia.-Magnetia. 

-Chlotint-Iodine.- 


■ 


SECT. IV. 






OUil>»ED ffrmtCTUMS. 







CONTENTS. IX 

PART II. 

ABRANGEMENT ASB EXAMINATION OF THE JEATEBIAL8 

OF CREATION. 

CHAP. L 

XUHBIITS OR SfXPLK SUBSTANCES, AND THXIB IMMEDIATE 

COMPOUNDS. 

SECT. L 

OXTOEEf. 

^ode Of Preparatioii.-- Mode Of ooUectliigGAiM.-- Lutes. . Page 133 

SECT. II. 

HTDBOOBN. 

Pnpantion. — Ligfatnen. — BaUoQn&-.With Oxygen formi Water.— 
Aiiparatus for the Formation of Water. — Peroxide of Hydn^en. 138 

SECT. IIL 

AZOTE, OR NFTROGEN. 

Preparation. — Question as to tlie Constitution of the Atmosphere, and of 
mixed Gases. — Protoxide and Deutoxide of Azote. — Nitrous, Hypo- 
nitrous, and Nitric Acids. . - . - .144 

SECT. IV. 

CARBON. 

Freporatioa — Properties. — Carbonic Acid : Carbonic Oxide : Marsh 
Gas or Fire-damp. — Olefiant Gas. — Oil Gas. — Coal Gas. — Resin Gas. — 
Superolefiant Gas. — Other Hydrocarburets. — Nomenclature. — > Cyano- 
gen. — Hydrocyanic Acid. — Cyanic Acid. — Fuiminic Acid. — Cyanuric 
Acid. — Ferrocyanic Acid. . . . - 157 

SECT. V. 

CHLORINE. 

Protoxide and' Peroxida— Chloric and Perchloric Adds. — Muriatic or 
Hydrochloric Acid. — Chloride of Azote. — Perchloride of Carbon.— 
Chlorocarbonic Acid. . . . . - 180 

SECT. VI. 

IODINE. 

Oxide of Iodine, or lodous Acid. — Iodic Acid.— Hydriodic Add. — Iodide 
of Azot& - - - - - - 187 

SECT. VIL 





X 




OORTBNW. 
SECT- VIIL 


« 


Sulphur 


^ Add.-Smph 


ric a'Z- North. 


«n ur S..Dn 










Sulphu 


retled Hjdcogen.- 




suiphu 






oitcn, and Hyd 








f Cjanogm an 


=j«ic 




r Sulphur. 




Olldc- 


SclcmotiiandSoI 


nlc Acidi..-:scl«ji 


mirfHydroa. 


Pl,p,pho 




o,lcAcld>,-Pl>«p 


oru..-Hn"ph 




- PhoiiihurEltcd 




■d Hydrc^n.- 




afSulpbLc, 






yLVOtlSE. 




1 Hjdroflu 




»c,..„. 


'^ 


Silica. — 


FlUMlllClC Acid. 


SECT. XIIl 


1 


fll Nam™, 


-BoKdcAcid.- 


Fluohorlc Add. 
SECT. XIV. 


1 


I flow.- 


MlvH. - ItM. - Copper. _ Lad. - T 


n — Ziac-^a 


t PUtiatj 


m.-PottHlum.— 






1 *Jr' 




— Emtiuni. — Stiont 


um.— YHHnm. 








nium—MolTbc 


1 IWt 




rT.nt»1um._Tcilu 




§ d>um.- 


-CobalL-Manp. 






■ Pallid 


Id. — nhodlum. - 


Iridium. — Oimlu 




L~ 




Heumc Aculi. 


^ 



CN>NTaMTf> XL 

CHAP. 11. 

COMPOniTDS OF SOMK KUOCBim rEX&S»TSD Bt TBI 
tBOXVAKS KIKODOK. 

SECT. I. 

ACam OF TIORABLBI. 

Cttik^SoiUG^Tatiiric, Qxalk. Game, Bensoicb Monntylic, Ulmic» Kinip, 
Sihic, Pinter Mwonk, Ftetic, Knuneric, Afpartic, Crotonk, Pyrodtric, 
PyioMible, Pyfddnic, Pyxottttttrk^ Pynnnucic, Succinic, Ridnic, 
Elaiodie, CtooanicCkdophonic^ Ctttaaotle, Bidk^ Aloetlc, Muck, Cam.- 
phoik, aad Suberic Acidt . - ... • - piigeS73 

SECT. It 

Quiniiia.— Onchoiiia. — Itoiphia. — Strydmia. — Brada. — Digitalia. — 
Hyoieyaiqa. — Atn>pia«— Vcfatrfa.— ftnatina, &C. - - 882 

SECT. IIL 

OTHBS PftOXlXAtS fKtHCtPUt» OF TRGBTABLBa. 

Ijgnin: WoocUgum: Wood.sugar: Vegeto-sulphuric Acid. — Resins. — 
Enential OiU. — Fixed Oils. •» Wax. — ' Camphor. « Balsams. — Gum. .- 
6umResins. — Caootchou&— Gluten: GliaiUn: Zimomin.— Vegetable 
Albumen.— Starch, or Fecula.^ Sugar.— Tannin: Artiadal Tannin. 285 

CHAP. III. 

COMPOUNDS OF 80ME ELEMENTS AS FRESINTED BT THE 

ANIMAL KiNOfiOM. 

Bone.~CartUage.— Gelatine.— Muscles. — Fibrin: Leucine: Nitrdeucic 
Add : Osmaxome : Adipocere. — Tendons. -^ Ligaments. — Membranes. 
— Cutis Vera. — Animal Albumen : Nails : Horns : Hooft. — Braia — 
Blood: Serum: Crassamentum : BufPyCoat: Colouring Matter.— Fats: 
Stearine: Elaine: Butyrine: Cetine: Phocenine: Hircine: Mar. 
gaiic, Oldc, Stearic, Butyric, Caproic, Capric, Phocenic, and Hirdc 
AddL— Sebadc Add. - - - • - 287 

CHAP. IV. 
eoKrovNDs of acidb with metallic oxidesi and non-ketaluc 

ALKALIES.— SALTS. • - 310 



^^^B 


PART III. 




i 


Kii 




-A PREGGNTED DVRINO EDUE 


BBMABKABIE 




^CHEMICAL CBAKQES. 




^ 




CHAP. I. 




■ 


SECT. 1. 


™»L L.F* 


H 


llieorTofljraliiHjof Cramfimii of laBrnngemd 


""™ " P^ 


'£ 




SECl'. IL 








UNIBKUieB OF THE TBMPBlUinUt BT 11 


JHALS. 




IhtoriBofC 




" 




CHAP. II. 






OF THE S 


.0><TA>.B<.U5 DECOMrosmos OF V 


r.PrABI,E AM 


' 


Vinmu Fecni 
Aoetaui F 


enuaon. - MalBna— Yat. - Alcohol , 
miEnmi™.-VIneg«: Acetic Acid, 
FfnoEntiaon: SlpgularCiieot-Eth 


LB CoBiposilion.— 
. 333 




CHAP. HI. 








or coHBuanos. 






Thoon-^fL, 


oiaicr r of Davy.— Some new Facu relib 
CHAP. IV. 


vc to Flame. 


3» 


Oir TBI DLI 


11UII ^ARTICLES or MAnEB. — 


TBUn aKLA 


KE 


WUaUTG- 


-TH« RATIOS IN WHICH THET COM 


BINE. — NAT 


UBB 


OTATOID 






361 

i 



ELEMENTS 



OF 



CHEMISTRY, 



PART I. 



CHAPTER I. 



INTRODUCTION. 



-Lhe several divisions of science which treat of natural 
phenomena are so intimately connected^ and have so 
many points of contact^ that it is scarcely possible to 
explain the principles of any one^ without assuming 
more or less of the results obtained in others. Che- 
mistry stands peculiarly in this predicament. The 
properties of matter of which it more exclusively treats 
are closely connected with the mechanical theory of 
solids and fluids ; and they are no less intimately re- 
lated to those departments of physics in which the phe. 
oomena of heat^ lights and electricity are developed 
and explained. In complete and independent treatises 
on Chemistry, it has therefore been usual to explain, in 
distinct chapters, so much of those parts of natural 
philosophy as is considered most necessary and useful 
to the researches of the chemical student. The present 
volume forming part of a series comprising distinct 
treatises upon those subjects, the introduction of any 
detailed discussion upon them is less necessary. lt\\a& 
been bought suMcient, in genersly to refer the xeadei 
^ the volumes of this Cyclopaedia which are specisLtty 

jB 



I 



BLBHKHTB Of OanUtlBT. 

I demoted to these parts of science. Some brief eiplan — 
«tion of the mechanical phenomena which will h^ 
principally alluded to, and which are most closely con — 
nected with cheroiBtry, ie. However, indispenBable; aitd^ 
in particulatj a somewhat extended view of the phe- 
nomena depending upon heat has been considered ad—' 
viaable. 

Matter, and all physical agents, are known to ua onl^ 
by their senaible effects ; and when the notion of quan- 
tity ia connected with them, that quantity must always 
be measured or estimated by some effect capable of 
being accurately appreciated by experiment or obseir— 
alion. The phyeical effects most intimately and imi— 
Tersally connected with matter are inerlia and veight- 
Inertia is the indisposition or inability of matter to put 
itself in motion, or in any way to modify or change any 
motion which it may have acquired from an external. 
cause. In fact, it is that quality in which mere matter* 
is distinguished from life. It is the absence of all. 
ability for spontaneous change with respect to rest or 
motion. All experimetit and observation prove that un- 
organised matter pDasesses this quality; and, therefore, 
that it will remain for ever at rest, unless it be put in. 
motion by the application of some external cause ; and, 
if once put in motion, will for ever continue to move, 
unless some external agency interferes to restore it to & 
stace of rest. 

It is proved by observation, also, that to put matter 
in motion requires the exertion of a certain force; and 
that to give the same motion to different masses of 
matter requires the exertion of different degrees of force. 
The quantity of inerlia of a body is estimated by the 
tjuantifji of force necessary to put it in motion at a given 
rate ; and one body is said to have as much inertia as 
another, if the same impulse is capable of commu- 
nicating to it the same velocity. One body is said to 
have twice or thrice the inertia of another, if it requires 
tn-ice or thrice the force to cause it to move with the 
tgaie speed. 






CmATp !• INTBODUOTION. 5 

The qtumiUy qf matter is a phrase of frequent oc«> 
cnrrenoe in all parts of physics ; and it is highly ne« 
oesary that the student should have a distinct and well, 
defined notion of its meaning ; the more especially as 
some confusion is frequently created hy definitions of 
this phrase^ founded on theory rather ihan on ohserv- 
atioQ. 

The qtiantity of matter of a hody is^ then^ determined 
by its quantity of inertia ; and two hodies are said to 
have equal quantities of matter^ when they have equal 
inertia. If the quantity of matter in one hody is said to 
be twice the quantity of matter in another, the meaning 
\ that one has twice the inertia of the other ; or, that 
to give it the same motion will require twice the de. 
glee of impelling force.* The mass of matter, or the 
fXMi of a body, is also a term of frequent use. This 
word mass is to he understood as synonymous with quan. 
%: the mass of a body is, therefore, the quantity of 
^ter in the body. 

If two masses of matter be placed at any distance 
from each other, and be uninfluenced by any external 
force, they will be observed to move towards each other, 
^ if each possessed a certain virtue by which it is ca- 
pable of drawing the other towards it. It is also found 
that, under the same circumstances, this effect increases 
tt the masses or quantities of matter in the bodies in. 
crease. If the quantity of matter be double, the bodies 
will move towards each other with a double speed : if 
the quantity of matter be increased in a threefold pro- 
portion, the speed of their mutual approach will be also 
increased in a threefold proportion; and so on. It is 
likewise found, that the energy of this effect is increased 
in a certain proportion as the distance between the bodies 
is diminished; the more closely the bodies approach, the 
more rapid will be their motions : but this increase of 
rapidity is not in the proportion of the decrease of the 
distance, but in the proportion of the decrease of what 
arithmeticianjs call the square of the distance. 1\i\s. 

*4fMCHANJcs, Cab. CycL Chap. III. 
B 2 



I 



attraction of bodies for one another is called aaAviTA- 
TioNj or oBAviTv. It IB a universal properly of matter ; 
and is found to depend (other resulta being the same) 
on the quantity of mutter aloncj nithout any regard to 
the nature of the body. Thus, a mass of lead and a 
RUBS of iron, having equal quantities of matter, — that is, 
having equal inertia, — will exhibit this attraction in an 
equal degree. Tlie results of astronomical observation 
ijirove that this quality belongs to aU the great bodies 
and bU the facta upon which mechan- 
is founded, prove that it is a quality found in 
bodies campoeing the earth, and existing on its sur- 
The great mass of the earth itself has this quality 
}d relation to all bodies in its neighbourhooil. The inooD 
and earth have a tendency to approach each otherj and 
if the effects were not modified by other causes, they 
would actually approach and coalesce. Detached bodies 
aa and near the surface of the earth are attracted by 
the earth. A body placed at any distance from the sur- 
-$|ce, and disengaged, wiC move straight towards liic 
.surface, and fall upon it. A body placed on the sur^ice, 
^Irill be pressed to the surface with a certain force. 
manifestations of the same principle ; and the 
quality thus exhibited in bodies on and near the earth 
ia called weiuht : weight is, therefore, a particular 
manifestation of the general principle of gravitation. 
From what has been just explained, it will be perceived 
that the weights of bodies are always in the same pro- 
portion as their quantities of matter. 

The proofs that gravity is an universal property of 
matter are too numerous and complicated to admit of 
any development here. In fact, the whole science of 
ASTBONOMV niay be regarded as one connected demon. 
Btration of the universality of this principle, so far as 
regards the great bodies of the universe; and the whole 
science of what is called ti^rrebtrial hiichanicb, a 
like demonslration of its universality, so far as regards 
ourearthj and the bodies upon it.* 



Wec, 



VI. indVH. 



CHAP. U. ATTKAOnOir OF ORAYlTATIOir. 



CHAP. II. 

ATTRACTION OF GRAVITATION. 

If a body be supposed to consist of particles of matter 
of equal weight, it follows that the greater the number 
of particles included within a certain volume or bulk, 
the greater will be the weight of the mass. If there be 
ten separate particles of matter, each gravitating with a 
force equal to 1, the gravitation of the whole ten par- 
tides, if united into one, would be equal to 10, and this 
would happen without reference to the bulk : the force 
of gravitation is, therefore, in proportion to the quantity 
of matter. 

The quantity of matter constituting the bulk of any 
body is subject to much variation. If we assume any 
measure of bulk, and fill it up with leaden bullets, we 
have a certain volume or bulk of lead ; if small shot be 
shaken in amongst the bullets, the quantity of lead is 
much increased, although the bulk remains the same : 
and even after this, a considerable quantity of smaller 
shot may be introduced without adding to the volume. 
Here then are three bulks, apparently the same, yet all 
differing in the quantity of matter which they contain, 
and, consequently, in their force of gravitation. A quart 
of ardent spirit mixed with a quart of water will make 
less than two quarts ; as if the same penetration takes 
place between the particles of the two liquids that hap*< 
pens with large and small balls of lead. A mixture 
of a quart of oil of vitriol with a quart of water will 
bear the addition of a very large quantity of the solid 
substance called magnesia, before the totsd bulk of two 
quarts will be made up amongst them all, when cold. 

The quantity of matter contained in any bulk i^ »:&- 
eertained by the process of weighing. A cubic \uc\v oi 
pure solid copper will weigh 4-j7j. troy ouiicea ; 1l\A*, 

B 3 




accordingly, expresEea its quantity. It ia quite evident 
that another cubic inch of copper put into the opposite 
side of the balance will counterpoise the firal ; but it by 
no mcan« follows that a cubic inch of any other rnetd 
will do the same. So much the contrary is the fact, that 
a cubic inch of Etandard gold ■ will exactly balance two 
cubic inches of copper; hence there is in the formec, 
twice the quantity of ninttcr Chat there JB in the latter, 
the bulku being tlie Bame. 

It appears, therefore, that equal bulks of different 
kinds of matter may have very different weights; and, in 
fact, every Jistinct species of body has a weight in a 
given bulk peculiar to itself. This property ia bence 
called the specific gravity, or density of bodies ; and 
It ia of great value in distinguishing one kind of 
matter from another^ it being different in almost every 
kind. To ascertain the specific gravity of bodies, there- 
fore, the bulk and weight are to be taken inl« account. 
If a cubic inch of copper weighs 4'7 troy ounces, no 
more is learned from this than its absolute weight ; but 
W a cubic inch of standard gold weighs 9''t troy ounces, 
not only is its absolute weight known, but it becomes 
manifest that tills metal is twice as heavy as copper ; or, 
in other words, contains twice as much matter, bulk for 
bulk. In the same manner might be tried the weights 
of cubes of all other metals and sohds, and it would thus 
be found how much heavier or lighter they are than the 
cube of copper: this would give their specific gravity, 
or their relative weight coropared to copper; but thoe 
Would be many sources of difficulty and error in such a 
method. First, it would be almost impossible to pro- 
cure true cubes or other figures ; they would not be all 
of precisely the same size, and the specific weightswould 
be all referable to copper. On these accounla another 
method is adopted. As different specimens of copper 
may be more or less heavy, according as they are more 
or Jess pare or hard, it is necessary to seek a substance 




^nu>. H. ATTAAcnON 09 OAAVITATION. 7 

Dot liaUe to Tariation : such is water ; any determinate 
\nJk of which^ when pure and at the same temperature, 
Is always the same in point of weight, aJtd hence it is 
preferred as a standard of comparison. Thus, instead 
€rf saying that the specific gravity of standard gold is 
twice that of copper, we ascertain how many times the 
gold cube is heavier than the same measure of water. 
This is easily done; for if a solid be immersed in a 
vessel of water, the water will rise in the vessel, and 
fill an additional space equal to the l^ulk of the solid. 
The water that is ^us displaced, having weight, has a 
tendency to fall back, and in its turn to displace the 
solid immersed; the water, therefore, presses on the 
solid, and tends to push it upwards, although it may not 
succeed so as to occupy its place. Now, it is proved in 
hydrostatics*, that the force with which the solid is 
pressed upwards must be precisely the weight of the 
quantity of water displaced by the solid ; that is, its own 
bulk of water. Hence we derive this conclusion, — that 
when a solid is immersed in a fluid, the solid is pressed 
upwards by the weight of as much of the fluid as is 
equal to the bulk of the solid ; the solid thus pressed 
upwards must, therefore, be so far buoyed up by the 
fluid, or, in other words, must lose that much of its 
weight by the immersion. That the apparent weight is 
diminished by immersion in water, is easily proved. 
Thus, let a person raise the heaviest stone that his strength 
permits him from the bottom of a river; while the stone 
is still under water he can lift it, but let him attempt to 
raise it entirely out of the water, and all his efforts will 
prove ineffectual. In the same manner, an angler, with 
a single hair and slender rod, draws a fish with ease 
through the water ; but he may snap the hair or rod in 
two, if he should attempt to raise the fish altogether out 
of die water. 

It is easy to prove, by experiment, that when a solid 
is immersed in water, it, for the time, apparently lo^^ 

»J!brs detailed account of this and other mattew alluded Ui \tv X\vA 
chapter, seethe Treatlte on HrDRoaTATtCB, Cab. Cyd. 

B 4 



p 



U much of its weight aa the bulk of water displaced bj 
it weighs ; and that, consequently, it actjiiires buoyancy, 
or »n upward preBsure, equal to the weight of die dis- 
placed waWr. Let a vesBel, Buppoac of glass. A, flir- 




I 



I 

^^r nislied with a lateral pipe fi, be filled with disdlled 

^H water, until some has run out at B, and it has ceased to 

^^m drop. Then place under it the empty receiver C, and 

^^B Hispend in the water a hollow glass ball, fastened by a 

^^1 thread E, to one of the pans of a pair of scales, and pr&- 

^H viouHly counterpoised in the air. On immerBion, the 

^H balance will immediate!)' be subverted ; the glass ball, 

^^1 according to the portion immersed, will displace water, 

^H and that water will run into tlie receiver C. When the 

^U water has totally ceased to drop from the pipe B, pour 

^1 the whole quantity contained in C into the pan of the 

Bcsde from which the glass hall is suspended, and it will 

be found to restore the balance. This proves, that the 

weight of water displaced by the glass ball was precisely 

the weight which the glass ball lost by immersion ; or, 

in other words, acquired in buoyancy : and it is obvious 

that the bulk of the water displaced could not be other- 

1 equal to the bulk of the glass ball. If the 

:r displaced by the ball, and tlte ball itself, be equal 

weight, then the ball and the water are of the same 

ec/jJc gra%-ity, and the ball will float in ati^ 'gart oS 




C«AP*4I. ATTBAOnON OF ORATITATJON. 9 

the water without any tendency to rise or falL If tht 
weight of the water displaced he greater than that of 
the ball^ the latter will be pressed up to the surface, 
where it will float, and a part will remain above the 
surface. If the weight of the water displaced be less 
than that of the ball, the latter will fall, by its difference 
of weight, to the bottom, and remain there.* 

The law being now understood, that when a solid is 
immersed in a fluid, the solid loses as much of its weight 
as its own bulk of the fluid weighs, we are presented 
with a method of ascertaining with precision the weight 
of the quantity of water that is equid to the bulk of any 
toiid. We have no more to do than to weigh the solid in 
a delicate balance or scales ; then to tie it with a horse« 
hair to a hook in one of the pans, and let it hang in pure 
water so as to be immersed : it will be found to be 
buoyed up more or less : then to add weights to the 
lighter dish of the balance until the equilibrium is re- 
stored ; the weights so added will be the weight of the 
water which equals the solid in bulk, and was displaced 
by it. Suppose that when the solid was weighed in the 
air, its weight was 6 ounces, and that when weighed 
in water it lost so much that 1 ounce was required 
on that side of the scale to restore the balance ; then 1 
ounce was the weight of the solid's bulk of water, and 
die solid weighed six times the weight of its own bulk 
of water. Hence we say that the specific gravity of that 
solid is 6 : and we mean that it is six times heavier than 
an equal bulk of water. In all such cases the weight of 
the cUsplaced water is called unity, or 1 : but as fractions 
often occur, one is considered 1000, and then the above 
specific gravity must be written 6*000. 

The very same consequences result, and the same 
explanations apply, be the medium, in which the bodies 
are immersed, what it may ; whether it be water or any 
other liquor, or air or any other gas. 

In the common process of weighing, the bodies axe 
immersed Jn a medium^ different^ it is true, from walet. 
• HrDB08TATic9, Cab. Cycl Chap^ V. and VIU 



10 Klbments of chemisthy. part 



but still sufficient Blightly to influence the results. 
When an ounce of glass anil an ounce of lead hang from 
a scale-beam in the air, they counterpoise each other, 
although they are, in point of fact, somewliat different 
in weight : for, being unequal in bolk, they displace 
unequal bulks, and therefore weights, of air ; ar.d these 
unequal weights of air press upwards differently on the 
glara and lead, and the difference must be compensated 
by a eorreepon ding, although trivial, difference of weigh) 
between the glass and the lead, if they are to remain in 
& state of equipoise. 

That the air does exert this unequal pressure on the 
two bodies of different bulks, can readily be proyed bj 
rowing the experiment on two bodies in which, ih* 
difference of bulk is considerable, weighing them first it 
dr so as to balance, and removing the air by Ihe air- 
pump, when the balance will be immediately subverted 

It therefore appears, that, in order rigidly to asceriaii 
tiie relative weights of any two bodies, when the specifll 
gravities are very different, they must be weighed in I 
yacuum, as it is only in this way that the influence ol 
bulk is obviated. But if the specific gravities be dM 
same, they may be weighed indifferently in a vacunin 
OT in air, or in any liquid. However, the inaccuracy It 
weighing any body in the air, unless it he exceedind] 
voluminous compared with the body against whidtiti 
weighed, is so trivial, that it may be disregarded i'^kBi 
when any substance is said to weigh an ounce,'il ii 
nnderslood to do so in air. 

There are circumstances to be attended to, with regan 
to temperature, which will be explained more fully here, 
after. For the present it is enough to say, that, in al 
eomparisons of specific gravities, the temperature of thi 
Bolids or liquids under examination must be the same 
for difference of temperature creates difference of bulk 
cold contracts, and heat expands, all bodies. When a 
temperature is expressed in stating the specific gravit; 
of mny body, that of 6o degrees ol Fa\\ieiilwil'« tbec 
tooateter is to be understood. -^^m 



I 

^saJiihta* AimAcmoN of oohbsion. 11 



CHAP. III. 

ATTBAOTION OF COHESION. 

Havino adverted in a general way to the attractive 
power which the bodies of the universe exert upon each 
other ; and having stated that this agency is exerted by 
the globe of the earth as well as by the smallest masses 
oomposing it> and that it gives origin to great varieties in 
the constitution of matter, it remains to enquire how far 
the minute particles of which these masses consist are 
afiected by any attractive influence. 

If we examine the materials of the globe, we perceive 
that some are hard and dense ; that others are soft and 
porous, that water is destitute of solidity ; and that th6 
atmosphere is far more attenuated. If a certain force be 
applied to a piece of glass, it is resisted ; but if the force 
be increased, the glass is broken, and by repetition of the 
process may be reduced to powder. The glass is now 
separated into the parts which previously offered resist- 
ance to the change, and which, consequently, were held 
together by some force. This force, therefore, is the 
cause of the solidity of the glass : it was obviously an 
attraction of the parts to each other that caused them to 
cohere ; and hence it is called the attraction of cohesion. 
It is also called the attraction of aggregation^ because it 
aggr^ates or assembles and retains the particles of bodies 
in the state of a solid. 

The evidence of the existence of cohesion is not merely 
inferential from the constitution of solids^ but can be 
proved to act between separate atoms and masses of 
matter. A mass of gold can be beaten out into a thin 
film, which could not happen if its constituent particles 
did not glide over each other and join new ones during 
the hammenng; yet still they are found to cohere. Tvio 
/ffsti'na masses of matter may be made to cohere by coiv* 



IS 

Uct. ThuBj let Ino pieces of lead be formed in n 
way that two of their flurfaces may be readily cu 
with a Bharp knife, and that -when the cut surfact 
applied to each other as at A, they will both ha 
the same perpendicular direction. 
a scale-pan be attached to one, ai 
the other be suspended &om a star 
If the two surfaces of lead be fo 
U A preseed together with rather a a 
motion one over the other, and the 
pound piece then hung up, they w 
here with so much force that weig 
, the amount of several pounds m 
i gradually put into the scale-pan 1 
ihey separate. 

I made the experiment with pit 
^j L^ lead one eighth of an inch thick 

^EJ^y surfaces in contact were each five i 

of an inch long; perhaps the real physical contac 
not more than one third of this, yet they euai 
a weight of three pounds. It might be, and indee 
once, supposed that the air having been excluded I 
dose contact of the contiguous surfaces of lead, 
WM a certain degree of atmospheric pressure tendi 
keep them together; but this was disproved by Mo 
who showed that the surfaces cohered just as fa 
when the whole apparatus was put under the recei 
an air-pump, and the air withdrawn. 

With regard to this kind of attraction, called coh 
we have to consider it under two conditions — 1 st, 
ila operation is suspended, and, 9d, when it is res 
Common experience is sufficient to prove thi 
force of cohesion is very different in different b 
some will scarcely permit the separation of their 
by almost any ordinary force ; while others, with 
culty, retain the solid form. When a solid is 1 
down by mechanical means, its cohesive force hai 
overcome; the operation of this force is sttspendet 
f^e body is now said to be mecbanicaW^ itaiicA. 



CHAP. ni. ATTBAOTIOM OF 00BE8I0N. 13 

ever fine this powder may be^ a microscope will prove 
that it is composed of grains^ every one of which is a 
soHd of the same nature as the original ; and there is a 
limit which, in the process of pulverisation, cannot he 



Although these particles are the smallest that can he 
procured by mechanical division, they are by no means 
the smallest that can be obtained by other means. Let, 
for instance, a piece of sugar be reduced to the finest 
powder ; its parts are still discoverable to the eye ; but 
let water be thrown on it, and it presently disappears 
altogether ; not a particle can be perceived by the most 
powerful magnifiers : it is now reduced to its smallest 
parts ; yet they are not destroyed, for they may be re- 
covered, 

In declaring that these are the smallest parts, a ques. 
tbn is taken for granted, on which philosophers are 
hj no means agreed, namely, whether there is any limit 
to the smallness of the particles to which solids can be 
leduced ; or, in other words, whether or not matter is 
infinitely divisible.* It will be shown hereafter, that, 
unless we admit the finite divisibility of matter, and the 
existence of atoms or molecules, the most important 
series of phenomena in the science of chemistry will be 
left in the situation of ultimate facts which, on the other 
hand, are beautifully and completely accounted for by 
the atomic hypothesis. The happy explanation which 
this series of phenomena receives from the admission 
of limited divisibility, is a strong argument in favour of 
the truth of that doctrine. 

Whatever may be the truth on this subject, it is certain 
that the practical divisibility of matter is truly astonishing. 
Silk, as spun by the silk- worm, is so fine, that twelve 
grains' weight measure one mile.f Gold can be beaten 
out into continuous leaves so thin, that, according to 
Boyle, 50 square inches wiU weigh but 1^ grain ; ac- 

* See MscHAJfica, Cab, Cycl Chap. II. 
/ SAaw'g Boyle, L40i. 



cording to others, 56 square incheH will wdgli but 
graiu. The gilding on silver wire is much thinuej 
Dr. Halley ehowed thai it may be hut tjiVuti^'* P* 
of an incb. Boyle proves that an ounce of gold can 
tliUN extended on silver to the length of 1^5 milei 
others say 1300 mileii ; and others, again, have d 
culateil that 14,000,000 of films, such aa erasts on tl 
wire, would be required to make up the thickness of t 
inch, although an equal number of leaves of cominf 
printing paper would be nearly three quarters of a mj 
in thickness. Dr. 'VVollaslau made a gold wire so th: 
that an ounce of it would extend 50 miles. The hui 
dred thouiandlh part of a grain of gold is visible to tl 
naked eye. If five avoirdupois pounds of pure waV 
be poured into a glass globe which it fills, and one graj 
weight of aloetic acid (a substance obtained by the acdc 
of nitric acid on aloes) be added, the whole will, afti 
some time, assume a line crimson colour; which could ni 
happen unless the grain of aloelic acid had been divide 
and equally difilised throughout the whole volume i 
water. It is possible to see so small a quantity of watt 
as a thousandth of a grain, and this portion of the solu 
tion must contain a thirty.five millionth part of a grai 
of aioetic acid. We have, therefore, actually divided 
dngle grain of this substance into 35,000,000 of parll 
and we know that the division can be carried muc 
farther. The substance called cervlin, obtained froB 
indigo, dissolved in the same proportion in water, give 
it a blue tinge throughout. 

Not only are the constituent particles of differen 
lands of matter heJd together by a different degree o 
cohesive force, hut we can lessen or increase this fore 
by artificial means. It is not possible, however, to de 
■troy it ; 30 far as human means are concerned, it seem 
SB indestructible as matter itself: all that we can do i 
to suspend its operation; and then it is always read; 
its energy when circumstances permit. Al 
tenestiitil bodies nre found in one or other uf the threi 




aUy,XIL ATTRACTION OF OOHESIOK, 15 

Mowing states, — the solid, the liquid*, or the state of 
air or vapour. Between solidity and liquidity there are 
degrees : a hody may he more or less solid ; it may he so 
soft as to he almost a liquid : hut airs or vapours always 
maintain the most perfect fluidity ; they never approach 
the other two states, and they remain like the atmo* 
sphere around us. There are many hodies which may 
be made to exist in any of these three states ; and, in 
tiK spirit of generalisation, it has heen even Bupposed 
that this is true with regard to all matter, although facts 
are not yet ahundant enough to warrant us in consider- 
ing such an assumption as estahlished. Ice is solidified 
water; when heated it melts into the state of a liquid; 
and this liquid, hy heing further heated, evaporates into 
the state of air or vapour called steam. This part of 
the sahject will be resumed in its proper place : it has 
been introduced here merely for the purpose of observing, 
that although, when a solid becomes liquid, its cohesion 
is said to be suspended, yet it is only its cohesion as a 
solid that is suspended, and we are by no means to sup- 
pose that the fluid produced is destitute of all cohesive 
force. On the contrary, the cohesion of liquids is an 
appreciable force, and exerts an agency easily rendered 
manifest. Thus, if a particle of quicksilver, which is a 
metal in a liquid state, be brought as near another par- 
ticle as is possible without their touching, they both pre- 
serve the globular form, which they naturally assume in 
consequence of the mutual attraction of their parts, act- 
ing in the same way as gravity does, in producing the 
sphericity of the celestial bodies. If they be brought 
so near as barely to touch, they instantly coalesce, their 
separate outlines are lost, and they form one larger 
globule ; or, in other words, the attraction of cohesion 
draws the particles of both globules, hitherto separate, 
into close contact, and holds them united. But so 

• The word Jiuid is used by chemists in rather a loose sense : it is merely 
opposed to a solid, and means either a liquid or a gas. In physics, the word 
i> a ^enus of which the species are gas and liquid, otherwise expre&sed Vsy 
^\Mtic and inelastic duids J and, in strictness. Jt is improper to confound on« 
fJlA the other. 



smftll is the tliaUnce to nhich they must be approached 
hefore the}' unite, that tlic finest dust un their Burfac^ 
prevents the union. Anotlier case of the coheBion o^ 

lids JB witnessed when we immerse a glass rod inm 
vster, and draw it out, holding it perpendicularly; th^ 

er forms a pendulous drop, and remains suspended — 
Here the attraction between the glass and the wate^ 
nstaina that portion of the drop nest the glass; bn^ 
tile lower portions of the drop are prevented from fall — 
ing off by their own cohesion. It is the same cohesiT^ 
power that preserves Btnall portions of quicksilver ii^ 
the globular form ; or drops of water on dusty sur — 
faces ; or drops of oil on wet surfaces ; otherwiie, thej^ 
would all lie flat, like filmi!, according to the laws of 
gravity. The cohesion of a liquid can be strikingljr' 



d 



^ e^ 



shown by an easily executed experiment. Let one of 
the scale-pans of a balance be removed, and a disc of 
tin-plate be hung by a thread in its place. Let the disc 
of tin hang horizontally in a shallow vessel, but not 
touching the bottom, and let the balance be brought to 
an equipoise. If water be poured into the vessel as high 
BK the tin disc stands in it the two surfaces will adhere, 
ajic/ with such force that weights pio^rtiouBte to the 
surface engaged may be put into die oppowte »6e ^i^ 



CBAP. m. ATTRACTION OF COHESION. 17 

Out forcing them asunder. When the weight in the 
opposite side is sufficient^ it will even be seen^ if the 
Vessel he of glass^ that the water is raised under the 
^isc^ above the level of the surrounding water^ so great 
is the force that opposes the separation of the stratum of 
'V^ater which adheres to the disc. This experiment fur- 
nishes an instance of the cohesion of a solid to a liquid, 
and of the particles of a liquid to each other. By the 
same apparatus we can prove that different liquids have 
different degrees of cohesion : for while the weights are 
in the scale-pan^ and the water is thus raised above the 
level, if a little ether be poured into the vessel, it floats 
on the water, takes its place, and instantly the tin disc is 
detached. 

Airs and vapOurs exhibit no cohesion : they are in. 
fluenced by an opposite force, which will be treated of 
hereafter. It now remains to consider the restoration 
of cohesion to bodies in which this force had been sus- 
pended. 

The simplest case of this kind is the following. If a 
piece of lead, or any other metal, be melted in the fire, 
its cohesion is suspended ; it becomes a liquid : but if 
it be allowed to cool, its cohesion again begins to act, 
the particles attract each other strongly, and it soon 
becomes as solid as ever. Here is a plain case of the 
suspension and restoration of the cohesive attraction, 
from a cause that will be enlarged on hereafter. 

The same may be effected through the intervention of 
a liquid. If a large quantity of sugar be dissolved in a 
smidl quantity of boiling water, and the syrup allowed 
to grow cold, the attraction of cohesion will begin to 
take effect between its particles, and at length the sugar 
will once more become a solid. But, in this case, as in 
many others, it is worthy of attention, that, whatever 
be the original state of the sugar, it always, in re- 
suming its solidity, assumes a particular form — one of 
great regularity and beauty. It was originally opaque \ 
it is now transparent: it wrs originally a shape\e^% 
izw»y jtjs now a prism of sixs ides, in regularity aiv^ 

o 



lustre scarcely to be surpassed by (he products of tb* 
lapiJary's wlieel. A solid of this syimneuical foriUj ain^ 
of spontaneous production, is called a crystal; and the 
process by which it is produced is called cryataUiMtion- 
There are nurabetlesa other Bubstancea which are 
capable of assuming the crystalline structure, of oU 
shape or other : common sea-salt, alum, and saltpetre, 
•re instances familiar to every one. Many bodies are 
found naturally in the cryetaliine state, as various precious 
■tones and minerals. 

With regard to artificial crystals, there are two model 
of producing them : either by dissolving the substanw 
of which they are to be composed in as little boiling 
water as will sufice, and allowing the noluHon (as the 
'dissolved substance is called) to cool ; or by melting the 
body by fire, without water, and allowing it to cool 
quietly and slowly. Jn the instance of certain sub- 
•tances, when a part has solidified, the liquid pari is to 
be poured off, and the residue will have the crystalline 
form. It does not, however, follow thai, in crys- 
telUsation, the same body invariably assumes the saine 
form : the fact is otherwise ; there may be several forms 
of crystals belonging to one body, but in one or other 
of these it is sure to crystallise, end not according to sny 
ether model. It is also true that very different kinds of 
matter may crystallise after the same model. 

Bodies, whether solid, liquid, or vaporous, are capable 
ef asauming the form of a crystal. If sulphur be melted 
faito a hquid, it will, on cooling, crystallise : if water be 
cooled to a low degree, it will shoot into crystals, and 
form ice ; and various vapours, such as that into whidi 
camphor is converted by heat, will, when cold, change 
into crystals. There are several metals which, when 
•lowly cooled after being melted, will cryatalli^e. 

The facility with which bodies assume the crystalline 
form is very various ; some doing sa with great ease, 
•nd others with great difBculty. The general method 
of obtaining crystals from BubBtances wWck diaaolve ia 
water ia to add the substance to tbe matet ai i\»Soii^ 



OHAP^tn. ATTItAOnON OF OOHESIOK. 19 

beatj and in as great a quantity as the water is capable 
of holding in solution. As the liquor cools^ the crystals 
tre produced ; and the more slowly it cools^ the more 
tegalaa the crystals. Sometimes it will be necessary to 
reduce the liquor to the freezing point before it will crys- 
tallise ; and sometimes it will show no more tendency 
to do so when cold than when hot ; in which case the 
Water should be gradually boiled away until the crystals 
have formed abundantly : it is in this way that com. 
mon sea-salt is crystallised. Motion promotes crystal- 
lisation ; but rest promotes' regularity of the shape of 
the crystals. 

The tendency to crystallise is often so nicely balanced 
by the force which resists it^ and which will hereafter 
be treated of^ that inconsiderable causes operate for or 
against the change. If a quantity of hot water be made 
to dissolve as much Glauber's salt as it can^ and if the 
solution^ still hot^ be poured into a glass globe which it 
just fills^ and the mouth of the globe tied over firmly 
with moistened double bladder^ it will not crystallise 
even when cold, provided no agitation has been used. 
Merely opening the covering of bladder, or throwing in 
a small crystal of the same salt, or touching the surface 
of the liquid with a metallic point, will instantly cause 
a crystallisation to commence, which will immediately 
extend downwards, in a singular manner, through the 
whole globe, and the contents, instead of being fluid, 
will become solid. So trifling are the causes which 
eflect this so long suspended crystallisation, that the 
nature of the phenomenon has never been understood^ 
notwithstanding that much investigation has been ex- 
pended on it. It is a singular fact, that, in the crys- 
tallisation of this salt, and a few others, light has been 
observed to be emitted when the experiment is conducted 
in a dark room. Melted phosphorus often comports 
itself in the same way with regard to suspended solidifl. 
cation; and there are other similar instances Imowtv. 

From all that has been saidj it appears that matter \% 
Bosceptible o£ being divided into particles so uunute aa 

c 2 



' 20 

to surpass sU com prehension ; ihat this division is in aC 
^obability not withoul a limitj that these minute par- 
I tides are held together in ihe solid state by a powerful 
I force or attraction, called the attraction of cohesion on 
I Bggregntiun ; that this force is manifested more stronglj* 
[ in solids than in liquids, although in the latter it is still 
I ditcoverahle ; and, lastly, that in some conditions ol 
;r, although it exists, ils operation is euspended, bal 



Thh natural forces, gravitation and cohesion, noticed 

n the former chapters, belong, in their full development, 

nore to mechanics than to chemistry. Hence, al< 

hough some preliminary pages have been devoted Co 

I these subjects, we have abstaineil from enlarging on 

n. There are, however, other forces in nature to 

[ be considered, which fall more exclusively within our 

I province ; and which, so far as this planet is concerned, 

a port equal in importance and interest to any 

f a rod of iron be immersed in a vessel of water, on 
I drawing it out it is found that some water has adhered 
■ , ; but if a rod of iron he immersed in a quantity of 
mercury, on being withdrawn no mercury adheres. Both 
of these facts are easily recognised as dependent on the 
eficcts of cohesion. The attraction of cohesion took plaM 
between the particles of the iron and those of the water; 
the same attraction, it is true, subsisted between the 
particles of water which were drawn out of the vessd 
and those that remaned in it, hut the attraction between 
tbe iron ui J trdter predominated. Not ao'w\ie\i'iii^wt 



OEAP. IV. ATTRACTION OP AFFINITY. 21 

^as dipped in mercury ; although there was an effort at 
the exertion of the cohesive attraction, it was not effi- 
cacious, because the cohesive force keeping the particles 
of mercury together was superior. But if a rod of bright 
gold be immersed in mercury and taken out, it will be 
found that the gold has drawn up a coating of mercury 
'which cannot be wiped off*; the gold is rendered white; 
And, if left long enough in the mercury^ it becomes 
soft 

In this case the mercury adhered to the gold rod, 
and was drawn up with it^ in opposition to the laws 
of gravitation, and to the cohesive force existing be- 
tween the mercurial particles. The question occurs, 
Was the mercury drawn up by a cohesion acting between 
il and the gold ? But it is answered in the negative by 
the fact, that the mercury cannot be wiped from the 
gold, nor removed by any degree of mechanical force : 
for if the surface be scraped until the whiteness be re- 
moved, a separation is not effected ; the scrapings con- 
tain both gold and mercury. 

Now, since the influence which caused the mercury to 
be drawn up by the gold was evidently some sort of an 
attractive force, and since it was not the attraction of 
gi^vitation or of cohesion, it must be some other, — some- 
thing unlike either of the forces which we have been 
considering. Accordingly, it is to be acknowledged as 
a different exhibition of the attractive force that pervades 
*11 matter ; it is distinguished by the name of chemical 
oitractiony or simply by the term affinity, — a more con- 
venient but less expressive term ; and it differs from all 
known forces in its agency. 

If a piece of lead be melted, and a bit of block tin be 
^d gently on its surface, it floats there in the same 
manner as a cork would on water ; because tin is spe- 
cifically lighter than lead. In a short time the tin will 
melt with the heat ; and being specifically lighter, we 
should expect it not only still to float, but to coxvaUVAXla 
Ae upper stratum when the two metals have groviTV so\\Ol 
fy cooling. It happens, hovr ever, Qi\iGt\i\&^\ fox vje ftxv^ 

o 8 









iftj' avlirfitt : diM, ipirii of 1 
Wt "■'l if '( I" povcd caDtiMii , 
K J but after • Imglh «f tiitie it irfll be found 
Tut* ffiWMuUfl to the bottom, and to be equally 
AHhi—ii lliftruKb all liBrr*, in cong»juence of the affinity 
*W«/ /// till- WMU-r to it. U, on ihe oihef Viind, ofl 
Hr, it wlU <eniBiu iherc 4\nm%«M 



/ 



<!BAP. IV. ATTRACTION OF AFFINITY. 23 

pcHod ; for it is lighter than water^ and is not attracted 
by any strong affinity to that liquid. 

A familiar instance of the attraction of an air or gas 
^J be found in the air \vhich is expired from the 
^gs^ and which is different from atmospheric air before 
it enters the lungs. If we hreathe for a few minutes 
Qpon a small quantity of slaked lime mixed with a little 
wster^ the lime will attract some of the air breathed on 
it, and will detain it. To prove that it does so^ we have 
only to pour on a little strong vinegar^ which will cause 
an die air that had been attracted to bubble off* visibly. 
But atmospheric air^ were it perfectly pure^ which it 
never is^ might for ever remain in contact with lime 
without being absorbed^ because no effective affinity sub- 
sists between them. 

This attraction does not act at any distance that can 
be perceived; its existence is only discoverable by its 
effects : but its consequences are very striking, and the 
changes it produces are of such a nature as cannot be 
overlooked. In the case of the cohesion of two masses 
of matter — suppose two pieces of lead, glass, or any 
other substance — they merely stick together with more 
or less force; the matter is in no respect altered. A 
piece of tin and a piece of copper may be made so 
smooth as to permit their being brought sufficiently 
near each other to allow the attraction of cohesion to 
operate; they then cohere together with some force, 
yet the two metals remain in every respect unchanged 
in their nature. But if their chemicaJ attraction be 
allowed to operate, as by melting them, the masses 
of each metal do not merely remain in juxtaposition, 
as in the former instance ; a mutual penetration of sub- 
stance seems to take place ; the particles run together 
and mix, so that no part of the resulting mass possesses 
ihe properties of either tin or copper. In this case of 
attraction, the only view which can be taken of the change 
produced is, that the ultimate particles, or most minute 
yortioDs of which the mass of each metal is com'^o^ft^, 

4 



I 



•ttract eacli olher ami unite, particle to particle; this ^^M 

expreEaed in chemical language by saying that the tw " 
melals combine. 

By thus melting the two metals into a combinatioi^^ 
estraoriliiiary changes are prtKiucecl. Thus, copper is o- ■" 

a reddish -brown colour, and tin is trhite ; we bIiouIi 9 

expect [he mixture of both metals to b 
both colours, that is, a paler reddlEli-brown ; 
real colour of the mixture is gray. Asain, copper is i 
Mft metal ; tin is etill softer ; but the mixture is exceed 
ingl; hard. Copper is also a light metal ; tin still mot^^ 
•0 : hut (he mixture is much heavier, bulk for bulk, thai^B- 
eitfaer. Of this, Glauber, one of the earlier chemists^ 
gjves a plain illustration. He says, " Make two balls o^~ 
copper, and two of pure tin, of one and the same form anA 
quantity, the weight of which halls observe exactly ; whidk: 
done, again melt tlie balls into one, and presently pour onC 
the mixture melted into the mould of the first balls, ancL 
there will not come forth four, nor scarcely three balls,' 
the weight of the four balls being reserveii." It appeara, 
then, that the same weight is condensed into a smaller 
bulk. Another, and not the least remarkable change, 
effected by the combining of the two metals, is on their 
sound. If three bells be cast from the same mould ; one 
of copper nearly pure *, one of good tin, and one of a 
mixture of both ; the copper bell will have a dull, heavy 
sound J the tin bell almost no sound ; but the mixture 
of both will have a sweet, clear, and musical sound. 
Hence bell-metal is composed of a mixture of tin and 

What the nature of the change may be that is thai 
produced on the two metals, cannot be explained ; but it 
is certain that, in the mixed mass, the coniiguity of a 
particle of one kind of metal produces a very decided 
change on the properties of the adjoining particle of the 
other ; and a property is produced by their union, which 
neither particle apparently possesseg. 

When J say that a particle of one Vind o( me^ acts 
' /tcauJdootbeculirtbccoppeoieceTeilKUT ^le. 



<3CBAP. nr. ATTBAOnON OF AFFINITY. 25 

on the contiguous particle of another^ it is necessary to 
explain what is meant by contiguity. It is not meant 
that the particles should be merely very near each other; 
they must be in actual contact — at least, in contact so 
fv as is compatible with the constitution of matter^ as 
"^^ be hereafter explained. 

Were this contact not an indispensable condition for 
the production of the change of properties occasioned 
in the tin and copper by their mixture^ it might be 
supposed that the same would occur on mixing ex- 
tremely fine filings of copper and tin ; but this would not 
^ realified in point of fact. By no mechanical means 
in our power is it possible to bring the particles of the 
^0 metals inUf the close degree of contact required for 
^ complete change of properties which the bodies con- 
^^ned arc capable of, and which is effected so easily 
I7 melting them together. By melting, the metals na- 
sally fall down into what are called their ultimate or 
niost minute constituent particles^ and no mechanical 
Cleans are competent to this eff*ect. 

The change of properties which takes place when 
chemical attraction acts^ is not confined to metals^ but is 
* general result in every case where different bodies 
*fe brought into this state of combination or chemical 
^ion. Frequently we find that the properties of each 
body are totally changed ; and that substances, from 
being energetic and violent in their nature, become inert 
and harmless, and vice versd. For instance, that useful 
snd agreeable substance, culinary salt, which is not only 
harmless, but wholesome, and absolutely necessary to the 
Well-being of man, is composed of two formidable ingre- 
dients, either of which taken into the stomach proves 
fatal to life ; one of these is a metal, and the other an 
air; the former is called sodium, the latter chlorine. 
When presented to each other, the violence of their 
nature is manifested by their immediately bursting out 
into flame, and instantly they are both deprived of their 
yirulence. Can any thing be more striking t\\aii Xiie 
change of properties in this case; and who co\x3lOl \ivje 




^I'Atvej 



■opposed that culinary sitlc is composed of a metal owSiA 
to an air ? The medicine called Glauber's salt is in- 
Other instance; it is composed of iwo caustic poiwnBot 
dilTerent kinds ; one called oil of vitriol, and the othel 
barilla or soda. There are also two substanccB knowa 
to chemiste, which are disgustingly bitter liquids ; one i* 
ealled nitrate of fiilvcr, and the other hyposulphite of 
■oda ; when miKed, they form a compound of contid^- 
able Bweetness. But the atmosphere which we bretthe 
ia the moat extraoriUtiary of all instances ; it must be 
■urprising to those who are unacquainted with the !tt^t 
that atmospheric air, indispensable as i\ ia to Ufe, is I 
oompoeed of the same ingredients as that most violeBt ' 
and destructive liquid called aqua /ortis, or nitric aoA- 
This powerful acid, by being made to act upon sugUi 
the sweetest of all things, produces a substance intensdy , 
bitter to the taste. Charcoal ia, of all known aubstancei, 
the most difficult to convert into vapour ; so much W| 
Indeed, that the conversion has never yet been decidedly 
effected ; it is also a very solid substance ; and diamond] 
which is nothing but crystallised charcoal, is one of ibe 
hardest bodies in nature. Sulphur, in the solid state, ia 
also a hard substance, and to hold it in vapour requirei 
a. high temperature. But when these two substanceS) 
carbon and sulphur, are made to combine chemically, 
■0 as to form the substance called bisulphuret of carbon, 
their properties are strikingly changed. Instead of the 
compound being hard, it is a thin liquid, and ia not 
Itnown to freeze or solidify at any degree of cold that 
can be produced. Instead of the compound being diffi- 
cult to vaporise, it ia of allhquids one of the most evapoi>- 
able. Charcoal is ihe blackest substance with which we 
■IE acquainted ; sulphur is of a most lively yellow hue; 
but the compound is as colourless as water, A new smell 
and taste are acquired, and, in a word, there is not one 
point of resemblance with the component. These facts 
ikingly illustrative of the change of properties 
which fcHhwB on the exertion of chevtiical a' 
^Ken the ultimate particles of bodies 



CHAP. IV. ATTRACTION OP AFFINITY. 27 



I 

4 In all the instances already adduced^ it may be ob- 
served that the bodies concerned are of a different nature 
fbm each other. Thus^ gold was said to have an affinity 
for mercury ; lead for tin; tin for copper; sugar or spirit of 
wine for water ; and air of a certain kind for lime. In 
fact; it is a property of affinity^ that it never takes place 
lietween two bodies of the same kind : lead has no che- 
mical attraction for lead^ nor tin for tin. In a former 
chapter it was shown that lead attracts lead ; and that 
two pieces of that metal^ when brought into close con- 
tact, adhere with great force ; but it was by cohesion. 
One of the chief differences between chemical and co- 
hesiTe attraction is^ that the former takes place only 
between the particles of different kinds of matter, 
whereas the latter takes place between particles of the 
same kind. If 10 particles of zinc and 10 of copper be 
combined, they will form 10 and not 20 particles of 
hrass : for the attraction concerned in forming the brass 
is affinity, which can only join particles of a different 
kind ; and, consequently, if there be any junction, two 
particles of a different kind must in each case combine 
to form one compound particle. Ten compound par- 
ticles being thus formed by affinity, and all of them 
being necessarily of the same nature, although com- 
pound, these will attract each other by cohesion ; for 
this force, and not affinity, possesses the power of joining 
similar matter. 

We find it sometimes stated, that the attraction 
of cohesion is otherwise called homogeneous attraction, 
because it takes place only between the particles of the 
same kind of matter. There can be no greater mistake: 
cohesion takes place between both homogeneous and 
heterogeneous matter. Two thin plates of different 
kinds of metal may be made to cohere with great force 
by a forcible stroke, and this is often practised in the 
arts. The silvering on the backs of glass mirrors is 
retained by cohesion : water, whether liquid or frozen, 
adhere? to solids by cohesion : mercury rises in capiWax^ 
tubes by the same power : glue sticks to wood, axi^ 



SS WUSMBTM OV OHZVUniT.'- 

Tarnish to tnctAla, in the saine manner ; i 
DumberlesB oilier instances. 

Another great difference between cohesion and ti 
B the following : — Wlien the particles of boilies co 
here, they can always he overcome by what we al 
mechanical force, such aa pulverising, idling, &c. But 
mechanical force is of no avail where affinity has tiken 
place ; for let the compound he ever bo conipUlelj 
divided, each particle of it will consist of all the in- 
gredients which entered into the composition of the 
original compound, and in the same proportions, and no 
mechanical contrivance can separate thetn. 

In this place it should be observed, that when a hoily 
annot, as far as known, be decomposed into two m 
dore ingredients, it is said to be a simple gubirtanee; 
but otherwise, it is called a compound : thus, copper il 
a simple suhstanco ; but brass, as consisting of rini 
and copper. Is compound. With regard to compounds 
the bodies of which they are composed are said to bi 
t etateof ehemical combiitation, or united or combine< 
fay affinity, or by chemical attraction : and this slat 
of chemical combination is contradistinguished from wha 
's called mechanical mixture, which merely means thi 
mixture of bodies without being attracted to each oihe 
by affinity. Thus, if filings of zinc and filings o 
copper be mixed by stirring them together, they are ii 
tate of mechanical mixture ; hut if they be melte 
leather, they form brass, and are said to he chemicall; 
combined. Or if a Uttle essential oil and a little wale 
be shalcen together, they mix in such a way that th 
small particles of each can he seen unchanged ; this is 
mechanical mixture : hut if a large portion of spirit e 
irJDe he poured on, they all dissolve, and the separal 
parts can no longer he distinguished : this is dien 
chemical combination. Mechanical mixture can b 
distinguished from chemical combination by the cit 
eumstance, that in the latter there is always a change c 
properties more or less complete ; wbeteaa uv (ba fontic 



CHAP. IV. ATTRACTION OF AFFINITY. 29 

the resulting properties are a mixture of the original 
ones, both being recognisable. 

We have now to enquire whether or not affinity is a 
force of very extensive operation in nature^ whether it 
acts in the case of certain kinds of bodies only, or whe- 
ther it is a general property of matter. The facts 
known, seem to warrant the inference that there are no 
two bodies between which an affinity does not subsist^ 
however great the repugnance apparently manifested 
by them for each other, and however successfully that 
fepuguance may oppose their combination. 

There are many causes which operate against affinity, 
and sometimes with such effect as altogether to prevent the 
^tual exertion of its influence. If a piece of iron and a 
■piece of sulphur be brought into contact, no change is pro- 
duced. If the iron be reduced to filings, and the sulphur 
'to powder, and both be mixed, still no change takes place; 
hut if this mixture be heated, they both melt, and form 
a substance essentially diflferent from the original ingre- 
dients; they have, therefore, entered into a chemical 
combination. Here it is obvious that the combination 
was not efiected, or, in other words, that affinity did 
not act, until the ingredients were melted, that is, until 
their cohesion was suspended : and it appears that the 
imperfect suspension of cohesion produced by the me- 
chanical operation of pulverising the ingredients was 
not sufficient to permit the exertion of chemical attrac- 
tion, until the force of cohesion was entirely overcome 
by the agency of heat. Hence the cohesion of the 
matters employed was the antagonist to the force of 
affinity ; and until that was overcome, affinity could 
not act. 

To take another instance : if a piece of marble be 
thrown into water, it does not dissolve, because the af- 
finity between the particles of water, and those of the 
marble is weak, while the cohesion of the particles of the 
marble amongst each other is strong. But if very strong 
vinegar be siddedj the particles of the vinegar exert a 
stronger aMDity to the marble ; its cohesion is thexeioie 



I 



virtually less powerful, and less able to resist, and the 
marble begins to dissolve. It dissolves slowly, however, 
for the cohesion still offers considerable TeEiHtance, al- 
though it is at length overcome ; but if this resislAitce of 
the cohesion be still further lessened by breaking dotm 
the marble into line powder, the force of affinity becomes 
an overmatch for the much weakened force of cohesion, 
and the marble dissolves with facility. 

In this case the cohesion is much weakened, but it is 
by no means completely suspended; every particle of tho 
powder being a small aggregate resembling the original 
mass in Qroperties. But a greater number of surfaces 
being now exposal Co the action of the vinegar, greater 
eflfect can be produced by the affinity in a short time. 
The cohesion is never entirely suspended until the par- 
ticles totally disappear in the liquid; or, as it is ez.- 
pressed, until they dissolve. 

In the same manner, if a portion of the precious stone 
called sapphire be thrown into oil of vitriol, the stone is 
not affected, because its cohesive force is more power- 
ful than the affinity exerted by the acid; but if ihe 
oohesive force be lessened by reducing the stone to a fine 
powder, Che force of affinity prodominaCca, and the stone 
dissolves with facility. 

In all cases where a solid dissolves or disappears in a 
liquid, so that the whole becomes liquid, and as trani- 
parent as before the'solid was added, the resulting liquor 
ia called a solution; the solid before its solution was the 
tolvend; and the liquid which effected the salution ia 
called the solvent or menaeruum. 

The instances which have been adduced show, that 
cohesion is the antagonist of affinity ; where ihe cohesion 
of any two substances is strong enough, it will prevent 
or retard the exertion even of 'the most powerful af- 
finity. On the other hand, where the affinity ia weak, it 
may he much assisted in its efficacy hy lessening the 
force of cohesion. 

As cohesion is the antagonist of affinity, so also is 
acuity the antagoniat of cohesioa ; and. -wWne^ei 't^ 



OHAF. IV. ATTBAOTIOK OF AFFINITY. 51 

former is very strong, the latter has a proportionate ten- 
dency to give way. If sugar be thrown into oil, it re- 
mains solid, because there is not sufficient affinity between 
the two bodies to overcome the cohesion of the sugar : 
bat if the sugar be thrown into water, the affinity of this 
menstnmm is so strong, that the cohesion of the sugar is 
broken down, and it dissolves. 

Heat sometimes increases and sometimes diminishes 
the force of affinity. In certain cases, we find that the 
affinity of two bodies is really rendered more powerful 
by raising their temperature ; in others, the affinity is 
apparently increased by heat, inasmuch as combinations 
are produced at a high temperature, which could not be 
in the cold ; yet the increase of affinity is but apparent, 
and the real effect of the higher temperature, is merely to 
lessen the cohesion of the bodies concerned, in a manner 
which will be explained in the chapter on heat, and toper" 
mit the natural affinity to act, which existed in equal power 
before, although it was overpowered by the superior force 
of cohesion. Thus, if alum be added to cold water until 
no more can be dissolved, the affinity of each for the 
other is so far weakened, that the cohesion of the alum 
can be no longer overcome : but if the temperature be 
raised, an additional portion will dissolve with facility. 
In this case, the increase of temperature must be sup- 
posed to exalt the energy of affinity, rather than to lessen 
the resistance of cohesion ; the diminution of the force of 
cohesion by this increase being very inconsiderable. But 
when we find solid substances — suppose two metals — 
refusing to combine at a low temperature, which evince 
the force of their affinity when they are melted, by the 
facility with which they combine, we must suppose that 
the chief effect of the heat was to subdue their cohesion^ 
and thus to permit their union. 

So far as to the increase of the force of affinity by 
heat. With regard to the diminution of affinity by in- 
crease of temperature, this effect, like the former, is 
sometijzi^ ival and sometimea apparent. 1£ \)Ot\\xv^ 
water be poured on daked lime, a certain poxtioiL ^JS^ 



ELEMENTS 






solves, nnd the water acquires a certain taste : bat in 
proportion as the water cools, more lime dissolves, anl 
the taste becomes stronger. The same observations appl|r 
Id magncaiaj and water at 91° is known Co diesi>l''e 
more Glauber's salt, than when hotter or colder. Hen 
then, is a direct diminution of the force of affinity bj 
heat : but in the fallowing case the same reasoning doei 
not apply. Common water contains a small quantity of 
atmospheric air dissolved in it, and to this it owes a iier- 
tain degree of the little flavour which it possesses: if tbe 
T he heated, it soon begins to discharge the air in 
ktebbleB, not because the affinity of water for air is Iw 
it a hij^h than at a low temperature, but because tbe 
it expands the air to such a disproportionate degree 
Hcompared with theexpan^^ion which the water undergoes, 
Aat Ihe force of affinity is no longer able to counteract 
; tendency of the air to resume its aeriform state. 
le water, as it cools, re-absorbs and condenses a new 
B.quaiitily of air. 

Besides the condition of cohesion, it appears, therefore, 
,t there is a state of a very opposite nature, which sn- 
■s the effectual agency of affinity, anil which de- 
(ome consideration. An air or gas is totally 
tevoid of any cohesive attraction ; and the distance 
its particles is so great, and maintained by so 
jowerful a repulsive agency, tliat there is considerable 
culty to be overcome, in. many instances, before a 
Riwmbinatian can he produced. This repulsive agency, 
I Irhich mechanical force can overcome, is called elasticity. 
Cases will be brought forward hereafter, in which two 
diff'erent kinds of air that possess a strong affinity for 
each other, will nevertheless refuse to combine, on ac- 
count of the difficulty of bringing their panicles into 
■uch contact as will permit tlie affinity to act: yet, if the 
distance be lessened, as by mechanically forcing or com- 
pressing the particles nearer to each other, they will 
combine with faciUly, and even with violence. And 
where this cannot be done, tlieunion may still be effected 
ty presenting tbe gases to each other ^vealei oS && 



caAp. IV. A'tntAcnov op affinity. 33 

Kpulsion which helongs to them as gases^ or^ more pro- 
perly speakings before this repulsive power can have 
attached itself to them ; namely^ at the moment of their 
generation^ or while they are yet in what is called the 
nascent state. 

It is true^ that in these cases^ heat ultimately appears 
to be the antagonist of affinity; not by diminishing the 
power of affinity^ as in the case just now adduced of 
lime and water^ but by keeping the particles of the gases 
concerned out of the sphere of each other's chemical at- 
traction. Thus^ rarity is as much an obstacle to chemi- 
cal affinity as density. 

But rarity does not always offer opposition to chemi- 
cal union : ihe affinity of some gases is of so powerful a 
Idnd^ that the moment they are presented to each other 
ibey combine^ and sometimes to the exclusion of the heat 
which maintains them in the gaseous state : hence they 
cease to exist as gases. Instances will be given hereafter. 
Having shown that affinity is a property possessed by 
all bodies ; that every kind of matter has, in all proba- 
bility, an affinity for every other kind of matter, although 
circumstances may prevent it from being exerted with 
effect, so as to produce combination ; we must enquire. 
Are there any limits to its operation ? has it a continual 
tendency to produce combination ? does combination sa- 
tisfy or lessen that tendency ? or, to speak metaphori- 
cally, is it an insatiable appetency of matter for matter ? 
A few facts of common occurrence will illustrate and 
answer these questions. If lime be left exposed for a 
length of time to the atmosphere, it absorbs from it a 
kind of air which is called fixed air, or carbonic acid gas. 
The absorption of the carbonic acid goes on progressively 
imtil a certain period, and then it ceases : thus, 100 parts 
by weight of lime will absorb 78 J of carbonic acid ; but 
the lime may be exposed for ever, and it will never absorb 
a particle more. This combination of lime and carbonic 
acid is found ready-formed abundantly in nature *. dv^ 
i» precisely such a compound; so also are limestoive, 
laarblej and various minerals. With regard to t\ve%e 

D 



V (ubstaDces, 




I 



(ubstaDces, dl very different in appeBrance, it ie remirk- 
able ihal the lime and catbonic acid heai U> each olher 
exactly the same proportion, 7^^ of the latter to 100 of 
the former ; it U therefore apparent, that when theae 
relative weights are preBenl, the affinit; of each {at 
the other is satiBtied, and the attraction, under ordmary 
drcumetances, ceases to be exerted any further. When 
bodies combine in such a way that the affinities me Hi- 
tiafied, they are said to saturate each other. 

lu the same manner, the substance called pouah hai 
an affinity to carbonic acid; and, when und^ proper cii> 
cnmstancea, will absorb it until 100 parts by weight of the 
former combine with about 46 of the latter; and then the 
abaorption ceases, because the elastic state of tlie gaa can 
be no longer overcome by the alBnity of the potash, now 
considerably weakened. So far the affinity of potaah for 
carbonic add in the elastic or at;riat stale may be said to 
he saturated or satisfied ; and a definite combination ia 
produced ; but, in fact, the affinity of the potash, unless 
under these circumstances, is not satisfied ; for if ita 
tendency to overcome the elasticity of the carbonic acid 
be assisted by any other power, as pressure, a new ab- 
aorption and combination of it will take place. 

TliuB it appears that potash combines with carbonie 
acid in two separate portions or doses : one dose is ab* 
sorbed spontaneously by the afSnity of the two bodies ; 
but this is limited by die counteracting tendency of the 
carbonic acid to remain in the elastic state. If the elas. 
ticity be counteracted by mechanical compreasion, the 
affinity ia again exerted, and a, new portion of carbonic 
acid, constituting a second dose, is absorbed. The 
quantity constituting the first tlose is aliout 46 parts bj 
weight; that constituting the second is nearly Qi to 
every 100 of potash. 

There is one thing that deserves remark with regard 
to these two doses of carbonic acid taken up by the 
potasli. It is an extraordinary fact, tliat each dose is 
precisely the same in quantity: so ^UU 4ti.^arts of 
nr&>Juc add unite to 100 of polaali tr 



CEAP. IT. ATTBAlOTIOK OF AFFINIT7. 35 

doae, 46 more will unite to form the second dose, and 
tbe potash will just contain twice as much in the 
second as in the first case. This is an important fact : 
it diould he well understood and rememhered, hecause it 
is an illustration of how comhinations in general are, 
efltoed whare a body has an affinity to different doses 
of other matter, A distinct chapter will be devoted to 
this subject. 

It has already been observed, that, as fftr as we know, 
all bodies have an affinity for each (^er, although there 
may be antagonist forces which prevent combination. 
We have now to enquire whether chemical attraction 
acts with equal force on every kind of matter. 

There are three substances in common use, and well 
known to almost every one ; magnesia, lime, and nitric 
add, commonly called aqua fortis. The nitric acid has 
an affinity for each of the other two bodies ; it has an 
affinity for the magnesia, and will combine with ic ; so 
also will it with the lime. Suppose, then, that these 
three bodies are mixed together ; what will be the 
consequence? Will they all combine together, and 
form one compound consisting of the three ingredients, 
as would be expected from the circumstance that 
the nitric add has an affinity for both of the other 
two? The result is curious and unexpected. Not- 
withstanding that nitric acid has affinity for both mag* 
nesia and lime, one only of these affinities is obeyed : 
the nitric acid attracts and combines with the lime; the 
magnesia is in no respect- affected or acted upon : it re- 
mains untouched and separate, while the lime is attracted 
by the nitric acid, and combines with it to the exclusion 
of the other.* It must be observed, however, that this 
atatonent is only true when the quantities of each of 
the three substances presented to each other are equal. 
The phenomenon is not the less surprising ; for, with 
even the smallest quantity of acid, its equal division 
between the other two bodies might have been expected. 
We Mv now prepared to answer the question piopo^edi 

•Davy, 
D 2 



, namely, whether or not affinity is equal in all 
bodies, or are some affinities stronger than others? The 
fttcts above detailed show that all affinities are not equally 
strong, and that the affinity of the nitric acid for lime 
ia stronger than its affinity for magneaia. On account 
of this preference, as it may be called, which one body 
nanifeits in attracting another, such cases have been 
fc designated elective attraction. 

,We shall now suppose a case somewhat different with 
K JR^ard to the same three bodies. Suppose the nitric acid 
1 magnesia to have already combined, and suppose 
e lirae to be Clien added to the compound ; the result 
I be precisely what might have been inferred from & 
knowledge of the former fact. The magnesia will be 
gdetached from its combination with the nitric add ; 
i lime will take its place, will combine with the 
Plaitric acid; and the magnesia, which had been formerly 
' inviiibie, and in a state of solution in tlie acid, will now 
re-appear and remain perfectly separate. The former 
compound, being subverted, is said to be decompounded 
or deampoeed ; and the process is called decomponition. 
Most of the great changes which are constantly taking 
place in nature, are instances of decomposition. It is by 
decomposition that the solid rock becomes covered nitlt 
fertile soil : it is by the same agency that the soU throws 
up its verdant clothing ; that growing plants ar« con- 
verted into animals by assimilation ; that animals at 
length fall into decay, and return into iheir original state: 
in fine, it is by decomposition that the great natural 
processea of renovation and decay are kept in a state of 
perpetual circulation. 



CHAP. y. HEAT. '37 



CHAP. V. 



HEAT. 



Fbom an experiment already described*^ it appeared^ that 
if two pieces of lead are brought into contact by the 
application of considerable force^ they are attracted pow- 
erfully^ and are held together so firmly^ that the weight 
of several pounds will be required to separate them : if 
•the pieces are brought into less forcible contact^ they do 
not cohere. Now^ as it has been proved that they have 
an attraction for each other^ and^ as in the present case^ 
a small force is insufficient to call that attraction into 
operation^ it is manifest that there is some other power 
acting which antagonises and overcomes it, and which 
must itself be overcome before the attraction can operate. 
In short, it appears that the plates of lead, when brought 
together, resist the force of the hand which effects the 
contact, and also their own attraction of cohesion, unless 
the force be very considerable. The obvious inference 
is, that this resistance is a repulsive power exerted by 
the pieces of lead ; which may, however, be overcome, 
and which then gives way to cohesion. This principle 
is called repulsion ; it is the antagonist of attraction : 
its existence under a variety of forms is certain, and 
can be rendered manifest in many ways. 

Attraction and repulsion being forces opposed to each 
other, they must very materially modify each other's 
agency. Yet they do so without confusion, for each has 
its proper limits ; and we find that where one commences, 
the other ends; or, in other words, if attraction takes place 
between two particles at one distance, repulsion "w\\l taVe 
phce a Utile further off: these distances, however, ate to 

* Seep. 12. 

n 3 



88 lOiranm or tniuuiriKT. kiUfa% 1 

small as to be insensible, and can only be known to exist 

by inference. There are cases of another kind, in nhidi 

ses can be made visibly attractive or repulsive of each 

other, merely by varying the distance. Thus, if 3 glass 

rod be electricaJJy esciled, by rubbing it with silk, or, 

I Indeed, with any substance ; and if it be brought near a 

[ Kght body, as a piece of cork, suspended by a silk thread, 

L the cork will be attracted : in a moment after it will be 

I lepelled ; but if the glass be Iwoughi with a sudden jerk 

■ariose to it, the cork will be attracted ; if the glass be 

V ^rithdrawn a little, the cork will be repdled, and so on 

t jdternatdy. Or a magnetised bar being freely suspended, 

I Jtnother magnetiEed bar is applied to it, en(l to end; if 

W'iihej repel each other at one distance, ^ey can be made 

" fto attract each other merely by lessening the distance. 

' iffithout either asserting or denying that the agent is the 

jutme in all, these experiments are here made use of to 

JQustrate the position, that matter exhibits attraction 

■nd repulsion at diiferent distances ; these distances 

being so minute as to elude our strictest scrutiny, and 

.bdng only discoverable by indirect means. 

The theory of Boscovich affords a representation of 
the constitution of matter with r^ard to attraction and 
repulsion : it is the one at present generally adopted, 
and it may be necessary to give a summary of that palt 
of it which relates to our present subject. Boscovich 
conceives that the ultimate particles of which all matter 
is composed are mere points without extension, and of 
coarse incapable of bdng divided. These points of 
matter have the property of repelling each other at the 
smallest distances ; the smaller the distance, the stronger 
Ihe repulsion : so strong does the repulsion become as 
the particles approach very near each other, that no pos- 
sible force can bring them into absolute contact. The 
admission of this repulsive agency becomes necessary to 
the theory ; because, as the material particles are sup- 
posed to have no extension, there would be, but for the 
repalsioii, nothing to prevent all the poiiW.B com^oeing a 
-Wass from being forced into one, and lima Niauii iSifc 



magnitude of die mass be anniliilated : in this sense he 
understands the particles to be impenetrable. Ab the 
constituent particles cannot be brought into contact, it 
follows that matter must be porous, however hard or 
heavy it may appear ; and as the repulsion varies with 
the distance, the particles are capable of approaching to 
or receding from each other, or, in other words, of oc- 
cupying more or less space according to circumstances. 
The particles being repulsive of each other„it may be 
asked why they do not repel each other with more efifeet, 
and separate to such distances as would cause the solid 
lo fall to pieces. To this question the theory provides an 
answer. Although at the smallest distances the particles 
of matter are repulsive, there is a limit beyond which 
they are no longer so : beyond this limit an attractive 
force comes into operation, which prevents the disso- 
lution of the solid state. Even the attractive force is not 
without its limits ; for if the particles of the solid be 
leparated a Uttle farther from each other, the attraction 
not only ceases, hut repulsioii once more seta in. Thus 
doattractionsaltematcwithrepulsions, until these changes 
terminate in that universal attraction which is called 
gravity. In solids and liquids, the particles or points 
preserve their distance from each other by being placed 
'n the equilibrium between the attractive and repulsive 



Such is the outline of the theory of Boscovich, aa far 
aa the constitution of matter is concerned; or rather, as 
far as the chemist is interested in the constitution of 
matter. Tht theory ia much more compUcated, by the 
multiphcation of attractions and repulsions, than modem 
philosophy requires, remarkable aa it is far adherence 
to facts only as guides. It will perhaps occur to the 
reader, that the existence of points of matter without 
extension, aa maintained by Boscovich, Leibnitz, and 
odiers, is very difficult to understand ; so intimate is 
H|Ae association, in the mind, of matter and magnitude, 
i so diScait is it to comprehend how ■poiivl.s -KYiAi. 




I 
I 

I 



magnitude can occupy space. It is vko, 
however, to diEcuss £uch lulijects. To the student 
who findE it impossible to adopt opinionB reroltingt*, 
Lis ordinary habits of thought, which found iheii cMcf 
dainiE to admisdon on the difficulty of disproof, it mi} 
be some satisfaction to observe, that the evidence on to 
■ut^ect cannot be of b. very convincing kind, when «e 
find Leibnitz asserting that the particles of matter have 
no extension ; Descartes mainiaiuing that extension is 
their only property; Locke defining an atom to be "f 
continued body under one superficies;" and Berkeley i^ 
nying that matter exists at all. It is fortunate for the 
chemist, that a knovvledge of the ultimate mechanism of 
matter is not necessary to the prosecution of his t»- 
searches ; although it must be admitted, that eertaik 
hypotheses respectinji; the ultimate molecules of matter 
may assist his imagination in conceiving Geveral of the 
most interesting natural phenomena. 

Whatever the nature of repulsion may he, it is found 
.to be in some manner connected with what we call htai: 
, corpuscular repulsion is found to he increased hy the 
presence of heat, and diminished by its absence. When 
heat increases tl)e repulsion between ttie particles of a 
body, these particles must recede farther from each othv 
in all directions ; and if (hey all take more remote 
stations, it is cThvious that the bulk of the hody must be 
increased : it is now, in fact, larger, although the qaaa- 
tity of matter remains the same, and it is said to be 
expanded. On the other hand, if a diminution of ,heat 
lessens repulsion, the attraction of cohesion is permitted 
to exert itself with more force : the particles of a body 
thus cooled will draw nearer to each other ; the body 
will consequently occupy less space, although the quan- 
tity of matter remains the same ; and the body, in this 
case, is said to be coatracled. 

From the constant and evident association of heat 
with repulsion, philosophers have at length conceived 
that they are both eilects of the same cause. As to the 



^ 



QHAP. 7. HBAT. 41 

nature of the cause there has heen much idifference of 
opinioD. Some suppose that heat is matter of a peculiar 
nature; others conceive that heat is a condition of 
matter^ and that it consists in a vihratory motion of the 
constituCTt particles of bodies. It is a question of great 
difficolfy, but of little importance. 

Be this as it may^ the language of the material hypo- 
liieds of heat being so much more convenient and intel- 
ligible than that of the undulatory hypothesis, we shall 
086 the former in preference. 

Heat is admitted by the philosophers of the present 
day to be the principle concerned in repulsion : and 
beat and cold are known to produce expansion and con- 
traction in all bodies. Heat is^ therefore, the antagonist 
of cohesion. Chemists have thought it necessary to 
make a distinction between the senses in which the 
word heat may be taken. In its usual acceptation, it 
merely means the effect excited on the organs of sens- 
ation by a hot body. But as this must be produced by 
a power in the hot body independent of sensation, that 
power is what chemists understand by the word heat : 
and to distinguish between the effect and its cause, the 
temi caloric has been substituted. The introduction of 
this term appears altogether unnecessary, when the 
sense in which the word heat should be understood 
is explained. Caloric means the cause df the sen- 
iation heat : and there seems no reason to fear that 
the perception of heat by the organs of sensation can 
ever be misimderstood to be the agent in chemical phe- 
nomena. 

The first question that occurs with regard to heat is. 
Where is its abode ? where does it proceed from ? The 
answer to these questions is, that it exists every where ; 
and can be obtained from every thing. 

It is ea^ to prove that all bodies, whether solid, 
liquid, or aeriform, contain heat, even when they appear 
to our sensations to be absolutely cold. They can be 
subjected to such processes as wiR cause its evciVvitioii •, 



and hence it is inferred, that these bodies must 
contained heat throughout their Eubstance in a 
and iiiBensihle state. 

If a piece of soft iron, at the common temperal 
the atmosphere, be struck smartly on an anvil ■ 
hammer a. few times, it becomes hot ; and if the 
mering be dexterously continued for some time, tfa 
may be hea(«d red hot. It is common among sm 
procure fire in this way. By nibbing two pieces 
wood together, so much heat may be generated as 
them on lire ; and this mode is resorted to by 
natione. In tubbing even two pieces of ice togetl 
some time, they will gradually melt; wluch provi 
heat must have been evolved. 

The instances that can be adduced of the ex.tr 
of heat are by no means confined to soUds: thi 
various fluids, which, when mixed, undei^ a coi 
able elevation of temperature ; such is the cai 
instance, with oil of vitriol and water: and if a 
tity of that liquid called nitric acid be poured oi 
turpentine, the mixture bursts out into flame. H 
considerable quantity of heat must have existed 
or both of these Uquids, in a quiescent state. 

That heat exists in airs or vapours is equally c 
Btrable : there are instances of the quantity be 
great as to produce ignition and flame. Thus 
brass tube, close at one end, of about a quartei 
inch diameter, and very even in the bore, be fitle 
a piston, well leathered like the piston of an air- 
so that when it is forced down the tube no air c 
csape. Then let a hit of the fungus called 
■bout a fourth part of the size of a pea, and well 
be thrown down into the bottom of the tube, and 
piston be introduced. If the air in the tube b 
compressed by powerfully forcing down the pisto 
a sudden strong stroke, so much heat will be ext 
from the air that the agaric will ignite. A philosi 
toy of this kind is now commonly sold. An . 



CBAF. V. HBAT. 4S 

flame may be instantaneously produced by mixing two 
tm, which will be described hereafter^ called phosphu- 
letted hydrogen and oxygen. 

That bodies contain heat would^ however^ be suf- 
ficiently proved ^thout the preceding experiments^ 
merely by showing that^ under ordinary circumstances^ 
ihej can be made colder ; or^ in other words^ that 
heat can be abstracted from them ; which could not 
happen if they did not contain it. The force of this 
xeascming certainly depends on the truth of the in- 
vdved position^ diat cooling a body is the same as 
withdrawing heat^ and that cold is merely the absence 
of heat. This is the opinion of philosophers at present : 
Imt the reverse has been maintained^ and striking ex- 
periments have been brought forward to support the 
ophiion that cold is an agent of a distinct nature from 
heat, and not merely the absence of it ; but they have 
Med in proving their object. The Florentine acade- 
micians placed a mass of ice, weighing 500 pounds^ 
before a concave glass mirror^ in the focus of which 
was a sensible thermometer. The spirit of wine in 
the tube immediately began to subside ; and when the 
mirror was covered^ the spirit rose again^ proving that 
the depression of the thermometer was not attributable 
to the proximity of the ice. From this^ and similar 
experiments^ it has been by some inferred that cold is 
matter sui generis; but the doctrine has few if any 
adherents. If we consider the process which causes 
the rise of the thermometer when a heated body is 
before the reflector^ and if we admit that cold is the 
absence of heat^ then^ by supposing the course of the 
calorific rays from the heated body to be inverted^ we 
find that ice should depress the thermometer^ inasmuch 
as the thermometer then becomes the source of heat 
instead of being its object. 

As all bodies contain more or less heat at all temper- 
atures which the world ever experiences, and as a por- 
130D can be withdrawn from them, or added^ it becomes 



I 

I 



* CHKHISrKT. 

a question, what are the effects produced upon 
by the loss or by the addition. 

If heat be the principle of repulsion, and ' 
gonifit of cohesion, the consequence must be, 
withilrnwtng heat, the attraction of cohesion 
allowed to act with more energy ; the partidei> 

body cooled will be drawn nearer together ; and 

the total bulk of the body must be diminiKhed. Henc^ 
the effect of cooling is to diminish bulk. If a body, in 
consequence of being cooled, has its panicles hwugW 
nearer together, there wil! be a greater number of parlitlM 
in B given bulk than before. Thus, if a bar of iron, lO 
inches long, could be so far reduced by cold ai V 
measure but Sf inches, it is obvioua that any gins 
inch of the bar, in its contracted state, must conldll 
a greater number of particles of iron than before. The 
quantity of matter iij any given hulk of a body, as hat 
been already explained, is called density, or specific gts- 
vity ; and it follows, diat in the case of the bar of iron, 
its density or specific gravity is increased by coolingi 
because a greater quantity of matter is brought into S 
smaller space. And it may be received as a general law, 
which, however, is not without exception, that the efffect 
of cold on all bodies is to lessen their bulk and to in- 
crease their specific gravity. Conversely, it might easily 
be anticipated that, by adding heat, the repulsion of the 
material particles would be increased, the bulk would be 
increased, and the specific gravity diminished: this, ac 
cordingly, is foiuid by exjieriment to be the case ; and 
the Jaw applies to matter, whether in the solid, liquid, 
or gaseous state. The expansion of solids and liquide 
for equal additions of heat is not always equable ; when 
high temperature, a further addition of heat will 
cause greater expansion than at a low one : but tliil 
not apply to gases ; they expand equably. 

The expansion by heat, and contraction by cold, 
bodies in the aohd, fiuid, and aeriform state, is eaidli 
sboini fcf experiment. 



!. SEAT. 4tf 

T of iron, made to fit into a gange, with ease, 
)1d, will, when heated in it, no longer fit it, but 

»me so large, that it cannot enter it On being 
it will resume its former diraenHiona, and again 
•auge. If the bar be made to fit the gauge, at a 
iture approaching to redneBS, bo aa to remain 

would drop out when coaled. In this experiment, 

r, it is important that the tempetatuie of the 

[self should not be changed. 

glass flask with a long neck, and 

I A with cold water, be heated, the 

ill b^n to rise in the neck, and, 

me time, the Tessel will be 

full : when cold, the water will fall 

its former level. This involves 
iciple of the thermometer, 
n air-tight metallic veesel^ 

water as high as A, all tbe rest 
Uled with air, and having a tube, 
ending into the water, furnished with 
■e heated until the air become hot. 



I this experiment, 
dperatuie of the 

with a stop-cock 
hot, its tendency 




and will increase its elastic force so much that it 
ess BO stronglj on tbe surface of the w&tet, V\»i 
lie stop-cock ia opened, a jet of water ■wiii \]e 






pr(>jecte(I to a great distance. ^Vlien cold, the Vt 
will shrink to its former volume ; and if t!ie slop- 
cock be opened wliile its jeUpipe is immersed in naler, 
a quantity of water will rush in, to supply the place oE 
that which the air had expelled. A bladder ptitlj 
filled with ^r, if held before the fire for some tin^ 
will appear full ; hut, on cooling, it will shrink to it* 
original bulk. Air and all va;>ours and gases espud 
by heat equally ; the rate is TiVijlh part of their whde 
bulk for every degree of [he thermometer. 

In all these cases, the addition of heat caused expin- 
don, whether the body concerned was soUd, liquid, iff 
aeriform ; and its abstraclion occasioned diminution of 
volume. But diminution is not caused alone by th> 
ahsCraction of that quantity of heat which had been 
added. If the body be cooled lower, for instance] 
much below the natural temperature of the surrounding 
medium, the particles composing the body appraaeh 
Btill nearer each other, and the contraction increases. 

As expansion and contraction are, with a few exoep- 
tiona, invariable results of increase and diminutiim oE 
heat, expansion has been made use of as the measure of 
heat, and the principle is adopted in that simple iastm- 
nient called the thermometer. The thermometer is no 
more than a glass tube of very small bore, with a tnilb 
blown on its end. The bulb and part of the tube sre 
filled with mercury ; and when heat is communicated 
to the mercury, it expands and rises in the tube. The 
height to which it rises is the measure of the heat j or, 
in other words, the more or less the mercury riK«, 
the greater or less is the intensity or degree of the heat. 
A scale is affixed, on which different degrees are en- 
graved ; of these degrees, two are the representativea o£ 
certain remarkable phenomena constant in their agencj 
and immutable in their period of occurrence, namely, 
the points at which, under certain circumstanceii, dis- 
tilled water freezes and boils ; ail the rest are arbitrary 
dirisions of (he space between iheae two invariable 



OAF. ▼. HEAT. 47 

points. Dififerent diyisioiis are adopted in different 
coontries ; a drcumstance to be lamented^ as comparison 
of temperatures thus becomes inconvenient. 

Water, at certain temperatures^ furnishes an ex- 
oqition to the law of expansion by heat, and con- 
tnction by cooling, which is well worth consideration. 
If a glass flask, with a very long neck, be filled with 
pQie water at 60° to the middle of the neck, a ther- 
mometer being immersed; and if some of the means 
bereafter described be used for gradually reducing its 
tooperatare; it will be found that, in proportion as 
tbe water cools, it contracts and sinks in the neck, 
OBtil the thermometer arrive at 39^^* The cooling 
IvoeesB being continued, the water, instead of con- 
tneting still more, b^ns to rise again in the neck, and 
continues to do so until the water freezes, and then it 
suddenly expands much more. Thus S9i[° is the ther- 
mometrie degree at which water is at its maximiun 
density ; above or below that, its density diminishes : 
and hence it is obvious that ice is specifically lighter 
than water : this is the reason that ice floats on water. 
Dr. Thomson found its specific gravity 0*92, that of 
water being 1*00. 

The expansion of water in the process of freezing 
was discovered by Paulo del Buono, an Italian philoso- 
pher ; and the fact was published by his associates of the 
Aceademia del Cimento (Society for Experiment). This 
has been long known; but it has escaped observation, 
that these academicians had also made an Experiment 
which evinced that the maximum density is above the 
freezing point, although they drew a wrong conclusion 
from it ; and of this any one may convince himself, 
by considering the experiment detailed at p.l06. of their 
Transactions. They also proved the enormous force 
with which water expands in the act of freezing: 
spheres of glass, silver, and gold, were burst by the 
contained ice. A sphere of brass was burst in this 
jxuauaer, which Muachenhroek calculates to liave Te« 



red a pressure from within equal to [37730 1 

ler stiiking results have since been obtained. 

'.t Imving been already ehown that the addition oi 
heat exiiands bodies, and that ita ahEtractioii diminiabu 
them in volume, it follows, as a necessary consequence, 
ihat heat lessens density, and tAat cold increases it. If 
a vessel be filled to its btim with cold water, and heat { 
applied, the vessel soon begins to overflow, because flw 
water expands. When the water comes near its b(ril- 
ing point, the vessel still remains full, although nuoh 
has left it. The panicles of the water must, then, have 
been repelled by the heat to greater distances from eadi 
other- Sut if the vessel, now full of tioihng water, be 
allowed to cool, (he water shrinks below the brim of the 
vesgel ; for the heat or repulsive quality being dissipated, 
the particles of llie waier resume their original distance 
from each other. The consequence is, that hot water 
weighs lighter than cold, the bulks being alike ; as b 
eaaily proved by pouring a pint of boiling water into 
one basin of a pair of scales, and a pint of cold into the 
other ; the latter will preponderate. It is but another 
mode of expressing the same fact, to say tbat hot water 
is specifically lighter than cold water : and the position 
ii equally true with respect to all bodies, whether Eolidi, 
fluids, or airs. The change of density, according to the ' 
change of temperature, is easily proved. Let a hollow 
glass ball be so prepared that it barely sinka in a vessd 
of water at the temperature of 60°. If iced water be 
poured in, the deneity is increased by the cold, and 
the ball, now speciticaily lighter than the water, ascends 
to the top. If hot water be added, the density is lea- 
sened ; the ball, rendered specifically heavier than the 
water, sinlcs to the bottom ; and it may be made to rise 
and fall alternately. 

The foregoing considerations enable us to obtain 
some insight into the structure of matter, and to appre- 
ciate the value of Boscovich's theory, so far as it need 
be gppUed to the facta wluch iiave come under ob- 



CBiP.y. SEAT. 49 

lerration. It was shown^ when noticing the theory 
of that philosopher^ that the particles of matter are sup- 
posed to be repulsive of each other at small distances ; 
attractive at distances a little greater; and at still 
greater distances^ once more repulsive. It appears that 
the repulsive agent concerned is caloric^ and that its oper- 
stioQ is a counteracting force to the attraction of cohe- 
aon. Solidity is, therefore, expressed by the following 
condition : — the constituent particles of matter are kept 
St a certain distance from each other by two forces ; co- 
hesion, which draws them together, and calorific repul- 
flOD, which keeps them asunder; and their actual 
distances from each other are precisely between the 
limits of the two forces: this is the equilibrium of 
fiosoovich. The addition of artificial heat, by increas- 
ing the repulsion between the particles, must augment 
the bulk of the solid, the cohesive force being so far 
weakened; and the abstraction of heat, by lessening 
the repulsion, must permit the cohesive force to act with 
more energy. It may, therefore, be laid down as a 
truth, well ascertained, that the effects of caloric and of 
cohesive attraction are opposed, and constantly antago- 
nise etch other. I am not aware that the following facts, 
which are highly illustrative of the subject, have been 
observed by others. At page 12. a figure is given, re. 
presenting two pieces of lead, with a scale-pan and weight 
attached, showing the force of the cohesive attraction. 
If, while the scale-pan is well loaded, the pieces of lead 
he heated, their attraction is lessened by the repulsive 
a^ncy exerted by the heat, and the lower piece falls off. 
The most convenient mode of heating the two plates of 
lead is, to direct a jet of burning hydrogen, pressed from 
> bladder furnished with a stop-cock and^pipe, upon the 
jonction of the plates. The heat need not be very great. 
If a wire of zinc, about 2 inches long and i^^th 
of an inch thick, be supported at both ends, while 
ft bng wire hangs from its middle, sustaining about 
7 avoirdupois pounds; and if, in this state of tVviT\g;&, 
^^uae be held under the zinc, its attraction of cohesion 

B 



will be so fir antagoniEed by calorific repulsion thi 
line win first bem! a little, and then suddenly bit 
two ; but there will not be the least symptom of fi 
If an empty glass globe, with a long neck, be set 




polished brass ring of a chemical stand, on wtri 
merely rests without fitting down into it more th 
inch, the neck forming an angle of about 45° wil 
horizon, it will remain in tlnat position while it is 
But if a voluminous flame of a spirit lamp be a] 
far below, yet so as to heat the globe and the ring 
a repulsive force will be generated between the glai 
the brass, and their contact with each other will 
far lessened, that, after some time, the long neck v: 
down, provided that the original posture of the 
was balanced so exactly as to be overset by the bd 
disturbance. If a few drops of water be let fall 
very hot iron plate, they glide over it in all dire 
with amazing volubility ; and they do not adheri 
■s they would were it cold : for repulsion acta be 
them. Or if ardent spirit be made to boil gend 
glaas flask, globules of ]ierfect sphericity will dano 
the surface without coalescing : for they repel each 
as well as the surface over which they ghde ; ant 
are spherical, owing to the cohesiovi of the liquid, ' 
h not countet&cieA by any aUracfton Srom 'l\y& t 



V. HEAT. 51 

h. If a small disc of tin plate be hung from 
lire by a wire^ and if a similar disc be made to 

to the under surface of the former by the inter- 
n of a few drops of water^ and pressing the discs 
ately until they adhere^ they will remain in con- 
But when the heat of a spirit-lamp is applied 
leath^ the cohesion of the water will be so much 
led^ that the lower disc will immediately fall off, 
i expansion produced in bodies by the addition of 
eat^ and the condensation or contraction occasioned 
abstraction^ having been so far investigated^ it is 
3 be enquired what other effects may be produced 
natter^ in its three states of existence^ by a further 
in or subtraction of heat. 

I piece of lead be heated^ the first effect of the 
on is to produce expansion and diminution of 
r : the heat continuing to increase^ the particles 
lead continue to repel each other more and more; 
It length they are so far separated as greatly to 
1 their attraction of cohesion : hence^ the solidity 
lead is broken down and it melts. If the melted 
be allowed to cool^ the heat or repulsive power is 
awn^ and the cohesive attraction of the particles 
is permitted again to exert itself: hence the par- 
re drawn together more and more as the heat is 
ted ; and at lengthy when the lead is cool^ the 
is have arrived at that contiguity to each other 
constitutes solidity^ and the metaJ is as hard and 
je as before. 

this instance^ the heat necessary to liquefy the 
as necessarily considerable : but there are other 
which^ under ordinary circumstances^ are always 
f as water; yet the analogy still holds: for^ as 
uidity of lead is caused by heat^ so also is that of 

if its temperature be sufficienUy reduced^ it will 
i solid ice ; and the only difference is^ that water 
s to be cooled much lower than lead before it 
es. 

melting of ice is, therefore^ explicable Va l\ke 

E 2 



puisii 



■ame manner as that of lead ; die lirst effect oT llieliett 
is to cause repulsion between the particles of the ice, and 
this goes on until the repulsion almoet balances ihe it- 
traction of cohesion ; then the solid ice breaks ilovn 

If we continue the application of heal still fnrtber, 
the EBnie process of expansion goes on ; the particles Of 
walcTj as the heat increases become more and morere- 
e of each other ; and at length the balance beiweffl 
1 and repulsion is aubverted, the attraction " 
and the repulsion prevails over its antagonist 
force. When this happens, the watery particles at on» 
expand themselvei so far asunder as to alter altogeiba 
the state of the water, which now is converted into whrt 
is called slfiim, or vopojir ; and the more this is heltedr 
the more it expands, unless it be confined. 

