Mrs. (Jane Haldimand) Marcet.

Conversations on chemistry .. online

. (page 28 of 43)
Online LibraryMrs. (Jane Haldimand) MarcetConversations on chemistry .. → online text (page 28 of 43)
Font size
QR-code for this ebook

Mrt. B, And alsoi the breath of animals

Caroline. The bre^^thof animals ?• I tbeught' you said that the
^8 was not at all respirable, but on* the contrary, extremely poi-

Mn. B. So it is ; but although animals cannot breathe in car-
bonic acid gas, yet in the process of respiration, they have the pow*
er of forming this pas in their lungs ;• so that the air which we ex-^
pire^oT reject from the lungs, always contains a certain proportion
of carbonic acid, which is much greater than that which is commen*>
ly found in the atmosphere.

Caroline. But what is it that renders Carbonic acid such adead-
Hy poison ? ^

Mrs. B.rThe manner in which this g*as destroys life, seems to be
ftierely by V^venting the access of respirable u?t for carbonic
acid gas, unless very much diluted with common atlS does not pen-
etrate into the lungs* as (he windpipe actually contracts and refu-
ses it admittance. —But we must dismiss this subject at present, as
we shall have an opportunity of treating of respiration much more
fully, when we come to the chemical functions of animals.

Emily Is carbonic acid as destructive to the life of vegetables as
it is to thatgf animals ?

Mr8,B/T(2i vegetable be completely immersed in it, 1 believe
it general (y^roves fatal to it ; but mixed in certain proportions
with atmospherical air, it is on the contrary, tery favourable to ve-

* This idea is at raudom. We cannot account fbt the origin of
carbonic acid in its native state any better than we can for oxygen.
It cannot be the product of combustion, since it existed before the
gfrowth of combustible materials. — C.

966. How does marble and calcareous earth obtain its grea
quantity of carbonic acid ?

987. Why do we not experience the pernicious effects of tbe car-
bonic acid in the atmosphere?

988. How is the atmosphere suppli^ with this acid ?

989. Why is carbonic acid gas so destructive toaoimflAlife f

990. Wliat effect does it have on vegetation f

Digitized byV^OOQlC


Ton Mmember, I suppose, our meDtioning^ the mioeral waters,
both natural aud artificial, which cootaiu carbonic acid gas ?

Caroline, You mean the Seltzer water ?

Mt$, Bo That is one of those which are most used ; there are,
however, a variety of others into which carbonic acid enters as an
iofredieot : all these waters are usually distinguished by the name
omadulout or gtueotu mineral watei^

The class of salts c^Med^rbpnaCtm the most numeronsip nature;
we must pass over them n» a very^ursory manner, as the subject
is (ar too extensive for us to enter on it in detail, ^he state of car-
bonat is the natural state of a vast number of minerals, and partic-
ularly of the alkalies and alkaline ekrths,, as they have so great an
attraction for the carbonic acid, that they are almost always found
combined with it] and vou may recollect that it is only by separa-
ting them from tms acid, that they acquire causticity and those
striking qualities which I have formerly described. AH marbles,
chalks, shells, cajqareous spars, and limestones- of every diesqrip-
tioa, are Qeutral salts, in whichmme, their common basis, has.lott
sjl its characteristic properties^

Emify. But if all these vari(Kis substances are formed by the un-
ion of lime with carbonic acid, whence arises their diversity i>tt
htttt and apn^Barance ? .

Mrs, B.^Doih from the different proportions of (heir component
parts, and from a variety of fureign ingredients which may he oc-
casionally blended with thenV; fhe veins and colours of marbles,
for instance, nroceed from a^rmtture of metallic substance?^ silex
and alumine also frequently enter into these combinations^ The.
Tarioiis carbonatSy therefore, which I have enumerated, cannot be
considered as pure and unadulterated neutral salts, aUhou||^h thej(
certainly belong to.that class of bodies.




Mrs*B, We DOW come to the three remaibinr acids with simpfo
bases, the compound nature of which, though long suspected, nav
been but recently proved. The chief of these is the muriatic ;^-

991. What are the waters called, into which this gas enters as an
ingredient ?

992. What are the salts formed by the acid of this gas ?

993. How extensive is this chass of'saMs, and under what forms
do they chiefly occur in nature ?

994. If hme is the common basis of marbles, chalks, shells, eal-
oireous spars, and lime stones, why is there such a diversitj in
their form and appearance ?

996. From what do the veins and colours of marble proceed ?

Digitized by LjOOQ IC


bttt I shall first describe the two others, as their bases ba^e been
obtained more distinctly than that of the muriatic a<^

Youtmay recollect 1 mentioned the boracic ACiD.rrbis is found
very sparingly in some parts of Europe, but for the uw)f manufao-
tures we ha?e always received »t from the remote couijiry of Thi-
bet,' where it is found in some lakes, combined with sodal It is ea-
sily separated from the boda by sulplmric acid, and apftan in the
form 6f shining scales, as you see here.

Caroline. I am glad to meet' with an acid which we need not be
fllraid to- touch ; for I perceive from your keeping it in a piece of
paper, that it is more innocent^an our late acquaintance, the sul>
phuric arM nitric acids.

Mrt.^» Certainly ; but being more inert, you will not find ita^
properties so interesting. However its decomposition, and the
brilliant spectacle it affords when its basis a^ain unites with oxy«
^n, atones for its want of other striking qualities.

Sir H. Davy succeeded in decomposing the boracic acid, (whieb-
had till then, been considered as undecompoundable,) by variou9<
methods. On exposing this acid to the Voltaic batteiy, the posi-
tive wire gave outfexygen, aed on the nenttve wire was de e ssitd l
a black substance, in appearance resembling cfaarcoaU. This wa8>
the bMis of the acid, which Sir H. Davy has called ^oracium or

The same substance was obtained in more 'considerable quanti*
• ties by exposing the acid to a great heat in an iron gun barrel.

A tnird method of decomposing the boracic acid 'consisted in bum-
ring potassium in contact with it in vacuo. The potassium attracts^
the oxygen from the acid, and 'leaves its basis ia a separate state.

The recomposition of this acid I shall show you by burning some
of its basis, which you see here, in a retort full of oxygen gas. The
heat of a Candle is aU that is required for this combustion. —

Emily. The light is astoni