Steam, while hot, is in a state very like that of the 
atmosphere: its particles are at a much greater distancS 
from each other than those of water. If these partide* 
be brought nearer each other, either by removing ths 
beat which is the cause of their repulsion, or forcing 
them to approach by mechanical pressure, tliey coalesce, 
and the result is water. 

It appears, therefore, that water is capable of under- 
going three different changes, by being made to contain 
three dlfTerent quantities of heat. It may exist in At 
state of a eolid, a liquid, or a vapour or air. In thi 
same manner various metals, sulphur and a vast numba 
of bodies, are capable of assuming these three states, te- 
cording to the degree of heat : and it is not only unde 
some one or other of them that all the boclies in natun 
exist, but it is supjwsed that every kind of matter i 
capable of assuming each of the three states, althougl 
as yet we do not, in every case, possess the means a 
communicating heat sufficient for the purpose. 

I'he sum of the preceding statements is, that all bodie 

contain a certain portion of heat, which, being nainia 

to them, Js insensible unless calleA forth ; that if to i 

aolid a sufficiency of heat be coraimuivoatoi.^^'Ki^**'* 



CHIP. T. HEAT. 53 

becomes a fluid. If another portion of heat be added^ 
the fluid boils away^ . or evaporates in the form of a 
Vapour, or gas. The question then occur^^ If bodies be 
deprived of their heat, do they pass retrogressively into 
the other states? and the answer must be affirmative^ 
provided the bodies can be sufficiently cooled. Thus, a 
8oIid that has become liquid by heat, will again become 
solid by cooling ; and a vapour, if cooled, will become 
Hquid or solid, according to it^ nature. But there are 
Mme vapours which cannot, by any attainable degree of 
cold, be made to change their form : these are what 
ve called permanent gases, of which the atmosphere 
tt an instance. When a body becomes solid, which was 
not previously so, no matter how the change has been 
effected, the heat, that constituted the previous state 
is liberitted. When a gas becomes a fluid or a solid^ 
heat is always liberated and rendered sensible : and heat 
is also liberated when a fluid becomes a solid. These 
unportant laws can be illustrated by experiments easily 
executed. 

The substance known in the arts under the name of 
^ ammoniac is a hard, white solid, having a crystal, 
iine texture. Notwithstanding the hardness and heavi- 
ness of this substance, it is composed of two different 
kinds of air, or, as chemists call it, gas ; and it is easy 
for even the inexperienced to resolve it into its two con- 
stituent gases, by processes which, although he may not 
*s yet understand, he can execute. These gases are 
kuown to chemists by the name of muriatic acid gas and 
*ninioniacal gas. If powdered sal ammoniac be mixed 
with oil of vitriol in a common phial bottle, the phial 
^ shortly be filled with vapours. If a cork be adapted 
to the phisd, and a slender glass tube be fitted tight in 
a hole bored through the cork; and if another phial^ 
p€rfecdy dry, be inverted over the former, so that the 
glass tube passes up a few inches into it, the vapour will 
enter the second bottle : after some time, it will exipel all 
the common air with which the bottle was OTigmaXV'5 
^iied; and the bottle will now contain nothing "but tcvvjl- 

E 3 



riatic acid gas. If a bit of ioe be thrown into ihii 
bottle, and the bottle corked, the ice will immediUel; 
ntdt, and tlie gas will all disappear. That it has dii- 
appeared may be proved by suddenly drawing out the 
cork ; for commoTi air will rush into the bottle with edcIi 
violence, that a Elight report will be produced. The mu- 
riatic acid gas ha3,in short,entered into the ice — ithulo^ 
its form of gas — it has become a liquid; and, in ao doing) 
it haa parted with the heat which caused it to be a gu! 
the liberated heat entered the iee, and melted it into 
water. The experiment can be made in a much wore 
elegant and convincing manner ; but to do so wouM 
render the description complete and the execution tioii- 
bleeome. 

The other constituent gas may be separated from ail 
ammoniac by mixing its powder with a little slakedlinMi 
heating the mixture in a bottle, and inverting a itj 
empty bottle over the glass tube, as before. If a bottle 
filled with muriatic acid gas, and another with ammo* 
niacftl gas, be closely applied mouth to mouth, so that 
the two gases can mix, but not escape, it will be found 
that, from being transparent and colourless Uke common 
air, they will, in mixing, immediately change to a dense 
white cloud, at the same time that the bottles will be- 
come warm. After some hours, the white cloud will 
subside into a thin, solid coating on the sides of tbe 
bottle, which is, in fact, the original sal ammoniac, le- 
generated from its two constituent gases. Thus, the 
gases, when mixed, pass from the gaseous to the solid 
state; in doing so, they both part with the heat which 
caused them to be gases ; and this heat is so great as to 
warm two considerable masses of glass. We have now 
to exemplify the case of a fluid passing to the solid 

A familiar instance is the slal:ing of lime. If on a 

piece of well-burnt roche-lime, its bulk of cold water be 

poured, it will be soaked up, and the lime will appear 

as dry as ever. In a few mmutcs \.\\e Wroe w^l swell 

Hp, burst, and become hotter tlian \ioii:vns viiWa, »xA 



CBAP. V. HEAT. 55 

donds of scalding hot steam will arise fh)m it In this 
ctK the water lost its fluidity, and formed a dry powder 
^mth die lime ; the heat which caused the water to he a 
fluid was extricated^ and it was sufficient to raise the 
temperature of the whole mass considerably. 

The last instance which shall be adduced is an analo- 
gmu ooe^ and is that of a solution of Glauber s salt in a 
f}m globe, described at page 19. This liquid^ as has 
been already mentioned^ will not crystallise^ or pass 
into the solid state^ until the vessel is shaken or opened^ 
«r the surface of the solution touched : it then suddenly 
lieoomes solids and the temperature rises. 

Conversely^ when a solid becomes a fluids or when a 
fluid becomes a vapour^ or a gas, it might, from the 
forgoing facts, be anticipated that heat would disap- 
pear: it accordingly does; and so much of it is ab- 
sorbed and concealed, that the bodies concerned become 
odder than before. 

Thus, let 1^ pound of newly crystallised common 
Glauber's salt be reduced to fine powder and thrown 
into a thin glass basin, with 15 ounces of muri. 
Stic acid, and let the whole be immediately stirred 
lound with a glass rod : the powder, from being a solid 
(for its particles are solid), dissolves, — that is, passes to 
the fluid state, — and this it could not do without re- 
ceiving a supply of heat. The supply is withdrawn 
from the whole contents of the basin ; hence their tem- 
perature is reduced ; and so cold does the mixture be- 
come that a tube closed at one end, filled with water, 
sod immersed in it, will immediately freeze, even 
during the heat of summer. The heat thus withdrawn 
bas entered into the solid particles of Glauber s salt, or 
the solid water contained in it, and they, in conse- 
quence, have assumed the liquid state ; while the heat is 
concealed or absorbed in some way that is not easily 
comprehended. Or, if snow, and half its weight of com- 
mon salt, be suddenly mixed, they immediately become 
liquid : and the mixture, if the ingredients were oxv- 
gmalljrat the freezing pointy will be reduced to %^ ot 

E 4t 



40° below It. Professor Braim froze mercury wilh » 
mixture of snow and nitric acid. The same absorpiioo 
of heat takes place with certain melallic mixturet: if 
207 pains of lead, 11 8 of tin, and 28* of bismuth, ll 
iD filings, be mixed with I6l7 graina of mercury, ihB 
temperature will be lowered from (i+° to 18°.* It i» 
only Bome metals that answer this purpose. When goM 
and mercury are combined, heal is produced. (OUm- 
iurgh, Phiiomtph. Trnng., JVb. 122.) 

The most common instance of the conversion of * 
fluid Into a gas is evaporation ; and to prove that be*t 
is withdrawn from the bodies concerned, and cold pii>- 
duced, a simple experiment will suffice. If some strong 
ether be poured on one's hand, it instantly evaporates,— 
that is, changes to the stab; of vapour ; and as in oidci 
to do this, it must derive a supply of heat from somi 
source, it does so from the hand, and there is a sell' 
aalion of intense cold produced. Persons who have no 
made such subjects a part of their study, are apt to cDn< 
ceive that there is an inherent coldness in the ether, bS< 
they are the less surprised. The following experimen 



IS sufficii 



Let 



thermometer he plunged into a phlsl of ether for a 
time ; no change takes place, proving that the ethe 
possessea no natural coldness: but let the thermometerh 
taken out, and instantly the mercury be^ns to sink 
evincing that the cold was produced by evaporation fron 
the bulb. If a very thin glass tube, closed at one end 
and filled with water, be wrapped round with muslin 
and if the tube be frequently immersed in strong elhel 
allowing what the muslin soaks each time to evaporatt 
the water in a short time will be frozen. Blowing vari 
air on it will even hasten the cooling, because it pro 
motes the evaporation. By wetting the bulb of a thennt 
meter constantly with ether, and blowing on it with 
bellows. Dr. Franklin sank it 95° below freezing t; an 
a without blowing, Cavallo sank it 4° lower, f 






jIh. Mr. ' 
111 ObKrraliont, p. 



' i t'OA'WJt'a.'^rtxA.-na 



CHAP.r. HEAT. 57 

On the principle of evaporation^ coolers for wine or 
water are commonly constructed. A vessel made of 
porous earthenware is filled with water^ which^ by 
soaking through and evaporating^ keeps the water and 
any thing immersed in it cold. The porous vessels so 
generally used in Spain^ called alcarrazas, were intro- 
(iuced by the Arabians. In warm oriental countries 
they have been used for centuries. 

As evaporation takes place much more rapidly in the 
receiver of an air-pump when the air is withdrawn^ the 
cold produced is the greater: but the watery vapour 
onut be continually removed by the constant action of 
the pomp, which is a difficult and imperfect mode. 
Uie obviated this, by introducing some substance which 
^rbs watery vapour rapidly^ as strong sulphuric acid^ 
or certain earthy substances. In this way, by exposing 
a thermometer coated with ice, he promoted the evapo- 
ration of the ice so rapidly that the mercury froze. Pro- 
fessor Configliachi, of Pavia, also froze mercury by the 
evaporation of water. 

In some cases, where a gas or a vapour is formed or 
extricated from a liquid, although cold is actually pro- 
duced, it is not sensible ; for an approximation has taken 
phuie between the particles of the liquid ; it has become 
more dense, and even this approach to solidity causes an 
extrication of heat which counterbalances the cold, and 
Mnce the temperature is scarcely changed. This hap- 
pens, for instance, in the case of mixtures of substances 
which occasion that kind of apparent boiling in the cold 
*^ed effervescence, — as when dilute oil of vitriol and 
common magnesia are mixed fixed air is developed, the 
'lecesBary heat being derived from the liquid, which 
hence would become colder, but that it has suffered an 
increase of density. The liquor is now less fluid, that is, 
as might be said, more solid : heat is the consequence, 
and this supplies the place of the heat which had been 
withdrawn by the evolution of fixed air. Indeed, there 
can be litde doubt that in all cases in which cold is ^to- 
daced during sadden liquefaction^ and in wbic\i as\m- 



:e of density happens, the degree of cold i» r^iderid 
Ie«8 intcnec on account of being counteracted bf the 
evolution of some heat occasioned by the increased den- 
•ity. Such mmt be the case in the production of cold 
from concentrated nitric acid and snow. 

n the foregoing statementi it appears that heat his 
the effect of expanding, or, as it is called, rarefying all 
bodies to which it is applied ; that (he series of changes 
of form produced by this raiefaclion is from the solid to 
the fluid, and then to the aeriform state. A solid ex- 
jMied to heat first expands, and then becomes a fluid : 
the fluid then expands, and at last in an enormous 
ntio, and becomes a vapour or gas; which, if further 
heated, still further expands : but no other change of 
■tate happens beyond this. The converse changes are 
the contraction or condensation of a vapour by cold ; a 
nidden contraction in an enormcus ratio so as to form a 
liquid; u furtlicr contraction into a solid; and this may 
be still further contracted by a greater cold. 

It appears also, that during this series of changes of 
form, heat is either absorbed and concealed, or liberated 
and rendered sensible. 

Notwithstanding, when a solid is about to become a 
fluid, or a fluid a gas, the caloric, which is to constitute 
and be concealed in a new slate, must previously pass 
into the body in a sensible form ; and the process by 
which it becomes quiescent, and afterwards sensible, is 
extremely curious. 

We shall take water as the body in question, as it is 
easily made to assume the three states — ice, water, 
and vapour. If a thermometer have its bulb bedded in 
a piece of ice, the instrument will indicate the temper- 
ature of the ice : suppose it to be at that time 20°. 
Bring the thermometer, still immersed in the ice, into 
a warm room, the temperature of which is, perhaps, 70°j 
it begins to rise, indicating that the ice is receiving ca- 
loric from the surrotMding warm air. The thermometer 
(wnlinues torise, nntilit stands at 32°: until this period 
ttc See rewidaed hard and dry ; buX at S2P "A '\»tQms* 



CHiP. y. HEAT. 59 

moist; begins to meit^ and this melting process goes on 
imtllitis liquefied. Meanwhile the thermometer^ which 
rose progressively until it arrived at 32°, stops there ; 
and; all the time that the ice is slowly melting, re- 
mains stationary at that degree; notwithstanding that 
another thermometer, hung up in the room, indicates 
the air to be still 70°. As soon as the whole of the ice 
is melted, the thermometer immersed in its water begins 
to rise ; and it continues to do so from 32° until it ar- 
rives at 70°, which being the temperature of the room, 
it can rise no higher. It should be observed that while 
^e ice is melting, both the ice and the water are at the 
temperature of 32° ; and the water remains at that degree 
^e diere is any ice unmelted. 

From this experiment, we may reason as follows : — 
When the ice at 20° was exposed to an atmosphere of 
70^, the heat of the air in the room entered into the ice, 
and raised its temperature until the thermometer stood at 
32 , when it became stationary. The first question that 
occurs is, Why did the thermometer remain stationary ? 
can we suppose that the heat of the atmosphere ceased to 
enter into the ice ? Such a supposition must not be ad- 
mitted; for then no reason could be 'assigned for the 
continued melting of the ice, and for the rise of the ther- 
mometer from 32° to 70°, after the whole was melted. 
The only other way in which the question can he put is, 
Mheat continue to enter the ice, although it had not the 
effect of causing a rise of the thermometer ? It can be 
shown that this is the truth. As soon as the ice rose to 
32 it began to melt, and continued to do so until it was 
*D melted, when the thermometer again began to rise, 
because heat continually entered the ice ; but, during the 
^nge from the solid to the liquid form, it was so con- 
cealed in the substance as to be incapable of afiecting the 
thermometer. Heat continued to enter until as much 
i^as absorbed as was necessary to convert the whole into 
Water ; when, there being no longer any ice to render 
the concealment of caloric necessary, the latter exvlereOi, 
became sensible, or free, and then affected tlie tYxeimo- 



conceive how | 



I 



60 

meler. However iliffintlt it miiy be ti 
heat can bt entering into tlie ice at the moment of mdl- 
ing without raising its temperature, it is certainly tmo, 
and can be proved by a very Bitiafaclory experiment 
Talce a pound of ice, broken small, at the tempcratnreoE 
32°, which it will exactly reach if exposed to a soniB. 
what higher temperature, until it begins to grow a litde 
moist ; ta this pound of ice, add a pound of water iieated 
to 1 72" ; mix ihem together : the ice immediately meits, 
and reduces the temperature of the water from 172° 
to 32", which waa ita own original lemperatnre. Whit, 
then, has become of the 140" of heat loEt by the hot 
water ? There is no other way of explaining it, than by 
admitting that ihia quantity of caloric has entered the 
ice, has become concealeil in it, was just sufficient by 
its concealed existence to convert that much ice inlv 
water, and was the exact quantity which would have 
raised an equal weight of water 14rO°, although it did 
not heat the ice at all. 

Perhaps the following experiment is still more strongly 
iUustrative of this doctrine: — Take a pound of water at 
32°, and a pound of water at 172°; mix them, and the 
resultiog temperature will be found 102", the arithmed- 
cal mean, or midway number ; for one baa lost as mudi 
ai the other gained. But substitute an eqnal weight of 
ioe at 32" for water at 32", and the resulting tem- 
perature will be still 32". The difference, iherefore, 
tetween a pound of water at 32° and a pound of ice at 
82° is, that the former not only contains as much heat 
M the latter, but such an additional quantity as would 
be adequate to heat anotherpoundof water 140^, although 
it IB concealed. 

It appears, therefore, that when ice arrives at 32", and 
the thermometer ceases to rise, a great quantity of heat 
must enter it before it can be converted into water ; anS 
that whatever heat ia required to raise ice at 31° to water 
at 32°, is vastly greater than what would be necessary 
larsise mater from 32° to 33", 01 iw from 31" to SS"; 
and, to concave the change more iptenseVjj'ABBaai'Vft 



CHAP. y. HEAT. 61 

imderstood liiat the whole quantity of caloric thus re- 
quired is employed in converting ice at 22° into water 
at 32^ 

' Were it not necessary to the liquefaction of ice, that 
A large quantity of heat should he ahsorhed ; and were 
the opinion true, whidi prevailed previously to the era of 
Blacky that the change of ice at 32^ into water requires 
but a very small addition of heat ; the consequences^ 
'^ays that celebrated philosopher, would be dreadful: 
torrents and inundations arising from the sudden melt- 
ing of snow and ice would be irresistible ; they would 
tear up and sweep away every thing, — and so suddenly, 
^t mankind could have great difficulty to escape their 
ravages. It is the same slowness of liquefaction, he 
observes, which enables us to preserve ice in summer in 
ice-houses ; and the melting is still further retarded by 
the difficulty which external heat experiences in pene- 
trating the building. Snow continues on many moun. 
tains during the whole, summer in a melting state, but 
melting so slowly that the whole of that season is not a 
sufficient time for its complete liquefaction. — (^Black's 
Lectures, i, 118.) 

Mercury in this respect resembles water in its habi- 
tudes. A mass of frozen mercury, with a thermometer 
included, if brought into a warm room, will rise to 39° 
or 40° below zero, and remain so during the whole time 
that the mercury is melting ; for this is its freezing point. 

Let us now follow up the original experiment a little 
further. The ice having been all melted, and the ther- 
mometer having ascended from 32° to 70^, which is the 
temperature of the room, no further increase of temper- 
ature can take place unless artificial heat be communicated. 
If the heat of burning fuel be applied, the thermome- 
ter again begins to rise, and at length reaches the tem- 
perature of 212°. But here it stops ; and, as happens 
in the case of the melting ice, no heat that can be ap- 
plied will raise it a degree higher. A new process ivoyt 
sets in : huhWes form in the bottom of the vesseV iie^X. 
die source of beat; they rise to the surface, bxeaiV, «Si^ 



discharge steBm, which is, in fact, a gas compose 
particles of water united with caloric, and so hi^; 
pulsive of each other as to occupy no less than 1 
times ■ more space than, the original water. Hene 
extreme lightnesB and thinness or rarity. This fi 
ation and discharge of Eteam-buhbles constitutes wb 
caUed the boiling of water. 

During tins process, the steam forma continBally; 
its temperature, as well as that of the water, is c 
nually 212°: the water, therefore, when it arrivi 
that degree, undergoes a change of state ; calorific ri 
sion overcomes the cohesion of the water ; steal 
farmed ; and all further addition of heat enters inti 
game kind of concealed existence as it does in me 
ice, and instead of raising the temperature, is espe 
in forming steam until the whole of the water is b 
away. But, after this absorption and consequent 
Teraion into steam, heat may he applied with efibct, 

• T)iU dHnmiiulInn ii » dlflirent tnm what l< Inftnible fnr 
CTpet imnra of Oy.LuBae, vli lffir7-3««P,imil IBSSitglBOf.*: 
jon ™ Hni(, *c. SOS.), that It ij nRMiarj loexiJliln tlir iBMino-ln w 
deduce It By ulculallen lifbuMKi onlheniiiimltlan that Evan 



walET lately adaMnl by the Ipttlalature. vli. S5S1SI 
mud by eUplB's tflblH, 9535(07 grain! at m". 



iieo, wouW CKpand into 1713786 cubic Inchoa. The lUKallc grail 
aoBio It «1S= U, iherrfore, ones complied xiib air at e&o ; awT Wf 
BchBi of it Bttgh 14 6§S7. Theipecitlc gtavilj of Meaia eDupureri 
ilr of the nine tempiMature as Ittclf li O-SISl : end 100 euticllUI 
Eteam at 00° would wi'lgh 190173 gnlna. 



k 



tarn Mr. VVaR'i e 



(179S cubic Inchei) oFEteBinat ilS° liver; near the uutb. But Di. . 
buttle iM na£ perfectly prcciie in tii opinion, "—<Lccfwn% I. ic7,) 1 



Q&AP. y. HBAT. 63 

the steam^ by beiDg enclosed in a proper vesBel^ may be 
made to raise the thermometer higher in proportion to 
the heat applied. 

Thns^ in the heating of water between the tempera- 
tures of 32? and 212? , there are two distinct stages at 
which remarkable phenomena happen. At 32^, the 
thermometer remains stationary^ and will not rise a de- 
gree higher while any ice remains unmelted : after this^ 
it ascends until it arrives at 212"°^ where it again remains 
stationary. 

All the time that the thermometer stands stilly heat is 
accumulating and becoming concealed; during the first 
stage in the water produced^ and during the second in 
the steam: and the heat that is thus accumulated and 
concealed is what constitutes the fluidity of the water 
and the vaporific form of the steam; hence the terms ca^ 
hric of fluidity, and caloric of fmporisation, which merely 
mean the concealed heat of water and steam. It is^ there- 
fore^ no more than what might be expected^ that water 
contains much more heat than ice^ and steam much 
more than water. 

Although it has been stated that water cannot be 
heated beyond 212^^ on account of the change of form 
which it undergoes and its conversion into steam^ this 
statement is only true under certain limitations ; it is 
necessary to the production of such effects that the steam 
should have liberty to escape. If it be under sufficient 
constraint and cannot escape^ and if the containing vessel 
he full of water^ steam will not be formed ; the water 
must then sustain all the additions of heat^ and its tem- 
perature must rise proportionately. In this way the 
Water may be raised to any temperature^ provided that 
the vessel is close and sufficiently strong to resist the 
violent effort which the water would make to form steam. 
According to Muschenbroek^ lead melts in the water of 
a Papin's digester when the water is heated under due 
pressure. Lead melts at 6l2°. When water under 
pressure is coni^derahljr heated, if the restraint \)e t^« 
mored there will be a sudden, formation oi stewn. , «u 



quanlity of steiun will escape, a proporlioDate ijiunlil 
of heat will be absorbed from ihe water, and will becon 
concealed in the steam, and the tem^rature of the wM 
will immediately fall to 212°; because all the he 
above this quantity was absorbed by just as mm 

But in making this experiment, if the quantity 
■watec contained in the close vessel or boiler do not t 
ceed one fourth of the whole volume of the Teasel, I 
results will be very different. In this ease a tempi 
ature of about 680° will convert the whole of the ws 
into steam : for, notwithstanding the great presn 
which exists in the vessel, and which opposes the for 
ation of steam, the tendency of that high temperature 
produce the elastic stale U adequate to overcome I 
opposition of the pressure. IntermeJiate ratios of wat 
compared with the volume of the containing vessel, « 
afford corresponding ratios of steam, compared with I 
unchanged residual volume of water. The same hoi 
good with other liquids, except that the space occupi 
by the vapour, and the temperature necessary for 
formation, so as to overcome the pressure, will be d 
ferent for each. 

Thus, when water is exposed, under ordinary circui 
stance, to a Eufficient heat, it is the easy escape of I 
steam that prevents the healing of the water beyo 
213°; but when the steam is confined, the temperatt 
may be elevated above that point in proportion to t 
force which confines it; from this elevation, however, 
immediately descends again to 212°, as soon as I 
steam is at liberty to form, the quantity of heat whidi < 
casioned the increase of temperature being thus removt 
It should here be observed, that 212" is the boili 
point of water only when the barometer stands at '. 
inches : at 31, the boiling point is 213-76 : at 29, it 
but 210-19 : in a common vacuum, it is 70". 

tt is now of importance that we should take a surv 
of the two processes which are. o^^osed to the meldJ 
of ice and the vaporisatioii of watei -, ns.niA'j , "iie a 



KT. 



VXAT. 



ifenwlion of itesni wiil the freezing of water ; and It 
nil! appear ihat the phenomena of both are preciiely in 
iceonjance with the facts detaileil on the converse tide. 
Since water at 212" absorbs a large quantity of heat, 
nhich converts it into Bteam, but is not sensible to 
ihe Ihermomeier, we tnigbt expect that a given weight 
of sieani at 212° should contain, and would coin- 
iiiiinicate, much more caloric than a similar weight of 
wiler at 212". This Is, accordingly, the case r for if 
» ^oand of steam at 212° be received into 5-56' 
poands of water at 32^, the former wilt be condensed 
into water ; and the whole, amounting to 6-5H pounds 
of water, will have the temjierature of 213". The tem- 
perature of the steam (now water) baa not been reduced, . 
jei 5-56 pounds of water have been raised from 32° tg J 
212°, that is, 180° for each pound, or 1000 (180= x 1 
S'J6) in aU. Hada pound of water at 219", instead of ^ 
1 pound of steam at 913°, been mixed with the 5-56 ' 
pounds of water at 32°, the resulting temperature would 
only have been 64° instead of 212°. Hence the num- 
ber of degrees of heat which steam at 219° contains in 
• lilent stale, and which does not elevate its temperature, 
ii 1000. 

If the temperature of the water be now reduced, it 
"ill sink progressively to 33°, or the freezing point: 
lint It (his degree, it will be recollected that ice begins 
Id melt, and in so doing abEorbs and conceals a very 
lifge portion of caloric ; consequently, when the water 
i" returning back to the state of ice, we should expect 
W have this portion of caloric liberated and rendered 
wnwble. Accordingly this happens ; and that it does, 
ie following facts are sufficient proofs : — In the cool- 
ing of water, it may be reduce<l many degrees below 
33°, without freezing, provided that it be not agitated, 
■od that it is kept perfectly still : Dr. Thomson 
«Po!eJ it as low as 5". Suppose, then, that ila 
tfmperature Is reduced to 20° without frteiing. K 
•e coramun/tMfe a (rem ulcus motion to ihe vialer, i 
m^i pariJoa will be saddenly converted inW \ce-, Oat 




1 lb Ae pitT ia w taUnett. I>Bii^ ike tnexing, ihe » 
T laric of ftuditj will be lOicmed in sndi qaaatity U 
I .«01 niae the wlule tmpennire to JS" ; a deai pT«i( 
that the eoDcealed caloric of the water was eKtrioted 
and rendered eeitBble so as to nise ibe themionietcr 
12". Similar pbenoineiui have be^i observed in to 
aolidification of otho' sobstasces which remained fuK^ 
« fbe lempentnre at which thej naniraUj become con- 
crete, itr. Keir Elates *, that sulfAuric acid, when of 
■p. gr. 1'78, the density at which it most readily freew, 
may be cooled to £9° without doing so. Agilaiion tba 
make* it suddenly freeze, and the temperalure iosUnlly 
rises to 4^°, its freeting poinL 

That water in the process of freezing parts with 1 
quantity of heat, which bad been latent in it, ie proTtd 
bj the fact that, in order to be reconTerted into vaUr, 
solid ice must receive a large Gupply of heat &om SODK 
external source. If this quantity of heat derived frunn 
exlfmal source must be combined with the ice in order 
to convert it into water, it is very obvious that, in die 
contrary process, the water must part wilh tlie wn^ 
quantity of heat in order to be restored to the solid atlK- 
The beat parted with by the water is not sensible in the 
ice, because tbe temperature of the latter ia not highH 
than that of the former ; it is not laietit in the ice, be* 
cause, if it were, the ice woidd contain sufficient laKnt 
heat to liquefy it, without the necessity of deriviog ■ 
■upply from any external source, which ia contrary » 
Citahlished fact. 

Jt is owing to the lar^e quantity of latent heat giWD 
put in tbe process of solidification, that a considenUB 
period of time is occupied in the congelatmn of ■ miff 
of water exposed to an atmosphere below 52°. Tlw 
process commences by small portions of tbe water shoot- 
in;; into crystals of ice. These dismiss their latent beilj 
■ which becomes for the moment sensible in the Bor- 
rounding water, and BtiU keeps it in tbe liquid 

I .e^ll(isophlcBlTiiMitBtfior.t,\1«l. 



_ 1 



uer, however, presently imparts this heat to the 
ml the temperature being again lowered, new 
9 of ice are produced, and heat again lieieloped : 
!8 until the water is completely 



lay be proved in the moat direct manner, that 
vater is undergoing the process of congelation, 
maintained at the fixed temperature of 32", it 
Ltly dismisses heat ; which is received by (he sur- 
ig air, and becomes sensible in it. Let a highly 
e air thermometer be placed o\et a vessel con. 

water exposed to an atmosphere bdow S'l" ; while 
icesE of ooiia;elation is going on, the thermometer 

continually affected by a current of air proceeding 
lie water upwards, and it will indicate a higher 
sture tlian the tempersture of the surrounding 
It appears, therefore, that the water in the 
of congelation imparls tn the air immediately 
t the caloric of fluiiUty which it dismifsea ; and 
?air, thus becoming lighter than the eunounding 

a all that has been said, 
w manifest, that when 
Its calorie is absorbed, 
does not affect its 
tCure ; and, converGeiy, 



liberated, and becomes 
■ in the surrounding air, 
water becames sleani, 

is similarly absorbed, 
es not affect the tem- 
I! ; and when steam 
9 water, its concealed 
extricated. 

annexed figure re pre. 

'jliple apparatus adapt- 
Uoflh, 



It a 



f 2 




I 



be made altogether air-tight. A is a sphere of coppeK 
tontaining cuarsely poirileTeii ice. B is a thermometer] 
with its scale engraved on the stem ; its bulb is immejBed 
in the ice ; it is fastened into the neck of the sphere by 
meBTiB of a perforated air-tight cork. C is a slop-coijc 
communicating with the interior. Suppose that, at the 
commencement of the experiment, the mercury of the 
thermometer immersed in the ice stands at 10°. The 
heat of a lamp being applied, the temperature of the ice 
rises gradually until it reaches 33,°, and then the thermc 
meter ceases to rise higher. Meannliile, the ice begins to 
melt, and, after some lime, it is all converted into water. 
As soon as this happens, and not until then, the thenno. 
meter again begins to rise : it continues to do so until it 
reaches 212°, and then it stands still again, provided dul 
the stop-cock C is open. For now, the heat entering al 
the bottom, passes into the water, and joins or combina 
vrith some so as to form steam. The steam is formed in 
bubbles, like those of air, at the bottom of the vessd, 
and, rising to the surface, issues with force through the 
stop.cock : nor can any application of heat beneath raise 
the thermometer higher, so long as the steam can freely 
pass o£F. Let the stop-cock be now shut : the thermo- 
meter will instantly begin to risi 
previously passed off in the stea 
■o ; it must, therefore, remain in its sensible form in 
the water, and the temperature would continue to rise, 
if the heat beneath were sufficient, until the whole 
apparatus would burst in pieces with the force of > 
bomb. But it is not safe to let tlie thermometer riw 
more than as many degrees as will prove the fact. When 
the thermometer indicates that the temperature of the 
water is 232°, let the stop-cock be opened ; there will 
be an instantaneous gush of steam, and the water will, 
in a moment, be reduced to the temperature of 213°; 
the excess of heat now finding a sudden vent through 
the medium of the steam. 

The relation between caloric and the three fomu of 
water way be considered a tj?e TikQatiB.'u.''o (A ■&» ■» 



; for the heat thai 
> longer do 



lUlviii between cttoric and all other matter, as far as the 
LB beer examined. All bodies, in changing 
meir state, render heat either latent or sensible. If a 
■olid becomeB s fluid or a gas, or if a fiuid becomes a. 
ps, caloric is absorbed and rendered latent ; and if a 
gta becomes a fluid or a solid, or if a fluid becomes 
Nlid, caloric is liberated, and becomes sensible. In 
Buny eases, where caloric is absorbed, and an abundant 
supply can be obtained, the loss of it is not readily 
peruivcd ; this ia the case when water is converted into 
•■■■3m by artificial heat. But where free caloric cannot 
I- abundantly supplied, heat is abstracted from all the 
i^rfonnding objects, even thoi^h they are at the ordinary 
itmperature of the air ; and they are rendered cold, be- 
ciUK the quantity of heat necessary to supply the portion 
■iMorbed during the change of state cannot be replaced 
ttilh as much celerity as the absorption took place. This 
<ritl explain the operation of freezing mixtures. 

In concluding this part of the subject, it may be 
HKeisary to revert to some facts already described. It 
lui been stated, that water constitutes an exception to 
tte general law ; as it does not contract from 39}j° 
Amnwards to 32°, but, on the contrary, expands. 
Bweral solutions are similarly circumstanced. These 
esceptions, however, may be but apparent, and may be 
wpUined vrith reference to the single instance of water. 
When a liquid is about to crystallise, it begins to expand; 
Uid the expansion ia supposed to be attributable to aD 
efflwt of the constituent particles of the crystal to attach 
tbenudves one to anotlier, acconling to a kind of polar 
trriDgeinent, similar to that which takes place in magnetie 
Hid electric attractions. It is to this elfort which pro. 
bably, causes the particles to separate a little, and expan- 
sion to result. When water is cooled to 39-J°, and becomea 
specificaUy lighter, it may be owing to this cause ; and, 
without this, it perhaps would not be an exception. 

It ha« been shown that all bodies in the ordinM-j ata«. 
contain a quandtj of csioric which does nol a.ffieo\. l5aK 
(Uy*™ of sensation, or the thermometer, like tiee ot %eft- 
f 3 



Bible lint, until some change is effected on the cond 
of the body, which liberates a part of its caloric, uid 
it into action. If a bar of iron, in this ordinary e 
be cut into Beveral lengths, each will take with i 
proper proportion of caloric. From this it ia plain 
any two or more pieces of iron of the same qtui 
quantity, and teiaperalure, no matter whether tbejr: 
ever fonne<l one piece or not, will contain the i 
quantity of heat : anil the same may be said of i 
metals, and of stones, woods, or any thing else. ] 
the other qualities of the body be alike, so also ami 
that one of containing caloric. Further, it ia an ofaf 
truth, that if two pieces of iron, the same in everj 
spectj be exposed to heat or cold — as, for instancej 
of boiling or freezing water, by immersion in it — j 
will both become equally hot or cold, as they will 
sorb or part with the same quantity of caloric, ' 

But if we take a piece of iron, and an equal wl 
of B different metal, suppose copper, and expose I 
to the same temperature, as by immersion in bo 
water, they nill both arrive, eventually, at the same 
gree of heat ; but they will have absorbed very diffi 
quantities of it in order lo do so. The same obi 
Htion, generally, may be applied to all the bodie 
oature, whether solids, fluids, or gases. 

Now, as bodies, in order to be brought to the i 
degree of heat, whether the highest or the lowest, 
require different quantities of caloric, the inferenc 
that different bodies, at every degree of temperal 
whether natural or artificial, must always contain 
ferent quantides of heat, the bulks or weights b 
Alike. Thus, the quantity of heat that would i 
one kind or state of matter 10°, would raise ana 
but 8'. Or, to explain the matter more geuerall 
appears that different bodies are so constructed by 
ture, that they require different quantities of heat to i 
them to the same temperature. And if equal qi 
tiCies of heat be made to enter il\ffereM\»iditB,thef 
v«*e thf bodies to different tem^eiatates, TWa (»; 



caUed the rapacifi/ of bodies for heat ; 
quwdty Df heat that is lliua required for any _ 
icular body, to raise it to a certain temperature, ia callej' 
Id tpeeifie caloric. 

The same kind of matter, while in the same stal«, has 
•IwijB the same capacity for caloric' : at least, this is 
<ne within a moderate ran{>e of temperature. Suppose 
itie body to be water, and that we take a pound at ()0°, 
and a pound at 213°, that is, boiling: each of these 
pMUda contains a different quantity of caloric. When 
ffliieil, the effect ought to be, that, as the capacity of 
wh pound of water for caloric is the same, and as the 
liHter must give to the colder as much as will bring both 
td^ same heat, that degree ought to be midway be- 
Iween the two heats, and may be found by adding 60 to 
ilS, the Bum of which, 272, being equally divided, give* 
136* u the arithmetical mean, and should be the re- 
•alliag temperature. That \3tj° will be the resulting, 
tanperature, any one may 
metring a thermometer into 
of boiling water and of water at 00". 

Here, therefore, there is no heat lost 
Ait: whatever the hot water lost,' the cold water is proved 
k> bave gsinei!. But when different ha<lies are con- 
wned, whichj as already obBervml, have ilifferent ca- 
Ittcides for caloric, the case is altered. For instance, if 
1 pound of water at 60° be mixed with a pound of 
>mcury at 313°, the aritlimetieal mean in this case, as 
in the last, is i3(i°. But, after shaking both of these 
lifaida well, so as to produce uniformity of temperatur^. 



he resulting .'^H 
self, by iiaaj^l 
jual weightd^^l 

unaccounted 



himself, by 
of equal weigl 



•TliUpaiKiDD 






, Crawford, 


ind Wilok^^H 


bibniiE^edin 


DUWlM by Dil'lDnE and Petri. 


Theiifllra; 


u 'he remS^H 


issiS 


rae 


heal orbudiei in 


TJn.d'eto 


t-;;sB: " 


nirbiMiuiilTrH 


nriri.1. bei 


R^ixnMlma'ntirKiU u 0UI2 


>iet-«ii the 


■pcciliclmDdfa 


body It two 
eildmoe ft 


the BUblblimei 




'^•.ntu.Obrd 


i<.IBaa,a,tttmt 


t of ono op 










)ded;thefa. 


'ihut'toiUne 


.™l cold w«er produce tho >rIlhiDHlciU mom. o 


Ij iboHl tha 


th.-,p«ili; 










maeoraea 




fxM that IK 




idi h; hesl a i«B,"«iu»«* 




ale K4/B, .■ 




out the Ust 




ftotiala «i7. 




p 4 




^^ 



I 

I 



nS ELEUENTS 0*' OB'Elt^t^ ^^^^^^H 

I we find that tlie reaultiDg heat, instead of beiag4^^| 
I uithmetical mean, is but 64-9°, or 171° lower: )ml^^| 
L this quantity of caloric remains unaccounted for. ^^ 
I The experiment evinces that the pound of metaaf 1 
1 was reduced from 212° to 6i-9° - hence it lost 147'I i I 
I which, bein)^ coramunicated to (he nater, raised it on^ I 
I' 4*9° : a"<', therefore, the quantity of heat which tvM» 
l« given weight of mercury 14'7'1'', would raise the same 
I weight of water but 4-9°, or one thirtieth. Thus, tk 
[' beat that would raise water 1°, would raise mercury 30°! 
water has, therefore, a capacity of containing heat 30 
times greater than mercury, without having its lempe> 
ature more elevated than that of the mercury. Or the 
aame fact is otherwise expressed, by saying that the 
specific heat of mercury is 30 times greater than ihit 
of water. If the specific heat of water be represented by 
unity or 1 , that of the mercuiy will be {^^ = ) 0-QSS, 
It may be ailmitted as a general truth, with very ft* 
exceptions, that all bodies require different quantitiea of 
heat to bring tliem to the same temperature ; or, iu othet 
words, that almost every kind of matter contains a quan- 
tity of heat peculiar to itself. 

Such are the chief facta which have been ascertained 
with r^ard to the ahaorption of heat by bodies, and ill 
existence either in a concealed state, without raising their 
temperature, or doing so in a less degree than it would 
Wher kinds of matter. Hiiherlo the explanations given 
hsve been confined to a simple expression of facts, fbr 
these there can he no mistake; and the language of 
tpectdalion has been avoided. It is now necessary to 
give some account of the two theories which have been 
most reUed on for the explanation of these phenomena: 
1 shall begin with Ur. Black's doctrine of latent heaL 

When Df. Black commenced bis lectures, in the uni- 
versity of Glasgow, in 1 757, the general opinion regard- 
ing fluidity was, that it is produced by a small addition 
to the quantity of heat which a body contains when 
;ADce raised to the point at which it is ready to melt; 
■etarn to the solid state depends ou a-sei^ snu& 



iminution of heat after it lias cooled to the melting 
oint; that a solid, when changed into a fluid, receive! 
D greater addition to its heat than what is indicated 
fler fusion by the thetmomeCer ; and that when the 
.uid liody is again made to congeal, it suffers no ^eater 
»s of heat than the ihernionieler indicates. But the 
niih is, that when ice or any solid is melting, it receives 

much greater quantity of heat tJian what is ini'. 
nediaiely after perceptible : and this great quantity 
iiinl be received, because it is the pause uf the fluidity 
liduced. ^Vhen the melted ice or other body is again 
Inul to become solid, it cannot do so without parting 
riih tile heat which caused the fluidity, and which had 
een concealed or latent. 

Previously to the time of Dr. Black, it was in th« 
use manner aupposeii, that when once water, or any 
iiiuid, exposed to heat, has risen to its boiling point, 
nhing more is necessary than the addition of a iillle 
lore heat to change it into vapour, And when tlm 
Bpour of water has eoolod so far as to be ready for 
ondeosation, it was thDup;ht that the return into the 
tste of water will happen at once, after losing a very 
mall quantity of heat only. But Dr. Black proved tliat 
1 the vaporisation of water a vast quantity of heat enters 
'; which afterwards is extricated during the condensation 
! rhe vapour into water. The quantity of latent heat 
DDtained in steam lie estimated by distilling 3 measurea 
f water into a worm immersed in 38 measures of 
'»ier at 52° : the 38 measures were heated 71° higher, 
lenre, S measures in steam heated 58 measures (that is, 
2j dmes as much) 71° higher : the total quantity of 
iWnt heat in the steam is, therefore, found hy multu 
Ijing 71° by iSj: the product is 899}°. But the 
^ginal three measures of water were at 62°, and they 
ere raised to vapour of 912°: therefore l60° (diflfer- 
iM of 52" and 242°), the sensible heat of the steam, 
inst be subtracted from 899}°; and 'he remainder, 739°, 

ihe latent heal of the rapoar; or, making allowaticefc 
' liispersian anil lose of heit. Dr. Black estinialeA l-Vft 



1 

I 



I 






latent heat at 744'', — a number which Mr. Watt t^f 
wariU changed to ^00° or 9^0^. Lavoisier eetimaleiil 
at lOOO" ; and this ie generally adopted. 

Dr. Black conEidered heat to be a substance of a dji* 
tinct and peculiar nature, " susceptible of union or com- 
bination with bodies, similar to those cotnbinatiini 
which the chemist observes between Domberless varielin 
of substance:" and he conceived that, in cases of boib 
expansion and fluidity, a combination with heat tabs 
place, but of a difierent kind in each. Heat enters vM 
vapour and into melting ice in the same way ; it eoia- 
bines ; docs not heat ; but merely conslitntes the n> 
porific and Uquiil form. In fine. Dr. Black conceind 
it a point fully eslablished, that when a fluid is raieed to 
iu boiling point by the copious application of heat, in 
particles sutldenly combine with a great quantity d( 
beat ; and their mutual relation is thus so far changei^ 
that they no longer attract each other, and form dra^ 
of liquid, but avoid each other, and separate to a virt 
distance, and would separate much further, but for the 
pressure of the atmosphere," 

Dr. Irvine was the pupil of Dr. Black, and his sue- 
eesBor to the chemical chair of Glasgow. He toA 
altt^lher a dl^rent view of the cause of the dissppeu. 
ance of heat in liquefaction and vaporisation. He sup- 
posed that the absorption of heat into the latent state ii 
ttot the cause of liquefaction and vaporisation, but tb( 
effect ; and he attributed the absorption to what is called 
change of capacity for heat, or that quahty of mattel 
which causes one kind to be more or less heated thai 
another by the addition of the same quantity of heal 
This unequal effect of equal increments of heat wi 
distinguished by Black and Irvine, about the same time 
by the term capacity. The 140°, that disappear whe 
ic« is melted, was called by Black talent heat: heat 
•BTted it lo be the cause of fusion, to comlnne cliemicaU 
with the solid, and to form a substance different fnn 
both, — ihqmd. This opinion was conddeted by Irrii; 



' tWH ». HBAT. ?5 

linot sufficiently comprehensive : he did not aUovr the 
enlriuice of Uteiit beat into bodies as happening upon 
liiiFerent principles from those which always direct the 
operadons of heat upon matter ; he imagined that latent 
fiestieonly a caseofwhat occurs in any aSecIion of bodies 
by heil, and that the caloric exists there precisely in the 
ume way as at other times. He thought that something 
more happens in fusion than Black imagined ; that the 
cipacity of water for heat might be found to exceed that 
of ine, is afterwards he proved experimentally ; and that 
1 new reason might be assigned, why ice, wMIe roclting, 
refuaea to admit an augmentation of temperature. The 
reison is, that it is then changing its capacity : from n 
substance easily healed, it becomes one that is heated 
<rilh difBculty. All fluid bodies are healed witli more 
ihfficHlty than when solid ; not because fluids transmit 
heU more slowly, for this is the contrary of the fact ; 
Init because the same quantity of caloric will heat a solid 
> greater number of degrees than it will a fluid. Ca-i 
fiatj is no more than the espression of the rise or fall 
'I temperature produced by equal quantities of caloric 
upon different bodies. He concluded, as a general law, 
that the capacity of all soUda for heat is increased by 
Auion, and that of all fluids by vaporisation. It appears, 
ihen, that beside Black's discovery of the great quantity 
of caloric necessary for converting soUds into fluids, 
■wlher remarkable allerarion is produced in the habit* 
(rf the body with regard to beat : from requiring but a 
roiall quantity to raise Its temperature a certain number 
nf degrees, it has become a body requiring a great quan- 
tily to produce that effect ; therefore, in fusion, the fluid 
brmed must, on account of this change of capacity, 
Kquire a supply of caloric to enable it to remain even 
It the same temperature with the surrounding bodies^ 
(t is clear, that if a solid be converted into a fluid of an 
nereased capacity, it must absorb heat, which will ex- 
libit the same phenomena as latent heat ; and the same 
pplies to ibe conversion of a fluid to the aeriform ata\e> 
■Ms explanation is not opposed, but supplemtntai, \» 



I 




Black's doctrine. Both theories admit iheei 
lai^e quantity of caloric iluring furion : Irrinel 
difiera in offering an explRiiation of the enlarge 
the Bpeciflc heat of the fused body, and in • 
■ny pecoHar or unusual comhinaiion of caloric." 

In commenting on this doctrine. Dr. Black tepBei M 
the following effect : — " Dr. Irvine imagities that it il 
not necessary to suppose a special coinbination of mUKI 
to lake place with caloric, which, while thus combined, 
K called latent heat. The explanation, it is said, maj 
be as well derived from the fact, that a body while ii 
its fluid stale has a greater capacity for heat ; that it 
abBorbs mora heat in order to rise one degree than whol 
n the Bolid form. Thus, ice is said to haye less capacity 
Jian water : when ice melts, a quantity of heat TitaH, 
therefore, enter the water produced, without msliDg 
" when water freezes, heat must leave dw 
freezing water, without learing it colder. The absorp- 
tion of heat inlo the melting ice is, therefore, notth* 
cause, but the consequence, of ite liquefaction ; while llK 
n of latent heat from freezing water is not the 
le, hut the cousequence, of becoming solid. Here, 
I, the change from solidity to fluidity is not account™ 
for, although it is the chief phenomenon. Fluidity » dA 
attributable to cessation of cohesion ; for how, tbni 
would it be restored? and we know that cohesiveattraclJia 
does still act in fluids. If it be maintained, that sensible 
heat increases or diminishes the distance of the partidn, 

I and thus acts on cohesion, why is not this an invariahl* 
effect ? and how happens it that water may be cooled to 
24°, without being acted on by cohesive attraction. Mil 
being converted into a solid ? By agitating snch ora- 
eooled liquids, heat is liberated which before was litent, 
and a pan of the liquid solidifies ; this latent heat wW 
the cause of its protracted fluidity." 
To this Dr. Irvine seems not to have been Me V 
furnish an adequate reply. He says the theory of C* 
juma'es asserts that the calovic rus\ves wlo ihe ice, ^ 



I 



[ing and satisfying iis capacitjr ai 
iL by ihe same action : ihe fusion, the it 
^ty, and the he^Lting of tl)e body, uccordinjr lo the 
Ir capacity, are siranltaneouB — tlie work of the Bame 
It may be difficult, he saya, to explain how 
la hippena on this hypothesis, but not more bo than 
nany other. On the other hand, the permanent in- 
f ^Nise of the capacity of all solids when melted, and of 
I ID floids (as he affirms) when vaporised, — sufficiently 
I niking^ facts, — aie not explained by Black's theory ; 
1 the opposite hypothesis (he conceives), the 
I ikmomena are readily accounted for. It may be sup- 
I paed either that the increased capacity and the fluidity 
"stent consequences of some conmian cause, 
« diat the union of the latent caloric and the soUd is 
IccwDpanied, at the moment of its taking place, with a 
WW capacity for heat, in proportion to which the latent 
(ilaric is great or small- 
It now only remains to explain a few of the chief 
fbenomena according to each of these theories, in order 
Alt ijtdr merits may the more readily be contrasted : 
f^ it ia in the language of one or the other that 
til facts relative to heat are expressed by chemists. 
'" explaining these phenomena, we need only attend to 
the: cases in which the change from solidity to liquidity 
or the gaseous stale causes absorption and disappearance 
'>r lieat ; those in which it is rendered sensible being 
"Illy their converse. 

In Euch instances, the followers of Black would say 
that the absorbed heat becomes latent, has chemically 
comUned with the solid or Uquid, and is the cause of 
the liquidity or of the gaseous state. Dr. Irvine would 
nppDse that during the change of state there is a change 
of capacity, the new state requiring more caloric to main- 
Iain it at the original temperature ; hence, an absorption 
of heat must take place to supply (he increased capacity, 
and this absorption Is an t^ec't of liquefaction and va- 
porisation, and not Clie cause. It is not only in case t>f 
" I one distinct stale to another, that a ctan^ 



BOiae of t 

change of densitj h^pen 



E of each sUte: thu*,* 
J if a piece of ii 



lently struck, its tpeclSo gravity is increased; 
become brittle, and very hot. If it be again « 
little more heat and conden&atian may be produce 
After this, DO effect results from striking it, e ~ 
regard to condeiiEaiian or heat, until its original i 
and condition be restored by healing the f 
the fire: this process also restoreB its mallealdlitTV ^ 
^ame happens with several other metals, but n 
to the extent described. When the density of a 
is increased by dissolving some other subet 
Wid, universally, when any two liquids ooi 
mically; there is an extrication of heal, somi 
•iderable. The mixture of oil of vitriol and « 
S good example of this heat ; and if tbe specific | 
of a gns or Tapour be increased, ihraewill be ai 
of its temperature. This is so great in conde 
jn the barrel of a very small syringe, close at 
that, as already mentioned, a bit of agaric cor 
jt is thus set on fire. The converse of all the 
■itions is, no doubt, e<]ually true ; but it is only in the esK ' 
of gases or vapours that it is very distinctly observsble> 
If the density of a gaa or vapour be lessened, cold ii 
produced, as appears from the sinking of a thermometN 
in the receiver of an air-pump when the air is raxified; 
because heat is absorbed from all the surrounding raedib 
All these cases of change of density, in which heat ii 
rendered sensible, would be explained, by the follower! 
of Bladi, by declaring that some of the heat necessBJ 
to the existence of the body as a solid, liquid, or gas, was 
forced oat of it by the approsimation of its particles; and 
AS the panicles of solids and Uquids are preserved tn equi- 
liitrio, by tbe balance of cohesive attraction and calorific 
tepulsion, any cause that disturbs this balance most 
change the relation of the body witli respect to heat. Jt 
does not seem to mc that Dr. Black followeil up this part 
pf fbe sulfject with, sufficient allenlion. Kccmiiia^ Xn'iia 




vi sxit tmivsmen a tux. ji 



•if 



•• . 



tiusr >dixur% IT ^— r#* 



k iu n^nsKLUUE lii]iisacruL«i kii -at jTiaer.. r: ^ vnur 
cnied br 'iii" " — if sbmctt .r»vcu' •^.cr.'t^^r: ~'<tfr, 
Bnee, in bl -ssc^ xthcl uusazu^ tut irra^ r iii^ .- Tr:.-n 
Insdicie^ lOCL I'^jacruae: bxjl 2»rrr«m -nAir.^i -:;^ tie 
ipedfic bcK -of -rmnnr if ▼.iskt a i«u ' - '-7' T*:.lff tx^ 
of vjiter faej: s I "yj'- Tha T.ifa:t irr-— nac s«» 
cipadiT ftf 'CBinir j> ««»-. jusrmi u zr^xt^ II.^ lur nf 
wuer: ms/L^ 4a. -^'aamraacim ^^nnn^ tr?i«^.i in iit^ sue 
iKigDCfi iy Irr-nis. ^ir -m-w. inili .«*- r:/i*-r-- jijcriiii-^sics 

fpedfif itfflc u: -vvomir » i.^r itr .-.-^.m lut -rrm. t.» 
have HK Bsea: -ssicaR: *niiiiii<^.:.->; .n .: <? 11 utkt ±-nrm x 
t coDcaBQUL 'Uf AiUL joiiRr-Bni^:*^ ' 2j:r. irr tie aiov^p^. 
BOD ftf Irvtseft tiear^ tift-- ?»f-?n 11 -^-- m aa a:2«»- 

the iSEiWC jocjOiiR dir ^rrr ■••'»!. It ji itjs-^ar-^ 

die cprnjaaszan ic tbf -rri ^i^ fnt^ -^ ic Tms* 11 i ^- 
Kmrmir jf ae meridt' -Mar ji ^le "imT-M^ aimid^i* 



I 



I 



mil b> admit, with Black, the esiateiiM of la 
in bodies. 

Modem discovery has accumulated a Dtmiber oFS 
which ilo not seem to be explicable by the theory if 
Irvitie, In the chapter on combustion, several soiidsnul 
liqttiitii will be mentioned, which, when heated gently, K 
even touched, explode with violence and produce gasMOi 
products. Here, then, are numerous instances of ibe 
conversion of Bolids and Uquids into gases, accompanid 
by the copious evolution of heat. — What is its sourw? 
If, in the production of the gas, there be an increase tt 
capacity for heat, whence comes the free caloric thil 
appears ? Why should we not rather expect cold M 
result, when gtinpowder is transformed into a vast volunie 
of gas ? For the answer to these questions, we must 
apply to the doctrine of latent heat. MM. Dulong and 
Petit give the following as a consequence deducible fTOO 
their researches, the details of which, however, they have 
not Btated : — " The quantity of beat developed at the 
instant of the combination of bodies, has no relation V 
the capacity of the elernentt : in the greater number of 
cases, this lose of heat is not followed by any diminution 
in the capacity of the compounds formed." 

We have now to direct our attention to the heating 
■nd cooling of bodies, and tlie processes by which dlese 
changes are effected. If a hot mass of metal be laid on 
one ^at is cold, the former loses heat, and what it loses 
the other acquires ; both are now hot ; and it is to be 
enquired. Why did this partition occur ? Ithssbeenal' 
ready observed, that, according to the corpuscular hyptH 
thesis of caloric, its particles are Eelf-rcpellent ; and tiio 
more so, the nearer they are to each other. The con-' 
sequence of which must be, that when the particles havs 
liberty of motion, they will constantly endeavour to dif- 
fuse themselves. If a great nunber he accumulated in 
one place, they will immediately, if not restrained, bc^ 
to separate in all directions, until the accumulation is 
removed : they are then at rest, and in a state called 
Aeeguililtrium of caloric; whicbKieid^ toemw, Ajbj.^ 



IHiP. y. HEAT. 81 

iiimmnding ofcrjects contain as much caloric as attaches 
itidf to them^ so as to saturate their capacity^ and 
iqaalise their temperatures. This diffusion of caloric 
in bodies does not depend exclusively on a repulsive 
igmcy^ but is assisted^ in all probability^ by an attrac- 
tive force ; for if caloric be matter^ its particles should 
tttract and be attracted by other matter with different 
degrees of energy : but on this part of the sulgect more 
will be said hereafter. 

The facility with which heat enters or leaves bodies 
depends much on the nature of the body ; some species 
permitting the passage of caloric through them with ease^ 
nd others with much difficulty. This property is called 
the capability of bodies to conduct heat. Instances of its 
existence occur constantly in our common experience ; 
thos^ when there is occasion to hold any hot metallic 
instrument^ we take care that the part by which it is to 
be held shall not be made of metal^ but of wood ; for 
the metal would allow the caloric to pass in so condensed 
ft state^ and with such rapidity^ into the hand^ as to 
prove painful; whereas wood^ and such other sub. 
stances^ will not permit it to pass otherwise than slowly. 
Hence the sensation produced by one portion of caloric 
on the hand has ceased before that of another com- 
nienees^ and there can be no accumulation. Metal is^ 
therefore^ called a good conductor of heat^ and wood a 
had one ; and bodies have very different powers in this 
lespect. Thus, water, heated to 150°, is capable of 
Bcalding : but air, heated to 260° *, can be endured with, 
oat any painful sensation ; because water can much more 
perfecUy be brought in contact with the body, than so 
ntre a substance as air. The conducting power of air 
saturated with moisture is to that of air commonly dry 
tt 230 to 80f ; hence the former feels so much colder 
to the human body, t 

In consequence of this property which bodies possess, 
of conducting heat with more or less facility, certain 
deceptive results follow^ which it will \)e iiecea*«r^ 

• Bbgdeo^ Pbilosopb. Trans. 1775. f Rumford, toid. Ym6. 

Q 



I 



I 



to explain. If a piece of cork, and an equal bnllt of 
metal, be kept for a length of lime in boiling water, 
then withdrawn and hastily dried, the metal will feel 
intolerably hot to the hand, while the cork feels little j 
more than warm. Here it might be supposed thai the 
two bodies, although both exposed to the heat of boiling 
water, had been heated to different temperatures, whcreai 
a- thermometer applied to each will stand at (he aiM I 
height^ proving that the different effect on the oi^aM - 
of sensation are owing Co the rapid trantmission of o- 
loric to the hand in one instance, and to its slow coni' ' 
niunication in the other. It is a fact attributable to ibe 
same cause, that if a piece of meial and a piece of cork, 
both at the common temperature of the air, be applied to 
one's skin, the metal will fee! cold, and the cork con- 
parativel; warm, because heat ia withdrawn from ibe 
skin more rapidly by the former than by the latter. 

Such bodies as are of greatest specific gravity art, 
generally speaking, the best conductors of heat ; but lie 
observation is not univeisally true. If a body, which li 
of great specific gravity, and is a good conductor of bell, 
have its specific gravity lessened, so will also be its con- 
ducting power. Thus, raeials are all good conductoTBOf 
heat; yet their filings, which are epecifically lighter, in 
consequence of the spaces between their particles, an 
Tery inferior in conducting power ; and whatever con- 
ducting power wood may have, it is much lessened by 
being conveMed into sawdust. 

Good conductors of heat would evidently form bad 
clothing. The object of clothing is to intercept the heat, 
and preserve the body as much as possible at a unifom 
temperature. In cold weather, ttie temperature of the 
atmosphere being lower than that of the body, clothing 
formed of non-conductors prevents the too rapid escape 
of heat from the body to the surrounding air ; and, in 
very hot weather, it answers a contrary purpose, — pre- 
venting the too rapid communication of heat to the body. 
Animals are ciotlied In fur, woo\, teativew, &c. — all umi* 
conductors ; and man borrows \ua dotoft^ itn-^cwx 
tiegree, from iheia. 



IHL,. ^.^.. I IP 

M All that has been said on the subject of the con- 
•M liMting power of bodies refers to such as are in the 
J Mlid stale; for those that are fluid are all very bad 
(oniluctors of heat. Tliis has been experimentally 
|)toveil by applying faeat (tbatj for instance, arising from 
s stratum of burning ether) to the surface uf (lie liquid 
iling a tall cylindrical vessel ; and having the bulb of 
1 ibermometer placed some distance t>elow the source 
of beaL The rise of the thermometer is extremely 
ibw. It had been even doubled that this smaU rise 
of temperature was attributable to the heat con- 
dscted by the fluid ; it was supposed that (he heat 
llid been conveyed down by the matter composiDg 
ii it tides of the cylinder, until the question was set at 
rat by an experitnent of the late Dr. Murray, of Edin- 
turgh. He constructed a cylindrical vessel of ice ; filled 
it with oil at 33" ; fixed a thermometet at some distance 
■ I below the surface ; and applied heat to the surface. The 
ihermometer rose 5^° in 7 minutes, clearly showing 
iliat, although slowly, the oil did conduct the heat, in- 
asDiuch as ice can neither conduct nor receive heat 
liigher than 32° ; — any aildilional heat melts it, and 
becomes latent. Lifjuida, like soliils, seem to conduct 
better in proportion as they are more dense : — thus, 
epirit of wine, a. very light fluid, is a bad conductor ; 
oil ia heavier, and conducts better ; proof spirit is 
heavier, and is a better conductor ; water is still heavier, 
and is a still better conductor ; and qutcksiiver, the 
heaviest of all liquids, is, comparatively, an excellent 
conductor of heat. 

As liquids are bad conductors, it may be asked how 
it happens that they become so speedily hot, and so soon 
boil when they are exposed to the action of lire. In 
Older to understand this, we must revert to a fact al- 
ready explained, that when a liquid is heated, it becomes 
3|iecifically lighter. When a vessel containing water is 
laid on the fire, the layer of water at the bottom, and 
neKt the fire. Brat becomes hot; it also becomes speci- 
ecaUy lighter, and consequently rises throuE;^ the wa.Vii 



I 



I 



KLBMSNTS OF OHiUBTRT. 

in the BHine manner as a cork or any other liplit boij 
would rise. This portion of heated water having be« 
thus removed by its lightness, the next layer, now in 
contact with the bottom, or source of faeal, becmm 
heated in its turn, and ascends ; and so on, layer after 
layer is heated, and ascenda until the water boils. 

These ascending currents, along with the imperfwt 
conducting power of liquids, assign the reason that thej 
receive downward transmissions of heat so slowly. Al 
awn as a layer of water at some depth from the surf»M ' 
receives a portion of caloric, instead of transmitting it 10 
the layer next beneath, it ascends to the lop. 

Aldiough it is the kind of matter (hat regulatea (be 
difficulty or facility with which caloric passes throng 
it, yet, with regard to receiving caloric in the first in- 
■Cance, or parting with it afterwards, the conducliDg 
power is by no means the only one concerned ; these 
effects depend in a great measure on the surface wluck 
receives or transmits. Thus, if two similar pieces of the 
same metal, polished alike, be heated equally, and set to 
cool at the same moment, in the same medium, they «ill 
be reduced to the ordinary temperature of the air in the 
leme space of time. But if one of the metals have ita 
polish impaired by scratching with sand-paper, and if 
they be now equally heated, and set to cool as before, 
the scratched piece of metal will part with its heat much 
sooner than the polished one; and however difficult it 
may be to conceive how the polish can act in retaining 
the beat, it is certain that the fact is ijo. 

When a body, such as the piece of metal just now 
instanced, is heated, and left in the open air to cool 
Biionlaneouely, the heat gradually flies off from it on all 
■ides, in the form of radii, or rays ; and from this cir- 
cumstance the departure of heat from the body is called 
the radiation of caloric. 

Some bodies have a greater power of radiating beat 

than others : the consequence of which is, that those 

bodies a'hich have the greatest vadiatiiYs^ ^ovjet will cool 

ill die shortest lime; atul by tliU ta^lAU^ o5 iLQQ\\w%,'Cae 



iniiadng power may be estimated, and rendered manifeit 
by experiment. 

Let two cylindrical vesiels of tin-plate be prepared, 
limilar to the one represent^ in the margin, capable of 
holding about half a pint each. Each must have ii cork 
fitted to its mouth, through which a thermo- 
meter tube passes, the bulb standing about 
the middle of the vessel. Let one of these 
cyhnders be painted over with lamp-black 
mixed with water and a Uttle size. If both 
I vessels be filled with boiling water exactly at 
same time, the corks and thermometer* 
ig immediately introduced, it will be 
I found that the thermometer of the blackened 
I vessel sinks very rapidly, while that of the 
I bright one fails very slowly. The experiment 
proves that the surface of lamp-black radiated 
heat more rapidly than that of bright metal. Indeed, 
die experiment may be made with the thermometers 
only, one having its bulb blackened with lamp-black, 
and the other being clean. If both be raised to the same 
temperature before a fire, and then allowed to cool, tlie 
mercury in the blackened one will sink at a much 
quicker rate. 

The coaling used in both experiments was lamp- 
black, for this substance is found to be the beet radiator. 
If its radiating power be esbimaled at 100, then that 
of ^aas would be found to be t)0, bright lead 19, and 
tin-plal« only 12 ; and although bright lead radiate* 
with a power of but 1 9, if the lead be a little tarnished, 
its power is raised so high as -I'S. 

In general, it may be afSnmed that all substances in 
nature have different radiating powerG. In the case of 
metals, the radiation depends on the mere surface, with- 
out reference to the substratum : but in the case of 
other radiating substances, the thickness of the coating 
constituting the surface, within moderate limits, increases 
the TiHiation. The radiation of heat taVes ^Uce mme 



I 



\ 

I 



rapidly in a Tscunra than in the air. It takes place in 

ill gases. 

Whatever the canse may be that enables these aur- 
faces t« radiate caloric with such facility, and Iransnut 
it in* right lines, it is but natural to suppose that ■ 
surface of the same kind would also permit the entrance 
of caloric. Accordingly, ne find that the fact is so; and 
that the surfaces of bodies which radiate caloric wilh 
facility, also absorb it with facility; and, conversely, thai 
surfaces which do not radiate caloric with much energy, 
are also those which will not readily absorb it when radi- 
ated from other bodies. For instance, polished metals, 
which radiate caloric imperfectly, receive it imperfecdj 
when radiated from other bodies ; but when their sur- 
face has its radiating power increased by being scratched 
by sand-paper, or tarnished, it then absorbs better. And 
lamp-black, which is the best of all radiators, is also 
the best of all absorbers. The following apparatus ex- 
emplifies this position: — A tin-plate cylinder. A, ii 




placed horizontally, and opposite its ends are placed tin- 
plate discs, one of which is to be bright at both tnir- 
faces, and the other is to be painted with lamp-black and 
aiKcd water on the surface next the cylinder. Let du- 
plicate discs of tin-plate be provided : let one of these 
be stuck to the disc B by means of a thin stratum of lard 
interposed ; and the other Himilail^ cemented to the disc 
Cj which ha» the blackened surface, V\\a,l wntasft^^rini 



U to the cylinder. Each pair of discs bhould be 2 
bea distant from the opposite end of the cylinder. Let 
(becylinder befiUed with boiling water through the mouth 
O, snd corked. The heat now radiates from both ends of 
<he cyUnder ; each contiguous disc absorbs the radiated 
''eat: but the blackened disc will soon evince that it haa 
ibsorbed with more avidity, for it will become bo warm 
ibsi the lard will melt, and the disc which iiad been in 
raatact with it will fail off; while the pair of discs at 
the other end will remain a long time unaffected, and 
perhaps may not separate. If both ends of the cylinder 
are blackened, the result will be more decisive, because 
more heat will be radiaierf from the cylinder. 

A question here occurs ; — Does this fact depend on 
any known property of the metal ? and are there any 
considerations which might have led us to an antici- 
pation of the result.' It might naturally be supposed, 
that a surface found to radiate heat with such facility, 
and to receive it so readily when radiated from other 
bodies, should easily allow a passage through the ma- 
terial of which it is composed ; and that, on this ac- 
coimt, the best conductors of heat would also be the 
best radiators. But so far is this inference from being 
correct, that there is reason to believe the reverse to he 
true ; for metals, which are the best conductors of 
calorie, are its worst radiators, that is, while they are 
bright and untarnished: and, in a great many cases, 
the best radiators, as lamp-black, Unen, paper, &c., are 
very bad conductors of caloric. It being the fact, that 
good conductors are bad radiators, i( should also he true, 
and it is the case, that good conductors present had 
receiving surfaces ; and this precisely corresponds with 
the experiment last described, in which the bright metal 
ilid not receive the radiated heat from die vessel of 
boiling water. 

As the polished metal was proved to he a bad receiver 
of radiated beat, and, in fact, refused to absorb the ca~ 
loric which must have radiated towards it ftom. 'One 
cjlinder of boiling water, it may be asked, wha.^ ^leCKa« 



I 



of that caloric which was refused admitlance by the po- 
lished tin : it did not p»sa through the tin, and, there- 
fore, it must have paEsed off in some other directiM 
without catering. 

It is easy to prove that caloric, under such circnm- 
itanceg, is reflected; and it is possible to prevent it« dii- 
peraian, by collecting anil concentrating it into one point 
All that need be done to render its effects manifest, is, 
to convert the plane reflecting surface into one of a con- 
cave form ; for, in this particular, caloric resembles, ind 
ia regulated by the same laws as light. If, therefore, i 
quantity of radiant caloric be allowed to impinge upon 
k concave metallic mirror, the rays will be reflected from 
the surface to a focus in which all the caloric will be 
concentrated. 

To perform this experiment with advantage, an ar- 
rangement different from that just described roust be 
made. It must be so contrived that the body, which is 
the source of heat, shall be at a much greater distance, 
and that the direct rays emanating from it shall exert little 
or no heating agency until they are concentrated by the 
Teflector. To produce the effect in a striking manner, 
the heat made use of should be much greater than that 
of boiling water ; burning fuel will afford the neceaaary 
temperature. One concave elliptical metallic specnhua, 
with the heated body and the object to be heated in the 
conjugate foci, would answer the purpose, except diat 
the proximity of the heated body might cause the effects 
of radiation and reflexion to be confounded. In ordet 
to transmit the heat lo so great a distance as ia necessary 
for distinctness, and to concentrate it afterwards, two 
parabolic reflectors must be made use of. The first re* 
c^ves caloric from the heated body, and reflects it to 
the second, which then collects and concentrates it in 
such a manner as even to set fire to a combustible placed 
in its focus. The mirrors may be formed of tin-plate, 
and the seams caused by the joining of the plates may 
be so nicely e.vecuied as not to pioie very detriment^: 
mbottC 3 feel diameter will suffice. One \a \o \» «n. 



^ 



eRAP. T. 



4 
BEAT. 



89 



pended from the ceiling of a room 12 feet in height It 
is to have an iron-wire cage filled with burning char- 
eoal placed in its focus. The other mirror may rest on 
the floor of the apartment. In the figure^ the mirrors 
tt« represented as being dose together^ to save space. If 





s little gunpowder laid on a bit of black paper be held 
in the focus of the lower mirror, it will explode, although, 
if held two or three feet higher up, that is, nearer the 
source of heat, it will not be affected. In this experi- 
ment^ the heat radiates from the charcoal, and is reflected 
twice before it arrives at the gunpowder. 

Since the two metallic surfaces reflect the heat from 
them, it is natural to suppose that they do not get hot, 
and, accordingly, we find that such is the case. But, be- 
sides this cause, there is another (or it may be the same), 
which prevents the heating of the reflectors: they are 
made of bright metal; and this, as we have already seen, 
is a bad radiator of heat, and therefore a bad receiver or 
absorber. Metals are the best reflectors of calonc, «.xv^ 
the wont radiators J and, generally, it is fo\ind x\va.\. ^e 



I 



90 ELEKENT3 OP OHBHIBTRT. PAKI h 

reflecting power of bodies is Btrorg in proportion K the 
rwliating energy is weak. 

The radiating power of glass is considerable, and, con- 
sequently, its reflecting power ought to be proportionately 
weak: this also is found lo hold; and as it is a good 
radiator, so it must be a good absorber. In the experi- 
ment juGt described, had the reflectors been of glass, 
which thus powerfully absorbs, although it reflects badij, 
the heat would have been detained by the glass instead 
of being reflected on the gunpowder. That a glass mir- 
ror scarcely reflects heat, any one may convince himself 
by means of a common looking-glass placed properly be> 
fore a hot fire. On the other hand, a metallic mirror, 
as has been already observed, reflects all the heat, andj 
consequently, does not become warm ; " but if covered 
with black over a burning candle, you cannot keep it 
four minutes in the same situation (before a fire) with- 
out burning your fingers." * 

With regard to the reflection of heat, therefore, it ii 
plain 'that it ia not sufficient for the reflecting surface to • 
he hard and well polished, liut it must be of such a ma- 
terial as is a bad radiator and absorber. In the case of " 
the glass mirror just now alluded to, the glass preaeDla 
a much more even and smooth surface than the tin, and ' 
it has even a briUiant metaUic coaling on the back of iti 
but the glass being a good radiator, it must make a bul | 
reflector. The silvering at the back has no effect : it . 
may be removed, and the back surface roughctl by grindf ~ 
ing, without any change in the reflecting power of the J 
other surface. 1 




i 

rmo investigated the principal phenomena of heat, 
IT H is necesKry to the eubject of the present trea- 
tte shall now explain a few of the leadin|; qualities 
of anodier physical agent closely connected with it. 

Ifheat be gradualiy communicated to a body, — a inaH 
of iron, for example, — no other eifects can be observed for 
■ CMstderable time, except an enlai^ement of dimensions 
ind an elevation of temperature. At lengdi, liowever, 
arery remarkable change will be observed. If the pro- 
cess be conducted in a dark room, the metal, previously 
inrimble, wilt become viaible, and will not only be seen 
itself, but will enable surrounding objects to be seen. 
Id fact it will emit light. The body is thus said to be 
state of ignition, or, in common language, it is red- 

iwi. 

The original sources of light are, iirst, the celestial 
bodies, the sun and fixed stars; and, secondly, terres- 
trial bodies, in which heat is produced in so intense a 
d^ree as to be accompanied by light, ae just explained. 
Light, being primarily produced in this manner, is dis- 
tributed, in a variety of ways, through the space which 
rarrounds us, end is the immediate means by which all 
objects become visible. It passes freely through the at- 
iDDspheie ; it strikes upon the clouds, and is reflected from 
3, Tendering them visible. It strikes upon all ter- 
rcMtial objects, and is by them modified in a curious and 
complicated manner ; so that, when reflected by them, it 
produces all the phenomena of colours. Its course, when 
uiobalructed iu passing through any space or medium of 
a uniform character, such as glass, water, air, or a va- 
'/ttum, is in straight lines ; but when it passes throug^i 
■jiarra occupied by substanixs of different kinds, or m 
^^i-rem states, — as' from glass to water, or from vi 



HUeUENTH or OBBHISTftT. 






e of density t< 



I 



I 



ferent state, — it is liable to be bent into a crooked or evei 
a curved path, subject to fiseil and well known, thongli 
very coio plicated, mathemalital laws. It is not neces. 
Bary, even were it possible, here to enter into any ex- 
planation or development of these phenomena, 'thorn 
who desire to obtain an acquaintance with them, will 
find them explained in works written expressly on 
Optics, and are referrexi to the Treatise on that subject 
in this Cyclopwdia. 

Light and heat so frequently accompany one another, 
that it has been sometimes disputed whether they are not 
exhibitions of the same principle. The fact, however, 
that heat of the greatest intensity can exist unaccom- 
panied by light, is unquestionable ; and this alone wonld 
pert^ps be sufficient to establish their diversity. But it 
IB contended, that light cannot exist without heat, and 
that, therefore, heat must be regarded as a quality of 
light. Against this it may be stated, that the sun's 
light reflected by the moon, although collected and con- 
densed into a point by the most powerful optical means, 
has never been found to affect the most delicate thermo- 
meter. Also, that when heat and light are produced by 
the combustion of common fuel, the heat will be inter- 
cepted by a plate of glass, while the light will be fredy 
transmitted. But, perhaps, the most decisive proof that 
the heat in the solar rays is a principle distinct fam 
their light, is found in the fact, that by optical menu 
the solar beam may be deciimposed into its constituent 
elements ; and that some of these elements are inviaible 
non-luminous rays, which affect the thermometer more 
powerfully, and are, therefore, more calorific, than Bnj 
luminous rays.* 

The chemical influence of light is conspicuoua in a 
variety of natural and artificial processes. In vegetation, 
light is an indispensable agent : it is by its assistance 
that growing plants are enabled to decompose carbonic 

* oenct, CMb, C)t. p. 69. 



CHIP. TI. LIOBT. 9^ 

add^ assimilating its basis for the purposes of nutrition. 
Wi&out its influence^ vegetables are deficient of their 
due elementary constitution : they are weakly^ inodorous, 
and of an unwholesome colour. Dr. Black proved, 
thst the green colouring matter of vegetables, which 
he found to be a highly inflammable substance, is not 
daborated in plants if they grow in the dark : ihty are 
bUnched. The influence of light in discharging v^e- 
taUe colours is manifest in the process of the bleacher : 
and the rapid fading of coloured paper-hangings, silks, 
and cottons^ when exposed to strong sun-light, is well 
known. Its energy as a chemical agent is still more 
decisively seen in the influence which it exerts in pro- 
moting combination and decomposition ; and the latter 
effect has been made use of as a measure of its power. 

A beam of solar light, admitted through a horizontal 
thin slit in a window, and allowed to pass through a 
wedge of glass called a prism, the edge of the wedge - 
being placed parallel to the slit, is found to be separated 
or decomposed by the action of the glass, so as to form^ 
when received on the screen beyond the prism, not a 
horizontal line of light, as would otherwise be the case, 
but an extensive luminous band, equal in breadth to the 
slit in the window, and extending from top to bottom a 
considerable length. Different parts of this band of light 
exhibit different colours; the upper end being violet, and 
the whole being divided into horizontal streaks of colour, 
descending through the tints of violet, indigo, blue, 
green, yellow, orange, and, lastly, red, which occupies 
the lowest extremity of the luminous band. Now, it is 
found that the light occupying certain parts of this spec- 
trum, as it is called, is capable of exerting chemical 
agencies, and of promoting, in various degrees, the pro- 
cesses of combination and decomposition. Wollaston, 
Ritter, and Beckmann, by a careful examination of every 
part of the spectrum, discovered that beyond the least 
brilliant extremity, namely, a little beyond the violet 
ray, the ma'ximum power resides, which deteimiv^ 
chemical combinatioD, The experiment had \)eei\ \oxv^ 



before made by Scbvelc ; but he came to the conchtuoii, 
that the greatest chemical effects are proUuceil in ike 
violet ray itself.* This chemical ray was first tiamed 
the (leoxidisitig ray, from a mistaken hypothesis of ihe 
nature of the chemical compound on which its agency is 
moGt manifestly exerted. 

It has long been supposed that the Tays in or near Ae 
violet extremity of the spectrum are attended whh t 
certain magnetising influence. The experiments, how- 
erer, which have been made to decide this qaestion, hm 

t extremely contradictory in the lesulu, &U m 
conclusion can be deduced from ihem.t 

One who contemplates surrounding objecta wotild, in 
■n probability, be first struck witii the singular sitDK 
of the air which encompasses him. Common expericBOt 
shows that the atmosphere is not a void; that it is matter 
which is capable of affording considerable resistance U 
mechanical force. The impulse on the sails of a wind' 
mill or of a ship, the blowing of a bellows, or the flying 
of a kite, are proofs of the materiality of air too palpable 
to require insisting on. '^ The materiality of air ll 
further proved by its capability of producing and pro- 



CIIAP. VII. 



CONSTITUTION ( 



Section I. 



pigating sound. In the detonation of gunpowder, that 
sabsunce is converted into a quantity of gas of immense 
diBticity, which, being at that instant conflneil within 
the compasB previously occupied by the powder, buTEt* 
ant njth prodigious force, and striken the exlemal air 
»ilh violence. But, because fire ia concerned, more 
miy appear to act than mere air. A simple experiroeut 
niil set this objection at rest. Let a bladder, full of 
ilr, be forcibly compressed until it burst : it is best done 
bj a powerfu) stroke : (he air rushes out with violence, 
ind, striking against the external air, an explosion will 
be produced as loud as a pistol-shot. This fact alone 
Hoald prove the materiality of air ; for the bladder, if 
■truck with a force not quite Guflicient to break it, 
returns very little sound ; it must, therefore, be the air 
rushing out which strikes the surrounding air with such 
force. Were the surrounding air removed, there would 
be DO sound : a bell, struck in the vacuum of an air- 
pump, cannot be heard. 

It may be observed, that the bladder will hear con- 
siderable compression without bursting : its sides may 
be forced Utgetlier ; and, in short, the contained air nay 
be pressed into a much smaller compass. It is, thereforej 
an unavoidable inference, that the particles of which air 
is composed are brought nearer together. But, since the 
bladder expands as soon as the compressing Force is re- 
moved, it is manifest that the particles of air resume 
their former distance when at liberty so lo do. Thus, 
a given quantity of air may be made to occupy more or 
less apace, that is, may be expanded or contracted ; and, 
when contracted, it will recover its dimensions with a 
force like a spring. This ijpring, or elasticity, of the 
air ia produced by the repulsive force of caloric, which 
lends to separate the particles, until counteracted by some 
opposing force. 

The elasticity of the air is a force of considerable 
energy. When a quantity of it is compressed, or, at it 
is calledj condensed, into a very small compas9,its eSsA 



I 
I 




OHEmSTBT. 



I 
I 




I 



proper bulk is prodigious ; tmd wM 

Uut It wiii Gometimea burnt the Etroiigest \i 
the well known danger of forcing loo much ai 
ball of an air-gun ; it bursts, and i 
misctiief. 

All these considerations proving that a 
becomes a. question. Does it resemble other maUerU 
common property, gravitation ? or, in other w 
weight ? This is a quealion which can bi 
directly in two ways. If the air possesB weight, iMli 
traction from a vessel ought to lessen the weight of tbtf 
vessel, and its addition should increase it. Accordinglj, 
tn empty glass globe is found to be lighte: 
lame globe filled with air.* 

Thus air, like other matter, possesses weight ; and the 
fact leads to some important consideratioiiB. For, U 
the atmosphere extends to a considerable height, it mtut 
be supposed that such a weight of heavy air, pressing « 
that portion of the atmosphere near the surface of llu 
earth, would exert a considerable pressure on all bodiM 
situated at the earth's surface. 

Air and gases generally partake of the fundauMBtri 
property of liquids, by which they transfer presran 
eqiully in all directions; and, as a consequence of ibil 
property, the pressure arising from their own weight ton 
in every direction, and, as its particles possess per&d 
freedom of motion at any point, the pressure depend! n 
the weight of the column of fluid above that point.t M 
the surface of the earth, the air sustains the whole wei^ 
of the superincumbent atmosphere: here, therefor^ the 
■ir beilig most pressed upon, its particles are forced 
nearer to each other, until their self-repulsion prevmll 
any nearer approach ; and hence the density of the tir 
is greatest at the earth's suirface; that is, a closed vesad, 
full of air, taken at the surface, would weigh more than 
the same vessel filled, at a greater height in the atmi^ 



Km. tarn Amoemxax. '97 

lere. The greater the height at which any given portion 
lir is taken, the less deiise it is, because it is leea com- 
ssed. The condition of being less dense ia otherwise 
■ressed by the words more rare ; because the number 
larticles in a given volume is less, and, therefore, such 
olunie would weigh less. At length, towards the 
beat parts of the Blmoaphere, where the pressure is 
msiderable, the rarity is great; the repulsion of the 
!icles being here an overmatch for their weight. 
withstanding the enormous weight of ttie atmosphere 
be sorfaee of the earth, the destructive consequences 
t are obviated hy the equality of the pressure on aJl 
s; for, to be preB!!ed equally on all sides, obviates 
)y of the effects of pressure as completely as not to be 
sed at aU. 

kir is a fluid of an unalterable constitution ; there is 
ion to believe that, Imt for certain processes to which 
i constantly subjected, it would never suffer any 
nge. On account of these processes, however, it is 
le to great and important alterations ; and these 
rations are of hourly occurrence. 'We know, for 
ance, that air is injared by a number of per- 
i breathing in it : it is thus that, in very crowded 
mblies, the air becomes absolutely pernicious ; and 
e is a dreadful instance on record, of a number of 
jrtunate persons whose lives were sacrificed by their 
g obliged to respire the same air for a length of 
:. In such air a candle will not bum. An equal 
ry, and of a similar kind, is done to air by a 
huroing in it, when there is not proper ventilation : 
air thus injured, if attempted to be breathed, will 
as an immediate poison, and destroy life. It is 
th while to enquire into the cause of this singular 
ige. 

n order to try the effect of fire, an experiment is 
ly made by burning a taper in a quantity of air 
ided in a glass jar, or bell, inverted o 
IB to prevent cowinvmcadoa with the atrnospWre. 
m be foaad tbaltlie best of the flame first ex-pani*. 





le time the quontiqi 
perceptibly diminish, u^j 
appear by the r 
Ok bell when it coohi it 
the taper will be exttDguish 
From tluH experiment tw 
are obvious; first, the air w 
mained in the bell after tl 
had burned some time n 
longer permit it to burn ; 
coodly, at the end of the 



t (her 






th&n before; or, in other wor 
of the original air was withdrawn. The questiot 
What has become of this air? Aii ordinary 
■would answer. It is consumed, it is burned: \ 
explanations have no meaning ; the air cannot h 
annihilated ; it must still exist somewhere. Tb 
we shall be presentiy able to assign. 

There are many other processes beside the bi 
a candle that would have diminished the quantil 
in the bi;ll-glass. A liquid, prepared by boili 
water on a Uttle lime and sulphur, has the pre 
absorbing a considerable portion of air which ] 
exposed to its action. The experiment is eas; 
by agitating some of the liquid in a bottie, we 
with a cork, and removing the cork under wate 
will rush in equal in bulk to the air absorbed, 
then ascertain whether or not the air which re 
incapable of supporting flame, as it was in the 
ment just now made with the candle. It will ' 
that it is not. 

The metal called quicksilver, or, as it ia o 
called, mercury, has also the property of absi 
certain quantity of air ; but, for this purpose, 
be kept boiling in a flask filled with air for 
length of time : the portion which remain 
sorbed a( t^e end of the process will extinguish 
in the former instances. Bw t\ie mctcai'j 4\ 



^HAP. vn. THB ATMOSPHERE. 99 

Operation has been very materially changed : it no longer 
poBsesses its fluidity^ nor its metallic splendour ; it is 
oofiverted into a red scaly substance ; and it is found to 
ItthetTier. Here^ then^ are two remarkable facts : when 
mercury is heated in a vessel of atmospheric air^ a great 
<ivuuitity of the air disappears from the vessel^ and the 
iBercory increases in weight. The natural inference is^ 
that the deficient air is contained and concealed in the 
i&ercury^ and that it may be possible to detect and re- 
<ioyer the portion thus lost. That such a recovery is 
pncticable^ appears from the following fact : — If, after 
tb£ air has been absorbed by the mercury^ the heat be 
incieased to ignition^ the red scaly matter into which 
Ae mercury was changed will restore every particle of 
*tt which it had absorbed^ and the mercury will re-appear 
in its metallic form. It will be found that the air thus 
tBcovered^ to all appearance, resembles common air, so 
^ as being elastic, transparent, colourless, and inodo- 
rous. However, it is very diflPerent from that portion of 
«ir which the mercury originally refused to absorb : that 
portion instantly extinguishes flame; whereas, if a newly 
extinguished taper, the wick still ignited, be immersed 
in a portion of the air recovered from the mercury, 
4e taper will re-kindle, and burn in it with increased 
splendour. 

From these experiments, the obvious inference is, 
that We have separated common atmospheric air into 
two other airs, diametrically opposite in at least one 
property, and both of them perfectly different from the 
OriginaL One of these airs is so far different from the 
atmosphere, that it extinguishes flame ; and the other is 
80 far different, that it re-kindles the flame, which the . 
original air could not have done. 

Since, in these experiments, the most remarkable facts 
to be observed are, that one kind of air causes bodies to 
hum with far greater splendour than they do in the 
atmosphere, and the other extinguishes flame, it should 
follow, that if the two be mixed together, an aix s\io\ii\J\. 
jiesuJtj which in its power of supporting flam^ vfo\3\A.\i^ 

H 2 



,. mL 



I 



■ mean of tliose which compose it. Accordingly, -w- 
know this tn be the case ; for ihe two aira were obtained — 
from atmospheric air, it being compoBed of them ; bih1_ 
every one knows that, in the atmosphere, a candle bum^^ 
preciaely in the moderate way which might be infen 
from the contrasted nature of the two constituent gases. 

The air in which the taper refused to burn is of » 
noxious a kind, that it would extinguiah life as well si 
flame ; this fact has been established by immersing ai 
animals in it. From its destructtveness to life, it i^^ 
called azote.* The air, which had been absorbed by '!'■=' 
mercury and recovered, and which favours combustion ^^^ 

faas the effect of sometimes communicating to combus 

tibles a sour tasle; and from this circumstance tt ia calletJ 
oxygen + gas. 

The sum, then, of all the preceding details is as fol- 
lows : — It lias been shown, that by certain proeeasea, as 
heating mercury in air, a portion of the uir is absorbed, 
and another portion is not. The unabsorbed portion I 
extinguishes flame and life; it ia called azote: ihe ab- I 
■orbed portion, when recovered, supports flame and life ' 
in an eminent d^ree, and is called oxygen. It appean | 
diat atmospheric air is composed of these two gases — ' 
oxygen and azote ; the proportion being 4^th of oxygen, 
to ^ths of anote, both estimated by volume or bulk under 
the same pressure. 

Oxygen and azote have a very decided affinity for 
each o^er ; and althougli, in the atmosphere, their else, 
ticity may oppose their combitiation, their union may be 
efiected by certain processes, and then the change of 
properties Resulting from combination is of the most 
■triking irind. Tt is only neccasary to confine a quan- 
tity of atmospheric air, or any other mixture of oxy- 
gen and azote, in a small glass tulic, one end only of 
which is open, and plunged below tlie surface of mer- 
cury, to cut off the communication of the external 
air. If tliroiigh this confined air a long continued suo 



301 

cession of electrical sparks be pasaeil, the mercury will 
gradually rise in the tube — indicating a diminution in 
t.he bulk of the confined air ; for the gaseous par- 
ticles have, by some unknown agency of the electric 
sparks, been forced into closer contact, and within the 
»«ach of their affinity for each other. 

If the air contained in the tube be examined after 
this process, it will prove to be very materially altered, 
Instead of being inert, as originally, it is now pungent 
and caustic. If brought in contact with water, it 
is in part absorbed, and the water acquires an acid 
taste, and also the remarkable property of changing 
the blue colour of vegetable infusions to a brilliant red, 
when mixed. Any substance, whether solid, liquid, or 
fiiiseoUB, which possesses this property of converting 
vegetable bines to red, and which has a sour taste — al- 
though this latter is not indispensable — is called in 
chemistry an acid; and acids form a well-defined class 
of bodies. Thus, vinegar and lemon juice are acids ; 
n> also ie the gas under consideration, produced by pasE- 
ing- electrical sparks tlirough common air, or any other 
mixture of oxygen and aznte. 

If the water which absorbed this acid gas be gently 
boiled, it will be found that the steam which flies 
off does not carry the gas along with it. It is pos- 
sible to vaporise almost all the water ; and, in propor- 
tion as it evaporates, the acid becomes stronger: at 
length it becomes exceeiUngly powerful; and so corrosive 
or caustic, that it will stain the skin yellow, and even 
destroy it and form an eschar. It is, in other respects, 
exceedingly powerful. A quantity of it, swallowed, will 
in a very short time destroy life ; and it exhales a smoke 
which is highly prejudicial if taken into the lungs. 
Thus is the mUd and wholesome atmosphere, the me- 
dium of health and life, convertible into the most de- 
structive of all poisons ; and by no other means than 
lessening the distance between its constituent pMlicW, 
so as to permit the affinity of its elementarj gases Vo 
operate, and a true, chemical compound to be ^toiuceiS.. 
H 3 



I 



3(B Bi-BBBsrs or OBmasmv. tUA I 

Thia acid is now known to exist in nitre ; it is pronued 
in large quantities from tliis source, and hence it ii 
called nitric acid. 

Oxygen and azote form no less than five combinatioM 
beside that of common air ; yet all these are perfectl; 
different in their properties. It may be here obsenwl, 
that, when bodies combine with oxygen, the sabstance 
resulting from the combination is often, but not alwajSi 
an iLciil ; and whenever it does not possess the pro- 
perties of an acid, it is called an oxide. Very ofleD, 
oxides, by being combined with an additional dose of 
oxygen, are converted into acids ; but in many eases U 
oxide will combine with a new dose of oxygen without 
becoming an acid, and will merely form a second oxide; 
and even a third and fourth oxide may be thus pro- 
duced. But when the compound acquires the projfei^ 
of reddening vegetable blues, it then is entitled to tbc 
name of add. Whenever there are these succwsiTe 
itages of oxidation, each stage is marked by the name. 
Thus, when any substance has united with its first doao 
of oxygen, the resulting substance U called a protoaiit, 
from the Greek word b/i5to! [protos'), first : when the 
second dose is taken up, the compound is called a dvttt- 
Mpide, from Ziircfsi; ^deuteros') second; the third doseii 
expressed by the name tritoxide, irom toi'to; {Mtol), 
third: but when an oxide contains as much oxygen u 
it can unite with, no matter whether it h the sectmd, 
third, or fourth, it is called peroxide, from the Latin word 
per, very much : and if tliere is only one combination, 
provided it be not an acid, it is simply called oxide. 
Other systems of nomenclature are also employed. 

The property of oxygen which, to an ordinary ob- 
server, would appear the most striking, is its power of 
supporting that process called, in common language, 
burning ; but in chemistry, combuHion. 

With such force does oxygen promote cortibustion, 
that not only ordinary inflammable substances are burned 
IwjV/i surprising energy in it, bat e^en won'W.?£\t Vsim* 
itb die most- dazzling brilliancy. M\ xhaX \r teofona 




OBIP. Tn. THE ATM06PHEBIU 103 

U, to introduce an iron wire^ to one end of which is 
attached a bit of burning candle-wick^ into a phial of 
oxygen: it takes fire^ scintillates^ combines with the 
oxygen^ and melts into white-hot globules. These have 
metalUc lustre^ and^ like the original iron^ are attract- 
able by the magnet : yet they contain all the oxygen 
which disappeared in the process : they are now an ox. 
ideof iron. 

In tfa^ constitution of the atmosphere we have ample 
>oope to admire the design and execution of a structure 
calcalated, with such wondrous precision, to fulfil its 
purposes. Were the atmosphere to consist wholly of 
oxygen ; and the different kinds of objects which com-; 
ppee^ and are found upon^ the globe^ to remain what they 
are; the world would run through its stages of decay^ 
lenovatioD^ and final destruction^ in a rapid cycle. Com« 
bustion^ once excited, would proceed with ungovernable 
violence ; the globe^ during its short existence^ would be 
iu a continual conflagration^ until its ashes would be its 
only remains : animals would live with hundred-fold 
intensity, and terminate their mortal career in a few 
bours. On the other hand, were the atmosphere wholly 
composed of azote, life could never have existed, whether 
animal or vegetable, and the objects of the Creator in 
forming this world would not be fulfilled. But the 
atmosphere is a wholesome mixture of these two for- 
midable elements, each neutralising the other's baneful 
influence. The life of animals quietly runs through its 
allotted space ; and the current of nature flows within 
prescribed limits, manageably and moderately. 



H 4 



^H this conji 
^f the two 



this conjecture cauM be brought to the test by mixiq 
the two gases, and thus ascertaining if witter can )) 
formed by their union. On malting the experiment, w 
find that the two gaseSj when mixed, remain unaltered 
their particles seem to be at such a diataiice from eacl 
other, while in their elastic state, that they are not nithil 
the limits of each other's affinity. But by lessening tfa 
distance, aa by farcing the two gases into a very aaai 
corapaes, by means of a powerful condensing ayringi 
they combine, and with the peculiarity of producing 
loud report, as well as a vivid flash ; for, under ordinar 
circumstances, whenever they combine they bum. TIu 
experiment is violent and dangerous, and the result « 
tbe combination cannot in this way be determined. B» 
inflammable air may be burned in a small stream in 
vessel filled with oxygen ; they then combine quicti] 
and the sides of the vessel arc soon covered with streaS 
of liquid, which trickle down to the bottom. This lawalC 

The result of this slow combination of (he two gsM 
is juBt what was anticipated r water has been formed 
and it may be admitted as a fact, analytically and ayH 
thetically proved, that water is composed of oxygen an 
inflammable air. It may appear surprising, that from 
large volume of gases only a few drops of water are ^ 
duced ; but when it is recollected that the gases were il 
their dastic state, and that now they have parted wW 
that heat which caused them to be self-repulsive UV 
voluminous in bulk, the wonder ceases ; tbe heat irid 
which the gases have parted was that which consdCntK 
the flame. As inflammable air is thus proved to be 4l 
most remarkable ingredient in the formation of water 
this gas has obtained the name of hydrogen *, sigmfjiiil 
vsater-form itig. 

Between oxygen and hydrogen there is a reraarlab!i 
difiference, which deserves notice. Hydrogen ia a com 
buatible body : but if a buminp; body be immersed in il 
the combustion ia extinguished. If a burning body b 
introduced into oxygen, t\\e comWsikhH ^iwa wiwilh b 



107 

fjr greater intenwty : but oxygen itself cannot by any 
nitins be made to burn ; it is therefore incombustible, 
liiliflugh it supports combustion. From facts of ihia 
'iiu!, a distinction of bodies into combustibles and sup- 
ifffM 0/ comhiiglion bia been made, and a classifi- 
uncm of all the bodies in nature has been founded on 
tliediatinclion. This is, perhaps, unfortunate ; the pro- 
(iritlf of it depends on the meaning; of the word com- 
lnutiini: and the definition of combustion which would 
Knia die distinction proper is too restricted, and caL 
WliWd greatly to perplex the theory of that process, as 
*31 ippear hereafter. 

During our examination of air and water, we have 
lidnd at the knowledge of some important and strikiag 
fKIa, We have seen that the wholesome air, whidi 
i« inflispeiiBable to the life of animals, contains the 
(letnentB of destruction : and that the most incomhua- 
tiUe of all bodies, water, ia composed of the eleiuents of 
Bk. In short, we have obtained an acquaintance with 
Wygen, azote, and hydrogen, — substances which hold 
«e most prominent place in creation : and we hare 
'orned that these bodies, by union with each other, form 
ddiers of agencies just aa extensive. Oxygen and azote 
iurm a powerful acid, possessed of violent properties j 
"lygen and hydrogen form a passive compound, chiefly 
''inarkable for its inertness ; but of the action of hy- 
'" i;:;en and azote on each other, whether they combine, 
'ilifso, of what nature the compound may be, we as yet 
:i:nv nothing. If hydrogen and azote, botji in the elaatie ■ 
' i'.E.', be mixed, no change follows : but we are not to J 
'" '0 far misleil by this fact as to conclude that there ia ■ 
■1 afKaity between them : we have learned by the ex- l 
[HritTice of azote and oxygen, as well as of oxygen and 
bfdrogen, that although powerful affinities may subsist, 
aumc management is often required to induce a combin- 
ation. Accordingly, a mixture of oxygen and hydrogen, 
when forced to an approximation of particles b^ Ti\e- 
dimiea) compreBsion, actually lose their elasticity, atv4 
combine witli explosion^ formiDg water. IE bj^Ogjeiii 



The ocean, along with rivers, lakes, and apring 
otqecte which, after the atmosphere, claim mi 
tention. They Ehall all be considered under the g 
name mater. 

To an ordinary ohserver, water might appear, 
it was once believed by philosophers to be, a simpl 
ment ; not composed of other ingredients, bat i 
same nature throughout. This is far from beii 
case; and that it is a compound is easily demonstt 

Every one must hare observed, that, when wi 
thrown on a hot Are, or when a very hot ii 
sprinkled with water, there is a disagreeable and 
liar smell evolved, he the water ever so pure. 
fire be exceedingly hot, like a forge, the water will 
somewhat like ardent spirit thrown on it. If a 1 
iron, heated to whiteness, be partially immersi 
water, the water clischarges a kind of air, which 
fire from the iron, and burns for a moment.* Tl 
may be collected by passing; the white.hat iron, or 
ignited to whiteness, under a bell-glass filled with ' 
and inverted, in a vessel containing water.t Bubl 
gas will be generated abundantly at the iron or coa 
will rise to the top of the hell. By heating th 
bar several times, and immersing it, and, after eac 
meraion, hammering it a little so as to detach some 
scales that farm on it, the bdl may be filled wit] 
Better methods will be given hereafter. 

This gas has two remarkable propetdes : it I 
ceedingly light, being scarcely more than ^^th { 
weight of the same hulk of common air.:|: It is ve 
flammable ; a stream of it will burn, on the appli 
of an ignited body, with the emission of intense 



Jinary al 



TitnUDnea, tt«^ n 



IP 



9BE WATERS. 



but little or no light ; yet a lighted taper immersed into 
a phial of it will be instantly extinguished. This gas 
is, therefore, of a nature quite different from the two 
gases which have been already described : it does not 
resemble oxygen, or azole, or any of their compounds. 

It has been stated, in die last section, that iron may 
be burned in oxygen gas. In the experiment there 
described, it was observed, that the iron wire, id 
burning, melts down into black, brittle globules, no 
longer metallic, although they have a lustre approaching 
lie metallic ; and still attractable by the magnet, al- 
4uugh now an oxide of iron. In the experiment, just 
Mw described, witli the white-hot iron bar, it ia ob- 
servible that the scales hammered off are an oxide 
nfiron, in every respect the same as the former. Now, 
Kbence was the oxygen derived, which thus united with 
uie iron ? The only substances concerned are iron and 
water; it is, therefore, an unavoidable inference, that 
tteoxygen was derived from the water, and that oxygen 
i" one of its component parts. The experiment may be 
inaile in a manner which renders the truth of thia 
pwidon quite manifest. Let the steam of boiling water 
be passed in at one end of an iron tube, containing iron 
turnings or borings, the tube and contents being kept at a 
bright red heat : let a flaccid bladder, from which the 
sir liaa been previously well squeezed out, be tied at the 
otiierend of the tube: the bladder will speedily be dia. 
t<ni<ied and filled with the gas in question ; the iron 
turnings will be converted into the same oxide of iron, 
'file passing of the steam over the iron may be continued 
until the whole of the water has been converted into 
steam, and thus forced through : the results are the same 
lothe last: inflammable air incessantly passes tlirough 
"lie tube, and oxygen is continually absorbed by the iron. 
^Vhen the water is exhausted, bath processes 
tuere are no other products. 

I It must be inferred from these facts, that 
Kdnble into oxygen and in^ammable air - and 'ia& \ViA 
onpoeed of cbese tfi'o gMses. It might also a^pea.i ^s!t 



I 




I 



be divested of its elasticity, and presented in this state 
to azote, an union takes place equally, and a compound 
is produced po&seGsed of energetEc properties, and veiy 
different from those of its component elements. But 
the hydrogen is not to be deprived of its elastidty by 
mechanical compression, as in the former case : the same 
object can he effected hy a much more easy method : 
let the hydrogen he presented before it has acquired 
elasticity, at the very moment of its birth as tve might 
My, or, as chemists express it, in the nimcent stal«. Al- 
though, in the processes juat now described for obtaining 
hydrogen, heat was made use of for liberating that gu 
from it« combination with oxygen, it is to be observed, 
thatheat only hastens tlie subvecsion of the affinity whidi 
holds the elements of the water together; the same 
changes may be effected without elevation of teni" 
perature, but they will take place very slowly. If iKU I 
filings be mixed with water, minute bubbles of hydroga 
will at length be seen to form round the particles of 
iron; the oxygen does not appear, for it combma 
with tlie iron. The hydrogen becomes visible, becsuK 
each particle of it has received the caloric necesaitj 
to its existence as a gas. But if the mixture of iroo 
filings and water be confined in a vessel containing 
nothing but azote, the azote will exert its affinity at die 
very instant when each particle of hydrogen has been 
eliminated from the water, and before it has had time to 
derive the necessary heat from the surrounding medift. 
Id this state of things, a combination takes place ; (be 
hydrogen does not make its appearance, and the anrte 
actually disappears ; and when we came to examine the 
contents of tlie vessel, we find neither azote nor hydrogeDi 
On opening the vessel, instead of an inodorous mixtUK 
of gases, as pure hydrogen and azote would be, it has 
acquired a smell of great pungency, identical with 
that emitted from what is called srmeUiiig aalln or harlt' 
horn, both of which owe their qualities to its presence. 
Water absorbs this gas witb av'iAUy, a\i4ivSOTilaa.li<\uid 
Jiaving the same sroellj a pungetvt caustic VasVe, a.via.^aA 



IUt.*rn. TBS WATBBS. 

I'lipert^ of reddening, ar even blistering, fhe skin whetf 1 
qiplied to it. 

In treating of the nimoBphere, it was suted, that, when 
fficjgen tuid azote are combined in a certain ratio, a 
canpound is produce<i whicli poeeesses the property of 
chai^g vegetable blue colours to red ; and it wai 
nenfioned that this property constitutes t!ie quality 
ciDed addity. We have now to examine whether the 
eiiin[Krund produced by the combination of azote and 
^iiogein possesees this quality. If some of this pun- 
gent liquid be added to water in which violets had been 
iofined, the blue colour will be instantly changed, not 
to red, but to green ; and the same will happen to any 
■ olher vegetable blue : or, the vegetable blue having been 
ueady reddened with an acid, if a sufficiency of this 
oinpound of hydrogen and azote be added, the red 
"liour will disappear, and the original blue will be 
fisiorei! ; and if still more of the compound be added, 
iiic blue will be changed to green, just as if no acid had 
ijteii ever added. 

'I'here is here not only a difference, but a decided 
opposition of properties. IVhat the acid does, this 
compound undoes : it not only destroys the rednna^ M 
Du»sioned by the acid, but it communicates a colon*' | 
charaeterifitic of itself. 

As the term acidity is attributed to bodies which 
have tlie power of reddening vegetable blues, so to the 
quality of rendering vegetable blues green a peculiar 
term has been appropriated ; it is called alkalinUij; and 
the bodies which possess this property, — for it will be 
hereafter seen that there are many, — are called aUsaliet. 
They possess another power, also, over vegetable colours; 
they convert yellows to a deep red, nr, rather, brown : 
and the infusion of the dye-stuff called turmeric is used v 
for this purpose. M 

It may excite wonder that such importance should bff^ 
attached to the apparently trivial circumstance of chang- 
ing the hues of ve^e/ji6ies, as to induce chemists to went 
Ki-ina indicative of generic distinctions amongsl "ViOiliea, 



f 

^^ founded 



tLEUEHTS OP CBElUSrRT. 



I 



founded on this quality. But the cause of wonder n- 
niehes when ne team that the effect on colours is merelj' 
■n easy tent, a visible announcement, ifaat each of iIhk 
ddsses possesses a distinct set of properties. We connM 
Mch change of colour with the posseasion of a eerOSH 
•et of propcTtieE ; and, by the application of this ten if 
colour, we infer the existence, and attribute the p«- 
KHJon of a whole series of properties to each cImb. 

Adib and alkalies are considered aa opposed to etch 
Other in their nature, and each presenting a kind o( 
reverse property to the other. They have, genendlfj 
■ powerful BfRnily for each other; and, obeying tlut 
tflinity, they counteract and lessen each other's ch>' 
ncteristic effects. Thus, an acid has a peculiar taaKj 
expressed sufficiently by its name ; it is aometimes M 
powerftil S3 to be corrosive and poisonous. ' An albli 
tu« also a peculiar taste, quite different from an mi', 
it also is often caustic and poisonous. If both of the« 
violent and pernicious substances be mixed, we night 
fkirly expect to have a compound doubly violent mi 
pernicious. But the reverse is the fact. If, to an acii 
of this kind, a small quantity of an alkah be added, the 
■ournesii of the former ii diminiaheil, it is less coirosiie, 
and less poisonous: a little more alkali produces a little 
more diminution in the power of the acid ; and the caoK 
happens with further additions, until, at length, the pit' 
perties of the acid are completely null, — it is no longO' 
■our, no longer corrodve, no longer pernicious, and it to 
longer reddens vegetable blues. Il is, in short, destitsK 
of effect on colours : its taste is salt and cooling ; aid 
in its general properties it is comparatively inactive' 
These changes are produced in consequence of llie 
affinities of the acid and alkaU having been satisfied: 
the ratio of tlicir quantity is such, that the point of 
aataration, explained in the chapter on affinity, is at- 
tained, and there is, consequently, a total ehange of 
properties, as is always the case when active affioidei 
have been in operation. But if, a&iex thia point of 
iias been attuned, the B,&^i.Snn ^ " "' " 



IHAP.7U. T«B WATBftS. Ill 

continued, the neutral and inactive state of the com- 
pound no longer suhsists: it now begins to assume 
acrimonious qualities; it again acts on vegetable colours: 
bat these effects are attributable to the redundant quan. 
tity of alkali above what was necessary to saturate the 
add. For> while the alkali was saturating the acid^ and 
destroying its peculiar powers^ the acid was producing 
a corresponding change in the alkali : the latter was at 
length deprived of its power of converting vegetable blues 
to green^ as the acid was of altering them to red. But 
aftor the alkali had completed the saturation, any further 
additions of it could effect no other change, and, there- 
fore, must remain independent and unaltered. This 
state of mutual saturation, where the peculiar powers of 
both bodies are suspended and concealed, is called n«ti. 
MUy; and the neutral compound is denominated a 
<(fft, because it generally has a saltish taste. The salts 
thus arising from the combination of acids and alkalies 
are generally disposed to undergo that symmetrical ar- 
rangement called crystallisation, which was explained in 
the chapter on cohesion ; and each separate regular form 
is called a crystal. 

It does not) however, follow that a salt must be neu- 
tral, because neutral compounds are designated salts : 
on the contrary, salts may either manifest the possession 
of acid or alkaline qualities. In such cases the salts are 
not neutral, and yet they may have been saturated ; for 
it does not follow that neutrality and saturation should 
always accompany each other. It is possible that an 
dkaline body may unite with such a quantity of acid as 
saturates it, although it still manifests alkaline properties, 
and is not neutraL 

The substance with which an acid is combined in a 
salt is called its base : thus, the alkali is called the base 
of the class of salts just described. 

Having thus explained the nature of alkalinity, and 
having taken advantage of the first opportunity that 
occurred^ to show how this property is opposed to acvAit^^ 
bow the two qualities counteract and saturate each oxSa^et , 



«nd produce neutrality, we must return to the i 
of hjiirogen aail aiole, which was under consider) 
and from wliich this digression wis made in order iR 
the nature of saturation and neutrality might be more 
ftilly explained- 

In volcanic countries, a mineral is found which ocean 
in crystals, and In masses of a grayish, yellowish, of I 
brownish colour ; its taste is sharp, burning, and saltiEli. I 
The quantity obtainable in a state of nature is so v»T I 
insufficient to supply the demand, that it has been an ' 
object at bU times to form it artificially, ami the inge- 
nuity of man has supplied it in abundance. It wu 
once manufactured in large quantities in Egypt, near the 
temple of Jupiter Ammonj and, deriving a name fiom 
the place whence it was obtained, it was called gal am' 
tnoniac, — a name which it commonly retains tolhisdaf. 
At present it is manufactured in vast quantities in 
Britain, for it is used extensively in the arts. By itsdf, 
it bos no smell ; but when it comes in contact wilh 
lime, it discharges a pungent and sufibcating vapour, 
easily recognisable as identical with the pungent pa 
produced by the combination of nascent hydrogen and 
azote. If the powder of sal ammoniac be mixed with 
quicklime in a bottle, and a bladder be tied round the 
mouth, the common air having been previously piesied 
out, there will be an extrication of gas from the bottle 
as soon as heat is applied : the bag will become infiated 
by the newly formed gas : it will resemble atmospheric 
sir in its physical properties, such as being transparent 
eoburless, and elastic : but its smell identities it with 
the alkaline gas already described as composed of 
hydrogen and azote. The identity is confirmed by the 
facility with which the gas is absorbed by water, by the 
smell of the water thus impregnated, by the caustic 
taste, and the power which it possesses of changing 
v^etable blues to green. Jt will also saturate and 
neutralise acids. This volcanic salt, therefore, as well 
OS thai artificially obtained, holds &e alka,Une gas in its 
substance ; it is its basis ; and ibe al^aime ^lateaNKSSi 



Ma». TU. EARTHS AND HETAL8. 115 

Buned ammonia, or ammoniacal gas, from the salt 
vliieli giyes origin to it. Water absorbs upwards of 
40O times its bulk of this gas, and acquires some of its 
properties ; the compound is hence called liquid ammo^ 
nia. During the absorption of ammoniacal gas by 
water, the liquid becomes hot : for the caloric which was 
latent in the gas, and maintained it as such, becomes 
sensible as soon as the gas changes its state to that of 
a liquid, according to a law already explained : hence 
the temperature rises. At the same time that the gas is 
thus absorbed, the solution suffers a permanent expan- 
non, for the resulting liquid is specifically lighter. 

If liquid ammonia be heated, the ammonia takes back 
the caloric which it parted with when it was first con- 
densed in the water ; it resumes the gaseous form, and 
flies off in the state of gas. From the circumstance of its 
flying Q^ liquid ammonia is said to be volatile ; and the 
temi is applied to all other substances which pass off in 
vapour or gas at a low temperature. 

It has been shown that acids and alkalies have a mutual 
affinity ; that they combine and form salts. The name 
given to a salt is contrived to be an index to its composi. 
tion : it consists of a genus and a species : the acid 
contributes the generic portion, and the alkali the specific. 
Thus, the name nitrate of ammonia is given to the salt 
formed from nitric acid and ammonia. Chemists are 
loquainted with a vast number of salts. 



Section III. 

EARTHS AND METALS. 

When the almost endless diversity of objects is contem- 
plated, which present themselves in our survey of the 
nineral products of the earth, one might at first be in- 
;lined to abandon the attempt of studying their habitudes 
is vaxpraeticablej hut for the agreement of many o£ them 



Thai, there arc a immbcr of bodies wliicfa ocrhi 

hcaTy, and opaque ; ii-»li«ii*» in water ; thej pom 
peraliu- kind of brigfatnew or splendour; admit of b 
n U^iljt polished a* to be good reflectars of ^it; 
c^«ble of being meltfd by beat, and of recofering I 
aoliditjr by cooling : mou of tbem may be extende 
batamehag, and some into tbe thinnest fihni. ~ 



- and many different kiodi 

IS colours ; and they rei) 

a melt, or, as chemists la; 



bodies are called metal*; 
known. They a. 
different d^rees of heai ti 
fuM them. 

We find minerals which erinee some of the 
perliea of metals, a> opacity, great wdght, Aomet 
^lendour, and at aD tiroes convertibility to the mel 
uaie : theie are roetals combined with oiber bod 
ihey are called ore* ; and it is in this slate that m 
occur in nature, and from it that metals are extract 

We find minerals which possess some InsCre, n 
weight, hardnecs, and transparency : they are insol 
in water, often infusihle in the tire, and little tltei 
by heat, unlesst he most intense : they assttme iq 
cryecalline forms. These are called *tone». Sotnet 
they are of decided and beautiful colours, perhifis ti 
patent, exceedingly close and hard in texture, 
smooth and brilliant in fracture. These are called 
eiou* $ti»ne» or gems. 

There are mineral bodies which, in their eKtemal 
raclera, resemhle the preceding class, but are distingni 
*ery decidedly in others. They are in beautiful km 
gular forms; they possess lustre; are sometimes colon 
they are generally acted on by a moderate heat ; ant 
very frequently dissolvable, or, as chemists say, total 
water. These are called native mlta, to distinguish t 
from lalla which are prepared artificially. 

Other minerals are distinguished chiefly by their c 

flnutibiUty ; such are sulphur, bitonii;iis, coala, &c. 
Ja tbe mineral, us in the vegetabVe Vkv%4(i\q, -b^ 




;i variety of acids anU alkalies ready formeJ, which, it'm 
ihey are not peculiar to miDeralS] are at least found 
lUDiigat them in couaiderabie quaotity. 

As to area and metala, no further notice need he taken 
of them in this ilivision of the work : tlielr place in 
creation, and their nature in general, are sufficiently 
known to every one. Rocks, stonea, ami earths appear 
digsimilar to each other; the hardness, closeneaa of texture, 
ami weight of the former, seem to distinguiah them from 
Lhe laoseneea, aoftneaa, and lightnesa of the latter. Yet 
observation shows that the nature of all of them is the 
urne; stones and rocks are often found mouldering into 
urih, and earth ia known Co harden into stone. The 
process of mouldering produces no change further than 
breaking down the cohesion of the rock : accordingly, we 
find, the soil at the foot of rocky mountains to contain 
ibe same ingredients as the rocks themselves. 

With regard to earth, very little palpable difference 
mn be perceived in the great bulk of it ; it is apparently 
much the same in all parts of the world. But rocks and 
stones are found in every variety of aspect, and com- 
posed of very different materials. Now as these, when 
broken down into small particles, or powder, constitute 
earth, chemists have denominnted the ingredients of 
which rocka and stones are composed, eartlis,- and these 
are, consequently, of different kinda. 

The beauty of the precious stones has brought them 
into such general request for ornamental purposes, that 
iheir external characters are well known. Notwithstand- 
ing their valuable qualities, they are, with two or three 
exceptions, composed of the same materials as the com- 
monest stonea. In the following account, such minerals 
only shall be noticed as make us acquainteil with some 
new substanoe. 

The sapphire ie, in point of value, second only to the 
diamond : it is of various colours ; but the blue and 
red are most esteemed, the red being more valuable. 
Sapphires are brought from Ceylon, and otliet OrieWaJ 



s well as from some parts of Europe- 
red sapphire is commonly called Oriental ruby, and 
yellow kind is the Oriental topaz. These stones, n 
nibbed, often emit a phosphorescent light. 

The sapphire ia almost entirely composedof ap 
Uar kind of earth, which, singular to say, is one of 
most abimdant and common in nature, notwithstani 
the great value set on the gem. The same kiud of c 
constitutes the basis of all day soils ; it is the in 
dient which gives porcelain earth and potters' claj 
plasticity and ductility that permit it to be moulded 
the various kinds of china, delft, &c. It is the i 
ingredient in pipe-clay and in common roofing slate, 
is named by chemisis argiilaceowi earth, or ahimiaa. 
every 100 grains' weight of blue sapphire, 92 are; 
alnraina ; and it owes its beautiful aod much va 
colour to so small an admixture as 1 grain of iro: 
every 100 of the gem. 

The next of the precious stones which it is neeea 
to describe is the amethyst. The kind most genei 
known is of a purple colour, although it occurs of c 
hues. The most esteemed are tliose brought from I 
Ion and India ; those next in value are ttie Brazij 
they are found also in Ireland, although of infi 
beauty ; and in many other parts of the globe. 
amethyst is composed of a basis quite different tjoui 
kind last described ; but, like the last, it ia abunda 
diffused throughout nature. Every one is acquai 
with the stone called flint; it is very common, 
therefore of little value ; yet it is composed of the i 
materials as amethyst : the latter contains, in 1 00 gr 
98 of a peculiar substance, which, from w/ej, the 1 
name for flint, is called *i7ico. Of the same subat 
as the amethyst and flint are composed the gems ci 
camehat), cat's-eye, rock crystal, Egyptian jasper, 
opal. The last, distinguished by the name of pre< 
opal, is one from most beautiful of gems, and jet 
tains, in 1 00 grains' weight, nodung mtne than 90 g 



'. (U^Vu.. 



nfi 



of silica and 10 of water. Notwithstanding the high | 

ptioe and beauty of these stones, the material of which | 

lliey are composed constitutes the great bulk Of the sand J 
uhich lies Talueless on our shores. 

Silica is an essential ingredient in glass, in all sorts | 

of pottery, and in artificial gema and enamels. It is . 
ibundant in nature, and sometimes constitutes the bulk 



It was, some years since, believed that silica is an earth 
Ualogous to those already described ; but it has been 
Jiscovered that this is a mistake, and that it is of a very 
iBferent nature. It has been here iJescrilied amongst 
fteeartha, merely because it is [he basis of a number of 
pncioiis atones ; and its real nature, as far as known, 
nO be pointed out hereafter. 

There are some gems of great beauty and value com- 
ptved chiefly of silica, but containing also alumina ; as 
the garnet ; the Brazilian topaz, wliich must be distin- 
^ihed from the Oriental; and theOccident^ or preciouB 
herald, of which the beryl is a species. 

The emerald and beryl are not, however, entirely com- 
posed of silica and alumina, but contain also another 
urlh, with which it is necessary to become acquainted. 
From its property of forming combinations which have 
) Eweet taste, it has been named glucina. 

There is a peculiar substance, until lately considered 
in earth, which constitutes the great bulk of the gem 
called hyacinth. This stone is found in - 
tries ; but the most valuable is from Ceylon, which 
ihe repository of all rich gems. Hyacinth occurs 
brown, yellow, and green : every 100 parts of the s 
contain 70 of the substance under consideration, 
was first discovered in a sjiecies of hyacinth called the 
zircon, and hence has been named zirconia. Besides 
oUier places, the zircon is found in Scotland. Its nature 
is not fully determined. 

The last of the gems which introduces to ovur fcnow- 
ledgt a peculisr earth, is one that is knowa oiA^ W 



°4 



minersIoi^gtB ; it is called gailolicite. &om ttte bud 
the Swedish, chemist, Gadolin, who discovend Utat 
Deral. In this atone was found the earth in quest 
and it obtained its name from the pUice where tlte 
oeral was found : it has been called gttria, from Ttte 
in Sweden. Its phyaical characters are not very difi 
from those of the preceding earths. 

In introducing the smdeot to the knowledge of 
precedinf; earths, the gems have been adduced u 
amples, on account of th«r containing then in f 
puritjr, and as suhatances with which being ttmili 
acquainted, we acquire a knowledge of their cmnpoi 
earths with Less of the difficulty and abruptness atleni 
w take leave of these, mil ; 
eeed lo consider the nature of a much less costly dit 
minerals, although, in point of utility, some of them 
of far greater importance. 

Every one is acquainted with (he stone called mar 
its direreiAed hnes, or its pure whiteness, and its h 
when polished, have introduced it as a beautiful mat 
for ornamental archilecture and sculpture. Matbla 
of all varieties and mixtures of colour. Notwithstan 
their value, they are the same substance with com 
limestone and chalk, with a slight difference onV 
purity. Limestone is one of the most abundant min 
in nature ; it sometimes constitutes the Gahstanc 

The huming of limestone is a process commo 
mr>st parts of the world. The stones are broken s) 
and stratified with fuel in a kiln, which, when sel 
to, heats the stone red-hot. During the burning, 
limestone becomes much lighter. It is now called qi 
lime, or rochc-Iime, and its properties are totally chai 
Water poured on it is immediately absorbed, and the 
appars as dry as ever. In some time, however, it sv 
bursts, grows hot, discharges Eteam, and falls to pov 
This powder is called slaked lime. The same ph 
mcria are exhibited by marVAes an4 ^sSk aSWi ^aar 
if similarly treated. 



There are two minerals very different from limestones 
sncl marbles, anil from each other, which, however, agree 
wilh limestone in the properly of affording eartlis that, 
nhen cold water is poured on them, become suddenly 
bnt, and undergo the process of slaking. These minerals 
are named carhonate of baryta and carbonate of strontia; 
md, from these names, the two earths obtained from them 
ire called baryta and ttroritia. 

Baryta is distinguished amongst the other earths by 
being a violent poison, and also by being the heaviest of 
ill the earths; hence its name. Strontia is not a poison. 
The only remaining earth is one that is well known ae 
>n extensively used and popular medicine ; this is called 
"mgmsia. It exists in various minerals ; one of which, 
found in America, consists, in 100 parts, of 70 mag- J 
neeis and 30 water. I 

The preceding earths are all which the ingenuity <jf n 
I'hemistB has been able to discover ; and of these are 
composed all (he gems, stones, rocks, mountains, and 
Mils, that are found throughout, and constituting, the 
globe. Some of these minerals contain hut one earth; 
otiiers two ; and others so many as four. From this ex- 
amination we learn, that the solid parts of the globe, 
SE far, at least, as human industry has discovered, are 
Composed of a few earths and metals, each being pre- 
sented under ati astonishing variety of forms ; and it will J 
presently be shown, that the distinction between earths ■ 
and metals, evident as may it appear, is not well (bunded. I 
It had long been observed, that the properties of eartbi \ 
very nearly resemble those of the compounds of oxygen 
and metals called metallic oxides : but it remained for 
the chemists of our own day to prove what their prede- 
cessors had so sagaciously suspected ; and, of late yean, , 
it has actually been demontrated that earths are them > J 
selves metallic oxides. This has been shown by theV 
very simple method of abstracting oxygen from them J- 
ind determining that, in each case, globules of a peculiv I 
metal made their appearance. To metalliae iKe v 
I * 



:nted,j 
the Utter 
produced. 
named all 



it is onlj neccEEary to mbvert the affinity BubEiGting 
between the metallic basis and the oxygen, by ttieani 
of some body having either a naturally Etronger affinilf 
for oxygen than the basia, or made to have it by »rl. 
The oxygen being nithdrawn from the compound, tbt 
basia will make its appearance id the melallic alaia 
But although the description of this method seems sim- 
ple, and easy of accomplishment, there are difficulties 
in the way, and such as require the exertion of no or- 
dinary skill to surmount. IVTiat these means are, it i> 
not here necessary to detail; it is sufficient to say, thit 
it was chieSy through the application of the powerful 
^ent called galvanism that the ditBculty was overcome: 
but the mediation of natural affinities was sometime 
sufficient. When any of these earthy metals was pn- 
m elevated temperature, to the action of oxygea, 
was absorbed, and the original earth was re- 
The metals obtained from the earths an 
icinum, yttrium, calcium, barinnii 
L. To this list a new metal haa 
lately been added : it has obtained the name of thorium ; 
being extracted from a mineral of a very complicttrf 
nature, called thorite- 
It appears, therefore, from the investigations of mo- 
dern chemists, that the globe of the earth is one vait 
mags of metals of different kinds, disgtiised by varioni 
substances, but chiefly by oxygen. 

There are three substances found in each of ^ 
kingdoms of nature, which, in their properties and cona- 
ptisiiion, are nearly relnted to the earths, and an 
in daily use in aria, manufactures, and domestic economy: 
they are called potash, soda, and ammonia. They all 
possess the properties of an alkah in a high degree; 
and, indeed, in many respects resemble each oth^< 
There is also another alkaline substance, which belong) 
to the same class, but differs in being exclusively of 
mineral origin : the name lilhia lias been given to it, 
ligniBcant of its atony origin. Potash, sada, euid lithik, 



«IAF. yn. BABTB8 AND IfETALg. 121 

hftye been proved to be of tbe same constitution as the 
earths; and metals of extraordinary properties have been 
produced from them by abstracting oxygen. On account 
of the sources from which they are obtained^ the metals 
are called potassium^ sodium^ and lithium. Ammonia^ 
although powerfully alkaline^ and analogous in its qua- 
lities with potash, soda, and hthia, differs from them in 
the circumstance of not being a metallic oxide ; and, in 
this respect, agrees with a numerous class of alkalies to 
be noticed hereafter. Its composition has been already 
explained : it consists of hydrogen and azote, neither of 
which is known to be metallic. As these four substances 
evince the possession of alkaline qualities in so high a 
degree, they are named, by way of en^inence, the alkalies: 
hut some of the earths possess the same properties, al- 
though in a much less degree, and are called alkaline 
earths; such are lime, baryta, strontia, and magnesia. 
To this property the substances called alkalies superadd 
uiother, namely, solubility in water: potash and soda 
dissolve in water readily, and in large quantity. Am- 
monia exists in the gaseous state, and is largely absorb- 
able by water. Lithia is but sparingly soluble ; so also 
are lime, baryta, and strontia : hence lithia is, in this 
property, connected with the earths ; but it is separated 
fit)m them by its caustic, acrid taste. Potash, soda, and 
ammonia, are easily soluble in strong spirit of wine: 
lithia is not so; and this, again, connects it with the 
earths. 

Opposed to the alkalies and earths, in properties, are 
the acids of which some mineral substances are partly 
composed ; and which we find in the mineral kingdom, 
existing in an uncombined state also, and sometimes on 
a scale of immense magnitude. There is, in the island 
of Java, a volcano called Mount Idienne, from which the 
Butch East India Company have been often supplied 
with sulphur for the manufacture of gunpowder. At the 
foot of this volcano is a vast natural manufactory of 
that acid commonly called oil of vitriol, althougYv it \» 
5*fine diluted largely with w&ter : it is a lake a\)OUt \2.00 



French feet long; the water of which is warm, of a green- 
ish white colour, and charged willi acid, from the sur- 
face of which a shght smoke rises. Towards the south- 
west, the lake discharges itself, and forms a river of the 
same acid. The taste of this liquid is sour, pungent, 
and caustic ; it kills all the fish of a river into whidi 
it flows ; gives violent colics to those who ritink of it; 
and destroys all the vegetation on its banks. VThen ■ 
little is evaporated by heat, pungent sulphurous vapoun 
arise, similar lo those discharged from the volcano, and 
some sulphur is deposited. From this account, it is 
plain that there is some intimate connection between the 
acidity of the liquid and the sulphurous fume occasioned 
by the incessant combustion of the sulphur. The water 
■eema to have absorbed these vapours, for these very 
Tapoura are exhaled when it is heated ; and that such 
vapours are aufSeient to cause the acidity, any one may 
convince himself, by the simple experiment of burning 
Bome sulphur in a glass globe full of air, in the batten , 
of which a little water lies : vapours are formed, wbid ■ 
the water absorbs ; it becomes sour to the taste, and ' 
now reddens vegetable blues. Such is, in fact, the 
voy process that is continually going forward in the 
volcano ; and the result is this acid in enormous quan- , 
titiea, produced by the combination of sulphur with 
osygen derived from the atmosphere. 

Chemists had long been acquainted with the acid under 
consideration ; but it was only within a century that it 
was known to be produced by the burning of sulphtu: 
&om the origin of the acid, chemists have given to it the 
name of tulpkuric arid. It was formerly called oU (/ 
vitriol, because it was distilled from a substance of mi- 
neral origin, called niiriol, on account of an imperfect 
resemblance to green glass ; vitriolum being the dimi- 
nutive from vitmm. It is now manufactured in Britdn 
on an immense scale, by the burning of sulphur; its 
uses in the arts being extensive. 
This lake is found to contain jAbo amovWi wid, with 
tproperties quite distinct from those <A tVe wA^omB- \\. 



) METAM. 12S 

J ijuanlity of its water be Buhjecleil to the process of 
Ming ill a glass flask with a bent neck, called a retnrl, 
'" ihtt (he steam which passes over into the neck shall 
lu there condensed into liquid, we obtain this second 
■-riii. It ha* been found in Tarious products of other 
lolcanic countries, by Spallanzani, Vauquelin, Breislak, 
niii] others. The last of these observers found it in a 
li>mi which, in itself, is a characteristic sufficient to dig- 
liii^ish it from the sulphuric : he found it in a state of 
v,i|>aur, as a permanent ~gas ; at least, so far permanent 
t^ai it would remain a gas for ever if not brought in 
L'dntact wiih water. This fact shows that liquidity is not 
ik- state in which this acid exists in its most simple 
lomi : the liquid consists of the gas dissolved iti water ; 
!'>! siich is the affinity sobsisting between them, that the 
['iasiicity of the gas is subdued. 

The celebrated traveller and philosopher Humboldt 
tuund it in a number of warm springs in Mexico, scat- 
I'Tcd orer a space of forty square leagues of volcanic 
.™ntry. 

It appears thai this acid is contained in vast abund- 
iflce throughout the great boiiy of waters which sur- 
nunda the globe ; although not in a free and independent 
■late, but combined with soda and magnesia. It has, on 
'ias account, obtained the name of tituriatic acid, indi- 
utive of its being an ingredient in sea-water. 

According to the analogy of the acids already de- 
Kribed, we should suppose muriatic acid to be com- 
pound. That it is a compound, and what its com- 
IMnent parts are, it is easy to evince. Let a mixture 
i! oxygen and muriatic acid gas be passed through 
» porcelain tube, one end of which is red-hot, and ihe 
tKhet cold : a quantity of water will be found condensed 
in the cold end. Now, the elements of water are 
Mygen and hydrogen : we have supplied the oxygen 
in the experiment ; but whence came the hydrogen ? 
There was no olber bmly present to supply il but llic 
"iinadt; add; we must, therefore, infer that h^ATOgeti 
we of die coasiiiueiits of mwiatic acid, and we shoviA 



expect (o find llie other still in the tube. On enainiiiiiig 
the tube, we find that it contains a gas very difierettt 
from the original muriatic acid. If passed through a 
vegetable blue colour, it no longer rediiens it, but tolall; 
deprives it of all colour: it is now much less absorbaUie 
by water ; the solution has not an acid, but an astringent 
taste ; and the colour of this gas is greenish, althou^ 
the original one was colourless. The new gas does not 
extinguish flame, as muriatic acid gas does ; on the con- 
trary, various bodies, when immersed in it, take fire 
spontaneously. In short, the gas found remaining ia 
the tube is in every respect different from the original 
muriatic acid gas. 

This new ((as, in conse<|uence of the green colouri 
which is a distinguishing character of it, has been named 
tAlorhie''; and its compounds with other bodies are cilled 
ehbridm:. From the experiment, the results of which 
have been stated, it appears that muriatic acid can bl 
resolved into chlorine and hydrogen : hence these two 
gases, when united, compose muriatic acid; and hnii* 
this acid has been also named hydrochloric acid, io 
alluBion to the two gases of which it is compounded. 

Chlorine is an abundant element in the mineral Icing- 
dom: it is found in combination with the metal sodium: 
the compound is rock-salt. In sea-water it is associalm 
with two singular substances, cidled iodine and bromrat, 
both of which resemble it in many respects. The mot 
striking quality of iodine is, that, when heated, it ex- 
pands into a violet -coloured ga.s, which, on coolingi 
crystallises again into its original form. Bromine is s 
poison, a violent caustic ; and is capable of setting fiie 
to metals, by mere contact, at common temperature. 

'I'he basis of sulphuric acid, as alrcaily observed, i( 
sviphur. This highly inflammable substance is found 
abundantly in the neighbourhood of volcanoes, cryatal- 
lised in a state of purity. It exists, combined with 
metals, in a number of ores ; and in some of these,' 



tint of the copper-roineK of Fahlur 
isle of Anglesea, — it i; associated 
wedingly simitar to itself in all 
substance is called selenium. Its mi 
qoaliiy is, that, when in the stat 
idntigly of horseradish ; and one 
snuSi^d up the nostrils, produces 
wiih violent cough. 



lis I 

, in Sweden, wid the 
with a substance e: 
its properties. This 
]B[ easily recognisable 
; of vapour, it sraelis 
of its compounds, if 
catarrhal symploniG, 



Suction IV. 



Notwith a landing the perplexing diversity of form 
ithich vegetable substances assume, experiments have 
proved that they are all composed of the same ulti- 
Wite materials ; and these very few in iminher. We 
niiy aelect any vegetable structure as the representative 
of ill the rest ; and, by examining others in the same 
nanner, it will be found that they present the same 
results. 

The nicthoii by which the component elements are 
•eparated is simple ; the vegetable is merely exposed 
'o the action of fire, — not an open fire, for in this 
say all its parts would be dissipated or burned away ; 
Jul in a vessel calculated to retain its principles in 
'ich a manner as to permit their being brought under 
ixamination. Green wood will be a good instance. 
Pake a common gun-barrel, the touch-hole of which is 
topped ; push a small cylinder of green wood down to 
be breach, and place that end horizontally in a good 
oal fire. As the wood is heated, the water, which is 
he chief ingredient of its juices, distils over, and drops 
rom the open end of the tube. In proportion as the 
rater distils, from being insipid it becomes sour. 
Ihortly after, a gas issues out of the tube, and may be 
ailected bj tying a moist bladder, the coiumoTi ^1^11:^. 1 



I 



weU pressed out of it, round the mouth of tbcj 
If, wheu the gas ceases to issue, the cod 
ti^ be examined, the piece of wood will be found 
tered into a black, dry, light, Eonorous tnass, reuining, 
however, its texture, lliough much retluced in size. It 
18, in short, convened into charcoal, or, in ehemicil 
Iftnguagc, carlion; and if its weight be added to tlul { 
of the gas, the mere water, and the sour water, the it' 
EUlt will be the original weight of the wood without 
loss : hence these are all the ingredients which compoied 
the wood. 

Charcoal is a subEtance so well known that it ia ud- 
necessary to describe it. One of its most commonlf 
known properties is combustibility : if a bit be kindled, 
and s current of air supplied to it, it will burn ahnosl 
entirely away, leaving only a few white ashes of lltllc 
weight. In common air it buniE with no great bril- 
liancy; but if the experiment be made in oxygen gu, 
it burnB with considerable splendour. 

A remarkable circumstance attends the combustion of 
charcoal in oxygen, which is introductory to a fact of 
importance. Notwithstanding that the experiment is 
made in a glass vessel from which there is no eecap^ 
the charcoal totally disappears. It will also be found 
that the oxygen is completely altered iu its properda 
In ita original state, a lighted taper immersed in 
it would hum with the utmost brilliancy ; it mi^t 
be left in contact with water without absorption M 
change ; and, if the water were coloured with a ve- 
getable blue, its tint would remain mialtcred. But, 
ttfter the burning of the charcoal in it, it manifetti 
the reverse of all these properties : instead of increasing 
the brilliaticy of a burning taper immersed in it, tlw 
taper will be instantly extinguished, as would also the 
life of an animal ; if it be left in contact witli common 
water, it will be absorbed, the water acquiring a iharp 
taste, which is now capable of turning vegetable bitieato 
Tbeee propertiea dUdngaUtu aufitciently the ^ 



J^ This 
"■I from 

=3 Z' 



lAicIi reinwits after (he combuBtion of charcoal. The 
'fKEtiun occurs, uhut has become of the charcoal and 
Wtyj(en ? for both have diBappeared. A moment's re- 
Secuon supplies the answer : the charcoal and oxygen 
Rete originally in the glass vessel ; nothing has escaped 
hota the vessel; and, hence, the new gas whicli fills it 
nmst cousist of the two bodies' that disappeared. The 
liinge of properties which ensued, proves that a che- 
idcil Eombinalion had taken place between them : the 
durcaal was reduced to particles so small as to be 
xivisible; these combined with the oxygen, and a 
rompound gas was produced, consisting of these two in- 
gredients, nhich, as it possesses the property of red- 
dening vegetable blues, is an acid in the gaseous state. 
This gas has received a name indicative of its origin ; 
the Latin word carbo (coal), it is called carbonic 
itiigaa. Under ordinary circumstances it is invisible, 
Qmeparent, colourless, and elastic like the atmosphere. 

The beverage called sods water is almost entirely 
lurnposed of water holding carbonic acid dissolved. It 
II the presence of this gas in some wines i!iac causes 
iheir sparkling quality, and their efCervescence ; it aJGO 
mrtsdtutea tlie sprightlincss of bottled ales, and pro- 
'iuces the foam by its entangled efforts to escape. If a 
Itil of charcoal be kept red-hot for some time in car- 
bonic acid, will be diminished in weight, because some 
of it has dissolved in the gas ; and it will be found 
ihat the resulting gas is quite changed in its properties. 
Carbonic acid reddens vegetable blues ; the new gas 
itoas not alfect tliein ; carbonic acid is not inflam- 
mable ; the new one is very much so, and will bum 
Kith u blue flame. The quantity of charcoal contained 
in this new gas is just twice the quantity contained in 
carbonic acid ; 100 grains of oxygen uniting with 37 to 
fbnn die acid, and with 74 to form the new gas. 

Accordiog to a system of nomenclature already ex- 
pluned, the compound of charcoal and oxygen, in wlwh 
ihe oxygen exists in sack quantity as to produce aw acVi, 



m 



it aSkd tarbonic add gu ; bat the other one, in irhieh 
the oxrgen is iitsnfficietit to produce an add, is aUid 
earionic oride. 

A striking proof of tbe exlraaidinaiy difieHncti 
of appearance which the fame bodv may assume, trA 
also of [he intrinsic wonhlessness of some of those vll- 
jecti on which sodely sets the highest value, occunin 
the instance of the substance under consideration. Ensj 
one knows the enormous price at which diamond! (J 
good qnalitj' and siie are estiinateil. The celelHWid 
R^ent diamond, which was set in the handle of the lite : 
emperor Napoleon's sword of stale, is now valoed ll 
360,000/., although it wdghs only about 1^ oimrti 
and was originally purchased for 20,400/. by ThomM 
Pitt, grandfather of the great earl of Chatham, nhfle 
governor of Madras. Yet this precious omameot !• 
neither more nor less than a piece of charcoal; aDdiinl' 
prising as it may appear to those hitherto unacquaioKa 
with the fact, it is well proved, by numerous e]tpenniait% 
that] between the diamond and charcoal there is aloDBt 
no difference of composition : tlie diamond humi in 
oxygen with brilliant flame, anil, like charcoal, fonin 
carbonic acid ; like charcoal, it formi steel by comtdn- 
Btion with iron ; and the difference between the two 
bodies seems to be chiefly in their state of aggregatiM, 
the diamond being harder anil crystallised. It is alsoi 
little purer in composition. The pure portion of charcoil 
is distinguished among chemists by the name of «tirioih 
It has been already observed, tliat, during the heating 
of a piece of wood in an iron tube, a large quantity 
of -gas is given off with an acidulous water, Thfl 
nature of this gae is next to be enquired into. Ifk 
burning body be applied to it, as it issues from the iion 
tube, it will take fire, and burn with a white voluminoui 
flame, somewhat like a common gas-light. This pro- 
perty distinguishes it from the two inflammable gases 
alreadj' described — hydrogen and carbonic oxide; the 
I former of wluch burns with the enua&ion (A 'icucel^ iny 



eHAF. Yn. ORGANISED 8TRUCTUBE8. 129 

Bght, and the flame of the latter being blue. If the 
gas from wood be burned in a slender stream passing 
from a bladder furnished with a pipe^ and if the com- 
bostion be performed in a glass globe filled with oxygen 
gaS; the globe will in a short time become dull on the 
interior, owing to the condensation of watery vapour, 
and this constantly increasing, it will at length trickle 
to the bottom, and a quantity of water will be found 
there. The formation of water is a sufficient proof that 
bydrogen constituted a portion of the gas burned in the 
experiment. But the globe, instead of containing oxygen, 
>8 it did originally, is now filled with a gas easily recog- 
nisable as carbonic acid by its sharp smell, its capability 
of being absorbed by water, and its communicating to 
the water the peculiar acerbity of that gas. The pro- 
duction of carbonic acid proves that carbon was present 
in the gas obtained from wood, and we cannot detect in 
it any other element than carbon and hydrogen, they 
being.in a state of chemical combination, and forming 
'distinct variety of gas. On account of the two ele- 
nients which constitute this gas, it has been called car^ 
^reted hydrogen, — a name comprising several varieties ; 
the differences arise chiefly from the relative proportion 
of the constituent ingredients. 

Beside these gases, there are hydrogen, carbonic oxide, 
•nd carbonic acid, present in wood gas. 

In this analysis of wood we obtain, as already observed, 
* liquid of a sour taste, capable of reddening vegetable 
bines, neutralising alkalies, and, in short, possessing all 
the properties of an acid. It was once believed to be 
different from all others known, and obtained the name 
o{ pyroligneous acid, indicative of its being produced 
fix)m wood by fire. It has the taste and smell of tar ; 
for common tar is obtained by exposing wood to a 
strong but smothered heat, and this is just what happens 
to the wood enclosed in an iron tube. A process has 
been contrived for separating the tar from t\\e aciOi, a^xv^ 
then the add discloses its nature, its smeW beitv^ ivo 
ong^er disguised : it proves to be vinegar ; it is m^^e 

K 



I 



I 



on the large scale from irood, and is an excellent Lind 
for many purposes on accouni of iis great strenj^h ud 
purity. Hlien made its strong as possible, it oliuiiM 
&.e name of acetic acid, fioni the Latin wotd acrtam, 
finegar. 

We row perceive ihal the exposure of wood M i 
high temperature sffbrds a great number of compounds: 
Acre are two combinations of carbon ami oxygen, M 
least two of carbon and hydrogen, and one which iMHi- 
priees the elements of the former two. H'e see ills' 
pure hydrogen is also extricated, and we find ihit i 
little alote existed in the wood ; for it combined witta 
hydii^n, and formed ammonia, which is found nen- 
trahsed in the acetic acid. Tliese, with the cliar- 
coal, are (be results of the process ; and as a general 
cmnming Dp, we may recapitulate, that from wood *e 
obtain hydrogen, carbureted hydrogen, bicarbureted hy- 
drogen, carbonic oxide, carbonic acid, acetic idd 
holding tar, ammonia, and charcoal. By multiplying 
experiments on other vegetable structures, we learn ihit 
all of them, however complicated, when made to on- 
de^^ the ordeal of heat in confined vessels, resobt 
themselves, like wood, into the four elements — axygen, 
hydrogen, carbon, and azote; the latter being in snch 
small quantity as to be barely discoverable. TheK, 
again, by combining amongst themselves, produce the ) 
compounds above described ; but the four ingredienU 
mentioned are what are called the ultimate elementi of 
•11 vegetable matter, notwithstanding its apparent £- i 

The subject selected for elucidaling the conatitatiw 
of v^etable matter was wood, because it is a fair repTC- 
Eentative of all other vegetable bodies when submitled 
to daUruclive distiUaUon, as exposure of any ilecompo- 
■able matter in close vessels at a high temperature, sa 
as to collect the products, is called. But it is only 
when submitted to destructive distillation that wood can 
be considered as the lepresenlafr'e o?. wivct fe^jftihU 
matter ■ and w-hea we look lo tbe uMimatc ^lo&aEo. A 



I Vn. ORGANISED 8TRUCTUBE8. 131 

isdllatioo^ namely^ oxygen^ hydrogen^ carbon^ and 

ese are called the ultimate elements of v^etables^ 
se the decomposition has proceeded to the last 
that is attainable in their analysis. But besidea 

and their immediate combinations formed during 
structive distillation of vegetable matter^ there are 
combinations which naturally exist in the vegetable 
ire^ and which offer themselves to our observation 
It being subjected to any complicated process, 
combinations, being the nearest to the natural con- 
jn, and the more immediate objects of sense when 
amine any vegetable organisation, are called the 
tate principles of vegetables, 
eill not be necessary in this place to describe the 
ble proximate principles ; they wiU come in here- 

they do not need any introductory remarks, as 
rist ready-formed, and offer no difficulty to an easy 
ehension of their state of existence in nature, 
^ing acquired some acquaintance with the vast 
r of form under which the objects constituting 
sgetable world appear, and the simplicity of 
composition, the next subject of contemplation 
animated part of creation, — the most inte- 
; and stupendous of all. How much more ad- 
e and surprising must the structure of a living 

appear, when it is known that it is composed of 
iew elements such as have been formerly described, 
e more than the meanest vegetable, and fewer 
lany minerals. 
! materials of which animals are composed being 

the same as those which compose plants, the 
ice is in their relative quantity, and in the mode 
bination. The combustible substance, phosphorus^ 
3n detected in small quantity in some vegetables, 
the onion : but it exists in large quantity in the 
of animals, — not in the state of phosphorus as 
lily seen, hut disguised by combmalAOxi >N\\ii 
in the state of an acid, and this acid cotc^svae^. 

K 2 



irith lime. The banes of animals, tben, consist chiefly 
of lime and phophoric acid : at least these ingredieDtt 
compose their earth; basis, as il is called ; but it is im- 
pr^nated with animal matirr that adds greatly to their 
ctrength, toughness, and sohdity. The other clement 
which exiets largely in animal matter is azole : it is also 
a constituent part of several kinds of vegetable matter; 
singular that the same azole which adds so 
much to the nutritiousness and flavour of animal food, 
venders vegetable matter disgusting to the taste, and 
poiaonoue. This will appear more fully when nc come 
to consider the proximate principles of plants called 
vegetable allcalies, which are known to be highly azotated, 
and which are all bitter and deleterious. Mushrooms 
in much azote, as 1 infer from the circuni- 
) fltance which I have often observed, that their juice, 
during putrefaction, generates a large quantity of am- 
la ; for this consists of hydrogen and azote. There 
ot be a more deadly poison thitn some mushrooms, 
an illustrative fact, that mushrooms, on account of 
containing so much azote, approximate very closely in 
flavour lo animal food. During the deetructive distiL 
Ifttion of animal and vegetable matter, -we And difier- 
s of results corresponding with their difference of 
composition : animal matter gives rise to the production 
of ammonia, — a powerful alkali ; and vegetable macler 
■flbrds a product of quite an opposite nature, — the pow- 
erfiil acid, vinegar. 

The clrief substances, then, which enter largely into 

die composition of animal matter, are oxygen, hydrogen, 

mzote, carbon, phosphorus, lime. We also £nd some 

other kinds of matter, as certain acids and metals, but 

^ in quantity so small as not to affect the truth of the 

^L above statement, that the foregoing six ingredients coa- 

^B ititute the great bulk of the animal fabric. 



1 

li 

I 

1 

I 
I 



133 



PART II. 

ABRiNQEHENT AND EXAMINATIONS OF THB ELEMENTS 

OF BODIES. 



CHAP. I. 

ELEMENTS^ OR SIMPLE SUBSTANCES^ AND THEIR IMME- 
DIATE COMBINATIONS. 

hf diemistry^ the word element means what is otherwise 
called a simple substance ; — one that is not known to 
contain more than one kind of matter. When a sub- 
stance is known to contain two or more different kinds 
of matter^ it is called a compound. The metal iron is a 
simple substance ; it is of the same nature throughout^ 
and no other kind of matter can be extracted from it : 
but rust of iron is a compound^ for it may be resolved 
into metallic iron^ oxygen^ and carbonic acid. It is pro- 
bable^ however^ that many of the bodies which chemists 
at present consider simple, may be hereafter discovered 
to be compound. ' The expression^ simple substance, is 
not to be understood as conveying any positive affirm- 
ation concerning the nature of that substance, further 
than that it has not been proved to be a compound. 



Section I. 

OXTOEN. 

Oxygen gas is a permanently elastic fluid ; that is, one 
which jio compressing Force or degree of coVd \vv\\vet\ft 
sppliedj has ever condensed into a liquid ox ao^d. W * 

K 3 



I 



134 KLEKBHTB OF OBBMIaTST. MXtm 

ja transparent and colourless: 100 cubic inches of il 
weigh 33*9153 grains ; and, as the same bulk of com- 
mon air weighs 30'8II5 grains under the same dr- 
camstanceK, the specific gravity of oxygen must be 
1-1007.* 

Oxygen gas ntaj be obtsineil by the following priv 
ceis : Procure a cast-iron bottle, with a tube of iron 
ground air-tight into its mouth. Such are now coni' 
monly sold by the iron-founders for chemical purposes. 
Into this introduce a quantity of hlaek oxide of manga- 
, Beae, — an article sold by'most druj^atG ; tit in the tube, 
I and bed the bottle in a good coal flte, building smaD 
^"bita of coal all round, so as to heat the bottle to a bright 
red. Oxygen gas will soon begin to be extricated 
abundantly. In order to collect it let a bottle be filled 
•jO the top with water, and cork it so that the cork 
having excluded its own bulk of water, the bottle re- 
mains full. Invert the bottle, plunge its neck under 
vrater, and take out the cork under water ; the bottle 
will still remain full. The bottle and the vessel of 






"hsissm 


ini—FlrU F 


rinciflri, i. 65. 




Ihuctbnrgb E 


iTrlyf^ll 


ja cubic In 








! ninn br Hoi li 


i)iHtrent(TVM*(* 


'S^l^£. 


itlng°ce,'B' 1 




£-.ks;ks;s,',i 


aiflifrtftomlhi.: wd 


'SiM'S 


MOlhB 




lO™ whli* IKHCeV 




«/«->. L ■ 


SSL], (riihsM mm. 


aoning the »uthon[j, givra li»91 






aulI.>fei[i>er)n»L 






ih"l«iBn"6f.lllrei)fdlTI*, 












A litre, raliTiilitM a 


■em cipUIn Kiler's d 






«|i»lt»'i.-10!no<^t»<: 




1 estimau 




wd,iH)«.ugh Iheall 






, and of If 




mr(,dlin«IVDTii»h»l: 


liu<beriinr>d 


lb Ubie 


1, 1 beHeve 


them la be amea. 




ilculfllimi Ki 






it ta-^li^m^eMa' 


iuches. The 


■ ml'ic i 


Tich of ws 


tet al IS° bH been 


tOaaa lo weigh eiSl5§ 




i..S58-fl 


» gnllis a 


leu^. T>kln(lbs« 






«, temper. 


.ture.ai.d.<>lumeor 


*lr g<nn br Bipt inu 


EOEliih InrhF 




.Ii>i. 1 a<.d 






iJrj.lB,Hii.herlciilr 


welgh^ail 


IgSgiaini. 


ButiitO. S.EtdTn 


ini\ M. B>nt 






o'amrai5?"f( H 




c mule vlth 


grMt 1 


illenlLm*^ 


OenOre. pnner ttiH 






in of Ijolh 


: the mean at both 


OBmbrn It SimiB gni 


niiinillhlil 


n*the™ii«hloH« 


in«K\M!wior.!E 


Vcl.l.b„admitted,%f 


obuln the meoific a 


rBv\H'Xo 






15:3391ii 


■.■.\-m 


1 -. V\tfn35.«ltatt«V3V 



CHAF. I. 



OXYOEN. 



135 



water should be previously so arranged that the end 
of the iron tube can be plunged under the surface of the 
water ; or, if the iron tube be not long enough to reach 
the vessel of water, a tin or copper tube may be slipped 
on the end of the iron one, and a piece of wet bladder 
tied over the juncture. The gas will bubble up through 
the water : the first portions will be common air, con- 
•tained ift the iron bottle and tube expanded by heat. 
When this has been allowed to escape, slip the mouth 
of the glass bottle over the end of the tube, so that the 
bubbles of gas may enter the bottle. In proportion as 
gas enters, water will leave the bottle ; and when it is 
filled with gas, put in the cork and remove it ; or, with- 
out putting in the cork, pass a cup into the water, under 
the mouth of the bottle, and remove both bottle and 
cup— the latter remaining filled with water, so as to pre- 
vent gas from escaping, or common air entering. Other 
bottles may then be filled in succession. If cylindrical 




jars, or bell glasses, are to be filled, they may be treated 
in the same manner, being first plunged down into water 
so as to fill them, and then raised up with the mouth 
downward, taking care that the mouth always reniains 
an inch or two under water, so as to prevent common 
air from entering. The most convenient vessel for 
holding water for these purposes is a trough or cistern 
made of wood or japanned tin, with a shelf about two 
inches under the intended surface of the water, for sup- 
porting jars or phiah while they are filling w\l\v if^-aja. 
The shelf is not absolutely necessary. This vesaeV \a 



' isff 

called tbe pneumatic trough, and is useful in all rases 
where gases are concerned, unless the gas be Hb^Drbtble 
by wBIer. It will, id procuring oxygen, be adviubls 
that H little newly sUkeil lime be ilissolved in A» 
water: for this will more certainly absorb any carbonie 
acid that tnay be derived from impurities or adulteratiom 
in the manganese, both of which are often found id that 



If a cast-iron bottle cannot be procured, one of the 
iron bottles in which mercury is imported may have an 
iron tube fitieil to its mouth. Or, if this method is not 
available, the following may be employed: — Let a com- 
inon Florence oil flask have its mouth strotigly wound 
round with cord for an inch downwards, in order that 
it may not be burst by tightly fitting a cork to it. Let 
a perforation be made in the cork with a round file, and 
a glass tube inserted into i(. Manganese is to be intrO' 
duced into (he flask ; sulphuric acid is to be poured on, 
in quantity sufScient to wet it thoroughly; and they are 
to be mixed. The cork and tube being pushed in, ind 
the whole made air-tight, the heat of an Argand lan^ 
or the flame of a cup of burning spirit of wine, is to be 
applied. In a short time oxygen gas will come oTer, 
the first of which is to be r^ected as containing com- 

Or some nitre may he introduced into a gun-barrd, 
the touch-hole of which is closed : a piece of commaii 
gas-pipe may be fitted air-tight by luting a wet bladder 
to its mouth, the other end terminating in the watK 
datem. The end of the gun-barrel containing ibe 
nitre should then be healed in a good coal fire to rednesb 
Gas comes over, but towards the end of the piocen 
becomes impure : it contains azote, and should be re. 
jected. Or in place of nitre, the mercurial oxide, 
sold by druggists under the name of red precipUotti 
may be poured into the iron pipe and heated. Thil 
a more expensive method; to furnish 113 cutne 
/aches of oxygen, a. troy ounce of red precipitate most 
lie ujied. Whea of ordinary ijurit^, t\vw o-siie o»vuaia 



flilAF.I. OXTOBN. 137 

BO nitric aoid^ and therefore will not afford any compound 
of azote : if any be feared^ the first bubbles will contain 
it all. Mercury^ in its purest state, distils over with 
liie oxygen; and it may be of use for thermometers and 
barometers, or for experiments. The red precipitate^ 
heated I dry in the oil flask- over a charcoal fire, will 
foniish oxygen also ; but the heat must be barely 
sufficient, or it will melt the flask. In this case the 
neck must be wound with annealed thin iron wire, not 
with cord : the glass tube must fit in without the inter, 
vention of cork, and the juncture must be rendered air- 
tight by cementing it round with a soft adhesive sub« 
stance called a ItUe. The lute, which answers in this 
ttd almost every other case, is very finely powdered 
pipe-cUy ; not that which is made into white-balls ar« 
tifidally^ but the rough material as purchased from the 
dnggist. This powder should be mixed in a mortar, with 
ss much boiled linseed oil, otherwise called drying oil, 
ss will form a mass Uke putty used by glaziers. It must 
be pounded with a heavy pestle for a length of time, 
Airing which it will become much too firm ; more oil 
should then be added, and the pounding resumed. The 
oil must be added and the pounding continued, while the 
niass becomes hard in consequence. The lute is now 
made, and ought not to be applied in any case without 
wiping the parts to be joined perfectly dry: and the 
juncture should be made smooth and regular by rubbing 
it over with the finger. When the lute is intended to 
be kept for store, it should be pressed into a pot, and 
tied over with a wet double bladder. This kind of 
lute, for there are many others, is distinguished by the 
name o£/at lute. 

Some of the properties of oxygen gas have already 
been noticed ; the remainder will come in under future 
heads. When suddenly and violently compressed, 
it gives out heat and light. M. de Saissy says, that 
none of the gases but those that contain oxygen give 
out light ; and that itself gives out the most. CVAo- 
rioe, however, is known to emit light. It Vvas \>eeti 



I 



f tated by Mr. Hart {Brandf's Journal, xv. 6f>.), tliU tbt 

Itgllt which aomeCLnies appears at the muzzle of Ul nr- 
gun, wllen it is discharged, arises from altiition of (&■ 
cideiital sand nr hard substances adhering to the waditlng. 
He loaded an air-gun with bits of sugar, quartz, fluoi 
spar, file, and discharged them: light was produced; 
but not when care was taken to avoid such substaucet 
in the wadding. 



Hydrogen gas is a permanently elastic fluid, tnm- 
pareiit and colourless. It is exactly sixteen CitMl 
lighter llian oxygen : hence, dividing I'lOOT by 11^ 
we have 0'0688 for the specific gravity of hydrogBii*! 
100 cubic inches of it, therefore, weigh S'UyT p^M* 
It is between fourteen and fifteen times lighter thul at- 
mospheric air. The followiog is the process for obtaili- 
iugit: — 

A glass retort must be procured ; they are sold it 
all glass-houses and chemists' shops, although generally 
Tery iU-formed : the idiape is given in (he figure. It 



should be blown without any imperfection in the sulf- 
stance of the glass, such as tears or stones : it should be 
very thin iu all parts, but particularly in the bottom: 
for no glass vessel that is not thin will bear sudden heit. 
* nr.Thnmam IFiTil Pria i 71.). from careruHj MKUird HjmrlmeBU 

nodei It piWty cerlMia Uial tbenumliB ^icn \ii Uw u: 



IHAiP. I. HYDROGEN. 139 

vithoat cracking. The retort should he tubulated, that 
s, it must have a mouth at A^ either fitted with a 
sork or an air-tight ground glass stopper; the latter 
node is expensive^ and seldom necessary. A numher 
if small iron nails should he introduced through the 
nhulature one hy one^ cautiously^ to avoid hreaking the 
^ass. The nails should then to a good deal more than 
severed with water, and sulphuric acid ahout equal to 
the weight of the nails should he poured in. Ehul- 
lition commences in the retort, owing to the rapid 
formation of gas in the liquid, just as steam would 
appear in water while hoiling; and gas is expelled 
through the beak or long neck of the retort. The end 
of the heak should he plunged in water, and some of 
the gas allowed to escape, for it is mixed with the 
common air of the retort. The hydrogen gas may then 
he collected in bottles or hell glasses, filled with water 
in the manner already directed. When the gas begins 
to come over slowly, nearly the same quantity of sul- 
phuric acid may he added, which will renew the ebul- 
lition, and gas will continue to be discharged until all 
the iron is dissolved. Small pieces of zinc may be used 
in place of iron nails. 

This kind of ebullition is called by chemists effier^ 
vescence; the word merely means the extrication of 
wy permanently elastic gas in the form of air-bubbles. 
Hydrogen gas, as commonly obtained, has a disagree- 
able smell, somewhat resembling phosphorus : but it 
nay be so far purified as to be quite free from smell, 
ly being shaken in a bottle, with a little alcohol holding 
K)tash in solution, or with a very large quantity of 
^ater. It cannot be breathed for any length of time 
dthout occasioning death : a few cautious inspirations 
lay be taken, it is said, with no other effect than at. 
inuating the voice for a while. It is, however, a rash 
(periment. A frog lives for a long time in it. 
In consequence of the lightness of this gas, compared 
ith the atmosphere^ it will ascend when at Ubext'j , ^w^X. 
the same manner as a cork plunged by force to t\ie 



I 



liottom of a vessel of water would rise to| the fl 
if left to obey the law of specific gravity. 

If a pig's bltt'liier of large size be filled with hydS 
its outer coat may be peeled off bit by bit^ until thelfl 
becomeE specifically lighter than the air, ati^ 
will ascend in the manner of an air-balloon, 
lantois which itiTeata the ftptus of the cow, proi 
from any butcher, or the craw of a turkey, will | 
an ex(!ellene material for a hydrogen halloo 

If a burning taper be plunged into a jar of hyft^ 
ihe taper will be extinguished; yet hydrogen gaii* 
comhuatilde, although it will not support c 
The philrmijAi'Ml candle is a bottle fitted with k9 
through which passes a slender glass or metallis.jl 
The materials for generating hydrogen being j 
duced, the cork and' tube are fixed in air-tight^ 
drogen gas will be discharged abuudantly. Some A 
be allowed to pass olT, in order (o expel t; 
air present; for without this precaution an i 
Bion would happen on kindling the gas. The ajQ 
tion of a burning body, or an electric sparfc, e' 
most feeble, wUI set fire to this jet of hydro 
will bum slowly and quietly while the efFervescenttl 
continues. The flame shows almost no light, bnt iti I 
heat is intense. Let a fjinall thin bladder, squeeud I 



tight so as to expel the 
with hydrogen and one 
being tiefl, make a pin-hole 
the hole to the flame of a candle ; 
place as loud as a pistol shot, 



be filled two thirds I 

third wi'h oxygen : the orifice I 

the bladder, and applf I 

-»\ explosion will tjte | 

t the bladder will be , 



shattered, although the hand that holds will i 
jured. There will also be a vivid flash of light. I 
have seen a person incautiously explode a very large cn 
bladder filled with these gases, holding it close to hia 
side while the tube proceeding from it was applied 
to a candle : the explosion was equal to s musket ibo^ 
and he was thrown with violence against a wall whiidi 
ie stood near, but sustained no injOT-j, It should be 
L^ere observed, that espVosioua oi ftia ^ni, ia ■*»&, 



loise is coneiderahle, are called by chemists deloiut- 
(from detonare, to tliuniier). 
be combiistion is %o violent, that the result of it 
ot be ascertained by making the exiierimenl in thia 
111 a former chapter, the product was ehown Co 
ater. But by burning the philaeophical candle in 
ge balloon containing oxygen gas, a combiDaCion 
eeii the two gases lakes place in the fiame, and the 
ting water U instantly dispersed in steam through- 
hs balloon, and will condense on ita sides if it be 
eool ; the water will gradually trickle down, and will 
ly accumulate in the bottam. The method is al- 
ther unsatisfactory, and very Iroubleaorae. But 
<f purpose is as well answered by employing atmo- 
ric air instead of oxygen, and the following cheap 
iratns may he made by any tin-plate worker, 
et a tin-plate cylinder, A A, be made, open at the 
^ closed at the bottom, except where the small 




ytinder B, open at both ends, enters it, and is si 
i to it. Let another tin cylinder, C, close at the ti 
xed inside the cylinder A A, and soldered a\\ ioiio4 
iih two slanting pipes, A A, proceeding tcma * 



Azote, or nitrogen, is a permanently elastic gas, tiMi- 
parent, colourless, and inodorous. lis specific gravity il 
0-9748 •; and 100 cubic inches of it weigh 3O'03S5 
grains. 

A number of processea have been given in chemicd 
books for tlie preparation of azote, but they are tedioM 
or troublesome, or both. The following is a melhod 
which I have found to succeed : — Take a bottle capihle 
of containing a gallon (277^ cubic inches), and fit A 
cork accurately to it r throw into it 22 troy drachma rf 
the salt sold by dru^sts under the name of green co^ 
peras, or sulphate of iron, with half a pint of water; then 
pour as much water on 4j drachms of roche-lirae as wiB 
slake it ; and when slaked, throw it into the diseolved 
■ulpbate of iron. Cork the bottle perfectly close; and, 
having inverted it, immerie the neck in a vessel of wata 
to prevent the entrance of air. By agitating this mix- 
tare briskly during a few minutes, still keeping the DtA 
immersed, the whole of the oxygen present in the com. 
mon air, which the bottle had contained, will be ab- 
■orbed ; and, on removing the cork under water, a quan- 
tity of water will rush in, equal to the volume of osygen 
^hich had been removed. The air now remaining Id 
the bottle is pure azote ; its volume is 2S2 cubic inches 
and it may be transferred into any other vessel by fiUing 
that vessel with water, inverting it so that the month 
shall be in water, then getting the mouth of the bottle 
under the vessel, and turning the mouth upwards : vMB 
will enter, and azote will rise into the vessel. The 
quantity of sulphate of iron and lime here directed, ii 
just double what ^ould be required by calculation; but 
the process is thus hastened. 



UP.L JUOTS OB NITROOBH. 145 

[f a burning body be immersed in a jar of azote, it is 
tttin^shEd as instantaneouely as if plunged into water, 
No animal that breathes can live in azote ; and from 
tliii circumalanee is derived its name, which signifies 
Hf'-depriver. It is not combustible; it enters cKtensively 
into combination : it is an abumlant element in animal 
Batter; and its existence in Kuch larj^ (juftntity is ■ 
chief distinction between the constitution of animal and 
ratable matter. 

It has been already ehown that the atmosphere is 
empoted of oxygen and azote; in every 100 cubie 
ia^ of atmospheric air there are 20 of oxygen, and 
lOof uole: hence the oxygen is one fifth of the whole 
**danie of anj measure of common air. There is great 
dUerence of opinion as to whether these two gases are 
Berdy mixed together, or whether they are in a state 
rf chemical combination. Strong arguments have been 
■il'anced on both sides, and the question reniains yet 
unriecided. It la now no longer confined to the mere 
Motiiiution of the atmosphere, hut has extended to the 
institution of all mixed gases, 

Thoie who support the opinion that the two gases are 
cbemically combined in the atmosphere, found their 
belief upon facts like the following ; — The specific gra- 
vity of azote is leas than that of the atmosphere ; the 
specific gravity of oxygen gas is greater. Now, since a 
certain volume of oxygen is heavier than an equal vo- 
lame of azote, we should expect, that if in the atmo- 
gpbere they be merely mixed without the operation of 
affinity, the oxygen would at length subside to the earth, 
while the acote would fioat above it. Bnt we know that 
the fact is otherwise ; for air taken from the greatest 
elevations to which balloons ascend, affords the same 
relative quantities of the two gases. Atmospheric air is 
also of the same compOEilion in all parts of the world. 
This consideration appears to favour tlie opinion, that 
tetween the two gases some chemical attraction subsists: 
but there are also considerable objectiona to l\ii» tww 
the subject 



1 



I 



It msy be objected, that if the oxygen and note m 
dlUE combined, same of those chemical changes uugbl t" 
be observable which indicate combination, and nev yn- 
perties should be evolved. But none such ate diacoier- 
able ; for the specific gravity of common air is the mein 
of the specific gravities of oxygen and azote; and il» 
chief properties seem to be a mean of the propertiei of 
its component gaEes. 

A view of the subject has been proposed by Dr. Dai- 
ton, which is not liable to these difficulties, although nut 
free from objections of another kind. Dr. Daltun con- 
ceives that the repulsion which produces the elailidtj 
of the atmosphere, doe» not subsist between a 
oxygen, but between aiote and azoic, and between oxygen 
and oxygen. He conceives that, with regard to oiygeM, 
axote offera scarcely any resistance to the indefiiute ex- 
pansion of that gas ; and that oxygen does not renat Ac ' 
indefinite expansion of azote. In fact, he suppoBCB thU 
each acts as a vacuum to the other, and that whatever 
pressure a particle of oxygen at the earth s surface eiu- 
tsins, that pressure arises solely froro all the particles of 
oxygen above and around it, but none whatever &om 
those of the azote ; and, conversely, that a particle of 
azote at the earth's surface is pressed by all the other 
particles of azote in the atmosphere, but not at all by 
the oxygen. Each gas thus sustaining only its own 
weight, it would expand itself, regardless of the othv; 
both would press upon other bodies, but neither would 
subside according to its weight. And although, tt 
very great heights, there might be a difference of Ae 
relative proportions of the oxygen and azote, in conse- 
quence of the great total predominance of azote in the 
atmosphere, this could not be observed at such heighti 
as are within our reach. He conceives that the two gases 
■re not in any manner chemically combined. 

The most obvious objection to the hypothesis of Dal- 

toa is, that were il admitted, it should follow, that bjr 

eonnecting a glass globe ftl\cd'wU\iox'j^ew,!mAafte6Ued 

irith azote, by a stop-cock, the \\ea.V\eT i^i^.XicCTi^'a.xAHi- 



LP. I. AZOTE OR NITBOOEN. 147 

ih, the moment the communication is opened there 
old be an instantaneous mixture. Dr. Dalton made 
following experiment : — A pint phial filled with 
x)nic add^ and an ounce phial of common air^ were 
nected by a glass tube^ thirty inches long and one 
d of an inch bore^ so that bo^ phials were air-tight 
h regard to the external air^ and communicated with 
1 other through the tube. This apparatus stood ver- 
ily^ the common air phial being uppermost. In one 
r^ the common air phial had acquired no sensible 
ntity of carbonic acid gas ; but in three hours^ it had 
1 great plenty.* Dr. Dalton adduces this expierim^it, 
irove that the ascent of the air in the lower vessel is 

attributable to chemical affinity^ as none subsists 
^een the two gases ; and he infers that it favours 
hypothesis. It seems to be as much an evidence 
inst his hypothesis. If each gas acted as a vacuum to 
other^ there ought to be an instantaneous commix- 
3. But, to remove this obstacle, he says that the gases 
it with some mechanical obstruction, owing to their 
lute division, while passing each other in contrary 
actions. Is it conceivable, that such an obstruction 
Id exist to the transmission of two gases through a 
e one third of an inch diameter; and that, for the 
ce of an hour, there should not have passed even the 
illest quantity of the carbonic acid gas into a vacuum? 
is experiment seems quite fatal to the hypothesis. 

has adduced other experiments, made with the same 
d of apparatus, but using gases which are not known 
tiave any direct affinity for each other ; such as car- 
lic acid gas and hydrogen. In the mixture which 
k place of these two gases with each other. Dr. Dalton 
iceives that affinity cannot be supposed to be con- 
ned, as they are not known to have any affinity. That 
tclusion may, however, be questioned. It may be very 
e that carbonic acid and hydrogen do not manifest 
f affinity for each other in their gaseous state ; but 
is quite certsdn that the three elements conceti^ft^— 

• Mmcbeater Memoirs, Second Series, i. «61, 

I. 2 



■ 148 BLGMKNTS or CBlMlBtKT- ■ MJVIb 

■ carbon, oxvgcn, snd hydrogen "— have, collectively, a 
I powerful affinity for each other, and constitute the basis 
I of vegetable organised matter. The obetacle to the sue- 
I cessful exertion of their affinity, is the elastir farm: but > 
I partially successful exertion may be conceived to operate 
I 10 far, that the solid dements would be retained at the 
I limits between calorifiuteiiulGian and chemical attraction; 
I the latter force bting active in a slight degree, but not 
I sufficiently to to effect a combination. As to dmilar 
I examples, drawn from other gases which are not knows 
I to possess affinity for each otlier, it may be replied, that 
I we can scarcely view affinity in any odier light than a> 
I K general property of matter. When bodies do not obey 
I the tendency of their affinity, it is because counteracting 
I igencies are in more powerful operation. We have an 
I example of affinity, the efficacy of which is partially 
I resisted, in the case of charcoal, which absorbs many 
I times its own volume of various ^ases, and gives than 
I out again by being placed in water, or in a vacuum. If 
I these gases permeate and diffuse themselves in a tolid, 
I for which lliey do not possess any affinity more than one 
I kind of matter does for every other, and without com- 
I Inning, why may not one gas difiuse itself in another 

■ ^as to which it has no more than their general affinity, 

■ in the same manner, without entering into an energetic 
I combination, and yet without separating by difference of 
I Specific gravity ? That oxygen is absorbed by charcoal, 
P by an affinity inoperative so far that it does not produce 

■ carbonic acid, is proved by llie fact, that after a loi^ 
lapse of time this acid gas is really formed, although not 
at first. 

Dr. Dalton conceives that his hypothesis receives 
support from the facility with which it explains the 
various cireimstances of the existence of aqueous va> 
pour in the atmosphere and other gases, and the 
difficulty of accommodating the chemical hypothesis of 
its solution in these gases. His aj^ments are the 
/bl/awing : ^ DiSereat gases are found V> can\.am the 
eaiue quantity of watery vapour, die tolurotsXicKv^iSift - 



OBAP.I. AZOTE OR NITROGEN. 149 

the density of the gas makes no difference ; for whether 
it be rare or otherwise^ the quantity of vapour is the 
fame : the same quantity of vapour would he present 
in the same space^ even if the gas were entirely removed^ 
and the space were left a Torricellian vacuum. Dr. 
Dalton suggests^ that hy supposing the vapour of water 
to exist independently of any attraction to the gas^ and 
under no other control than its own weighty the phe- 
nomena are disembarrassed of the foregoing difficulties. 
But it may be observed^ that it has never been proved 
that different gases contain the same quantity of vapour in 
equal volumes : the experiments of Saussure^ Clement^ 
and Desormes^ merely prove that different gases impart 
the same quantity of water to other substances ; but 
this may depend on the power of these substances to 
abstract water^ and the power of the gases to resist such 
abstraction. Hence^ until the facts be better proved^ 
there is no occasion to seek any explanation of them ; 
and^ if the above reasoning be correct^ one of the found- 
ations on which the hypothesis rests is removed. The 
following considerations seem adverse to Dr. Dalton's 
opinions^ and favourable to the chemical hypothesis ; — 
If vapour maintains an independent existence in a va- 
cuum or in air, being neither attracted nor repelled by 
the aerial particles, it follows that rarefying or condens- 
ing the air should make no difference in the quantity of 
vapour; as is, indeed, affirmed by Dr. Dalton himself to 
be the case. But Saussure found his hygrometer to indi- 
cate '^ dryness in the air which was rarefied, and humidity 
in that which was condensed *;" and hence he concluded, 
that '' rarefied air dissolves less vapour than when it is 
dense." f It is even a well known fact, that when the 
air in a large receiver of an air-pump is suddenly rare- 
fied by a few strokes of the pistons, vapour is actually 
seen falling down in mist; and this can scarcely be 
attributed to reduction of temperature, for Dr. CuUen 
found that a thermometer included in the receivet CeU. 
hat two or three degrees. Such was the effecX. oi \k<& 

*EisaJ38url'Hygr6m6trie, Neuchatel, 1783, p. 1S3. t WiV^u ^. SL^a. 

J. 3 



heat that disappeared, no matter how great ils quality 
might have been. 

If air does not dissolve water, or exert anj afBnitjron 
it, as is Bupposed in the hy|)oihesiB of DaJton, how 
doe* it happen that the evaporation of water is greatly 
proraoted by passing a current of air over its surface ? 
If vapour be elevated from water merely by its own 
volatility, the passage of air over it should have no 
~ ct ; or if any, it ahould be a counteracting one, when- 
r the air is colder than the water, by depriving it of 
le of that heat which is the means of elevating it into 
Tapour. Many other arguments, of tlie same tendency, 
could be ttdiluml, if space permitted. 

On the other hand, it must be admitted, that the 

[ affinity of air f^r watery vapour cannot be the sole 

agency exerted in the solution. The fact that vapour 

I pervades a Torricellian vacuum, seems to decide this 

I point. I am inclined to think, that the agency of bodi 

I beat and affinity is necessary to the explanation of the 

' phenomena. The increased solubility of water in air, 

I in proportion as the latter is warmer, may be explained 

by increase of the intensity of aliimly ; for heat is known 

in many cases to exalt its force. 

Aa to the argument that Btmospberic air is equal in 
volume to the sum of the volumes of the two gases which 
compose it, and that it possesses properties merely inter- 
mediate between those of its elements, although a certain 
change in them ought to result, if chemical combinatioD 
had taken place between them ; it may be replied, that 
aa tlie affinity in effective operation is exceedingly weak, 
■0 much so as to be overcome by almost any other 
affinity, the change of properties should be proportion- 
ately trivial. There is an undoubted chemical compound 
of the same elements, in which the volume of the ele- 
menta does not alter on entering into combination, viz. 
deutoKide of azote : and with regard t« changes, there 
are unquestionably some observable, which are usually 
attributed to dilution, but ■Brtiic\\ ma's fl«^\\i ^ttiTj on 
« weak affinity ; and these are at \eM.t aa aCn!Kio% a* ftut 



chiQgea which take pli 
although in thi; 
■appose that affiDity is in operation. 

In fine, as we know of no two bodies which we can 
»ffinn do not possess any sffinity for each uther, and as 
ibere is reason Co belitvo that tliis kind of attraction ia 
)>niuch a general property of matter as gravitation, I 
duit we are not under die necessity of seeking the 
esplanation of the mixture of gases on a gratuitoos 
J principle, which supposes the caloric that ej ' 
surrounds two particles of difierent kinds of 
"m i^aseous state to obey a. law diametrically the reverse 
ti what we know would act upon them, if they 
(he liquid or 8oli<i state, 
, We have now to consider those substances which aig 

ompoeed of azote and oxygen, and in which the ele<- 
mats afe universally admitted to be chemically 
lUied ; there are five such ; two oxides, and tliree acide.. 
Protoxide of azote. — It was stated at page 113. that 
litric add and ammonia, when combined, form a cryEtaL 
litiesjdt, called nitrate of ammonia. If a quantity of thin 
nit be introduced into a retort, and heat gradually ap- 
plied, the salt will melt, boil up, and dischai^e a gas, which 
ii to be collected in the manner described at page ISS. 
Thisgju is a iximpound of azote and oxygen ; it was for- 
merly called nitrous oxide and gaseous oxide of azote, and 
Wat discovered by Dr. Priestley. It has a sweetish taste- 
Water absorbs three fourths of its volume of it, It ia 
traasparent and colourless. At the pressure of the aC- 
iHosphere it is a gaa ; hut when compressed, by a force 
equal to about 50 atmospheres, it is condensed, and be~ 
comes an exceedingly volatile liquid, which, however, ex- 
pands again with violence when the ]iressure is removed. 
It consists of lOOmeasuresof oxygen combined with 200 
of azote, both condensed into the volume of 200 mea- 
sures. Its Epeciflc gravity ia, therefore, 1'5252; fill 
twice the specific gravity of azote, 1 '0497, added 
specific gravity of oxygen, M007, anil diviieA 
^res 1-S252. Dr. Tbomson ascertiuned. b^ ftnee eKj 
i. 4 



I 



rinienta, which ngreed.thiil the specific gravity is 1-5269; 

sufficiently striking correspondence. 100 culoe 
inches weigh i^'Qi)3l grains. ComhuslibieB bun 
in this gas : a candle bums In It with less brilUuiCT 
than in oxygen, but greater than in common air; itit 
length becomes surrounded with a bluish lialo : sulphur, 
phosphorus, and chareoal, require to he well kindled be- 
fore they are introduced into it, otherwise they do not 
bum ; and an iron wire burns in it as it does in oxygoi, 
but for a sliorter time. ' 

The most remarkable property of this gas is its eSecl 
upon animal life when breathed. If an oiled silk big 
containing it, and furnished with a tube to hold inlhe 
mouth, be so arranged that a person can draw the gu 
into his lungs, and breathe it hack and forward a few 
times, it will produce extraordinary sensations of 1 
highly pleasurable kind, accompanied by an iacretsed 
■ vividness of ideas, propensity lo muscular exertion, inft" 
luntary laughter, and the greatest exhilaration, wilhoal 
the subsequent languor and depresBion that foUs* 
ebriety. Sometimes, liowever, in peculiar constitutiDUi 
we find the only effect, in the first instance, to be a sens- 
ation like the approach of fainting. In one inKtanc^ I 
saw it produce effects resembling apoplexy ; but n* 
injury was sustained. It is probable that this gas mSf 
yet be found of nse in medicine. 

DMiiftrideqfoeo/e. — The second compound of o«y* 
gen and azote was formerly called nitrons gas; but, in 
conformity with the principles of nomenclature ahvadj 
explained, it is at present named dentoxide of azote' 
like the former compound, it is a gas. Protoxide 9 
azote requires 50 measures of oxygen tolOO azote: bat 
in order to form this deutoxide, 100 measures of iicK 
combine with 100 of oxygen, that is, twice the bulk rf 
oxygen contained in the ]irotoxide : these equal meaaurei 



of the two gases unite without condensation, and there* 
fore form 200 measures. 

This gas may be obtained 'b^ iwtin^ \ktce ^aita of 
m eoncenlrated nitric acidwidi lour oi ■««■ 



EAP.I. AXOTE OR NITBOOBN. 153 

ore, and pouring the mixture on copper wire cut into 
dt8^ and contained in a glass retort^ the heak of which 
I plunged in water : red fumes and an effervescence 
ppearin the retort; and when the former disappear^ the 
;a8 may be collected in bottles or jars^ as already de- 
mbed. This gas is very little heavier than common 
ir, 100 cubic inches weighing only 31*975. As it is 
imposed of equal measures of oxygen and azote^ with- 
nt condensation^ it is easy to see that its specific gravity 
nnstbe the arithmetical mean. Oxygen is 1*1007^ and 
^te is 0*9748 ; the arithmetical mean 1*0377; and 
bis is the specific gravity required. 

If alighted candle be immersed in deutoxide ofazote^ 
t is immediately extinguished ; it also destroys animal 
ife. Like the protoxide^ it continues the combustion 
if charcoal and phosphorus^ when these bodies are in- 
nxluced already burning. This gas has not been li« 
[uefied by pressure. 

Its most remarkable property is its effect on oxygen 
lis, whether pure^ or as it exists in the atmosphere, 
i^en these two gases are mixed^ they instantly assume 

deep red, or orange brown colour. If 100 measures 
f oxygen, and 200 of -^ieutoxide of azote, be mixed, 
^ change of colour takes place, and the whole is sud- 
enly condensed to 100. The resulting compound is 
idled nitrous acid vapour, and is next to be described. 

Nitrous acid. — The above mentioned vapour, when 
ifficiently cooled, is condensed into a liquid called ni- 
ous acid. ■ In the 200 measures of deutoxide of azote 
nployed, there are 100 of oxygen, and 100 of azote : the 
)0 of oxygen added to the 100 with which the deut- 
dde had been mixed in the experiment, give the com- 
»sition of nitrous acid as follows : — 200 measures of 
ygen combined with 100 of azote, that is, four times 
e quantity of oxygen contained in the protoxide. The 
10 measures condense into 100 of nitrous acid vapour, 
into a liquid, if the temperature be low. This liquid 
very different from what is called nitrous acid \tv eoici- 
rce. The real nitrous acid is very volatile ; it \Joi\a «.t 



I 



Ite Epecific gravity is 1'4^I : it contains no wata, 
for it may be formed from gases which are perfectly dij. 
IthaeapowerfulafGnity for water : water added, dungM 
its colour to orange, yellow, or green, according to ifac 
ratio; much water resolves it into deutoxide of uote,. 
which escapes, and nitric acid, which will preaentlj be 
described. 

Byponitrous acid is bo named, from its conlaining t 
quantity of oxygen less than what exists in nitrous kA 
last described {ita, under). If 100 meaBUres of oxygen be 
mixed with 400 of deutoxide of azote, and the mixtnre 
is then exposed to intense cold, the whole condensesinB 
a green hquid. The volatility is such, that it can ooly 
retain the liquid form at very low temperatures. This u 
hyponitrous acid : its composition is obvious, from wtaU 
has been stated above; for as there are 200 measuM 
of oxygen in the iOO of deutoxide employed, and 100 
meHEures of oxygen were added, 300 measures of my' . 
gen^ combine with the 300 meaeurea of azote, fiMAi 
canstiCuted the remainder of the deutoxide of sutb I 
This is three limes as much oxygen as exists in the prat' ' 
oxide. HyponitrouB acid is decomposed by water: ytt. 
if sulphuric acid be present, the three bodies ent4ar intS 
combination, and we obtain a compound, consisting « 
hyponitrous acid, sulphuric acid, and water, in the fom 
ofa crystalline sohd. 

Nitric acid. — There is but one more combination (rf 
azote with oxygen ; in forming it the azote is satursUd) 
and does not manifest any further affinity for that gu- 
It cannot be produced unless water be present, andili* 
known to chemists only as containing it. If 100 Mbio 
indies of oxygen and 133^ of deutoxide of azote h 
mixed, water being present, the two gases are complete^ 
condensed, and the resulting compound is called nt'Mt 
add. Of the ISS^ cubic inches of deutoxide of azot^ 
one half (66j) consists of oxygen, which, added lo dK 
lOOof oxygen, affords Kiflj culnc inches: and the otha 
I half (66^) is azote. Hence, as QQ% of azote require 
l^fi?^, bj- theruleof piopotdonlOQo^aiowm'iiTM^ 



WUP.'im AIOTE OB NITBO«EN. 155 

S50 cubic inches of oxygen ; and this^ accordingly^ is the 
atio of the two elements in nitric acid. 

Nitric acid^ composed of the same elements combined 
IB die same proportion^ may be obtained by exposing a 
nixtore of nitre^ rendered perfectly pure by' repeated 
nations and crystallisations^ with an equal weight 
of the strongest sulphuric acid^ to a moderate heat in a 
fiuA retort : the acid will distil over into the neck^ and 



tiidde down into the glass receiver A^ provided that the 
long neck of the latter be kept cool by constant sponging 
^^ cold water. This acid contains about one fourth of 
Its weight of water^ derived from the sulphuric acid. If 
the nitre had been rendered perfectly pure by repeated 
Nidations and crystallisations, and the heat was exceed, 
iogly moderate, the acid produced will be almost colour, 
bs: but if it contained common culinary salt, as that of 
commerce always does, the acid will be somewhat yel- 
Wish, on account of a little muriatic acid, which cu- 
linary salt gives origin to, and which decomposes some 
nitric acid. Common nitric acid is orange coloured on 
this and two other accounts. Pure nitric acid cannot 
Crist without a certain ratio of water present in it. 
Unless the sulphuric acid be employed in sufficient 
quantity to afford that ratio of water, a part of the nitric 
tcid will be spontaneously decomposed ; the result being 
oxygen, deutoxide of azote, and nitrous acid, and the 
colour will, consequently, be orange. The process recom- 
mended by Mitscherlich as affording the best produce, 
ind occasioning the least waste of acid, trouble, and 
M, is to distil a mixture of 100 parts of nitre, 9^*8 
)f sulphuric acidj and 40'45 of water. TYie lesvAl- 
^nitric add will weigh 135 pounds, and its ai^eci^t 



150 XLKMKim (W CBBHOTBT. SUlil 

gravity will be 1-3. The third reason for the yeUoW 
ness of common nitric iidJ is, because it is not alwi] 
protected from the agency of light ; this has the efib 
of partially decomposing it, and generating osygen,irbk 
exhales, and nitrous add, which imparts the colour. 1 
render orange or brown nitric acid colourless, introdu 
it into a retort; apply a long necked receiver b« befia 
and espoae it to heat : the brown part will rise in vapix) 
and be condensed in the neck. What remains in tl 
retort is colourless nitric add ; the nitrous acid is fini 
in the receiver. 

The specific gravity of the strongest procurable nill 
add is 1-55, and then it contains exactly one seventh 
its weight of water; that of commerce is about Vii 
and contains two fifths of its weight of water. Niti 
add has very opposite effects on water, with regard 
tile production of heat. If dilated with half its we^ 
of water, heat is evolved : but if the water be in t 
Btate of snow, intense cold is the result. If nitric SI 
be poured round the rim of a saucer, on which lio 
quantity of warm, dry charcoal powder, the latter Ul 
fire, and throws up copious showers of brilliant epid 
the acid must be strong and a little warm ; and the du 
coal should be newly made and finely powdered. 1 
piece of ignited charcoal be laid on strong nitric ic 
the charcoal burns with intense vividness. 1 have fbl 
that cantharides, perfectly dry and warm, are set on fl 
if thrown on very strong warm nitric acid, contained 
a glass flask. About a tea-spoonful of nitric acid, o 
tained in a phial and tied to a long stick, will, if pm 
on the same quantity of oil of turpentine, cause it 
burst out into a fiame with some force. If poured 
phosphorus, it causes it to burn. 

When exposed to 66° below melting ice, it treet 
at 248° it boils, if its specific gravity be 1-420: il 
be stronger or a little weaker than this, it boilt I 
lower temperature: thus, acid of specific gravity 1 
and of i-!ii both boll at ^40°. I^^Wyc wiA ibu 
moistme iioia the atmoB^beie, \i einfcftea. \o '■»., 



'. Z. OARBON* 157 



It will now be luefiil to bring together the chief facts 
■pMaikd relating to the combinations of azote and oxygen. 
jf( atmospheric air be denied a place amongst the real 
fgimfainations of these two gases^ the five combinations 
WU stand thus: — 

Protoxide consists of 100 azote and 50 oxygen or 2 to 1. 
Beutoxide - - 100 - 100 - 2 to 2. 
. Hyponitrous add 100 - 150 - 2 to 3. 
Kltrous acid - 100 - 200 - 2 to 4. 
Kitricacid - 100 - 250 - 2 to 5. 

'^%e numbers in all cases representing cubic inches or 
Wty other volume. 

Sbctiok IV. 

CARBON. 

It has been already shown that charcoal is the sub. 
Unoe which remains when wood or any vegetable sub- 
Knee is exposed to a red heat in close vessels. The 
Im charcoal for chemical purposes is made by covering 
t piece of box- wood in a crucible with sand^ and expos- 
ing it to an intense heat for some time after all flame has 
ceaiedon the surface of the sand. When cool^ the char- 
tml is to be taken out, and included in well.closed hot- 
ties. * If made at a red heat, charcoal is a conductor of 
tleetricity, and burns without flame : if made at a heat 
lidow redness^ it is a non-conductor, and blazes a little 
ti burning. 

When charcoal is set on fire, it bums away, and leaves 
Uiind a small quantity of ashes, which consist of alkali, 
WbB, salts, and metaUic oxides. These are impurities, 
nd should be considered as quite foreign to the red 
imtter of charcoal. In the same light we should view a 
^ery small quantity of hydrogen which the best burned 
charcoal contains. The real matter of charcoal is what 
(honists understand by the word carbon ; and it is this 
0% which IB to he considered as identical wit\i \\ie 
dtmoDd (seep. 128,). 



Charcoal recently made, perfectly dry, and still wj 
has the remarkable property of slowly Bbsorhing giM 
very large quantities, — in some cases 90 tiine» ita 
Tolame, — and giving them oat again unalteted « 
immersed in water, especially if boiling. 

It is probably a result of this property,'that itaci 
powerfully as sn antiseptic, and removes the tui 
meat that is in progress of jiutretac^on. The am 
mode of using it,^however, for this purpose, is nil 
ineffircttve. The meat to be recovered should be 
washed estrcmely well seveial times in cold watM 
should then be covered with cold water in large quan 
and several small pieces of charcoal, red-hot, shoul 
thrown into the water when somewhat hot: the bx 
must be continued as long as the meat requires it. . 
haps it is on the same account that charcoal miDi 
divided forms a dentifrice so useful in certain c 
What is sold in boxes can have nothing to recomn 
it but its grittiness, if this be really a recommendal 
to correct fetor, it should be powdered with the tiD 
despatch in a very hot metallic mortar, and speedil] 
troduced into a pliial, which should immediately be 
corked, and even sealed. When this powder is usei 
ought to be exposed to the air as short a time as povi 
It is a common practice to char the inside of water a 
in order to keep the water sweet, for charcoal awee 
putrid water; and to scorch the ends of timber iniei 
to remain in the ground, to. prevent its putrefaci 
The bitterness of particular vegetables is destroyec 
boiling with charcoal, whether animal or v^;etable. C 
coal absorbs watery vapour from the atmosphere; 
probably does so, and retains it, in the same maniter 
according to the same principle that it retains gi 
There are several cases on record of the spontau 
ignition of charcoal, both dry and moist, the cau 
which has never been ascertained. 

The most intense ordinary heats with which we 
acquain^d, have no effect u^ou c\iwcn«!l, e^oe^t to 



QBAP. I. OABBON. 159 

dff it harder^ denser^ and more sonoroas*; that is^ if 
M other sabstance is allowed to act along with the heat : 
'^ heat excited by a powerful galvanic apparatus acts 
i^on it in such a manner us to render it probable that 
ihe charcoal had been both fused and volatilised ; but 
the fact seems not clearly established. 

It possesses the useful property of depriving various 
Squids of their colour^ and any peculiar or disagreeable 
imdl which they may possess. A long account of ex- 
ffriinents on its powers in this respect^ by Lowitz^ may 
k seen in Crell's Chemical Journal, vol. ii. He recom- 
BKDds vegetable charcoal well burned and finely pow- 
dered ; but it has since been found that charcoal obtained 
fiom animal substances is far more powerful. 

Carbonic acid. — ^\Fhen charcoal is burned in oxygen, 
iotense heat and light are produced: if a bit of the bark 
of charcoal be fixed to a copper wire, and immersed in 
i state of ignition in a vessel of oxygen, it throws out 
die most beautiful and brilliant scintillations, which fill 
die vessel in all parts. During this combustion, the 
oxygen and carbon combine, and the result is carbonic 
tdd. There is no change of volume during the com- 
bostion, except a temporary expansion owing to the 
Iieat ; we may, therefore, calculate the quantity of car- 
bon which has combined, by deducting the specific gra. 
»ity of carbonic, acid from that of oxygen : — 100 cubic 
indies of oxygen weigh 33*9153 grains; 100 cubic 
inches of carbonic acid weigh 46*5973 — (Thonisori) : 
Ae difference, 12 '682, is, consequently, the weight of 
onrbon that combines with 100 cubic inches of oxygen, 
and that exists in 100 cubic inches of carbonic acid. 
Then, as 30-8115, the weight of 100 cubic inches of 
common airf, is to 46*5973, the weight of 100 cubic 
inches of carbonic acid, so would the number 1*000, or 
onity, be to the number 1*5123, which expresses the 
specific gravity of carbonic acid. 

* Although it never has been volatilised, the term catbon vapour \& VAcdi 
l)y chemists: it will be hereafter expiajnea. 
/ See note, page 134. 



Carbonic acid extinguishes fiame : tliis can 1 
ing); shown by letting down a burning taperJ 
botlom of 3 gla«fi jar ; filling a bottle with c 
acid, and pouring it, as if it were water, into the ju: 
the flame is immedialelj extinguiahe<l. It is equtUj 
fatal to life as to flame. The Grotlo del Cane, or ie 
Dog's Grotto, in Italy, is well known ; it is an artifidil 
cave, in whii^h there is a constant natnral exhalation of 
carbonic acid. The following feat is shoH-n to siriii- 
gera:'ra man carries in a dog, and places him on die 
floor : the dog, If left long enongh, dies ; but the mm ii 
not affi^ted j for the carbonic acid, fay its weight, ocoi- 
pieB the lowest atratuni of about 1 8 inches' dep^, and tlu 
stratum above is pure air : but that it is poisonom to 
man is evinced by the fate of persons who 'incaalioDd; 
expose themselves to the vapours of charcoal burning in 
ill.Tenlilated apartments, or who venture into large •nt- 
eels in which fermentation had been conducted, as is 
breweries, distilleries. Sec. 

In order to generate carbonic acid, it is not otcB- 
Bary to bum charcoal in oxygen gas. Common lime- 
atone, marble, chalk, &c, are all compounds of Sw 
with carbonic acid, and the latter may be detached tm 
the lime in all cases by pouring on an acid having 1 
greater affinity for the lime than the carbonic add hit: 
a mixture of oil of vitriol and water succeeils ; but mu- 
riatic acid is more convenient. Bits of chalk, or 1(13 
better, marble, may be gently let fall into a tubulated re- 
tort, and diluted muriatic acid may be poured in, so II 
to half fill the retort ; the gas may be collected in the 
manner already deEieril)ed, except that water will notte 
proper for. the pneumatic trough and vessels, as it wooli 
absorb the gas ; in this case, mercury must be a«i 
instead of water. 

In oriler to prove that this gas is an acid, the beak nf 
the retort, in which it is generating, may be immerBCd 
in a jihial battle, containing an infusion of blue cabbage; 
a/ier a /itlle of the gaa has \>eew s.^isn'oei, \.\ve infusion 
jfiZ/ change gradually to red ■. DT,\i 



OBAF. I. CARBON. , l6l 

liter for the infusion^ the lime and carbonic acid will 
unite, and form the original chalk which was put into 
the retort, and which consists of these two ingredients ; 
the chalk thus regenerated floats through the water, and 
raiders it turbid. This is one of the characteristic pro- 
perties of carbonic acid ; and it may thus be detected in, 
or removed from, gaseous mixtures in which it exists. 

Water absorbs about Its own bulk of carbonic acid 
spontaneously ; but much more may be forced into it by 
using mechanical pressure, as that of a condensing syringe 
or a powerful force-pump. The water, by this treatment, 
acquires the property of effervescing violently when 
poured out ; it has a brisk, agreeable, acerb taste ; and^ 
tlthoQgh in other respects an acid, is not sour. If a little 
wda had been dissolved in the water previously to its 
impregnation, the result is the beverage called soda water. 
It is carbonic acid which imparts the effervescing quality 
to cider, perry, ales, porter, and sparkling wines ; and 
it is the same that renders bread spongy. This acid gas 
i« expelled from water containing it, either by boiling or 
freezing. By exceedingly powerful pressure the gas is 
condensed into a liquid ; but when the pressure is sud. 
toy removed, it recovers the elastic form with an ex- 
ploBion. It constitutes about ToViy^^ of the weight ot 
•tmospheric air at the surface of the earth ; and is also 
found at the greatest elevation. It constitutes an ingre- 
^ent in many minerals and mineral waters. 

The diamond, by being intensely heated with a burn- 
ing lens in oxygen gas, burns with a bright red light, 
*nd converts the oxygen into pure carbonic acid gas, just 
ts charcoal does. Carbonic acid gas is, therefore, to be 
considered as a solution of diamond in oxygen gas, even 
when it is prepared by the combustion of mere char- 
coal. 

Carbonic oxide, — When carbon is burned in oxygen, 
the oxygen is by no means saturated with carbon, as is 
proved by the following experiment: — TakealongeaitYvetv 
tob^ GUed with bits of charcoal, and place it acto%^ ^ 
^nace, so that it will be heated red-hot almost thtou^ 

M 



163 

its whole length. To one end connect a bladder, hiK 
-filled with carbonic acid ; and, to the other end, a flucid 
Wadder, of the same capacity, squeezed quite emplj- 
When tlie charcoal is perfectty red-liot, press ihe of- 
bonic acid very slowly through the tube, so that it diiil 
pass through the red-hot charcoal into the empty 1^- 
^er ; and pasa it back and forward several times in Ac 
same manner. All the projwrties of the carbonic soil 
■will now be changed : it will be lighter ; it will be com- 
bustible, and bum with a blue flame; it will be no lon^ 
SCid ; it wilt not be absorbable by lime water; anditsblllt 
will be exactly doubled. Thenewgas is called cnriowf 
ewide. Were this experiment made with erery attention » 
■ccuwtey, it would he found that 100 cubic inches of <«- 
Iwnic acid, weighing 46'5973 grains, are converted iito 
fiOO cubic inches of carbonic oxide, the weight of whiA 
IS £9'279^ grains ; beit\g an increase of 1S-6S3 grainii 
which is the additional quantity of carbon taken up in 
the process, and just equal to the quantity of carbon ihit 
existed originally in the carbonic acid. Hence lOO 
cubic inches of carbonic oxide consist of 12-68S graiu 
of carbon and 50 cubic inches of oxygen, wei^ 
ing I6'y576 grains; the whole weighing 29^996 
grains : and the quantity of carbon is double what exiiS 
in carbonic acid, consistently with the law of multiple 
ratio. Ab 100 cubic inches weigh 29"6936 gnjw 
(conmion air being SO'Sll.^ grains), its specific gravilj 
must be 0-962. 

Carbonic oxide easily takes fire ; it bums with 1 
sulphur blue fiame, and generates but very little best 
while burning. The result of the combustion is carbonic 
acid ; to become which, it is evident, from what has been 
slready explained, that the carbonic oxide must comlniK 
with half its volume of oxygen, and that the carbonic 
acid BO formed will condense into the original bulk of 
the carbonic oxide. Although it so readily takes fire, 
it extinguishes the flame of burning bodies when they 
Mre immeTSEil in it. 

This gaa, if inspired, acts m a. -eavMs^- ^« "a-'ftwf\ 



OBAP. I, €ARBON. • l6S 

"took, three inspirations of it^ mixed with ahout one 
fiwirth of common air : the effect was a temporary loss 
of sensation." The case of Mr. Witter has been re- 
corded by himself {Phil, Mag, xliii. 368.) : he made 
** three or four hearty inspirations of the gas^ having 
first exhausted the lungs of common air as much as 
possible. The effects were an inconceivably sudden 
deprivation of sense and volition. I fell (he says) su- 
pine and motionless on the floor." This happened in 
the laboratory of the Royal Dublin Society, in my 
presence. Immediately after the occurrence, while he 
l&y on the floor, his breathing was stertorous, his face 
purple ; and in this state he continued for half an hour. 
The late Dr. Wa^e chanced to be present ; he directed 
oxygen to be forced into the lungs : but it did not appear 
to me that his recovery was attributable to this. 

In order to prepare carbonic oxide, there is no occasion 
to have recourse to the process given above; the follow- 
ing seems the best : — Throw about 20 ounces of whit- 
ing into a wide metal pot, placed on a moderate fire. 
The damp of the whiting will soon begin to exhale ; 
and the process of its expulsion will be exceedingly 
tedious, unless the matter be continually stirred with 
a pestle, in order that the little masses, constantly 
forming, may be broken down. It will be known to 
be dry, when these masses no longer form, and the 
whiting is a discrete light powder. Of this an avoir- 
dupois pound should be returned into the metal pot, with 
a pound of tolerably bright iron filings, and the mixing 
over the fire resumed, so that the filings may be perfectly 
dried, and the whole well mixed. The reason of 
guarding so much against water is, that it would furnish 
hydrogen by its decomposition by the iron. The mixture 
should next be introduced into a cast-iron bottle, such 
as that described at page 134*. ; the whole of it will 
exactly fill a bottle capable of holding 1|- pint of wine 
gallon measure ^ 36 cubic inches. The Itoh tvxbe lowsx 
then he Btted into the bottle, and the 'bot^e >)ed<\edL Vgl 
: strong coal Bre, urged continually by beWoTia, VL \\ 

M 2 



I 



' 164 

be in a common grate. All the vessels empSoyed sllDnld 
be filled with water, whitened by lime, in order thai iny 
carbonic acid given over in the jirocess may be absoibed, 
ind thus reraoveil. By cskuktion, on pure matiriili 
Hid perfect deconipoailion, the product should be 6609 
cubic inches of carbonic oxide : but it will be a succeGtAil 
proceEs, if it he 3^ cubic feeL In this process, the imti 
robs the carbonic acid (of the whiting, for it is meiely 
carbonate of lime) of half its oxygen, and thus convert! 
it uito carbonic oxide. The mixture of the two id- 
gredients should be very intimate, to avoid ihe evolution 
of unaltered carbonic acid ; the great excesa of iton 
naed Iiaa the same tendency. Tlie lieat used for drying 
the whiting should not be so great as to espei uy 
oarbonic acid. 

Carbonic oside is not known to be susceptible of beiDj! 
. condensed, by pressure, into a liquid. When mixed 
frith twice its volume of air, the electric spark is capabto 
of causing It to explode feebly. Red-hot iron or charcMl 
Is required to set fire to it; although hydrogen, whiol 
produccE so much more heat in burninK, kindlei from 
■charcoal heated so as to be barely visible — (ZPoey)- 
At a red heal, carbonic oxide is decomposed by hydiogeD- 
It possesses no acid properties, and is not absorbable bf 

Besides carbonic add, carbon and oxygen form anolhef 

\ icid, called oxalic, which wilt be hereafter described. 

There are many combinations of carbon with hydn^eOt 

■iid Tnnch uncertainty prevails with regard to theif 

1 number and nature : they are all designated by tli« 

I Bame hydrocarbons, or, more properly, Uydrocarhtirets. 

Marsh gaa, or fire-damp. — The gas which bubblel 

fi-om the bottom of stagnant pools, is the same as tiilt 

which issues from the fissures of a coal mine: it is R 

carburetted hydrogen ; at least nine tenths of its bulk 

■re so ; the other tenth being carbonic acid and common 

air. in the former case, it originates from the decompo- 

tStioa of vegetable matter contMtieA \ft X\\e -waXM , boA «an- 

Jiot be imitated by art. Il haaamoal'iAsasicc^Ntwa^ 



CaSAP. I« CARBON. l6S 

which, however, does not depend upon it^ but upon foreign 
natter ; for, when well washed, it is nearly inodorous. 

This gas is transparent, colourless, and elastic, like 
eommon air. When mixed with twice its volume of 
oxygen gas, and a lighted taper applied, or an electric 
spark passed through, an explosion takes place with a 
report, and carbonic acid and water are the re-. 
100 cubic inches of the gas require for com- 
iHution exactly 200 cubic inches of oxygen ; and, after 
the explosion, they are found condensed into 100 cubic 
inches of carbonic acid. As oxygen is not altered 
in bulk by being converted into carbonic acid, it is 
evident that 100 cubic inches of the oxygen were con- 
Bumed in forming carbonic acid ; to do which, 12-682 
pains of carbon were required, and this was the whole 
quantity of carbon present in the original 100 cubic 
inches of carburetted hydrogen. We have now only to 
discover the quantity of hydrogen which it contained ; 
^^i as the hydrogen was saturated with and condensed 
ky the other 100 cubic inches of oxygen, it follows that 
^ere must have been 200 cubic inches of hydrogen 
present, the weight of which is 4*2394 grains. These, 
•dded to 12*682 grains of carbon, give us 1 6*921 grains 
te the weight of the original 1 00 cubic inches of car- 
buretted hydrogen. We may therefore infer, comparing 
this with the weight of common air, that the specific 
gravity of carburetted hydrogen is 0*549. 

Olefiant gas, — This gas, which is also called carbu- 
iBtted hydrogen, is similar in appearance to the former: 
it has no smell : 100 cubic inches of it weigh 29*6034 ; 
hence its specific gravity is 0*9608 : 100 cubic inches, 
mixed with 300 of oxygen, and a flame applied, or an 
dectric spark passed through, will explode violently, and 
the bulk of the whole will be reduced to 200, — these 
leing carbonic acid gas. Hence the original gas con- 
listed of 200 cubic inches of hydrogen ( — 4*2394 grains) 
ind 25*364 grains of carbon, all condensed mto 100 
obic inches, 
Blcarjlfiirett^d hydrogen wiw^ originally called oleJlanV 



Or OHBMIBTBir. 

gaa, because, by combinstion with liydrogen, i 
liquid whicb liaa an uily appearanct'. Jn bi 
produces a dense, while, and voluininoua San 
illuminates Etrongly. It may be copiously genetaled bj ! 
heating a mixture of one meaeure of alcohol with three ' 
of concentrated sulphuric acid in a retort : an effertet- 
cence takes place ; and a gas cornea over, which, liter | 
a little haa escaped, is received in jara in the uaatl [ 
way, using water, whitened by lime, in the pneumado 
trough, that any carbonic or sulphurous acid may be 
absorbed. 

When this gas is several times passed through « 
intensely heateil earthen or metallic tube, it is partiiflT I 
decomposed, and it sufiers a great diminution of ithi- 
ninaling power. It may be totally decomposed by ■ 
current of electrical sparks. 

Carburetted and hicarburetted hydrogen bear very dif- 
ferent relations to the well-being of man : the ftunffi 
when a spontaneous production of nature in mines, is one 
of the most terrific instruments of destruction, and * 
great obstacle to human industry ; for, by mixing witu 
ft certain quantity of common air, it acquires the pRH 
perty of exploding when accidentally kindled ; and 
thousands of human lives have fallen sacriliceji to in 
violence, until the splendid invention of the safety lamp 
divested it of its terrors. Bicaiburetted hydrogen is ibl 
chief, although not the most abundant, ingredient in 
coal gas, now so generally used for illumination : tbB 
other ingredients are carburetted hydrogen, hydri^, 
and carbonic oxide. Coal gas is made by introducing) 
quantity of bituminous coal into a large iron cylindo 
^ed a retort, close at one end, and furnished with t 
mouth-piece at the olher, for closing or opening it: 
there is also a tube for carrying off the gas and other 
products as they form. A quick, strong lieat is applied 
round the cylinder; and a vast quantity of gas, com- 
posed of the four ingredients just mentioned, is thus 
extricited, with tar and an omTfloivvacsi \\q[)qt, both 
[_ of which are condensed by ^aasTOg ftnoo^ ijv^(* tm 



iBAP. t OABBOK. l67 

mersed in cold water. There is a great difference in 

the relative proportions of the gases in the mixture^ as 

also in the quantity of tar, according to the quality of 

the coal^ and the mode of applying the heat. The more 

tar the gas holds dissolved, the more dense will he the 

flame when the gas is made to hurn^ and the more dis« 

agreeahle will be the smell when it is not burning. 

A slow heat gives much tar and litde gas^ and that 

little of a poor quality : a quick heat gives much gas of 

good quality, and less tar. Owing to these and other 

causes, the illuminating power of coal gas varies much. 

Before it is let through the conducting tubes for public 

consumption, it is weU agitated in contact with a mixture 

of lime and water, or passed through strata of loosely 

strewed hydrate of lime : it is thus deprived of much of 

its smelly but also of some of its illuminating power. 

On on average, a chaldron of good Newcastle coal^ 

weighing 25 cwt.*, will afford 12,000 cubic feet of gas, 

provided that the retorts are new. After being used a 

few months, the product will not exceed 11,000 feet, or 

€vea 10,000. On the whole year, the average may be 

About 1 1,000. The quality of this gas is such, that half 

a cubic foot per hour is equivalent, in burning, to the 

light of a mould candle of six to the pound, during the 

same space of time : hence, one pound weight of coal 

will afford light equal to such a candle for 4^ hours. 

An illuminating gas of this kind is sometimes presented 

ready-formed by nature. A village of Fredonia, in the 

western part of the state of New York, is lighted with 

this gas as it naturally issues from a rock : the flame is 

large, but not quite so brilliant as that of coal gas. 

Oil gas may be prepared in the following manner: -^ 
A large iron cylinder, containing coke, being heated to 
redness, oil is allowed to drop on the coke by small 
quantities : the oil is decomposed ; and gases, nearly 
similar to those obtained from coal, are produced. 
But, in a given volume of oil gas, there is much more 

• The chaldron ig generally estimated at S7 cwt. Mr. LoweH tUA«Qi«nXA 
diotr it to be Mtmit S5 cwL 

M 4l 



i 



t t h u m nrice Ae 

faapcrial Kdda irf Ae nry hm ii hfc J «a 

abeoi 120 cMbie fm «f e>: ' 

dM« not txatd 80 «r 90. «*»« «■ Aekad ^MJHy 

(b« oil cootrooDlf cfaplojcd- Bom ^ m aaMsbcknM' 

ia ibc ■une maniitT at ofl pa, rsnpt lb«, imi^ iC 

^W o m p wiog oil in the retons, dx^ bk a li^nd ftC- 

pH«(l by Bieltin); common ■mbeT.-cotna^ rcsn with ■ 

kilMl of ibin fn\, nbich antes during the decompoaiioa 

ot ibe redn, wiil condeoies in ibe ppes- Tbu gH 

_ JWRI* Is have an ilium inaiiog power not mnch supencrtt 

■food coal gaR. Many bouses are lighted with it; and itia 

uH prncnl iMcd for portable gas-lighia ; it being fbandV 

B|o«C IcH by the DondensatioD of liqttid hydrocarbon a 

Ut under ilic nccetsary prMsure, tlian oil g!u, beside bong 

Binuch cheaper. 

I Supirriibfiant gun. — Beside carburelted and bicir- 
■hlreilcil hydniK<^n, a third gaseous coni])Dniid i» belitnd 
no eslit, wliicli ia obtained during the decoinpositioD of 
Boll fur producing no illDmtnating gsB, but which is nM 
B^ocumble in a separate form. It has been named supei- 
Klcflant gu. One volume requires, for complete coB- 
Hbuation, aecording to Dr. Henry, 4§ volumes of oxygn 
MM, unil affbrds ii volumes of carbonic aciil. From tint 
■U la eaHy to calculate its compasition. If 3 volume^ 
MRIppOio .^00 cubic inches, of carbonic acid are formed; 
■rilvn >^00 cubic inches of oxygen combined nlA 
HIB'tiXa X 3 =) S8'04f) grains of carbon, which va( 
Mm whole quantity in the su|)eroleflant gas. There re- 
nBalned 1^ vuluin«i that is, 150 cubic inches, of oxygen 
Wfn combine with the hyilrogen, nhich, consequeDtiy, 
btut h«Y« be«n twice as much, or 300 cubic inches 
nNlghtng(!i'Il!l7 >' 3 =) (i-3S91 grains, ivUch, wbea 
ndd«d to the S»-n*fi grains of carbon, give 41 405 U 
H# Wtijiht of the original 100 cuVnc \ncl\e« of super- 
ptfjuil gaa. The specific graVw^ ol sw^eitie&KO. ^x 



«BAP. I. CARBON. IGQ 

V therefore 1*4412. The existence of this gas, as a 
distinct compound^ has been questioned; it has been 
nggested, that it may be a mixture of carburetted hy- 
drogen with some of the other hydrocarburetted products 
presently to be described. But superolefiant gas may be 
exposed to a degree of cold, without condensing into a 
liquid, which the other hydrocarburets cannot sustain, 
and continue in the gaseous state. This, connected 
^h the facts abeady stated, seems to render it very 
probable, that superolefiant gas is a distinct compound. 
Its name is inappropriate. 

The two compounds of carbon and hydrogen that 
wmain to be described were discovered by Dr. Fara- 
day, with some others which present less distinct 
ttsults, in the oil gas which had been compressed into 
4e recipients of Gordon*s portable gas-lights. Com- 
pression of common oil gas to 30 atmosphere scaused 
Ae deposition of a fluid, the specific gravity of which 
Was but 0*821. Dr. Faraday found this to be a mixture 
of various bodies, separable from each other by their 
difference of volatility. By a complicated process, he 
obtained a bicarburet and a carburet of hydrogen. Bi- 
carburet at common temperatures is a transparent, colour- 
jess liquid, having a mixed odour of oil gas and almonds: 
Its specific gravity 180*850: it crystallises, but the crystals 
^Qse at 42"^ : at 0^ it is white, transparent, and as hard as 
loaf sugar : it boils at 1 S6°; burns with a bright flame, and 
much smoke : its vapour mixed with oxygen detonates 
powerfully. The other compound, which for the present 
Daay be called Faraday's carburet of hydrogen, is a liquid 
It 0^ : it boils and evaporates at a temperature below 
i2^ ; the vapour may be recondensed by cold; it is 
herefore not a permanent gas. Its specific gravity, when 
:ept liquid at 54^ by pressure is 0*62?: it is, therefore, 
he lightest body in nature. Its vapour burns readily, 
nd with a brilliant flame. 

One hundred cubic inches of the vapour of Faraday's 
icarhnret of hydrogen require 750 cubic inches oi ox-'j- 
B for tbeir oombastioiij and the result is 600 oi cw* 



I 

I 



bonic acid, and the due product of water. The ctrhiM 
of hydrogen requires 6"00 of oxygen, and the resulting 
carbonic acid is 400 cubic inches. In the manner already 
sbowD, we may hence calculate the constitution of bolh, 
and the specific gravities of their vapour. Faradaji'i 
hicarburet must coneist of 600 cubic inches of CRrbm 
vapour, and SOO of hydrogen condensed into 100 rulic 
inches ; but the carburet is composed of 400 cubic inuba 
of carbon vapour, and an equal volume of hydrogen cod- 
deased into 100 cubic inches. 

names of these five compounds itiett 
much confusion ; and the necessity of reform in 
the existing nomenclature of the science is no wheit 
more conspicuous. The source of the perplexity in tbii 
case arises from a circumstance in the conslitutioB d 
matter which has but lately come under the cogniiuW 
of chemists, and for which no provision was made by 
the framers of the nomenclature at present in use wboi 
their system was originally promulgated.* It was fv- 
meriy supposed, that when the ingredients of two com- 
pounds and their relative quantities are tbe same, lb> 
compounds themselves are tlie same. This view is n« 
found to be incorrect. The elements and their ratio m^ 
be identical, yet the resulting compounds may he lolil^ 
different in their properties. Of the truth of this pod- 
lion, perhaps, no better proof need be adduced than some 
of llie hydrocarburels at present under consideradoB i 
•llhough the relation of phosphoric and pyrophosphoM 
acids, that of acetic and succinic adds, and of tbe tM 
kinds of tartaric and stannic acids, to each other, nufifA 
be adduced. We have a gas which contains 200 vohinw 
of cathon vapour, and ^00 of hydrogen condensed in» 
100 ; another which contains 300 volumes of each con- 
densed into 100 ; and a third, which, in 100 volumo, 
contains no less than 400 volumes of each. 

In these cases the ratio of tlie ingredients, which It 
the circumstance that determines the prefix of a name, 
cannot be made the basis ot a i&svmoi'ie appellation, it 
being the same in ^. The^ s\ioui'i,solMaa>:Q*-?iA3» 



^BIP. I. OABBOK. 171 

in use are concerned^ have the same name^ because they 
tie varieties of the same thing. How^ then^ are they to 
be distinguished ? In the class of substances alluded to 
tbove, such as phosphoric^ stannic^ and tartaric acids^ 
perzelius prefixes the Greek preposition vapa, to the com- 
poand less easily obtained ; thus paraphosphoric^ para- 
itannic^ paratartaric acids. But these prefixes do not 
nem to apply to the cases under consideration. As some 
distinction must be made^ I shall here adopt one that is 
not founded upon any consideration of the number of 
atoms which constitute an integrant particle — for on this 
subject all our information is uncertain ; but on the fact 
that the three varieties of carburet of hydrogen differ in 
Ae condensation of their constituent volumes. The first 
(200 volumes -|- 200= 100) shall be simply called carburet 
of hydrogen ; the second, being composed of 1 ^ times the 
Tdame of the former (300 + 300= 100), will be sescu- 
plocarburet of hydrogen; and the third, containing intrin- 
sically double the volume of the first (400 + 400= 100), 
inll be duplocarburet.* 

It remains to decide on the names of the other two 
compounds. The old marsh gas consists, as will be ex- 
plained hereafter, of two atoms of hydrogen combined 
with one atom of carbon : it may therefore be called 
kihydruret of carbon. On the other hand, the compound 
discovered by Dr. Faraday consists of two atoms of carbon 

*Tbe words sescuplum and duplum^ as every one knows* are derived troxa 
pGca, a fold, compounded with sesqui and duo : hence, in the present in- 
stances, they form adequate prefixes. Sescuplocarburet means " one and 
a half.fold carburet," which just applies to the condensation of 1| volume of 
the simple carburet into one volume of the sescuplocarburet. Duplocarbu. 
KC, meaning ** two-fold carburet," exactly designates thetwo-fold condens. 
aUon of the carburet into this gas. Sescuplo answers better than sesquipio, 
u chemists already use »esquL but for a different purpose. 

The prefix bis or disia useful (or expressing the repetition of the atom 
of matter that is indicated bv the part of the name to which the prefix is 
attached : but I think the e£[bct of the prefix so attached should not ex- 
tend to the matter represented by the other part of the name For in. 
stance, the name ditculpkate of altmtina, at present given to the com. 
pound of 1 atom of sulphuric acid and 2 atoms of alumina, might seem to 
convey that 8 atoms of sulphuric acid are combined with the base. By 
inverting the order of the generic and specific members of the name, the 
Oreek or Latin numerical adverb may be prefixed without fear of inv«cotL. 
ception. In th/g wmj I bav^ used the names bihydruret of c«x\)OU ttsvOLYa- 
cutniret of It jrdrQgen,~m terms generally acknowiei^is^. 



of hydrogen, — a name sufficiently expressive, and »nito- 
goUB with t)ie fonncr. 

lowing distinct hydrocsrburets: 1st, bihydruiet of ca- 
bon ; 2d, carburet of hydrogen, of which there ate ihtce 
varieties ; 3ii, bicarburel of hydrogen. With regard to 
the second compound aiid its varieties there can be lio 
confusion, for two of them are distinguished by ptffiws 
peculiar (o them ; and when the name carburet of hy- 
drogen is used without a. prefix, it means that one whid 
is unity with regard to the others in paint of cont1en»- 
stion. In the carburet of hydrogen there is nu pred». 

as will be explained hereafter ; and this condition seRnt 
best expressed by a name without a prefix. 

Tabla of the chief CampounrU of Carbon and Hydng^ 






"--- 


r„^«f 


S^ 


^^r 


i 




In ,irU„.. 






C«lM. 


M,.r- 


'^. 


H,rtr- 




J»cuplo. 
3. Binrbuw) 


iSSSt 


.^ 


600 


aw 






mm 




it 


It might appear to the student, that, as the ihrM 
'orielies of carburet of bjilropen Aifiei otl\-j vti densilj 
would be possible to bring ihem ai\ Xo ■&*; «4.roe tw. 


1 



laUP. I. CARBON. 17s 

ititution by mechanical rarefaction or compression. But 
this is not so ; for they would return to their former 
volume on the removal of the restraint. 

The compounds of carbon and hydrogen correspond 
with the law of multiple combination already explained 
in the chapter on affinity : the last column of the table 
shows the series of numbers representing the quantity of 
carhon which a certain quantity of hydrogen combines 
lith. This series^ when reduced to its lowest terms^ is 
1, 2, 4. There are other hydrocarburets known, of 
which the chief are naphtha and naphthaline, both ob- 
tained from coal tar by distillation : the former is a 
transparent, colourless, volatile liquid ; the latter is a 
transparent, colourless, volatile soUd, which assumes the 
form of crystalline plates. 

Cyanogen, — When charcoal and ammonia are heated 
in contact, a compound is produced of very singular 
properties. Ammonia is composed of hydrogen and 
82ote : the compounds of charcoal with hydrogen possess 
no such properties as those noticed by Scheele ; conse- 
quently, they must be attributed to the formation of a 
comhination of charcoal with azote. When a combin- 
ation is effected between azote and carbon, no matter by 
^hat means, a gas is produced which resembles common 
>ir, so far as elasticity and transparency are concerned, 
although by mechanical pressure it is condensed into 
* liquid. 100 cubic inches of this gas weigh 55*3996 
pains, hence its specific gravity is 1*798. Water 
absorbs about 4^ times its bulk of it. It kindles 
^ the flame of a candle, and burns with a beautiful 
bluish purple light. When 100 cubic inches aie ex- 
ploded by an electric spark, along with 200 cubic 
inches of oxygen, the result is 200 inches of carbonic 
scid, and 100 of azote. Hence this gas consists of 100 
cnbic inches, that is, its own bulk of azote, holding twice 
12*682 grains of carbon dissolved, or 100 cubic inches 
of azote combined with 200 of carbon vapour : but it 
contains no hydrogen, as appears from tVie iael oi \\i^ 
m producing a pardcle of water when b\iiiit YJ\t)!a. ax.1* 



Bc*. Tbemetbod of pnfHnglUi pBrnDbepreBodf 
Uiie,o>etii> 



a wQl be diown haafio'. 



Is the presEnce of ibc 

property iif 
gM has bcea calM <7- 

Hgdroeyanie arid. — CTUingni gis has the property lif 
combiDing wiih both b jdragni and mjgen, and formii^ 
■cidt. If we Mmtnne eqtul rtAvmta of cysnogen and 
bj'drogen, two volames will itsulc of a compoiind whiA 
feddena v^etable Uaes, and pttssesses the other proper' 
tiea of an add. This add is still in the state of pi,' 
bat it is readily absorbaUe b; water or alcohol. Beiii( 
composed of hydrogen and cj!Uiogen, ii has obtained 1 
name indicative of iu origin, add is called AyrfrotjiOTie 
ocirf ■' it has been for some time used as a medidne : it 
is capable of acting as an immediate and virulent paiNfi 
whether it be breathed in the gaseous form, or «wll- 
lownl, or rubbed to the body in its liquid form, l}»t i( 
condensed by cold or in water. It was formerly oiled 
Pni«eic acid, from being; an ingredient in Prussian blue- 
It may be prepareil by boiling a mixture of 6 
ounces of Pmssian blue in powder, with 5 ounces of 
red precipitate (i. e. peroxide of mercury), and W 
ounces of water, for half an hour, then straining thiMg^ 
paper, and hoihng away some of the water in s glM 
vessel. On cooling, the liquor will deposit crysl»ll 
which are a compound of cyanogen gas and mercurji 
called cyanuret * of mercury. From this salt we nsy 
prepare eitlier cyanogen gas or hydrocyanic acid. If, 
after being perfectly dried, it be distilled in a retort by 
heat, cyanogen gas will come over, which is to be col- 
lected in a pneumatic trough filled with mercury, ae it 
is absorbed by less than one quarter its volume of water. 
Or if the salt be distilled in a retort with seven eighths 
of its weight of muriatic acid, specific fp-avity l-l6, we 
cblain Aydrocyanic acid in va^oatjNiV.X'Ai. thi-j be coo. 



CBAP. I. OARBOK. 175 

' ^ieDBed by cooling the receiver with snow. This liquid 
contains a little muriatic acid and water, both of which 
can be removed by a second distillation from well-dried 

Liquid hydrocyanic acid has a most agreeable smell, 
which is easily recognised in certain flowers — the wall- 
flower, for instance — and in the blossoms of various trees, 
t8 the peach tree and hawthorn : this acid seems, indeed, 
to be their odoriferous principle. It is found in various 
bmels, as those of the apricot, cherry, and almond ; in 
^ last, in such quantity as to have occasioned death. 
It exists in the leaves of the common laurel so largely, 
that a water distilled from them is almost an instant- 
neons poison. This fact was discovered in 17^8, at 
DoMin, where several persons who had used it as a 
cordial, mixed with spirituous liquors, were poisoned ; 
tnd investigations were undertaken by Drs. Madden, 
Mortimer, and Rutty, to prove its virulence. Taken 
in very small doses, hydrocyanic acid retards the velocity 
^the circulation. 

Liquid hydrocyanic acid, which contains no water, is 
exceedingly volatile; it boils at 80^, it freezes at 5°; if 
allowed to evaporate spontaneously, it produces such cold 
is to freeze itself. By keeping, it in a very short time 
suffers spontaneous decomposition and spoils, especially 
if it contain muriatic acid : the more concentrated it is, 
the more speedily it suffers. When pure, its specific 
gravity at 64° is 0*697. If much diluted with water, 
and secluded from the action of light, it may be pre- 
lenred unaltered for a great length of time. Its vapour 
is inflammable. 

Cyanic acid, — When cyanogen is combined with 
oxygen instead of hydrogen, cyanic acid is obtained. 
It is composed of 100 parts of cyanogen combined with 
50*769 of oxygen ; hence, 100 parts of cyanic acid con- 
sist of carbon 35*3, oxygen 23*53, and azote 41*17.* 
By the process which affords it, it is obtained in a state 

• » Ceateginul ratios greatly facilitate calculation ; hence 1 i«to.m V.Yvcia» 
sUbotigti tbey axegcivg out of use. 



of ililution witli water ; and if kept in thta iOtt 
few hours, it ia diicoiiipostd, as well as smoe o 
water; the hydrogen of the latter and the aioieo 
former combine and produce ammonia ; and the c 
combine* wiih the oxygen of both the acid and i 
furinin); carbonic acid, trhich enters into combii 
with the ammonia. If the compound of tills add 
potush be boiled with water, a decompoduon 
place, and a compound of carbonic acid and patii 
aultG, ammonia bein|{ extricated. The taste of c 
mdd is Bour ; it reddens vegetable blues j its smell i 
what resembles that of acetic acid. 

Fulminic acid. — There ia another compound c 
anogen, uf an acid nature, whicli enters very extern 
into combitintion with bases; and most of the conipi 
which restilc have the remarkable property of prod 
a loud explosion, accompanied by the emission of 
and iiRht, when they are healed, rubbed, or struck, 
loudness of the noise has obtained for tlie acid the 
ot/utminic acid. According to Gay-Luasac and Li 
the fulminic and cyanic acids coneist of the samt 
mentB, and in the same ratio, although the prop 
of tiie two acids are totally different. Were this 
founded, it would afford another instance of the 
of the statement, that identity of elements and re 
quantity does not constitute identity of conKiitution, 
accorilitig to professor Davy, of the Royal Dublin 80 
who has been the most extensive enquirer into this 
Ject, fulminic acid differs from cyanic, not only ii 
ratio of its elements, but in containing an addii 
element — hydrogen. 

The substance from which this singidar acid is 
pared is the powder called Howard's fulminating 
cury. To obtain the latter, ilissolve 100 grai) 
mercury in a measured ounce and a half of nitric 
(specific gravity 1-3) by heal. Pour the solution, 
cold, on 2 ounces' measure of alcohol (specific gi 
0-S4ff} in a glass vessel, and a^^i^^ a maieiivc Wi 
1 effervescence be excited. Xjo-wiei gtwiBjii 



IBJtf.l. 0AB80N. I77 

opitates^ which is to he iminediately collected on a filter^ 
^ washed with distilled water^ and dried at a heat 
lot exceeding that of IxHling water. These are Mr. 
Boward's directions : the product he ohtained^ varied 
from 120 to L5S grains. It is not necessary to ohserve 
^ above speciiSc gravities very exactly : I succeeded 
"^ acid of 1*4^ and alcohol of 0*840; and my product 
"Weighed 113 grains. It is by no means a perishable 
compound : I have a specimen prepared about twelve 
years since^ which is now as violent as ever. When a 
grain weight of fulminating mercury is struck on an 
nvil with a small hammer^ a sharp^ stunning detonation 
it produced^ accompanied by a flash ; a little whitish 
moke is extensively diffused^ which occasions sneezing. 
A drop of sulphuric acid let fall on the powder causes 
it to bom off in a bla7.e^ without explosion. It is a 
e&riooB fact^ that this blaze does not burn gunpowder. 
fWminating mercury is composed of fulminic acid 
^ted to red oxide of mercury. The acid may be 
tnnsferred to other bases by double decomposition. Its 
compounds all possess the property of fulminating when 
wbbed or smartly struck. Fulminating silver may be 
prepared by the same process as fulminating mercury ; 
it is a highly dangerous substance^ and has been the cause 
of loss of life, and of many accidents. Fulminating 
gdd was formerly in use as a medicine. 

C^nuric acid. — Besides these combinations of cya- 
nogen^ there is another, which contains double the 
Entity of oxygen that exists in cyanic acid. It also 
nmtains hydrogen. It is called cyanuric acid, — a name 
peculiarly unfortunate, as its salts must be called cyanu'^ 
*^€Sy which, in utterance, is not easily distinguishable 
Tom cyanurets. Cyanuric acid is a crystallisable sub- 
lance. 100 parts of it consist of cyanogen 60*465, 
ocygen 37*209, and hydrogen 2*326. 

Ferrocyanic acid. — Cyanogen enters into combin- 
ition with both hydrogen and metallic iron, andfoim^ 9Xv 
idd^ ben^^ named ferrocyanic or ^ydro/errocyanic acxd. 
D ttus compound, 72'22 grains of cyanogen, ^5*9^ ol 



I 



boo, «nd 1'85 of hydrogen, are comliiiieil W form 100. 
s pale yellow colour ; is less perishable than by- 
dn»7'aiii(^ acid ; but exposure to light or heal decompows 
it into hydrocyanic acid and a white prectpitale, whicb, 
when it absoibs oxygen from the air, becomes Fruseiut 
blue. It reddens legetaUe blues, and expels the n 
bonic and acetic acids from carbonates and acetates. R 
■gents or tests do not discover the presence of iron 
this acid, because it is not oxidated ; but when some 
its combinations are heated strongly, its iron is oxiduedt 
«nd oxide of iron Is evolved. Prussian blue con^ 
^B acid, combined with peroxiile of iron ; at least, tbb 
18 the nature of its colouring matter ; and it is dtluteli 
■od rendered a colour of body by means of an adiaixtniE 
of alumina. 

There are three opinions concerning the nianne 
which the dements of this acid are combined. S 
consider the cyanogen, iron, and hydrogen, as combined 
together, without being coupled in any manner < 
reference to etch other : some conceive that an acidifi- 
■hle base, consisting of cyanogen and iron, is acidifisl 
by hydrogen ; an opinion which does not differ ncA 
from the former ; others suppose that the cyanogen ai 
iron, combined as a cyanuret, are dissolved in hydrw^* 
anic acid. An experiment was made by Mr. Forrtl^ 
from which inferences may be drawn that seem dr 
culateil to estabUsh the first or second opinion. By 
placing ferrocyanate of soda in the galvanic circuit, ll 
lodn passed to the negative pole, and the elements lit 
ferrocyanic acid passed to the positive. These elemaiS I 
are iron, hydrogen, and cyanogen. Had the iron btea ' 
in the state of oxide, as it was formerly supposed to k, 
it would have been found at (he negative side, ax h^ 
pens with metallic oxides. But it may be objected, thai 
being in the metaUic state, it should have been fouod 
there equally ; and this would certainly have been ibe 
ere it not that it was held united to the other 
I eferaenls by an aihnity so povierfvi ^kw, i.Ue ^vanie 
■ - of arrangeiaent waa avftifeHKi. "^Ve^imtsSOTC- 



CHAP. I. OARBON. l79 

skm of the galvanic order is obserrable in the caif of 
netallic oxides^ earths^ and alkalies. All these contain 
oxygen^ which^ when separate^ collects at the podtive 
pok ; but when combined with a metal^ goes along with 
^ latter to the negative pole, because of the powerfnl 
affinity which antagonises its natural tendency. The 
question now occurs, what were the other elements of 
the hydrocyanic acid which held the iron by so forcible 
sn affinity ? Those who maintain the opinion that this 
^id consists of cyanuret of iron, merely dissolved in 
hydrocyanic acid, would answer, that the iron and cya- 
nogen thus powerfully attracted each other ; and that the 
fact 80 far corresponds with their view, as the cyanogen 
would naturally pass to the positive pole. It must, 
however, he recollected, that the validity of this answer 
tt negatived by the passage of hydrogen to the positive 
pole, contrarily to its natural tendency ; and the posi- 
tion is not tenable that it wa« carried over by the affinity 
of cyanogen — for so weak is that affinity known to be, 
^at cyanogen and hydrogen will not subsist in com- 
l>ination sometimes for more than a few hours. The 
conclusion seems inevitable, that ferrocyanic acid does 
Hot consist of cyanuret of iron dissolved in hydro- 
cyanic acid ; but tUat it consists of iron, carbon, azote, 
and hydrogen (not adverting to whether the three first 
constitute a base acidified by the last), all held by an 
affinity capable of resisting the decomposing energy of 
galvanism. Hence tlie greater permanence of this acid 
than that of hydrocyanic acid; yet by the agency of 
water and light it is at length decomposed. It is true, 
&at in Mr. Porrett's experiment some hydrocyanic acid 
was volatilised, and some Prussian blue was formed; 
but this was because the iron, on arriving at the pla- 
tinum wire of the positive pole, was oxidated by the 
water in the same manner as the wire would have been 
were it iron, or as the platinum itself would have been 
had it been in nitric acid, and the galvanic battery 
very powerful. But for the interposition of the g;Ei3LN«oi<i 
igeocy on the iroDj there would probably Yiave \seevi xift 

N 2 



TW fMMitiw «C fKtan and uow in ferrecjnu 
mU m ia dw nAu mecnmrj to the formation of cf 
Hsgw ; dM hj<to y i> <nlj id nich quandtj ti V 
«1 HH t»w diiwb of tkc <7aiK^ai into hydrocjuue 
acU ; tW WMWMig tbM «f e^uiogea is wiCGcient ta 
The otjjea of these oi* 



Tltu • MMil «Im«U MOMiinte an element it 
vkidki witli kyli c y, Anns tm aciil, will Ik tlia 
kw MUrnaaf. «lw*t il )* considered, that the meal 
MttariuH, by indf, it actoall; an acidifiable buc with 



Chlorine, as almd; aialed, Ji a gss of a greraUl 
colour. Il may he prepared by mixing commOO 
*ea lalt witi) tl)iv« tguiTlert its weight of Uack oxidj 
of nian(^e«e, inirailuciiig them into a retort, and 
pourifift on sulphuric aciileijual to ihe weight of ihesalli 
and diluted with its own weight of water. The lai 
mixture should be added at tno or three diRerentdnM, 
the gw proituoetl b; the first quantity being collected 
before the «ecoiid aciil is poured on : this precaulioo 11 
to gnanl against loo violent in effervescence ; and on tba 
Mine account no heat should be applieil until the eSbi- 
Tescence becomes very moderate. After the comtnoq 
air has been expelled, the gas may be coUecteil in bottEea 
filled with water, and inverted in as little water ai wiQ 
anEwer the jiurpose, in order to prevent waste by ab* 
^ lorpiion. The bottles, or pneumatic trough, muit not 
mhe filled with mercury, as this oieCai is powerfully acted 
vin by chlorine. 



€lil»i; OHtiOlUNB. 181 

Chlorine^ if Inreathed undiluted^ is fatal to animal 
Ife, but does not extinguish combustion. A candle 
Ittnis in it with a red flame. It possesses the remarkable 
imiperty of setting fire to many of the metals^ even at 
^ common temperature of the air^ when introduced 
into it^ beaten out into thin leaves or reduced to filings; 
fltteh are copper^ tin^ arsenic, zinc, and antimony. 
Phosphorus, when introduced into it, burns with a pale 
white light. Mercury absorbs it rapidly. Water ah- 
lorbs twice its bulk of it : the solution is called chlorine 
witer; and if this be exposed to light, some water is 
imposed, its oxygen is liberated, and the hydrogen 
Gombines with the chlorine, forming muriatic acid. As 
^ combinations of metals with oxygen are called 
^des, so the combinations of metals with chlorine are 

Chlorine has the property of destroying all vegetable 
colours. If a vegetable blue, for instance, be exposed 
to its action, the colour is not altered to red, as it would 
^ by an acid, — nor to green, as it would be by an al. 
'^, — but it is totally destroyed ; and the medium, in 
^e substance of which the blue was contained, appears 
^^lourless, at least so far as the vegetable was concerned. 
^ this account, chlorine has been introduced as a 
powerful agent in the art of bleaching; for if un- 
bleached linens be properly exposed to its action, the 
natter which gives them their gray colour is destroyed, 
fid the linen assumes the whiteness which is natural 
> its fibre. Flax is naturally white, and owes the 
ray colour which it assumes solely to the processes 
irough which it is put to separate its fibres — as im- 
lersion in bog streams, and other such injurious treat- 
lent. The chlorine, however, if applied in its pure 
ate, and not sufficiently diluted, or otherwise cor- 
seted, invariably destroys the strength and texture of 
le linen ; and, therefore, it is a dangerous agent in the 
ands of the inexperienced. 

The specJSc gravity of chlorine gas, wYien c\y\Me ^t«a 
om watery vapour, is, according to Thotasow, ^-5' 

N 3 



I 



100 cubic inches of il, therefore, weigh 77'0987 gnto j 
When perfectly dry, it remainn a gas at the tempenilUK i 
of — 40'^; by means of mechanical pressure, it mtylK 
condensed into a yellow liquor; in which state it remuu 
only while the pressure continues. IVhen aaturtirf 
with watery vapour, or dissolved in water, and eipoiw 
to a cold of 33°, it forms into crystals, which consill of 
72-3 of water combined with 27-7 of dry chlorine. ThU 
compound is called kydTate of chlorine. 

Chlorine has an affinity for oxygen, and they com- 
bine in no less than four proportions : two of tbMD 
contain so much o\ygen aa to form acids ; and theolhet 
two, as [hey lio not manifest any acid properties, are to 
be considered as oxides. Oxygen and chlorine, iiot-' 
withstanding their affinity, do not combine when pw- 
sented lo each other ; but they may be detached in 
combination from certain compounds which contaili 

Proio^ide of chlorine. — When 100 parts of chlorin« 
combine with 22-219 of ""yge", a gas is prodocrfj 
which, as it is the combination containing the leosl 
oxygen, is called protoxide of cklorinp. 1 1 has a smfl] 
resembhng burnt sugar. It was discovered by aiiff. 
Davy; and was named by him euehlarine, in consequenK 
of ita very green colour. Under strong pressure, ikis 
gas is condensed into a liquid. Wlien warmed in « 
glass tube, even with the heat of the hand, it cxpkKlw, 
and expands into a greater bulk, the increase being ^tb 
of the whole ; a flash of light is at the same time pro- 
duced ; and the tube is now found to contain a mixnue 
of oxygen and chlorine, no longer in combination. 
Combustibles first decompose eitchlorine, and then bum. 
It reddens v^etable blues, and then destroys the coloui 
totally. 

Peroxide of chlorine When 1 00 parla of chlorint 

■re combined with four times the quantity of oxyger 
which enters into the protoxide, that is, with 88876 ol 
oxygen, the compound formed \% x\\e ^otoxide. It^ u 
wM as the protoxide, maj be coUecVeii. o\et mracas^^- 



i.«BAP. I. OHLORINE. ISS 

flSutt metal being not affected by either gas ; but both of 
them are absorbed by water. The colour of this gas is 
•n intense and livdy yellow. It discharges vegetable 
ctdoarSj like chlorine. When heated^ it explodes with a 
•considerable emission of light; and 2 volumes expand 
into 3 : these 3 volumes are a mixture of 2 volumes of 
•oxygen and 1 of chlorine; the gases being no longer 
in combination. Phos^^orus^ immersed in it^ causes an 
explosion by decomposing it ; oxygen and chlorine re- 
mit, and the phosphorus bums in the mixture. Per- 
<xxide of chlorine may be formed by thoroughly mixing 
•-« imall quantity of die salt sold by druggists under the 
mme of ehloreUe or ojpymuriate of pot(uh, vrith as much 
■nlpharic acid as will form a paste^ and exposing the 
Jnixture to a very gende heat, in a very small retort : 
*QmU quantities should be employed, lest explosion 
>bould take place. The same salt^ when heated with 
'^ute muriatic acid, affords protoxide. 

Chloric add. — When 100 parts of chlorine combine 

Mth five times as much oxygen as exists in the prot. 

<>xide, that is, with 111-095 parts of oxygen, an acid 

"*5 produced, which is called chloric acid. It was for- 

■ ^erly named hyperoxymuriatic acid. Water is neces- 

' ^ary to its constitution ; and, hence, it is always ob- 

' Gained in the state of a solution in water, which has an 

^dd and astringent taste, but no smell: it reddens 

^^;etable blues, — the characteristic power of chlorine on 

* v^etable colours being subdued ; the colour, however, 

is at length destroyed. 

Perchhrie acid, — The last compound of chlorine 
-and oxygen is formed when the quantity of the latter is 
seven times greater than exists in the protoxide; or, 
when 100 parts of chlorine combine with 155*533 of 
oxygen. In this case a distinct acid is formed, called 
perchloric acid, the properties of which have not been 
ascertained. 

Thus chlorine, by uniting to different portions of 
oxygen^ forms four different compounds. TVie dewvewXa 
-in all of them are retained by a very {ee\Ae «S&Qi\:^ \ 

N 4« 



I 



tmnf erred EroB 
tchicfa often Man 
dace the numbeiE Ttfinh 
teati r ^ the i fiff a e nl qvHiIidei of oxygen, ni. 92'Sl% 
88-S76, 1 1 1-095, 1 55-53S to tiieit' lotrest lenns ; thai 
the oxtgen of ibeprotoxulevfill be I. of the peroxide4, 
that of chloric acid 5, uhI tbu of pcichloric tdili 
■11 these nombers being in conformiry with the iloctripe 
of maliiple raiios. It is probaUe that other tompMoit 
wiU jet be discovered. 

Murialic or HifdnMoric acid. — Besides unidog 
with oxygea, chlonne combiaes with hydrogen, and 
farms muriatic acid. If chlorine and hydrogen be 
miieil together in equal volumes, and exposed to com- 
mon daylight id ■ gUss flask, they vrill, in a little time, 
eomUne; and evea esploile in combining, if they had 
been exjiosed to sunlight, or to the aciion of an etectrif 
•park, or to the light of a candle. Two volumes of 
mortatic gas result. Besides this synthetical proof, the 
composition can be shown analytically. 

Muriatic acid gas, in its pure state, is transpareD^ 
eolourless, and elastic : under very strong pressure, it 
condenses into a liquid. A volume of chlorine and a 
volume of hydrogen combine and form two volumes of 
muriatic acid gas : hence, as there is no change of bulk 
by coodensMion, ne can find the specific gravity of mtk 
riatic acid by adiling tt^etlier the specific gravity of cadi 
constituent, and taking half the sum as the spedfie 
gravity of the compound. The specific gravity of hyr 
drogen is 0'06'ST9, that of chlorine Q-5 : the Hun is 
2-j;6S8, and the half is 1-3844, which is theapedfie 
gravity of muriatic acid gas, and Is identical with the 
ECBult of an experiment made by Thomson. Water 
absorbs this gas with avidity ; one cubic inch at 69^ 
absorbs 417-S23 cubic inches of the gas; heat is pro- 
duced, and, when cold, the bulk of the water is increased 
b) 1-3433 cubic inch. This is liquid muriatic acid: 
b these proportions of couatitueniB, its specific gra> 
is I'J958 : 100 grains oS it "awavti. ol «y?.^ <$ 



ff.l* C&X'ORIMIS. 185 

1 add and 59'6l of water. — ( Thomson,) But at 40®, 
«r is capable of combining with 480 times its bulk 
he gas. The specific gravity of the strongest liquid 
I that can be conveniently obtained is 1*203. In 
! state it is very volatile; it boils at 107°, and fre- 
Dtly forces the stopper out of the bottle in warm 
ither. At a temperature below freezings add may 
)btained so strong as 1*500; but as the temperature 
8, the liquid gives off acid fiimes^ which leave the 
ainder weaker^ until^ at 60°, it becomes 1 *203. It 
colourless liquid ; and^ when exposed to the air, it 
kes, because the gas exhaled condenses the moisture 
he atmosphere. It extinguishes both flame and life, 

is not inflammable. Its smell is pungent^ suflb- 
Qg^ and somewhat aromatic. It powerfully reddens 
itable blues. 

'he method of preparing muriatic acid, just now 
ribed, is not that employed for preparing it for 
Common culinary salt is the source from which 
derived. A mixture of this salt with sulphuric acid 
water is to be distilled with a heat barely sufficient : 
llow liquid acid comes over; but if the salt had 
I previously heated nearly red-hot, the acid is 
>8t colourless. According to Dr. Barker, of Dublin, 

made many experiments on the subject, equal 
;hts of salt and sulphuric acid give the largest pro- 
. With 5000 grains of salt, the same of the 
igest sulphuric acid, and 8000 grains of water, the 
luct was 9389 grains of muriatic acid, specific gra* 
1*160.» 

hloride of azote. — There is but one known com- 
tion of chlorine with azote : it is one of the most 
lidable and dangerous substances in nature, owing 
le facility with which it explodes, and the violence 
le explosion. It is called chloride of azote. Pour 
1 a flat dish a warm and unsaturated solution of 
ammoniac in water. Fill a phial bottle with 

ehis ** Observations on the Duhhn Pharmacopoeia.** paae36.',«k"'«rj 
commentary. 



I 



I 



1(180 ELEUKNca. or aoMwanr. H)Q;|^ 

chlorine, and cork it: then invert the bottle in llie so- 
lution, and uncork it under its surface. An ibsorpflori 
of the gas takes place; it decomposes the amraonit, ewi- 
binea with its azote, and forms a yellowish oil; mb- 
Btance, which ia chloride of azote. When one or two 
globules are formed, the process should be stopped 
on account of the danger. If heated to 212°, lUi 
chloride ia resolved into its elementa with a tmneii' 
douB explosion. Contact with phoaphonu, oik, "i^ 
A variety of suhslances, cause the same effect. I' 
conaiats of i volutnea of chlorine, combined widi 1 w 
azote. Its colour is pale greenish yellow. It bwa 
at 1(J0° : no known cold is capable of freezing it. I" 
consiatence ia little more than that of water. It >! 
soon decomposed when left in contact with water. I" 
specific gravity is I'65S. 

Ferchloride of carbon. — By the action of chlorine M 
defiant gas, a compound of chlorine and carbon Ib 
formed, called perchloride of carbon. When healed in 
a retort, it evaporates, and the vapour condenses iaio 
crystals. If sublimed rapidly at a high heat, it fonoB 
B transparent, colourless mass. It buma in the flameoC* 
candle with a red light and much fiame. It hu * 
smeS somewhat reaembhng camphor ; like camphor H 
scarcely dissolves in water, but easily in alcohol, frdiB | 
which it ia precipiiated by the aftusion of water. Hoi j 
alcohol dissolves more than cold ; and a hot sohitii* ' 
affords crystals on cooUng : the aame may be said n 
ether. It dissolves also in oils. Camphor, included in 
a bottle, volatilises and crystallises on that side of the 
bottle most exposed to the light; thia cliloride do» 
the same ; and the other points of resemblance to cam- 
phor are striking. 

If thia perchloride of carbon be passed in vapour 
through a red-hot glass tube, a part of the chlorine is 
given off, and a protochhride ia produced, which ma) 
be condensed in a cool part of the tube. This is * 
liquid which does not seem W ^ssesa aa-j very strikinfi 
properties. 



42BiP. I. IODINE. 187 

t 

It has been observed by Dr. Silliman^ that if, in 
attempting to mix chlorine with olefiant gas, the latter 
be allowed to occupy the upper part of the vessel, and 
the former the under part, a bright flash and slight 
explosion will take place; carbon will be deposited, 
tnd the chlorine will disappear. 

Chlorocarbonic acid, — There is a gaseous combin- 
ation known in which carbon is acidified by both 
oxygen and chlorine. It is called chlorocarbonic acid. 
It is produced by exposing equal volumes of perfectly 
dry chlorine and carbonic oxide in a glass flask to 
s^ong sunshine. They combine and condense to one 
Volume. This is an acid; for it reddens litmus, and 
combines with certain alkalies. It has an exceedingly 
pungent smell. Water decomposes it. 

Section VI. 

IODINE. 

There exists a substance much resembling chlorine 
in some of its properties, and derived from a source 
which also supplies chlorine : they are both of marine 
origin ; the latter existing in sea water, and the former 
chiefly in sea plants. This substance may be procured 
by drying and powdering common sea weed, and heat- 
ing it with sulphuric acid : a violet coloured vapour 
rises, which, if received in a' cool vessel, will condense on 
its sides, and will form scaly crystals, of a somewhat 
metallic lustre. These crystals are the substance in 
question ; from the violet colour of its vapour, it is 
called iodine. When exposed to the air at common 
temperatures, it volatilises slowly but completely ; but in 
close vessels it requires the application of heat for eva- 
poration. At a heat a little above that of boiling water, 
it melts ; at 350°, it boils and evaporates in a violet 
coloured vapour, almost exactly the colour of the vapour 
discharged from indigo thrown on hot iron *, \\. ct^%\a)u 
Jises as it cools. The specific gravity oi vodVcL^ \%, ^^i- 




I 



cording W Dr. Thomson, 3-084. It has a leaden guj 
metallic lustre, but it is a non-eontluclor of electridt;. 
It has resifited all efibrta to decompose it, and may be 
passed in vapour through a red-hot earthen tube with- 
out change. It has the pro])erl:; of fonninji; a beautiful 
blue colour, when mixed with a little powdered slarA 
diffused through cold water: and hence iodine and 
atarch are used by chemists as mutual tests of eadi 
other's presence even in the most minute quantity. 
Iodine stains the iingers yellow, and consumes the cork 
of the phial in which it is contained. It dissolvei in 
7000 times its weight of water, and the solution B 
brownish yellow : but it is by far more soluble in aloohol 
m ether ; and the tmcture, if concentrated, is of a ieef 
reddish brown. It has a smell of chlorine ; like chlodiM^ 
it destroys vegetable colours ; and, hke that substance, it 
combines with oxygen or hydrogen — in either case fonn-. 
ing an acid. With chlorine it also forms an acid, whi(i< 
ie called chloriodic acid. 

The process given above for obtaining iodine, ta not 
the one by which it is procured for sale : and it can 
be now purchased at ao low a price, that no chemist ever 
thinks of preparing it for his own use. Dr. Ure bH 
I^Ten the process in flill detail : it is one invented bf 
himself ; the following is an outline : — 

Iodine is largely contained in kelp ' ; and it may be 
economically prepared from the brown oily. looking 
liquor which is the waste of the soap manufacture, and 
in which all the iodine originally contained in the kelp 
used in that manufacture is to be found. 

Every 8 ounces, apothecaries' measure, are to be 
mixed hot with 1 ounce measure of sulphuric add 
diluted with its hulk of water. IVhen cold, filter the 
Hquor; add 666 grains of black oxide of manganese; 
and introduce the whole into a large glass globe, oftt 
the wide neck of which another is to be inverted and 
k^t cool, while (he bottom of the lower o 



1 



(BAP.!. IODINE. 189 

V7 buming charcoal to about 232°. Iodide now sub. 
limes copiously^ and is readil j condensed in the upper 
THsd. From the above quantities^ about 1 drachm 
troy will be obtained. 

Iodine combines with sulphur) although without much 
iN-oe of affinity; with phosphorus it combines ener- 
getically ; it unites with carbon^ and with yarious me- 
tals ; but in none of these combinations is there much 
interest. It is a poison ; but in minute doses it is used 
in medicine^ and^ if long continued^ produces remarkable 
emadAtion. 

O^eide of iodine, and lodous acid. — There are three 
combinations of iodine and oxygen known^ — oxide of 
iodine^ iodous acid^ and iodic acid ; the two first were 
discovered by professor Sementini, and the following 
u the process for obtaining it^ as described by himself:— 
*' A copper tube^ two spans in length and eight lines in 
diameter^ is furnished at one end with a screw, its other 
end terminating with an aperture one line in diameter. 
This extremity must be bent in such a way as to be in- 
troduced into the tubulature of a retort^ leaving the latter 
a proper inclination. A bladder of oxygen must be 
screwed into the other end of the tube. Along and 
imderneath tbe tube, a long spirit lamp should be placed, 
famished with several wicks, which, when kindled, are 
capable of heating it to redness. At the same time a 
lamp must be placed under the retort. When the re- 
tort and tube are both nearly red-hot, one assistant 
strongly compresses the bladder, while another intro- 
duces a spoonful of iodine into the beak of the retort ; 
and this, falling under the copper tube from which the 
hot oxygen issues with force, is reduced to a violet 
vapour, which gradually disappears, lining the beak of 
the retort with a yellow, transparent matter, almost 
solid. This is the oxide of iodine; it has the con. 
sistence of a solid oil ; its taste is rough and disgusting ; 
it evaporates totally in the air ; it is very soluble in 
alcohol and water, and communicates an am\>et ^c^^<a>ii , 
which alkalies render colourless: brouglit m coTk\A£X 




I 



with phosphorus, the latler inflames." He fuilhei 
found, that " hy coutinuiog the jet of oxygen after ibe 
bvak of the retort becomes lined with the yellow, wft- 
HoUd oxide, iodouH acid will b^in to form, which nQ 
run down along the beak, and will announce itself sai. 
ficiently by the redness which it oecasiona in tinctnrt of 
turnsole. The production of iodous acid will be faci- 
litated, if, while the jel of oxygen is continued, the 
lamp, instead of heating the belly of the retort, is an. 
ployed to heat the oxide in the beak, which, immediate' 
ly combining with a new portion of oxygen, is converted 
into iodous acid."* Sementini has also shown, that by 
mixing iodine with chlorate of potash, both in powdH-, 
and in such proportions as will produce a yellowish 
colour (three parts of chlorate of potash and one of 
iodine succeed best), and applying a gentle heat, so 
amber- coloured liquor (listila over, evaporable at w low 
a heat as 112"; of a strongly acrid and disagreesble 
odour; capable of reddening without destroying vegb 
table blues, and of inflaming phosphorus. This tit 
is iodous acid. In order to produce it, a gende heit. 
must be applied. A strong heat will altogether cbuige 
the nature of the products.-)- The acid will more ce»> 
tainiy be obtained pure, if three parts of chlorate ef 
potash to one of iodine be employed. 

Iodic acid. — By exposing iodine to the action of piol> 
oxide of chlorine, the latter is decomposed ; its two 
elements combine with iodine ; and two compounds at 
farmed, named chloride of iodine and iodic acid. Ai 
these substances differ in volatility, the apphcation at 
heat drives off the former, and iodic acid remains. It 
is a Bohd, semi-transparent, white substance, not only 
soluble in water, but dehquescent. It first reddens and 
then destroys vegetable blues. When heated strongly 
by itself, it is resolved into its elements ; but if healed 
with combustible bodies, an explosion takes place. 

Chloride of iodiiie may be prepared also hy 

• GiDrualeaiFiiiCB,lB2b,3ST. -^ \»ji,\« 



eJEUP.-I. IODINE. 191 

Iodine to chlorine : the latter is absorhed^ and a chloride 
is produced which manifests the properties of an acid ; 
but it is uncertain whether in its own nature it is an 
add^ or whether it becomes one only when, by decom- 
posing water, its elements are acidified. Those who 
consider it an add in its own nature, have given it the 
name of chloriodic acid. At ordinary temperatures, it is 
a dehquescent solid ; if heated, it melts into an orange 
Hquid ; and if still further heated, becomes an orange 
yellow vapour. 

Hydriodic acid. — The combination of iodine with 
hydrogen posflesses properties which eminently cha. 
racteriw it as an acid : its taste is acid, it reddens vege- 
table blues, and it combines with bases. The name of 
diis compound indicates the two elements which form 
it ; it is called hydriodic acid. It may be procured by 
Che direct union of its component ingredients: if the 
vapour of iodine be passed through a red-hot tube along 
with hydrogen, both substances combine, and a colour- 
less gas results, which is the acid in question. This 
gas, when allowed to escape into the air, condenses the 
moisture of the air, and thus produces abundant white 
fumes. It is decomposed by almost all metals ; the iodine 
combining with the metal, and hydrogen being left un- 
combined. The same decomposition is effected by 
heating a mixture of it and oxygen or chlorine ; water 
being produced in the former case, and muriatic acid in 
the latter, by the abstraction of the hydrogen, while the 
iodine is liberated. Hydriodic acid gas may be ob- 
tained by the action of iodine on sulphuretted hydrogen ; 
the iodine takes the place of the sulphur ; and on this 
fact is founded a good process for obtaining liquid hy- 
driodic add, which is as follows : — Triturate iodine and a 
a small quantity of water ; when the mixture is tole- 
rably smooth, add more water, and pass a stream of sul- 
phuretted hydrogen gas through it, arising from a mix- 
ture of sulphuret of antimony and muriatic acid heated 
in a flask. The gas may he transmitted tYixoM^ \)[ie 
Iodine and water by means o£ a glass tube "bent ime^ «X 



ELBMEim or 



right angles, as in the sketch, — a ver j easily Q 
apparatus, wliich answers for all such purpoi 
Bulphuietted hydrogen ia decomposed; the mlphnrH 




I 



slmost completely separated; the hydn^en, coTDbiiiiiig 
Trith the iodine, dissolves it, and forms liquid hydriodic 
&cid, which may be filtered from the sulphur, and bailed 
for a few moments, to expel any rednndant sulphuretted 
hydrogen. This liquor, when distilled, at first gives off 
water only, hut at length the ax:id itself distils omt. 
Hydriodic acid gas ia absorbed copiously by water, ud 
the result is liquid hydriodic acid. This liquid, by tx- 
posuxe to air, ia speedily decompOHed. 100 cubic indiff 
of hydriodic acid gas contain 50 cubic inches of hydi»« 
gen, combined with 50 of the vapour of iodine. Thil 
gas is set on fire by pouring into the vessel which ean- 
Uina it a few drops of strong nitric acid. 

Iodide of azote. — With azote, iodine combines, al- 
though indirectly, and forms a curious detonating couf 
pound. If hquid ammonia be poured on ioiline, put 
of the ammonia is decomposed into hydrogen and azou: 
both of these combine with iodine ; the former produ- 
cing hydriodic acid, which unites to the retnsinder of 
the ammonia, and the latter affording the compound in 
guesdon ; to this the name of iodide of azote has been 
given. It is a dark brown powder, and is of so ei- 
plosire a nature, that not on\'j \ieWtt\^, VsiM. toviching it, 
wiV cause it [to detonate vioWn^"} •, "si'l. ■ 



SKiA X. . BBOMINa. I9B 

win detonate without any apparent cause. The results 
of the ex^osion are iodine in violet-coloured vapour^ and 
•aote ; and the cause of the explosion is dia concussion 
on the air, occasioned hy the sudden conversion of these 
two substances from the solid to the gaseous state. 

Iodine combines with several other substances, but 
the compounds need not be here noticed. 



Section VII. 

BliOMINS. 

This is a substance which resemble chlorine and 
iodine in many of their habitudes. If a large quantity 
of sea water be boiled down, and the common salt re- 
BiOfed until it no more freely crystallises, we obtain a 
itttdual liquor, called by salt makers bittern ; and an 
abtndanoe of it can be procured at the salt works, often 
without charge, for in many localities bittern is made 
no use of. Through this liquid,, chlorine gas is trans* 
nutted, until it assume a brownish yellow colour. Some 
ether being added, the whole must be well shaken, 
and then allowed to settie : the ether, now of a fine 
red hue, floats on the top, and, being decanted, must 
be shaken with pure potash, and dissolved in a littie 
water. The ether now loses its colour, because it 
has transferred to the potash the matter which caused 
the colour. The same ether may be agitated with more 
bittem, which has been treated with chlorine, and may 
tlma be nmde the medium of transfer between a large 
joantity of bittem and a small quantity o^ potadbu 
rhe solution of potash, continually agitated with fresh 
portions of etiiereal liquor, becomes so lughly charged 
it length, tiiat by being a litde evaporated it will afford 
nbical crystals in abundance. If these be distilled in a 
"etort with dilute sulphuric acid and some black oxide 
)f manganese, red. vapours will arise, wYulc\\ mvj \ife 
oadeased iDto a very deep reddish brown Wqvxox, >3nj 



KLBKBNn OP 

receiving them in a globe or fiask Eurrounded by ice « 
very colil water. Tiiis liquid is about three times u 
heavy as water (2-96) : it ia sparingly dissolred lij 
water, more copiously 1^ ether. At 117" it boi's; 
but even at ordinary temperatures it emits reilJiBh 
vapours, somewhat like those emitted by nitrouE add. 
It discharges the azure colour of litmus, as would 
happen with chlorine^ and witliout reddening it. Like 
chlorine, it sets fire to certain metals when brought in 
contact with it. It u not combustible, and it estio. 
guishes combustion ; it acts ae a strong poison, and 
corrodes the skin. It becomes a solid at a little belov 
aero ; but if combined with water so as to form a hy- 
drate, it affbrde iine red crystals at 32". Brought in 
contact with phosphorus, bromine occasions an expls- 
sion. Its vapour is not decomposed at a red heat. A 
taper immersed in the vapour is extinguished, aftd 
having its flame surrounded by a greenish mar^ 
topped with red. Starch is a test for bromine as wdl 
as for iodine ; hut it produces an orange hue, instead of 
the blue which iodine affiirds. 

Bromine, like chlorine, combines either with oiygen 
or hydrogen, and in both cases forms an acid. Tbe 
acid formed by oxygen is called bromic acid ; that will) 
hydrogen is hydr^romic acid. The fortner can only 
exist in combination with water ; but the latter is a gB 
which water absorbs, and acquires considerable aciditj' 
and density by so doing. Chlorine also combines wilb 
bromine : the chloride is an orange volatile liquid. 

The combinations of bromine are numerous, hut dMr 
-properties do not warrant tlie occupation of limited sgUt 
by particular descriptions. 



SULPHUR. 195 

Section VIII. 

SULPHUR. 

»ngst the various combustible bodies with which 
n observation makes us acquainted^ the sub- 
called sulphur stands sufficiently characterised 
well known appearance^ and the peculiar blue 
rith which it burns. It is much used in the arts 
inufactures. It is found in great purity in many 
)f the world, especially in volcanic countries 
t lava: it occurs in masses, and sometimes in 
; and it is an abundant ingredient in various 
s. It is of a yellow colour; is moderately hard; 
peculiar smell, which is increased by friction, or 
ntle heat. When a roll of it is held in the hand^ 
igth cracks in pieces. It is a non-conductor of 
ity, and when rubbed becomes highly electric, 
beated to 218°, it melts almost into a liquid; if 
a little more it becomes less liquid, and if much 
becomes tenacious ; on cooling somewhat, it re- 
its former liquidity. If it be allowed to cool 
le parts next the sides and bottom of the con- 
vessel are solid, while the central portion is stiU 
and the vessel is slowly inclined so that the 
art may run off, the interior will present a mass 

all over with crystals of sulphur. If, while 
and viscid, it be poured into cold water, it ac- 
omewhat the consistence of softened sealing-wax, 
this way it is often used for taking impressions 
als. When strongly heated, it boils and evapo- 
md the vapour condenses on any cold body in 
2 of a fine yellow powder, called flowers of sul- 
;he part that refuses to evaporate is called sul- 
<mm, — an inappropriate name, and contradictory 
Id name caput mortuum, which such residua ob- 

If heated to 300'^ in contact with t\ie aXxao- 
t takes Gre^ and burns with a lambent \Aue ^axckft, 

o 2 



I 



I 
I 



^B w 



whicli, 8B the beat rises, becoiuea whitish ; ei 
it burns, but so feebly [ha.C the quaotit; ( 
gunpowder may be all consumed without expl( 
tbis may be done by laying the gunpowder spread w 
on a moderately hot tile. Sulphur burns, in oxygen 
gHB, with a much more briUiant and a hgbier colooNd 
flame. In either case, the sulphur combines niA 
oxygen, and emits copious fumes, which are a c 
pound of oxygen and sulphur ; they are pungent to 
smell, and acid to the taste. We are acquainted with m 
leas than four compounds, consisting of these elemenn 
in difiereut proportions. 

SitlphuTOTie add. — -The ahoTe mentioned fumes ar 
the first compound; we know of no oxide of sulphur 
all the combinations puBsess acid properties. The en 
8t present under consideration, in conformity with dtt 
principles of nomenclature already explained, is CsIU 
sulphurous acid. When quite free from water, i 
gas at ordinary temperatures and pressures of the at- 
mosphere ; but when compressed into half its bulb, it 
becomes a hquid ; and the same happens by expoang 
it to an intense cold without pressure. Exposed to sif, 
this liquid acid evaporates speedily, and produces sadi 
a degree of cold, that the mercury in a thermometer tubs 
may be frozen by its means : it boils at 14^. The gH 
has a Etrong affinity for water ; it is absorbed by ^di 
of its bulk of water, and the solution thus formed is the 
same as what is commonly called liquid sulphurous add; 
but is perfectly different from the acid liquefied by coldi 
for the latter may contain no water. The gas may iB j 
expelled again from its solution in water by btriliHg- ■ 
This add comports itself differently from other Vait 
with regard to some vegetable colours; it instantly Mit 
dens the infusion of blue cabbage, but it dischaiges dx 
colour of infusion of the red rose. The gas bleadn 
various textures, as those of silk, wool, and straw ; tlK 
liquid acid bleaches sponge. It hears a red heat witlh- 
decomposition. 
When sulphur ia bomei in ijcrteci-j &n trasBmiw. 



3BiF. I. " SULPHUR. 197 

h, or oxygen gas^ no product is fonned but sulphurous 
idd; butt if moisture be present^ both this acid gas and 
ulphuric acid are produced. To generate sulphurous 
dd gas for experiment, mercury ox copper cUppings 
bould be boiled with strong sulphuric acid, in a glass 
etort, and the gas received over mercury, as water 
mold absorb it. When sulphur is burned in dry 
xygen, its volume, when cold, is so little altered, that, 
rere the sulphur quite pure, it is believed there would be 

alteration whatever. In fact, it is admitted, that sul- 
bnrous acid gas contains exactly its own bulk of oxygen. 

This gas has an exceedingly pungent smell j it is 
ital to breathe it undiluted ; it extinguishes flame ; and 

1 not inflammable. Its specific gravity, according to 
>avy, is 2'2293; according to Thomson, 2*22 1 : the 
lean is 2*2251 j and hence 100 cubic inches of it weigh 
8*5596 grains. If from this last number we subtract 
le weight of 100 cubic inches of oxygen, 33*9153 
rains, the remainder, 34*6443 grains, are the weight of 
00 cubic inches of sulphur vapour, such as exists in 
llphurous acid. Hence, I conceive the specific gra- 
Ity of vapour of sulphur must be 1*1244, and not 
'1111, as stated in chemical works. If we suppose a 
ohune of sulphur vapour and a volume of oxygen to 
sndense into a volume of sulphurous acid, the suppo- 
tion will just accord with the known specific gravity 
rthe latter; for 1*12444- 1*1007= 2*2251. 

Sulphuric add. — It has been already mentioned 
lat dry oxygen gas does not act upon dry sulphurous 
dd gas; but if water be present, a combination is 
fluted, and sulphuric acid is formed. The most in- 
tractive mode of making the experiment is the foUow- 
ig : — Pour some liquid sulphurous acid into a flat 
essel, and invert a jar of oxygen gas over the acid, so 
lat its surface may be in extensive contact with the 
xygen. After some time the quantity of oxygen will 
^n to diminish, and the liquid will slowly rise in the 
ur, until at length all the oxygen (if its c^\xax\\\t^ N^^a 
sctljr apportioned) wiR disappear. Tlie sui^Wtwx^ 

o S 



I 



I 



add is now totally altered : it has IobI i 
ameU ; it may be boUed without expelling any g 
ingCeail of Ulacharging the colour of tbe red n 
renders it more intensely red: it is now conTerteil iltto 
sulphuric acid, although very much diluted with water. 
If the liquid be boiled until its specific gravity became 
1-8+5, it ia then the strongest sulphuric acid that m 
be obtained. 

The process just described is very different from that 
made use of on the large scale for obtaining commercial 
Buiphnrio acid. Formerly it was procureil by the di»- 
tillatian of common green or white copperas^ thati!> 
sulphate of iron or of zinc. When sulphate of ironi 
exposed to heat in a retort, it first gives off water < 
crystallisation ; this was called phlegm of vitriol ; it il 
little acidulous : next conies a tolerably strong adli 
which was called spirit of vitriol; and, lastly, 
strongest portion, which, from its consistence, was caDn 
oil of vitriol : the latter part of this becomes solid, owiif 
to its great concentration, and was called glacial oil tf 
vitriol ; it possesses the property of smoking. Froll 
6 cwt. of common sulphate of iron, Bemhard obtained, 
by distillation, 52 pounds of dry concrete acid — {-ffsp- 
»»•« Wiegleb). 

In 1703, Homberg published a paper in the Meniffln 
of the Roya! Academy, in which he described a method rf 
obtaining spirit of sulphur by burning sulphur 
receiver. But this must have been done to great disadnn- 
tage; for Geoffroy infonns us, that by the process, 1 
pound of Bulphur sometimes yields 1^ ounce of the 
acid spirit, and this he considers a great product. Tbit 
it was then a great product, and the process a real im> 
provement, appears from. " The Booke of IHstUlatioiH," 
which gives the following method : ^Throw brim«t<HK 
in amali quantities Into a pan of earth or iron placed on 
the fire. Keep a bell glass hanging over it, but not so 
near as to confine the vapours, and thus extinguiab the 
Same. As the brimstone buma, wiy^Vj wiore; " a darit 
redoyle will collect, and diiacancmc'iiaX.Qtt-sii-^KMsia- 



•aAP.I. SULPHUR. 199 

•f brimstone you shall hardly gather one ounce of oyle/* 
Such was the produce two centuries and a half since. 
Homberg, however, was not the inventor of the im- 
proved process, for it is mentioned in Margraaf 's Ma- 
teria Medica Contracta, published twenty years before. 
In some time after, ComeUus Drebbel, a Hollander, 
discovered a method of obtaining 10 ounces of the 
^d spirit from a pound of sulphur ; but the process was 
kept secret. 

The next great improvement in the manufacture was, 

the discovery that, by adding nitre to the sulphur during 

the burning, the access of external air, which used to 

Carry off the acid fumes, was rendered unnecessary, and 

that a much larger product might thus be obtained. 

This had a considerable effect in reducing the price of 

the acid; from ^s. 6d. per pound, it fell to 1^., and 

then to lOd. ; a short time previously to 1758 it was 

leduced to 4rf. — (^Elaboratory laid open, 158.); and at 

present it is sold in London for scarcely more than a 

quarter that sum. A patent had been granted to some 

persons, a few years before 1758, for this invention; 

l>ut on the grounds of novelty they had no title to such, 

for the nitre process is actuaUy described by Lemery, in 

his C0UT8 de Chimie, 1713. 

Until I8O7, when the theory of Clement and Desormes 
was first promulgated, the practice throughout Great 
Britain had been to enclose a number of plates of iron, 
containing a mixture of one part of nitre to nine of sul- 
phur, in a state of combustion, in a chamber of lead, 
which was made as close as possible by means of water 
lute. This was done accordantly with the improvement 
above mentioned, of preventing the acid fumes from 
being carried off; but it will presently appear that the 
closeness of the chamber was of the greatest possible de- 
triment to the process, because it excluded common air, 
and because a crust of hard salt, which could not be 
broken, formed on the surface of the burning melted 
matter, and prevented perfect combustion. U^ to 1\\\^ 
pen'odj it was considered good produce to oVjtaixi ^^^ 

o 4 



p 



psTte br wei^ of i«l|>hiitic Mid &tm lipvi ot wlplnr'; 
uul ofun the aTenge pnd«ee liiil mc exceed v^ 
weighu. Bni u uon as tbr tbeciy of Cknicnl Hid 
Dt9onne« became known, the pe t c »iij of ilmitriBg lb 
atnunphere wu percdTcd; fakes were ap|Jied to ik 
baming matter; and sudt wai the eSect an the produce 
tbat from I pouod of solphor do lea* than S^ a 
3 poundit w^e obtained, and from 6d., to iitiicb the 
price had riEen, it was redaced to Sd. per pound. 

Instead of burning the mixture of snlpbiu anil nitre 
in the chamber, a stratum of water being laid on iti 
floor to absorb the acid fumes, the present pracliee is V> 
bam tJie mixture on tui iron pan, in a furnace outside 
the cbamber, so contrived that the fumes shall eaiet the 
chanibeT, and be there condensed in the water : no air 
paiaes intu the chamber but what goee over the bumilf 
nilphur. According to the old process, the crust of mIi 
from the pans o^en fell into the add, and rendaed it 
foul; this is prevented bj the new plan. If the coDl> 
bufllion of the nitre and sulphur be allowed ta proceed, 
too rapidlj in the furnace, there will be little or no toL 
phuric acid farmed in the chamber ; the sulphurous add 
and nitrous gas. will be perceived in the most remote 
chamber, without condensation ; and, perhaps, unaciiU- 
fled aulpiiur will be sublimed. Suppose tliat a chaige 
of 1 cwt. of the mixture of sulphur and nitre it 
burned at once, three such charges will be consumed 
every twenty-four hours ; a new une being added wbea 
the former is nearly Imrned out; each charge is to 
be oontinually rake<l, especially near the end of itt 
combustion. The water in the bottom of the chamber 
absorbs the fumes, and increases in specific gravity, A 
first more rapidly than afterwards : when it arrives at 
1-330, if it gain 3° of Twaddle's hydrometer (i. p. ips 
dfic gravity 0-015) ever)- day until it attain I-4.50, it 
ll accounted good work, the depth of the water being 5 
or (i inches, and the height of the chamber 12 feet> 
In some vjlrio) works, when tile acid reaches 1 '4-50, lite 
• lnintfiEiia)i,¥.*lS. 




GBAP. I. SULPHUR. 201 

impr^ation is discontinued ; it is then concentrated by 
evaporation in leaden boilers^ until it become 1'600. 
Al a strength very little beyond this^ the acid would act 
iqK}n lead; and so high is the boiling point become^ that 
the lead would be in danger of melting. On these ac- 
coontSj it must be transferred to glass or platinum retorts 
or matrasses, in which it is boiled down or distilled^ 
until it be of specific gravity 1*845, or 1'850. The liquor 
which boils off in vapour is at first water ; then liquid 
flolphurous acid ; and, lastly, sulphuric acid. The test of 
completion is, that the acid, originally deep brown, has 
become perfectly colourless. The cause of the brown 
colour is excess of sulphur; this decomposes the sul- 
phuric acid, and hence sulphurous acid appears : there 
is thus a waste, although but trifling. Sulphur boiled 
on sulphuric add, turns it blue, green, or brown, ac- 
cording to the quantity of sulphur. It is proper to 
observe that, in some factories, the impregnation of 
the water by the gas in the leaden chambers is con- 
tinued until the specific gravity be 1*()00; it is then 
transferred at once to the platinum retorts. 

The leaden chambers at length, but slowly, are cor- 
roded and wear out ; the sides and top most, the bottom 
least ; but most of all near the source of heat. I have 
known lead of six pounds to the square foot, to stand 
DDioderate work for fourteen years. About half a pound 
»f the combination of lead with sulphuric acid is found, 
after the perfect concentration of a retort charge which 
afforded 150 pounds of acid ; and a little more remains 
dissolved in the acid, which dilution precipitates. 

The residuum remaining after the burning of the 
sulphur and nitre is sold to alum makers, soda makers, 
and soap boilers. 

The following is the theory of Clement and Desormes, 
as improved by sir H. Davy : — '' The sulphur, by 
burning, forms sulphurous acid gas, and the acid in the 
nitre is decomposed, giving off nitrous gas ; this, coming 
in contact with the oxygen of the atmonphexe, igito^\xRft& 
'utrous acid gas, which has no action upon svj[i^\i\xTa\i& 



wtSd. Bf the hfgc fwtiiy mi wMcr mrnMj a 



, iceai diii g to diea^ friiriffc af e 

, dD dic«a*fr at Ae han^rf Ac 
. Il is fB^ to pMieAt 

_ a he nuxed Ugedier, bf mfetnig At 
m^dniront gto to paaa ima a ^bf* gUie puti>llTtf> 
haoBted. juid contaioing nitmis »ad ^s, dwre w31 k 
no acdon between tbe gases ; bat if a drop of nU* be 
introduEvd, there will be an unmediate condeosstioD, ud 
a beantifiil white crystalline Golid wiD line the iniour 
of the (esGel: whereas, if the glr>fae contain plmljrf 
wtier, lutroas gas will be giTen off with great vioieBC^ 
and the water will be found to be soladon of oil oT 
triol," It is eiident that the azote, which is contim 
accnmulating in the leailen chamber, must consttntlf k 
allowed to escape. 

The following are the chief properties of salpbnrie 

■dd : — WTien mixed with water, heat is gcDcrated. If 

the »dd weigh four times as mach as the water, ** ' 

both are at 50°, the temperature will rise to 300°, lad 

(here wilt he a diminution of volume. Such is Ae ■!• 

traction of this acid for water, that it will, when expoMd 

to the atmonpherej attract moisture from it, and itfl 

Qius gradually become much diluted. The greateat dfr- 

. sree uf concentration to which pure sulphuric acid can be 

I broughtbj'boiling, is apecilic gravity 1-845*; and eves *t 

dliK strength, every 100 parts weightcoiitain I8'S7 pM« 

' of water. The acid of commerce, as it comes from llie 

manufacturer, is l-S.'iO; but it is so in consequence of 

I. Jti containing salts of \ead, or of earlhK, or of poti^ 

• JVrcevsl, Irt>hTiint.W.B9.-,Bni 



QHAP. I. 8ULPHUB. 203 

It may be purified from these by distillation over a char- 
coal fire in a green glass retort^ on the bottom of which 
iome bits of glass or platinwn should lie, to prevent con- 
dnual concussions arising from the vaporisation of the 
icid under so heavy a liquid, which might endanger the 
iressel. The portions that first distil contain the water 
present, along with any sulphurous acid that may have 
Men generated by the accidental mixture of carbonaceous 
matter ; these should be rejected. The second portions 
bat come over will be very pure; but the phial in which 
t is kept must be well closed, to prevent dilution by 
ttmospheric moisture. Sulphuric acid, colourless when 
>ure, becomes discoloured by any carbonaceous matter 
'ailing into it ; a bit of cork would effectually blacken it. 
Boiling is the remedy; for the carbon is expelled as 
sarbonic acid, along with the sulphurous acid generated 
>y the abstraction of oxygen by the carbon. 

Sulphuric acid freezes when sufficiently cooled, and 
be crystals are sometimes large, distinct, and hard: when 
)f specific gravity 1-780, Mr.Keir found it to crystallise 
m being cooled in melting snow (32°) ; and if stronger or 
breaker, it required a greater cold : but the temperature 
)f the crystals, when formed, wa^ so high as 45°.* This 
loes not correspond with the extensive experience of a 
jcientific vitriol manufacturer, who informed me that 
be specific gravity of the acid which he found to freeze 
nost easily, is 1*835. 

Saxon or Nordhausen sulphuric acid is made in the 
bllowing manner : — Green copperas (sulphate of iron) 
8 calcined to a yellowish red ; it is thus freed from the 
ihief part of its water, and is reduced to half its weight. 
iVbile still warm, it is distilled from large earthen re- 
orts in a reverberatory furnace : it gives some acidulous 
pater; the acid then comes over. Its specific gravity is 
ometimes as high as 2*0. The distillation of a batch of re- 
orts often continues ten days. If the calcined copperas 
vere not immediately distilled, it would attract moisture. 
)uch is the process described by Gren and Wie^'efe. 

_ * PbUosophical lYansactions, by Hutton, &c. xv\. Snv 



304 BLBHEim or c 

This acid,' when exposed to air, discbargca nhi^ib. 
gray vapoure, whidi are not sulphurous acid, is fonneil; 
supposed, but real dry sulphuric acid. Acid of spedh 
gravity 1-896 contains about ^'jth of water; and i» 
so voiatUe, that it boOs al 120= — (Thomson.) If ilbe 
distilled into a receiver cooled irith snow, the fiimiDg 
portion comes over first, and concretes into & Ktoww 
solid Ukt. ntheslw, which is far more volatile than eta, 
and is pure sulphuric acid ; all the water remains Id 
the portion contained in tbc retort, which is now conu 
mon sulphuric acid. 

From these facta it therefore appears, that perfecdy 
pure and anJti/droa» • sulphuric acid is a white solid 
substance.so extremely volatile, that it discharges vq 
of sulphuric acid into the air ; these attract moisture. 
both condense into visible paitJcles: and that, if to 
81-63 parts of it, I8'37 parts of water be added, bodi 
bj weight, the result a ordinary sulphuric acid, which, 
instead of being volatile like the original, requires a hMt 
shore 600° to make it boil. Further additions of w««f 
tender it more volatile ; but it is obvious that the boiling 
point can never fall lower than 212°, be the acid em 
so dilute, although the pure acid boils below 120°. The 
solid acid. Dr. lire says, if dropped on paper, will hum 
holes in it with the rapidity of a red-hot iron ; dropped 
into water, it hisses as if a red-hot coal were thrown in: 
Bt 64° it melts into a thin liquid. The analysis of sul- 
phuric acid is readily performed in the manner pointed 
out by Davy. Let the strongest acid of commerce be 
passed in vapour through a red-hot porcelain tube; put 
of it will be decomposed into two volumes of aulphuroui 
acid and one of oxygen. The water, with which the 
decomposed acid had been in combination, will mig with 
the portion of acid which escaped decomposition. Sul- 
phuric acid is, therefore, composed of two volutna of 
lulphurous acid and one of oxygen, condensed into ■ 
liquid. 300 cubic inches of sulphurous acid wdgb 



^_ uquio 



cmp. I. SULPHUR. 205 

137*1192 grains^ an equal volume of which is oxygen^ 
and weighs 67'S306. The 200 volumes of sulphu- 
10U8 acid^ in becoming sulphuric^ take up 100 cubic 
indies of oxygen^ weighing 33-9153 grains; which, 
added to the oxygen aheady in the sulphurous acid, give, 
as the total oxygen, 101*7459 grains: but, in the 200 
cubic inches of sulphurous acid, there are 200 cubic 
inches of sulphur vapour, weighing 69*2886 grains. 
Hence, sulphuric acid consists of 101'74<59 grains of 
oxygen and 69*2886 grains of sulphur; and, conse- 
quently, 100 grains of sulphur combine with 146*843 
grains of oxygen, to form anhydrous sulphuric acid : or 
200 volumes of sulphur vapour combine with 300 vo- 
lumes of oxygen, the volume of the latter being 1 J time 
as much as exists in sulphurous acid. 

Hyposulphurous and Hyposulphuric acids. — Beside 
sulphurous and sulphuric acids, there two' other com- 
binations of sulphur with oxygen which contain a less 
proportion of oxygen than these acids respectively, and 
they are both acids ; hence, one is called hyposulphurous 
add, and the other hyposulphuric acid. To produce the 
former, 100 parts, by weight, of sulphur combine with 
24-474 of oxygen. To form the latter, 100 of sulphur 
combine with 122*369 of oxygen. Hyposulphurous acid 
has been obtained in an uncombined form ; at least, in 
combination only with water ; but, even in a few hours, it 
undergoes spontaneous decomposition. Hyposulphuric 
acid has been procured in solution in water, the specific 
gravity of which may be raised, by evaporation, to 
1*347; but, if the heat be continued beyond this den- 
sity, the liquid is resolved into 4 parts by weight of 
sulphurous acid gas, which exhales, and 5 of sulphuric 
add, which is the only remaining product. Hence 
these relative quantities of tho two acids, combined, con- 
stitute hyposulphuric acid. 

Suhsulphuraus acid There is one more compound 

of sulphur with oxygen : it contains a quantity of 

oxygen^ intermediate between sulphurous and \i^'^osa\- 

pbuwus add; and is called by Dr. Thomson, -wVxo ftx^X. 



I 



pointed oat ils exact nature, evhuulpburous idd, B 
containing a lower ratio of oxygen thati wbal is con- 
tained, in sulphurous acid, and yet distinguished from 
thai in which the ratio is still lower, viz. hyposuljAH- 
tous acid. In subaulphurous acid^ 1 00 parU of suljihor 
are combined with 4.8-948 [larla of oxygen. The fd- 
lowing table shows the compoEilion of die compoundBof 
sulphur and oxygen by volume and weight : — 






HfiiotuJphurii 



Ox. Sulph. 



f IJX) CI lOO • 



tMM 



The ratio of oxygen in these compounds is as tbff 
numbers 1, 2, 4, 5, 6. Were a compound hereaftar 
discovered in which the volume of oxygen would be 75, 
we should then have the series of natural numbers com- 
plete. In all probabiUty such a compound exists. 

Sulphuretted hydrogen, or Hyrlnmilphtiric acid.— 
Sulphur has an affinity for hydrogen, and unites with h 
in two proportions. If sulphur be healed in a flask of 
hydrogen, the latter dissolves some sulphur, and a gat 
18 produced by the union, wliich has an intolerably fedd 
Bmell, resemhling that of eggs in the last stage of putre- 
foction ; indeed, the smell of putrid eggs ia owing to the 
emission of this gas. But by this process the hydrogen 
does not take the quantity of sulphur which would be 
necessary to form even the first combination ; about half 
of the hydrogen remains altogether unchanged. In 
order to procure the perfect combination, hydrogm 
must he generated in contact with sulphur ; and, while 
in the nascent state, it will saturate itself in the first 
degree. The substance sold by druggists under tike 
name erude antinumy, or sulphuret of antimony, ia a 
combination of sulphur and the metal antimony; if 
strong muriatic acid be^ heated on this substance, in 
weight about six or aefeu limeR "A^a^ of the antimony, 
an effervescence will t».Ve yXace-, ^l■ii^lo?,t^i -«a \» 



CHAP. I. SULPHUR. ?07 

formed ; and it will instantly saturate itself with sul- 
phur^ so far as to form the gas in question. This 
compound is sulphuretted hydrogen. It is collected 
over water, in vessels filled with water in the usual 
banner. But as little water as possible should he used, 
^ it absorbs 3'66 times its bulk of the gas, and occa- 
sions so much waste. The gas is, at the same time, 
purified from any muriatic acid fumes which might 
*iave passed off along with it. Water, thus impreg- 
nated, is found abundantly in nature ready formed ; it 
^^nstitutes the sulphurous springs of Harrogate, Aix- 
^a-Chapelle, Kilburn, &c. The sulphuretted hydrogen 
*iiay be expelled, unaltered, by boiling the water. 

If a stream of sulphureted hydrogen be passed 

through water tinged with a vegetable blue, the colour 

is changed to red, in the same way as it would be were 

Carbonic acid passed through it, or any other acid. This 

^as combines with other bodies, and comports itself hke 

a.n acid, except that its taste is not sour. Some years 

since, when chemists imagined that oxygen was the 

acidifying principle, and that nothing could be an acid 

•that did not contain it, the properties of sulphuretted 

■hydrogen were considered anomadous and irreconcilable. 

Now it is ascertained that, to constitute acidity, oxygen 

is by no means necessary, and hydrogen is known to 

produce acids in conjunction with other bodies. 

Sulphuretted hydrogen has been named by the Ger- 
mans hydrothionic acid (peiov, sulphur) ; the French 
call it hydrosulphuric acid. If 100 cubic inches of it'*' 
be mixed with 150 cubic inches of oxygen, both dry, 
and an electric spark passed through, an explosion takes 
place, water is formed, and the 250 condense into 100 
cubic inches of sulphurous acid. Now, hydrogen, in 
combining with sulphur, does not alter its volume ; it 
is, therefore, evident, that 100 cubic inches of sul- 
phuretted hydrogen contain just the same volume of 
hydrogen. To form water, the 100 cubic inches of 
hjdiogen must have removed, and coinb\i\e^ mxXv ^^ 
^ubJc inches of oxygen ; leaving 100 cubic mOtte^ q?1 




I 



gm if wOfbai, miwwiIiil ib 34^6143 gtaiu: it d 
m a mW a t ifau dnt tm Ae vc^it itf (Hlphor conluwl 
m the aiginal 100 oibic inchci of ralpfaurettedlif* 
Avgca ; aad if dw wd^t of 100 odiic inches of ^- 
Jfog H i, vtx. S-IltfTgniUBiWhich U die «hcJe qnintilj 
ariemallv present, be added, we then have 3()-764 grvni, 
■• die wdgfat of 100 cuIhc incbes of Eulphiueraed hj- 
diogen. From dm, bj die rule of diree, we calculilC) 
tb*t, aa 30*8115 grains of common air (die wagbt tf 
100 cuUc iaclies of il) tie to 36'Gi grains {At 
wogtit of the Bame measure of sulphuretted hjrdrogen), 
BO win the nomber 1-000, or nnity, be to the omabv 
exprening the specific gravitjr of sulphuretted hjdiugo^ 
or 1-1931. This is the calimlated specific gravit; ; (S- 
periment has ^ven the uainber aimOBt exactly the nnit : 
Gay-LuBsac and Thenard found it I'lJUa.— (TAfflwrd, 
TraW ElSmenlaiTK, L 234.) 

This gag neither supports combaadon nor life ; it ii 
one of the inoBt poisonous gases known ; experimaitl 
have been made which prove that so small an admuttuM 
as ^^fif' "f '' ^^h common air is capable of killing I 
borae, if breathed ; a ^eenfinch inslandy died in air 
containing i^^th of its volume : and it lias been showD, 
that enveloping the body of a young rabbit in nd- 
phuretted hydrogen, die head being in the open afrj 
killed it in a quarter of an hour. It extinguishet 
flame instantly, but easily catches fire from a cand)^ 
ami burns with a bluish flame, provided that te 
Jet of ga« is in contact with air. A few drops of 
•trong nitric acid let fall into a vessel filled with sut 
phuretted hydn^en, sets fire to it. I Bufii;red a severe 
li^nry from an accident of this land, twelve years mnc^ 
long before Berzelius announced the accension of si^ 
phurettmi Jiydrogen by n'lWic adA. 1 l\ail poured mn- 
rinio neid on aulphutel ot i«h.\too^t i» "■ ■««n ^«^ 



QBATV V flULPHUB. S09 



; and while the vessel was partly filled with sul- 
plraretted hydrogen^ and partly with common air^ I 
pooled in a little nitric acid^ when instantly the ma- 
tnsB was shattered^ and my hands were severely in- 
jured. In such experiments the two acids should be 
prenoosly mixed^ before they are poured on the sul- 
pimret 

Sulphuretted hydrc^en may be easily rec(^ised^ even 
when largely mixed with other gases^ by its power of 
Uaekening silver^ and the dry powder called white lead. 
The wood- work of rooms^ painted with white lead^ is 
ofWai darkened by human exhalations containing this 
gM; and articles of plate are blackened by the same 

This gas may be condensed by pressure into a liquid ; 
bat it recovers die gaseous state^ with energy^ when the 
pKSBure is removed. 

BistUphuretted hydrogen, or Hydroguretted sulphur, 
— This compound contains twice as much sulphur as 
the preceding ; the following is an easy process^ given by 
Dalton^ for obtaining it : — Let half an ounce of flowers of 
sulphur, and as much slaked lime, be gently boiled to- 
gether in a quart of rain water for one hour ; more 
water may be added as it evaporates. After cooling, a 
dear yellow liquid is obtained. To six ounces of this 
liquid put half an ounce of muriatic acid, and stir them. 
In a diort time the mixture exhibits a milky appear- 
ance, and this becomes interspersed with brown oily 
dots, which gradually subside into an adhesive matter 
of a semiliquid form at the bottom. The liquid may 
then be poured off, and the brown matter washed with 
water, which is to be poured off. From 20 to 40 grains 
of this brown oily substance will be obtained. ^^ If a 
portion of it touch the skin, it requires a knife to scrape 
it off. When a little of it is applied to the tongue, a 
sensation of great heat, and a bitter taste, are felt ; the 
saliva becomes white like milk." When heated, sul- 
phuretted hy driven exhales, and sulphur iemam&. \ec^ 
ittle 18 known of the nature of this compoMud ; \\. \a ^ 

p 



810 



feeble adii, and combines with aikaline 
Froro Thomson's experimente it miy be inferred, (hit, 
to form bisulpburetteil hydrogen, 100 parts, by weight, 
of Bulphur, combine with S-OSpS of hydrogen. Tlut 
quantitji of hydrogen would require but ^0 parte d 
sulphur to form sulphnretted liydrogen. 

BimiphurBt of carbon. — Sulphur combines willl 
carbon, and forma a liquid which formerly had ibe 
absurd name of alcohol of nulphur, but is now ctM 
bitvi^nret of carbon. It may be formed by diedlling 
the mineral called iron pi/ritm, mixed with one fifth at 
its weight of newly burnt charcoal, both in fine powdUi 
from a stoneware retort, coated with Stourbridge diy, 
and placed in a furnace. The beak of the retort is to ban 
■ long ^ass tube luted to it, one end of which plangH 
into a vessel of water. By a strong heat a jditm 
liquid distils over, and falls to the bottom of the waW, 
from which being separated, it is re-distilled in a ^us 
retort with a very gentle heat. Thishquid is sulphurel 
of carbon. 

When thus rectified, it is transparent and colourlew; 
its boiling point is about 10S° ; its specific gravity is 
about 1-266: when exposed to air, it evaporates n- 
■ pidly, and produces intense cold, such is its volaliliff^ 
If a thertnometer tube, with a bit of muslin tied rouD^ 
tbe bulb, be dipped in this hquid, then included in an 
air-pump receiver, and the air exhausted, the ev^MI- 
Btion produces such cold that the mercury freeiM' 
And if a few drops be difliiBed on the surface of a ^M 
of cold water, the bisulphuret will begin to evapanU 
so rapidly, and such cold will be produced, that whit* 
ever remains will become cased in a shell of ice. It I 
takes fire at a temperature very little above that of 
boiling mercury, bums away, and is resolved into cat' 
bonic and sulphurous acids. Its vapour, if mixed wiA 
oxygen, explodes by the electric spark with considerable 
noise : and if mixed with deutoxide of azote, and 
(ransiiiilted through a jet-'pVvw, 'W, \i'aiM, -with a some- 
wbMt greenish beauliM \is\ii. 1.^. toftTOXsee. -aKi^, 



OBAT. I. SUIiPHim. 211 

<Qd is converted into a substance resembling campbor^ 
b^ the action of a mixture of nitric and muriatic acids. 
It dissolves in aloobol and ether^ but not in water. It 
appears to combine witb alkalies and eartbs. Its smell 
is stroi^ and fetid. 100 parts by weight consist of 
84'83 sulphur and 15*17 carbon. 

Xanthogen and Hydroxanihic acid. — Although hi. 
iolphuret of carbon does not appear to be an acid^ 
) combination of carbon and sulphur is capable of 
kiting as an acidifiable base^ and forming an acid when 
iombined with hydrogen. In this case^ the combin- 
tion of sulphur and carbon constitutes a compound 
adical^ no doubt different in the ratio of its elements 
rom die bisulphuret; and^ when acidified by hydro- 
en^ is to sulphuret of earbon what hydrocyanic acid 
\ to cyanogen. On account of the yellow compounds 
rhich this combustible radical is capable of producing 
rith certain metals^ it has been called xanthogen (from 
xvBo^, yellow), and to the acid which it forms by 
^mbination with hydrogen, the name hydroxanthic 
(dd has been given. It has also been called hydro- 
irbosulphuric acid. 

Dr. Zeise, professor of chemistry at Copenhagen, the 
iscoverer of this acid, states, that although bisulphuret 
F carbon does not redden litmus, it neutralises an alco- 
olic solution of a pure alkali : for the alkali determines 
16 formation of hydroxanthic acid by the re-action 
r itself and the alcohol. If a concentrated alcoholic 
^hition of potash, neutralised with bisulphuret of car- 
)h^ be mixed with diluted sulphuric acid, and in a 
rw moments after with a large quantity of water, a 
ansparent, oil-like, yellow, strong-smelling liquid, is 
(parated, which should be immediately well washed 
ith water. This is hydroxanthic acid. Its taste is 
id, and then astringent and bitter. It reddens litmus 
iper, and then changes it to yellowish white. It is 
soluble in water, and is specifically heavier than that 
lid. It Is easily ind&med, and while "buiivm^ ^- 

p 2 



I 



' S13 BLEMENTB 9F 

fiiscB the smell of Eulphurnus acid. It is ieawfOni 
by heat. — (^Annalea de Chim. ei de Phj/a. xxi. I6O.) 

There are two other Bcids known, which are cam- 
pOBcd of the Bame elements aa hydroxanUiic uid, 
although very UiBBirailar in their properties : they ire 
called vegeto-tulplixtrie acid, and sulpho-naphthalic acid. 
It will save space to refer vegeto- sulphuric aeid to 
fttture coneideration. 

Sulphimaphtltalic acid is ubtained by causing strDDg 
Bulphuiic acid to act on naphthaline. A red cryBtalline 
compound results : this is dissolved in water ; the solu- 
tion is saturated wilh baryta: sulphate of baryta pred- 
pitates, and, being separated, the solution of sulphti- 
naphchalate of baryta is decomposed by sulphur' 
and filtered. This liquid is the acid required. When 
the water is removed, it becomes a white, deliqueieenl, 
easily fusible solid, of an acerb acid taste. It is eoBi- ' 
posed of carbon, hydrogen, and eulphuric acid : die Mp j 
turating power of the sulphuric acid is reduced toliilf I 
by combination with the carbon and hydrogen. ' 

StiiphureU of cj/anogen and Sulphocyamc aeid.-~~ 
Sulphur combines with cyanogen in two proportion^ 
and forms two distinct compounds. To form the HtM, 
100 parts of cyanogen combine with 31 of sulphni; 
but iu the second compound there is four times that 
quantity of sulphur. The latter sulphuret of cyanogen 
is known to act the part of an actdifiable base, and b/ 
combining with hydrogen to form an acid, whidi it 
called kydrosutj^ocyanic add, or, simply, ruipAocjionlO' 
This acid ia capable of crystallising at a very low ton- 
perature ; its smdl resembles that of acetic acid ! it> 
taste ia sour. But its chief distinguishing property I* 
its producing a deep blood-red colour when dropped 
into any solution which contains peroxide of iron : the 
two substances act as tests of each other's presence. 
This acid combines with sulphuretted hydrogen, and 
forms hydrosvlphuretted iuiphoci/anic acid. 

CA/eride qf aul^mr li a ^bm ftst^t \« €«ed with 



COAT. I* SELENIUM. filS 

dry dblorine^ and a bit of sulphur introduced^ they will 
combine if heated^ and form a reddish coloured liquor^ 
which smokes in die air. Its specific gravity is 1*700 : 
it boils below 200°. It does not manifest acid pro- 
perties. It decomposes water^ the oxygen of which 
combines with some of the sulphur^ forming sulphurous 
and sulphuric acids ; the hydrogen combines with the 
chlorine^ forming muriatic acid^ and some sulphur is 
precipitated. 



Section IX. 

SELENIUM. 

The substance now to be considered is nearly allied 
to sulphur in its nature^ although it in some respects 
partakes also of the nature of a metal. There is a 
.copper.mine in Sweden^ near Fahlun^ celebrated for its 
antiquity^ and its enormous produce. Besides copper^ 
.the mine affords vast quantities of iron combined with 
lolphur^ and to such extent^ that it has been found 
worth while to extract the sulphur^ although it is ex« 
ceedingly impiure. The sulphur is consumed in the 
manufacture of sulphiuric acid. After the combustion 
and acidification of the sulphur^ and the absorption of 
the acid fumes by the water used in the process^ a 
reddish brown substance is found to subside^ consisting 
of .a great proportion of sulphur mixed with other in- 
gredients. If some of this reddish brown substance be 
strongly heated^ it emits a pungent smell resembling 
that of horseradish. 

By complicated processes^ it is possible to separate 
the odorous substance from the reddish brown matter. 
This substance seems to partake of its sulphurous 
origin ; for it in many respects resembles sulphur in 
its properties : and^ on the other hand^ it possesses so 
much of the metallic character^ that its diseo\eieT,^^T. 

p 3 



I 
I 



zelius, did acCuaUy pronounce it a. meul. At finllu 
mistook it for the metal called tellurium ; bnt aflerirari! 
he ascertained that they are different aubstancM, yd 
resembling each other in some of their qualities. Td- 
lurium having been so named from lellus, the Lion 
name of our planet, Berzelius named the new meMl, » 
he conaidered it, selenium, from o-tJ-ijuj, the moon,— 
thereby Buggeating the relation of the two metals liy tl« 
relation of the two planets. 

Since the discovery of this subetance, il has been 
found in the pyrites of the isle of Anglesey, and m; 
be detected in the sulphuric acid manufactured frtwi 
the sulphur extracted from that mineral. It has beoi 
also found in the sulphur of other countries. | 

Selenium, under certain circumstances, has conddet- I 
able metallic lustre ; hut it has not the opacity of ( I 
metal ; for, when reduced to thin plates, it is semitram- I 
parent. Unlike a metal, it is a non-conductor of elee- I 
tricity ; and, unlike sulphur, it is a non-electric. Iti 1 
colour varies according to circumstances : if examinEd | 
by transmitted light, or, in plain terms, if hoked tAjwiji 
as a transparent body, it appears reddish ; but if seen 
by reflected light, that is, looked at in the ordinary 
manner of opaque bodies, it is leaden gray and brilliaot. 
It breaks with a vitreous fracture, somewhat like sul- 
phur ; and it may be reduced to a powder, which is red 
coloured. Like «u1])hur, also, wlien subjected, to heat 
h) a larj^e glass globe, it subhmes into flowers, but of t 
reddish brown colour ; while in vapour its colour ig 
yellow, somewhat like the vapour of sulphur. At the 
temperatiu'e of 212°, it softens; and if heated a little 
more, it melts : at a little above 600° it boils, and 
distils over into drops of a metallic appearance. When 
it has been fully melted, it will preserve, while cooling, 
a certain degree of ductility, and may be drawn out 
into threads like sealing-wax ; and these have a metallic 
lustre, although somewhat transparent. It is insoluUe 
4n water, lis specific graiil^ is V^W. \ti the flame 
'the blowpipe it i^Bap^eaw, coTQm\ni\ia.'a'D.%B.'a.MNii». 




' Arip. I, SELENIUM. 215 

oidoar to the flame^ and a highly diffusible smell of 
kraeradish : such are its characteristic qualities. 

(kride of selenium, — Selenium combines with oxygen^ 
<Qd forms an oxide and two acids^ the properties of 
which have not been fully ascertained. The oxide exists 
in the form of a gas. It may be produced by heating 
selenium in a flask of common air. 

Selenious add may be formed by passing oxygen over 
Selenium heated to about 600° in a small vessel, from 
idufih it oumot readily escape in vapour ; the selenium 
■Bm nve, ffinwHiwwifli oscyigen, •nd'fcmM the4Mid in 
question. It sublimes into crystals, the form of whidi 
lomewhat resembles those of nitre. While in vapour, its 
colour is yellowish green, resembling chlorine. It is 
very soluble in water and strong alcohol ; the taste of 
its solution is acid, and a little acrimonious ; its aqueous 
Bcdution, when concentrated, crystallises. The same 
add may be formed by the action of nitre or nitromu- 
riatic acid on selenium : a solution is effected ; and this, 
when evaporated to dryness, affords a white mass of 
fldenious acid, which may be crystallised either by sub- 
limation or in the usual manner. 

Selenic acid. — By means of a new addition of oxygen 
to selenious acid we obtain selenic add : and here, again, 
is observable the resemblance of selenium and sulphur ; 
for selenic acid possesses many of the properties of the 
sulphuric. Selenic acid is decomposed, at so low a tern. 
perature as 536^, into selenious acid and oxygen. When 
mixed with water, it causes a considerable elevation of 
temperature,, just as sulphuric acid would. If to its 
aqueous solution some muriatic acid be added, and a 
plate of zinc or iron be immersed, selenium is reduced 
in the form of a powder, the colour of which varies. 
This precipitation, by means of a metal, corresponds 
with the pseudo-metallic nature of selenium. To form 
selenious acid, 100 parts of selenium combine with 40 
of oxygen ; and with 60 to form selenic acid. 

Seleniuretted hydrogen. — Another poitvt oi xesettM^^wsfe 
subsisting between selenium and sulphviT \^, \)ftaX\»^ 

p 4 



I 

I 



bodies combine with hydn^n, sad form a feiid fft, 
which jKtsflesBos the properties of «ii add. Bj srnng 
on a combinsdon of selenium nrjih iron or polB£Uiiiii,by 
means of muriatic acid somewhat diluted, a combintaoii 
of hydrogen with Eelenlum will be evolyed in the fonn of 
a transparent and colourless gas. One of its most stiit 
ing properties is the effect which it produces when cm 
the smallest quantity is snuffed up the uostiils: iheiel! 
a painful irritation produced, which gradually diffiun 
itKelf down the throat, accompanied by a temporary Ion 
of the sense of smeUing, a violent cough, and conads- 
kble expectoration ; all of which unpleasant efSscU con- 
linue for many days. It is the opinion of profeus 
Berzelius, that to inhale much of this gas might be I 
dangerous experiment. 

This gas, in conformity to the names giren to other 
combinations of hydrogen with inflammables, i* ciBal 
iekniuretlerl hydrogen. Its smell resembles that of nl- 
phnretteU hydrogen. It consists of 1 00 parts of Beleniim 
combined with 2-5 of hydrogen. It is copiously absorbed 
by water; and the litjuid produced, like sidphurett«d 
hydrogen, poBsesses the proporiies of an acid, and pre- 
cipitates metallic salts ; it siains the eldn of a brown 
colour. Selenium combines with sulphur, chlorine, and 
c»rbon. ^^ 



This well known substance, though sold at the loir 
rate of 3». per ounce, is prepared by an exceedingly 
diificult process, Several methods of preparation have 
been given, all of which have their disadvanlagei. 
Macquer gives, from Hellot, a process which occnpiei 
■even pages. To make an ounce of phosphorus, the 
firet Blep is to evaporate three hogsheads of fetid urine 
to drynem. This specimen \a eno\j.^\v ■, \i. ia not neces- 
sary to describe the procesii iurtVci, 



<aBAP. X. FH08PHOBU8. SI 7 

liiat Schede's method of making it from bone ashes 
was uniyersally employed as soon as discovered. But 
even this mode is wasteful and excessively troublesome. 
Bone ashes^ decomposed by sulphuric acid in the man- 
ner hereafter described^ are but partially acted on: much 
of the bone remains unaltered^ unless a large ratio of 
sulphuric acid be employed ; and this excess gives rise^ 
in the common process^ to much trouble^ loss^ and dimi- 
nution of the product. 

In order to obtain phosphorus^ prepare pyrophos- 
phoric acid* from bone ashes^ in the manner hereafter 
described. It must be perfecfiy dry^ and immediately 
reduced to powder in a hot mortar, and mixed with half 
its wdght of newly made charcoal in fine powder. An 
earthenware retort must be in readiness, rightly pre- 
pared : its pores must have been closed by washing with 
a mixture of two parts of finely powdered borax, one of 
powdered lime, and a little water ; so that a coat of glass 
will be formed on it during the incandescence of the 
vessel. It must then be evenly coated over with a mix- 
ture of Stourbri(%e clay and pounded crucibles, mixed 
with cut tow and a little water, and allowed to dry slowly. 
The retort, charged with the above mixture, is placed 
in an air-furnace, with an opening before to admit the 
neck, which should have a wide copper tube, 20 inches 
long, luted to it; the other end, to prevent access of air, 
being immersed in a basin of water so as to be barely 
covered. The belly of the retort is supported on a 
brick lying on the bottom of the furnace. The fuel, 
compactly disposed all round the retort, must now be 
kindled; and the heat, kept very moderate for two hours, 
must be increased until it become fierce. Much gas 
bubbles from the surface of the water, which bums bril- 
liantly when the bubbles burst in the air : lambent lu- 
minous fumes undulate through the air over the water 
in a singular and beautiful manner; and at length vapour 
of phosphorus condenses in the copper tube, which must 

* Tb^ is the subetance that was formerly caUed glacial phosphoric oc»A. 




I 



«f arwtj AkilM pfa^bOTw, ■• to ife de^iw of «Utt, 

MlM,acmC^iDDr.n^«M:bu AisMMttAl 

dMar. ItuiBflttljMtaUeiBlxitlifixEdBidiidataedt 
to alcobol and ether. It fadh at 554", tet, in a Tamil, 
enpome* gradnallf at 219'. IiscpceificgraTitf ial-71& 
ll l« capaUc «f ciynallinng into ocuhednns. or. as oCboi 
nj, into ilodecahedronf. Friction or patrnsnoo »tt 
Are to it. l«tten or lines traced with it appear limiB- 
0III in the dark : bat there is danger in the tracing, n 
ibe phMpfaonu often tak^ fire, and bj melciitg faUs en 
liv penon* clothes, and it is almost impossible to ex> 
tingnish it : the best waj is lo smother the flame with 
■ rrry wet cloth held firmly pressed on the part. It 
may be distiDed in a retort, if the air be o^hausted : tUt 
method annwers for purifying tt from ebarcoal, wUfiti 
gmerally fonlo it when fim distilled : but an easier 
method Is to lie it up in a piece of glove, or alum-leathcTp 
to Imroersc It in cold water, and gradually heat the wata 
until the phcwphoruB me\is-. Ai"j \>t»«vtv?, iiLt\e«laosi 



<9Ay. I. PHOSPHORUS. SI 9 

lig under water^ the phosphorus will strain through the 

pores quite pure^ in the same way as mercury would. It 

should be preserved under water ; as, even at ordinary 

temperatures^ it undergoes a slow combustion in the air. 

Hiosphorus bums in common air with a brilliant white 

tigfat^ but in oxygen gas the combustion is transcendently 

Inilliant : white fumes are formed in abundance^ which 

condense into a solid acid. When introduced into chlo- if«., 

rine at ordinary temperatures^ it takes fire also^ and burns 

with splendour : a smoke arises^ which condenses into a 

dry chloride. According to Dr. Bache^ of Philadelphia^ 

it is inflamed by powdering it with animal charcoal at 

60^. Its combinations are very numerous. • 

The compounds of phosphorus with oxygen have been 
investigated by several chemists of eminence^ but the 
knowledge of them acquired is not commensurate with 
the labour that has ^been bestowed on them. It is^ as 
yet, mere matter of supposition, that phosphorus com- 
bines with oxygen so as to form an oxide. But it readily 
forms compounds which have decidedly acid properties. 
Three such are known : they are called, 1 . Phosphoric, 
of which there are two varieties, phosphoric and pyro- 
phosphoric acid ; 2. Phosphorous ; and, 3. Hypophos- 
phorous acids. 

Phosphoric and Pyrophosphoric acids. — When phos- 
phorus is exposed to common air, at its ordinary tem- 
perature and degree of moisture, it undergoes a slow 
combustion, and absorbs oxygen : it is luminous in the 
dark, and emits luminous smoke, which has a strong 
odour of garlic: the surface becomes moist, for the 
moisture of the air is absorbed as well as the oxygen : 
the moisture trickles down; more is formed; and at 
length the whole is transformed into a dense liquid, of 
an exceedingly acid taste. This has been by some con- 
sidered a distinct acid, and it obtained the name of phos^ 
phatic or hypophosphoric acid. It is at present, however, 
believed to consist of a mixture of phosphoric and phos- 
phorous acids. The higher the temperatuie ^X. \5\\v3cl 
this process is conducted, the more speedily t\ve ^-axv^t^^ 



I 



I 



I 



and the quantity of acid will be greater, u ' 
be kept OTcr the phosphorus, the coDlain^ 
; ofleu renewed. In order to convert thie deiw 
add liquor into pure pboBpburic acid, expose it in n sLtle 
of considerable dilution fur s long time to the air, in 
order to absorb osygen ; or, ajid nitric acid to it in pro- 
portion of one twelfth the weight of the original pbw- 
phorus ; evaporate by heat ; oxygen is taken from tk 
nitric acid, \rhen the mass is dry, expose it to a rd 
heat for a few moments in a platinum crucible. Tbe 
resulting substance is the variety called pyropbosphonc 
add. Jf it be dissolved in water, end the solution Ivd 
by for some days, it is converted into phosphoric add, 
although not the slightest change has been produced in 
the elements or their ratio. 

Another process, less tedious, but not so safe withotil 
great caution, is to throw bits of phosphorus, not exci 
ing the size of small shot, one by one, into warm mtiu 
add, waiting each time until (he effervescence ceaie. The 
phosphorus should not exceed one twelfth of the we^ 
of the nitric acid : the former takes oxygen from diC 
latter. Shoidd the chemical action become violent, the 
vessel must be immersed in cold water. When the 
loludon is complete, it must be evaporated to drynesi, 
heated to redness in a platinum crucible, and treated as 

A much more economical method of preparing phos- 
phoric acid in the large wayi when the ultimate object 
is the preparation of phosphorus, or when the acid ii 
not required to be chemically pure, is the following : — 
Sifiiise SO pounds of powdered white bone ashes in 20 
gallons of boihng water; gradually add 10 pounds of 
aulphuric acid diluted with 10 pounds of water, and 
keep the mixture stirring until all apparent action cease. 
Throw the whole into a cotton filtering bag, and occa- 
Bionally press the sides of the bi^ so as to agitate iix 
mass, and let 10 gallons more of water run throo^ 
to wash out the acid. 'NeaUt^u^ 'i^ 'scid. liquor 
irith carbonate of wnmomB. ■, a,tvl Nrtiea \.\. Asw*. &msl 



3^AP. I. PHOSPHORUS. 221 

md evaporate in a leaden boiler to a small quantity, 
^oor this matter^ while hot^ into a thin glass balloon^ and 
»lace it on sand in a reverberatory furnace. Continue 
be heat until the bottom of the balloon is red. A hard^ 
!olourless^ transparent phosphoric glass will remain^ 
^hich. by breaking the balloon, may be easily detached.* 
niis L j^yrophosfhoric acid, 4hich, by being dissolved 
n water^ and laid by for some days^ becomes phos« 
>horic acid. 

From all that has been ascertained on this subject^ it 
vould appear that phosphoric acid is only known as 
ixisting in the liquid state. If it be evaporated^ and 
leated to such a temperature as may be judged capable 
»f expelling the chief part of the water^ it is changed 
nto pyrophosphoric acid : and the same change takes 
)lace when the acid exists in a salt combined with an 
Jkali. Although between phosphoric and pyrophos- 
)horic acid there is no known difference of composition^ 
;he properties of each are essentially different. Pyro- 
phosphoric acid produces, with oxide of silver, a white 
(alt ; phosphoric acid a yellow one : the former is a less 
mergetic acid ; it has less saturating power, and is even 
separated from its combinations by phosphoric acid, 
rhis is another proof of the position laid down in other 
parts of this volume, that bodies of the same compo- 
sition with regard to relative quantity and identity of 
elements, may be quite different as to properties, in con- 
sequence of some unknown difference in the manner in 
nrhich the constituents are combined. The name pyro- 
phosphoric acid is given to this substance, to indicate 
Jiat it owes its origin to the action of fire on phosphoric 
icid. 

When phosphorus is rapidly burnt in a large vessel 
iUed with dry oxygen or common air, a white smoke 
irises, which soon condenses into white flakes: these 
ire anhydrous pyrophosphoric acid. They are deli- 

• Dr. B. WgginB, Minutes of a Philosophical SocletN, p. ^SL V^i>^%w^\^ 
t intended for making phosphorus, it will answer 'muie&lAXA olVTta^Vvc*- 
borKScid. 



p 



quescent, and, of course, readily soluble in water; tbey 
diBGolve with a remaikable hissing noise. Indeed, neb 
is the affinity of this acid for water, that even in id 
TicrcouE state it retains a small quantity which nabeU 
will expel ; for the compound of acid and nttler it 
volatilised at a bright red heat, if long enough conliniied> 
When pyrophosphoric acid is allowed to deliqaeUGiiC 
■IB converted into phosphoric acid, owing to the leogA 
of time which elapses before it is liqueAed. 

Fhosphorout avid. — Although it hua been sUWd 
above that phosphorus burnt in the air affords pjr»- 
phosphoric acid, this is only true when phosphorus it 
heated to 148°, the point at which it takes fire, so as If 
bum rapidly and with full splendour, and when a full; 
sufficient supply of oxygen or common air had acceu la 
it. But if phosphonifi be heated in a glass tube, tb« 
orifice of which is drawn out so small as greatly ta 
obstruct the ingress of air, il will burn with a. feetde 
greenish Ught, and became phosphorous acid. This » 
a white, powdery, volatile substance : it has a strong 
affinity for water, and will absorb it from the atno. 
sphere, so as to deliquesce into a dense oil-like hquid, 
With one fifth of its weight of water it forms a hydrate, 
■which is capable of crystallising. When the dry powdw 
is heated in the open air, it takes fire, absorbs oxjgeilf 
and produces pyrophosphoric acid : hut when heated in 
a close vessel, it is changed into the same from a dif- 
ferent cause ; for one portion is deoxidated, phosphorus 
aubhmes, and its oxvgeu combines with the phosphortnii 
aCid Whtn hydrate of phosphorous acid is heated in 
close vessels, it afiords pyrophosphoric acid, and phot- 
phonis dissolved in hydrogen gas. If phosphoniB be 
burnt m rarefied air, we obtain pyrophosphoric and 
and phosphorous acid, and a ted substance supposed to 
be oxide of phosphorus. 

The best mode of obtaining phosphorous acid is to 
pass the vapour of phosphorus through a glass tube, 
owdered cotiokWe Eo\?itiiaXje -, " % limtjid 



QOAP. I. PHOSPHORUS. S23 

*Bd the scdudon heated until it is of the thickness of 
symp. It is a oomhination of water and pure phos- 
{jioroos acid: it forms a white crystalline acid on 
Qooling." — (^Davy,) Corrosive sublimate is a compound 
of mercury and chlorine: the phosphorous vapour 
seizes on the chlorine^ forms a limpid fluid chloride : 
the diloride of phosphorus is decomposed by the water ; 
the hydrogen of the water combines with the chlorine^ 
and forms muriatic acid ; while the oxygen of the water 
unites with the phosphorus^ and produces phosphorous 
add. By heating, the muriatic acid and most of the 
water are expelled ; the acid remains pure^ and^ if suffix 
ciently concentrated^ will crystallise in parallelopipedons. 
Hffpophosphorotts acid. — Besides the foregoing two 
adds^ there is this other^ which contains a less ratio of 
oxygen than phosphorous acid. By combining phos- 
phorus with lime^ a compound is produced, which 
decomposes and is decomposed by water : the hydrogen 
{onoB a gaseous compound with a Httle phosphorus; 
and the oxygen unites with the remainder, and produces 
phosphoric and hypophosphorous acids, both of which 
combine with the Hme ; the former producing an inso- 
luble, and the latter a soluble compound. The phos. 
phate of hme being filtered off, the clear liquor must be 
mixed with dilute sulphuric acid, which, having a greater 
affinity for lime, will detach the hypophosphorous acid. 
The most remarkable feature in the history of this acid 
is, that all its combinations with alkalies and earths are 
soluble in water. 

With regard to the ratio in which phosphorus and 
oxygen combine to form the three compounds — phos. 
phoric, phosphorous, and hypophosphorous acids — there 
has been much discordance amongst the statements of 
chemists. The following represents the latest^ results, 
the elements being represented in parts by weight : — 

Phosphorus. Ox. 

Hypophosphorous acid consists of 4 combined with 1 

"Phosphorous acid - - - 4 • - 'i 

PAospboric acid ... 4 . . S 



Photphurelted and fierphaxphnretted hydrogta. — By 
heating phosphorus in h^'drc^en, 3 soludoa of a imill 
pordon only is effected. There are two compoundi, 
conristing of these elements in difioent proportiong: 
they are commotdy called phosphuietted hydr^en, and 
perphoBphuretied hydrogen. They may both be fumtcd 
front a combination of phosphorus and lime, called 
phosphate of lime, which is to be prepared by healing 
small bits of welLbumt lime in the middle of a long 
earthenware tube, sealed at one end, and having a pietf 
of phosphorus kept cold at the sealed end, while the 
middle part is heated across a chaSng-dish of burning 
charcoal. ^Vhen the lime is red-hot, the end conlaining 
the phosphorus must be beaied so aa to convert it inU 
vapour ; this, by passing through the lime, will be ib- 
■orbed, and will form a brown substance, which « 
phoaphuret of lime. !t is a troublesome and difBcalt 
process: if the object be merely to procure a spon* 
neously combustible gas from the phosphuret of Ume,it 
may be accompUshed with much less difficidty. Thro* 
ft piece of phosphorus into a cold crucible ; and having 
heated some coarsely powdered roche-lime in anothtt 
crucible lo redness, pour it suddenly over the phosphorui, 
w> as to cover it to the depth of two or three inches. 
There will be considerable inflammation, which nisy be 
checked by instantly filling up the crucible with bbdiL 
When the ccucible is cold, ilie matter must be hastily 
taken out, and the brownest portions put up for use inW 
a bottle to be well stopped. 

When this substance is thrown into a glass of water, 
IS decomposition of a part of the water 
B, which goes on for a length of time. Some 
hydrogen is evolved j but the chief part of the hydrogeii 
combines with as much phosphorus aa forms perphos* 
phuretted hydrogen ; and eai^li bubble of this gas, on 
reaching the surface, spontaneously catches fire by 
intermixture with the oxygen of the air. A small cloai 
of white smoke, in the form oi & liiia, ascends from 
each bubble, widening aa il rises, »»i m«Q'Ciia% "bi. v 



PHOSPHORUS. 229k 

and beautiful manner. This smoke is white, 
it contains solid pyrophosphoric acid in a state 
ite division. If the glass of water be intro- 
ider a bell glass of oxygen or chlorine^ the corn* 
of the gas is more brilliant : with the former 
lame is white^ with the latter greenish : but in 
se there should be but very little of tlie phos- 
f lime^ as the gas^ when mixed with oxygen or 
bums with violence. The oxygen of the 
composed by the phosphuret of lime also com- 
th phosphorus^ and forms phosphoric and hypo- 
rous acids. 

-e perphosphuretted hydrogen is to be collected, 

1 be generated in a very small retort^ filled to 

of the beak with water acidulated by muriatic 

70 or three lumps of phosphuret of lime must 

thrown in at the beak; and^ as they sink, 

must be plunged in the mercurial pneumatic 

Gas will be formed^ which should be collected 

filled with and preserved over mercury. Much 

ever be kept in one vessel ; for there is risk of 

il intermixture with common air, which would 

3 explosion of the gas. 

I phosphuretted hydrogen is exposed to the light 
un^ or is allowed to remain for some time in 
no matter whether over water or mercury, ex- 
; in the latter case the change is produced much 
>wly, the gas parts with a third of its phof- 
and is converted into the same volume of 
'etted hydrogen. This gas is not spontaneously 
i or combustible when mixed with common air 
3n ; but, if let into chlorine, it bumi spon- 
f, A very remarkable property of this gas i§, 
en mixed with oxygen, rarefaction causes them 
le, as condensation produces explosion in other 
;ases ; or the mixture will detonate by tlie 
spark, or by being heated to 300^. It may be • 
^rredj that phosphuret of lime, if acted, oa V| ^ 
ted muriatic acid, e\6L\e% pboKp\iiixetteiV}<4 

9 









I 

I 



dn^en ; but if the aciil is diluted, perphosphuretteA 
hydrogen is the result. According to Thmnsoii, lOd 
parts hy weight of hydrogen combine with l6 of jihos — 
phonis, to form perphoqihu retted hydrogen, and wilS 
10-666 to form pliosphuretled hydrogen. 

ChhrideK of phosp/ioru*. — A compound of chlorii^ 
and phosphorns may be formed by passing the vapoi^ 
of phosphorus through powdere<l corrosi'vi; Bublimst—* 
The latter, which is a compound of chlorine and mer^ 
oury, is dwoinposed ; its chlorine combines with tfci 
phosphorus, and forms a Suid as clear and colourless ca 
water; this is chloride of phosphorus. It is not in i.ti 
own nature acid; but when acted on by water, it becotaei 
acid iu the manner already described. If exposed to 
the air, it evaporates in smoke for the most part, bwt 
leaTCE a little phosphorus, which speedily burns. TM 
Tapour bums at the candle. 

Ferddoride of photplmrua may be formed by intrd- 
ducing chlorine Snto a receiver previously exhausted nf 
air, and containing phosphorus. " The phoaphonit 
takes fire, and burns with a paJe flame, throwing off 
aparks ; and a white substance rises and condenses on 
tie sides of the receiver." — (-ZJ-iuy.) This ia ■ snoK- 
white powder ; it is very volatile, and evaporates It « 
; under pressure it may be (used, tsi 
?s into transparent prisms. It MB 
r, and decomposes it: the oxygen an^ 
' ; acid, and the hydn^ 
; acid. It is analagouato 
1 many of its properties ; its vapour redden* 
dry litmus paper. — (Bacy.) 

Phogpliuret of fulphvr. — Phosphorus and sulphw 
combine in various proportions, but the exact ratios are 
not known. The combination, if effected by heit, 
■ Sometimes takes place with combustion and explodMi. 
Phosphurets of sulphur are often used for oblaining iD' 
eCanlaneous light : a sulphur match is dipped in the 
compound, and then ruWied. oiv a ^\ece o^ tirft,iiAldi 
produces immediate combaatiovi. K>)e\.'tfK -sstiifawn 



heat below 212" 
it then erystalli 
■violently on wat 
phosphorus form phospll 
and chlorine prodi 



nmap. r. nxtmin*. tfi7 

is the following: — Throw a bit of phoHphonia into & 
stiiill phial, kindle it, and allow it to bum for about 
ttTD seconds ; then eitCtnguish it by corking the bottle. 
I'he substance itt the phial is now somewhat red ; it is 
sxippoaed by some to be an oxide of phosphorus : it is 
8o combustible, that it Bpontaneoualy takes fire in the 
%ir. If a sulphur match be dipped into it, a particle 
a-dheres to the match, and inflameH on drawing the 
"Hatch ouL I believe the following lo be the theory of 
the process: — The phosphorus continually deprives the 
•i in the pbiai of its oxygen ; it is, therefore, con- 
tamully in an atmosphere of azote, and it is thus pre- 
^■wited from burning. When the match draws out a 
{Wticle, the latter takes lire as soon as it is brought out 
Of ihe atmosphere of aKote into common air ; but the 
*ciDiunder of the phosphorus is protected from catching 
4te by the azote which surrounds it. 



The substance called fluorine has never yet been 
obtained in a distinct form ; tbe assumption of its 
separate existence may, therefore, be considered an hy- 
pothesis, though suppormt by the strongest analogies. 
Provisionally, a name has been given to it : it exists in 
the mineral called ^uor spar ; and is called Jtuorine. 
Fluor spar is otherwise called Derbyshire spar, or fluate 
of lime; but its proper name h fluoride a/ caic'ivm. If 
some of this mineral in powder be distilled with strong 
sulphuric acid, from a leaden retort, into a leaden re- 
ceiver kept cold with ice, " an intensely active fluid ia 
produced. It has the appearance of sulphuric acid, but 
it is much more volatile. Wlien applied lo the skin, it 
instantly disoi^anises it, and produces very painful 
wounds. When it is dropjied into water, b hissing, 
noise is produced, iritb much beat, and an acid %m&.'u 
fanned. " — (jOavy.) 



rii 



I 



Flint had, for a length of time, been Bupposed K be 

an earth, analogous in compoddon to the olhei earlH 
IVTien the metallic nature of the earths in genersl wW 
in progress of being ascertaineJ, it was natural!; expecwl 
that silica, or the matler of fiint, would also prove to ' 
a metallic oxide. Experiment, however, failed to il 
close such H composition; on the contrary, it has bwB 
shown that, as far as investigation has been able to 
its base is of a nature very different from metaUic, ui 
agrees with a distinct class of bodies. It may be ob- 
tained by the following process : — 

Let fluor or Derbyshire spar, and glass, (one of tbc 
constituents of glass is flint,) both in powder, he mixed 
with strong sulphuric acid, and heated in a glass retort; 
a gas arises, which, after it has expelled all the commOB 
air, may be collected in the usual manner over mercnry: 
let a piece of metallic potassium be heated in this gtB 
until it takes Are. After the combustion, the potaBdmn 
will be found converted into a brown matter, which, 
when thrown into water, decomposes il, and evolves hy* 
drogen ; for it is a compound of the base of silica united 
with potassium, the latter of which takes up the oxygen 
of the water, and the former combines with a portion of 
the hydrogen. The brown powder must be washed with 
large and frequent effusions of water, and dried. Thia 
is a compound of hydrogen, and the base of flint : if it 
be heated in the air, the hydrogen bums ; if it be healed 
in a close vessel, the hydrogen is expelled, and the pure 
basis of flint remains : it is called silicon : it very much 
resembles boron in its appearance, and in it^ relations to 

Silica, or Silimc actd, — ItissiUcon, that, when com- 
■ned with oxygen, irmnn, \he svAnWace ^ 



QBAF^fr SILICON. S31 

sc^al names silica^ flinty quartz^ rock crystal^ &;c. have 
^n given. But the compound^ instead of being an 
^fiHh, turns out to be an acid: and to obtain it in the 
state of an acid^ no such difficult process as that just de- 
s^bed need be had recourse to : all that need be done. 
^ to heat a piece of flint red-hot ; throw it into water, 
^ make it pulverisable; then reduce it to a fine powder, 
^d melt it .with dry carbonate of potash in a crucible, 
^^en cold, throw it into dilute muriatic acid ; filter, 
and evaporate the solution to dryness. Wash this pow- 
der, first with dilute muriatic acid, and then frequently 
^ith water ; and then dry it. This is silicic acid : it is 
^ gritty, white, tasteless powder. 

It neither has an acid taste, nor reddens vegetable 
olaes ; it manifests its acid properties by combining with 
Dalies, earths, and metallic oxides, in definite quan- 
tities, and with such force of afiinity, that it is not easy 
to decompose the compounds. Flint glass is a salt of 
this kind ; it is a silicate of soda and lead. It must be 
admitted, however, that its acid powers are not very 
decided. 

Silicon does not easily combine with gaseous oxygen, 
although it does readily with oxygen solidified in cer- 
tain combinations. Thus, if mixed with carbonate of 
potash, and heated very moderately, it burns, and takes 
oxygen from the carbonic acid : tlie silicon becomes silicic 
acid, which remains in combination with the potash. 
Silica, or silicic acid, is composed of equal weights of 
silicon and oxygen. 

FluoHlicic acid. — Hydrofluoric acid has the pro- 
perty, which no other acid possesses, not only of taking 
the silica from flint-glass, but decomposing it, and hold- 
ing its silicon dissolved in the gaseous state. In this 
case the silica parts with its oxygen ; the hydrofluoric 
acid loses its hydrogen : the former is reduced to the 
state of silicon, the latter to that of fluorine. The sili- 
con and fluorine, in this nascent state, combine, and form 
an acid. It is difficult to determine wlaicYv \% \Xve X^^'sft 
and wbicb the acidiBer : but it is ki\OY?xi \haX. \)cvfc ^wsv- 

Q 4 



I 



SSS BLnnnTa or cnxxmsr. HtK^ 1 

pound is HI acid, and the name of fuesHicie add bt 
been given to it. It maybe readily obtained by miiinf 
glass and floor apar, both in powder, with strong snl- 
pfauric acid, in a glasB or leaden retort, and appljing 
beat ; fluosilicic acid f^as is discharged abundantly. The 
theory of its formation is obvious from the faregoing 
obfiervations. 

This gaa is very heavy : ICO cubic inches of it wdgh 
1]0'77 grains; hence its specific gravity is 3'631. — 
(Davy.) Dr. Thomson estimates it S-6. It produce 
■while fames when it is diiFused in the atmosphere. 

This gas, when brought in contact with water, is pK- 
tially decomposed by and decompoBes it. Oxygen pistti 
&om the water to part of the silicon, fomiing silici, 
which is deposited in the state of gelalinoas hydrate: 
and the hydrogen of the water combines with the m- 
inaining unaltered fluosilicic acid, and converts it ' 
totally different acid, called hydrofuosUicic acid, 
acid enters into combination with many bases : id 
IB GOUT. The hydrate of silica, obtained in the proced, 
IB soluble in water. 

The action of hydrofluoric acid on silicon, even when 
contained in glass, has been made available for the pnr- 
pose of etching on glass. The easiest mode is to coU 
the glass with a varnish made of spirit of turpentine and 
wax, on which, when dry, the drawing or writing is to 
be traced with a needle, cutting through the vamish 
down to the glass. A margin of wax being then ruled 
round the glass, the hydrofluoric acid, diluted with 
water, is to be poured on .* in a few minutes the whole 
may be plunged in water. The varnish being remtfved, 
it will be found that the lines traced by the needle are 
corroded into the glass ; and beautiful etchings ai 
thus executed. 



The substance called borax has long been uskI in 
arts and in medicine ; but it is only of late years 
I any thing is accurately known of its composition. 
borax, which had been melted in the fire and then 
^deied, be healed intensely with s tenth of its weight 
ine powdered charcoal, in a gun-barrel closed at one 
, a black powder is obtained, which must be several 
es washed with hot water, then with muriatic acid, 
. finally with water again. The resulting powder, 
=n dried, is of a blackish olive colour : it contains 
le charcoal: but the other ingredient is boron. In 
1 state it is sufficiently pure for ordinary c;(periment« : 
(blain it perfectly pure, boracic acid must be decom- 
ed by potassium. Pure boron is an opaque, brown- 
olive powder, infusible, and not volatile in any 
iperature to which it has as yet been exposed. It 
ther dissolves in nor acls upon water : it bears all 
Tees of temperature, under 600°, without change; 
ibout that heat it takes Hre, and combines with osj. 
.. If burnt in oxygen, it throws off bright scintU- 
ons, and is converted into a combination of boron 
li oxygen. This compound possesses tlie properties 
in acid : it is called btiracic acid, and, when combined 
h Boda, forma the borax of commerce. 
Boracic acid, — But it is not by this process that bo- . 
ic acid is procured for chemical purposes. Borax is 
Dmpotmd of boracic acid and the alkaU called soda : 
( salt is to be dissolveil in boiling water, and dilate ' 
ihuric acid is to be added ; it combines with the soda, 
I detaches the boracic acid, which, on the cooling of ) 

liquor, separates in scaly crystals : these, washed 
h cold water, are boracic acid. It is by no means a 
ferful acid; and it even evinces cjaa\iX\es lA ti^CT 
■quirocai naOire with regard to aciiiit^ ■, vVvwa'As ^*fc 



I 



^ perf. 



ii scarcely, if at all, sour: although it reddeng litMM 
paper, it jets like an alkali on paper stained \dth ite 
dye^tuff called tunnerie. The colour of turmerii: piptr 
is yellow ; when acted on by an alkali it ia changed to 
brown r it is hence used as a test of alkalinity; jet 
boracic acid renders it brown. But this snbitance m 
nifests acidity, by combining with alkalies, earths, and 
metals. It dissolves in rectified spirit ; and if tbe tt' 
lution be set on flre, it bums with a green flame: iiei- 
posed to heat, it parts with its water of cryslallisStion, 
amounting to 43 per cent, : it mdts, and then 
bears any degree of heat without further change. When 
cold, it is found converted into a perfectly colourieK, 
transparent glass, which remains so, if it be preserved 
from tlie air ; but loses its transparency, if exposed, by 
the re.absorption of the water which it had lost diuii^ 
the heating. Borax itself, when heated, melts into » 
perfectly clear glass, which is the basis of some artifidil 
gems that possess considerable beauty. Borax coranni* 
fusible nature to other bodies, and henW' 

used as a j?ux. Boracic acid is the only known eon' 
1}ination of boron with oxygen : it consists of one p«rt 
of boron combined with two of oxygen. 

JFtuoboric odd. — Fluorine and boron have an affinity, 
and are capable of combining ; the result is an add, 
which exists in tbe gaseous state. If fluoride of calcium 
(fl.uor spar) and boracic acid, which had been melted to 
a glass, BO as to expel its water, be heated together in aa 
iron tube, both having been rednced to powder and well 
mixed, there will be a double decomposition ; fluorine 
will forsake the calcium ; the calcium will take oxygen 
from some of the boracic acid : the latter will be con- 
verted into boron ; but the calcium, by combining with 
^le oxygen, will form lime, and this will unite with the 
remainder of tbe boracic acid : meanwhile the boron and 
bine, and form a transparent and colourlen 
gaseous acid, which is evolved, an<l which has obtained 
tbe name of fiuohoric ueid. \\. \b bviVvjAiowb, Its smell 

pinWes tliat of muriatic add. 



CHAP. I. BORON. 235 

In this case^ either boron is acidified by fluorine^ or 
£uorine by boron : but^ perhaps^ the truth may be^ that 
neither acts the part of the acidifier more than the other. 
According to tli^ theory of Gay-Lussac and Thenard^ a 
different explanation mnst be given. Fluor spar must 
then be considered a fluate of lime^ — that is^ a combin- 
ation of lime with fluoric acid ; and fluoric acid must 
be viewed as a compound of fluorine and oxygen : when 
heated with boracic acid^ the latter decomposes the fluate 
of lime ; one part of the boracic acid combines with the 
lime^ and the other part combines with the fluoric acid, 
now detached, and forms a gas^ consisting of fluoric and 
boracic acids^ the name of which must therefore be^ not 
fluoboric acid^ hat fluoroboracic acid. According to this 
theory^ we should expect that^ if the acid gas be passed 
into water^ we should obtain a solution of fluoric and 
boracic acids; and this is precisely what happens^ for 
boracic acid actually crystallises. But the fact can be 
equally well explained^ by supposing that fluorine and 
boron compose the acid gas : the gas, when passed into 
water, decomposes a portion of that liquid : its oxygen 
passes to the boron, and produces boracic acid; while the 
hydrogen goes to the fluorine, forming hydrofluoric acid. 
This explanation is the one now generally received. 

Fluoboric acid gas is not prepared for use by the pro- 
cess given above ; the best method is to distil a mixture 
of fluor spar and borax, both in powder, with sulphuric 
add : a glass retort will answer for this purpose, as it is 
not acted on by fluoboric acid. The spar should be quite 
free from flinty matter; for if it contain it, as it gene- 
rally does, the silicon would be converted into fluosilicic 
acid. The gas must be collected over mercury. 

Fluoboric acid gas contains no water ; yet it has so 
powerful an affinity for water, that when allowed to 
escape into the air, or into a gas containing moisture, 
there is an immediate condensation of the vapour into 
visible fumes : this acid is, therefore, sometimes used as 
a test of the presence of moisture in gases. l\&«^^c^^^ 
^avjtjr is 2'362. The fumes which it pxo^ucfe^ vkv ^^^ 



air are nhite, and almost opaque. It is ahsorbed rapidl^^ 
and largely by water, the volume absorbed at 50° bein^^ 
700 times greater than that of the water: the solution; 
is of specific gravity I-77. During this absorption, eoit:^ 
boracic acid crystallises, and dissolves again as the liqti^Sj 
approaches saturation. The taste is powerfully ai ' ' 



Section XIV. 



I 



\ 



■ 

that aO J 
latinge I 



To an ordinary observer it might appear, that al 
metals are essentially the same, and that their difibreiw 
of colour and other properties may be owing to a 
and character given to them by adventitious drtoiH' 
srances, or hy a trifling admixture of other substancei. i 
The opinion is natural, and was once entertained bf 
most of the chemista of that day ; or, as they were dieB , 
called, alchemists : and as gold was the most valuable oT | 
all metals, and was considered as the pure basis of & 
the rest, their efforts were directed Co the separaticia of 
the substance, whatever it might be, the presence <u 
which prevented lead and other base metals from hmn^ 
gold. It 18 scarcely necessary to ohaerve, that these 
eSbrts failed, the modem chemists, believing the thing 
to be impossible, have come to the matter of fact coH' 
elusion, that 1^hen metals are of different colours, de- 
grees of hardness, strength, lustre, brittleness, &c,, thej 
are of different natures 

Gold. — This IS the most valuable of all inetals. In 
B State of ]iunty it is not generally known, as the melal 
is not commonly met otherwise tlian alloyed with cop- 
per. The gold com of Great Britain is a mixture of 
gold, copper, and silver. The constitution of the coin 
was first determined by law in the reign of Edward I.: 
S3 parts or carats of fine gold, 1 of copper, and 1 
of silver, at present constitute sterling goUl ; or it may 
consist of 22 parlt oi ftne goW Bail o( co'5\ier. The 
mint price of this g,o\d, liial i*, 'i^ waniaii. -iiiKR 



mp 



a.t which it issaes, is 31. !?«■ lO^d. per ounce: and a 
t-roy pound of it, formerly coineil into 44^ guineas, 
is now coined into iG aovereigas, and Ms. iid. over, 
^ach sovereign weighing 123 J grains, or more exactly 
133'274. This is called sterling gold ; but standard 
}^ld does not mean exactly the same. I'he latter term 
lias more immediate reference to the manufacture of gold 
VtensilE, and takes greater latitude of composition. 
Standard gold has two extremes: it may be eterling, 
that is, 22 gold + 2 copper; or it may be 18 gold + 
a copper. Articles sent to Goldsmith's Hall to be marked 
will obtain the mark representing either of these quali- 
ties. Should the artide sent profess to be sterhng, and 
prove on assay not to be bo rich in gold, it will be broken, 
and ihe mark refused. Should it profess to be I S carats 
fine (that is, gold IS + copper 6), while it is really 
richer, or sterling, or even virgin gold, it will be marked 
as 18 fine. Any article below 18 carats wili not be 
marked; and pure gold will be marked as II carats. 
Silver may be substituted for copper ; its eSect is to 
produce green gold, as it is called. 

The reason of adding these other metals ia, that pure 
gold is not the most serviceable slate of the metal : a 
mixture of gold and a very small quantity of copper is 
much harder than pure gold, and will near much better. 
It may be here observed, that when any metal is melted, 
and combined with another or several metals, the com- 
pound metal ia called alloi/. The property of being 
extended by mechanical force, as by hammering, is 
called maUeability. In the chapter on cohesion, many 
examples of the malleability of gold have been given. 
The ductility of gold, or that property which permits it 
to be drawn out into thin wires, is considerable : a wire 
of only Tt)'^ '^^ '"' '"'^^ i" diameter will support a 
weight of 500 pounds without break-ing; this property 
is (^ed Uniacity, and it belongs to gold in an eminent 
degree ; but it is known that the process of drawing a 
raetai into wire enhances its natural lenacitj. \Vie- 
tjuires a heat very iittie higher tllan CO'g'^ V» ■mi^^.'W., 



I 



much higher than Eilver, and greatlv higher duo linC 
lead, and tio ; but by far lower than iron. It tmj hf 
kept at a very high heat for almost any length of itnx 
Dnaltered : Knnkel kept gold in a glass-house fomue 
for nearly eight inonlhs, daring whiEh it neither lotl 
any weight, nor appeare<l changed- The highest len- 
peraturc that can be exeited is found, howerer, lo rtdi- 
tiliae a little of it.* If exposed to the most inienw 
heat of a powerful burning glass, Its surface becinnra 
purple, owing to the ab«orption of a little oxygen by tbe 
metal from the atmosphere ; and it may be aettully 
biuned in the flame of hydrogen ur^ed by tt stream of 
oxygen, and converted into a purple oxide. Electiidty 
does the same. 

When 100 grains or parts of gold combine with i 
of oxygen, an oxide is produced : but this oxide do** 
not contain the lart^est quantity of oxygen that can be 
combined with gold ; for these 104 gruns, in a short 
time, undergo decomposition ; one third robs the other 
two thirds of their proportion of oxygen, and the part 
thus deprived is reduced to its original state of meuUic 
gold. The gold, thus deprived of its oxygen, weighs 
69J grains ; the oxygen of this quantity, amounting tff 
aj grains, is, therefore, transferred lo the remaining 
S^l- parts of oxide, which, already containing 1^ grain 
of oxygen, will then contain i grains of oxygen in all: 
but this it the full quantity of oxygen which the 
original 104 grains of oxide held combined; and it is 
now contained in one third of that weight, or 34^ 
graine. Hence, a new oxide is the result; and it must, 
thereibre, contain three times as much oxygen as the 
original 'oxide. From these facts it is manifest, that 
gold combines with oxygen in two proportions : its 
protoxide is composed of 100 parts of gold, combined 
with 4 of oxygen; and its peroxide of 100 parts of 
gold united to 12 of oxygen. 

Gold alloys with various other metals, as tin, lead, 

• BriiWin'f PhyiicBl Pilnfii.l™. 6it-V-»W- *tM™*\iB..^«tedL a™ 
tela > IHlJeflbo.e gold Uilen.el:f liesWiXiT nXniTtimilfio*. 



copper, iron, mercury, &c. ; the alloys being of more I 
"' less use. ^VTien any metal unites with mercury, it 1 
!■ said H) amalgamate ; and the compound is calleil an - 1 
"malgam; but the distinction is absurd, and without 1 
practical use. I 

Gold is a little more than ip times heavier than its I 
fciilk of water ; its precise specific gravity, when pure, is I 
19'3.* I(B hardness is between that of silver and tin. I 
Notwithstanding its ductility, the smallest admixture of I 
Iiismuth, lead, or antimony, renders it brittle ; io little as I 
^.TTjth of either is suHicient to affect its ductility. I 

Gold is found, in nature, in the metallic state for the I 
most part. When any metal occurs, in a stale of J 
tuture, in its metallic form, it is said to be found in 1 
the native Hale. But native gold is seldom pure, being 1 
generally alloyed with a little silver or cojjper. U 
Dccura in compact masses, or crystallised in cubes,* i 
prisma, octahedrons, or pyramids ; or it is found in I 
grains. It is found, in veins, in primitive mauntains, I 
although not of the oldest formation, accompanied by | 
Tarious atones and metallic ores. 

Gold occurs in almost all parts of the world ; and, 
although so generally, only in small quantities, unless 
in the warmer regions of the globe. Africa and America 
supply the chief European consumption. America pro- 
duces, annually, 30,000 pounds' weight. About thirty- 
sis years since, an immense fragment of rock tlimbled 
from one of the highest mountains of Paraguay ; and 
masses of gold, weighing from two to fifty pounds each, 
were picked out of it. In the cabinet of the count i 
d'Ons-en-Bray there was a specimen of native gold, I 
which weighed sixteen pounds. — {^Brienon.) It is found 
in grains, in the sands of rivers, in various parts of 
Africa, America, and even Europe. Cramer says, that 
" there is hardly any gravel, in the nature of things, 
that does not contain gold in it." — {Dodmasia.) Near 
Pamplona, in South America, single labourers have 
collected SOO/. worth in one day ; atvA in ftome. 



F840 



ELEMENTS OF OBKniSTBT'. 



I 



lOngBt the graina, lumps weighing 73 anil 133 
In certain rivers in Scotlant], gold dust hu 
been fouud. At the coronation of Charles 1., medala 
were made of this gold, with this inscription round tbe 
edgCj Ex auro at in Scotia reperitar. And, in 1539) i 
coinage of native gold was issued in Scotland. 

In Ireland, county of Wicklow, seven miles west ot 
Arklow, about the year 1770, there was an old schorf- 
master, who used frequently to entertain his, neighbonn 
with accounts of the richness of their valley in gold; 
and his practice was to go out in the night to search fot 
the treasure. For this he was generally accounted in- 
sane. But, in some years after, bits of gold were foDod 
in a mountain stream, by various persons ; and, in 
1796, a piece weighing about half an ouiice. The 
news of this having circulated amongst ihe peasantrj, 

(Such an infatuation took possession of the minds of the 
people, [hat every other sort of employment, save thtt 
of acquiring wealth by the shon process of picking ittqi 
out of the streams, was abandoned ; and hundtedi of 
human figures were to be seen bending over the wateji^ 
and scrutinising every object there to be seen. In tbii 
way, during six weeks, no lese than 800 ounces of gdi 
were found, which sold for 3/. 1 5«. per ounce, or 300DL 
Most of the gold was found in grains ; many piecei 
weighed between two and three ounces; there was one 
of five ounces, and one of twenty-two. It contained 
about 6 per cent, of silver. Government soon uuilertwifc 
the works ; but the amount of gold found, while supeN 
intended by the appointed directors, was only StiT^J- 
It then appeared, that there was no regular vein in the 
mountain, and that these fragments had probably existed 
in a part of the mountain which time had mouldered 
away, and which left its more permanent treasure U 
the only monument of its ancient existence. The voik> 
were at length discontinued. 

in Croatia, in the sands of the Drave, gold to the 

■mlue of about I6OO dacata i» Mwva^'j I'saai hy the 



OBAF^It UBTAtB. B4] 

Gold is said to have been detected in vegetable ashes 
and in garden manure. It enters into various combin- 
ations ; we have its combination with chlorine, iodine, 
broiniiie, sulphur, and phosphorus. It dissolvea with 
effervescence in a mixture of nitric and muriatic acids: 
the result is chloride of gold. If peroxide of gold be dis- 
solved in muriatic acid, and precipitated by ammonia, ■ 
powder is obtained, which detonates even by being rubbed. 

Silver. — .The metal next in esteem to Rold, of those 
that are generally known, is silver. This is a soft 
metal, and possesses great malleability; it may be 
beaten into leaves so thin aa -molioa'^ ^^ ^" lichi 
yet this is almost three times thicker than gold leaf. 
It may be drawn out into ivires thinner than the ' 
human hair ; hence its ductiUty ia next to that of I 
gold. Its t(.-naciiy is such, that a wire one tenth of an ' 
inch in diameter will support a weight of 270 pounds. , 
Its tenacity is, therefore, not much greater than half 
that of gold : but silver is a httle harder Its specific 
gravity is 10'474. In point of brdhancy it exceeds all 
metals except steel. It melts at a full red heat; and' 
hf a fierce and long continued fire it may be made to 
boil and evaporate away altogethir In the greatest 
ordinary heats, as that of a glass-hou^ tumace, it loses 
bat little weight, and that httle slauly 

If kept for a long time melted it ahaorba oxygen 
from the atmosphere, and torms a brown oxide, 100 i 
parts of silver combining with 7 272 of o\ygen, Dt, ' 
Faraday has discovered an owde that consists of 4'848 
parts of oxygen combined with 100 of silver; that is, 
two-thirds of the quantity of oxygen contained in the 
brown oxide. The singular fact has been ascertained, 
that silver in fusion absorbs oxygen, which, on sohdify- 
ing, it parts with : and Gay-Lussac says, that it thus 
giies out twenty-two times its own volume, and that 
the presence of a very little copper destroys this pro- 
perty. Silver alloys with gold, iron, lead, tin, i\uick- 
diver, &c.: it unites also with copijet, Mvi tetwvs «a. 
Hoy which, like that of gold with co^'jer, \b ^XMiEt 1 




I 



Bwtab, a^ydi Uhntratec the prindple tlut bodks do M 
m'tte in etaj proportioa, but in deceminste pnfot- 
dona : if the two metals be Icqit mdtetl togefba fv 
■ome dme, and liloved to cool, two strata will b 
found, ODe Ijiog otct- the otber, and not adherii^J 
neither wtmma, however, is pore, for each meul am. 
laina a poititHi of the other, Uut portioD being llie 
■ataiating qoanlity. 

One poond of standard mlTcr is coined inU 
ahtUings; it was formerlT 6S shillings — (Wation): tlw 
mint price of silver is, therefore, 5». 6d. per ouni 
present. 

This metal occarv in the native state, and allofcd 
with a tuiet; of other metals and sabstances. It il 
found in all parts of the world. In 17^0, a mai 
native silver was taken from a mine near Frejhaj^ I 

■which weighed upwards of 140 pounds: and in 17*4 
a mass, a part of which was ore, was discovtsed, 
which produced 44,000 pounds of silver. The iMd 
ores fur the most part cont^n some silver : it is (a>d| 
that in the leail ore of a mine in the county Aotriin, 
one-thirtielh of the whole weight of metallic lead ob- 
tained is silver. The Cumberland lead ore afibidt 
IT ounces of silver from a Ion of lead. Hut a miiw 
in Yorkshire, for every ion of lead, afforded 2S0 
ounces of silver. The lead mines in Cardiganibkc 
produced at one time 9000/. worth of silver per monttk 
In l60*, 3000 ounces of Welsh silver were coined* 
the Tower. We are informed by Humboldt, that the 
silver mines of Mexico and Peru, in the space of ibne 
centuries, have produced 316,023,883 pounds' w^bt 
of BJIver, These mines afford many limes more mIt« 
annually, than all the mines in Europe coUecdvely.. The 

silver miiieH of Kongsbei^, ia'^tinia,-^, m. one y*" 

(1 idy), produced 79,OOQt. 



MKTAM. 94S ^ 

IT combines ni(h chlorine, iodine, bromine, mi- 
ni, and phosphorus. It dissolves readily ii 
' nitric acid, and mity be precipitated in the 
nietaUic state, although not perfectly pure, by immer- 
sion of a plate of copper : but perfectly pure, and in 
fine powder^ by pouring into it a solution of green sid- 
phate of iron. Bj digestion in liquid ammonia, oxide 
of silver acquires the property of detonating when 
Btruck or rubbed. 

Iron. — We now come to consider a metal with 
which none can compare in point of real utility, and 
fortunately of abundance. Iron is found in almost 
every mineral production. It is much harder than 
either of the two preceding metals. Its specific gravity 
is from 7' to 7'84 ; and it ia, therefore, the Ughtest of ' 
all the useful metals except tin. It may be drawn o' 
into wires of great fineness : a wire one tenth of an ini 
in diameter will support a weight of 450 pounds : hence ■ 
its tenacity is a little less than that of gold. It is oi 
of the few metals which the magnet attracts ; and it ] 
readily acquires magnetic properties, which, however, 
are not permanent." To melt iron requires a very- 
intense heat, much higher than either of the preceding 
metals, and, indeed, nearly the highest that can 
excited in furnaces. When raised to a yellow heat, it 
becomes very soft, and may then be hammered out i 
any shape. When (he heat ia raised towhileness, it 
grows so soft as to Buff*er even a commencement of 
flision ; for if two pieces be laid in contact at this tern-' 
perature, and struck, they unite and form one, the 
junction being as solid as any other part of the iron. 
This property of uniting, by hammering at a high 
lieat, is called welding. Iron is a very combuGtible 
metal ; if thrown into a common coal fire, in a state of 
filingH, it bums with brilliant scintillations : and a very 
thin iron wire bums with scintillation in the external 
Same of a candle. Its vivid combustion in oxygijn w 



r S44 



BI£VSNTi 09 CHBMlimTi 



I 
I 



deacribed in a former chapter. During the combusdun, 
the iron melts and forras into drops, which at length 
fall down. This is protoxide of iron : to form it, eroy 
100 parts of the metal combine with 28-572 of oxre*"' 
If the protoxide be exposed to a red heat for 9ome 
hours, it absorbs half as much more oxygen, and fonni 
the peroxide, consisting of 100 metal and 42-837 
oxygen : and if the peroxide be heated to whilenen, 
it will give off the 14'285 parts of oxygen, and will lie 
reduced to the state of protoxide. The cobur of tlie 
protoxide is black; that of the peroxide is led: but, 
according to Gay-Lussac and Thenard {TraitS Eb- 
mentaire, trois. edit. ii. R?.), there is an intermeilille 
oxide obtainable by passing steam over iron wire at » 
red heat. The British chemists reject this oxide. 1 
have reasons for believing that it exists : for I hsK 
obtained cumpounds which seem not to contain eitha 
of the admitted oxides. 

Iron, in the purest state in which it occurs in GOB. 
merce, is called vrovght iron. If pieces of wrou^ 
iron be laid one over another, witli intermediate layoaof 
charcoal, and kept at an intense heat for several diyi, 
a combination of iron and charcoal will take place, nd 
the result will be steel, which every one knows is cap^ 
of being made much harder than iron : it is also mOE | 
sonorous, tenacious, elastic, and ductile, than iron. Itv 
capable of becoming a permanent magnet : iron aiiqabts I 
only a fugitive power. The ratio of carbon combiiKd 
vridi iron so as to form east itee! is 99 parts of iran to 
1 ot carbon. But these are not the only proportions in 
which they unite; irAi(pca«(ironconsiBlBof lOOparttrf 
iron, combined with 5-26 of carbon: this kind is brittle, 
and ao very hard thai it cannot he cut with a file. Bladi 
call iron is composed of 100 parts of iron, united to 
7*066 of carbon : it is fusible, and much softer than the 
preceding ; the quality need for castings is of this nunre 
nearly. These estimates are t^en from Thomson's a- 

jieriDients, and ttey ap«c ^i«q ■oeaiX-j -wviv >b»Kof 

" . Atushet. 



Thus, the greater the ratio of carbon to iron, the m 
fusible the compound becomts ; and the greater the ri 
of carbon, within certain limits, the harder the compound 
becomes : but beyoud these limits it is rendered softer. 

The relation of these three compounds, witli regard 
to the quantity of carbon which they contain, is illua- 
trated by the fact, that if a dender rod of pure wrou^t 
iron be immersed in radted cast iron, it will come out 
GonTert«d into steel, because some of the carbon has been | 
absorbed by it from the cast iron, Wrouf;ht iron maf 
be converted into steel by ignition in carburetted hy- 

It has been already stated, that tlie diamond possesses 
the property of converting wrought iron into steel, be- 
cause the diamond is carbon. 

Iron is found in all parts of the world. There ia 
scarcely a stone, or a particle of soil, in which it may not 
be detected ; it ex.Uls even in plants, and in the human 
body. It occurs commonly in the state of oxide, more 
or less complicated with clay or slonea, and other metals ; 
it is thus found in veins, and disseminated in rocks. 
The Bulphuret of iron, called pyrites, is a very com- 
mon mineral. Iron also occurs in immense masses in 
such situations as have suggested the idea of their hav. ' 
ing fallen from the air ; they have hence been called i 
meieario iron. Professor Pallas describes a block of ] 
diis iron found on the top of a mounlaiii in Siberia; 
it was said, by the inhabitants to have fallen from the 
sky; it weighed 16S0 Russian pounds.* In Croatia, 
a large led.liot mass of iron was actually seen to fall 
from the atmosphere : it is now in the imperial museum 
ofVienna: this occurred in 1751. In South America, 
a mass of meteoric iron was discovered many years 
since, which was estimated at 30 tons' weight. An- 
other, found in Peru, weighed about 15 tons; its ex- 
ternal surface was marked with singular impressions, 
resembling hands and feet, and the claws of birds. In 
• EqaiH to ISSai ayoitdupoii. 



I 
I 



I as 

the desert of Zahra, tbere lies e. vast idbbe of this Idtid 
of iron. In the Academy of Sciences at Petersbuijh, 
there is a mass deposited, which weighs 1200 poimdi. 
In 1620, a mass of iron fell from the atmosphere in. 
the Mogid territory, which weighed a little more tbn 
4 pounds. 

It ia very singular that these masses of iron lie in 
•ituations to which they could scarcely have been pe- 
jected from any volcano ; none such being foiaiil within 
a cDnfliderable distance of them, and no symptoms of 
an extinguished volcano having been discovered in the 
surrounding country. It is also a remarkable ciicum-. 
stance, that the iron in many cases u combined with 
another metal, nickel, which is always an ingredient in 
these masses, called meteoric stones, that have been 
actually seen falling from the air. Hence, it is do 
wonder that the behef of these masses of iron havii^ 
fallen from the atmosphere has become prevalent. L« 
Place has has even calculated, that they may have been 
projected from a volcano in the moon. 

Iron, when heated in cldorine, buma with a red 
light, and forms a chloride. It combines with snlphiir 
in five different proportions. It will be only necessuj' 
here to describe that which is frequently used for pnw 
curing sulphuretted hydrogen. There is some diffi* 
Culty in preparing it in such a manner that no metalUe 
iron shall remain unchanged : for, in proportion as then 
is metaltic iron, hydrogen will be produced when ihe 
compound is acted on by ddute sulphuric acid. I have 
never failed in procuring sulphuret of iron good enough 
for common purposes, when I observed the following 
formula : — Mix 10 ounces of Sne iron fiUngs with 6 
of flowers of sulphur : heat a crucible to a bright reil, 
and, having removed it from the fire, throw in the mix- 
ture. A kind of combustion commences round the 
margin next the crucible, and this extends slowly lothe 
centre, the ignition becoming more intense every mo- 
ment. When it has teacheA tive ceivUe,,'iX»; '::an&va«.<tiaa 
/s complete, and the igQUvoti^iegniB Vi iSiwiaaSti. VtVs*. 



G8AK I. METALS. 247 

cqM^ the mass shrinks^ and may be extricated frgm the 
crucible by mere inversion. It is a deep gray -coloured 
^th a shade of purple. 

Iron combines also with selenium^ silicon^ phos- 
phorus^ boron^ and various metals. 

Coj^per. — The metal^ which in point of general 
Utility ranks^ perhaps^ next to iron^ is copper. Its pe- 
collar red colour need not be described. Its specific 
gravity is very variable: on an average^ it may be 
said diat copper^ after meltings is 8*9*' by hammer, 
ing it is increased; a specimen which^ after meltings 
was bat 7*242, became 9*020 by being hammered. — 
(WaUons Essa^, iv. 57.) Copper is a very malleable 
metal: it may be beaten out into very thin leaves^ 
by the same process as gold leaf is made, and in this 
state it is called Dutch metal. It melts at rather a 
kywer heat than gold : at an intense heat, it boils and 
evaporates away in metallic fumes. When rubbed, it 
emits a smell. When heated in a hydrogen flame, 
urged by oxygen, it bums brilliantly, and emits a 
dazzling green light : a piece of copper, in a coal Are, 
tinges the blaze green ; and even when melted, it emits 
a bluish green light. When exposed to air and 
moisture, it rusts into verdigris, but very slowly with- 
out moisture. When heated red-hot for some time, its 
surface saturates itself with oxygen, and a scale is 
farmed, which is spontaneously detached when the metal 
eools : this is deutoxide of copper ; and, to form it, 100 
jiarts of copper combine with 25 of oxygen. The prot- 
oidde, procurable by a more complicated process, con- 
sists of 100 parts of copper, united to 12*5 parts of 
oxygen, which is half the former quantity. The per- 
oxide is composed of 100 parts of copper, combined 
with 50 of oxygen. 

When copper leaves are introduced into chlorine, the 
metal spontaneously takes fire, and a chloride is pro- 
duced. If copper filings and sulphur be heated, a 
sadden and brilliant combustion takes place *, aiv^ ^^% 
happens -even in a racuum. The tcbuU ia a «vvi\Jtoa^'C 

R 4 



I 



I 

I 



of copper. Copper rombines aleo with [ 
aelenium, and iodine. 

Copper is found in the native state in all parti of llie 
world, although not in lai^ quantities : but one to; 
iai^ mass of mi^tallic copper is on record ; it wis 
&nind in Brazil, and weighed 26l>6 poundii. It occiitg 
alloyed with other metals, or combined widi ox^en and 
. aciili. 

Lead is one of the softest and most fusible of llu 
metals. It is easily rolled into sheets ; but it doeG not 
tulmit of being beaten into leaves like gold, silver, and 
copper ; nor does it allow itself to be drawn into very 
thin wire. Its specific gravity ia lI-4>. At a temper- 
ature between 600° and 612° It melts; at a highv 
heat, it boils and evaporates : at the heat of burning 
hydrogen, urged by oxygen, it burns with i 
flame. When exposed to air while in fusion, and kept 
continually stirred, it absorbs oxygen, and is at leagA 
totally converted into an oxide. There are three oxidM 
of leJid : the protoxide consists of 1 00 parts of meta), 
combined with 7-6Q2 of oxygen ; the deutoxide, of 100 
metal, with half as much more oxygen, or 11-538; the 
peroxide, of 100 metal, with twice as much oxygen tt 
forms the protoxide, that is, ] 5*^84. The protoxide 
is known in commerce as a yellow paint, under the 
name masBteot, or, if it be semivitrified, litharge : Ae 
deutoxide is also a paint ; its colour is a brilliant red, 
inclining to orange : its commercial name is minUtm, or 
rfd lead. The peroxide is of a deep, puce brown 
colour ; its most remarkable property is, that, when tri- 
turated with sulphur, spontaneous combustion takes 
place. The peroxide may be formed by transmitting 
chlorine through water mixed with red lead : when the 
latter is dissolved, add potash ; a powder falls, which is 
to he dried on blotting paper. 

Lcail is never found native. If protoxide of lead be 

exposed to a sufitcient heat, it melts, and forms a 

besutifui glass, perfectly transparenv, atvi ^toiaMstoit- 

ktB: hy fax the most coTumon BU.wm"»''ta.'^'t''«-w«'™' 



I nature, ia mineralised by Gulphur. The common 
itne for BUlphuret of lead is galena : it is abundantly 
nind in all the quarters of the globe ; most abundantly 
L secondary roctca, but often in primary. 

THn resembles lead in many of its properties. We 
)eak familiarly of various implements and vessels said 
' be made of tin ; but what is meant is tin-plate, or 
ates of iron coaled on both sides with tin, which, in 
ime degree, has penetrated the iron throughout. The 
le of tinning sheet iron is to prevent it from rusting, 
id the consequent desliuction of the utenall ; tin is 
ucli less perishable than iron when exposed to air 
id moisture. Tin is of a roellow silver colour : its 
iftness is such, that it may readily be cut with an 
on knife. It may be beaten out into leaves less than 
/g-j^th of an inch tiiick. What is called tin.foil, 
jwever, contains a' little lead. Tin melts at a much 
wer heat than lead ; 440° is suflicient. Its specific 
avity is 7"285. When intensely heated, and oxygen 
ipplied, it bums with great brilliancy. When kept 
elted for aome time at a low red heat, in contact 
Lth air, oxygen is absorbed, and a gray protoxide is 
■oduced. There are two oxides : the protoxide con- 
sta of 100 parts of tin combined with 13793 of 
;ygen ; and if the protoxide be considerably heated, it 
kes fire, burns like tinder, absorbs a new portion of 
lygen, and forms the peroxide, consisting of 100 parts 

tin and 27'586 of oxygen, or double the quantity in 
e protoxide. 

This metal combines with cidorine, iodine, bromine, 
losphonis, sulphur, and duoiine. It alloys witll 
veral metals. The coat of tirming which is given to 
e inside of copper vesBels. is, in fact, a mixture of 
id and tin ; and the use of it is to prevent the copper 
im coming in contact with the food prepared in such 
vessel, which might be otherwise impregnated with 
at poisonous metal. Although lead itself is a poisonous 
BtaJ, it is singular that the presence ot^Mviwiifttft'A 
'oxious; the nasoD of which U, tlialtMi yteNea^* **« 



I 



I 



lead firom dissolving. Pewter is camposed of lead ud 
tin ; and on account of the presence of the Utter, die 
former is rendered safe. Tin generally occurs comhiiitd 
with oxygen, in a crystalline Torm, in veins tnTersiig 
priraitive rocka. It is found in many parts of Europe, 
and in all quarters of the globe. It does not ippw 
that tin IB ever found in the native state, unless ne ni) 
on the testimony of Matthesius. Cramer affirms, ihil 
English tin is the best of all ; for its ore is, of all tin 
ores, that which is less defiled with iron." The Si^ 
exportation of tin from England took place 3200 Tean 

Zinc. — This meial, although entering into the coia- 
position of one of the best known of tdl metallic com. 
pounds, is, itself, very little known to the genenlitj 
of persons who have not made these subjects their study; 
when combined with copper, it forms that usefid sab- 
stance, bTiws. Zinc is of a bluish white colour ; its hne 
is intermediate between that of lead and tin. Its specific 
gravity is about 7, or very nearly the same as that of 
tin. When heated, it enters into fusion about 0SO°, or 
700° : at a higher rate, it evaporates ; and, if access of 
■ir be not permitted, it may be distilled over — by which 
process it is rendered purer than before, although it is 
not perfectly pure. When heated red-hot, with access 
of air, it takes fire, bums with an exceedingly beautifnl 
greenish or bluish white flame, and is, at the same time, 
converted into the only oxide of zinc with which we ore 
acquainted, consisting of 23-53 parts of oxygen, com- 
bined with 100 of metal. It is, when cold, a fine 
white powder, Uke flocks, and bo Ught, thai it was 
formerly called philosojAical imxil and vhile nothing. At 
common temperatures, zinc can be extended but little 
under the hammer ; but, at a heat a little above that of 
boihng water,, it may be roiled into thin sheela with 
.facihty, or drawn into wire, although it will not form 
ibin wire. At a temperature midway between this heal 
and its melting point, il bccomea «a \vcWiiE, a& U be 
easily reduced into a fine i>owAet, 



. I. METALS. 251 

Zinc is found in all quarters of the globe : it occurs 
in Great Britain and Ireland^ associated with lead : it 
is never found native^ but is met in combination with 
Oxygen^ sulphur^ &c. It combines with^ and is set on 
fire by^ chlorine : it enters into union with phosphorus^ 
sulphur^ selenium^ iodine^ and various metals. 

Mercury, — r However easily melted some of the pre- 
ceding may be^ there is one metal which exceeds them, 
and all others, in fusibility : this is quicksilver, or, as 
it is called by chemists, mercury : so fusible is it, that, 
nvithout the aid of art, we never see it in any other state 
than that of a liquid. Yet, when mercury is reduced to 
a very low temperature, it freezes, or becomes solid; 
and then it may be cut with a knife, or beaten out a 
little by the hammer. Its malleability is, however, 
very limited. The freezing of mercury has been known 
to take place, in very cold chmates, spontaneously, and 
without any artificial process : it was witnessed by 
Pallas, at Krasnojark. This metal, in freezing, con- 
tracts very much ; hence the mercury of a thermometer 
does not indicate the true freezing point when it becomes 
solid. On such occasions, it has sunk 600° below 
freezing. Its freezing point is discovered by allowing 
a mass of frozen mercury to liquefy slowly when the air 
is very cold : during this process, a thermometer im- 
mersed in the mercury will steadily stand at about 40° 
below zero, which, of course, is the real freezing point. 
The temperature at which it boils and evaporates is 660® 
of Fahrenheit's thermometer. It may be readily dis- 
tilled over. Its specific gravity at 60° is 13'568. 

Mercury combines with oxygen in two proportions : 
to form the protoxide, chemists seem agreed that 100 
parts of metal unite with 4 of oxygen; and, to form the 
peroxide, the same quantity of metal unites with twice 
as much oxygen, or 8. By keeping mercury at its 
boiling heat for a length of time, in contact with air or 
pxygen, its vapour combines with the oxygen, and 
ioims ibe peroxide : but it is a very ^^crai\X xsi^xxet xk^ 



I 



252 

obtain the protoxide id b state of puiit;. Thk loetilw 
nol aitered by exposure lo t" 
It combines with chlorine in two proportiona: 
c)i]oriile, commooljr called calomel, consists of 100 pull 
[>f mercury, united to 18 of chlorine ; the perchloride, 
called orrosive sublimate, of the Esme quantity of mer- 
cury, with 36 of chlorine : it is a violent poison. Mer- 
cury also combines with iodine, hroinine, Eulphnr, tui 
fluorine. 

This metal occurs in the native state, or amalgamalcd 
with silver, or comlnned with sulphur, constituting 
cinnabar. It is produced in South America and Spus 
in great abundance. But, perhaps, the greatest qoict- 
silver mine in the world is that of Idria, in CarnioU. I 
It has been at work for more than three centuries: its I 
average produce, during four years, was about 366,000 
pounds of mercury ; it employs, in all, about 1000 men. 
The ore raised afibrds better than 8^ per cent, of metal: 
but mercury in the metallic state is found abundantly, 
sometimes issuing from the rock in a stream ; and, in 
this way, 36 pounds have been collected in six Itouif. 

Platiyium. — Tliis is a metal which, of all others, 
possesses properties the most useful for the construction 
of vessels of all sorts, and for various other purposes. 
It will not melt in the heat of our most powerful fur- 
naces, — a property of much importance, but of the les 
value, as it prevents the possibility of casting it into 
different forms. Even this defect is nearly coimterrailed 
by the property which, like iron, it possesses, of weld- 
ing ; two pieces may thus be united, by laying them in 
oontact and hammering them while they are raised to 
■n intense heat. It does not rust or corrode wheit ex-- 
posed to air or moisture ; and if heated in the hottest 
fiimace, it comes out bright and untarnished. Notwith- 
standing all tiiese advantages, platinum is of little use to 
mankind, for its price is juat as high as its properties are 
valuable ; hence its limited employment in the arts. Its 
colour is while like silver ; \W syicifec ^rariS^ '\i IV W ? 
it baa been drawn inlo wiie ao iJcaa aa -j^^^Tju-inA «fc 



im^ 



inch, but only in short lengths, and not very perfect. 
The number of ila oxides is not ngreed on by chemists ; 
there are probably four. 

There is a form of this metal which possesses some 
extraordinary properties ; it is called spongy platinum. 
It may be prepared by dissolving platinum in a mixture 
of nitric and muriatic acids by heat : b> the solution 
must be added solution of muriate of ammonia, while it 
continues to precipitate any thing ; the precipitate, fil- 
tered off, must be washed with water, and dried in the air. 
If a small quantity of this powder be heated in a candle, 
it will become incantlescent, as if it took fire. It is, when 
cold, fit for use. If a jet of hydrogen, from a tube of 
very slender bore, be directed on it from a little distancBj 
the metal immeiiiately becomes red-hot, and it sets fire 
to the hydrogen. This may be repeated a great number 
of times ; but the sponge at last loses its power : the 
smaller tile quantity, the sooner its power ia lost. The 
lower the heat to ithich tlie powder was exposed in the 
candle, consistently with producing incandescence, and 
the shorter time the heat was applied, the longer will 
the spongy platinnm continue to produce the pheno- 
menon, and the more certainly it will act. The cause 
of this effect is not known. 

The combinations of platinum with metals and other 
simple substances are very numerous. 

Potasiium. — This metal may be obtained in a variety 
of ways : the aimplesl, is to abstract oxygen from potash, 
by exposing a mixture of dry carbonate of potash, with 
half its weight of recently burned charcoal, to a strong 
heat in an iron bottle coated with Stourbridge clay, and 
having a pipe proceetUng from the bottle, so contrived 
that it can be kept cold with ice, and the air excluded. 
Potassium tlistila over, which condenses into a solid 
metal. Its colour, when it is newly cut, is white, hke 
that of silver, hut it rapidly tarnishes in the air: lo be 
preserved from change, it must be kept under na^bcha. ^ 
that substance not containing any ox^ge^. \\. w. ». ctm- 
ductor of electricity : its specific gtavil-^ \^0■&65,■wa^e 



I 



being I'OOO; it, therefore, although a metal, is ligbw 
than nsler, and swims upon it. At ordinari/ tempct- 
atnres, it may he moulded hj the iingerB ; at 32°, il ii 
brittle; at 150°, it melts perfectly; and riseB in »apoiir 
in a heat a little below that of redness. When thwwn 
upon water, it acts with great violence, swims upon the 
surface, and hums with a beautiful white and red ligb' 
mixed with violet ; and the water is found to be alkalhK. 
It iuflamiiS when gently heated in the air, bums with t 
red light, and throws otF allcaline fumes. It burns ipon- 
taneously in chlorine, with intense brilliancy. 

Oxygen combines with potassium in twoproportwiu: 
the protoxide is that which is formed when the nietil ll 
thrown into water, and which exists in common potaab ; 
it consists of 100 metal and 20 oxygen. The peroade 
is formed when potassium is burnt in oxygen ; it con- 
•iats of 100 metal, and three times as much oxygen as 
in the last, or 60. When thrown into water, this per- 
oxide gives off 25 per cent, of oxygen by eftervescence, 
■nd is reduced to the state of protoxide. 

What chemists call caustic potash, ia a hydrate of the 
protoxide : it is generally prepared by depriving peari. 
ash (common potash ignited) of its carbonic add by 
means of hydrate of lime, bodi being diffused in water j 
&e solution, being filtered, is to be evaporated, and the 
pure alkali dissolved away by alcohol. But pearlaah 
always contains commou sea salt ; consequently, the 
resulting alkali will contain soda. To remove this source 
of error, I varied the process, a few years since, in ibe 
fallowing manner : — Dissolve the salt sold by dru^scs 
under the name of bicarbonate of potash, in the smalleat 
possible quantity of water at 100^ temperature ; decant, 
and expose the solution in a flat dish before tlie fire: in 
a few hours a crop of crystals will be obtained, which 
are to be separated from the mother liquor, and rinsed. 
The crystals are next to be boiled with their own wei^t 
of hj'drate of lime B.nd water for fifteen minutes : after 
dae subsidence, the clear liqiioi: ia «i \>e -jraMieili. tiS. Thit 
' solution of caustic potash, w'todi, 'nw "vn% a. -^-weA^ 



I 

^^ (Ale SI 



affinity for carbonic acid, is to be carefully preserved 
t'nm thK air. — {Dublin Phil. Journ. i. 48.) If it be 
Required in the solid state, it muit be boded down in h 
'Oliver or bright iron vessel, and out of contact with the 
sir. If solid potash be applied to the surface of the 
Qody, it destroys the part, and forms an eschar : it 
changCB vegeuble blues to green, except litmus ; and it 
changes vegetable yellows to brownish red : it is soluble 
in water or alcohol. When nitre has been heated until 
totally decomposed, with a view of obtaining oxygen, it 
is not potash that remains, as was commonly suppoied, 
hut peroxide of potassium. If it be kept for a length of 
time at an obscure red heat only, it ia not perfectly de- 
composed, but is changed into a salt called hyponitrite 
of potash. 

Potassium combines with hydrogen, and forms a gas, 
which spontaneously bums when let to pasii into the air: 
it is always formed when water is decomposed by this 
metal, and it bums on the surface ; or when potaBsium 
is strongly healed in hydrogen. When potassium and 
sulphur, or phosphorus, are heated l<^ther, even in a 
vacuum, they combine, with the phenomenon of brilliant 
combustion, and form sulphuret and phosphuret of po- 
tassium; both of which hum when heated in air. When 
sulphur and pearlashes are heated, the result is chiefly 
sulphuret of potassium ; the oxygen of the potaah being 
abstracted by some of the sulphur, and carbonic acid 
expelled. If potassium be introduced into chlorine, a 
brilliant combustion takes place, and chloride of the 
metal is formed. It bums in sulphuretted hydrogen, at 
the same time combining with the sulphur: it burns also 
in hydrofluoric acid, forming fluoride of potassium ; 
and in fluoboric acid, forming fluoride of potassium, 
boron being liberated. If heated in carbonic acid gas, 
it burns, takes oxygen from the charcoal, and the latter 
is precipitated; it absorbs cyanogen gas, becomes red- 
. hot, and forms cyanide of potassium ; it also takes oxjgen 
a boracic add, and leaves boron. 

. — Tbja metal may be obtJdnei^i's Mi'j ol'Coft 



I 



I 



266 BUBKHNTa or chkkhtbx- Mmmr I 

proceEseE which Hflbrd potassium. In many of ils da. 
TBCters it rest^mblei potassiuni : it is lu white sa silver, ] 
has great lustre, and is & conductor of decliid^. It J 
fuses at iibout 200°, and evaporates at a strot^ red lieat: I 
iu specific gravity is 0*973- When heated sQroDglf il 1 
oxygen or clilorine, it hums with great brilliBTicy. 'Vl^ 
thrown upon water, it efferresceti violently, but doea not 
inflame : it Ewims on the surface, gradually diminiabn 
with great agitation, and renders the water a solution of 
soda. It acts upon most substances in a manner sitnilir 
lo potassium, but with less energy : it tarnishes in the 
air, but more slowly ; it then absorbs oxygen. Like 
potassium, it is best preserved under naphtha. Then 
are two oxides of so<Uum ; the protoxide consists of 101) 
metal and 33^ oxygen ; the peroxide, of 100 metal and 
50 oxygen. 

The protoxide, combined with water as a hydrate, is 
the caustic soda of chemists ; it may be formed fian 
the bicarbonate of soda, by a process similar to that given 
for caustic potash, and may be solidified in the stune 
manner. Sodium bums in chlorine, and forms chloride 
of sodium, or common culinary salt. It combines with 
sulphur and phosphorus, occasioning similar phenomena 
to those presented by potassium ; but the sulphuret and 
phosphuret of sodium are less inflammable. 

Lithium. — Of this metal very little is known : it 
exists in several minerals, and its stony origin is indi- 
oated by its name. The minerds called »podumene and 
petalUe afiord it in small quantity. Its basis was proved 
by Davy to be metallic: its protoxide is the alkali called 
lithia. Its solution in alcohol, in burning, emits a red 
light : it has a very acrid taste ; and, in some respects, 
acts as a caustic. It does not deliquesce ; and it dis- 
solves sparingly in water, whether hot or cold : a red 
heat melts it. It absorbs carbonic acid from the air : it 
reddens vegetable yellows : it is not volatilised by a white 
heat. The chloride of lithium is dehquescent and soluUe 
in strong alcohol, Lilh\a \>aa scmiviettKiE iv±M.'a«,^miig 
power: it forma a sulpiiMel, ■w\iic\i,-rfBfin.6Es«tQ.\ra^ 



MAf . U MKTALS. 257 

>y adds^ affords the same products as sulphurets of 
^r earths and alkalies. From this account^ it appears 
hat lithia acts as a kind of connecdng substance between 
be earths and the two alkalies^ potash and soda : at 
nt, indeed^ it was mistaken for soda. It exists in 
ctalite in the very small ratio of 5 to 7 per cent. ; and 
I spodumene 8. Lithia consists of 100 parts of the 
«tal lithium^ combined with 123 of oxygen. 

Calcium, — One of the most useful and generally 
H>wn of the earths is lime^ the burning of which has 
ien abready described. By means of galvanism^ Davy 
^cceeded in separating from it a metal possessed of 
oderate lustre ; but in such small quantity^ that it was 
^t possible to make sufficient experiments on it : to this 
' gave the name calcium. When heated in contact 
ith oxygen^ it takes fire^ and forms an oxide^ which is 
Dae: but tliere is also a peroxide of calcium. Pure 
one is tasteless^ and insoluble in water : it readily ab- 
)rbs water poured on it^ swells^ heats^ bursts^ and is 
myerted into hydrate of lime^ commonly called slaked 
me ; it has now acquired a taste ; it is soluble in water^ 
kd the more so if the water be cold. The solution is 
Ued lime-water ; its taste is styptic^ followed by sweet- 
!ss. Lime-water made in the cold^ and^ therefoie, 
turated^ deposits hydrate of lime, if the water be raised 

212°. The alkaUne properties of lime-water are 
werful^ and it ^nders vegetable yellows brown. If 
posed to carbonic acid gas^ or to die atmosphere con- 
ining it^ the lime combines with the carbonic acid^ 
comes insoluble, the compound precipitates, and water 
siains : the water is expelled from hydrate of lime by 
red heat. It is possible, but difficult, to procure lime 
crystals, by evaporating lime-water at ordinary tem- 
ratures in an exhausted receiver. Every one knows 
U slaked lime, mixed with siliceous sand, and water 
ded, constitutes mortar, a cement for building. The 
rdening of mortar has been supposed chiefly to depend 
the tibaorption of carbonic acid^ and ih.exe-QoiiN€t«\Qiw 



of iitne into carbanale of fimt, wUeb is txtoB^^ 
lurii, u appears in the iiuance of fimestoac I b^m 
the tbtnr; to be, that Kmie of llie bScvobi atfM n 
actuall* diMohed by tbe caustic lime inio a pnle; ad' 
that such panicles of the Ejlifa is do not £nali«s> 
tirely, enter into combination by their snrfaees, 4« 
compound surfaces holding the heterogeneous mattBii 
a stale of finn cohesion. This, at least, acmmiti farde 
■tonjr bardneaa of mortar in the interior of ihidc tU 
walls, where carbonic add could scarcely haw ]we- 
tratcd, and where it appears not to have been abeorbtd, 
at least in sufficient quantity, by the fact that it scared; 
eServesces when treated with adds. Beside the nxof 
liine in maktnt; mortar, it is of extensile utility in agri- 
culture, for improvinR the quality of land. 

Lime h best prepared for chemical purposes by in. 
teniely heatin); pure white marble, bo as to expel ill 
carbonic add. Chlorine decomposes lime, wh^n asuitcil 
by heat ; the oxygen is expelled from the calcium, ai 
the chlorine takes its place, but in double the volune: 
the new compound is chloride of calcium, — aremarUUf 
deliquescent substance. Lime also combines with dd>- 
rine by a very weak affinity, as is always tbe case iriKR 
thelatCer combines with a metallic oxide: chloride of KiK 
is produced, — a salt chiefly useii for bleaching. Tfaoe 
ii also an iodide of lime. Calcium combines with sulpbtir, 
phosphorus, and bromine. Lime, or protoxide of oi- 
dum, consists of 100 parts of caldum, united with 40 
of oxygen. The peroxide contains caldum 1 00, oxy- 
gen 80. 

Magnesiwai. — The employment of magnesia in me- 
dicine has rendered it universally known, and beyond 
that use it contributes very little to tbe wants of man- 
kind. The source frcm which the chief supply of 
magnesia was formerly derived was the sea. If its 
water, sufficiently boiled down, be mixed with peulaab, 
a white powder subsides, wliicb, when washed, is a 
coinbiuation of this eartH wU\\ cttt^wnit anA (krind 
from the alltaU. There is a toi-wnai t^ei 



fiBJLB, I. METALS. 259 

^mestone^ consisting of carbonic acid^ lime^ and mag- 
i^ia; and from this we now obtain abundant supplies. 
When the combination of magnesia with carbonic acid 
is exposed to a red heat^ the carbonic acid is drawn 
off, and magnesia is left in a state of purity. During 
this ignition^ the magnesia appears much hotter than the 
fire in which it is heated; a bright white light is emitted 
l>y the earthy apparently of the phosphoric kind. This 
phosphorescence attends the ignition of some other 
earths also. If a little magnesia, which has been thus 
ignited, and still remains a little warm, be placed in a 
wucer, and a little exceedingly strong sulphuric acid be 
poured round the edges of the saucer, there will be a 
hissing noise produced, and sparks and flashes of bright 
White light will be emitted from all parts of the mag- 
nesia. In the heat of burning hydrogen, urged by 
Oxygen, this earth is fusible, but not in any lower 
<legree. 

The basis^of this earth has been proved to be a metal ; 
it has been obtained in brown scales, which, when 
nibbed against agate, leave a metallic stain of a leaden 
colour. If this metal, which is called magnesium, be 
strongly heated, it bums with a red light, and is con- 
verted into oxide of magnesium by combining with 
oxygen ; this oxide is magnesia. Or, if magnesium be 
thrown into water, it sinks, slowly effervesces^and be- 
oomes covered with magnesia. 

When magnesia is heated strongly in chlorine, the 
oxygen is displaced by the chlorine, and a chloride of 
magnesium is formed. If the vapour of potassium be 
passed over ignited chloride of magnesium, the metal 
magnesium is separated in brown scales. 

Aluminum, — The earth alumina, when pure, is a 
fine {light powder of brilliant whiteness; it does not 
dissolTe in water, but soaks it with avidity, and retains 
it^ forming a mass, which is so ductile and tenacious, 
that it can be moulded into any form. This paste, 
when heated, becomes exceedingly liaxd ; %ivd \\. \& qtx 
iccount of those properties that aluTmiia i& «i\:w^.^^ NJft* 

8 2 



I 



baeii of every kimi of potlery. WLen a maagofilii. 
niina le heeWil, it shrinks in bulk propoitionalely tollw 
intensity of the heat; hence, it has been employed Bl 
kind of thermometer, or rather pyrometer, for meiMir- 
ing high heats, which wouJd destroy an ordinary titer' 
mometer. A gaage is used for determining the amoiut 
of the contraction. The contraction of aluininB lu> 
been supposed to be an exception to the general Uw of 
the expansion of sohds by heat ; but it may be oiJj 
apparently so. During the heating, water, which kepi 
the particles at a certain distance asunder by its ability, 
is expelled, and not fully without a. while heat : cobe* 
Bion may then take place the more strougly, eo as to 
bring the particles nearer together; but they may not 
approach so closely to each other as If the antagoniBing 
force of calorific repulsion were not at the same lime 
acting. Thus expansion may actually haTe been pro- 
duced by the heat, although it is disguised by tlM 
greater ratio of contraction, owing to loss of mitlei 
(water), and consequent increase of cohesion, nowmott 
energetic, because not obstructed by affinity. 

Alumina is tasteless and inodorous ; but if breathed 
upon, it acquires a smell distinguished by the ti»i« 
tarthy. This earth, in a state of purity, may be obtaind 
from alum purified hy recrystaUisation. A solution of 
such aluni is to be mixed with deliquesced peartashul 
excess ; the precipitate which appears is to be separaUd 
by the filter, well washed, dissolved in dilute nmriWic 
acid, and again precipitated by liquid ammonia. The 
precipitate well washed, collected, and intensely heated, 
is pure alumina. 

By causing potassium lo act on chloride of aluint' 
num, the basis may be procured in the metallic state; 
it is called aluminum. It is obtained as a grey powder, 
which, under the burnisher, assumes metallic lustte. 
When heated red-hot in air or oxygen,ilbumH aplendiiUy; 
oxygen is absorbed ; and an oxide is produced, which is 
alumina. It is excessiveV^ haiA, wA. cmcw tt-^Ue of 
cutting glass . The metal is iAola«£4oa\)-j 



UP. I* METALS. 261 

it at a boiling heat it effervesces in a slight degree, 
his metal^ like iron^ is a non-conductor of electricity 
ben reduced to minute particles. When the metallic 
•wder is thrown into the flame of a candle^ it scintillates 
:e iron burning in oxygen. Oxide of aluminum or 
imina consists of 100 parts of aluminum^ combined 
th 8 of oxygen.^ Aluminum combines with chlorine^ 
losphorus^ sulphur^ and selenium. 
Glucinum, — The metallic basis of the earth called 
icinum may be separated by the same means as the 
sis of alumina. It is a very dark coloured powder^ 
lich requires the burnisher to produce its metallic 
ttre. It is called glucinum. When heated in air or 
ygen^ it burns brilliantly^ and affords the oxide. 
Glucina is a soft^ tasteless^ white powder^ which^ when 
(t^ is somewhat plastic like alumina. It neither dis- 
ves in water^ nor melts in the fire. Like abimina, its 
ts have a sweetish taste; and both of these earths are^ 
this respect, opposed to magnesia, which, with acids, 
brds salts of a bitter taste. Glucina is of rare occur- 
ice in minerals ; it has not been converted to any 
*, and therefore need no further be described. Oxide 

glucinum consists of 100 metal and 44*44 oxygen; 
is compound is the earth glucina. Glucinum com- 
les with chlorine, phosphorus, sulphur, selenium, 
line, and bromine. 

Barium. — By a complicated process, sir H. Davy se- 
rated a metal from this earth, which he thus describes: 
• It appeared of a dark gray colour, with a lustre infe- 
)T to that of cast iron. It was considerably heavier 
an sulphuric acid; for, though surrounded by globules 

gas, it sunk rapidly in that fluid. It instantly he- 
me covered with a crust of baryta (protoxide of ba- 
mi) when exposed to the air, and burnt with a deep 
1 light when gently heated. When thrown into water, 
effervesced violently, disappeared, and the water was 
ind to be a solution of baryta. 

• Thomson, Tirst Pjtinc, \. 31^. 
8 3 



■S6C KLuiBKM ar BBBnanSK «MM 

There are two oxides of barium : the protoxidt is 
, funned in the manner just deECribed ; and if (his be 
heated in oxygen gas, a quantity of that gas is abEorbed, 
and peroxide of barium is produced. 

Baryta may be obtaineil from the very common mi- 
neral dulphate of barytea, by heating ils powder, mixed 
with charcoal powder, to whiteness ; dissolving the miss 
thus produced in water; adding nitric acid; filtering; 
evagmrating until, on cooling, crystals form ; and h«atiiig 
these crystals to redness for a length of time in ■ plk- 
limini crucible. ^Vliat remains in the crucible is 
oxide of barhim or baryta. It is a gray powder, 
absorbs water Uke quicklime, and slakes like lime, Uid 
sometimes emits light in slaking just a 
quantities does. A hyilrate of baryta is thus produced, 
which dissolves in water ; the solution is called harjl* 
water ; and the earth may be obtained from it in ciysttis 
by evaporating the water, or by the cooUng of a 
rated solution. Baryta water rapidly attracts carboidc 
acid from the air. All the soluble compounds of ba- 
rium are poisonous in a high degree. The protoside 
or baryta consists of 100 metal and II ■71)4 oxygai'I 
the peroxide 100-f23'529. Barium combines i" 
ehlorine, sulphur, phosphorus, and bromine. 

Strontium. — The earth called strontia so much n- 
sembles baryta that they were once confounded. St 
K. Davy, by the same means as he obtained the metal of 
baryta, obtained also that of strontia. The metal sttoa^ 
tium resembles barium in most of its properties ; and 
there are two oxides of strontium which may be obtained 
in the same manner as the two oxides Of barium. Tbe 
protoxide is tbe earth called strontia ; and it may be oV 
txined from the mineral called sulphate of strontia, by * 
similar process to that for preparing baryta. CertMO 
compounds of strontium possess the property of tinpng 
flame of a deep rose-colour : the use of such compoandi 
n theatres is well known for procuring red light. One 
i&unilred parts of the meWi Bttawwiwi towWiro; ^ ' ' 
8:181 of oxygen, ti 






I. 



METALS. 263 



36'362y to form peroxide. This metal combines 
chlorine^ phosphorus^ and sulphur. 
trium. — Most of the salts of this earth are sweetish 
e taste ; and two of them are of an amethyst colour, 
n yttria is melted with a proper quantity of borax^ 
rms a transparent glass ; but it is opaque^ if the 
tity of borax be too great. By heating potassium 
chloride of ittria^ the metallic basis of the earth is 
ned. The metal is procured in iron gray scales, 
ated in oxygen or common air, it bums brilliantly ; 
m oxide is formed, which is the earth ittria. But 
aetal is not oxidated by water, even if boiling. The 
i is insoluble in water, tasteless, and white, and 
s to have suffered a commencement of fusion. It 
10 action on vegetable colours. Caustic alkalies do 
ct on ittria, but it is dissolved by solution of car- 
l;ed alkalies. An intense heat is necessary for its 
n. Yttrium combines with chlorine and the com« 
bles. 

\orinum. — This is a newly discovered metal, which 
be obtained by a process similar to that for obtain- 
ttrium. It is of a leadeil gray colour, heavy, and 
r the burnisher shows metallic lustre. Water does 
ict on it. The oxide may be formed by heating 
netal in common air ; it bums brilliantly ; the re- 
ig snow-white oxide is the earth called ihorina, 
ng caustic alkalies do not act upon this earth ; mu- 
; acid dissolves it readily ; sulphuric acid has much 
action on it, and nitric scarcely any. Thorinum, 
1 heated in vapour of sulphur, bums. 
irconium. — The earth called zirconia is a harsh 
ish powder, without taste or smell ; it possesses no 
n on vegetable colours, and is insoluble in water, 
fusible at a lower temperature than any of the 
r earths : the heat of a good forge is sufficient to 
n it. It is soluble in the mineral acids, and in 
ions of alkaline carbonates. — (JDavy.^ The basis of 
IS been separated by the agency qjf po\as««3Lift., «c^^ 
7posed to be metaiUic ; but as yet t\ie cbiei ^^"Cflv- 

8 4 



w 



guisliiiig property of metals — a decideil melallic Instre 
— lias not been evinced by it. It is a perfectly Uuk 
powder. Sir H. Davy, by means of a m^:nifier, s 
particles which appeared metallic in some pariaj and of ' 
a chocolate brown in others. The black powiler buni 
St a heat below redness, and forms the oxide or earth 
LctrconuL 



We have now taken a brief Eurvey of those metal* 

which, on account of being of extensive utility to man. 

Icinil, are f^enerally known ; but the catalogue is by m 

I .means exhausted. On the contrary, those described ate 

L exactly one half of the total number knonn. ~' 

Kiinelals which remain to be noticed are either useless in 

P-their own nature, or are so on account of the difficoltj 

and expense of procuring them, or they are useful fori 

few purposes only ; hence, little more than an eni 

ation will be required. 

JMickei is a hard malleable metal, which, like iron, ti ' 

I attracted by the magnet, and, unless it contain arsenic, I 

Via convertible into a magnet. It has not been genenltf 

B.TOnverted to use, on account of its scarcity. Dr. Fyft, 

1^ lays, " Nickel exists also in tchile copper brought &SID 

China, in union with copper, iron, and xinc, which is 

Bopposed to be obtained from a native production called 

white copper ore. The composition of the white copper 

^0^e 1 have found to be copper 40-4, zinc 25'4, iron fi, 
and nickel 31-6."— (i^y/es Clianiilry, 620.) 
. The metals called Cerium, Uranium, Moli/bdenum, 
Tungsten, Colnmbium, otherwise called Tantalum, Tellw 
rium, Cadmium, and Fanadivm, on account of their 
Bcarcity, or from the difficulty of reducing them to the 
metallic state from their ores, are but imperfectly known, 
and have not been applied to any useful purpose. CotaU 
"s used for giving a blue colour to glass anrl porcelain! 
m^e tint is beautiful, and \\ence vW mMA^Rmaa high 
Jfanganeve is macb vn use ■, ^V '^^ mk^Xo^iA^si 



<HJtP. I. METALS. S65 

^888 makers for two opposite purposes: for commu- 
mcating a purple or violet colour ; or for destroying all 
oalonr^ and rendering the glass colourless. This dif- 
ference of eflfect depends on the property, which the 
metal possesses, of combining with different portions of 
oxygen : there are four oxides known. In order to un- 
derstand their action on glass, it must be observed, that 
iron often adulterates the materials of which glass is 
made, and a very small quantity of the protoxide of 
iron gives to glass a green colour, although the peroxide 
imparts no colour. Now, if to glass rendered green by 
a little protoxide of iron, we add a small quantity of 
tritoxide of manganese, it will give off a little of its 
oxygen to the iron, which thus becomes peroxide, and 
loses its colouring power. On the other hand, the trit- 
oxide of manganese possesses the property of rendering 
glass purple, while the deutoxide possesses no such 
power ; the manganese, by converting the iron into the 
state of peroxide, is itself reduced to the state of deut- 
oxide; and this, like the peroxide of iron, does not colour 
glass : hence the original colour of the glass is de- 
stroyed, and no new colour is communicated, if the 
proportion have been rightly adjusted. 

It is in the state of tritoxide, or black oxide, that man- 
ganese is commonly found in nature ; and when this 
oxide is reduced to the metallic state, the metal speedily 
absorbs oxygen from the air, and returns to the state of 
black oxide. It is from the tritoxide that chemists for 
the most part obtain oxygen for experimental purposes; 
and the modem practice of bleaching cannot be con- 
ducted without it: hence, this oxide is extensively 
useful in the arts. 

There is another metal used in coloured glass making, 
and glass and porcelain painting, called Chromium; it is 
also used in enameUing, and as a rich, strong, and dur- 
able pigment. To glass and enamel it communicates a 
green colour, while it furnishes to the painter his best 
and mast lively yellow : its high price TaMc\Y \\m\\& \\a. 
me. 




Binmiith is one of the most fusible of the metals, and 
it communicates fusilnlitj to other metals, 
of tin, leaiJ, and biamutb, is bo fusible, thai it mdls when 
thrown into boUing vatet : a toy of tliis kind is ireQ 
known ; it is a spoon which, when immersei) in a reiy 
hot liquid, immediately mells. An alloy, compoEeil of 
3 parts of leoil, 2 of tin, and 5 of bismuth, melts al IST, 
and may be used for taltiiig casts from gems, i 
The compoation is rendered fusible at a still lower heat 
by the addition of a Ultle mercury. This last prepar- 
ation is also used for silvering (as it is called) the Inaide 
of glass globi^ : the compound, when gently heated in the 
globe, melts; and by Cuming the globe, an equal costing 
ma; be laid on, which, when cold, hardens and adheres. 
There is a substance pretty generally known, iit con- 
sequence of its being much used in medicine, called 
Antiviomj. The substance to which the name is cobu '| 
monly given is an ore, from which a peculiar metal ma; I 
be extracted; and it is to this metal that the name of anti- 
mony is given by chemists. Jt is.wbite, and so brittle, 
that it may be reiluccd to powder : it melts when heated 
to redness ; at a higher heat it evaporates. It has three ' 
I oxides. Antimony, melted with 16' limes its wdj^ ' 
^«f lead, forms the alloy of which printing types SK 
fiinned : and the alloy of tin and antimony, made into 
plates, is used for engraving or rather punching mudc 
The crude platinum of commerce is by no meani 
pure: it contains no less than four other mi^t^s; these ue 
called palla'liuin, rhodium, iridium, and osmium. They 
I are procurable in very small quantities : they have not 
I been applied to any use ; possess no very remarkaUe 
L jiroperties ; and, therefore, need not be here further 
1. noticed. 

I The last metal to be enumerated, is one that, in a cer- 
I tain state of combination, is well known to the world, on 
I account of its destructivi^ucss to animal life : it ia called 
I Arsenic. This is a grayish white metal, which may be 
L^BiVy broken to powder. \T\veT\ ii«i4KiB.\eV^ kieajjed, it 
fcreptrates, and at the same t^iwie coToiii-ttet -kvOo. ot-^^o. 



fSBLAP, I.' METALS. 267 

forming a white coloured oxide, commonly called arsenic, 
\)ut improperly, that name belonging only to the metal. 
This oxide is the well known poison. 

Such is the very brief sketch of the metals at present 
known. It will be necessary to make a few general ob- 
servations, which will render t^heir resemblances and 
diflferences more manifest than when separately con- 
sidered. In the first place, it is to be observed, that 
all the metals possess that property weU understood by 
the expression metallic lustre, without which no sub- 
tance can be considered a metal. They are of different 
colours : — some are white, as platinum, palladium, 
rhodium, iridium, silver, nickel, cerium, tin, mercury^ 
molybdenum : some are bluish white, or grayish white, 
as lead, zinc, iron, arsenic, tellurium, manganese, 
uranium, cadmium, antimony, chromium, tungsten : 
two are yellow, namely, gold and titanium : copper is 
red; bismuth is reddish; and cobalt has a paler reddish 
tint than bismuth. 

There are three metals magnetic — iron, nickel, and 
cobalt : chromium has been affirmed to be magnetic. 

Some metals possess the property called malleability : 
gold and silver may be beaten out into leaves, almost 
inconceivably thin ; copper, tin, platinum, and lead, 
possess the same property, but less perfectly: others 
are totally destitute of it, as arsenic, columbium, anti- 
mony, cobalt ; and they can even be easily reduced to a 
fine powder : hence these are called brittle metals. 
Nearly allied to the property of malleability is ductility, 
which expresses the capability of the metal to be drawn 
out into fine wire. All the malleable metals possess this 
property: gold, silver, and iron may be drawn into 
wires as fine as a human hair : lead and zinc may be 
drawn into wires, but they cannot be made fine : the 
brittle metals, as might be supposed, do not draw. 

Metals differ much in their cohesion or hardness : 
tungsten is so hard as to resist the file ; while lead and 
tin may be scratched with the nail o£ oive a ftivgst. 

With regard to the fusibility of melals, ox XJaea ^«^^ 



I 

I 

I 



bility of beins melted by heat, they diSer from adi 
other as much as in any other respect. Some sieabw- 
luUJy infiisible in the greatest heats of our fumsces, is 
platinum (which, however, melts in the flame of hy- 
drogen, urg^ by oxygen), rhodium, iridium, molyb- 
tlenum, and, we may add, uranium : it requires tbe 
most powerfd heat to melt manganese, nickel, andiron. 
Others melt long before they become red-hot, as tini 
lead, and bismuth; while potassium, at common teinper. 
atures, is always an easily moulded soft-solid, and mer- 
cury is, at all ordinary temperatures, in a liquid eUW. 
It is particularly to be observed, that metals difitr 
very much in the faciUty with which they unite i ' ' 
oxygen. Some of them, by mere exposure to the at 
■phere, absorb its oxygen with great rapidity ; such M 
potassium, sodium : otbers more slowly, as manganeKj 
iron, arsenic ; and lead and copper stil! more slotriy. 
Others do not oxidate by exposure to air, unless ai t 
high temperature, as tin, zinc, titanium, mercury, anti- 
mony, bismuth, osmium, rhodium, and .cobalt. Others, 
again, will not oxidate by exposure to air or heat, or by 
immeiaion in water, as gold, platinum, palladiuin, 
iridium ; and we may say nearly the same of nickel; 
silver is with great difficulty oxidised by heat. TheM 
are some of these metals, which, when heated red-hot in 
the fire, burn with the greatest splendour, and at the 
same time unite with oxygen ; of this kind are copper, 
zinc, cadmium, tin, and bismuth ; columbium bumi 
feebly ; iron fihngs thrown into the flame of a candle, or 
exceedingly thin iron wire held in the external part of tbe 
^ame, will scintillate : antimony bums at a while heal; 
«nd tellurium burns before the heat of the blow-pipe. 
In short, at intense heals, most of the metals may bt 
burned. But if placed in a burning jet of hydr^en, 
on which a jet of oxygen is allowed to mix, they defla- 
grate with intense brilliancy and great facility. On the 
other hand, potassium burns by contact with a piece of 
ice, with as much inlensU'j, aa o^Xwia io -wWn 'citnted 
in the oxyhydrogen flame just taetiiAOTaA. 



HAF. I« liXTALS. 269 

Some of the metals^ when exposed to heat^ not only 
lelt^ but obey the general law of other bodies — boiling 
nd evaporating when the heat is sufficiently high, 
i'hus^ mercury^ zinc^ cadmium^ bismuth^ tellurium^ and 
ntimony^ boil and evaporate at a moderate heat : it is 
ven known that^ in a Torricellian vacuum^ mercury is 
vaporated at ordinary temperatures : silver and lead 
equire a higher heat; tin and cerium a violent heat: gold 
rill only evaporate in a slight degree^ under the most 
atense heat that can be applied; and iron^ nickel^ 
langanese^ uranium^ and chromium^ cannot be made to 
vaporate in the most intense heat with which we are 
cquainted. Arsenic evaporates without melting. 

In evaporating^ some of the metals afibrd a pecidiai^ 
mell. Arsenic vapour has the odour of garlic ; tellu- 
ium smells like horseradish; and osmium takes its name 
rom the smell of its vapour. Some have a smell when 
ubbed^ without being heated. 

There are instances^ even^ of some metals assuming 
be state of vapour^ and maintaining it permanently; 
lut^ to do so^ they require to be combined with a gas. 
rhus^ arsenic and tellurium unite with hydrogen gas^ 
nd form gases^ called arseniuretted and telluretted by- 
Irogen gas. Zinc^ in small quantity^ also dissolves in 
lydrogen. There are compounds of tellurium and by- 
irogen, and of bismuth and hydrogen, which are even 
apable of existing in the solid form ; the former is 
oluble in water. Potassium dissolves in hydrogen, but 
he compound spontaneously decomposes after a while. 

Some metals, when combined with oxygen, afibrd 
>xides, which possess the properties of acids ; they are 
ailed metallic acids. Arsenic affords two oxides, 
^bich act in the double capacity of bases and acids. Of 
he three oxides of antimony, the deutoxide and peroxide 
re acids. The following metals afford each two oxides^ 
he protoxide being a base, and the peroxide an acid : 
— tungsten, columbium, titanium, chromium, uranium, 
in^ vanadiunij and, perhaps, gold. Tvio xcvaXa^a, xaa- 
bdenum and cobalt^ afibrd three oxides e«y^ \ ^^ ^^« 



1 oxide of both being acids. Of the four osidcE of nun- 
r ganese, the peroxiiie is itn aclil. The foUonEDg; metilt 
produce two oxides ^ach, both of which act aa basH: 
— plntinncOj palladium, rhodium, gold? silver, nier- 
cury, cerium, nicliel, iron. With zinc and fftdmiiuii. 
oxygen combiues in one proportion only, and the oxide 

tacts as a base. Lead anil copper give three oxides each, 
all bases. Iridium is supposed to have four oxides; and 
oemium, five ; but nothing is certainly known of them. 
, Some metallic oxides are alkaline in a hi(dl degree i 
luch are those of potassium, sodium, and lithium. Nine 
Other metals aiford oxides of alesB aikaline nature ; th«f 
vere formerly called earths ; calcium, barium, Btnm- 
tium, magnesium, yttrium, aluminum, zirconiunf 
thorinum, glucinum : tlie first four earthy oxides change 
vegetable yeliows to brown, but the last six do Ml 
aSbct them. 

Tellurium, by combination with hydrogen, is ooB- 
verted into an acid, as well as with oxygen. SeTeialof 
the metats, when acidified by oxygen, combine wiA 
hydrofluoric add, and form double acids ; such as chro- 
mium, tungsten, raolybilenum, columbium, and titanioin. 
The names of the melaUic acids are arsenious and 
arsenic, autimonious and antimonic, tungstic, columlNC, 
titanic, chromic, uranic, Btajmic, vanadic, auric ? mO' 

»lybdic, cobaltic, manganesious and manganesic, tetlDrie 
-and lelluretted hydrogen, fiuochromic, fluotungslie, 
■ fluoraolybdic, fluocolumbic, fluotitanic. The alkaline 
and earthy oxides are potash, soda, lithia, lime, baryta, 
Btrontia, magnesia, yttria, alumina, zirconia, thorinB,8nil 

Many of the metallic oxides, when taken into the 

Btomach, act as poisons. Oxide of arsenic is a notorions 

r and virulent poison ; oxide of copper is less virulent 

r. fhan arsenic ; oxide of lead is a painful poison ; oxide 

r of nickel is known to be a Ipoison ; and peroxide ti 

ry, unless iu small quantities, is of a poisonoua 

^Witb regard to the aUo^B.Uia ^^e^aMaa.-^ WjAefint, 



«HAP. I. METALS. 271 

that many of them are more useful than the metals of 
which they are composed ; and possess properties a good 
deal different from their elements. The most useful of 
all alloys^ hrass^ is composed of zinc and copper : it is 
harder^ more easily melted, more close grained, better 
coloured, and less liable to tarnish, than copper ; it is 
less brittle, and in every way more serviceable, than 
zinc. Pinchbeck is composed of the same materials as 
brass, but in different proportions, the zinc predomin- 
ating. Of copper and tin — two very soft and flexible 
metals — are composed the aUoy called bell-metal; 
which is harder than iron, very brittle, and sDnorous. 
Of the same materials, but in different proportions, are 
composed mirrors; and the kind of ordnance, impro- 
perly called brass cannon. Pewter is composed of tin 
and lead, sometimes with the addition of zinc, copper, 
or bismuth. Plates for stamping music are composed 
of tin and antimony ; and printing types are formed 
from the alloy of antimony, lead, and, perhaps, a little 
bismuth. Tin foil is an alloy of lead and tin ; and 
plumbers* solder is composed of the same metals. Fu- 
sible metal is bismuth, lead, and tin. The amalgam of 
zinc and mercury is used for exciting electric machines ; 
that of mercury and tin is the compound employed for 
what is called silvering looking-glasses. The alloy of 
gold and silver with copper, for coins, has been already 
noticed. 

In our search after the metallic productions of na- 
ture, we by no means generally find them disseminated 
through the earth in their metallic state. Sometimes 
they do occur native. Gold is found slightly alloyed 
with silver or copper. Platinum is always found alloyed 
or mixed with iron, palladium, iridium, rhodium, and 
osmium. Copper, silver, mercury, antimony, bismuth, 
arsenic, and teUurium, occur both in the native metallic 
state (although never perfectly pure), and also mineral- 
ised by other bodies. Lead, zinc, tin, antimony, iron, 
&c. are constantly found combined, ox ia\Tvet?iX\^e;^\3rj 
galpbnr. Afetals are often found combmeOLm\)a.Q^^%«swj 



with oxygen and carbanic scid. The cambina 
a raetal with its mineralising substance is called n 

in tile state of ore that nieuls oi 
are not found native. Ores soraetiines j 
luBtre ; BonieCinieG they appear atony, i 
earthy. In many inEtances they are cryslalliseil It 
regular forma ; and often they are amor|ihou5 (ihipe- ' 
I iesB) maEKes. Ores are found in lai^ lissures in rocb, 
1 called vdin ; and often in beds of earth. The re- 
duction of them to the metallic state is, geaeraJlj,! 
I difficult process. 



[- In treating of organiEcd bodies, we have shown duli t 

I notwithstanding the yariety of aspects under viiA ' 

' vegetable substances are presented to us, and tb 

striking difference of their properties, they are sQ 

composed of four ultimate elements. The combJu- 

Btiona with each other, into which these enter, are, 

however, various ; and each form of combination pro. ■ 

duces a substance of a different kind. These Bub< 

Es, associated with each other more or less nu- 

' merously, compose tlie vegetable structure ; and, being 

the more immediate objects of sense, in the investigation 

of any oi^^isation, they arc called their proximatt 

principles. Existing ready-formed in woods, rootSi 

leaves, fiowers, fruits, and seeds, we find a considerable 

mber of proximate ^riud-^XeB, as atvds, alkalies, sweet 

jirinrfples, bitter prmci'jVes, oiis, exM&fmata,-. ustib 



KtU A0n>6 OF YEOETABLEB. 27$ 

onous^ others wholesome; some spontaneously se* 
iting^ others remaining obstinately combined. To 
I a brief account of the chief of these^ is the object 
bis chapter. 



Section I. 

ACIDS OF VXOETABLES. 

Htric acid, — The acid of lemons exists in their 
i, combined with a considerable portion of mucilage^ 
:h disguises its properties^ and renders it perishable; 
is^ therefore^ been an object to remove this^ when 
icid is to be preserved, or when its real properties 
X) be examined. The process which succeeds best, 

present to the juice any substance which has a 
iger affinity to the pure acid than the mucilage 

and whidi, by forming a compound that water 
ot dissolve, will permit our washing it with water 
move the mucilage. The substance added is then 
; withdrawn, and the acid remains pure. From 
jatin word, citrus, a lemon tree, this acid has been 
i citric acid. The outline of the process is as 
ITS : — Add to strained lemon juice as much pow- 

1 chalk as will saturate it. A powder subsides, 
which the liquor which floats above should be 

ited ; and the powder washed with various afiu- 
of warm water, until the washings come off with- 
iste. Dilute sulphuric acid should be heated on 
owder : the acid liquor should then be pressed out 
gh linen, — and evaporated, until a pellicle appear 
B surface ; on cooling, crystals will form, which, if 
'bite, are to be dissolved in water, and the liquor 
id, and again evaporated. In 100 grains of these 
ds, there are 23^ grains of water, and the re- 
ng 76^ are pure acid, in its most concentrated 
The«e 76^ grains of pure acid are coto^o^e^ ^1 
yf oxygen, 31-58 of carbon, and ^'63 oiV^^o^esi, 

X 



I 
I 
I 



r«76 

wnnftining 88 parts are the pure anhytlrouB acid, com 
posed of 32-39 parts of carboOj 52-97 of oxygen, ani 
M-64 of hydrogen. 

This acid exists abuntkntly in other fruits, but ei 
pedally Id the tamarind ; in the grape it exists »!«){ 
with citric, raalic, and an acid called iiinic, which k- 
aembteB tartaric acid in many respects, but diRerfi Ctm 
it in others, and concerning the nature of which ahaoS 
nothing is known : these four constitute the agre«abk 
tartness of the juice of that fruit. 

Oxalir iwid. — The plant called sorrel is valued fi 
its acidulous taste. This acidity is owing to the pre- 
■ence of a peculiar acid, which may be separated from 
the juice, and from the potash with which i 
hined, by a process analagous to that described for Ae 
preparation of citric acid. It has obtained the n 
at oxalic acid, from the generic name of the plant, owB* 
atxtoiella. 

This acid forma readily into regular crystali, of 
■which one half the weight is water, the other half beillg 
pure acid. It is a remarkable circumstance in its ooo- 
Btitution, that it contains no hydrogen, and that it too- 
sista merely of carbon and oxygen, — there being twice n 
much oxygen as there is carbon. So that it difibn 
from carbonic acid merely in the relative quanUtietof 
its ingredients. OxaUc acid can be prepared fay an ar- 
tificial process, with great ease, from Bugar, and $ timet 
its weight of nitric acid,— the former affording the car- 
bon necessary to its formation, and the latter die 
oxygen. It is only necessary to heat the nitric add 
on the sugar ; the sugar dissolves, and there is a violoit 
effervescence, which must be moderated hy immersion 
in cold water : when the mixture cools, crystal* of 
oxalic acid form in abundance, which may be puri&ed 
by a second crystallisation. 

Oxahc acid is an active poison ; many persons have 
/alle'i victims to its virulence, by having swallowed il 
3D mistake for Epsom salt, -wtecV V 
pearance. la all proba\>i^t'j , t\ii* ^oAi ^i 



OHAP. II. ■ ACIDS OP VEGETABLES. 277 

lie the only vegetable acid capable of acting as a poison. 
Chalk finely powdered^ and difiused in water^ is the 
proper antidote to the poison of oxalic acid. 

Gallic ticid, — We have now to consider an acid of 
a much less decided character^ although possessed of 
striking properties, than any of the foregoing : it is 
obtained from gall nuts ; and hence has been called 
gallic acid. The process for preparing it is very simple : 
introduce coarsely powdered galls into a glass retort, 
md heat the belly of the retort gently and gradually 
intil crystals form on the neck. These crystals are 
;allic acid, which rises in vapour from the galls in 
consequence of the heat : the vapour, as soon as it 
Mimes in contact with the cool part of the glass, con- 
lenses, or becomes solid there ; and new particles of 
idd continually fixing in the same way, and joining 
ach other according to the symmetrical arrangement 
lescribed in the chapter on cohesion, crystals are formed 
ust in the same manner as if a liquid by cooling had 
irystallised. Whenever a solid is thus converted into 
vapour by heat, and the vapour by being cooled again 
)ecomes soUd, whether assuming the form of crystal or 
lot, the solid is said to have been sublimed; and the 
process itself is called sublimation, because it is gene-i 
•ally performed in tall vessels, — the soHd taking a high 
station in the vessel, as it could not cool nearer to the 
(ource of heat. 

The claims of the gallic to be considered as an acid 
ire not very decided. It has been stated by Berzelius, 
;hat it does not redden Utmus ; but others affirm that 
t does. Its taste is scarcely acid ; it is rough and 
jitter; but it possesses the property of neutralising 
ilkalies, and of expeUing carbonic acid from the car- 
bonates. Its most remarkable property is that of 
changing the colour of solutions containing iron to an 
ntense blue-black colour; and it is partly owing to 
he co-existence of gallic acid and peroxide of iron in 
Dkj that its black colour is attributable. 

T 3 



) 



The crjEtals of ihis acid <lissol*c in 
weight of water at )>0°, or twice their weipht of wita 
■t2I2°. 100 grains of it connsl of 56-95 carbon, S7'S 
Qxygea, and 6*55 h^ilrogen. 

Other acidf. — There are a number of other Mil, 
which, being of little use, and not possessed of inj n- 
markable properties, it will be sufficient merdj U 
allude to. 

Benzoic acid is contained in the odoriferous reA 
called henzoen or tenjamin, and may be obtained llf 
gentle niblimstion in the same manner as gallic aocL 
Moroxylic arid ia proiluceil from the bark of the uniL 
berry tree ; iilmir acid from the bark of the etei, sn* 
fimn varioufl other vegetable sources : khiie acid ii pro. 
cured from the hark of the cinchona tree, — the mat 
which aSbrils Peruvian bark. From turpentine, n 
exudation from various species of pine tree — are derived 
«iAnc and /fjijj'' acids. From poppy-heads is obUunel 
metallic acid : from carrots anil other vegetables, puftU 
add may be separated. The roots of the liraiiwril 
triandra, or rhatany, a Peruvian mountain shrub, cootBl 
krameric acid. Asparagus shoots afford airpartie Bcit 
I The seeds of the rro'nii ligliiim furnish crolonie oeU. 
I Besi<le the foregoing, there are three or four others not 
i worth naming. 

I The acids which have been just described exist 

I Tea<ly formed in the fruits, barks, seeds, Eeed-capaaks) 
rootSj &c. of plants ; they are simple edueU. Bot 
there are others having a vegetable origin, which do not 
I exist in plants as acids, but niay be formed by chemicll 
[ phangea proiluced on certain elements contained in 
I v^etabtes which afford the base of the acid : these »m 
[ scid pToducU ; some are produced by the agency offing 
I others by the action of nitric acid. 

I When citric, sorhic, kinic, tartaric, and mucic «ddl 

[ are distilled at a high temperature, they undergo de- 
composition ; and, by a new arrangement of the ele- 
, ments, new acids are obtaivitA. "TVieit ■na.-mc* -nnMMi 
itbe same, with the word pyro at a ^tA'*-, iefvi^&lM 



4IE1P. n. A€ID0 OV VEOETABLES, 279 

^, fire^ indicating the manner of their production 
Thns^ we have pyrocitric, pyrosorbic, pyroMnic, pyro^ 
tartaric, and pyromucic acids : they are all capable of 
assuming the crystalline form ; and differ materially in 
Iheir properties from the original acids previously to 
iheir being altered by fire. 

. There are other acids generated by similar means, 
bat they have simple names without any prefix, because 
they are not known to exist in any previous acid state. 
Thus, amber, a substance of vegetable origin when dis- 
tilled, affords an add in crystals called succinic {succi^ 
num^ amber). When castor oil is distilled, two acids 
are generated ; they have been named ricinic and elai^ 
edic acids. 

When potash, a substance chiefly of vegetable origin, 
is exposed to a powerful heat along with carbon, an 
acid is produced, which, on account of its saffi*on colour, 
is called croconic acid. If pinic acid be exposed to 
heat, its nature is altered : it becomes a new acid, and 
has been called colophonic ; but this is an unnecessary 
innovation on the established method of nomenclature ; 
it should be denominated pyropinic acid. The acids 
which follow are generated by the action of nitric acid 
on a compound vegetable basis. 

Carhazotic acid. Indie acid, Aloetic acid, — Indigo, 
when acted on by nitric acid, affords products which 
vary with the strength of the nitric acid employed. 
When the acid is strong, and its action on the indigo 
is maintained by a moderate temperature, the latter 
dissolves with considerable effervescence, and a solution 
is obtained, which, on cooling, deposits transparent yellow 
crystals. These, when purified by various processes, 
eonstitute what is called carhazotic acid, — the name being 
derived from the circumstance that carbon and azote 
enter into its composition. 

This substance reddens vegetable blues, yet its taste 
is only bitter. It may be sublimed by a slow heat ; 
\fat hy a strong and sudden heat it i* "kVcv^e^, «xv^ Na* 
consumed with a yellow flame. It iotm% a. n^tvsX^ ^"^ 

T 4 




7CiTM»b^ wbdi Wve ^ and tiiK 

I ineif aav^ ■> Ae flw 

' > if *S*&* prt 

, 40-«M oTpn, ad 1V142 a 

■MttoTdK «a 

Airda, tlie izoie doable, utd the mjgev die a 
Uk qoanlitia which compose iaAc acid. This i^ 
pun bj the anaijsis of Dr. fioC When incEe tbl 
1 b)f strong nitric ■cid, it 




^^E. Bnfoniwt had diwoTeFeil, that irheii nitric add i* 
^^M^etttd 00 aloe«, a fdlon floculent precipltote appeal), 
^B jeiy little toluble in watet, and, wben pure, maoiffacitig 
^V Ae propertici of a pecidiar acid, which he called aheti' 
^^>- tel4. When this or its cryEtaUised combinatioD widi ' 
^H; fMUuth it hi»ted, it iletonateE with a purple flame ; in 
^V the Utter case the nnell of hjiilrocyanic acid is perc^ 
^M liblf . Liebeg obtained the same results, but he wis 
^B<«llled inio the belief that nitric acid enters into the 
^HH^ompoiiitiiiii of aloetic acid, and is combined with t 
^H pMuliar bitter principle of aloes not passessing the pr»> 
^Hj^rtim of an acid, 
^H But whatever might he the nature of aloeCic acid, he 

found that it posaesses some extraordinary propertiea. 

Rllk bniliil in its solution acquired a beautiful purple 
"/lour, wliicli was not affiecuA ^I'j s*ii'^, ntn V-j aa^ 
adil cxcqit nitric, and llua iAia»ei4 \V \n ^tf&n-ii ■,>!«. 



OHAP. n. • AOIDS OF VEOETABLE8. 281 

mere washing in cold water restored its former fine 
purple. He found that all shades may he given by 
proper mordants. To wool^ a particularly heautifiil 
black is communicated by this substance^ on which light 
has no influence. Leather takes a purple^ and cotton 
a rose colour from it, which gives way to soap. To 
silk it also communicates a rose colour, — the only per. 
manent one known. 

M. Lieb^ afterwards found that he, as well as Bra- 
connot, had mistaken the nature of aloetic acid. His 
new researches informed him that aloetic acid is a com- 
pound, consisting of carbazotic acid, combined with a 
peculiar substance possessing the properties of a resin. 
Carbazotic acid, he found, is an excellent test for dis. 
covering potash ; the carbazotate of potash requires a 
lai^e quantity of water for its solution ; hence, when 
dropped into solutions of potash, even of sulphate of 
potash, a precipitate is produced. Nay, it occasions a 
precipitate in infusion of litmus, on account of the 
minute quantity of potash which that substance con- 
tains. 

The action of nitric acid on indigo was first observed 
by Haussmann ; he obtained a bitter substance from it, 
which he did not recognise to be an acid. It was 
called the bitter principle of Haussmann, but was really 
impure carbazotic acid. Welter ascertained that, by 
digesting nitric acid on silk, a bitter principle, which he 
called amer, is also produced, and it was supposed to be 
identical with that obtained from indigo. Liebeg in- 
vestigated this subject ; he obtained from silk the same 
crystalline matter as from indigo; showed that both 
form the same compounds, and that they are, in short, 
the same acids. Chevreul had denied that the bitter 
principle is an acid ; he considered it to be a combin- 
ation of nitric acid with vegetable matter ; but he as- 
certained that an acid may be procured from indigo by 
the action of dilute nitric acid. This is the acid to 
which the name of indie is here giveiv. 
Mt£€io acid. Camphoric add. Suberic acW-.— ^^ 



I 



Kctinj; on gngar qfmilk with nitric acid, both undogo 
omposition, and an acid in the form of a vhitt 
powiler is produced, which is called saclaetic acid (etc 
charum l&ctis). If nitric acid be made to act on pun 
Arabic, tite ver; same acid is formed ; and hence it his 
also been named mucic acid, and considered t« be i 
yegetable acid. If camphor be similarly treated with 
ric aci<l, we obtain a substance in crystals, called 
OlinpAoric aeid. And if cork be acl«d on by nitric 
rl, a crystalline acid is };enerated, called .ruAeHc, froDi 
, tuhcr, the cork tree. 



It has been discovered that acids are not the only 
daes of bodies which constitute the most deddedly 
characterised component parts of vegetables. It ii 
known that alkalies exist already formed in the plant 
as one of its constituent parts, in the same way tt 
acids, and with far more decided properties; and it 
is certain that they are not generated, as is the caie 
with potash and soila. Several of the substances which 
bave been announced as alkahes, manifest alkaline pro~ 
perties in so undecided a manner, that they have lieen 
distiuf^shed by the term lUkaloids, in order to imply 
B relation or resemblance, rattier than an identity with 
the alkaline nature. The properties of these substancei 
are not of sufficient interest, at least to the chemist, to 
call for description in so small en elementary treatise,as 
diis : a few short notices shall suffice. 

Quinina and Cinchnnin are alkalies, which have b*«n 
discovered existing in the different species of cinchona 
bark, in combination with kinic acid. They have a 
considerable resemblance to each other, but are suffi- 
ciently (Jisringuifihsil iu ceitaiw ^'^ai^ttve?,. T\».^ have 
3 bitter taste ; they tiealta^ae acvia, tni iwro cit*^ 



GHAP. n. ALKALIES OF VEGETABLES. S83 

luable compounds^ some of which are used m medicine ; 
and are supposed to concentrate in them all the medical 
efficacy of the cinchona barks ; but it seems probable 
that this conclusion is founded on insufficient or exag- 
gerated grounds. Cinchonia readily crystaUises : it is 
insoluble in cold water^ and requires 2500 times its 
weight of boiling water : alcohol and ether dissolve it. 
Quinina possesses nearly the same properties^ but it 
does not crystallise. The alkaline properties of both 
are strongly marked. Morphia is an alkaline substance 
obtained from opium^ in which it exists in combination 
with meconic acid. It has been supposed to concen- 
trate in itself the sedative virtues of opium ; while the 
stimulating effects of that medicine are imagined to 
reside in a different principle, narcotine, which may be 
obtained from opium in a separate form, and which 
does not manifest the properties either of an acid or 
alkali. On this subject Mr. Brande observes, " It must 
be admitted that the composition of the active prin. 
dple in crude opium is yet but imperfectly understood : 
and it is possible that narcotine, in some pecuHar state 
of combination, may contribute to its powerful qualities : 
it cannot be admitted that they are referable to morphia 
only, for 100 parts of opium do not yield more than 
7 of that base; so that were morphia the true active 
essence of the poppy, it should produce (when extracted 
in its active saline state of sulphate or acetate) effects 
commensurate with the fourteen-fold concentration 
which the opium has undergone. Yet morphia, or 
rather its soluble salts, may be given in nearly the same 
doses as crude opium ; and a grain of opium and a 
grain of acetate of morphia are not widely different in 
their operation as sedatives." If these facts have been 
observed in a sufficient number of cases, they seem to 
negative the statements which have been made with 
legard to the relation of acetate of morphia and mor- 
phia to opium, in point of strength. The foTvoet \% 
siBrmed by OrSla to be one of the most Tpo^etio^. tvbx- 
cotic poisons of all the salts of tliat aSkal^-. axv^^^.- 




IioibI bait gnm p^ind 
E^rtia^ tbe ificenntanar M tt 

i^er wfaick ttie 



Much ia yet w faen 



bauTits is met uwin^ 
The eipenniean: seems, buirvvis, i 

adds in the -ttmssdi mav ash d 



of aH tbe sniwtuiiEs in nature, aad pMBMt 

ite prnpcny iif inihicbl^ sjlnpllMK o( dK 

cded locked jsw. Ir maj be ani M he am^ 

h h^ of latB been DBd ncd k 

% in paraljtii: a^cui 




I*!. It reiiiiira 500 JMrt 
I ikafafd, hot 
h baa Ikcd ^Oiacttd fans ifae bark of ■ 
in Abj^bm, calird wga|;uMair, or ftrwM 
mtUHjftmtfriea. It haaaho faecBcdkd ^fae anguslaf^ 
■ml wai «old for real angmtnrs, — a fraud <n- mkli&e 
which at the time created dreadful contequraiwa. It 
b itini^Iar thai Mr. Bruce, the celebrwed trareBer, 
whme name the bark bean, beiog attacked, while in 
AhyMrtnia, with the dymiieiT which ravages tiilt 
mtry, WSd actuallj cured b'j uking a heaped te*- 
nfal of ihc powdeted \ffli\; o^ *fee ^wi*- vmaee ^-iK\. 
ifaCTiiniUnce wtacb miMoei ^«" vi \<rrot «*. 




CHAPrU. VEGETABLE PRINCIPLES. ^85 

seeds of so valuable a plant to England^ where it has 
gprown. The effects of this dose do not seem to cor- 
xespond with the known character of the alkali which 
has been extracted from it. Perhaps brucea^ in small 
dosesj might have beneficial ^fleets in the dysentery of 
this climate. 

Digitalia is said to be an alkali procurable from the 
leaves of the foxglove^ or digitalis purpurea. The 
only substance which I could find in foxglove leaves^ 
that seemed likely to be the active principle^ was a sub- 
stance possessed of the most intense bitterness ; but I 
did not observe that it was alkaline. I suppose that 
this bitter substance is the narcotic principle merely^ 
from the analogy of other violent narcotics^ which are 
almost always bitter. 

Hyoscyama, Atropia, Veratria, Emetina, &c. are 
derived from henbane leaves^ deadly nightshade leaves^ 
white hellebore root^ and hippo root^ &c. : they need 
not be described. 



Section III. 

OTHER PROXIMATE PRINCIPLES OF VEGETABLES. 

Having now briefly described the acids and chief 
alkalies which are found in vegetables^ we proceed to 
some other proximate principles. 

If we take any recent vegetable, and boil it for a 
length of time in water, then pour off* the water, add 
new water, and boil again, and so on, five or six times, 
the plant will be much changed in its nature. It loses 
its taste ; its medical qualities, if it possessed any ; per- 
haps its colour; and most generally nothing remains 
but an inert fibre, possessing no other properties than 
those of wood, and resembling common wood in all its 
physical qualities. It is, in fact, woody fibre, and 
constitutes the solid basis of aH vege\;ai\A& ^\xvv<^Xxa^^. 
Jt is called lignin, from lignum, Yfood •, asiA. Vt ^qtqsJ^- 




inwrinbtUtj in water ; tfaor aadj Kddffitj in ikaU, 
irilb wtucb tbej gtomallj fOTBi m vanuali ; and i~ 
re-appeariDce in ihe stale of afine wlute powder Aoi 
in the liquid, when water is added to tbeir akritdRa 
■olution. If a resin be betted, it gcnenllj metal ; W 1 
on cooUng, it haidens again : if much bewed, it burnt 
vilb a deiue flame and mnch enwke. When a ttan n 
exposed to heat in a distilling apparatoc, the odotiftroiu 
oil diitili over, and leaves the Tesin b^ni) ; and so fn 
altered, that it is now harder, darker colouied, and, conu 
paratively, destitute of sroelL In this odoriferoua oil 
ia mippoied to reside almost the whole of the medted 
viitnea which this class of bodies are sometiiDes valtied 
for posteising ; and, being considereJ tile chief ingredient 
or the e»teiKe of the thing, it has obtained the name of 
ttiKnlial oil. From the circumstance of its speedily 
evaporating, or (l;ing off, when ex]M>Eed to the air, it ii 
■Iso called volatile oil. 

Eiwntial oils vary much in their physical qualities: 
their mnell and taste, both pungent, dif^r in each case; 
their colour ia generally very light when newly distilled, 
but by age they become brown : tbey an; mostly pale 
yellow, but some are green, and others blue. When 
shaken with water, they appear to mix for a moment; 
but in a few miimtes almost the whole of the oil eitber 
k awims or subsides to the bottom, according to its spe- 

Kryciit and peculiar taBW oS ^.tee o*-". a'?^«>'^*^»™* 



CBir.n. VSGETABLB PBIXOIPLES. 289 

of the oil has remained in solution. Time causes a 
SKBter quantity to dissolve. 

£t8ential oils are obtained from resins^ from the bark 
of the wood^ from the wood itself^ or from the leaves^ 
flowers^ or rind of the fruit. The seeds of plants 
^tlmoit always contain an oil ; but its nature is gene- 
nfly different from that of an essential oil. When 
exposed to the air^ it does not evaporate^ but leaves a 
&iuy stain^ and remains fixed ; and from this circum- 
itanoe it has been called fiaed oU, in opposition to volatile 
ofl. Some seeds^ however^ contain a volatile oil of great 
.ftignuDce. 

Fixed oils have always a greater consistence than 

volatile oils ; their taste is mild and bland ; they do not 

dJHolve in any quantity of water ; and they are much 

leas. inflammable^ generally requiring to be heated to 

their boiling pointy which is in all cases high^ before 

they catch flame; while volatile oils catch flame at much 

lower temperatures. Volatile oils are inflamed by the 

afiiudon of nitric acid ; but flxed oils require a little 

solphoric acid to be mixeTl with the nitric. The former 

disiolve readily in alcohol ; but of the latter a few only 

disaolye. 

There are two substances found in plants which seem 
to have some analogy to flxed and volatile oils ; these 
are lotup and camphor. When wax is melted^ it possesses 
many of the properties of a fixed oil : it may be consi- 
dered both as a vegetable and an animal substance. It 
is known to be wax that constitutes the varnish on the 
leaves of trees^ which proves it to be a vegetable sub- 
stance. Bees^ when confined in a room^ and fed with 
SDgar^ will produce a comb composed of wax ; the sugar 
has^ therefore^ been converted into wax by the animal 
process which it undergoes in the bee. The myrica 
oerifem shrub produces what is called vegetable wax. 
A good shrub aflbrds seven pounds of berries^ and these^ 
boiled in water^ give out one pound of greenish wax.. 

Camphor aeems to possess the properties oi «t coxicteXe 
volatile oil to a certain extent, although it laust \i^ «^^- 

u 



290 

mitted to be matter of quite a distinct nature from iQ 
other bodies. It is volatile; has a pungent taste; acarcclj 
diiiEolves in water ; is eoiuble with facility in klcohd, 
from which it may be again Keparated by mixing watei 
with the solution. It also dissolves readily in oiIb, whe- 
ther fixed or volatile. It is obtained by sublimadoi 
from llie laurus camphora. But a small quantity m. 
turally exudeB from the trees in grains, and falls to [hi 
ground. There ia a very precious sort in Ceylon, wbid 
is never imported into Europe : it comes from the root 
of the cinnamon trees. 

A class of bodies should also be mentioned, in alm« 
every tespect resembling resins,except that one of aSbid 
ing a substance when submitted to distilladon, whio 
resins do not. When heat is applied to these substance 
a volatile oil, as usual, makes its appearance, and trickli 
down the sides of the vessel. But a little nearer to til 
source of heat, we Hnd a vast assemblage of brillitui 
white, downy crystals, of great beauty : they have 
fragrant odour, and an aromatic taste : they dissolve i 
S4 times their weight of boihng water; and the solutic 
reddens litmus, and neutrahses alkalies. Hence tlie 
crystals are an acid; and as they are generally obtain 
from a resin called benaoen, the crystals are call 
benisoic aeid. 

Any resin, whether soft or hard, which, when heat 
in a distillatory apparatus, affords an essential oil, tl 
benzoic acid, is designated by a pecuhar name : it isn 
then called a resin, but a AuArani. There are, howevi 
substances of a resinous natiure, which are commov 
called balsams, but which, as they do not afford beii» 
acid when distilled, are improperly so called : thus, t 
substance called copaiba balsam is merely a resin 
turpentine, it afTording no benzoic acid. 

There is another variety of resins, called gum reair 
they are so named, because they are composed partly 
I resin and pardy of a gum. 

The chief propenJes oi inue ^m — gwa Arabic, i 
\_ipstance — are, transparetvc^ , ' 



bility in water, viscidity of the solution, capability of 
cementing fragnienCs, and of affording a varnisll, its 
total insolubility in spirit of wine. 

The properties of jum resins are mostly intermediate 
between those of gum and resin ; if they be digeeted ia 
water, the gum disgolves, and leaves the resin insulated; 
if they be digested in spirit of wine, the tesin dissolves, 
and leaves the gum insutated ; and if they be digested 
in a mixture of spirit of wine and water, the effect of 
the two solvents ia exerted, or, rather, a liquor of new 
powers is thus produced, and a great part of both the 
pum and the resin dinsolves. Such a mixture U, there- 
fore, made use of in pharmacy for extracting the virtues 
of ^m resina, when they are to he used aa medicines. 

Something aUied to the nature of resina, altliough 
essentially different in most of its properties, is the 
substance called CaovCchouc, otherwise named Indian 
rubber, or gum elamlic. It is the exuded juice of s 
pecuUar tree, which gradually pom's out when the hark 
ia stripped. It ia a milky liquor, that hardens when 
exposed to air, and becomes so elastic as to permit its 
bein)!; drawn out into threads. A tolerably strong heat 
melts it inta a liquid, which forms an excellent tranB- 
ptkrent varnish, apphcahle to iron utensils, in order to 
prevent their rusting. Caoutchouc dissolves in essential 
oils, particularly that of turpentine, in coal naphtlia, 
and in ether ; but it does not dissolve in alcohol or 
water. Its solutions are used as elastic and air-close 
vamishes. It is, according to Faraday, composed en- 
tirely of carbon and hydrogen. 

A substance, in external appearance somewhat re- 
sembling newly solidified caoutchouc, may he obtained 
from whealen flour. A quantity of flour is made 
into dough with water: the dough is then well worked 
in the hand under the surface of a large quantity of 
water, until it no longer whitens the water. M'hat 
remains in the hand is the subslance in question : 
it ia of a ^ray colour, somewhat liVe new caout&oMS 
biic ii does not grow black by age lite l\\e \a.Ue:t . V 
D 2. 



I 



eiceedingly elastic, aod ttiay be drawn onl U » llun 
film ; yet it wil] shrink with elastic force to iB timer 
dimensions, when alloweil to do to. It may be dtkd 
in a gentle heat ; and then it bemmes setnitranipuent, 
bard, and horny, and very mach resemUes gill& iQ 
its moiEt state it undergoes a putrefactiTe proccffi, •fitt 
trhich, and not before, itdissolve3,tdthoQgh notentiidy, 
in strong spirit of wine; and the solution is applicaUe 
to tlie uses of a varnish. From the glubnous natwe tt , 
this subelance, il has been cai]ed gluten. 

Gluten thus obtained ought not to be consideied a 
prosimale principle of v^etables, if it be true, as hu 
been affirmed, (hat it consists of two other prosimaie 
principles, which may be separated by kneading gluten 
in alcohol, until the spirit takes nothing further bata 
the gluten. By evaporation of the spirit, a seniittant- 
parent, yellow, brittle substance isoblained, of asweetiib 
taste ; it is combustible, and burns with a voluminciDE 
Same. This substance has obtained a name derived 
from yTja, gluten ; it is called gliadin. That part of 
the gluten which remained in the hand after beii% 
kneaded in the spirit of wine, is now hard, tough, and 
dark coloured. It is called by its discoverer siuioiM, 
from Xvi/.r„ a ferment ; hut in English it should be 
called Jiiviamin. 

Zimomin possesses one remarkable property, which 
may be turned to some account. When mixed wi& 
that gum reain used in medicine, called guaiaeam, &k 
mixture will, on exposure to the air during a few mi- 
nutes, become greenish blue. Guaiacum powder mixed 
with wheat flour produces a similar change, more 
intense as the quantity of gluten in the tiour iagreattx; 
«nd in this way guMacum may be made a measure or 
test of the quantity of this indispensable ingredient 
That flour which has been damaged, and in which the 
gluten is deficient, will afford a colour of little intenaty. 
Perliaps the ^me property may be found of uae to 
maitsteti and brewers. 

The facta rdatiag to miaomm. «n6. igi»Jao. ■«» 



CBAP^-It. VBGETABLE PBIN0IPLB8. ' 29^ 

or^nally brought forward by Dr. Taddei^ an Italian 
ehemist. They have been called in question by Ber- 
sdliu8^ who admits that the gluten obtained by kneading 
wheat flour under water^'is certainly a compound of 
two proximate principles ; but that one is the gluten 
of fbrmer chemists^ and the other a substance which 
has been found in various vegetables^ called vegetable 
oBfumeny to distinguish it from animal albumen^ here- 
after to be described. 

Vegetable albumen constitutes no less than one quarter 
of the whole weight of sweet almonds ; and^ according to 
Boullay^ is the basis of all emulsive grains in place of 
starch ; at leasts to the test of iodine^ there is no dis- 
coverable quantity of starch associated with vegetable 
albumen in «weet almonds. And Thibierge also showed 
that^ in mustard seed^ the basis is albumen^ not starch. 
In Boullay's opinion^ it is the great quantity of this 
substance present in emulsive grains^ which renders 
them indigestible. According to the analysis of Vogel^ 
vegetable albumen exists in bitter almonds^ but combined 
with oil ; constituting a vegetable cheese^ amounting to 
80 per cent, of the weight of the almonds. This 
albmnen^ like that of animals^ is soluble in cold water^ 
but is coagulated by boilings and rendered insoluble : 
both kinds resemble each other also in the common 
quality of counteracting the poison of corrosive sub- 
Hmate. — {Taddei,) It has been shown by EinhoflPand 
Vogel, that both starch and vegetable albumen exist in 
the nutritive grains ; the latter only in a very small 
quantity. 

The water in which flour has been kneaded, with a 
view of separating the gluten, is rendered white with a 
quantity of floating powder. If this water be allowed 
to settle, a flne white sediment will subside which, 
when collected and dried, constitutes starch. 

Starch dissolves in neither cold water nor in spirit of 
wine ; but it dissolves in hot water with facility, and 
forms a kind of jelly of well known use. 

One of the moat remarkable properties oi sXax^> ^^> ^^ 

V 3 



I 



S94 

it is otherwise called, fei^ila, is that of being convettiUe 
into sugar by the action of diluted sulphnric ttdi 
When these two iugTedients are boiled togelliei' for agmt 
len|;(h of time, aud some chalk added, the hquor, i ' 
strained and evaporated, will f\irnish crystalline ipbc 
nJes of sugar, the quantity of which is about one tenth 
greater than that of the starch. 
Tertible into ardent spirit, like (be common kind. Btw 
a mixture of starch and water, exposed to each oUki'i 
action for two years, is found to contain sugar. 

A natural process, similar to this in its results, taket 
place in the malting of barley : the etarch of the grtin 
is converted into sugar, as will be hereafter shown. 
Starch also appears convertible into a kind of gum, by 
shghtly scorching it: it then dissolves in cold water: 
it is called in the arts, British gum. 

Starch is aflbrded, not only from the difierent kinds 
of grain, hut from potatoes, and many other kinds ti 
vegetable substances. Potato starch is often substituted 
lor another kind of starch, much 'in demand as an article 
of food, called amw root, which is obtained from the 
roots of a ^Veat India plant. The nutritious substanoct 
called sago and tapioca, or cagava, are merely varieties 
of starch CKtracled from different sources. The presenile 
of starch in any thing may be always detected by the 
azure blue which solution of iodine added to it produces. 

From thi.- facts stated, it appears that the nutritjoua 
grains consist of gluten, vegetable albumen, and starch ; 
«r, according to Taddei, of the two last, with zimomin and 
ghadin. The starch of potatoes, as well as that from grain, 
. is convertible, by means of sulphuric acid, into sugar. 

Sugar obtained in this way is by no means com- 
parable, in point of sweetness, and purity of flavour, 
with the kind which ordinarily obtains that name. 
The sugar of the sugar-cane need not be described. 
There are two kinds, soft and hard ,- the latter being 
the purer, although it may be still further refined. 
Either kind, if dissolveil in a atn^ ^ipOTift^-^ aJ-wwer, 
and exposed to cold, wifl totm toW "te^iuii sri^oia-- 




■ called eavdied sugar : llie colour of the crystals 

e as that of the sugar employed. ^VTien 

e of the Eugir-cane is aufficienlly purified and 

torated] the sugar crystallises in small ^ains ; and 

' i brown syrup which remains, is called mo- 

e average proiiuce of raw iiigar, from 100 gallons 
e juice, is 108 pounds ; and the average quantity 
Kfined sugar procurable from I cwt. of raw sugar, 
61 pounds, along with 18 |)ounds of bastards, and 
hponnds of molasses, — five pounds being waste in the 
The analysis of sugar will be hereafter given 
iideralion of fermentation. 
B derived from many sources : it is commonly 
led from the sugar maple tree, from beet root, and 
The first method is resorted to in America ; 
last in France. Grape sugar is easily crystal- 
— not into regular crystals, but into grains which 
1 groups of a tubercular shape, resembling those 
rvsble in cauhflowers. [Nothing is easier than its 
on : grape juice is to be saturated with chalk, 
1 with white of eggs or blood, and evaporated. 
e days, it assumes the form of a crystalline 
B. — {Tbmard, Trait/; iii. 201.) 
> The substance to which the name exttactiKe matter 
Tim been applied, is no longer admitted as a peculiar 
{VOximate principle. 1 1 is quite clear, that if a vegetable 
be boiled in water, removed, and the water boiled down 
to a soft-solid consistence, the result must be a mixture 
of all the soluble substances whicli the vegetable con- 
tained. There ia, therefore, no such thing as extractive 
matter known. 

But there is a substance obtainable from certain kinds 
of vegetable matter, by the above-mentioned process of 
extraction, which possesses remarkably distinctive pro- 
perties. It may be procured from oak bark, nut galls, 
and gome vegetable substances which have an astringent 
taste, by boiUag in water, and evaporal\n% t\\e ifccQiA\OTi 
• Panrraotht Sugar Cm^. Londrm.lMM.vs-li'l^ 



Hipo ELKHKNTs OF aamtamtr' iuiwuAV 

I to drTTiesB ; a mass will result, canlxining several ingre- I 
^ dients, — amongst which is one, in particular, of giW I 
importance in the arts ; it is called tannin ; and U is so I 
named because It is the inaterial employed in tamrii^ I 
leather. To obtain tannin in a stale of puritj-, a conu I 
pticateil process is required : in gall-nuts it is associated I 
with gallic acid. Dr. Turner recommends Mr. Wsi- I 
rington's modification. A concentrated hot infusion of I 
nut-galls is agitated with white of egp, and the irai.- 
ture filtered. Sulphuric acid is added to the liquor ' 
when cold, as long as a precipitate falls. The precipitate, 
consisting of sulphuric acid and tannin, is WRshed 
with dilute sulphuric acid, pressed in folds of blotting 
paper to dry it, disaolved in water, and macerated with 
fine powder of carbonate of lead. By filtration, a solo. 
tjon of tannin is obtained, which, by evaporation in 
vacuo, aSbrds a hard mass. Tills, digested in ether, 
filtered, and tlie filtered solution evaporated, leaves puK 

This substance is inodorous and colourless. It has > 
rough, astringent, bitter taste. When its solution is 
dropped into isinfilass dissolved in water, a precipitate in- 
standy appears, which is perfectly insoluble in water. Tbe 
same happens with solution of glue, or gelatine, hereaftn 
to be described. The gelatine, to be acted on, need not 
be in solution : it will succeed also in the solid state, if 
it can be penetraled by the tannin. The skins of 
animals are composed almost entirely of geladne. The 
process of tanning hides depends upon these relative 
properties. The skin is immersed in an infbsion 
of oak bark, the tannin of which, combining with the 
gelatine of the skin, renders the latter hard, dense, tongh, 
and insoluble, and counteracts its tendency to putrefac 
tion. The skin is now converted into leather, or it ii 
tanned. There are many substances which contain 
tannin, and may be economically applied to this uae. 
The tannin procured from these sources has different 
properties, and tlifferenl Yiaines, tte Wift»,\Kc«flfi called 
liuio and catechu, contain a Wge ojiarAi.^ (A'\a— ■- 



C0AP. m. ANIMAL SUBSTANCES. ' 2^7 

bat the properties differ in some respects. An artificial 
tannin has heen formed by dissolving charcoal in dilute 
mtric acid^ which possesses the property of forming an 
insoluble compound with gelatine : and is^ therefore^ 
capable of tanning. In some respects^ this kind of 
tannin differs from the natural. 

All kinds of tannin may be obtained in the solid, 
state^ by evaporating the water at a low temperature. 



CHAP. III. 



OOMPOyNDS OF SOME ELEMENTS AS PRESENTED BY 
THE ANIMAL KINGDOM. 

In a former part of this volume, it has been shown 
that vegetables are composed of lliree principal ingre- 
dients — oxygen, hydrogen, and carbon ; united, in some 
cases, with btoslH portions of azote. Animal matter is 
distinguished by the constant presence of a much larger 
quantity of azote : there is also generally a greater pro- 
portion of carbon than is found in vegetables, and the 
c^bon of animals is much less easily combustible. 
. Beside these elements, we occasionally find others, 
which are common to the three kingdoms of nature. 
These will best appear by stating the composition of the 
chief parts of the animal body. 

The solid part of bone consists of phosphate and car- 
bonate of lime ; but, beside these compounds, there are 
two other ingredients, which exist in recent bone in 
considerable quantity, and impart firmness to a struc- 
ture which, without them, would be brittle, and even 
friable. These substances are cartilage and gelatine. 
Fat is also present, which adds somewhat to the tough- 
ness. 

Cartilage may be obtained from bone, by immersing 
it for a length of time in dilute muiiatic ad^; ^'^ 
earthy and other salts, and the gelatine^ aie «iXV ^'s.^^^^ 



I ,1^ the acid, and a subatance remains, Btill preaerrii^ui 
% great degree the form of ihe bone. When the id- 
herisg acid is well washed away, the Eubstance wtucb 
remBins is cartilage : hut if the muriatic acid had been 
very much diluted, it will disBolve only the salts, and 
the residuum will consist of both gelatine and cartiUge< 
When bones are boiled for a length of time in walei, 
the gelatine dissolves, and the water, on cooling, vill 
gelatinke; that is, will become a tremulous jelly. The 
fat is found floating on the surface. The bone nm 
consists of the same ingredients as before, without ibe 
Ratine. If the original bones were derived from ) 
young animal, had been broken to powder, and bnled 
for a great length of time in water, both the gektine 
and cartilage would dissolve, and nothing would remsia 
in the bane but the insoluble earthy salts. The diffi- 
culty of dissolving away the cartilage increases wilb 
the age of the animal, and the quantity of the cartilage 
diminishes in proportion as the animal is old. The 
bones of very young animals are almost entirely car- 
liltige ; and the carriage of old animals is often pv- 
tiftUy or totally converted into bone. The skeleton rf 
lie oaaified man in the anatomical museum of Triniq 
College, Dublin, affords extraordinary instances of Ht 
conversion of cartilage into bone through disease, even 
in comparatively early age. The cartilage of some 
parts is more easily soluble in boiling water than othen ; 
and sometimes a portion will occur, which no boiling in 
water will dissolve. Bones boiled under the pressure of 
a Papin's digester more easily give out their gelatine 
and cartil^ie, but the taste of the solution is empyreu- 
matic, if not ammoiuacal : a loosely covered vessel ii 
best. 

When strong solution of gelatine cools, it becomes 
somewhat stifl' and tremulous. If the solution be boiled 
down considerably, the residuum, on coohng, becomes i 
hard, brittle, transparent substance. These changes 
are well underatood ii\ ihe culinm^ m^. WVew " 
or meat are boiled, the gelat-vne ™\tit\i fti<rj 



^BlA*ea in the water. This water, now consisting chiefly 

Htjf dissolved gelatine, constitutes broth or soup : and, if 

^Bb be allowed to cool, it will form animal jeUy, which 

^^■By be flavoured either with sweet or eahne and aro- 

^Rwtio condiments. If the mere jelly be boiled down so 

^Hkat the water Ehall be almost entirely evaporated, the 

^■datine and cartilage which remain will, on cooling, 

^■hlidjfy, and form the hard transparent substance called 

^■Mrtobfe soup, when it is obtained from esculent mo. 

^Htriala ; or glue, when it is prepared from indiscriminate 

Hparces, such as ekins, horns, hoofs, bones, and the 

Hletne of the cow obtained from slaughter-houses. 

^■^Tbus, bone is composed of a number of materials: 

^^Mording to fierzehus, it contains gelatine and cartilage 

^H^17, blood vessels I'lS, fluoride of calcium 2, phos- 

^BUe of liiae 5I'04, carbonate of lime ll'SO, phos- 

^BhMe of magnesia I '1 6, and so<la, with muriate of soda, 

^Hnd water, I'SO. Bone ashes contain also sulphate of 

P UnK, in some way generated during burning. When 

i bones are heated red-hot in a close vessel, the whole of the 

wimBl matter is dissipated except the animai rhareoal ; 

and this gives the residuum an intensely black colour. 

Bones thus burnt to blackness, and finely powdered, are 

known in commerce under the name of ivory black. But 

when bones are burnt in an open fire, even the carbon 

ia burnt off*, and the residuum is perfectly white : it is 

then called bone ashes, and is of extensive utility in 

various arts. During the distillation of bones, carbonate 

of ammonia is generated in large quantity ; and the 

larger, if much common air finds its way into the vessels. 

Beside this, an empyreumatic oil of insupportable fetor 

distilB over. 

The presence of gelatine is not confined to the bones ; 
it is also found in those fleshy collections of fibres called 
mtuiplet, in which resides the strength of the body, and 
which direct and originate the motions of the bones. 
Not only is this substance contained in muscle, but an 
additionsJ quantity may be formed by \»\1hi% ■nva*€ua 
for a great length of time in water. Ge\B.\iae w, ^ftaie- 



I 



I 



F-MO 

fore, one of the ingredients of muscle ; but thrae is 
another of far greater importance, and present in mudi 
greater quantity. When muscle is weU washed in le- 
peated quantities of water, from being red it changn to 
white ; mere inspection vrijl then evince that it is goid- 
posed of a vast number of fibres, and from this cirinnn- 
stance it is called fibrin ; the gelatine has been washed 
sway, and may be found in the washings. ItianiX 
here necessary to advert to the fat, the celluiai substance, 
the blood vessels, and nerves, which are disseminated 
throughout the substance of the fibrin constituting 
muscles. 

Fibrin, while recent, is elastic: but, when peribcdj 
dry, it is somewhat homy and transparent. In nntbo' 
state has it taste or smell. When dilute nitric acid i> 
made to act on recent muscle, axote in a slate of purity 
is given out abundantly. Fibrin or muscle is converted 
into a jelly by the action of strong acetic acid and heat; 
Bome azote is given off when the jelly is dissolved in 
water ; and, by strong sulphuric acid, the fibre it 
tinged into a substance called ieitciTie (Xeiikd;, white], 
without any production of sulphurous acid. The pro- 
cess is, to heat a piece of muscle, well washed and 
wiped, with about its own weight of sulphuric add. 
Dilute the solution thus obtained, when cold, with water; 
boil it for nine hours, constantly supplying the waste of 
water. Saturate with chalk ; filter ; and evaporate to dry< 
□ess. The residuum should be boiled in alcohol. On cool- 
ing, the alcoholic liquor will deposit leucine. It is a white 
powder, which has the taste of boiled meat, and, when 
heated, emits the emell of roasted meat. This substance 
acts as a compound acidiflable base. Nitric acid eon- 
verts it into a cry stalli sable acid, cdUed nilroleucic. 

Beside fibrin and gelatine, muscle contains animal 
albumen, presently to be described. But a much rooie 
important substance is also present: it is a kind of ex- 
tractive matter, which is supposed to be the chief in- 
gtedient that cominumcates V) saii^a wtvi\nQ\!a» ^heit 
iwctlliar taste and smeU; 4\i4 fee ^Wi?*-! liie ofisMtei 



OOAF. in. '* MUSCLES. TENDONS. ^1 

present, the better is the soup. It was discovered by 
Thouvenel^ and was named by Thenard osmaxome 
(eo-fbi}^ smelly l^tafxaq, broth). It may be formed by 
macerating and pressing slices of raw muscle in suc- 
cessive quantities of cold water ; evaporating the mixed 
waters by heat ; skimming off the albumen as it coagu- 
lates ; allowing the evaporation to continue gently until 
the consistence of a syrup be attained. This is com- 
posed of a little gelatine^ the salts present in the muscle^ 
and osmazome. By dissolving the syrupy matter in 
alcohol^ the olsmazome only dissolves^ and it may be re- 
covered by evaporating the alcohol. It is soluble in 
water ; does not gelatinise it ; and the solution is not 
coagulated by heat. Its concentrated solution has an 
acidulous taste ; and this is very perceptible in strong^ 
well made soup. 

When muscle is exposed for a great length of time 
to a constant stream of running water^ it becomes totally 
changed in its appearance. It now possesses some of 
the properties of spermaceti^ and is fusible and com- 
bustible : it is called adipocere* Nearly the same sub- 
stance may be formed by digesting muscle in dilute 
nitric acid ; or it is produced when dead bodies^ in great 
numbers^ are left in a heap, and covered up with earth 
in such a manner as to exclude the air. Some suppose 
lliat adipocere is merely the fat a little changed^ which 
is found disseminated throughout all muscle^ the fibre 
being decayed away. Others conceive that it is a real 
conversion of the muscular fibre into fat. I have ob- 
served that alum leather, cut small^ and digested in 
dilute nitric acid, is at length converted into a fat^ per- 
haps of this kind. 

Nearly allied to gelatine in their nature are the tendons, 
which muscles terminate in^ and which conjoin mus- 
des with bones ; the ligaments, which connect the joints 
of bones ; the membranes, which form cavities or line 

*" The poet Southey subjoins the following note to hisThalaba, ii. 155. 
-r ** The common people of England have long been acqaavntedk viWYv >^\% 
diaage which muscular Gbre undereoee. Before Ibe cueutQ&taxvce ^sa 

Jkbowa to pMlo8<^hen, I have heard tnem express a (V\«\i^e axv^\^»XXvvcv^\o 

apenaaceu, because it waa dead men's &L* *' 




ia ««ter b; kng boOing : 

There i* an abonilanl ammi 
fMmd in man; paiti <d tbe a 
albuinen : it ocean nearij in a Etalc of pariCT, in wbit 
ja called tbe rhite of tbe egg. It is sohible in c^ 
water, but coagulstec when iIk Bolotioa is boiled. Egg 
albatnen, b; cantiniwd tnodeiue heal, may be Boli£SBd 
into yellowish, brilliani flakes, which are still aoloUete 
water. 1 found that 12 avenge hen e^s aSbrd if 
onoce of perfectl)' dry albutnen. IVltile of ^gs inslalUlf 
decomposes solntton of cornwive sublimate ; a precipUe 
^ipears, consisting of calomel and albomen, which, rf 
ootuse, is not poisonous. Heuce, white of ^gs is ii«d 
as an antidote to the poison of coirosiie saUitnate. 

Of this albumen in the coa^lated state, along widl 
gdatine, are composed nailn, horns, and hooft. 

Tbe brain has been examined by VauqiteUn and 
John ; and, in this difficult analysis, a surprising coin- 
cidence between their resulu may be observed. It is a 
onrious fact, that in the brain of man no less than SO 
per cent, of tlie weight is water. According la die 
analysis of Vauquelin, 100 parts of human brain con- 
dst of aO parts of water ; 4'53 of white fat; O"? of 
red fat; 112 of osmaiome; 7of albomen; 1-5 of phos- 
phorus, united with the fats ; 5'15 of sulphur, biphos- 
pbate of potash, phosphates of lime and magnesia, and 
Other salts. Of such materials is the thinking ot^an of 
man composed. The spinal marrow and nerre* lie 
•imilarly constituted. The ratio of water in the brain 
of the call' is also 80 per cent. 

Of the fluids of the animal body, one only need be 
noticed, — the blood : this fluid is intimately connected 
with functions the most important to life of any other, 
— regpiration and the ^^eoerstion of animal beat. 
Of the appearance of \Awn\ ■w\ien ft.tW. iroww, little 
ueedbeEAid: it is weU toown w^ a winv'i«H>6W.T\iKA. 



"•Uft m- BBAW. — BMWD. 8091 

*Pd liquor, exhaling n vapour of a peculiar odour. ^Fhen ' 
It is left &t rest a few hours, its appearance is very much 
altered : it has separated intJi two parts ; one quits { 
liquid, of a greenish whey-hke appearance, and heucs I 
called iierum : the other is an elastic firm jelly, of i 
crimBon red colour ; this is called tlie craaaamentum, \ 
because il is of a thick consistenc*, and resembles a 
deposit. I 

This mass is generally a little cupped on its surface, i 
and rounded every where else. If drawn in a stale <^ i 
disease, it is sometinies much more cupped ; and the 
fibrin, separating from the colouring matter, appears on 
the surface of crasBamentuiu of a huff colour, hence ^ 
called the buff^ coal : tllese are frequently symptomH of 
the existence of inflammation ; and the cause of them 
has given rise to much unsatiefactory discussion. The 
crassamentum is less abundant in proportion as the 
animal is exhausted by disease, or has lived upon scanty 
or deteriorated food. In fcetal blood, the crasBamenbun 
contains leas fibrin than in more advanced life. 

If some crassamentum of blood be washed with re- 
peated portions of cold water, it totally parts widi ia 
red colour to the water, becomes white, and a fibrouB 
matter remains, which, when subjected to analysis, 
proves to be the same as the substance already described 
under tl)e name of fibrin, us obtainable from muscle. 

If the water used for washing away the red portion 
of tiie blood be evaporated to dryness, at a heat mucli 
under boiling, a very dark, almost blackiah red, Bab«^ 
stance will remain. This is the colouring matter of 
the blood: obtained in tlie fotegoing manner, it is sbhb 
hie in water, and in several acids and alkalies. SuL. 
phuric acid, diluted with 8 or 10 parts of water, 
and healed on the colouring matter, dissolves it, and 
forms a beautiful lilac solution. Nitric acid destroys or 
injures its colour. Alkalies form deep red solutions 
with it. In cold-blooded animals it is easy, with the 
aid of a microscope, to perceive abufidKM. iiiA ^iSoviies., 
Boating in the serum : and if human tilno4\»i a;^^a.'u^ 



I 



i 
I 



["304 

while cooling, and the fibrin which separates be W- 
niOTed, the liquid will, on etanding some time, ilepoflt 
the colouring nutter, which the microscope will di^ 
cover to consist of minute globules. This colounii 
matter is now believed to consist of animal maliH. 
The French chemists asserted, ihat it is corapoeed of 
the subphosphate of iron dissolved in seium : but diii 
statement has been proved tn be incorrect. The glo- 
bules, combined with peroxide of mercury, aSbrd a ' 
permanent red dye. Woollen cloth, impregnated widl 
solution of corrosive sublimate, and dipped in water; 
solution of the colouring, matter acquites a red tinge 
which soap does not remove ; and calico and hnen maj 
he dyed of the same colour by the same means, escept 
fliat the solution of the colouring matter should contain 
ammonia. The difficulty of washing out the stains of 
blood is well known, and has often been the means of 
detecting the murderer. There is, however, no doubt 
that iron exists in the red globules of the blood ; for, 
when they are burned lo ashes, it has been found that 
one half the weight of the ashes is oside of iron. The 
Other ingredients of the ashes are lime, phosphoric acid, 
and carbonic acid. It is scarcely credible, that 1 
grain of oxide of iron can communicate to 40 ounces 
rf blood the intense hue which it possesses : yet, W- 
cording to Pearson, this is the ratio of iron contained 
in it ; and the estimate of Berzelius differs very httle 
from this. Professor ^I'urzer has lately delected traces 
of manganese in the blood. 

What the cause of the coagulation of the blood may 
be, IB unknown. Some affirm that exposure to oxygen 
retards coagulatioTi ; others' say it accelerates it ; others, 
again, deny any effect to it. ' It happens in a vacuum ; 
and, it has even been said, more rapidly. The previoas 
health of the animal affects the celerity of coagulation : 
the lees intense the powers of life, the more speedily 
the blooil coagulates. It is found, that passing two 
ligatures round a vein, at a fc\a.wt» ^«kv eai* other, 
so as to include and conftme a q;iiwv'6vj <ii ""dwiiA,-^ 



^^*AP. ni, THE BLOOD. 305 

^fify^R it in a semifluid state for a length of time. And 
^€ know that the blood drawn by leeches, and retained 
itt their bodies for months, will be disgorged in the 
■Bine semifluid state. During fainting, in drowned 
persons, and those killed by lightning, the blood does 
not coagulate. The last fact has been questioned by 
Dr. Scudamore ; but, as I think, on very insufficient 
gnmnds. Coagulation is prevented by agitation, al- 
though the fibrin separates; or by commixture with 
solutions of certain alkalies and salts, although other 
salts and several acids promote it. 

The serum of blood coagulates when heated to 156^ 
or 160° y nearly in the same manner as the white of an 
e^ but the colour is not a pure white. If the serum 
thus coagulated be cut in slices, and pressed, a fluid 
will exude, which is called the serosity of blood: it 
consists chiefly of water holding a little altered albumen, 
and a little common salt dissolved. The coagulum 
that remains is albumen. Serum is composed of water, 
salts^ a little soda, and albimien. The ratio of water is 
90 per cent. 

In fine, it appears that blood is composed of t^o 
proximate parts — serum and crassamentum ; or, as the 
latter is otherwise called, cruor or clot : that serum is 
composed of the following subproximate parts, — water, 
albumen, soda, and some salts of soda : and that eras- 
samentum contains, as its constituent subproximates, 
fibrin, albumen, red colouring matter, a little iron, and, 
as some say, a little carbonic acid. 

In the body of an animal, a variety of fatty substances 
exist : some of them, at common temperatures, are very 
hard^ as tallow; others are soft-solids, as hog's lard, 
butter ; and others are fluid, as oils. In the small space 
that can be devoted to these substances, it would be 
in vain to attempt a separate account of each ; I shall, 
therefore, describe them generally, and enter a little into 
the nature of soaps. 
Fatg and &xed oils were consideied as "Wnxo^ew^^xv^s. 
proximate prmdplea of animals and ^\aii\:&, wjqnS^ "'^'^ 



I 



reaearcheB of CheTreuJ and firacunnot demonstrated thu 
ihey are mixtures of several. Chevreul, in his euly it- 
searches, found, that by heating fat in alcohol it dis- 
solved ; and that, as it cooled, a portion sepualed in 
crystals: another portion did not cryBlallise; it renia' 
dissolved ; andj hy distilling oS* the alcohol, the on- 
crystoUisable matter was obtained in the form of U 
oily fluid. The crystaUisahle matter he called (iMrmt; 
the oily fluid, elaine. Braconnot, witlioot being awiie ' 
of Chevreul's experiments, efiected the same sepantidn 
by a mechanical and more simple method. He wrapped 
up lard in many folds of blotting paper, and applied 
pressure : the paper absorbed a portion, but left a tea. 
duuni, which, when puri&ed by being melted in oil <tf 
turpentine, cooled, and agMn subjected to pressure in 
blotting paper, was a ilry, brittle, inodorous, Eemitraoa- 
parent mass, of a granular texture. It softened wiUi 
difficulty by the heat of the titigers: it was scarcel]' 
soluble in boiiing alcohol : the blotting paper, when 
boiled in water, gave out what it bad absorbed ; it wn 
a liquid oil ; J 00 parts of pork lard afforded 63 of fiA 
oil, and 3S of the suet. The suet described by Bn. 
connot seems not to be the same as the crystalU^d 
substance obtained by Chevreul ; for the former wai lib 
loluble in alcohol, and the latter was obtained by ciyt- 
taltisation of its alcoholic solution. Braconnot, hffw. 
ever, found that when his suet was acted od by an alkali, 
it was decomposed into an oil and adjpocere, both oT 
which were soluble in alcohol ; this adipocere, therefoit) 
is probably identical with Chevreul'a crystals. 

Braconnot has shown that various fixed oils, by bcJng 
frozen and pressed in blotting paper, may be sepaialBd 
into Btearine and elaine. The stearine was white, bril' 
liant, inodorous, insipid, and firm ; 3S parts were oh- 
tained from 100 of olive oil; and it required the tem- 
perature of 68" to melt it. 

Ciievreul next proteeAeA Mj mvcatij^ate the nature of 
various other fatty ^>oA\es,wii m.MSftie&'wi.swifiiiiix^ 
the existence oEBevetalive"H a.tC\Hii^otl»vv'aiK-^'^c9i». 



CftiP.m, PATTT PBINCIPLEE. SAPONlFICATroN. 3(^ 1 

In butter he discovered an oily liquid, which, at 32°, I 
iloeB Dot solidify. It is soluble in boiling alcohol, bat I 
not in water ; it has the peculiar unell. of butter, and ia I 
BometinieG white, eometinnea yellow : to this he gave the I 
name of hutyrine. From spermaceti he separated 9 " 
oynallieable matter, which he called cciine : from por* 
poise oil he procured an oil very soluble in hot alcohol, 
denominated phor.miine : and, in sheep's and deers' fat, 
be diaeovered kircine, a peculiar oii. 

When soap, composed of lard and potash, is difiused 
throagh a large quantity of water, Chevreul ascertained 
that a portion dissolved ; and another portion, iieing 
insoluble, was deposited in pellets of a brilliant white- 
ness, resembling mother of pearl. This insoluble por- 
tion W'as dried, and digested, in a large quantity of 
water, at about 60°, for ten davs during nhich time 
it had fiDed up. The liquid was then liiitrcii ; the in- 
•oluhie portion was well washed, dned, and digested in 
alcohol of 0'820 : part dissolved, and part did not. 
Muriatie acid being added both to the alcnhotic solution 
und the portion insoluble in alcohol, a fatty substance, 
in both CBsei, separated, which was soluble in boiling 
alcohol, and was deposited in crystals as the solution 
cooled. When well puriHed from alkaU that obstinately 
adhered to it, it was a tasteless, pearly, white substance, 
lighter than water : it melted into a colourless liquid at 
133° ; and, when cold, crystaUised into brilliant white 
needles. U waa soluble in boiling alcohol, but was de- 
posited in crystals as the solution cooled. To this sub- 
stance, ou account of its resemblance to pear!, Chevreul, 
at first, gave the name of margarine ; but finding that 
it reddened litmus, and decomposed alkaline carbonates, 
he called it margarelir, avid, — a name since changed to 
margaric ncid. 

The two portions of muriatic acid that had been 
added to the originai alcohoUc solution, and its insoluble 
teaduum, were next examined ; the potlionviVicVv ac^ei 
on tbe sohihle part bad taken up one lwe\ft\i oS \*a 
we^bt of potash, wbUe that which had acted oB li\e\M*i- 



^L mi 

^k POBI 



7 CREUiBcsv. TpMffnr 

]uble matter contained very amall traces of alkali. TIu! 
was the cause of the difference of solubility. It a^eiied 
that margaric acid combines with potash in two ym- 
portions, — forming a margarate nnd bima^^rate of 
potBEh. 

The original soap of lard and potash, when difitiscd 
in water, had partly dissolved; that which did notdii- 
•olve being the portion from which the margaric idil 
was obtained. The soluble portion was decompased b] 
tartaric acid ; and a substance was thus separated, poi- 
KBung acid properties : when sufficiently purified, il 
was very soluble in alcohol, insoluble in water, fudbk 
at a low degree of heat, and crystalli sable. Its colour 
is yellowish ; its smell often rancid ; its appeartux^ 
when liquid, oleaginous : it powerfully reddens litiaUi 
and combines with alkalies and earths. This is an 4aJ 
«ui generis; and Chevreiil gave to it the name of oWc 
acid. Thus, both margaric and oleic acids cqmbiiK 
with alkahes and earths, forming salts, which are cmd* 
manly denominated soaps. 

During these investigations, Chevreul observed, OM 
sometimes what he conceived to be msi^aric acid, nut* 
taining a less ratio of oxygen, was obtained, and that it 
manifested properties somewhat different. At length In 
ascertained that it is a different substance, and he glR 
it the name of stearic add. It is produced at the UHK 
time, in the same manner, and from the same Bubstuuv^ 
as margaric acid : they are both formed from steariiu. 
But margaric acid melts at 140°, while stearic acidn- 
qoirea 18 degrees higher. 

Chevreul next proceeded to investigate the Kstilts 
which the different other fatty substances, diseovoed 
by him, would present during saponification. Whefl 
butter was converted Jnlo soap, by combination with sn 
alkali, decomposed by means of an acid, and the reslJt. 
'ing matter put through various other processes, he atu 
BUied, in a separate iotTn,!io\Bss\5iatt three acids, cacl 
possessing diatinguiElring ^'^ope^'Qes'. 'ftie ftiW.'Xit f^A 
iutprici the second capi-oic ; Balftus'iiiiioaFrt*.'^ 



&BAP. III. ACIDS FROM ANIMAL SUBSTANCES. SOQ 

two last were so named because they are procurable from 
tihe butter of the goat as well as of the cow. Beside 
these acids^ others wer6 discovered^ which he denomi. 
tk&ted phocenic and hircic; being derived from phoce- 
nine and hircine. 

It appears from these researches^ that fats and oils do 
Qot^ in their natural state^ contain acids^ as ready formed 
constituent parts : but that^ when the fat or oil is formed 
into a soap^ by combination with ' an alkali or earthy a 
change is produced in the constitution oif the different 
fatty principles above-named^ which determines the form- 
ation of the acids. As soon as the acids are formed^ 
they unite with the alkali^ or earthy which had been in- 
strumental in generating them^ by decomposing the fatty 
matter: and the salts^ formed by the imion^ remain 
mixed^ or loosely combined^ and form soap. Thus^ hard 
or common soap is made by combining soda with oil ; 
and it is to be considered as consisting of margarate^ 
stearate^ and oleate of soda. Soft soap is made by com- 
bining potash with oil; and it is to be considered as com- 
posed of margarate^ stearate^ and oleate of potash. It 
is also to be understood^ that in the oil^ previously to 
combination^ there was not one of the three acids pre- 
sent; tiiey being die result of the chemical action of 
the alkali on die stearine and elaine^ of which oil is 
composed. 

It shoidd here be mentioned^ that when tallow^ or 
hog*s lard is distilled in a retort^ by a brisk heat^ an acid 
of a peculiar nature distils over^ along with some acetic 
add and water. It has obtained the name of sebacic 
add. It is crystallisable^ and enters into various com. 
binations; but is perfectiy different from those above 
described. 



X 3 



J Tbb BfRnity which acids manifeat for metallic ondci, 
I includin); alkalies and earths, has been expluned in n- 
' iJDUa parts of this volume. The resulting substance b 
oallcd ■ salt. The number of salts now linown to ] 
ehemists it immense, and such as precludes the po«a- 
bility of giving even the shortest description of them in 
M small >n elementary work as this. All that can h/Bt 
be (lone, is briefly to nodce the circumstances under 
which the acids combine with the alkalies, metallic ud 
non-metallic, the metallic oxides, and those fonnerij 
calleil earths. 

The generality of acida enter into combination with- 
out undenioing any change ; and form a salt in whhA 
the acid exists, just as it did while insulated, so fartt 
eomposidon is concerned. Others not only suf^ it- 
eomposition tiiemselves, when they combine, but effiet 
the decomposition of the base, if it be a metallic oxtibf 
■nd various substances result. Of the first clan •» 
the following ; and to form them, all that is required U 



be done, ia to samrate 


he respective acids with th 


oesHary base. 




Acids. 


Sails.. 


Nitric - - 1 


g 


"Nitrates. 


Carbonic 


s I 


Carbonates. 


Sulphuric . 


1-2 


Sulphates. 




■>.e 




Selenic - 


■ 1^ 


Seleniatea. 


Iodic - . . 


^■2 


lodalea. 


Phosphoric 


s| 






1 


Hydroxanthates. 


biiphonaphtlialic - 




\^%o.\v\iwna^lvthaI*t 



And all the vegewWie aciia. 



oij*p.j». ULn. Sll 

When the acid ends in the syllable iCj the salt formed 
'torn it is made to end in ali: When the aoid termi- 
''aiee in ouir, its siits are liistinguiahed hj the termin- 
ation iff. Thus, 

SuIphurouB -1 r Sulphites. 

3eleni0UB - - enters into com- J gglenites. 

Hypophoaphoroui fomn""' "" 1 Wypophosphiles. 

IXyposulphurouK |^ liypoEulphiteB. 

Soroetimea the insulated acid cnnnot be direetij aa- 
turated by a base, without occaaionirin deeompOBition of 
the add ; yet, by indirect meauE, itx salts may be pro- 
duced. Thus, if tve attempt to saturate hyponitrout 
und with a base, the acid ia reaohed into deutoxide of 
azote and nitric acid. By boiling 10 parts of nitrate of 
lead with 7'8 of metallic lead, we obtain a compound 
of hyponitrouB acid and lea<l, which, if mixed with a 
bisulphale of the base required, affords, by double de- 
eomposition, a hyponitrite of that base. Some acida do 
itot oombine with bases at all, bcin^ decomposed when 
presented to them, and no indirect means being known 
ot forming tbein ; althou^^h, in such cases, they do not 
ttecompose the base. This happens when bases are 
presented to nitrous and chlorioilic acids ; hence, w* 
have neither nitrites nor ehloriodates. The same ob- 
servation is apphcahle to Beveral other acids, but witb 
this additional circumstance, — that the bases, if metallic 
as well as tlie acids, are decomposed ; and that com- 
pounds are formed, in which neither the ori^nal acid 
nor base eKists. As the phenomena attending the pro- 
dncdon of such compounds are of }treat interest, it will 
be necessary to make some observationa on them more 
in detail. 

Until about twenty yuars since, muriatic acid wa* 
mppoaed to consist of an unknown base combined vvith 
iffygen ; and it was thought that it combines with 
bases simply by saturating them. 

When muriatic add is poured into wAnfitm o^ "jisAafti, 
^was i6ou;ii( that muriate of potash lestAXi'A-, «n&*ia.\. 



I 



n 



I 



I 
I 



when tlie solution was evaporated, and nystals famed, 
theEe were still miuriale of potash. I'he first positianil 
Btill admitted to be true by some chemists; but the; 
conceive that, in the act of cryBtaJliaing, the salt is Je- 
composed, — the hydrogen of the muriatic acid eombhBi^ 
with the oxygen of the potash to form water ; and 'ill 
liberated chlorine and potassium uniting to form chloriik 
of potassium, — this being the substance obtained b; 
cryataUisation, and not muriate of potash. Others ad 
that the resulting salt is a combination of chlorine and 
potassium ; but they imagine that it had the same MO. 
Ktitution while it was in solution, and that the decotn- 
poaidon of the muriattc acid and the potash took place 
at the moment of mixture. According to the flut ^ 
opinion stated, when chloride of potassium is diaadnd I 
in water, it is also decomposed, as well as some of 0k i 
water ; the hydrogen of the water and the chloriK 
form muriatic add, while the oxygen of Ae water iii 
the potasaium form potash, which combines wiA the 
murialjc acid. Thus, according to this view, &at 
could not exist a solution of chloride of potassium ; fin 
water converts that salt into muriate of polaah, tod 
muriate of potash could not exist in the solid slate, u 
crystallisation converts it into chloride of potasBium. 

What has been here said of chloride of calcium, is ap- 
plicable to all the combinations into which muriatic add 
and a metaUic oxide have been supposed to enter ; and 
it has been a question amongst chemists, whether or 
not any such class of salts as metallic muriates exlit 
It is universally allowed, that, when muriatic acid Ktn- 
rates ammonia, the resulting crystallised salt is a reil 
muriate, for ammonia neither contains a metal nor 
oxygen ; and, therefore, no such changea as those de- 
scribed above can take place. The same observatjon 
should extend to the combinations of muriatic acid wifli 
hst of alkalies, consisting of oxygen, hydnw», 
earboD, and azote, to which vegetable chemistry is every 
dty adding. There is i\o leastni to sov^irae OnttaT 



«' . .^^ 



other change takes place, is sucb cases^ than the mere 
formRtion of a muriate. 

Then- ere ottier acids, concerning the combinationB of 
which with metallic oxides, analogous dCuhts exist, 
because hydrogen constitutes an element in their com- 
position ; these are hydrocyanic, ferrocyanic, hydriodic, 
hydrobromic, sulphocyanic, and hydrofluoric. To all 
of lliem the same mode of reasoning applies: it is ac- 
cordingly supposed by some, that when they are pre- 
sented to a metallic base, decomposition of both the acid 
and oude takes place ; and that the result is water, with 
a cyanide, a ferrocyanide, an iodide, a bromide, a sulpho- 
cyanide, or a fluoride of the metal. According Co the other 
view, a simple union takes place, and we have hydro- 
cyanates, ferrocyanates, hydriodates, hydrobromatcB, 
Eulphocyanales, and hydrofiuates. In the case of am- 
monia and the vegetable alkaUes, nothing beyond simple 
union is supposed to take place. 

There is a fact relating to the salt resulting from the 
combination of hydrocyanic acid with potash, which 
deserves notice, as it apphes by analogy to all the otlier 
cases. If a plate of copper be immersed in its solution, 
poiassium is precipitated, which, reacting immediately 
on the water, evolves hydrogen by effervescence.* How 
is this to be explained, if the original salt was a hydio- 
cyanate of oxide of potassium ? Can it be supposed 
that copper could take oxygen from a substance which 
attracts it so powerfully as potassium ? — and what other 
allowable cause can be assigned for the appearance of 
hydrogen ? But if we suppose that the original salt 
was a cyanide of potassium, it is nothing surprising 
that potassium should abandon cyanogen for oxygen, 
when the change is aided by the affinity of nascent 
cyanogen for coppr. 

On the whole, it may be concluded that much doubt 

hangs over the nature and properties of the compounds 

Ikich have been just described. My opinion Is, that, 

o views which have been taken, vWt-jiVA&Wte** 

> JBomioD'iCJiEmiiti)', 1831, vol.li.p.Wl.rtsWi. 



I 



encambered with ihe supposition of complex decompo- 
dtions fliul rtcompoBitioni is that which lieniea llie 
exiBten(« of the hydrogen acid comhinations with hk- 
lalliv oxides, whether id the solution or in the toUd 
state, and coneiderB them as compounds of a metal wllh 
the hj'drogen acid radical. 

Some observationB remain to be made on the too- 
pounds of sulphur and hydrogen. It has been diown 
(page sot).) that theae elements combine in two propor- 
tions, and form aciils, called aulphuretted hydrogen, ud 
bisnlphuretted hydrt^en : their combinations with btan 
bare been called hydrogjitphiireU and kt/drofUTttUi 
lulphitrels. Ever since it was ascertained that an aBcaUw 
or earthy Bulphuret is a combinatian of sulphur with ftt 
metal of the alksli or earth, and not a compound of sul- 
phar with an oxide of that metal, as was once Bupposed, 
it was believed that when a sulphuret, suppose of polu- 
■iiun, containing more sulphur than what constjtutei I 
prolosulphuret, is dissolved in water, it is decomposed, 
md decomposes a portion of the water. The hydrogen of 
die water combines with the sulphur in two proportiou, 
forming the above-mentioned two acids, both of whicb 
combitw with potash, formed by union of oxygen from 
the water with the polassiura. Two salts result, which 
may also be formed by other means. The hydrosul- 
phuret may be formed by traiiMnitting Eulphnretted 
hydrogen through solution of potash; and the hydio- 
gnretted snljihuret may be produced by digesting ite 
former on sulphur, without heat, and filtering. From 
theae salts, acids separate the sulphuretted hydrogen by 
efiervescence, and the bi sulphuretted hydrogen by d^ 
position in the form of an oily tenacious liquid ; the 
potash combining with the acid added. 

When sulphate of potash, mixed with charcoal, ie 
heated to whiteness, both its elements give up their 
oxygen to form carbonic acid with the charcoal ; the 
potassium and sulphur then form protosulphurel of po- 
tassium. If dilute 6»i\p\iuT\c Bt\i\ie ^\h«A (mUiia, 
Kome water is decomposeA, l^e oi.'j?,eii. o^ 's'to'Sa -aro- 



SIS I 

'erts the potassium into potash ; and this, with the sul- 
■lillric acid, reproduces the original sulphate of potash : 
Wt the hydrogen of the decomposed water is suiBcient 
Q iaturate all the sulphur, and the resulting sulphuretted 
lydrogen efferresces ofFi there is, therefore, no other 
iKKhict. But had the original sulpliate of potash and 
harcoal heen exposed to a red instead of a while heat, 
rate polish would have escaped decomposition * hence, 
be potassium evolved would be insufficient to eliminate 
B much hydrogen from the water of the dilute 6ul- 
huric acid as would convert all the sulphur present 
ito Hulphuretted hydrogen, and hence some sulphui 
rould he precipitated. 

The same sulphuret of potassium may he generated 
J belting potassium in sulphuretted hyibogen ; the 
olphur forms sulphuret with the potassium, and hy- 
TOgen is disengaged. If the sulphuret of potassium 
e heated in more sulphuretted hydrogen, they combine 
rithout decomposition, and the result is a solid hydro- 
olphuret of sulphuret of potassium. Exactly the same 
olid is produced by heatini^ carbonate of potash in an 
xcees of sulphuretted hydrogen ; the latter expels the. 
aibonic acid, its hydrogen deoxidates the potash, and 
lie metal combines with the liberated sulphur : the 
ulphuret of potassium thus formed combines with sui- 
hurelted hydrogen aa before. 

When this salt is thrown into water, we are at a lost 
o know what happens. It may merely dissolve; or 
ome water may be decomposed ; its oxygen, with the 
lotassium, forming potash ; its hydrogen, with the sul- 
ihui of the potassium, forming a quantity of sulphur- 
tted hydrogen, additional to what was originally present. 
rhe sulphuretted hydrogen, now doubled, may combine 
rith the potash, forming a solution of bihydrosulpburet 
rf potash, which, in crystallising, may undergo decom- 
lORition : the hydrogen and oxygen, originally furnished 
•J the decomposed water, uniting and recompoaing 
rater; while the sulphur and potasBTOin, vivVV ■»i\at\i. 
tese elemenM bad been combined, tecompose ' 



I 
I 



I 



r OHKMIBTRT. 

of potassium, this re-uniting with the original Kulphu^ 
etted hydrogen. 

The bihydroBulphuret of potash above mentdonedH 
the salt commonly called hydroEulphuret of potush, ini 
prepared by pasBing a stream of sulphuretted hydropn 
through solutioTi of potash. This last method of pre- 
paring it might be explained in two ways, coDformiblf 
to the forgoing two views. Either the gas is tneidj 
absorbed, or the potaah and half the gas are decomposed 
at the instant of meeting ; the hydrogen, hy taUng 
oxygen from the potaesium, producing potash, and leif- 
ing its sulphur to combine with the potassium, and fbm 
sulphuret of potassium, which then unites with the n- 
maining undecomposed half of the sulphuretted hydro- 
gen, leaving hydrosulphurct of sulphuretted potatam 
ia solution. 

Although the explanadons here given have been em> 
fined to sulphuretted hydrogen and potash, they applj 
equally to any other metallic base. When ammonia or 
a vegetable allcaii is the base, we must suppose Aat lliii 
acid gas merely combines, without ni&ring oi occauoB- 
ing decomposition. 



317 



PART m. 



PHENOMENA PRESENTED DURING SOME REMARKABLE 

CHEMICAL CHANGES. 



CHAP. I. 

OF SOME PROCESSES CONNECTED WITH ANIMAL LIFE. 

Although it is not my intention to enter into explan- 
ations of vital functions in general^ there are two animal 
processes so intimately connected with^ if not dependent 
upon^ chemical changes^ that they appear to fall within 
the province of the chemist almost exclusively. There 
are others which seem to have been so little illuminated 
by the lights of chemistry^ that they might just as well 
be surrendered altogether to the physiologist. The sub- 
jects of respiration and animal heat shall occupy the 
two succeeding sections. 

Section I. 

EESPIRATION. 

The blood is distributed by the arteries to all parts 
of the body, and is returned by numerous veins, which, 
by frequent junctions, become larger, and at length ter- 
minate in two trunks, called the vena cava superior, and 
vena cava inferior: these, meeting at the heart, discharge 
into the right auricle, from which the blood is propelled 
into the right ventricle, and hence into the pulmonary 
artery, which ramifies in a vast number of minute 
branches through the air cells of the lungs. After being 
exposed in these delicate vessels almost to the direct 
action of the air inspired into the lutiga, \Jafe\}tfiQ^ *v^ 
returned by the pulmonary veina to t\ie\eix. ^wcvO^^, «sA 



I 



bence to the WFt voitridt, fiom wlikji it is diqiened 
through the lOTta to all parts of the body. It u wink 
panhig diraog^ die minaie and DiBDeroiu nmificafim 
t^ tike puiinoTiary vterj and polmaittn reiOE, and dioT 
f ffiH^rj jonctiaii^ thai die hlaod loaes He duk ahadt, 
inwtmri the floiid red htie which il ii fouoil to poiMi 
in the arteriea, and acquires its nntridonB qoaliliea 
Daring the circulatioo, it loses its vcmilion caimiT asll 
itc nutritioiiB qualitiei, bj snppljiiig the waste of mi- 
lerials throoghout the whole bodv ; and when it hM 
retomed into the veins, it has once more become diA 
carfoored. Tile change of venoos into artoial Uood il 
the essential phenomenon constituting te^iixlioa; ilii ' 
bj this chan^ that the blood is qnalified to snpport Sfb 

What the nature of this change may be, is a satiJMI 
involving much difficulty and nncertaiuty. The piocesi 
by which it it e^cted must be of great consequence to 
the animal : for one of the chief usee of that coniplei 
apparatus, constituting the organs of drculation, is to 
expoae the mass of the blood, amounting, as some af. 
firm, to S3 pounds, extended to a vast surface in tbe 
capiQariee of the lungs, to the action of the atmo. 
sphere, about 23 times every hour; for such 1 is ifw 
calctdated velocity of the circulation. The followit^ is 
an abstract of the difitrent theories which have been 
advanced to explain the nature and uses of the process 
of respiration. 

Lavoisier conceived that the oxygen of tbe air drawn 
into the lungs during inspiration, meeting hydrogen and 
carbon, which exist in tbe blooii, combines with both, 
either in the lun);s or clurin}; the circulation ; carbonic 
Bcid and water result, and these are expired. He con~ 
oeiveil that the azote neither acts nor is acted upon- 

Crawford taufjht that the bloori receives what be called 
hydrocarbon in the capillaries ; anil that it is the pre- 
sence of this in venous blood, which constitutes the dif- 
ference between it and arWiial Wood. Tbe oxygen of 
tile air inspired, combinea vii'ftv the^i'^AiQca.'r^'a'vii.fei 
lungs, and forma carbotuc ac\a ani ■wa.xerj vB.-^wn. \^ 



consequence of this abstraction of hydrocarbon, the ] 
venouH blood is reconverted into arterial. It h not easy 
to perceive any real difference fjetween this, and the 
theory of Lavoisier. 

1 have not had an opportunity of seeing the original 
of M. Lagrange's theory ; what follows. Is the account 
given of it by Hassenfratz. The hlood, in passing through 
the lungs, dissolves oxygen abstracted from Che air in- 
spired: the blood, holding this oxygen, is transmitted 
through the arteries, and thence to the veins ; daring i 
its passage, the oxygen, by little and little, forsakes its J 
state of dissolution, and partially combines with tbel 
carbon and hydrogen of the blood, forming n 
carbonic acid ; the latter of which is disengagec 
as the venous blood leaves the heart to enter the tungg. 

Hasaenfratz has supplied some parts of the detail of 
this theory, and has supported them by experiment. It 
was ascertained by Priestley and others, that venoiB 1 
blood, by exposure to oxygen, is rendered bright n 
that, by remaining for some time thus exposed, 
duaUy loses its florid hue, even although tbey are shaken 1 
together ; and that blood, exposed to any gas not con- 
taining oxygen, is rendered dark. Hassenii^ta explains 
these facts, by supposing that the bright red colour of 
arterial blood is occasioned by its holding oxygen in 
solution ; and that when the oxygen abandons the blood, 
in order to combine with the carbon and hydrogen pre^ 
sent, the blood loses its bright red colour, and becomeB 
dark : it is then venous blood. Corresponding with this 
explanation, he ascertained that chlorine (which indi- 
rectly supplies oxygen), mixed with venous blood, im- 
mediately renders it very dark coloured ; a phenomenon, 
in his opinion, attributable to the facility with which 
chlorine supplies oxygen in a state ready for immediate 
combination with carbon and byilrogen, while the oxygen 
of the atmosphere, being gaseous, combines with dtflS- 
culty. Chlorine does in an instant, what common air can 
only do by lanp; continued contact. 

These theories difler very little Iiom e^ch o'&Et- Vn 



;t 

renotB^^H 
t redj^H 

itgra^-^H 
thaken ^H 



I 



aU of them the error is comnutted, of suppoung dal 
vater is generated in the lungs ■ whereas it is merely 
exh^ed from the mucous membrane which linei tbe 
mouth and pharynx. That no union lakes place betmct 
the oxygen of the air and hydrogen existing in the Uwd, 
is proved by tlie fact, tliat although tnoisnire is it- 
ways found in the breath, the quantity of oxygen whidi 
disappeara is, at times, almost exactly equal to the ai- 
bonic acid by which it is replaced ; and ne must sap- 
pose that the origin of the moisture is altrays the same. 
It is not expl^ned, in any of these theories, what the 
Qrigin of the carbon is, that is supposed by them to be 
constantly renewed in the blood : this deficiency hu 
been supplied by Drs. Thomson and Murray, in th^ 
respective systems of chemistry. Dr. Thomson uyi, 
" It appears, from the most accurate observations hi. 
riierto made, that neither chyle nor lymph contiili 
fibrin*, which forms a very conspicuous part of the blood: 
diis fibrin is employed to supply the waste of the nnu- 
des, the most active parts of the hody ; and, therefoR 
in all probability, requiring the most frequent supj^yi 
Nor can it be doubted that It is employed for other 
nseful purposes. The quantity of fibrin in the blood, 
fiien, must be constantly diminishing ; and, therefote, 
new fibrin must be constantly formed. But the only 
substances out of wlilch it can be formed, ate ihe cliytt 
and lymph, neither of which contain it: there most, 
therefore, be a continual decomposition of the chyle and 
lymph going on in the blood vessels, and a continuil 
Dew formation of fibrin. In what manner the chyle, oi 
a part of it, is converted into fibrin, it is impossible la 
lay; but we can see at least that carbon must be sb- 
ttoacted from that part of the chyle which is to be con- 
verted into fibrin. Hence, as the process of blood' 
making advances, there must be a greater and greater 
redundancy of carbon in the Uquid ; we may conclude, 
therefore, that one great use of reapiraUon is to abstract 
■boa, by forming wi\^ il. eai^njois. iKvi." 



CHAP. I. RESPIRATION. 321 

Dr. Murray gives the following account : — ^^ The 
blood is the source whence the animal products are 
formed : this expenditure is supplied hy the chyle^ — a 
fluid less completely animalised than the hlood. The 
peculiar character of animal matter^ with regard to com- 
position^ is a large proportion of nitrogen^ and a dimin- 
ished proportion of carhon: it may he, therefore, inferred, 
that in the extreme vessels, where the animal fluids and 
solids are formed, the general process will he the separ- 
ation from the hlood of those elements of which animal 
matter is composed ; and that, therefore, carhon, which 
enters more sparingly into its composition, will exist in 
the remaining hlood in an increased proportion. This 
is, accordingly, the general nature of the conversion of 
arterial into venous hlood. Nitrogen, hydrogen, and other 
elements, are spent in the formation of new products ; 
and the proximate principles of the hlood remain, with 
an increased proportion of carhon. • In this state it is 
sxposed to the atmospheric air in the lungs — the oxygen 
of which abstracts its excess of carhon, and forms the 
carbonic acid expired ; and this constitutes the conver- 
sion of venous into arterial blood." 

The foundation of Thomson's explanation is the po- 
sition, that carbon must he abstracted from that part of 
the chyle which is to be converted into fibrin. Unfor- 
tunately, we do not possess comparative ultimate analyses 
o£ chyle and fibrin ; and hence the proof of the above 
position rests on the fact, that carbon is taken up by 
9xygen in the lungs, which is the phenomenon to be 
explained. It is possible that chyle may sometimes con- 
tain a greater ratio of carbon than fibrin does. Dr. Mar- 
ket showed that the chyle of dogs fed upon vegetable 
iiet, afforded three times more carbon than that of dogs 
■ed on animal food : but a theory of the origin of carbon 
n expired air must account for its appearance under all 
nrcumstances of diet. Mxuray's explanation depends on 
the truth of the position, that " the peculiar character 
)f animai matter is a large proportion oi mtTO^eti, wv\ 
dimimabed proportion of carbon." HexvcfeVve oomv^x^* 

Y 



KLSVEKTH a 





I that, US " oU animalB live, ilireirtly or indirectly, e 
regetable matter," ihc chyle will be a " fluid less com- 
plelely animaliBed than blood ;" which n 
it will partake mare of the cegetable 
which it is ultimalelj derived. It does not appear a 
me, that the indirect origin of food of animak [□ tep. 
table matter has any connection with the subject ; fa: 
a vegetable becoming animalised, cannot aSect thedijle 
produced by assimilation of such animalised I 
But that one of the peculiar characters of animal 
ia its containing a diminished ratio of carbon, ii 
■ition which not only has never been established by 
experiment, but seems contiadicleil by moEt of the fuB 
with which we are acquainted. We do not know the 
relative quantities of fibrin, gelatine, and albumen, which 
chiefly constitute muscle ; but it is of less consequence, 
as tile ratio of carbon in each of these tliree proximate 
principles is not very different. Were mascle ci 
of equal parts of these proximate principles, the 
ratio of carbon would he about 51'4 per cent, 
precisely the quantity of carbon in beecU-wood. WheU 
flour does not contain, at most, above i5 per cent 
earbon ; potatoes contain but 37'4> per cent, : and, g 
nerally, vegetable proximate principles contain less ihi 
50 per cent, of carbon, and many of them much undei 
this ratio. These considerations render Dr. Murray'a 
position very questionable. 

It appears to me, that, notwithstanding the induilry 
with which the subject has been prosecuted by n 
chemists and physiolo;;;iats, the theory of respitalian 
stands pretty much in the same way as it was left bj lis 
modification of Lavoisier's explanation, given fay La- 
grange : it may, therefore, be expedient to expadate on 
it a little more fully. 

That oxygen exerts an agency on blood, is a fact that 
leems proved beyond question. The experiments of 
li'onlana and Luzuriaf^a show, that blood, whether u- 
terial or venous, wticn B\i.tt\i.en iti coWac\. in"vCn. cnvnmon 
lix, or, better, with os-^geti, i.iQ-\itttXs ca-fwia, ikd^ wsi- 



<OHAP. I. RESPIRATION. 323 

verts the oxygen into carbonic acid : it is, therefore, a 
fair presumption, that, in the body, the change of in- 
spired oxygen into carbonic acid is «fiected in the same 
manner. In the air cells of the Imigs, the oxygen may 
be considered as almost in contact with the blood con- 
tained in the ramifications of the pulmonary artery, and 
of the pulmonary veins in which they terminate ; inas- 
much as nothing but the exceedingly thin substance of 
tibe vessels is interposed. It was shown by Priestley, 
that venous blood, tied up in the thicker substance of a 
moist bladder, became red when exposed to air, as soon 
and as much as if in direct contact with the air. When 
the oxygen of the air is taken into the lungs, after a 
momentary contact, as it may be called, with the blood, 
it is discharged again during expiration ; but part of it 
has combined with carbon. Concerning this combination, 
tiiere have been, as was already stated, two opinions. 
One is, that the oxygen of the air instantly dissolves and 
combines with carbonaceous matter found in the blood, 
and immediately after is expired as carbonic acid : the 
other is, that the oxygen of the air is absorbed by the 
blood in the hmgs; that it circulates with the blood 
throughout the whole system, during which it combines 
with carbon ; and that, on the return of the sanguineous 
current to the lungs, the carbonic acid thus produced 
exudes through the coats of the minute vessels, and is 
exjMred. I consider the latter of these opinions the more 
probable, on several accounts. Fontana exposed blood 
to common air, during so long a space as three minutes, 
without producing any change; but when he agitated 
tiiem together during the same time, carbonic acid ap- 
peared. Independently of the evidence afforded by this 
experiment, it might reasonably be expected that the 
carbon of the blood would require more than an instan- 
taneous contact with the oxygen of the air, before a 
combination could take place. Such a condition would 
be fulfifled, if the oxygen were to circulate with tl\e ^Iqq^ 
for two minutea and a half; for this,^^ i«i a&S&Vwywxv, 
w the space of time which the wliole voVwme oi \3ftfc\Svw>^ 

Y 2 



i'«S4 



vtatatA 



I 



I 



requires to navel from the lungs back agun to the 
lungs; and. this was nearly the space of time during 
which Fontana found it necessary to continue the tg.- 
tation. If, in Fontann'e experiment, actual contact of 
the blood with oxygeo during three minutes diii tiK 
evolve any carbonic ueid, it would be singujju: if , in the 
longs, carbonic acid coidd be formed during the dn)c 
occupied by one inspiration, notwithstanding that the 
BubBtance of the blood vessels and air tubes ia iDlet- 
posed. Tbese considerationa correspond exactly with tht 
&ct stated by several respectable authorities, that car- 
bonic acid exists in recently drawn blood ; and that it 
may be separated from the blood, by placing it under an 
exhausted receiver. The statement has, certainly, been 
called in question ; but it appears that the authorities by 
which it is supported, are of equal conaidcratian witb 
thoae opposed to it: and tliere is this addidonal argu- 
ment in favour of it, — that it harmotiisea with all ibe 
fact* known. 

It appears to me, that to confine the office of air in- 
spired to the mere rotnoval of redundant carbon from 
venous blood, is to take a limited view of its operation; 
and to under-rate the utiUty and necessity of the coin- 
plex and astonishing mechanism by which so simple an 
object would be accomplished. To the process of re- 
spiration, the construction of the chief parts of the aniinil 
system are subservient ; if respiration be suspended, so 
is life : even the atmosphere is constituted in such a way 
as to conduce to the due performance of this functian. 
We know the important and extensive agency of oxygen 
in creation : can we doubt that, in the laboratory of llie 
body, where chemical changes are incessantly taldog 
place, oxygen is in all parts constantly in demand ? and 
is it not probable, that the medium of supply of oxygen 
to all these parts is that obvious one, which, in order to 
receive the supply, is presented, in hundreds of currents, 
to hundreds of cuxtei\tB oC air, the absorption bdng 

promoted by the two mosler 

and extensive aurfacc'J 



tHAP. I. RESPIRATION. 3S5 

It would contribute towards a decision of this 
^uestion^ were it ascertained that the air taken into 
die lungs loses at all times exactly the same volume of 
oxygen as is returned in the state of carbonic acidi 
A volume of oxygen suffers no change in being con- 
verted into carbonic acid. If this conversion took place 
equally in the lungs without any change of volume^ it 
might then be presumed that the oxygen inspired had 
done nothing else than remove carbon.* Hitherto there 
has not been such a correspondence between the results 
of the experiments made on this part of the subject, as 
to warrant almost any conclusion that ought to influence 
our judgment on so difficult and important a question. 
The inference which seems best supported by the state- 
ments of different experiments, is, that sometimes the 
oxygen of the air inspired almost exactly agrees with 
the carbonic acid expired ; this happens in the human 
8(>ecies, and some other animals. Sometimes there is a 
greater volume of oxygen consumed than is accounted 
for by the carbonic acid ; and in certain animals the 
difference is often considerable. It seems that, so far 
as the function of respiration is concerned, it matters 
little what animal, within certain limits, is made the 
subject of observation ; we must suppose that, in the 
higher orders of animated beings, the use and nature of 
the function is mainly the same. 

It has been found that the azote of the air inspired 
is sometimes returned in full volume, and sometimes is 
partially retained, and disappears ; the quantity of it is 
very variable. It has been even ascertained that the 
quantity of azote expired sometimes exceeds the quan- 
tity which had been contained in the common air taken 
into the lungs ; and it has been affirmed that this hap- 
pens in summer, while in winter 4ess azote is returned 
than is received by the lungs. This evolution of su- 
perfluous azote, no longer necessary in the animal 
economy, has been strikingly proved to take place, by 
including a guinea-pig in pure ox'^^eWj wv^. ^xva'^'ex \a. 

* Its inSaence in producing aiumaV Y\eat \» tot \,\\e vt**^^^'^^^^^^' 

Y 3 



{ 






ml hydrogen — the rutio bring 
; in both cases, axoU was Anuui 
remaining gas. A pigeon confined in a sinultr 
■j^en and hydrog^i also evolved axoK. 
During the respiration of both of these animala in 
the mixed gas, it was found that some hydrogen was 
taken into the lungs, which totally disappeared. The 
singular fact has been ascertained, — and it is one 
which may yet he turned lo good account by the jAj. 
sician, — that breathing a mixture of oxygen and by. 
drogen produces a tendency to sleep. 

It has been found that, in the human ^>ecies, diSu^t 
individuals consume difierent quantities of oxygen, and 
surse return different quantities of carbonic acid. 
breath expired has been shown to contain fiDm 
1 8 per cent, of carbonic acid. Drs. Frout and 
Fyfe have proved experimentally, that peculiar con^ 
of mind or ho<)y render the quantity of carbonic 
acid variable. The former has shown that the quandly 
depends also on the time of the day ; at noon it is st 
the maximum ; it decreases until nine at night ; it then 
remains at the minimum for six hours ; and at four in 
the morning it begins to increase. These were the re- 
Rolts obtained in the month of August. 

The lungs are not the only egress for carbon in the 
human body. If a person's arm be enclosed in a bell 
glass full of common air, and the communication with 
the external air be cut off by tying a moistened bladder 
round the mouth of the bell glass to the arm, the 
oxygen of the air will in part disappear, and be rephKcd 
by carbonic acid ; but it is not known how this change 
ia effected. 

The foregoing stati^ments seem to bear out the con. 
elusion just now ar»ved at, that we are really ignonnt 
of the uses of respiration in the animal economy, and 
that the mere removal of carbon cannot be the duty of 
the air which enters the lungs. IJoth oxygen and BMte 
ire proved to he frequenft'j a\iBDT\ie4 •, Koi, ^ox ta^ 
thing we know to llie contiaijj Oaeae oetaavomis^v^^iua 



^fiilF. I. ANIMAL HEAT. 327 

of two active gases may be just as necessary under cer. 
tain conditions of the animal^ as the formation of car- 
bonic acid in the circulation (if it be there that its 
elaboration takes place)^ and the eventual elimination of 
carbon from the body. When additional oxygen and 
azote are not necessary in the body^ then^ probably, the 
inspired air is returned in full volume ; having merely 
experienced a partial conversion of its oxygen into car- 
bonic acid. 



Section II. 

MAINTENANCE OF THE TEMPERATURE OF ANIMALS. 

The changes produced during respiration have been 
^wajs supposed to be intimately connected with the 
iBiiiitefii»ioe of thitcltwiicid temperature^ which distin- 
guishes the existence of certam orden of Mwmated 
beings ; and much difficulty has been experienced in 
forming a theory of animal heat which will correspond 
with the facts^ but hitherto without success. 

Black's doctrine of latent heat afforded an explan- 
ation of the origin of animal heat. During respiration^ 
the oxygen of the air inspired combines with carbon, 
and, as it was at first supposed, with hydrogen ; both of 
these substances, in combining with oxygen, evolve some 
of the heat which was latent in the composition of the 
oxygen and hydrogen ; and this heat is circulated by 
the blood to aJl parts of the body. 

But it was soon perceived that, as this combination 
took place in the lungs, and the heat was evolved there, 
the lungs should not only be the hottest part of the 
body, but the heat would be capable of injuring these 
organs. In order to remove this difficulty, different 
explanations were offered, of which the chief are the 
theories of Crawford and Lagrange. 

Crawford made experiments to prove that the specific 
heat o£ arterial blood is greater t\iaiv \\\aX oi nc^wv^. 
Hencej arterial blood, at the tempeiataie oi XJcva \xvsv^, 

Y 4 



I 



would cotitAin more' heat than venous blood at the aaiw 
temperature ; and arterial blood, in changing lovetioui, 
woiUd part witli its excess of hettt, and jet remnin al 
the same temperature as before. If oxygen, in cora- 
bining with carbon and hydrof^n contained in the 
blood, caused the evoludan of so much heat, thu eto- 
lution would take place in the blood itself at the loDgB. 
But at the same instanC the blood becomes arteiiil; 
that iSj in effect, suffers an increase of its capacity for 
heat, absorbs a quantity of heat which does not ndae 
its temperature, and thus removes the portion of belt 
that might have done injury to the lungs. In this 
way the blood and heat are carried to the capillaries ; 
where the formerj liy continually changing into venous 
blood of less capacity, part£ with its heat gradually. 
and maintains the animal temperature equably. 

Lagrange removed the difficulty, and arrived at the 
same ol^ject, by supposing tha^ the heat is not disen- 
gaged exclusively in the lungs, but in all parts where 
the blood circulates. This follows irom his theory of 
respiration alreaiiy described. According to him, the 
oxygen of the air is dissolved by the blood at the lungs, 
and circulates, thus dissolved, in the arterial blood ; it 
is only when the blood is changing gradually and 
alowly in the great circuit of the capillaries, that the 
combination of oxygen with earl>on and liydrogen takes 
place, and that the heat is developed. 

Dr. Girtanner, of Gdttingen, gave a modified view of 
this theory, which, being rendered uselesaly complei:, 
need not here be described. 

Dr. John Davy, in repeating Crawford's experiments 
on the difference of specific heats of arterial and venom 
blood, obtained different results. According lo ihe 
former, the difference is inconsiderable, and inadequate 
to sustain the olgect for which the experiments were 
instituted. It is of no consequence whether we decide 
jn favour of the accuracy of Davy or Crawford ; inai- 
much as the theory o? Ija^avi^e e^s.'^wia ■&« es^s*!. 
liaatiott of animal heat m & sa.l.Ma^Wt'i '«a.-S "> «es™.M» 



CHAP. I. ANIMAL HEAT. SQQ 

harmonise best with recently discovered facts ; and thus 
renders the theory of Crawford^ ingenious and beautiful 
as it is^ useless. 

The grand question was^ what is the source of animal 
heat ? Black supposed that the oxygen of the air 
inspired parts with some of its latent heat. Crawford 
conceived that the difference between the specific heat 
of oxygen and carbonic acid is the portion which is 
liberated during respiration^ and. maintains the animal 
temperature. But Delaroche and Berard infer^ from 
their experiments, that this difference is trivial : they 
represent the specific heat of oxygen to be 0*8848, and 
that of carbonic acid 0*828 ; air being unity, and the 
comparision being made on equal weights of the gases. 
Hence it has been supposed, that so small a difference 
cannot be the source of the large quantity of heat pre- 
sent in the body. But it is between the specific heats 
of equal volumes that a comparison should be instituted. 
We then have 0*97^5 as the specific heat of oxygen, 
and 1*2583 for that of carbonic acid: the difference is 
much greater than in the former case ; but still the 
question arises, is it sufficient to account for the tem- 
perature of the body ? 

In answer to this question, it was maintained, on 
the authority of experiments by Crawford, Lavoisier, 
and La Place, that an animal consuming oxygen, and 
returning it as carbonic acid, evolves pretty nearly as 
much heat as that same quantity of oxygen would 
evolve, had it been converted into carbonic acid by the 
combustion of carbon in it. Chemists, however, seem to 
place no reliance on the measures of heat employed in 
these and similar experiments ; and even the opposite 
of the inferences drawn from them have been main, 
tained to be true. 

It appears to me, that a very useful estimate may be 
formed in this inquiry, by reference to common ex- 
perience, without the aid of any instrument or refined 
expenment It is believed that a inati ^ewet^Xfe^ ^wi^. 
40,000 cubic inches of carbonic acid in ^^\kavnL^ \ "^^ 






contains about llj aToirdupoiB ounces (11-59) of " 
bon. Suppose that tliiB quantil)' of charcosl were 
burnt in common air ; that the whole of the h 
evolved were applied, without loss, to sustain the U 
perature of the human bod; at fjB" ; and that die body 
nmsists of )€ stone weight of solids, soft solids 
liijuids ; a considerable portion of heat is to b 
atfaeted by tile surrounding medium, and much t 

be vaporised in the breath, and i 
perspiration. The quantity of vapour of water pre- 
~ iced at the surface, supposing its average temperatui 
and ftuni the mouth, would amount to no less Ham 
S26 cubic inches in ^i hours, at some times ; taut 
-would seldom be less than 70,000. Beside this, the 
expired air leaves the mouth at Q0°, and a million 
cubic inches of air so heated leave (be mowth evBf 
24 hours. Would the combustion of 11^ ounces of 
charcoal afford such a supply of heat for ^i houn 
(that is, 311 grains per hour) as would accomplish all 
theae objects p 

Mr. Brodie, led by considerBtiims of a (liferent liind, 
has denieil that there is any production of animal heat, 
in consequence of the conversion of oxygen into car- 
bonic acid in the lungs. Having procureil two rabbitf 
of the same size and colour, he killed both by dividing 
the spinal marrow. Having removed the head of one, 
and secured the vessels of the neck by ligatures, he pro- 
duced artificial respiration by meiins of a small bellows 
fitted to the trachea. The heart now contracted at the 
L-Xftte of 1 44 times in a minute ; but in 1 00 minutes tile 
Lnumber was reduced to 90 per minute. A thermome- 
r ter had been introduced into the rectum of each rabbit, 
Biid at the beginning of the experiment both stooil at 
100Jl°. Both thermometers began to sink; but tiut 
in the rectum of the rabbit in which artificial respira- 
tion was kept up was always 2 or 3 degrees lower thao 
the other. In 100 miuutcB, the former stood at goi", 
the latter it ii3° . Tbe iViffeience ft«wx(^Qo.'L -was mkA- 
buced to the large q^uantttj ot co\i sii ■wVve'o. cs««,\K&'ii 



HAP. I. ANIMAL HEAT. SSI 

ooled the blood circulatiiig through the lungs of one^ 
nd not of the other : and it was shown in another 
xperiment, that when the circulation is prevented by 

ligature^ the artificial respiratory process being con- 
inued^ the cooling agency of the air was scarcely dis- 
overable, because it now was confined to the air cells of 
tie lungs^ and could not affect remote parts. 

Other experiments showed that, in rabbits killed by 
Olsons, which act by disturbing the functions of the 
rain, the circulation may be contained by carrying on 
n artificial respiration ; the same quantity of carbonic 
ci4 was expelled as during life ; and the same change 
f sensible qualities of the blood took place in the two 
apillary systems, as would occur in the living animal, 
fet in consequence of the cold air thrown into the 
ings, the animal cooled more rapidly than another in 
^hich no artificial respiratory process was kept up. 
Ir. Brodie, therefore, argues, that if the conversion of 
xygen into carbonic acid in the lungs were the cause 
f animal heat, the dead bodies of these rabbits should 
ave maintained their temperature. He concludes that 
nimal heat depends on some function of the brain. 

These experiments are, however, liable to some ex- 
eptions. Although artificial respiration did not keep 
p the animal temperature, it might have generated 
ome heat, which was afterwards carried o£F in various 
^ays. First, the. cold air thrown into the lungs, acting 
n the whole circulation, must have withdrawn heat in 
wo ways ; and the experiment of obstructing the cir- 
ulation by a UgatUre, as is admitted by Mr. Brodie, 
id not prove that heat was not withdrawn. Secondly, 
.0 allowance was made for loss of heat by the vaporis- 
tion of water exhaled by the mucous membrane. And, 
birdly, there was no allowance for loss of heat by 
utaneous perspiration, which takes place, often largely, 
t the moment of death, and no doubt continues while 
lie circulation is forced to continue. At least, it was 
ot proved that these three sources oi i?iXi"a.c^ ^^ ^'^'^ 
Jit. It must he observed also, that. t)aft«fc cyl^tvtsns^^s* 



I 



I 



t been attended with die same results in die 
hands of other persons ; for it has been affinned that 
the cooling process is rendered slower by arUficial k- 
spiration. This, however, is of little cotleeijuence. Mr. 
Brodie's experimenta prove very clearly, that animil 
heat is not maintained by respiration ; but they do not 
prove that no heat is generated during that process- 
Indeed, it can scarcely be denied, that the conTereion 
of oxygen into carbonic acid in the lunge, is a sanive 
of Bome heat, as well as it would be oat of the lui^. 
In the process of arterialisation, the blood, is pto»eil to 
become warmer. Majendie estimatea, I know not if 
on the authority of his own experiments, the diSerentt 
between arterial and venous blood so high as S° ; 
although this difference is not great, it U quite gImt 
that it does not repreeent the total heat devdoped 
during respiration. 

It might, perhaps, be considered probable, ^at the 
conversion of hquid chyle into solids, to supply the wute ' 
of the body, might, during the change &om flnjdjty IS 
Bolidity, evolve the remaining quantity of animal heat 
But, beside some difficulties that would attend this mode 
of explanation, we are prevented from ailopting it by 
knowled);e of the fact, that durin;; some diseases there 
is no such conversion, for no aliments are taken inlo 
the stomach ; and instead of any accession to the solide, 
there is a constant wasting of them : yet tlie heat of the 
body is higher than ever. 

Perhaps the opinion on the subject of animal lieat, in 
entertaining which we shall be least liable to error, is, 
that the elevated temperature of warm-blooded aninata 
does not derive its origin from any one source, but fiom 
severa!, and that at present we know of but one. We 
may also suppose that chemical changes are coastandy 
taking place in the body, through the means of whicb 
heat is extricated. But we are not enable<l to astign 
any thing more precise as to the nature of these changes, 
without entering into UBe\eift oi iansptoMaV-j-^'iKKs. 



chAf. u. fermentation. 333 



CHAP. II. 

OF THE SPONTANEOUS DECOMPOSITION OF VEGETABLE 

AND ANIMAL MATTER. 

By the word fermentation*, modern chemists under- 
stand the spontaneous decomposition which animal or 
vegetable matter undergoes when placed under proper 
circumstances; the most remarkable result of which is, 
either alcohol, acetic acid,, or a putrid smell. The pro- 
duction of these different results gives origin to three 
distinct stages of the process, each characterised by 
different phenomena. All fermentable substances, how- 
ever, do not proceed through each of these changes, 
even when the circumstances are favourable ; but 
there are some good instances in which the stages are 
distinct and consecutive. If grape juice be exposed 
to a moderate temperature, it soon begins to effer- 
vesce, and loses its transparency ; a viscid scum rises 
to the surface ; the taste changes from sweet to «i- 
naus; and, under proper management, the Hquor is con- 
verted into wine. Solution of sugar and all sweet Uquids 
are capable of undergoing similar changes, and of being 
converted into a kind of wines. The process by which 
these changes are effected, is, on account of the nature 
of the product, called the virwus fermentation , and the 
result of it is the formation of alcohol. 

If the hquor which has undergone the vinous fer- 
mentation be exposed to the temperature of about 75®, 
it from being transparent again appears somewhat mud- 
dy ; the taste changes to sour, for the alcohol is now 
changed into vinegar; and from acetum, the Latin for 
vinegar, this stage is called the acetous fermentation. 

Vinegar, when long kept, loses its acidity and its 
transparency : it exhales a putrid smell ; and has now 
undergone its last stage, or the putrefactive fermentation, 

* A much fuller iiccou»t of the process of fetmetrtalVim.N^VJWjft tovxsA'va. 
the Cabinet Cyclopadia, Vol I. of Domestic EconomY. 



I 
I 



Wbeo wbMien floor is nude into dough idlh mtn 
and a lin!e jeatt, it undeT^oes the vinous fermenlatioii; 
carbonic acid is eTolved, which pafis ap the dougti in 
alight sponge; and alcohol in small quantity is evohei 
A patent has been taken oat for an oven, which, in Ink- 
ing the bread, coitdenses the alcohol. I euBmined some 
of the alcohol thus produced, and found both it. and tfae 
bread which afibrded it, to be, as I conceived, of eud- 
lent quality. 

There are several candilions necessary to the jiroduc- 
tion of fermentation : water must be present iu aU cases; 
there must be a temperature above SS" at the lowest; 
a fermentable substance, and a ferment, are also necesMrfi 

Vinmui fermeRtation. — lu oriler to produce the vinoM 
fenneotittion, the only fermentable substance known i« 
■npr, in some one or other of its modifications. A whtiwt 
of common sugar, starch sugar, fruit sugars, a 
in the dii&reut fruits, or the Eacchariite matter of malted 
grain of any kind, will answer the purpose perfectly. 
In same cases, sugar does not exist ready formed, ^- 
tbough the vinous fermentation may be excited : but in 
all such cases, the elements of sugar are present; md 
during some stage in the process, sugar is proiluced froin 
them. It was discovered by Kirchoff, that if potato 
starch, and gluten from grain, he mixed with hot wawr, 
and allowed to act on each other, the mixture, at lint 
not in the least sweet, eventually becomes so, because 
the starch is converted into sugar. This explains the 
fact, that in the process of the distiller a mixlnre of malt 
and raw corn, when mashed with warm water, and fer- 
mented, affords even more alcohol than would have beM 
obtained had the raw com been malted. In the raw 
com there was both starch and gluten. 

It is here necessary to explain the nature of mail: 
any kinil of grain, such as liarley, l>ere, oats, wheal, 
millet, rice, maize, or rye, by Iwing made to germinate, 
antl the germination immediately stopped, will be thus 
converted into malt. B^ tV ^laoCTao^ ^fcrroMMAtj^,!!™ 
.Jtarcli of the gtwn is spo'ivlB,neaufi\'5 cn^NeiueiVwViBiiiM, 



D^AP. n. VINOUS FERMENTATION, 335 

intended by nature as the food of the embryo plant. The 
instant the sugar is formed^ the process should be stopped^ 
as otherwise it would disappear again. The germination 
is checked by drying the grain. When barley is to be 
malted^ it is first steeped in cold water : after a time^ 
the water is drained off; the barley is spread out in a 
deep heap : it soon becomes warm^ owing to the chemi- 
cal action which forms sugar in it; the rootlets and 
future stem shoot. When this happens^ the grain is 
spread on a heated kiln until it is quite dry. The result 
is malt. When grain has been made to germinate^ and 
the further growth of the embryo plant is checked by 
drying, '^ its vital principle is extinguished for ever." * 
The ferment is the body which possesses the power of 
commencing the fermentation ; jand once commenced, it 
proceeds without further assistance. Its presence is so 
necessary, that a solution of pure sugar will not ferment. 
There are many substances, however, which combine in 
themselves both a ferment and a fermentable matter. 
Thus, impure sugar, when dissolved in a sufficient quan- 
tity of water, will ferment almost perfectly : the juice 
of the grape, gooseberry, and some other fruits, contain 
both abundantly. The ferment commonly used by 
brewers, distillers, vinegar makers, and bakers, is yest or 
barmy — the scum which rises to the top, and afterwards 
falls to the bottom, of those vessels in which the fer- 

* The passage marked above by inverted commas is taken from the first 
volume of Domestic Economy, written by me for the Cabinet Cycloiisedia. 
It was some tiirie since brought forward as evidence in a revenue tri.il, in 
such a manner, that I was induced to make experiments with a view of 
ascertaining how far those authors, from whom I took the statement, were 
eorrect. 

1 procured several samples of pale malt of the best quality from diflfbrent 
com Actors and brewers. They were sown in diflfferent drills about the be- 
ginning of April, along with a drill of barley. The barley grew in course j 
but for three weeks there was little or no appearance of the malt. The 
malt then sptang up abundantly in all the drills, and, at length formed good 
ears of corn. The only difference was, that the malt, in shooting, forming 
ears, and ripening, was always three weeks later than the barley. 

Next year I procured fVom an eminent corn factor some pale mnlt, picked 
grain by grain, each of which he pronounced to be perfectly ma,\ted. I'hese 
were unm in drills as before. Not one grain ever germinated. The year 
after, the experiment was repeated on picked grains, with the same result. 
We may therefore infer, first, that in perfect malt the vital ptiucipW is ex- 
tinct; aeccoid, that the process of malting is very VrnpexteeW^ "^tacW^cdL.', 
Mt/d, third, that the evidence afforded by the gTovrth oC au&i^ecX.edLtcvaNX^vA 

oAmt trougbt Arward by exci«e officers at revenue tha^a, oxxg^X. XoX^ie cnw- 

ideredastavving Dotbing. 



I 



mentation of iofusian of malt is conducted. 
inowii of the nature of fennenta ; yest lias In 
posed to be gluten ; gluten lias been found eapaUe o( | 
producing fennentation, and it is known to exist in 
grapes and gooseberries, 1£ grape juice be deprived of 
its gluten by boiling and filtration, it will not fermenL 
Alcoliol is composed of oxygen, carbon, and hydio- 
gen ; the oxygen in it, if saturated with as much of the 
hydrogen present as would form water, would teaw 
exactly as much hydrogen as would saturate the carhon 
present, so as tu form olefiant gas. Ueuce alcohol may 
he said to be a compound of water and olefiant gas ; or 
the same may be expressed by saying that it is a com- 
pound of oxygen, carbon, and hydrogen. If its com- 
poKition t>e expressed in the latter way, it will stand 
thus r —Oxygen 34-834.1, carbon 52'1035, hydrogen 
I3'06ll — 100 grains: if in the former way, thus: — 



,..rf 1^ 



[raiflly OfllSl 



Si" 



I 

^^P Hence, the specific gravity of the vapour of alcohol, at 
^^B 60°, is 1*58; 100 cubic inches of the vapour wdgh 
^H 48'68 grains ; and 48-6S grains of pure liquid alcohol, 
^V when resolved into its two constituents, would consist 
^^ of 100 cubic inches of vapour of water, and 100 of 
olefiant gas. We have now to enquire how alcohol is 
formed tiom sugar. 

The composition of sugar is so differently stated by 
chemists, that the analyses given can be considered as 
little better than good npproxiniationa. According to 
Berzelius, 100 parts consist of carbon 44-2, oxygen 
4y-0I5, hydrogen 6-785. Dr. Ure says, carlwn 43-38, 
oxygen 50-33, and hydrogen 6-29, "n 100. Gaj- 
Lussac and Thenard. gvve fee mmiida ftvoa-. 4a'4T, 
¥S0-63j aud 6-9. Dr. Prout, gv-ies f*i\»w. Vi%^, wi. 



I. SUGAR. ALCOHOL*. 33? 

ments of water 57' 15. Were we to consider 
lomposed of carbon 39*9315, oxygen 53*394'1, 
sn 6**6744, the following would be the consti- 
jy volume of 95*278 parts ; and the reason for 
g that number of parts will presently appear. 

Grains. Cubic in. 

m vapour 38*0460 being in yolume 300 or 3 vols, 
en - - 50-8729 - - 150 or IJ 

ogen - 6-3591 - - 300 or 1 

95-278 resolvable into 750 



■j according to Gay-Lussac (Annales de Chitn, 
6.), 100 parts of sugar, when made to undergo 
cess of fermentation, are converted into 51*34 
y weight of alcohol, and 48*66 of carbonic acid; 
95*278 grains would afford 48*915 of alcohol, 
'363 of carbonic acid. If, in order to make the 
s correspond with the theory of volumes, and 
'cific gravities of the gases as determined in this 
for reasons assigned, we alter these numbers to 
17 alcohol, and 46*5973 carbonic acid, the fol- 
scheme expresses the changes which happen 
the conversion of sugar into alcohol : — 

Sugar. ^ Alcohol. Cartx)nic acid. 

Cub. in. ' Grains. Grains. 



f200 weighing 25-3640 



vapour -f^QQ - - - weighing 12-6820 

J 50 weighing 16-9576 

' " "L^O^ - - - weighing 33*9153 

jen - 300 weighing 6-3591 



750 con verted into 48-6807 and 46*5973 



comparing this scheme with the composition of 
. given above, it will' appear that the analysis of 
*6807 grains of alcohol is the same. And from 
se statements it may be collected, that 95*278 
of sugar (which consist of gases &mo\m^xi%\j5 
bic inches) are converted by fermenta^wiL VoXo 
^ grains of carhouic acid, and 48'6ft01 ^«at.^o^ 

z 



I 



338 BVBMBH'K or OBnamiT. MWatt 

alcohol, consisting of 100 cubic inches of the vapmrof 
water, and 100 cubic inches of olefiant gas. 'Fhea 
calculationB correspond so accurately with the Tacia, 
that I do not hesitate la adopt them. We may briefly 
express the change thus : some of the carbon and some 
of the oxygen combine to form carbonic add, which 
exhales during the fermentation ; while the renuiodtt 
of the carbon, the remainder of the oxygen, and the 
whole of the hydrogen, combine to form alcohol. The 
fermentation takes place independently of the eleraaili 
of the atmosphere ; the product is even larger when the 
atmosphere is excluded. In the case of grape sugar, 
Gay-Lussac found that, at the beginning of the proceis, 
the absorption of a little oxygen was necessary. 

AcetoiM fermentation. — When a liquor that tut 
already undergone the vinous fermentation, is exposed 
for a length of time to a temperature of 75", the beU 
rises 10° or 15°, a hissing is heard, carbonic add i> 
generated, the oxygen of the atmosphere being absorbed, 
and tile vinous taste gives place Id an acid one. The 
alcohol which the liquor contained is now converted into 
vinegar. Floating shreiis make their appearance, and 
are deposited as a gelatinous magma. These are the 
changes which lake place when a lai^ quantity of 
vinous liquor is acted upon : if the quantity be small, 
no change is otmervable but gradual souring. 

In order to form vinegar, it is not necessary that die 
liquid employed should have undergone a disdncl utd 
separate vinous fermentation. It will answer as wdl if 
a solution of sugar, mixed with yest, be exposed to the 
temperature of 80" throughout, so that the vinous fer- 
mentation shall proceed with rapidity. In this case the 
acetous fermentation goes on simultaneously with the 
vinous J liut the former continues after tile latter hu 
ceased, and continues until very nearly the whole of the 
alcohol is acetified. 

That it is the ako\\o\wVnc.\v is converted into vinegar, 
api>ears from the fact, thai a. let-j ^M'wwivwiase rii iL- 
cahol anij water, a.\Dr^ witSi a ^tie A\mwjii.,Tfiii,"i 



\ 



«BAP,1] 



ro. SSf 



ibout forty tlnys, lose oU traces of alcohol, and 
linear. 

Vinegar may be formed from solution of 
mgar, sweet juices of fruits, especially the grape, in- 
fuaion of malt, &c. By the diGtillation of wood it i* 
obtained abundantly, along with tar, which can readily 
be removed. Cider, if long kept, changes into excellent 
vinegar ; eo also do weak wines and beere. In all cases, 
within certain limits, the greater the quantity of alcohol 
present, the itronger will be the vinegar, and the slower 
its formation. If the liquor be highly alcoholic, it will 
keep any length of time without souring. 

The various kinds of vegetable mailer existing in 
vinegar, although foreign to its consUmtion, render it 
apt to run into putrefaction by the process called mo- 
tiering. This is prevented by distillalion, and less 
perfectly by boiling; but flavour is in the former case 
lost. By freezing, it may be concentrated; for the ice 
is water, and may be removed. By saturating vinegar 
with lime or potash, evaporating to dryness, and dig. 
tilling the dry salt with sulphuric acid, we obtain a 
perfectly pure acid in its most concentrated form. It 
is now colourless, transparent, exceedingly pungent in 
smell, and of a caustic acid taste. In this state it is 
called acetic acid : it does not di^r from vinegar, 
but in purity and concentratioi 
kind, the tarry einpyreumatic i 
rillin g wood may be rendered 
from any other source. 

^Vlien acetic acid is highly concentrated, it is capable 
of cryslaUising. The liquid acid, at 60°, is of specific 
gravity 1-063. Even at this strength, there is some 
water present. If more water be gradually added, the 
specific gravity condnually increases to 1 '073. If more 
water be stjll added, the specific gravity, instead of 
increasing, diminishes continually. The vapour of the 
strongest acetic acid is combustible. 

Theories have been brought forviatd lo ^ccoMaX. ^^^ 

B 2 



By a process of this 
egar procured by dis- 
1 pure as that derived 



( 



I 




I 



ifae foriDitioa of linear during the scetous fennoit- 
ation, foundnl od ihe belief thai the ab^iTptioD of 
oxjKen from the atmosphere is indispensable : utd in 
agency of the oxygen has been supposed to be the 
remoTtd of oubon and h jdn^n from the alcohol, bj 
the fonnation of carbonic acid and water; for it ii 
Jtnown that acedc acid contains lees c&rbon and hydro. 
gen thao alcohoL A theory of this kind, however, bu 
to contend with the fact, that although oxygen ii 
absorbed during the acetous fermentation, and ctrbonic 
acid la formed, this absorption seems to be eSected bj 
some other carbonaceous matter present in the liquor, 
and not by the carbon of die alcohol ; for vinegar nuiy 
be formed perfectly, and with ease, even thou^ die 
access of air be totally prevented. This fact is proval 
by many instances. Beccher included wine in a glut 
bottle, which it filled; he hermetically sealed ihemootb, 
and exposed it to a digesting heat ; after some time ie 
wine was converted into very strong vinegar. (PAyfkB 
Sublerranm, Lipsife, p. 18*.) Fourcroy and Vauqudin 
obtained \inegar from a solution of sugar contained il 
cloie vessels. Homberg included good wine in a botik, 
and having closed it accurately, he fastened it to ibc 
sail of a windmill : in three days it was very gimd 
vinegar. It is a fact well known to every one, thall 
bottle filled with weak beer, and closely corked, tnD \t 
some time be converted into vinegar. It may be aaU 
that air was absorbed through tlie cork : but this conld 
Hcarcely happen ; for, after a cubic inch or two of oiy- 
gen would thus be absorbed, the neck of the bolllt 
would be filled with azote ; and there being now nu 
longer the aid of a partial vacuum, it is hard tA con- 
ceive how air could enter. But the experiment of 
Beccher seems to me irrefragable ; and, I think, we ate 
bound to admit that the absorption of osygen dutttig 
tJic fonnation of vinegar ia incidental, not necessary. 

According to Ga'y.L'u&eac miATViEraad, 100 parh of 
acetic acid consist of 50'i2.4r ca,i\»\i, ^V\Vl oi-^^rl. 



.AC8TIC ACID. 



34t 



their coiiicidence with the doctrine of volumes 
nrrect specific gravities leads to a constitution of 
acid, which eeeraa to be the truth. Let us take 
8 carbon, 44'508 oxygen, and S'SGi hydn^n, 
■ ratio in 100 parts of acetic acid, then the ratio 
1003 partB will be 19-023 carbon, l6-p576 oxy- 
nd 2-1 1 (JY hydrogen. Here the quantity of oxy- 
i the same as exists in 48-6807 parts of alcohol 
le scheme at page 337-), tlie quantity of carbon is 
bic inches less, and the quantity of hydrogen is 
Mc inches kss. The composition of acetic acid 



e oxygen and hydrogen are here in the ratio which 
waUr, as was proved to be the case in acetic acid, 
years since, by Dr. Prout. According to this liew, 
48-6807 grains of alcohol are converted into 
i03 of acedc acid, its oxygen remains unchanged : 
ts with 50 cubic inches of carbon vapour, and SOO 
drogen, which unite, and form the gelatinous cake 
s produced. This, when dried, becomes as thin 
oei, and blazes at the candle, emitting a smell of 
led wood. Its composition may be similar to tllat 
od, the oxygen being derived from the air ; or, 
access of air is prevented, it may be a hydrocar- 
, If alcohol be considered as a compound of water 
lefianl gas, acetic acid will be a compound of water 

le following is a summary of the changes which 
biy happen when 95'278 grains of pure sugar are 
to undergo both fermentations :— 100 cubic inches 
(nrbon vapour combinewith an equal volume of its 
jkaiid form 40'59~3 grains (rf caTWiM.aiwi,'*'™*^ 



I 



I 

I 



escapes. The remaining 200 cubii? inches of iU oAcm 
vapour combine with the remaining 50 cubic inchci of 
its oxygen, and 300 (the total quantity) of its hydrogen, 
producing 48-6807 grains of pure alcohol. Of tha 
carbon vapour contained in tliis alcohol, 50 cubic inchea 
combine with 200 of its hydrogen, probably conid. 
luting the gelatinous dime ; while the remaining 150 
cubic inchea of carbon vapour combine with the n- 
raaining 100 of hydrogen and 50 (the whole) of the 
oxygen to form SS'lOOS grains of acetic acid. 

The acetous fermentation requires its peculiar fer- 
ment as well as the vinous. What its nature is, we do 
not know ; but it is believed to resemble the vinous fer. 
ment, in being some moditication of gluten. When i 
saccharine liquor ferments, the fermentation will pro. 
ceed (o tlie acetous stage, if the quantity of alcohol 
evolved be Email, and the temperature be kept up. Bui 
although, in this ease, the vinous ferment produced die 
acetous fermentation, the acetous ferment never pro- 
duces the vinous fermentation. The slime found in the 
bottom of vinegar vats acts as a good acetous ferment 

FutrpfacliBe fermentation. — Tlie putrefactive fer- 
mentation afiecta both animal and vegetable matRi. 
Animal matter consiBls chiefly of oxygen, hydrogen, 
carbon, and azote. During ite putrefaction, hydn^D 
and azote combine and form ammonia ; hydrogen ^ 
combines with oxygen, forming water, and with carbon, 
affording carburetted hydrogen : carbon and hydrogen 
also unite and form carbonic acid : the chief part of the 
carbon remains in some obscure state of combination for 
a series of years, if air be excluded; but if not, the carbon 
disappears after some time. 

The smell of putrefying animal matter is in part 
attributable to phosphorus and sulphur, which exist in 
small quantity in it, and which dissolve in hydrogen 
during the new order of affinities. But beside tb* 
odour of these, there is some other far more disi[gree< 
flWe, the source of w\ac\i ia TiQXVmy»n\j'aQX.'ni».'j deqeod 



tXBAP. II. PUTREFACTIVE FERMENTATION. 545 

on the solution of animal matter in some of the gases 
evolved. 

Putrefaction does not take place at low temperatures : 
hence the hodies of animals have heen preserved for 
ages in ice^ as fresh as at the day of their death. Moist- 
ure is so necessary^ that animal matter^ which has heen 
dried by accident or design^ will keep a great length of 
time. Of this^ the catacombs of Palermo^ where the 
dead bodies are preserved indefinitely long by the mere 
process of drying^ afford a striking instance. 

When vegetables putrefy, the* changes are not so 
complex, because the elements concerned are fewer. 
The oxygen combines with hydrogen ; another portion 
of hydrogen combines with carbon. The chief part of 
the carbon remains as such, unless free access of air be 
admitted, which then slowly combines with it. 

During the putrefaction of animal and vegetable 
matter, much heat is produced ; and if the mass be con. 
siderable, the heat continues a long time. I foimd the 
heat of a heap of stable manure 135^, and it maintained 
this temperature for a week ; but it continued very warm 
for two months. Hay that has been stored damp often 
takes fire. 

I once witnessed a singular case of putrefaction, 
which seems worthy of notice, as I do not remember to 
have seen any account of a similar case. It occurred 
at the Richmond Hospital school of medicine in Dublin, 
I tiiink in 1828, and was seen by most of the lecturers 
and pupils. The body of "a girl, about thirteen years of 
age, was laid on the dissecting table : there was nothing 
remarkable in its condition : it was summer. In some 
days a white smoke began to exhale, which increased 
for two days, and then became very dense. There was 
no more fetor at first than in ordinary cases ; but at 
length a smell so intolerable arose, that it was necessary 
to remove the body to the vault. I occasionally watched 
it, but nothing further occurred ; the smoke in a few 
days more ceased. There was no YieaX. Aev^o^^^ ^^^ 
/ could perceive. 

z. ^ 



I 



Ethers. — IVhen equal weights of alcohol and sdphu. 
ric acid, both as strong as possible, are distilled, a liquor 
oomea over, the chief ingredient of which is « li^t, 
odorous, colourlesa, highly volatile liquid, of a pene- 
trating taste and smell. This is called ether; ind u 
there are other etiiers, it, for distinction, is called 
tviphuric ether. 

According to the analysis of Dumas and Boolky, 
100 grains of sulphuric ether consist of oxygen 91'S4, 
hydrogen 13'85, and carbon 65-05. If we correct thoe 
numbers so as to make them correspond with die theory 
of volumes and the specific gravities of the gases which 
seem best supported, we shall have the analysis Aiu: 
— Oxygen 2I'66'l6, hydrogen 13'5386, and carbon 
f)4<-799S = 100. According to this corrected arulyait 
of lOO grains, S^-WiG grains would consist of oxygen 
8'4788, hydrogen 5-2!)98, and carbon H5-3640. Com- 
paring this with the analysis of 4'8'6807 grains of 
alcohol, stated at page 337., it will appear that tlie quan- 



tity of carbon la the sara 


in both. 




A!cDhoL 


Oraln^ 


°issr 


Oxreen I e '9576 
Hydrogen e-35HI 
Carbon SS-oG^lO 


8-4788 
3-2993 


B-478B 


<8-fiS07 


2yH50 


9-.6MG5 



L 



The difference of composition between 48'6807 grwns 
of alcohol and 29-l+2f) grains of ether exists only in the 
oxygen and hydrogen; ami the quantity of these gases 
which constitute the difference are as 8 to 1, which b 
their ratio in water. Now, if we convert the above 
table of grains' weight into the volumes which iOt/J 
represent, it will stand thus : — 



CBAP. II. . SULPHURIC ETHER. 345 

Vapour of Vapour of Vapour of 

alcohol ether. water. 

Cub. in. Cub. in. Cub. in. 

Oxygen - 50 - 25 and - - 25 

Hydrogen - 300 - 250 and - - 50 
Carbon - . 200 - 200 



550 475 75 



condensed into 100 37*1 50 

From which it is obvious, that if, from 100 cubic 
inches of the vapour of alcohol, we abstract the ele- 
ments which constitute 50 cubic inches of watery 
vapour — that is, half of the total water in the alcohol — 
we shall obtain 37*1 cubic inches of the vapour of 
ether: for the ethereal vapour weighs 29*142 grains; 
and 100 cubic inches weigh 78*^84 grains, as will 
herieafter appear. 

It has been already shown, that alcohol may be con- 
sidered as a combination of olefiant gas and vapour of 
water, in equal volumes, condensed to one half. In 
y the above case, 200 cubic inches of carbon vapour are 
combined with 200 of the hydrogen, forming 1 00 of 
olefiant gas; and the remaining 100 of hydrogen are 
combined with the 50 of oxygen, forming 100 of 
watery vapour. In ether, 200 cubic inches of carbon 
vapour are combined with 200 of hydrogen, as in the 
case of alcohol: but the remaining 100 of hydrogen, 
and 50 of oxygen, which the alcohol contained, al- 
though in combination, fare divided into equal parts ; 
one half the volume of watery vapour only remaining 
in the ether, and the other half being eliminated as 
water. It tfierefore appears, that the change which 
alcohol suffers in becoming ether, is, in effect, the sur- 
render of half the water which existed in a state of 
combination in it. Ether is alcohol minus half the 
water of the latter. 

Whether this is the only difference, is a controverted 
question. It is generally believed, lYiaX. Vtv «^!wJti.^ «sv\ 



I 



I 



ether, the carburet of hydrogen is the same ; and thu 
it is oleliant gas which, as already shown, consists of 
two volumes of carbon vapour and two Tolmnei of 
hydrofien, both condensed into one volume. Dr. Thoai- 
Eon maintains the opinion, that the basis is what he 
deiiominales telarto-caibo-hydrogen, or what I hive 
described in page 17I. under the name duplocarbiuel of 
hydrogen, consisting of four volumes of carbon vapour, 
and four of hydrogen, both condensed into one. Ilii 
obvious that, in either case, the ratio of the eleinenlaiB 
the same ; and the only difFerence is the mode in whidi 
they are combined, — a subject on which we know ahnoat 
nothing. Dr.ThomBon cannot prove hia opinion lobe wd 
founded, nor can any one else prove that it is incorrect 
The fact that the hydrocarburet is evolved in the state of 
olefiant gas, when sulphuric acid acts on a small quan- 
tity of alcohol, does not seem favourable to Thomson's 
view, although it does not decide against it. 

The theory of the formation of sulphuric ether is 
also a controverted subject. It had long been believed, 
as it is still by many, that when sulphuric acid and 
alcohol are distilled, ether is formed, because the atSnity 
of sulphuric acid to water is such as to subvert the com- 
bination of the elements of the alcohol when aided by a 
high temperature, and to withdraw half its water, ot 
the elements of water, in the manner already described. 
This view is supported by the fact, that an ether, 'which, 
according to Boullay, is absolutely the same as sulphuric, 
is obtained by the intervention of some other acids which 
have a powerful affinity for water, as arsenic and phos- 
phoric ; hut it is opposed by tte following conuder- 

When equal weights of alcohol and sulphuric aciil 
are mixed, and no artificial heat applied, ^e result is 
not a mere mixture of these two liquids ; for, although 
sulphuric acid forms insoluble salts with lead and baryta, 
the above mixture affords soluble salts with these bases. 
7h fact, the olefianl gas of i^ie iAtdrio\ »W* ^!fte ^la*. of » 
baae: it loses its gaseous ala.W.ccmilaw.e'i-wV'Cft-vatae^aa 



half of the sulphtiric acid ; and the latter, in conse- 
quence of the union, loses half its saturating power. The 
comhipation of sulphuric acid with oleflftnt gas con- 
edtutes an acid different from all others ; it is called 
sulphavinic add. This, accordingly, is the chief iii- 
gredienl when alcohol and sulphuric acid are mi\eiL 

WTien sulphovinic acid is distilled, it is decomposed ; 
the sulphuric acid reappears in its original state ; and 
the other element, carburet of hydrogen, (which would 
be oiefiant gas, were it in the gaseous state,) combines 
with water that had been present in the sulphovinic 
acid ; and, accordinj^ to the quantity of water with which 
the carburet of hydrogen combines, ether or alcohol 
will be formed. Jf there was mudi water in the sul* 
phovinic acid, the result wilt be alcohol ; if little, ether 
will be produced. This fact favours the idea that the 
hydrocarbon in alcohol and ether is the same- 
It has been suggested by Mr. Hennell, the discoverer 
of the chief facts relative to the theory of the formation 
of sulphuric ether, that when equal weights of alcohol 
and sulphuric acid are distilled, the resulting ether may 
be not formed by the direct action of these two bodies, 
but indirectly by the previous formation of sulphovinic 
acid, and its continual decomposition, and recomposition 
from the residual unaltered quandties of alcohol and 
sulphuric acid. During the distillation, he tested por- 
tions of the liquid in the retort taken at different periods, 
with acetate of lead ; and found that the quantity of 
insoluble sulphate of lead precipitated continually in- 
creased, because sulphuric acid was continually evolved 
by the decom position of the sulphovinic acid. The 
reason that ether, and not alcohol, is generated during 
this distillation, is, that the quantity of water present, 
and not held by the sulphuric acid, is only sulHcient to 
afford ether by union with the carburet of hydrogen 
evolved from its combination with sulphuric acid. But 
if, previously to the distillation, water had been added, 

a tie reEiilt woahi not be ether, but a\tti\io\- 
f.At the commencement of the ptoceaa fot doixovva?. 



I 



H^ sir. 
^h teal 



etber, thai liquiil onljr is prodaced along widi 
quantity of alcohol, AlTien nearly the whole of lie 
ether generated has paased over, oil of whte dietils ; llut 
fluid, according to Mr. Hennell, coudsts of snlpbiiri( 
add, neutralist b; carburet of hydrogen, and not in 
the least acid ; it iliffere from sulphovinic acid only in 
eontwning twice as much carburet of hydrt^en. OlelUnl 
gpa is disengaged about the same period. Then VHM 
water, sulphuroua acid, and carbonic acid. The liquet 
in the retort blackens and thickens with evolved chii- 
ooal ; and when culd, I have found masses of a aaSA 
black pitch in it, resembling common pitch. 

A theory of etherisation must account for aU ibw 
jdienomena. In the subsequent stages, n-e must snppow 
■.that the alcohol which had diluted the sulphuric add 
rlleing now for the most part removed, the water wlud | 
'■was abalraeled from the alcohol having distilled ova, 
■nd the Hulphovinic acid all decomposed, the sulphiuic 
acid is in so large a quantity, and so much concentrated, 
that it acts with greater enei^ than ever on a litde 
alcohol remaining. The water is totally nithdrswn 
from this alcohol ; and it is hence resolved into carbant 
of hydrogen, part of which escapes as olefianl gas. The 
other part reacts on the sulphuric acid ; sulphurtms 
and carbonic acids and water result, and diadl over. 
The pitch is tlie last remains of the carburet of bydco- 
gen, which, no doubt, would have been eventually de- 
composed by the sulphuric acid. The reason that the 
Hiphuric acid and the carburet of hydrt^en, at the end 
t>f the procesB, do not form sulphovinic add, as at the 
banning, h, that the temperature has become consider- 
ably elevated, 

When tile vapour of ether is mixed with three times 
its volume of oxygen, and a burning body applied, it 
explodes with violence. A dangerous explosion oc- 
curred to me from the casual inlermisture of common 
ipparatus in which ethw had been distilled, — 
a candle having beeti a^pfeAtol^e ^"^«<^»W"t- "^Qiaiti- 
rJte vapour ol eftver ■pvirfec'LV^ , ^'^ '°^™^ ""'^^ 



cSap. t 

require 600 oF oxygen ; the results are, water, and 400 
cubic inches of carbonic acid. It ie obvious, that 
oxygen does not change its bullc in Incoming carbonic 
acid, and reijuires its own volume of carbon vapour, 
there muat have been present 400 cubic inches of carbon 
vapour; and as the remaining 200 cubic inches of oxygen 
formed water, they must have met 400 of hydrogen. 
But the analysis already stated ebows that water waa 
originally present, the constituents of which amount to 
50cubicinchesof oxygen, and 100 of hydrogen. Hence, 
ethereal vapour consists of 400 cubic inches of carbon 
vapour = 50-728 grains, 500 of hydrogen = lO-S^SS 
giains, and 50 oxygen = l6'957(i grains ; in all, 950 
cubic inches, condensed into 100, weighing 72'284I 
grains ; and hence the specific gravity of ethereal vapoot' 
ia 2'5407 hy calculation. Gay-Lussac found it, ' 
periment, 2'586, and Despretz 2'5808. 

Ether is a liquid of a penetrating taste and agreeably 
smell. Its specific gravity, when pure, i. ' ~ 
boils at <)6'^ ; but evaporates in the open air 
peratUTes, and produces so great a cold, that water may 
readily be frozen by it. It is soluble in all proportions 
of alcohol, hut only in a very large quantity of water. 
It dissolves -/, th of sulphur, and ^\,th of phoaphorus. 

There are several other ethers known beside the sul- 
phuric ; but their nature is so far diSferent, that they are 
combinations of the acid employed in their formation with 
other elements. Thus we have nitric ether, a compound 
of hyponitrous acid with the same elements as exist in 
aulplinric ether. Muriatic ether consists of muriatic 
acid, carbon, and hydrc^n. Chloric ether contalna 
chlorine, carbon, and hydrogen, Hydriodlc ether is com- 
posed of iodine and olefiant pas. Acetic ether is a com. 
pound of acetic acid and the elements of sulphuric ether 
Oxalic ether is similarly constituted, but contains oxalic 
instead of acetic acid. There are a few others, but 
they possess no interest. 



I 



?iirt#' 



I 



One of the most remarksble, important^ and least undet- 
Btood phenomena in naturC] is the process of combustion. 
It has, unsuccessfully, occupied the attention of philn- 
Bophers in all ages ; and even at this moment, the chief 
difficulty remains unexplained. It would be in yain 10 
detail the different theories which have been advanced, 
even in comparatively modem times, as they have not 
now a single advocate. The theory which, of late jinn, 
has occupied most attention, is that of Lavoiuer; die 
diief positions of which had been advanced in l665,bj 
the ingenious, or, as might be said, considering tbi 
period, the illustrious Dr. Robert Ilooke. But, owing 
to circumstances, his opinions were forgotten ; and, in 
all probability, were utterly unknown to Lavoisier. A 
very remarkable part of Hooke's doctrine on combustion 
is liie following : — " This action, or dissolution (i. t. 
combustion) of inflammable bodies, is performed by i 
substance inherent in air, tliat is like, if not Ihe ftty 
tmrie teitk, that wMeh is found in mltpetre." Here is Hbt 
foundation of the Lavoisierian theory, the combination 
of the combustible with oxygen. But Lavoisier hai! 
made the experiments, from which hit theory was au 
ferrihie, long before any such theory was inferred j and 
we And him, in his Opvsculeg Phyiiqiies et Chimiqueii, 
1773,utterly ignorant of the conclusions to which the ex- 
periments there described, and others not contained there, 
afterwards led him. According to Lavoisier, combuilioii 
can never take place hut whrai oxygen is present. Oxygen 
gas is, according to Lavoisier, a compound of a gravitating 
baae, caloric, and tight. When a combustible substance 
is exposed to the necessarj tew^ierMnre in oxygen gas, 
the latler is decomposed, ft\eg,tai\\a,'in¥,\iBa\*Q'i.'Ci\e^K 
eomhinea with the combustMe, w& tVs Veax (mi'fi^\ 



S5l 

scpBjate from the \^aa in the form of fire. Thus, the 
latent heat of the oxygen gas is the sensible heat which 
spears in the phenomenon : and he attributed to oxygen 
gas a greater quantity of latent heat than to any other. 
A different explanation of the source of the supply of 
heat was soon found necessary. It was supposed that the - 
mean capacity of the oxygen and combustible, is greater J 
than the capacity of the Eubstancc formed as the pro»fl 
duct of the combustion ; and that the excess of the for. ^ 
mer heat should be evolved, and rendered senBible, a* 
we iind it to be. But modem researches do not cor- 
respond with these Etatemenls : it is found that the pro- 
ducts of combustion have sometimes a greater capacity 
for heat, than the substances between which conabustion 
took place. For instance, it was supposed that carbonic 
add has a less capacity for heat than oxygen gas : hence, 
when charcoal is burnt in oxygen, the heat developed ia 
chiefly the difference between the specific heats of the two 
gases. But it has been since affirmed, that carbonic acid 
gas has a greater capacity for heat than oxygen ; and, if 
this he a fact, it ought lo happen, according to the tlieory, 
that in the formation of carbonic acid, as there is no 
condensation, there should be an absorption of heat and 
production of cold, instead of a brilliant combustion. 
Nitric acid and nitre, in both of which the oxygen has 
lost all the heat that belonged to it as a gas, are capable 
of affording combustions with combustible bodies, the 
heat resulting from wliich is much more considerable 
than oxygen, in the soUil state, ought to give out, coo- 
aistently with the doctrine of cajiacity. If, with Robins, 
we suppose that a cubic inch of gunpowder, when ex- 
ploded in a vacuum, produces 244 cubic inches of gas, 
die enormous quantity of heat necessary to supply the 
increased capacity of the particles, now become gaseous, 
cannot possibly, according to this doctrine, he derived 
from solid oxygen, wliich, were it even in the gaseous 
state, would contain less specific heat. In such caee&, 
recourse must be bad to latent heal. 
Another defect that was soon obaervei m ftw 'Oaewi 




I 
I 



I 



of Lavoisier, related to the emission of ligbt t 
buatioii. The quantity and qu^ly of the light evolied, 
WBE found to depend on the nature of the catnbtutiUe; 
and it frequently occurs, that light in abundance appean ' 
in combinationa, when oxygen is not present. A moii- ' 
fied theory was then proposed: — Oxygen gas conaXl 
of oxygen (as the gravitating hase was called) coin- 
bined with caloric. CombusdbleE coneiEt of an unknowi] 
base, combined with hght. In combustion, a doublede- 
composition takes place: the oxygen gas gives up ill 
heat, and the combustible its hght ; the heat and light 
combine, and form lire ; while the oxygen and com- 
bustible base form the new product. This theory is, of 
course, hable to the same objections with regard to t!w 
source of the heat. 

The difficulty arises, in part, out of the opinion, 
that heat and light are material agents. But did 
circumstances permit our understanding heat as a mere 
condition of matter, which, in my opinion, they do 
not, one source of difficulty would be removed. It ip. 
pears to me, that, admitting the materiality of hesl. 
we shotdd not singly look for its source, during com- 
bustion, in changes of capacity, or in the quantity whidi 
bmlles contain in a latent form, in consequence of tluir 
being hquid or gaseous. We do not know suffident 
<m the subject of the quantity of heat rendered l&tent in 
changes of state, or the alteration of quantity that ariia 
out of change of capacity, to render such a restriction, H 
to the source of what is developed in combustion, safe 
in such investigations. When phosphorus, charcoal, 
sulphur, or a metal, bums in oxygen or chlorine, at 
when gunpowder bums in a vacuum, much heat is 
evolved. This must certainly proceed from the solid 
or the gas, or, most probably, from both. We have not 
any knowledge of the rca.1 zero of temperature ; but it 
teems certain that the absolute quantity of heat con. 
tained in matter muBt aKcmmt, for that developed in 
combustion. Unti\.Bome\.\ivn%mOTe"?^eci5c\fi\.Tin™^(A 
the quantities of heal w\\\c\\ comxixvae ■i!na\«jm.i t£«»«. 



COMBUSTION. 353 

nt states of existence in matter^ or the specific 
s which different kinds of matter require, it 
It prudent to refer the heat of combustion to 
ral stock which all matter contains, without 

the circumstances by which such heat is re- 
in its recondite residence, as to solidity, liquid- 
iseous form. 

are not the only difficulties that beset the La*. 
1 theory of combustion. Its fundamental po- 

that combustion never takes place but when 
3 some way or other present. At its first pro- 
1, combustion was identical with oxidation : but 
ish chemists made the essential difference to 
1 the simultaneous development of heat and 
h the occurrence of oxidation. Indeed, the 
las been needlessly perplexed by a want of 
t as to the meaning of the term combustion ; 
ler words, what class of phenomena should be 
d as constituting it. It is singular that, in aL 
chemical works of the day, oxidation, the main 
^ the French theory, and the insurmountable 
o the disposal of the question, is still retained, 
the use of such a restriction.'* It unnecessarily 
es the difficulty, by excluding a numerous and 
t class of phenomena, in which heat and light 
rned without oxygen. Why should we not 
word combustion in its obvious and popular 
»n, — that meaning under which it was origin, 
ted in physics } We say, the fire burns, a 
burns ; and we merely mean that intense light 
are emitted from a body affected by some con- 
ich we do not further trouble ourselves about. 

taken by sir H. Davy seems tome by far the 
lonant to phenomena, and to divest the subject 
difficulties which a useless restriction has im- 
m appearances quite difficult enough in them. 

comprehend. Generalisation is the great in. 
of research, as well as of meuvoi^ *, wv^ ^^ 
imber of facts a geneiali&alioii coTX\aM\&, xiftfe 

A A 



I 



more important an instrument it becomes. Sir H. Diiyi 
simply an expression of facts ; and it aeani U) 
comprise all die IngreUients of an adequate definitiw. 

The restticied sense of combustion was founded on 
the admission, that nothui); could bum unless ox;gQ> 
were present. The progress of discovery haadeTd»prf 
so many exceptions to the theory, that they now tqiul 
the number of the conforming instances. If a meul i> 
burnt in osygen, the case is avowedly one of comboslioii: 
but if the same metal is bamt in chlorine, >i _ 
same appearances, it is not combusCion ; it is dien de. 
aignated by the timid name deflagration. If potasaiinii 
be heated in oxygen, it is admitted that combiudoo 
takes place : but if potassium be heated in cyant^en gu, 
the metal burns with the same splendour, yet thisia 
comhuslion. Iron wire undergoes a brilliant combnadra 
in oxygen : iron heated in milphnr bums with all dw . 
iqipearances of brilUant red Are. Why should not ibil 
be a case of combustion equally ? The metal thorimiBi, 
when heated in gaseous sulphur, burns just as well uin 
gaseous oxygen. Should notboth phenomena be eqalUy 
entitled to be consdered as combustions? Whengno- 
powder is heated, it explodes with considerable emiw» 
of heat and hght: there is another powder, iodide o^ 
azote, which, when touched or heated, explodes vicdently, 
and evolves intense heat and light : one is called Gom- 
hustion, the other is not. A mixture of onygett lod 
hydri^n, when heated, explodes with the productioo of 
heat and light. If that gaseous compound of oxygen 
and chlorine, called euchlorine, be heated, it explodd 
with the sensible phenomena of fire also ; the circnitu 
stance that the former is a case of combination, and iht 
latter of decomposition, affords no grounds for denying 
that both are cases of combustion. (Thioride of azote, 
if heated, explodes violently : peroxide of hydrogen, if 
dropped on oxide of silver, explodes : anhydrous liqtud 
hydrofluoric acid, if brought in contact witli potaasioiDT 
explodes: and gaseous \>\\v^4ios"*^ "i^ '^as' 
sulyected to dimimsbed-pTeasoie, es-i^Voi-ia^ 




. ni. ooMBusnoK. S5B 

[ these instances^ and many more^ in which deto. 
a happens, the phenomena of fire appear ; yet they 
ot admitted as cases of combustion, 
ie flame, which frequently accompanies combustion^ 
sts of heat and light; the latter being sometimes 
imensurate with the former : thus, the flame of hy- 
;n, when perfectly pure, emits scarcely any light ; 
i good oil gas, which produces much less heat. 
Is a dazzling illumination. According to sir H . Davy, 
ae is gaseous matter, heated so highly as to be lu- 
us, and that to a, degree of temperature beyond the 
5 heat of solid bodies ; as is shown by the circum- 
e, that air not luminous will communicate this de- 
of heat. This last is proved by the simple experi- 
of holding a fine wire of platimmi, about the 
of an inch from the exterior of the middle 
le flame of a spirit lamp, and concealing the 
: by an opaque body ; the wire will become white 
in a space where there is no visible light." — 
[lenever a flame is remarkably brilliant and dense, 
y always be concluded, that some solid matter is 
iced in it : on the contrary, when a flame is ex. 
sly feeble and transparent, it may be inferred that 
lid matter is formed." — " The density of a com- 
flame (that of a gas light or candle) is propor. 
I to the quantity of solid charcoal first deposited, 
ifterwards burnt." — '^ But to produce this depo- 
I from gaseous substances demands a higher tem- 
ure." — " By inflaming a stream of coal gas, and 
Qg a piece of wire gauze gradually from the summit 
5 flame to the orifice of the pipe, it was found that 
pex of the flame, intercepted by the wire gauze, 
led no solid charcoal ; but, in passing it downwards, 
charcoal was given off in considerable quantities, 
prevented from burning by the cooling agency of 
dre gauze ; and at the bottom of the flame, where 
r&s burnt blue in its immediate contact with the 
ipberej charcoal ceased to be deposited.** * 

• Davy on the Safety Lamp, &c. 91. 5*. ?! . 51. 
A A 2 



\ 



From these stBtementB, it does not very deulj 
appear how " soVul matter is produced" in a btQUuit 
(tense flame, and how solid charcoal ia to be undenlwd 
as " first de|Hi^ted, and afterwards burnt," in acanmcn 
flame. ^Vhen a stream of coal gas is set on fire, tlu 
esperiment of cotlectlng carbon on a piece of vat 
gauze held in the flame, seems to prove that the guii 
decomposed. But one would he inclined to im*^ 
that the r^stdting carbon would separate in vipmr; 
Uid that its appearance in the solid state on the wiic 
gauze happened merely on account of the casual con- 
densation ; the temperature of the wire being infinitdj 
beneath that of the flame, as shown in the first (ape- 
riinent quoted, and also beneath that at which wAoa 
could remain a vapour. It does not appear easj Id 
comprehend in what manner carbon, (merging ftom iIk 
gaseous state in carburetCed hydrogen, and instandy pur- 
ing into a new gaseous state by combining with oxjgeO. 
could have been depositedin the solid state in the flame; 
or how its existence in the flame as a solid could tendtr 
the flame in a high degree luminous. Not only doa 
it seem tliat no appreciable time intervenes, but Ani 
there ia no conceivable interval between the moaienHrhen 
the carbon is admitted to be a vapour, and its metifflor- 
phosis into another state of vapour (carbonic acid) during 
combustion. It seems to me, that the only inferniM 
we can draw is, that the presence of gaseous carbon ia 
hydrogen causes the latter to bum with a wliite light in 
some manner uninown : and this amounts to nothing 
beyond a statement of a fact. 

I conceive that there is something else in opention 
besides the deposition of solid matter, in flame, wtiicb 
causes the evolution of a dense light. On thia eultjecll 
made several experiments some time aince : they «« 
yet imperfect. The following is an abstract of a fr* 
of them : - — A soUd, unchangeable body, when heated U) 
degree, becomes luminoos ; and the hotter i' 
the more intense va ihe \u^i. viXvidnW «»*. 
no reason W \wlie\c xbsA 6«me, -rfoKuc-w-o 




BtAP. ni. COMBUSTION. 357 

atiire may be^ is not capable of existing at different 
smperatures. Consistently with the analogy of other 
VBLtter, we may suppose that^ at high heats^ it is more 
iminous than at lower. This supposition accords with^ 
ud is borne out by^ facts. If a single jet of coal gas^ 
com a tube of very small bore^ be kindled^ it bums 
rith a flame which, except at the bottom^ is brilliantly 
rhite. To try the effect of lowering the temperature 
f this flame^ I made a hollow cylinder of ice by means 
tot necessary here to describe^ the diameter of which 
ras about half an inch. By inclosing the jet in 
bis^ so that the flame was in the axis of the cylin- 
ier, like a lantern^ the flame instantly became blue^ and 
howed almost no light : it at length went out. The 
ame effect^ but less perfectly^ was produced by bringing 
wo pieces of ice in contact with the flame, one at each 
ide^ and very close to each other : and sponges dipped 
n ice water answered nearly the same end. Even by 
dowing one's breath on a jet of flame^ it may be made 
o bum blue. Every one has observed that the bottom 
Ntrt of a common gas light is blue and illuminous; 
ind tihis fact has been the subject of much speculation. 
[ once thought that the carbonic oxide which exists in 
p» was bumt here ; but the foregoing experiment gives 
18 die true solution of the blue colour of that part of 
iie flame. It is partly cooled by the proximity of the 
irass^ but chiefly by the constant current of cold gas 
iseending from the holes of the burner ; these causes 
ustlng in the same manner as the ice. To prove that 
he blue part is not so hot as the white portion^ a very 
limpk experiment will suffice. If a bit of paper, rolled 
q[> as a match, be run upwards through the axis of an 
4rgand gas burner from the underneath crutch, so that 
he top of the paper shall stand in the axis of the hoL 
low cylinder of blue flame^ it will remain unaltered; 
yat if the paper be pushed up towards where the flame 
segins to whiten, it will instantly take Are. The best 
^cumstances for the experiment ate, liliMX \)Svft ^«n!kft, 
9cluded in a glass chimney^ shall \)e ehoxX. «3dA cfcssv- 

A A 3 



f sss 



SLSMXim OF c 



I 



drical throuirhout, Dot coELlcscing at the top ; Koi the 
paper should be viewed by looking down through ibc 
axis of the flame. Another proof that the cunenl of 
gas, from the holes in the humer, cools the flame, it, 
that if a wire heated red in the flame be passed inta 
the current near the burner, it is instantly obscureil bj 
cooling. 

If the cooling of the flame were really the rauK »f 
its blueness and deficiency of hght, I thought, thatbj 
removing the cause of its cooling, the blue migbt It 
cbangedinto while, like the rest of the flame. I theiefive 
tied a bladder filled with coal gas to a long tobacco pipe, 
the bowl being removed. On pressing the bladder, and 
inflaming the gas, it gave off a long stream of flame, oF 
which more than an inch was blue, and the rest white, 
About three inches of the end of the pipe were no* 
heated to wliiteness, and maintained at this degree; 
the bladder being pressed, the flame burnt whiK 
throughout, except about one eighth of an inch; whid ' 
was somewhat bluish. For this experiment a red belt 
will not answer. A non-exptosive mixture of connDOI 
air and coal gas, passed through an Argand inOBB, 
afforded a blue flame without any while light ; for the 
dilution of the inflammable gas by an incombustible «ne 
prevented the flame from reaching the tempetalure 
necessary to its becoming fiilly luminous. I caused I 
massive Argand burner, three inches in diameter, with 
thirty capillary holes, to he maile : and having paned 
good coal gas through it, and kindled the gas, I fonlid 
that the flame was almost totally blue, and shotted 
scarcely any light: the great quantity of brass, and ihe 
cold current, were adequate to deprive the capillary jeB 
of flame of the quantity of heat required for the pro- 
duction of white light. If a red-hot iron be introduced 
into the blue part of a gas flame, the latter instantly be- 
comeswhile; but if the iron be cold, it has no efiect. Tbe 
flame of a taper, held very close to (he blue flame, renden 
It whitish ; but the ttftme oi \wrn\iv^[,m\t\™t wj^ljsd, his 
not this efiect, as it U not suffi-de'tvAi Vox.^ot x^-^'oivw 



OHAP. in. COMBUSTION. SSQ 

Although the hlue part of the flame is colder than 
tihe white^ a thread of glass grows apparently of a 
Vrighter red heat when held in the former; hecause 
llie whiteness, hrilliancy, and semi-opacity of the white 
flame^ conceal the heat to which the glass is raised in 
it : but this is not the case in the blue flame ; for it^ 
"beiiig but Uttle himinous, and very transparent^ aflbrds 
a contrast with the redness of the glass. 

A candle has scarcely any blue light, because the car- 
bonised wick is the worst of all conductors of heat. 
Bat a long wick cools the flame by radiation, and there 
is a diminution of light, although the flame does not 
become blue. 

< A common jet flame of gas is surrounded on all sides 
by blue flame ; for it is every where in contact with the 
eold atmosphere. The eye does not perceive this uni- 
Teraal blue margin, being dazzled with the white light, 
unless a piece of thiclf card, or some opaque body, cut 
precisely to the shape and size of the white part of the 
flame, be interposed between it and one eye — the other 
being kept shut. Then the card appears surrounded by 
a margin of blue flame. 

Carbonic oxide bums with a feeble blue flame, which 
shows very little light: the temperature of this flame 
is also very low. In order to discover if the low tem- 
perature was the cause of its deficiency of light, I filled 
an iron bottle with a mixture of iron filings and whiting, 
both perfectly well dried. The mouth of the bottle 
was stopped with an iron plug ; and in the side of the 
bottle was drilled a hole. The bottle, being placed 
in a furnace^ was heated as high as it would bear with- 
out melting. On drawing it out of the furnace, there 
was a long jet of flame issuing from the hole, which 
was almost white. 

I found that the flames of sulphuretted, hydrogen, 
and even common hydrogen, issuing out of a tobacco 
pipe heated to whiteness at the end, were by no means 
so blue and pale as under ordinary ciicwxa^JudLTLC^^*. *^^^ 
abawed, alao, more light. During wxcYi e^"^eT\xftfe\v\&, ^^ 

A ▲ 4 



I 



EIiEMEKTB Of ORKIfiBTBT. 

tobacco pipe must not be white-hot at the beginliiiig 
merely, but must be Buslained so throut;hout. 

From these, anil many other experiments, 1 infe 
that, although the temperature of flame is not the onlj 
cause of its Ught, but iC is connected wiUi it, and tidi 
Bome other cause unknown. Were the light in pro- 
portion to the lemperatnre, the flame of hyclrogen ahonlil 
he more luminous than tliat of cobI gas. 

The bp;ht and heat of combustion have been it- 
tempted to be explained by the agency of eleclridtj, 
It has been supposed that different kinds of nitltir 
exist, naturally, either in the positive or negative sltle 
of electricity ; that when two bodies thus circumatMcel 
combine, the two elales of electricity annihilate ekd 
Other, and produce a modified spark, which ia th( 
cause of the heat and lip;ht. I have so fully expnmti 
my opinions on this subject, and have iletidkd eoAt 
number of opposing experiments and cnnsiclentiom 
elsewhere •, that, in this place, I content myself bj 
stating my belief that the electro- chemical hypothesis 
it utterly incompatible with all known phenomena. 

In conclusion, tlien, it is perhaps the safest, bewiee 
the most comprehensive, idea for (he student to ai- 
tertain of combustion, that it is the emission of liglit 
and heat from bodies in the act, generally, of combiniitg, 
bat sometimes of separating : that the heat ia pail of 
the combined or latent caloric of the combining bodi«a: 
that the light may aleo proceed from them ; although 

i chiefly dependent on one of them 
bustihie. 




HHAP. IT. ATOMIC THBORY* 36l 



CHAP. IV. 

ON THE ULTIBIATE PARTICLES OF MATTER. THEIR RE. 

IiATIVB WEIGHTS. THE RATIOS IN WHICH THEY COM- 
BINE. NATURE OF ATOMIC NUMBERS. 

The question^ whether matter is infinitely divisible^ or 
consists of atoms *, has been agitated for more than 3000 
years : yet it is still a disputed point ; and our opi- 
nions on this subject^ whatever they may be, are hypo- 
thetical. Unless finite divisibility be admitted, the 
most important series of phenomena in chemistry will 
be left in the situation of ultimate facts incapable of 
fiirther explanation. Yet the phenomena ascend one 
d^ree in the scale of cause and effect ; and are inferable 
d priori, if the existence of indivisible particles be sup- 
posed. Such particles may, for shortness, be called 
atoms: if matter be infinitely divisible, there can, be 
no such thing as an atom; for the word imports that 
which cannot be divided. 

It would be a waste of space to enter into the opinions, 
or arguments made use of by the ancient poilosophers, 
on each side of this question, some of which, if not 
convincing, were at least plausible. Of this kind was 
the curt dogma of Diogenes Laertius, — '' In a finite body, 
there cannot be an infinite number of parts." The 
peripatetics affirmed, that matter is infinitely divisible ; 
and the notion was adopted by the Cartesian school. 
The Epicureans, on the contrary, contended that matter 
is composed of atoms, indivisible, hard, and impene- 
trable. Lucretius, the powerful advocate and able 
expositor of this system, in his well known and beau- 
tiful poem, says, 

Sed qus sunt rerum primordia nulla potest vis 
Stringere, nam solido vincunt ea corpore demum. 

These atoms constituted the v\vj, or first matter, 
of which all things are composed, and concerning which 
to much controversy and incomprehensible xvoXioxv^ «t^ Xa 

• From &T9ixeff indivisible. 



I 

I 



I 



he found amongst tlie ancients. In later times, it wu 
the fashion U> brin^ forward arithmetical and geome- 
trical demonstrations, to prove that matter mtj bt 
divided infinitely ; hut these fail in their ol^'ect, inu- 
mucb as they only prove the infinite divisibility of ihe 
magnitude of matter, and are by no means applicable 
to matter itself. It is certainly true, that any migm- 
tnde, however small, mi^lit he reduced to one bslf ; 
that this half might etill futtlier be divided ; and M 
on for ever, without its being reduced to nothing. It- 
deed, we cannot consider magnitude independently of 
the idea of divisibility without limits; but it alioaU 
Iiot be admitted as on inference, that matter pmniti 
infinite division, because the space which it occu|ue> 
may be conceived to be the subject of an infinite diri- 
Bion. It is possible to conceive the division of a grain 
of sand into a million parts, and each of these pirti 
into a million other parts, and so on. And if at length 
the parts can no longer be conceived to be divided, it 
can only be so because they are annihilated, which, H 
far as human means are concerned, is impossible. But, 
in point of fact, it may l>e true that a grain of sand caB- 
not be divided into more than a thousand or ten thousaiul 
parts; that each part then becomes what we caU in 
atom, or ultimate particle of matter, invisible to om 
best microscopes, and of such cohesion as to resist all the 
ene^es of nature tending to a further division. In 
fine, it seems to me, that much of the controversy which 
so long agitated the philosophers of former times, with 
regard to the infinite divisibility of matter, and which 
St present ought to be a subject of greater interest thU) 
ever, originated in the want of agreement on the nattne 
of the question : one side insisting on the infinite difi* 
ubillty of including space ; and the other side inaistiiig 
on the possibility of a limit to the divisibility of the 
included matter, which, although it may be ro«f«ttw( 
to be surpassed, is not in the operations of satiut. 
Partly in each of liiese senaea nii^^t^ft \»\&enMQd the 
apparently paradoxical ap\iou%m ol "Lewo, ■Cbw.^^umfe. 



CHAP« IV. ATOMIC THEORY. ^ 363 

a body is infinitely divisible^ it does not consist of infi- 
nite parts ; and if he meant that the magnitude of a 
body may be indefinitely divided^ although the number 
of its ultimate divisions is limited^ I apprehend the 
chemists of the present day would not dissent. 

The opinions of sir Isaac Newton concerning the 
atomic constitution of matter^ were nearly the same with 
those attributed to Moschus^ who lived 3000 years be- 
fore him^ except that the former rejected the atheistical 
notion of the eternity of atoms. He says, " It seems 
to me that God in the beginning formed matter in solid, 
massy, hard, impenetrable, moveable particles ; and 
that these primitive particles, being solids, are incom- 
parably harder than any porous bodies compounded of 
them ; even so very hard as never to wear or break in 
pieces, no ordinary power being able to divide what 
Grod himself made one in the first creation." 

In all compound substances, formed by nature or 
art, the compound ingredients are found to exist always 
in the same relative quantities. A piece of marble 
always contains the same relative qu'antities of carbonic 
acid and lime, no matter from what part of the world 
the specimen was derived. Water consists of the same 
proportions of oxygen and hydrogen, whether it falls 
from the atmosphere, or is taken from the subterraneous 
spring, or from the ice of the north or south pole. Salt 
is composed of the same proportions of chlorine and 
sodium, whether obtained from mines, lakes, or the 
ocean. If mercury be exposed to heat in oxygen gas, 
the metal will continually absorb the oxygen up to a 
certain point ; and then, be the excess of oxygen ever 
so great, not a particle more will the metal receive ; 
for a permanent and saturated compound is now formed, 
the constitution of which will be the same, whether the 
experiment was made in Europe or America. From 
such phenomena as these, we derive the important law 
that matter does not chemically combine with matter 
in aU proportions^ but only in one VuNonaX^^fc \^^^ 
quantity for each compound ; and the Ikw \w^'^^ ^oja.^:^ 



whether ihr number of different kinds of matter con- 

Ttwre xrc cases which do not seem redncible under 
ihU lavr, anil which appear to constitute a class of forn- 
tuDalioits in which the suhslances concerned unite in 
all propanions. Alcohol or sulphuric acid, to all appeu- 
UKe, unite chrmically with any quantity of water; id* 
many iRstanrrs of the same kind might be whlnced. Bat 
dtMe unliiuileil combinations may be bo onlyappaTendy; 
we may ounceive them referriblc to the geoend kw in 
(he following manner: — Sulphuric add may comKile 
with a detenninatp and invariable quantity of wstei.b 
Ibnn ■ hydrate ; this hydrate bein); a new eubttuce, 
nay comhiDe with a new determinate quantity of water ; 
and this new compound again with another, and m on : 
Uid all these compounds may unite with each other, N 
aa to afford every conceivable ratio of the ingredients, or 
apparently to dispense with all limits to comtunatioa, 
Either view may be sustained ; but it is remarlcaldj, 
chat, when the exiftcnce of detemiinata ratios is indis- 
tinct, it always happens that the affinity is weak and 
indedrivej and the changes of properties consequent on 
combination are inconsiderable. 

If we admit the existence of atoms, i. f. paiticle« 
wliich can be no further divided ; and also the por- 
tion, that matter can combine with a different kind of 
matter only in a certain invariable ratio ; some very 
hnportant coroUaries may be deduced : one of iheK 
would be, that when two kinds of matter combine to 
form a compound, tJie two kinds combine attun to 
atom. For in order to combine chemically, the two 
bodies must be reduced to their ultimate division ; and 
then an atoni of one kind must, to form the coroponni! 
in question, always combine with an atom of the other: 
it cannot combine with half an atom, for, according U> 
the hypothesis, no such thing exists ; and it cannOI 
combine with two atoms, \wc«iae it is saturated with 
one', that is, its attraction \e wi\6fte4\>i pme ttjaHi,iisA. 



QHAJP.IH. ATOMIO THEOBY. S65 

is HO further exerted. Hence the resulting compound 
consists of an atom of each kind of matter ; and it is 
to be considered as still one atom^ although consisting 
of two : for^ were the two atoms separated^ the com. 
pound would cease to exist as such ; and the compound 
aXoai cannot be divided so that its halves shall still be 
compound^ for the individual atoms, according to the 
Jiypothesis, cannot be divided. There is^ therefore^ a 
great difference between a simple and a compound 
atom : the former cannot be divided ; the latter can, but 
then it is decomposed and resolved into two simple 
atoms. 

In this way, the immutability and constancy of the 
relative quantity of the ingredients composing any body 
become intelligible. If, in a grain weight of any kind 
of matter, there be, as the hypothesis supposes, a cer- 
tain number of atoms, say a thousand, each being indi<- 
visible ; and if, in a grain weight of some other kind of 
matter, there be an equal number of atoms ; and if the 
two grains of matter enter into combination ; it is quite 
obvious that the resulting compound will not only be 
homogeneous, i. e, of the same nature throughout, but 
that in all other cases of its formation, the same com- 
pound exactly will be produced. It will be homoge- 
neous, because each atom of one kind must have com- 
bined with one atom of the other : less than an atom 
cannot have combined, because atoms are indivisible ; 
more than an atom cannot have combined, because the 
affinity is satisfied by one, and there is no attraction to 
another. Hence, each compound atom will consist of 
y^^th of a grain of one kind of matter, and the same 
quantity of the other ; and there wiU be but 1000 
atoms of the compound. But if there had been a grain 
(= 1000 atoms) of one kind, and two grains (= 2000 
atoms) of the other, the very same mode of combin- 
ation would result ; with this difference, that the excess 
of the latter (viz. one grain, or 1000 atoms,) would 
remain uDcomhinedj and merely mixed m\!l[i \2(n& <:^\S!k« 
pound produced. 



BiiiarBirai W 
Bui if it be denied that matter qonsists of Btoms, 
tnd if it be asserted ihat it is infinitely divigible, il 
becomes dlfiicult to comprehend why any ccnstwcy 
should be observable in compounds. For iustance, in 
the case just supposed, in which an atom is equiialeu 

^tOyJ|'iJ^|th of a grain, if the equivalent of an atom of 
one kind of matter may combine with less than the 
equivalent of an at«m of the other, there is nothing tt 
prevent its combining with half, a hundredth, a miL 
Uonth part of an equivalent ; an infinite number nf 
OOmbinationE would be producible ; and it is hard U 
conceive how compounds, constant as we find them in 
their composition, could be produced, or how such ■ 
state KB saturation could occur, unless as a matter of 
chance. If a grain of A may combine with o»J 
quantity of B, there must be as many possible com- 
pounda of A and B as there are possible quantities of 
A and B, or they must he infinite ; and we know that 
this is not the fact. But the case is very much altered, 
if we suppose that there is but one elementary quanlily 
of A and B, viz. the atom of each, and that all other 
quantities are multiplications of it ; for then there can 
exist but one possible combination, consisting of an 
atom of eacli ; the affinity being in that esse satisfied, 
and uo further attraction exerted. 

Hitherto, for tile sake of simphcity, it has been 
taken for granted that different kinds of mutter cool- 
liine only in the quantity of a single atom of one to a 
ungle atom of another, admitting that matter is flnltelf 
divisible. The case is in reality very different; we 
know that two, three, or more atoms of one kind may 
combine with one Btom of another, and that in each 
case compounds of distinct natures result. Cases of 
this kind 'receive as ready an explatuttion, ns those in 
which a single atom combines with a single atom. We 
may understand combinations nf this kind in two ways. 
Suppose an atom of A lo tombine with an atom of B, 
and a compound lo \ie iwmveA. ^aiwewei tS oMihb. 
properties. The affiniis ol K to "ft tob.'^ TOmaa «. 



CHAP. IV. ATOMIC THEORY. 367 

far unsatisfied^ that an attraction to another atom of 
B may exist ; a second atom will accordingly be taken 
into the combination when opportunity permits^ and a 
compound will be formed with properties essentially 
different from those of the former. The same may 
happen with a third atom of B^ and a third compound 
may be produced. Or an atom of A being combined 
widi one of B^ that combination may, in its capacity of 
a compound, exert an affinity for an atom of B^ and may 
combine with it so as to form a compound consisting of 
one atom of A and two of B. This last combination 
may in the same manner take up a new atom of B^ and 
so on. 

Be the mode of combination what it may, it is cer- 
tain that a substance^ A, may combine with such a 
quantity of another substance, B, as will form a definite 
compoimd ; yet another definite compound^ quite differ, 
ent from the former, may be produced, if a second 
quantity of B can be made to combine with the com- 
pound already formed ; and in like manner a number 
of successive quantities of B may produce distinct 
compounds, the number of which, however, rarely ex- 
ceeds three. In all such instances (with a very few 
exceptions), it is found that the successive quantities of 
B, which are added, are equal to each other. That this 
ought to happen, clearly appears from what has been 
already explained of the atomic constitution of matter. 
For the illustration of this subject, let us first consider 
the combination of zinc with oxygen. There is but 
one such known ; to form it, 100 grains of zinc com- 
bine with 23'53 of oxygen ; the affinity of the two 
elements is then satisfied, and no further attraction 
seems to exist. But if another quantity of oxygen 
could be absorbed by the zinc, to form a second oxide, 
it would be at least 47*06 grains, or as much more 
as the first quantity. In the instance of mercury and 
oxygen, experiment proves that, in round numbers, 100 
grains of the former combine with, iovn ^^ ^"fc \3aXX«t 
to form the protoxide. Now, -wliy ^aii \W ^««v^ ^^ 




I 



I 



mercury combLne with four of oxygen? 
supplied by ihe supposition of the alomi 
of matter is, that there are as many atoms of mHwrji 
in 100 grains' weight of it, as there are atoms in fon 
grains of oxygen, no Cwith standing the djfitrence indwl 
appearance and constitution ; hence the two suhstinwi 
combine atom to atom, and afford a compound c 
in its characlers and composition. It, however, by m 
means follows, that each atom of mercury has m 
affinity for oxygen. On the contrary, eEperimenl I 
proves that it has, and that it will unite with an tddi- ' 
tional quantity. But what is the amount of the tiH- 
tional quantity P If, to form the protoxide, each aUn 
of mercury attracted one atom of oxygen, it is obviool 
that, if a further attraction takes place, each atom of 
mercury must attract an additional atom, at least, of 
oxygen ; for there cannot exist less than an atom ; tbll 
is, two atoms of oxygen will be now combined with on* 
of mercury. The 100 grains of mercury, oriptuDj 
combined with 4 grains of oxygen, will now be united 
with 8. But B is the double of 4 ; the new coudt, 
therefore, contains twice as much oxygen as the piot. 
oxide: and were there a third oxide, it would conlan 
■C least three times the quantity of oxygen existing in 
the first, and so on. Molybdenum combines iriA 
oxygen in three doses', forming three distinct oxides: 
the first oxide consists of 1 atom of metal and 1 of 
oxygen ; the second of 1 + 2 ; and the third of I +3. 
Potash combines with two doses of tartaric acid ; m* 
being twice as much as the other. A vast number of 
instances might be adduced. 

• Thsre li nol, perha]ii, a lord in the language Ihat rgpTmienUj «& 
pRua lliE quanllti of n bnlT which enteis Into cmnbinniinn jahU 
not onJr hTpoUiel[calt but often InapplioUiICi m when h, 

EqvhiaietU fi only oKpreiHive when compr-" — -''•*' 

Inl U directly implied. Propartlim meai 

'ioHal \i «lff of the tfnnfl of a proportion. CowbininR vuantih/ or 
omeilraH e»pr«.ire; l.ut bulde tolnit unwieWr, it ft ool dhnM i^ 
■ hie DoKlliam tiiMo., oC i.l.]u, I give,) l> unlverullr enplnrcf to* 
— - -• ■■ T ri^niiP 4--«"-— - •^'"- - - — ' -^ - 




ATOMIC THEORY. SGQ 

cases^ it is a matter of indifierence which of the 
g suhstances we assume as the constant quantity; 
) grains of A unite with 50 of B, or twice as 
)0), or thrice as much (150). Or the same thing 
Impressed hy saying, that 100 grains of B unite 
grains of A, or half as much (100), or one 
nuch (66'666) : the multiple ratio does not 
! kind of matter otherwise than another, 
case of mercury and oxygen just now adduced, 
d that 100 grains of the former wiU combine 
8 of the latter. It may be asked, what, then, 
le consequence, if 100 grains of mercury and 
lediate quantity of oxygen — 6 grains, for in- 
re presented to each other under proper cir- 
es for combination ? will no union take place, 
iie ratio of oxygen to the metal is neither 4 
r will 4 of oxygen combine, and the remain- 
rejected ? Under such circumstances the case 
as follows : — 100 grains of mercury will unite 
of oxygen ; the protoxide will thus be formed. 
; now 2 grains of oxygen to be disposed of; 
unite with as much of the protoxide as con- 
grains of mercury. These 50 grains were 
T combined with 2 grains of oxygen : they 
ombined with two more, four in all; hence 
•ains are converted into peroxide. Thus we 
ve a mixture of 52 grains of protoxide and 
Dxide. 

;ases enter into combination with each other 
ame peculiarity. Thus, when azote and oxygen 
)rm the protoxide of azote, they always do so 
tio of 60-071 grains of azote to 33-915 of 
To form the deutoxide, the same quantity of 
require 67*83 grains of oxygen, or twice the 
uantity : for hyponitrous acid, the azote will . 
rice as much oxygen, or 101*746' grains: for 
id, the azote takes four times as much oxygen, 
grains: and, for nitric acid, the ox^^ewxoaaX 
?s greater, orl69'5^6 graiiks. TYwL^jXXxfe^o^K^ 

B B 



I 



of tixygen thai combine with any quantity of udK, V j 
fortn the foregoing substances, will he to ewh otbetu 
the numbcTs 1, 2, 3, 4, 5; and never Ij, S/J'f,, Snup 
&c. ; nor any olher assignable fractioiiE, however net) 
they may be conceived to approach the whole nunlxn 
bearing the above relation. 

The researches of chemists have proved that thiEmnk I 
of combination, ptr taltum, takes place in almost all ibi I 
cases of decided chemical union which have been mtib | 
the subject of accurau? observation ; and so 
that the phenomena have been generalised into a !iw. 
The law is thus espressed by Serzelius : — " When i 
body. A, combines with a body, B, in several propor- 
tions, the numbers expressing these proportions are in- 
teger multiples of the smallest quantity of B that A csn 
•bsorb." The import of this law cannot be misMkeB. 
In die case of oxygen and azote, the smallest quancitj 
of the former that combines wit!) 100 grains of ifae 
'latter, is S6'458 grains. As they form a second ccm- 
ipound, the quantity of osygen which constitutes die 
second dose, is an integer multiple of the first (that it, 
the first miUtiphed by a whole number), or twice 56"4S8 
^112'9l6. In the third, theosygenis thrice asnuieb, 
or ififl-S?* : in the fourth, the oxygen is four-fidd, Oi 
225-832 : and, in the fifth, it is five-foid, or 282-Sg. 
Thus, the smallest dose of oxygen is multiplied by du 
whole numbers, 2, 3, 4, 5, to give the succesaive coni- 
pounds : or the law may be otherwise expressed, b; 
saying, that the smallest dose of a combining body is an 
■hquot part, or submidtiple, of all the others. Auodlel 
expression of it, which requires explanation, is to be 
found in hooks to the following eiTect : — " When two 
bodies combine in several proportions, the first proporfion 
is either a multiple or submultiple • of all the rest." 
The mode of expression renders this difficult to under- 
stand i perhaps tfie following will he more readily com- 
prehended : — " When two bodies combine in more tiui 
one ratio, the (luantiiies coTvatrtwiivi, ftsi tw, ^wia ue 



Asote. 




O^gen. 


100 


+ 


56-458 


100 


+ 


112-916 


100 


+ 


169-374 


100 


+ 


225 •832 


100 


+ 


282-290 




CHAP. IV. ATOMIC THEORY* 371 

In the relation of multiple and submoltiple to the quan- 
tities which constitute all the other ratios/' The instance 
of azote and oxygen will illustrate this : their combin- 
ations may be represented in two ways ; either gas being 
inade the constant quantity^ and both being expressed 
in weight : — 

O^gen. A tote. oxygen. 

56'45S + 100 =1 

56-458 +50 =2 

56-458 + 33-333 = 3 

56-458 +25 = >t 

56-458 +20 =5 

In the first arrangement^ the first dose of oxygen, 
56*458, is a submultiple of all the rest : in the second 
arrangement, the first dose of azote, 100, is a multiple 
of all the rest : so that the terms, multiple and submul- 
tiple, refer to the two different bodies, and resolve the 
law into the same meaning as the other expressions of it. 

But although, in the combinations of azote with 
oxygen, the doses of the latter are represented by the 
numbers 1, 2, 3, 4, 5> it does not follow that a regular 
arithmetical progression is always to be expected, either 
when weights or volumes are concerned. All that the 
law of multiple ratio, as it is commonly called, declares, 
is, that the doses shall all be multiples of the smallest : 
and no common difference between the terms of the pro- 
gression may be discoverable. Thus, in the combination 
of chlorine with oxygen, the doses of the latter, by 
weight or volume, which combine with a given weight 
or volume of the former, are as 1, 4, 5, 7. Perhaps 
compoimds containing oxygen to the amount of 2, 3, 6, 
may be hereafter discovered : or, perhaps, such may be 
the nature of the affinity, that l^ese compounds do not 
exist 

There is a circumstance attending these, and all other 
gaseous combinations, which ft is of great importance to 
notice. It has been said above, that be the quantities of 
izote and oxygen^ which enter into coinbiTva^ovv^ ^\s»x 
fee/ majr^ the ratio of these quantities -wiiW. ai!bN«L^^^^V««^ 

BB 2 



i ITS BLBjaHM ov aanacRV, 

protoxide is formed, be ftl'071 of azote to 33'9lSo£ 
OKygeu ; and this ratio may be so expressed, or in ia 
Jowest tenuE, vii. I'TJl of azote to 1 of oxygen; oris 
any other numbers, provided that the relation he pre- 
served. The reason for selecting SO'O?] graini, ni 
33-915 grains, is, that the former is (he neight of SOD 
cubic inches of azote, and the latter is the neight of iOO 
cubic inches of ox.ygen. Two to one, then, is the rado 
in ■which these gases combine, by volume, to form lie 
protoxide of azote. Now, as the weight of oxygen is 
doubled to form the deutoxide, tripled to form hypo- 
nitrous acid, quadrupled to form nitrous acid, and qnii^ 
tupled to form nitric acid, the same multiplication mnst 
happen when cubic inches, or volumes of any kind, a 



concerned 



shall, consequently, observe the ewn 
iting between the volumes, as between the 
igbt. The following table will show the le- 




lation in both ways : - 

I'raloiide of mole aOOt 100 or 60-071 - 

Deutoxide - - 200 + 200 or 6007! - 

Hjponitraua acid UOO + 300 or 60-O7t - 

Nitrous ucid- - ^00 + 400 or GOOTI -I 

Nitric acid - - SOO+500 or a0 07t - 
And it ia obvious, that, either by weight or vololPCt 
the relation of the quantity of oxygen in ail the com- 
pounds is as 1, 2, 3, 4, 5, the quantity of azote IwinB 
always the same. The same relation is manifest in »11 
gaseous compoundE, the composition of which is weU 
ascertained; and the facts have been generalised into' 
law, called tJie lain ofrotumes, which has been thus ex- 
pressed by Gay-LusBHc, its discoverer : — " All gasC 
which act on each other, always combine in the mosi 
simple ratios ; the ratio being as 1 to 1, 1 tu 3, or 1 U 
3." • Thus, 1 volume of oxygen requires exacdy 1 
volume of hydrogen, to form deutoxide; and 2 voloma 
0/ hydrogen, to lorm watex ■, 1 No\\sme ol\i.^^ia;g[«.ce' 



CBAP. IV. ATOMIC THEORY. $73 

quires 3 of azote^ to form ammoniacal gas : 1 volume 
^ hydrogen requires 1 of chlorine^ to form muriatic 
acid gas : 1 volume of muriatic acid gas requires 1 of 
ammoniacal gas^ to form muriate of ammonia : 2 vo- 
lumes of oxygen combine with either 1 volume or 4 
tolumes of chlorine. The compounds of azote and 
oxygen fall under Gay-Lussac's general law^ in the 
following manner : — 1 volume of oxygen, and 2 vo- 
himes of azote, form protoxide of azote ; 1 volume 
of azote, and 1 volume of oxygen, form deutoxide ; 
1 volume of oxygen, and 4 volumes of deutoxide of 
azote, form hyponitrous acid ; 1 volume of azote, and 2 
of oxygen, form nitrous acid ; and 1 volume of protox- 
ide of azote, were it to combine directly with oxygen to 
produce nitric acid, would require 2 volumes. Dr. Thom- 
son, in referring to this law, as developed in Gay- 
Lussac's memoir, says, " In this paper, Gay-Lussac shows 
that the gases, considered in respect of their volumes, 
unite with each other in a very simple manner : — 1 vo- 
lume of one gas combining with 1 volume, with 2 vo- 
lumes, or with half a volume, of the other."* I conceive 
that Dr. Thomson*s enunciation of the law is more con- 
veniently applicable to the facts than Gay-Lussac's, as 
in the case of the combinations of azote and oxygen. 
This most important law, which corrects analysis and 
synthesis, has been extended also to vapours ; and even 
to the supposed vapours of bodies, which no degree of 
heat has been hitherto able to convert into the vaporifie 
form ; although it is certain that, combined with other 
matter, they are capable of existing in the state of ul- 
timate division. Thus, 2 volumes of carbon vapour 
combine with 1, or 2, or 4 volumes of hydrogen, to form 
different varieties of carburetted hydrogen ; and the same 
quantity of carbon vapour combines with 1 volume of 
oxygen, to form carbonic oxide ; and with 2 volumes, to 
form carbonic acid. 

It may be here necessary to explain more distinctly, 
what 18 to be understood by the texm caxbou wj/pwwr ' 

• First Principitet,\. Ift. 
B B 3 



■LEUMm or cuEHisTBT. 



yet beOiob- It 



I 



H TOl 

pi 



carbon being a subBtance whitb has n 
toineii insTilaled in the vaporific fomi. If pnrelii1i« 
be burnt in 100 cubic inches of o:iygei) gas, untS i» 
latter be saturated, the oxygen will be converwd into 
carbonic acid, and the resulting volume will still be IW 
cubic inches. The original weight of the oxygen m 
SS-9153 grains: the weight of the resulting carbimie 
acid is 46'5973 : the weight acquired by the oxygen in 
forming carbonic acid is, therefore, 12'682 grains, wludt 
must consist of pure carbon. Now, it is obvious tlul 
this carbon had been divided into its ultimate atonu: it 
became invisible; and WBS,therefore,converted ii 
which flUed the space of 100 cubic inches in every put 
The circumstance, that each atom of carbon is in conlmi* 
ation with an atom of oxygen, does not in the least iSleet 
these statements : thus, carbon may be said, with nf- 
ficient truth for all theoretical purposes, to have been 
Mnverted into vapour, of which 100 cubical inches weigli 
1S'()SS grains; and of which the specific gravity ii, 
therefore, 0'41]6; and aa there t5 neither condensatiaii 
nor expansion in tlie formation of carbonic acid by burn- 
ing carbon in oxygen, die condition of the carbon io 
carbonic acid is to be understood as meant, in cheinicsl 
books, when carbon vapour is spoken of. But if carbm 
vapour were capable of existing in tile insulated state, 
I volume of it would combine with 1 volmne of oxygen, 
to form carbonic add, and the 2 volumes would con- 
In all the instances which have been adduced, dw 
bodies concerned are suttject to the law of multiple ratios, 
whether taken by weight or by volume- There is no- 
myBteriooa in this coincidence of weights soi 
volumes in the second, third, fourth, or fifth doses of any 
hich unites to another, B ; they being only mul- 
_plea by weight, and therefore by volume, of tile first 
dose of A, as also of the volume of B. Thus, in the 
before mentioned comvounda of aiote and oxygen, we 
Had, that to form ptotox\Ae o? a.iave, 60-ty\\ ^wi&KtK. 
raote combine wit\\ 33-915 Et^n* '^ Q-*^%eo, V-ta 



«HAP. IT. ATOMIC THEORY. 375 

luppens that these quantities saturate each other so far 
as the first stage of comhination is concerned. There 
18 nothing surprising in the fact^ that 60*071 grains 
should he the weight of exactly 200 cuhic inches of 
azote ; ^or that numher of grains has heen here assumed^ 
merely hecause it is the weight of 200 cuhic inches: 
any other numher of inches or grains would do as well^ 
except for the arithmetical convenience. But it is a 
very remarkahle fact, that 33*915 grains of oxygen — 
namely, the quantity required to saturate the 200 cuhic 
inches of azote — should he the weight of 100 cuhic 
inches of oxygen, or exactly half the volume of the 
azote ; for here could he no assumption of any certain 
nmnher of grains to answer a purpose — the weight, and 
therefore the volume, heing determined hy the affinity. 

This ha^ heen generally considered an ultimate fact ; 
— a truth of which no explanation can he given. But 
it is so ohviously and immediately connected with the 
atomic constitution of matter, which has heen of late 
years so fully developed, that the solution of it cannot 
much longer remain unattained. Indeed, some ingenious 
speculations as to the cause of it have long since heen 
advanced, hut they appear to he inapplicahle. I have 
often thought that an explanation of this ohscure part 
of the atomic hypothesis may he derived from another 
part, which has heen generally admitted. To explain my 
views, several considerations must first he adverted to. 

Two opinions have divided philosophers relative to 
the nature of caloric : according to some, it is matter ; 
according to others, it is motion of matter. Those who 
deny its materiality, rely much on the fact, that it seems 
destitute of gravity — the common attribute of all known 
matter. The argument does not strike me with much 
force. It is certain, that the nicest balance does not 
discover any real difierence between a cold body, and 
the same body heated. Weighing proves, perhaps 
nothing in this case. Hydrpgen is certainly matter^ 
and in large quantity is easily shovm. \o "^o^"8fe^'e»N?«\s^\ 
but in practice it is found a dif&cult^ to ^^\^ ^\Kts^ 

B B 4> 



1 vohime as ercn a cubic inch of it: the bakncelK- 
comes oveiload^, and its sensibility overpowered by tbi 
neighc of the containing appsratus, and its conntFt- 
poise. The same happens when heated bodies are 
weighed : there must be coniaining matter for d» 
caloric ; and the quantity of this matter must be un- 
(iderable, to contain a sufficient quantity of the alnic 
When we consider that the atati<^ experiments aUndel 
to, were not made in a vacuum, but in the air, it ii 
plain, that even if the caloric really possesseil a link 
weif^ht, it might not be discoverable. Most peopk 
conceive electricity to be matter : it can be made to per- 
forate a qtiire of paper ; it will strike into the eiitii, 
mnd make a deep hole ; it will split trees, and ihnw 

I down the most massive buildings. It is difficoll ts 
nnderstand how these eS^^ts can be brought about, an* 
s by a material agent : yet who doubts that elcctrid^ 
is destitute of weight? On the subject of matcei-* 
what it is, and what it is not, there is little UK IB 
Qwculation. We know that some eminent geuuH 
have even come to the conclusion that matter is nothingj 
— that it does not exist. Such a conclusion, if relied 
I, would render the explanation of all physical phe- 

I nomena exceedingly embarrassing. Taking the word, 
then, in its usual acceptation, 1 shall, in tlie following 
observations, assume caloric to he matter. 

If caloric be matter, it is probable thai it resemblei 
all other bodies, in possessing and being subject to thai 

Igpeciea of attraction called affinity. This opiiuon wb( 
maintained by Black, PicteE, Irvine, De Luc, Crawford, 
Lavoisier, La Place, and Thomson. Lavoisier says, that 
caloric is fixed in bodies by affinity, so as to form part 
of the substance, or even of the solidity, of the body. 
Dr. Black speaks in very remarkable terms .* — he says, 
" A particle of water a/tracts and tcnites with one or 
more aloms iff heat ; these atoms of heat are gel at iibertS 
bg/ the fixed laws of chemicoi aff,nity." — (^Lectures, 
. .m.) 
t This affinity has even \ieea meAe ««= »i^«». «^ ■* 



II 

I 

I 



cnay. tv, ATOMIC nraOBT. S?"^ 

culationbyAvogadro*^ and he has constructed a table, in 
which therelativeaffinity of various substances for caloric 
ifl expressed numerically, — the affinity of common air for 
beat being taken as unity. These numbers he deduced 
from the specific heat of gases, as given by Berard 
and Delaroche. 

We discover caloric entering into a state that seems 
to possess the characteristics of chemical combinadon ; 
for a decided change of properties is manifested. Ca- 
loric, when presented to ice, is absorbed ; the ice loses 
most of its properties as such, and becomes water, while 
the caloric loses its chief remarkable property of raising 
the temperature. The same observations apply to aU 
other cases in which heat becomes latent ; and other 
ilJuatrations of the position derived from specific heats 
might be adduced, did space permit. 

If there exist a reciprocal attraction between caloric 
and all other kinds of matter, why may not such an 
attraction be subject to the general laws of affinity? 
Why may we not suppose that the exertion of such 
affinity causes bodies to combine with caloric, atom to 
atom, and thus produces combinations bearing a deter- 
minate ratio to each other ? We are not in the habit 
of considering determinate ratios of heat, or atoms of 
it ; yet such may exist : and if experience prove that 
such an admission harmonises with, and leads to, the 
explanation of phenomena, which otherwise must stand 
in the situation of ultitnate facta, then we are bound to 
admit the notion as probable. It ia no more than an 
hypothesis ; but hypotheses are often the beacons of 
discovery : the atomic constitution of matter was an 
hypothesis in the hands of Higgins ; yet what depart- 
ment of the science has not since experienced iu bene- 
ficial influence ? 

There are some combinations of carbon with hydro- 
gen which may be here referred to, as illustrative of 
this part of the subject: they are gases ; and have been 
ilescHbed at page 1 70. of this volume. t\ie ftt*.''. ms^- 

• OloniflleiiiFiiiea.ilfc.U.tDtnQviM.B.l.. 



I 

I 



NHts of 3 volumes of carbon vapour, and 2 voluiDCSof 
byilroi^n, both conilensed into 1 volume ; the kcoeiI 
consists of 3 volumes of each, condensed into 1 ; and ihe 
third of 4 volumes of eiicb, condensed into 1. Here, 
then, are three different gasea containing the same ingie- 
dienta, in the same ratio, but in different quantities: IK 
have 4, (i, and 8 volumes respectively, condensed into I, 
but so far differing in their state from what would be dK 
resultof mechanical condenEation, that thejspontaneovtlf 
retain thecquahty of their respective volumes. Itiapnk 
habic that in each of these gasee, the compound ptrtidei 
consisting of carbon and hydrogen are at, and are nuiib ^ 
taiiieil at, different and determinate distances from etd , 
Other. Now the particles are at distances from eadi 
otlier, because tliey are kept so by interpo«efl calorie; 
and tliey are at ikterininate distances from each other, 
moBt probably because the quantities of caloric are de- 
terminate with which the compound particles of carbon 
and hydrogen are combined. If, from that gas whieb 
consists of 4 volumes condensed into 1 , we could reuow 
one dose of caloric, we should proluibty reduce it to ibe 
atate of the gas which contains 6 volumes in 1 ; uul 
were two doses removed, the resulting gas would, per- 
haps, be reduced to the state of the compound whicb 
COntainK 8 volumes in 1. In the same manner, were 
it possible to remove a determinate quantity of caloric 
from any gas, without further alteration in constitution, 
the result would, no doubt, be a permanent contractioo 
to a volume which would bear some simple ratio lo the 
original bulk. 

We have now to apply this hypothesis to the phe- 
nomenon proposed to be explained. The phenomenon 
itself may be briefly recapitulated as fallows : — Wlien 
bodies not gaseous, C and D, combine in definite ratios 
by weight, although the second, thin), fourth, Ike doses 
of D are all multiples of the lirst dose of D, the first 
dose of D is not a multiple or submultiple of the quan- 
tity of C which enters to\.o "Oae comXJvTa&aw. '^MJ.^ban 
two gases, A and B, cooAAm, cnto ■ibe few. **«» «A "S. 



eHAP. IV. ATOMIC T3E0RY^ 379 

bears a simple ratio to A^ being either equals oi double^ 
or triple, &c,, provided that volumes are considered; 
but if the quantities are estimated by weight, this pe- 
culiarity of the first dose disappears, and the law of 
multiple ratio is only observable in succeeding doses. 

To account for a coincidence of volumes so unex- 
pected, it was supposed, first by Avogadro, and after, 
wards by Ampere, that in all gases, simple or compound, 
the temperature and pressure being alike, the ultimate 
particles or atoms are at equal distances ; and that the 
number is the same in equal volumes of all gases, or, 
in other words, is in proportion to the volume.* Ac- 
cording to this view, the specific gravity of the gases 
would depend on the specific gravity of the atoms: 
other views might also be taken. Admitting this to be 
the constitution of gases, the explanation of the sin. 
gular ratio observed as regulating the first dose of B 
to A becomes easily intelligible. If 100 cubic inches 
of oxygen combine with 100 cubic inches of azote, to 
form one compound ; and with 200 of azote, to form 
another; it is plain that, as, according to the hypothesis, 
the number of ultimate particles or atoms is equal in 
equal volumes of all gases, each particle of oxygen must 
have combined with a particle of azote in the first in. 
stance, and with two of azote in the second. In short, 
granting the hypothesis, the phenomena naturally and 
consistently flow from it ; and the apparently myste- 
rious relation of the volume of the first dose of B to the 
volume of A, is in no way surprising; as the number of 
atoms is the ^ame in each, and they unite atom to atom. 
It appears to me, however, that the hypothesis is un. 
tenable on many accounts. We can no longer suppose 
that the number of atoms is the same in all gases, for 
we have instances of the contrary — at least, according 
to^ the evidence afforded by the analyses which have 
been made. The three varieties of carburetted hydrogen 
which contains respectively — 

♦ GiomtJe di rmca, dec il tomo vUU 1. Aima\e» Ae CWvmifc A«»»^^'>^ 



Variut; Isl, 2 Yols. i^umbmcil with 2 vols. 1 condensed 

— 2d, 3 vols. - . 3 Tols. I into I 

— 3il, 4 vols. - - 4 vols, J TDlumF, 

U expluneil in page 170, show that the number of kCohu 
In these three gases cannot be the same. From thu 
exception we may be ted to suspect that there are olhen, 
and to conclude diat the hypothesis is incompatible wilh 
ihe present state of knowleUge. 

The opinion relative to tile constitution of gases with 
Kgard to determinate ratios of caloric, which has been 
above EUg^sted, seems to harmonise tolerably well wiA 
the phenomena. If caloric be matter, it may be the 
subject of chemical attraction ; if it be chemically at- 
tracted, it may conibine in determinate ratios ; if it 
combine in determinate ratios, the gaseous compwmdi 
fbrmed must exist in determinate volumee. According 
to tbiB view, the abstraction of a dose of caloric from t 
gas, in which it had been chemically combined, would 
cause it permanently to contract to a half, or a third, or 
any aliquot part of its original bulk ; and the additioB 
of a dose of caloric would, when combined, cause it 
permanently to dilate to double, triple, or any multiple 
of its first volume. In short, if <^oric combine che. 
mically with the atoms of ditferent kinds of niKttei 
in determinate ratios, so as to form different gases, il 
would follow that, adopting as unity that gas wUcli 
contains the fewest atoms, the number of atoms it 
all other gases would be multiples of the tirst by an 

Were gases thus constituted, they should always unite 
in the ratio, not only of weight, but of volume, that is 
L observable in such cases ; and such a eonstitulion 
I would assign a sufficient reason for the relation of vo- 
^ hime which subsists between two gases when they enter 
into the first stage of combination ; — a relation which 
the hypothesis, thai a\\ ^iBse* lA 'tW sKcne fQUime, tem- 
perature, and piesBUte, wmxam ^i«: sameTOariaM tSv"- 



OBAP. IV. ATOMIC THEORY. 381 

ticles^ seemed to account for^ but which appears no longer 
tenable. * 

That^ under the same pressure and temperature^ equal 
volumes of all gases contain an equal number of par- 
ticles^ is opposed to the opinions of those who understand 
the atomic hypothesis^ as it flows from the general rule 
laid down by Mr. Dalton as a guide in investigations 
concerning chemical synthesis^ viz. that ^^ when two 
combinations are observed^ they must be presumed to be 
a binary and a ternary." There are two combinations 
of oxygen and hydrogen: water must, therefore, be 
binary j that is, in two volumes of hydrogen there must 
be as many atoms as there are in one volume of oxygen, 
which is irreconcileable to the hypothesis of .Avogadro 
and Ampere, although consistent with the views of Ber- 
zelius and Davy. 

The hypothesis of equal volumes of all gases contain- 
ing an equal number of atoms, fails also in another way; 
it assigns no reason for the remarkable contraction in a 
simple ratio to the original volume, which several gase- 
ous compounds undergo at the moment of their form- 
ation. It is necessary first to state the law, and to 
give a number of instances of this contraction ; the ob- 
jection may be then applied. Gay-Lussac, die disco- 
verer of the fact, says, ^^ Not only do gases combine in 
very simple proportions, but the apparent contraction of 
volume which they suffer by combination bears, also, a 
simple relation with the volume of the gases, or, rather, 
with that of one of them." 

When 1 volume of oxygen, and 1 of azote, com- 
bine to form deutoxide of azote, the result is 2 vo- 
lumes, as computation would indicate \ hence, there is 
no condensation. But when 1 volume of oxygen, and 
2 of azote, unite to form protoxide of azote, the re- 
sulting bulk is not 3 volumes, but 2 ; hence there 
is one third of the whole bulk lost by approximation of 
the constituent atoms. When 1 volume of azote and 
S of hydrogen unite, the ammomacai %«»ic$rK!kft\^<Q«^ 
not amount to 4 volumes^ "but ^; \«I\i S& xSckset^'tfste 



tolinnes of oxygen, and 4 rf 
da not afibrd 6 of protoidde of chlotine, 

Wr bate, IB Aort, rrdnctioiis from i voluma to I, 
3t»1, 4Ml,8lDl,aail9toI; and from Sto3, Sto!, 
TM3; and one af 6 to a. Il U obserrable, that aD the 
TOt^ae* coBcenKd, ImmIi Mmbining and resnltiDg, Bt 
wWe nnAoa ; fnrtioiiBl quantities never ocnuring in 

Aat, dnring oomhtnatioti, the partides of the gasea do 
OM renaio at the same lUstances, but approach ttA 
other a) «i bo present a resulting volume of the eon- 
pnood gaa which bears che shore mentioned ainiple ti6o 
to the sum of the two component gaaeB. We mij, 
therefore, express the law generally, by declaring, tbit >| 
when contraction does lake place, it is eo related, Ihil 
the same mut meosnres the volume that disappear!, the 
Vfllome of each of the gases which combine, and the 
vohune of the resulting compound gas. 

In explanation of this rate of contrat^tion, it raigbl 
he sapposed that either of the combining gases sarreo- 
ien its udoric, and merges its volume ; and snch u 
expUnatian mi^ht apply, if the resulting volume alwij* 
corresponded with either of the combining voluina. 
But tbii is only sometimes the case: ammoniacal gas, 
for instance, is formed from 1 volume of azote, anil 3 
vohimea of hydrogen ; the resulting bulk is 2 vohmies ; 
which would not be the case, had either the azote or 
hydrogen surrendered its gaseous existence. MTien the 
■tOQiB'Of azote and hydrogen combine, the atoms of 
ammonia formed, retain the quantity of heal proper to 
diemselves: but the singular fact, that the quantity of 
h^ retained is just sufficient to enable the newlj 
formed gaa to occupy a volume, bearing the ratio to the 
original gases already stated, remains unexplained, un- 
leaa the existence of definite ratios of combined hrat be 
admitted. 

/ have not been detenei ?ioto »6sravco\^ -iaiHR t»- 
Uoai, vague u tlies at ^leaeal we, QT>^ iu»<»m\ <A wj 



CHAP. IVr ATOMIO THEORY* , 585 

considerations derived from the specific heats of gases^ 
suspecting that we have as yet no certain knowledge 
of that subject : it is not even agreed whether they are 
the same in all^ or different for each : and when we find 
the experiments of Delaroche and Berard diametrically 
conflicting with those of Marcet and Delarive^ it seems 
but prudent to abstain from coming to any conclusion 
on the subject. 

There is a consideration . relative to Gay-Lussac's 
discovery of the law of volumes, which seems not to 
have been attended to by chemists. The law has been 
conceived to consist of two distinct positions : first, that 
gases combine 1 volume with 1 volume, or 1 with 2, 
or 1 with 3; second, that when contraction follows 
combination, the resulting volume ^^ bears also a simple 
relation with the volume of the gases, or rather with 
that of one of them," as it is expressed by Gay-Lussac. 
Does not the second position flow from the first ? and 
do not both indicate parts of the same phenomenon ? 
Two volumes of muriatic acid gas saturate 2 volumes of 
gaseous ammonia ; and 2 volumes of ammonia consist 
of 3 volumes of hydrogen, and 1 volume of azote. If 
the 3 volumes of hydrogen and 1 of azote did not con. 
dense into exactly 2 volumes of ammonia, but occupied 
the bulk of suppose 2^ volumes, then the first position 
of the law could not be fulfilled in the combination of 
2^ volumes of ammonia with 2 of muriatic add gas. 
The same kind of observation applies to the 2 volumes 
of muriatic acid gas composed of 1 volume of hydrogen 
combined with 1 of chlorine. Again, if oxygen, in 
being converted into carbonic acid, suffered the slightest 
expansion or contraction, the law of volumes could not 
be obeyed in the saturation of 1 volume of carbonic acid 
by 2 of ammonia. Were any expansion or contraction 
to take place in the generation of carbonic acid, it 
should be at least in such a ratio as would permit a 
multiple combination with aU other gases. 

Id the foregoing pages of this c\i«^\et,\\.\vas^\jR«Ck. 
MbowDj as fully as the small space vfYsidi ca5i\» ^Q»N^fc^ 



fSB* 

to the sub.iect would permit, tfaat mattler coinliiiKs 
chemically with matter in limited quantities,' thalvrilfain 
the limit there frequently are delermiaate and succcnivt 
stages of combination, in each iif which the ponderaUe 
quantities giving origin to the successive stages tie 
equal I that this equality of ponderable quantitieB ii 
observable in solids and in gases ; and that, in the (Me 
of gases, it is observable as well when the quantitiet 
are determined by volume. It now only reraaina to n- 
certain the amount or value of the combining quantiliGB. 
AfGnity is a property of all matter : it acta in ntcb 
a manner between two bodies, that, when they combine, 
they do so in quantities whicli are constant for the Eune 
bodies ; and this is the case, whether there is one com- 
bination or more. Forty parts of sulphuric acid Batunle 
32 parts of soda ; and the same quantity of acid satorata 
S8 of lime. These quantities of soda and lime are then 
so far related, that each is the Tepresentative of the 
other, with regard to the power of saturating 40 parti 
of sulphuric acid. The question occurs, is the acidity 
of sulphuric acid such that the ratio of the alkaline 
bodies to each other exists with regard to saturating tl 
only ? or, is acidity a general property, the same in al! 
acids, so far as the ratio of the alkaline bodies adequate 
to flaturate it is concerned ? T]ie latter form of the 
question must be answered in the affirmative. We find 
that the above mentioned quantities of the two alkaline 
bodies agree in the property of being saturated by 5i 
at nitric acid. Thus, a remarkable relation subsists be- 
> tween these quantities of the four substances concerned : 
I 40 parts of sulphuric acid act the same part as 54 of 
nitric acid, in saturating 32 parts of soda, or 28 of 
lime: they are all equivalents (as they are now pretty 
generally called) to each other in saturating power: 
they are the combining veights of these substance! : 
Ihey are the repre^titatii:e niimben, from which we 
'^ learn the ratio of the quantities that saturate each 

We learn from 1.^11% tb.i:vs, &»X \S "Xh -^sna 

0-/-52) of sulpliate oS ao4a,»n4-%'i"?'»W8- V?^■^■'^-'S^ 




V. ATOMIC THEORY. 3S5 

ite of lime were, mixed^ the known order of 
3 would prevail^ and a total decomposition would 
the 40 parts of sulphuric add, which had heen 
d hy 32 of soda, would now he equally saturated 
f lime; that is, the equivalent of 32 of soda; and 
s of sulphate of lime, would he formed : and the 
s of soda, now liberated, must be saturated by 5^ 
I acid; the latter being the equivalent of 40 parts 
huric acid, which had formerly saturated the 
Thus, the result of the decomposition would be 
s of sulphate of lime, and 86 parts of nitrate of 
md there would be neither free alkali nor free 
be found in the mixture. - 
3d, in all such double decompositiouB, if the 

salts were neutral, so will the resulting salts, 
n a few cases of compHcated affinity which need 
I be specified : and it cannot be otherwise. For 
;, consisting of an acid. A, and an alkali, B, be 

it is so because A saturates B : if, then, that 
decomposed by another, consisting of an add, C, 
iarth, D, the acid C being just suffident to satu. 
which had been previously saturated exactly by 
A and C are equivalents ; and it is nothing sur- 
that A should saturate D, which had been pre- 
saturated by C. Neutrality must result : the 
s may, perhaps, not totally decompose each other • 
result of any decomposition that does take place 
neutrality. 

nay extend the number of the four equivalents 
lentioned, throughout the whole catalogue of the 
t bodies in nature. Whatever quantity of pot- 
irates 40 of sulphuric add, will be the equivalent 
arts of soda, and of 28 of Ume ; and will be sa- 
as well by 54 of nitric add : this quantity of 
is 48 parts. Whatever quantity of carbonic 
urates 48 of potash, or 32 of soda, or 28 of 
ill equal the saturating power of 40 parts of sul. 
jcidf, or 54 of nitric add : IMb qy\axi^\7] oil ^'wt- 
id 18 22 parts. Or, it ^inll \)e iwjiw^, ^3s»X ^a 

c 



see 

parts of oxide of anc nil] saturate 40 puts of 
acid, and, coD^equendy, i^l' of nitric acid, and £i ol 
carbonic; and to these, or any other acids, it iriUte 
equivalent in saturating pover to 33 of soda, 26 of line, 
and 4S of poush. Thete observatiotw have pwsenlri 
HE with the following scale of etjuivakntE, the duh 
representing the bodies to be combined, and the nim- 
bera showing the qaantitieB in grains, pounds, or K<ii>> 
Di any other denominations, which satnrale each nOta, 
in such cases as comtunations actually lake place: — 
I Sulphuric acid 40: nitric acid Si: carbonic add SSi 

oxide of zinc 42 : potash 48 : soda 32 : lime SS. 
' Now. as all these bodies are compound, and are eqvU 
Talents to each other, it would follow, as a consequeiw, 
that the elements of which they are composed an )1m 
equivalents to each other in relative quantity ; and ibil- 
in the case of any two of these bodies — sulphate of sic. 
for instance — we are not merely to conmder tbatsaltn 
composed of sulphuric add and oxide of zinc, in a kt- 
ttun ratio to each other, but as composed of suIpburK 
acid, zinc, and oxygen. The i2 parts of oxide of ti>K 
consist of 34 parts of zinc and 8 of oxygen: camt- 
quently, 34 is the equivalent number for zinc,tiidS 
for oxygen. If we examine potash, soda, and linWi ■■< 
the same manner, we should, of course, find 8 coiutultlj 
the equivalent for oxygen : thus, 48 parts (ibe eqmT*- 
lent) of potash consist of 40 parts of potassium and 8 
of oxygen : 32 parts (the equivalent) of soda cowost nl 
24 sodium and 8 oxygen : and 28 parts (theequivdenl) 
of lime consist of 20 calcium and 8 oxygen. Thus «* 
have obtained the following additional equivaleoU:— 
Oxygen 8; zinc 34; potasdum 40; sodiuin 24; t^ 
ciura 20. 

But the acids above enumerated are also eotnpoundi> 
they consist of oxygen and a base ; it is, therefore, ik- 
cessary to discover if the oxygen is the same in tliem " 
in the substances just examined. Sulphuric acid, in tf 
parts (ita equivaitint"^, con^:maa\ft oS fN^^V\n.,*ad » 
much as 24 paita o£ ox^aen.-. m-avo »cui,\M. bV^f* 



rCHAF* IT. 



ATOttIO THEORT. 



387 



(its ^uiyalent)^ contains 14 of azote^ and 40 parts of 
oxygen : and carbonic acid^ in 22 parts (its equivalent)^ 
contains 6 of carbon and l6 of oxygen. In these acids^ 
we^ therefore^ have the oxygen as 24^ 40, and l6 ; and 
in the former estimate we have it 8. But as 8 is the 
quantity which exists in oxide of zinc^ potash^ soda^ and 
lime ; and as 24 is three* times 8^ and as 40 is five times 
S, and l6 is twice 8^ it is evident that 8 is the real 
equivalent number ; that in sulphuric acid there are 3 
doses of oxygen^ in nitric acid 5, and in carbonic acid 2. 
These analyses afford the following additions to the list 
of eqnivalents^ the numbers being foimd by subtracting 
the oxygen in each case: sulphur l6; azote; car- 
bon 6. 

In water the oxygen is 8 parts^ the hydrogen 1 
part^ both by weight : 8 being the equivalent of oxygen^ 
.1 is the equivalent of hydrogen. The following table 
presents all these bodies^ with their respective num. 
bers: — 



Hydrogen 


1 


Lime 


28 


Carbon 


6 


Sodff - 


32 


Oxygen - 


8 


Zinc 


34 


Azote - 


14 


Sulphuric acid 


40 


Sulphur 


16 


Potassium 


40 


Calcium . 


20 


Oxide of zinc - 


42 


Carbonic acid 


22 


Potash 


48 


Sodium 


24 


Nitric acid 


54 



And we may easily find the equivalents of any of the 
compounds of them by adding the numbers together : 
thus water will be 8 + 1 = 9; nitrate of lime will be 
54 + 28 = 82, &c. The value and meaning of this table 
will be more fully seen in the following observations: — 
The numbers representing the equivalents in the 
table, may be increased or diminished to any extent : hy- 
drogen, instead of being 1, may be represented by the 
number 100, or by 1000, or 999^ or any other num. 
ber, provided that all the other numbers ate tavi^^^^,^ 
fa an equal ratio. Or hydrogen ma^ \)e leipte^wvNfc^ Vj 

c G ^ 



I 

I 



tTi\-n <"■ -mhrm, if all Ae other numbers are eip»ij 
diminiahed. If hydrogen »t-re 100, oxygen wduU be 
800, nitric acid 5400. Were hydrt^en 0-01, di^ 
would be 0'08, and nitric acid 0'54; — nowbHS ill 
equally inconvenient either to write or to speak. Itic 
Ihe ratio that renders them of value : the table iafMn> 
lis, that 40 parts of Bulpliuric acid would saturate iS d 
potash ; but there is nothing useful in the numben W 
and 48 more than in 20 and St, or 5 and 6 : it is lltf 
ratio of the sulphuric acid to the potash which we tt 
quire to know, and of which we are informed hj ih 
table. Every one knows that the larger the numbnsii 
any series are, the more difficult it becomes to percdn 
their relation. Thus the relation of the numbersin V 
progreeeion 1, S, 3, 4, 5, Scc. is obvious on inapeetio 
but it would not be so were we U> exprcGS the sutui 
Jatioii by the numbers 129, 258, 387, 5l6, 6*5, t 
Hence, it has been an object to reduce the equiviloil 
numbers to the lowest ratio that can be obtained. 

But, the ratio being the main object of the scale of 
equivalents, it may be enquired, why are not the niunbH! 
reduced far tielow what are given above ? for the B»le, 
if extended so as to include all known bodies, will p" 
numbers higher than 500. To understand the answer 
to this queetion, we must first consider the nature mmI 
conGlitution of numbers in general, so far as is necH- 
sary to a clear comprehension of the nature and asu^' 
tution of the numhers which represent chemical elBI- 
valents. 

Euclid (leflnes number lo be a multitude of vwl'- 
Mr. Locke observes, " Amongst all the ideas we h*rc, 
as there is none suggested to the mind by more v*p, 
BO tliere is none more simple, than that of unilg or !• 
It bad no shadow of variety or composition in it: eieij 
object our senses are employed about, every idea in tmt 
understandings, every thought of our minds, biingi tla* 
idea along with il." — " B-j relating this idea (wati) 
in our minds, and aAftin?, 'te TtijSii.'a.aBa ing^ss-. 
■^o have the comples. idea o? a- tiiffiia^i, ot Bt\*Sw» 



CHAP. IV. ATOMIC THEORY. S89 

number." £iiler defines number to be '^ tbe proportion 
of one magnitude to another arbitrarily assumed as the 
unit." In shorty we can have no idea of any number, 
but in reference to some standard which measures that 
number ; and that standard is 1, or unity. In its own 
nature unity is not a nrnnber, and, therefore, it is indi. 
visible: for, even though it should really consist of 
parts, '' it has no shadow of composition in it," and it 
is " arbitrarily assumed" to be one. Such is the nature 
of the unit of number ; and this nature wiU now be 
shown to correspond with the unit of the table ill 
question. 

On inspecting the table of equivalents, we learn that, 
to form potash, 40 parts of potassium must combine 
with 8 of oxygen. The table gives tiie quantity, but 
not the quality, of tiie relative weights: it does not 
declare whether the weights are grains, ounces, or 
pounds. In practice, it may be any of them; in 
general, it may he parts j but, in the tiieory and con- 
struction of the table, a very diflferent denomination* 
from any palpable weight, is implied. When we con- 
sider the numbers concerned, viz. 40 and 8, they convey 
no idea, unless they refer to the unit, or measure, of all 
the rest : forty times something else, and eight times 
the same, are both implied by the numbers. The 
measure expressed in the table is hydrogen ; it is called 
1, and is therefore the unit. This affords tiie reason 
why the numbers in tiie table are so high : they aU refer 
to hydrogen as unity ; and hydrogen enters into com- 
bination in very small quantities, partly owing to its 
lightness compared with its bulk, and partiy to its great 
saturating power. For instance, tiie weight of hydrogen 
tiiat combines to form ammonia, is almost five times less 
tiian that of the azote: tiie weight of hydrogen, in 
sulphuretted hydrogen, is only -y^th ; and, in hydriodic 
acid, it is but -j^^th. It is obvious, tiiat the less the 
weight of hydrogen is, which combines witii other bodies, 
tbe greater must he the weight of \ko^ \»^%:e» ^«^^ 

cc 3 



«i 



I 

I 



I 



combine with it : for ll)e terms more and leu IR 

The nMeesttjr of an unit hoTii^ been thus poiiited 
out, the next enquiry ia, concerning the denominatiantif 
which this portimlar unit is, m it is not the meaEureof 
any p»lp«ble wdght known in practice. The most in- 
t^igible mode of introducing the Eubject, will he HI 
.(lotftil llie circumstances which led to the idea of em- 
ploying equivalent numbers. Mr. Balton was the fini 
who distinctly conceived that, from the relative wriglui 
(tf the elements in the mass of any compound bodft 
the relaliTc weights of the ujlimate partdclea or ilMM 
of the bodies may be inferred : and that, from d^ 
dwir number and weight, in various other compoDtid^ 
would appear in such a way as to assist and guide fittuK 
inveitigations, and to correct the rcEutia. He inferred dw 
lelative weights of the atoms in the foUowing manner;— 
Water, he conceiveil to consist of 1 part, by weight, of 
hydrogen, and 7 of oxygen. It must be presumed, he 
thinks that, when two combinations of two bodies on 
be obtained, the first must be composed of an atom of 
each combined ; and the second, of 9 atoms of one, and 
1 atom of the other. .Applying this rule to the two 
comMnations of oxygen and hydrogen, we must suppose 
that water consists of an atom of hydrogen comhiaed 
with an atom of oxygen : and, if this be admitted, the 
weights of the atoms must be in the same ratio as the 
weights of the total quantities that compose water. Ueaee, 
an atom of hydrogen will weigh 1, and the atom of 
oxygen will weigh ?■ Ammonia, Mr. Dalton conceited, 
to consist of I part of hydrogen, combined with nearly 5 
of aiote ; and, as he considered ammonia as composed 
of an atom of each element, there being but one known 
combination of hydrogen and azote, the weight of the 
atom of hydrogen is 1 as before, and that of the atom 
qf azote is about 5. Carbonic oside, consisting of 
oxygen and caifaon in nearly the ratio of 7 to 5, and 
'eing composed of an atom o^ea^(^c«\s;w,,'iie»wiwio( 
will weiKh 7 as \MSoTe, aai liie aiftia tS. >adsM 



^OAP^'Vn ATOMIC THJBORT. 391 

about 5 : and the weight of an atom of carbonic oxide 
wiU be 7 + 5 = 12.* 

In this way he proceeded to examine many compounds^ 
ISrst assoming the weight of an atom of hydrogen to be 
unity^ and^ from that^ determining the weight of the 
atoms of other elements^ by representing them as so many 
times heavier than the atom of hydrogen — the number of 
times being discovered by comparison of the weights of 
the different elements. These weights were determined 
by analysis of the compound formed either with one part 
of hydrogen^ or with a given weight of some other 
element^ the relation of the atomic weight of which to 
that of hydrogen had been already ascertained. Thus^ 
the weight of the atoms of other bodies were expressed in 
atoms of hydrogen^ each of which was denoted by unity. 
' The reason for adopting hydrogen as unity, is, be- 
cause that body, of all others, enters into combination 
in the smallest weights : hence Mr. Dalton considered 
hydrogen to be the most proper unit. We now see that 
this unit is an atom ; and that an atom corresponds 
with the simple and indivisible nature of an unit : for an 
atcnui without a contradiction in terms, can have no parts. 
It will be useful to reconsider a few of the equivalents 
in tlie table already given, and to show in what manner 
these mimbers have been derived, so different as they 
are from the numbers originally given by Dalton. Water 
is now known to be a compound of 1 part of hydrogen 
and 8 of oxygen, both by weight. It is conceived that, 
in water, the two gases are combined, atom to atom ; 
which is the same as to say, that there 'are as many 
atoms in 1 part, by weight, of hydrogen, as in 8 of 
oxygen : and, if this be so, it is quite clear, that, as-^ 
suming the atom of hydrogen as 1, for the reasons 
already assigned, the atom of oxygen must be 8 times 
heavier. Hence, in the table, hydrogen is called 1, and 
oxygen 8. But no assertion is made further than regards 
the ratio of their weights : nothing is conveyed as to th<l i 

•All these atomic weights, given by MT.'D«\toTi,Yivi«>ae«a ^SiX^t^x^ . 
^nwegiieoce o/«iilwequ«nt investigations. 

C 4i 



I 



I 



^^B^7 CO] 



actual number of puticleij of either oxygen or hydioga 
contained in a given weight of these gases. 

Again: olefiant gas is composed of equal vohuaes rf 
hydrogen and carbon vapour, 100 cubic inches of 
esrbot) vapour weigh 12-6S'2 grdns, and the asiH 
volume of hydrogen, 2-1 107 ; Ibftt is, a volume of CM- 
bon Tftpour weighs 6 times (711. pT.) more than an eqnil 
volume of hydrogen. If it be assumed, that theie t« 
gases unite atom to atom, it is quite clear that, withont 
asserting any thing as to the number of the atomi ID 
any volume of these gases, we may conclude, the ttoo 
of carbon is 6 times heavier tlian that of hydiagWi 
hence, the latter being 1, tlie former is rated 6 in 
the table. 

The same atomic weight may be derived Id ano^ 
way. Carbonic oxide consists of 33'9I53 parli of 
oxygen, and 35-364 of carbon, both by weight : that is, 
the weight of the oxygen is to that of the carbon, u 
1*3371 to 1. Now, as it is Bssumed that the oxygen 
and carbon combine atom to atom, it is plain, that tlie 
atom of the former will be to the atom of the latter, in 
weight, as 1-3371 to 1. But the atom of oxygen Im 
already been shown to weigh 8: therefore, as 1'3371 is 
to 1, so will 8 be to 6 {qu. jur.) ; and thua ^;ain we 
obtain 6 as the atomic weight of carbon. Here it i« 
to be observed, that the atomic weight of carbon has 
been obtained, appareiilly, without reference lo that of 
hydrogen. But it has been compared with the atom of 
oxygen, and that was originally obtained by compariaon 
with the atom of hydrogen. The atomic weight of 
barbon is, therefore, in directly, derived from a cojnpariwin 
with that of hydrogen. 

We may also infer the atomic weight of carbon 
from marsh gas and carbonic acid, with instructive re- 
sults, Marah gas consists of carbon 12-()8'2 parts, and 
hydrogen 4*239, the ratio being very nearly as 3 to 1. 
When these quantvtits unite, it cannot be supposed that 

!j combine atom to atom -, ioi xWx -wis. 'Owt m^-^ 
the fonnttdoTi oi okftaiA ^aa. TWVitewffa 



CHAP. tV, ATOMIC THEORY. SQ3 

is now double the weight ; hence its atoms are double 
the number : and as the weight of the carbon is to that 
of ibe hydrogen^ in the case of marsh gas^ as 3 to 1^ and 
as in the 1 of hydrogen there must be two atoms^.the 
real weight of carbon is as 6 to 1 ; that is^ the atomic 
weight of carbon is again found to be 6. 

Carbonic acid consists of 33*9153 parts of oxygen 
and 12*682 of carbon ; the former is to the latter as 
2*674» to 1 . But the volume of oxygen in carbonic 
acid is twice as great as it is in carbonic oxide ; so also 
must be the number of atoms. Hence^ the ratio of 
weights being as 2*674 to 1^ and the former number 
representing 2 atoms of oxygen, we have the proportion 
2*674 : 1 : : l6 : 6 (qu.pr,). 

The atom of azote is deduced from the composition 
of protoxide of azote. To form this, 33-Q153 parts of 
oxygen combine with 60*071 parts of azote ; hence the 
azote is to the oxygen as 1*771 to 1 : and as the atomic 
weight of oxygen has been already proved to be 8, and 
the two elements combine atom to atom, we have 
1 : 1*771 :: 8 ; 14 (^w-pr.). Hence the atomic weight 
of azote is 14. 

The weight of the atom of sulphur may be derived 
from sulphuretted hydrogen, which consists of 2*1197 
parts by weight of hydrogen, and 34*2 of sulphur. The 
weight of the sulphur is, therefore, to that of the hydro- 
gen, almost exactly as 1 6 to 1. Hydrogen being unity, 
the atomic weight of sulphur is l6. 

From these examples it appears, that the atomic 
weights are all derived, directly or indirectly, from hy- 
drogen assumed as unity : and as the unit in the table 
of equivalents is an atom, so also the equivalent num- 
bers are multiplications of that atom. It is, therefore, 
manifest, that nothing is known of the real weight of 
an atom in any ponderable or practical denomination, 
such as grains, &c. An atom must certainly possess 
physical weight, be it ever so minute ; but as it is totally 
inappreciable^ we are utterly ignoTant oi \\.. \\. ^'sk^ 
fore foUowB, that the numbeis in the Xa^^^ ol ^ojfxiH^*^ 



• 



■ixMBtm ov c 

lenta ilo not reallj tepreEent poaderable qiuuili&i, 
>lth<)U}!;h they iDsy be used as such. They merely is 
preEentratioBof weights, and not the weighia thentMini. 
M^en it is said that the atcm of catbon » 6, iti*iiu 
tended to affirm that itB aU>m is six tiron heavier tbta 
the Btom of hydrogen, aesuining the latter ailHtntily 
M a BtaniUrd of compariEon, and not profeEsng n 
understand tile value of that standard. Id the aae 
manner, we eay that tlie atom of oxygen is 8 timei 
heavier than that of hydrogen; and hence («ddiiig8 
to ti), that the atom of carbonic oxide is 14 liawi 
heavier than the atom of hydragen. 

Itut we must also view these numben undci 
another aspect. If they represent the conpin- 
live weights of atoms, and if bodies combine atom js 
atom, these numbers must, as already stated, lepicsat 
the ratio in which bodies combine and satumte (Mil i| 
other; hence the name combining vreighf, ^veDtalhen 
by Dr. Young. Thus, if IC repreient an atom of Nil* I 
phur, and 1 an atom of hydrogen ; and if Hulphnr »d 'I 
hydrogen unite atom to atain, then l6 parts (whelhcf 
grains or pounds) ought to saturate 1 part of hydnfnii 
and thus form 1 7 parts of siUphuretted hydrogen ; and 
die number 17 should also be the atomic weight and 
combining quantity of that gas. This is true ; for m 
find that 17 parts of sulphuretted hydrogen enter into 
combination with ^6 of sulphuret of potassium. Thia 
latt number is the atomic weight of sulphuret of p»> 
taasium — it being composed of an atomof sulphur=l6, 
«nd an atom of potassium = 40. It is in this way 
• that the table of equivalents becomes of such vast im- 
portance to the practical chemist, especially when lud 
down on a scale with a slider, as in WoUaston's scale o( 
equivalents, which even performs arithmetical operations 
on compositions and decompositions. 

On inspection of the table of equivalents above giTe% 
it will befound,that theuumbersare all multiples of the 
weight of hydrogen, atii <bttV, o^ toa'Rfc, -aa ^^nConoil. 
lumbers occur. Inileei, ^ive aawiE oW^d'aow wj^os* 



IHAP. TV* ATOMIC THEORY. $95 

o the equivalent numbers of all the bodies known^ with 
>ut very few exceptions. The singular circumstance, 
hat the first adopted unit * should exactly measure the 
itoms of all the substances which were afterwards re- 
iuced under the law of multiple ratios^ might be ex- 
plained by supposing that the atom of hydrogen is the 
natural and real unit of all matter ; or^ more probably, 
that fractions have been removed by the corrections 
made in the analysis of bodies^ according to a practice 
DOW almost invariably adopted and allowed by chemists^ 
N^otwithstanding this coincidence^ it has been considered 
by the majority of good judges, that there are countervail:, 
ing advantages in assuming oxygen as unity, in place of 
representing it by the number 8. If oxygen be con- 
sidered 1, we must then reduce the whole scale of 
equivalent numbers to -^th of what they would be were 
[lydrogen 1. Thus, sulphuric acid, which in the table 
is 40, would then be 5 ; and nitric acid, instead of 
[)eing 54, would be 6*75 : lime, instead of 28 would 
ye 3'5 : carbonic acid, from 22, would change to 2*75 ; 
md hydrogen would be 0*125. In this case, almost one 
iialf of all the ascertained numbers would be fractional ; 
}ut they are almost always those fractions which are 
easily remembered, such as ^ = 0*25, or ^ = 0*5, or 
If = 0*75. Dr. Thomson, in advocating the oxygen 
scale, says, ^' Surely it will not be said that the frac- 
ional numbers are more unwieldy or unmanageable 
han the whole numbers ; while, in all cases of whole 
lumbers, the advantage on the side of the latter method 
s very great. Thus, if hydrogen be unity, the atom of 
iranium is 208 ; while, if oxygen be unity, it is only 
16.** — {First Princ A. 17') On the other hand. Dr. 
Jre observes, ^' It has been objected by some, to our 
issuming hydrogen as the unit, that the numbers re- 
presenting the metals would become inconveniently 
arge. But this could never be urged by any one ac- 
[uainted with the theory of numbers. For in what 
espect is it more convenient to xecVoii \i«d\rcci ^^'^^ ^^, 
* Hydrogen was the unit chosen \yj ^.'D^Voxv. 






tomic scale, or 8-75 x 16=140 on sirH.Dsvj'i 

■cale of eTperimcnt ? Or is it any ailvactage ta nuiK, 
with Dr. ThomBon, tin = 7375, or to all it US OB 
die plan of the English philosopher f If the rom- 
bining ratios of all bodies be multiples of liyttrogeii, ti 
is probable, why not take hydrogen as the unit." It 
■ppears to roe that the oxygen scale of numbers, con" 
mdered with regard to numerical convenience only, hu 
little or no advantage over the hydrogen scale. In 
writing, speaking, or thinking, the three figures, 8^^5, 
fleem to have no advantage over the other three figure*, 
140 ; and there are many such instances. Dr. Thomaoa 
Msigns, also, the following reason for preferrii^ oxygen 
sa unity : — " Hydrogen, so far as we know at present, 
combines with but few of the other simple bodies; 
while oxygen unites with them all, and often in vaiions 
proportions. Consequently, very little advantage ia 
gained by representing the atom of hydrogen by 00101, 
hut a very great one by representing the atom of oxygen 
by unity: for it reduces the greater number of arith- 
fttetical operatione, respecting these bodies, to the ad- 
dition of unity ; and we see at once, by a glance of dit 
bye, the number of atoms of oxygen which enter into 
COmbinatiDn with the various bodies," This argument 
seems to me unanswerable. In the appendix to Dr. 
Thomson's System of Chemistry, recently :pnbUshed, 
there is a list of 390 bodies, the atoms of which ate 
represented by numbers composed in aU of 1026 digits 
for the oxygen scale, and 800 for the hydrogen scale. 
Thus, on an average, the number of digits employed fijr 
each body, according to the two scales, is as 1 -3 1 to 1 f 
a trifling disadvantage, compared with the great utility 
of subtracting, adding, or remembering the dose ot 
oxygen belonging to a body by means of unity, and 
many other important substances by numbers not very 
much greater. 
£ither of the Bca\c« wi^ aTvawcT the purpose. In 
convert llie ^i^iso^e^ «^'»^ ™-'^ ^"^ oi^ye*' 



CHAP. IV. ATOMIC THEOBY. 397 

scale, divide the former by 8. If the oxygen scale be 
multiplied by 8, the product will be the hydrogen scale. 
It is now necessary to show, that the numbers them- 
selves, considered abstractedly as representatives of the 
weights of atoms, and without reference to their capa- 
city of expressing combining ratios, are hypothetical 
and useless ; and that they may be, in reality, very dif-. 
feretit from what we suppose them. As there are but 
two imits employed, oxygen and hydrogen; and as both 
of these are contained in water, the composition of 
which is agreed on by all chemists ; the analysis of 
water may be considered as the basis of the atomic 
hypothesis. Water consists of 1 part of hydrogen and 
8 of oxygen, both by weight; or, what is the same 
thing, 2 volumes of the former and 1 of the latter* 
It is inferred, that in the 2 volumes of hydrogen there 
are exactly the same number of ultimate particles, or 
atoms, as there are in 1 volume of oxygen. But there 
are no grounds for the inference, beyond a supposed 
probability. It originated with Mr. Dalton, and was 
expressed in the following words : — ^^ When only one 
combination of two bodies can be obtained, it must be 
presumed to be a binary * one, unless some cause appear 
to the contrary : and when two combinations are ob- 
served, they must be presumed to be a binary and ar 
ternary." f Water is, therefore, inferred to consist of an 
atom of hydrogen combined with an atom of oxygen. It 
is further inferred, that a given volume of hydrogen con- 
tains but half the number of atoms contained in the same 
volume of oxygen : and as the weight of oxygen in wa- 
ter is 8 times greater than that of hydrogen, the atom of 
oxygen is inferred to be 8 times heavier than that of 
hydrogen. The truth of the fact inferred, however,, 
depends on the truth of the assumption, that the two 
gases uiiite atom to atom ; — a position which may be 
either denied or admitted at pleasure, for it is perfectly 
gratuitous. It may be affirmed, as equally probable, 

, * Mr. Dalton explains a binary compound to xoeaxi vcv «.\xnsL^t «»«2cw <a>^ 
ment in. combination, 
f A ternary compound is 1 atom combined m\i3ciSt «XA\n&. 



BLBHtlNTS OP OBEMIBTBT. 




that a Toltime of hydragen consiets of the si 
of atomsas avolume of oxygen. In thiE i 
of an atom of oxygen will be IR dmea heavier than on 
stoni of hydrogeo ; and then, if oxygen be aaEumed u 
1, an atom of hydrogen will weigh 0'0625, instead of iM 
double, 0'19a ; or, if hydrogen be ^ I, the atom of 
oxygen will weigh 16, instead of S^ and all the nomben 
in the table of equivalents must be doubled. In short, 
ta we know notliing of the number or weight of atomi 
constituting hydrogen or oxygen gas, all numbers pro- 
duced by mnllipUctttion of the atom of either raaat be 
ooi^eetural, and only valuable so far as they express 
ratios to an unit assumed at pleasure. 

Another instance of the fallacy of the general nile, 
that when two compounds are known, one is to be pre- 
sumed lobe binary and the other ternary, may serve to 
Bet this matter in a proper point of view. If hydrogcB 
be = I, oxygen will be = S. Analysis shows that about 
8 parts of oxygen combine with 200 of mercury to form 
the protoxide, and 100 to form the peroxide. If we 
take S as one atom of oxygen, and if, according to the 
rule, as there are two combinations, the protoxide is 
binai^,- then the atom 8 will unite to an atom of mer. 
cury, which, consequently, will be represented by 200. 
The atom of mercury has been hitherto, accordingljr, 
rated at SOO in hydrogen tables of equivalents, and at 
35 in oxygen tables. But we may just as well suppose 
that the protoxide consists of an atom of oxygen com- 
Inned with 2 atoms of mercury; and then the number 
representing mercury is reduced to one half, that is, 
100 or 13-5, This view has been adopted by Dr. 
Thomson, in the last edition of his System of Chemistry, 
ftr reasons which he has there stated, and which, when- 
ever they will be founded on «n extensive induction, 
will be of the utmost value in determining the real 
atomic numbers. In his Introduction, p. xiii., speaking 
of the tables of atomic we\^^, he 64^8, " It is not 
unlikely that some ai livese nMnCa«'i iaKi\ie \™wfe u 
, high as they ought W \«." l^^S '■'^ --^-V. ™.™- 



CKAP. IT. ATOMIC THEORY. 399 

the xeal condition of the atomic numhers in the follow- 
ing : -— ^^ In many cases it is not easy to fix upon the 
true atomic weight of a hody. We can always infer 
that the weight of one hody that enters into combination 
with another^ either denotes the atomic weight of the 
body, or at least a multiple or suhmultiple of that 
weight ; hut in some cases it may he very difficult to 
determine which of the three." 

These statements hold true, whether we take oxygen 
or hydrogen as unity ; and whether we admit the ex. 
i^tence of atoms, or not. It has been supposed by some, 
that the doctrine of determinate proportions is a mere 
expression of facts, and essentially different from the 
atomic hypothesis, which is founded on the assumption 
of the finite divisibility of matter ; or, in other words, 
on the atomic constitution of bodies. It appears to me, 
that there is as much hypothesis in one doctrine as in 
t}ie other. We say that an indivisible atom of hydro- 
gen = 1, combines with an indivisible atom of oxygen 
= 8 ; and the latter combines with an indivisible atom 
of mercury = 200. Here, it may be said, are three 
gratuitous assumptions : first, that the combining quan- 
tities are atoms ; secondly, that they are indivisible ; 
and, thirdly, that the bodies combine atom to atom. 
But in the doctrine which professes to embody facts 
only, we can detect these same three assumptions tacitiy 
involved. According to this mode of expressing the 
phenomena, a certain quantity of hydrogen — the least 
that enters into combination — is called i*.nity, even 
although it consists of 2 volumes; this is the very 
same position, in another form, that has been considered 
objectionable in the atomic hypothesis of Dalton. The 
quantity of oxygen with which this unites, is the least 
that enters into combination ; and the quantity of mer- 
cury with which this last unites, is also the least tiiat enters 
into combination. Here, then, we have three bodies 
taken in the least quantity that enters into combination* i 
How does this quantity differ ftoxxi «.tv ^Xatel T\.^^!^de<| 
understood ? An atom does not mean «i cjvxjKoJaX^ -'w^t^^ 



cannot be diviiled, but one which nevtr U hnovn to be 
divided ; combining quantity means the Game : hence, 
whatever otgectioii applies to one, applieB to the otbei. 
And, in general, the tables of equivalents proieas to 
eontun the smalleEt weights which enter into comUn- 
ation ; such, also, arc atoms. By the application of 
certain prinuples. Dr. Thomson has reduced the wraghl 
of an atom of mercury to one hidf: tile same reasoning 
umilarly aifects its combining i|UBntity. In fine, what- 
ever applies to one doctrine, seems to apply to the other; 
anil both appear to be diSerent methods of expressiiig 
the same tiling. 

if the trutli of the law^which is affirmed to govern 
multiple combinations be admitted, and if the law be 
beheved to depend on ibe union of bodies, atom to atom, 
it must be universal in its operation, and there can be 
no exception. To admit an exception, would be to 
admit the existence of parts of atoms, which the atomic 
hypothesis excludes i for the combining ratios must 
always consist of 1, 2, S, 4, &c. atoms to 1. But, in 
point of fact, we find ratios that appear to militate will) 
this law. Thus, 3'5 of iron, in order to form the prot- 
oxide, combine with oxygen 1 atom. According to the 
law of multiple ratioii, we eboutd expect that die second 
Btige of oxidation would require 2 atoms of oxygen ; 
whereas experiment proves, that IJ atom is the real 
quantity that enters into the peroxide. With a view of 
removing this anomaly. Dr. Thomson says, " I need 
hardly observe, that we can get rid of these half atoms 
with the greatest ease, by merely doubling the nimibera 
representing the constituents of the compound. Thus, 
if an atom of iron weigh 3-5, and an atom of oxygen 1, 
and if we consider it as absurd to viewperoaide ofiroa 
as a compound of 1 atom of iron and 1 ^ slom of oxy- 
gen, we have only to double ,^-5 and 1 '5, which are the 
two constituents of peroxide of iron. By so doing, we 
get 7 = y atoms of iron, and 3 =; 3 atoms of oxygen j 
and the peroxide of itonwfflVie^wim^avBAii^^WnE* 
iron and 3 atoms oxjaeii" 



ATOMiq THEORY. 401 

It does not appear to me that the anomaly is here 
more than apparently removed : the fraction has cer- 
tainly disappeared from the numhers^ but it seems still 
to exist secretly. In order to admit this explanation^ I 
think we must also admits- what chemists will scarcely 
assent to — that 1 atom of iron cannot he brought to the 
state of peroxide^ since 2 atoms require S^ and since the 
only possible division of 3 is into three separate whole 
atoms. Such cases as this — and there are but few — 
should not be considered as exceptions^ but as facts^ the 
circumstances of which are not yet fully understood. 
Should it, as it very probably wiU, be hereafter dis- 
covered that there is an oxide consisting of S'5 iron 
+ 2 oxygen, we may then suppose that the second oxide 
is a compound of an atom of each of the other two 
oxides. 



i> i> 



im 



J 






?i 






INDEX. 



AcnoDB ftrnmUtloD, S3B. 






CompDundi of, with metiU 

kulio, 31L 
Cjunic, 175. ^ 

" — uric, ftnncrmk, I|||l. 




di>, ». lu »ci|!hi, M in 



7. Of afflnity, SO. Eleetiw, Sa 
DIE, IDD. ItB ipedai: mTltr. 

a[0Mainln||it,14S. FtCfiettitf 



, Beiw*\iss™5»»™>'i\^ 



ill doctiiDe of Ulcnt 



BnCt^ £ Side ftr 

IS. iMfeiof.S Cl.cm 

Tlw rvn«tlii£ w«CT oT 
proDOrtlDa ■* UicrAdlw 

Bondcidd ; pn«B fin 



B mcoTt ch.hl 



C-oS«^26l ■ 



k1 Kparat«d 



of, JSK 
. jl»re»l properties, 3IS- 



Miaa. phmnmaia t£»L 
liibl udlint oe, eipUlDid,». 

ConillgllKbi, pTDTeBac, ST. 

Csiiper, )l>p«ips«il,M7- 

ConKltni jfirtbel. isa 

Cnvtbid, bbthcarr orrciptnin. 
SIS. Hli elperiineiili W r™* 



DmIIdo, Hb-., hii (qtolBn sf tlwdu- 
liidlyor[liBatinM|riiere,,lK Bli 

of the idiUie maghu at nUn, 
ItaTj ■irH.jlBe, HUlDinlwl* 



Dinmood, the tuDO conmotUloD U 

chiraBl, l£8. 
Dalonb M., S(L 



FihrenbriclthFTTBdmel 
Fandar, Mr., IRt. 

louTsaS.'^itnfaeBTBiM*" 
Fetrocruiic Bdiil, JT" •'^—^- 



ic acid, 131. 
incL LunirlBgi, thr^T f 

unlnUMl3aad,3K. 



n oTouuli, ah 

6.' Malleiitulln, ductlUtv, 
Dadtjof,SS7. lliipedic 
;,£)». lUiulouicmibiD. 



L tbeidUKonlitariinQltTi 
^^OIpUKUlar i¥[iu]dDn in. 

Uhea br Iti itwnce, M. 

>g it, 41. The anUgonlU of 
on, U. lu mM obvious 

,44. Deo^tf teMened br, 
ftcUof, on loUdi and fliridt, 
jil«l DT exHTiraentt, 53. 
I heU.ISL UlmpeDance 



«M,3i7. 



Hydrlodlc uM, igi. 
HjidroGTUihi kM, 1H 
HTdRHcngu, 138. 
Hrpomtroui add, IM 



<n',S4i lUTUiouiHHiitAutloni, 



Lagrange, M., hlj Ibeory t* re^- 

saoD.Sls. 
LcTiHiier, hb tbemy oTniplnaan, 

318. HIi Uhwi of cndHution, 

Ltnd, lU Kwdflc tmitJi lu pn>- 
I^Jwiti, hti Di^nlon of (he ei- 



Maddsn, r>r„ 17S. 



if, 11. Md*. 
Ehinlal did. 
dbOiti or. 13L 

Ij. CrriuUU 




the ^tt^ledrt^onH'i"^ 
StrurhiTM, orgBjibal, 1*6. 
Suberic «:ld.ffl!. _ 



INDEX. 



407 



Sal&hur,195. Spirit of, 19& Chlo- 
Tide of, 212. Photphuret o^ S2& 

Sulphuric acid, 122. Analysis of, 
SOI 

Superolefiant gas, 168. 



Taddie, Dr., S9a 

Tannin, manner of obtuning it, 

29& 
Tartaric acid, 897. 
Tendons, the, SOI. 
Thenard, 11, his view of the na- 

ture of fluor spar, 2S& 
Thermometer, 47. 
Thomson, Dr., his experiments for 
, ascertaining the specific gravity 

of protoxide of azote, 151. His 

*' l^stem of Chemistry,** extract 

fironiy determiningthe real atomic 

numbers, d98L 
Thorinum, 96SL 
Tin, its properties, 249. Found in 

Europe and in many parts of the 

globe, 250. 
Tof, philosophical oneibr extrica. 

ting heat nom air, 43. 



U. 

Ure, Dr., his process for obtaining 
iodine, 188. 



V. 

Vapour, 150. 

Vauquelin and John, thdr analysis 

of the brain, 302. 
y^;etables, acids of, 273. Alkalies 

of, 282. Other proximate prin. 

ciples of, 285. 
Vegetable albumen, 293. 
Vinous fermentation, 334. 
Volatile oils, 289. 



W. 

Wade, Dr., 163. 

Water constitutes an exception to 
the law of expansion by heat and 
contraction by cold, 47. Vapori. 
sation of, 73b Resolvable into 
oxygen and inflammable air, 105. 
Is composed of the elements of 
fire, 107. Formed by mechanical 
compression of a mixture of oxy. 
gen and hydro^gen, 107. Its ab. 
sorptive power, 181. 

Watt, Mr., 74 

Wax, 289. 

Weight, 5. Lost by immersion, 6. 
Rule for ascertaining with pre- 
cision the weight of the quantihr 
of water that is equal to the bulk 
of any solid, 9. Of air, 10. Of 
atoms, 390. 

Witter, Mr., his experiments, 163. 

Wollaston*8 gold wire, 14. His ex- 

Seriment on the chemical in. 
uence of light, 93. 



Xanthogen acid, 211. 



Young, Dr., S14i 
Yttrium, 263. 

Z. 

Zeise, Dr., 211. 

Zimomin, its properties, S92. 

Zinc, its specific gravity, 250. 

properties, 251. 
Zirconium. 263. 



Ito 



THE END. 



LomMN: 

Printed by A. & R. feottltwoode, 
MewJSCreet^SiuMreii 






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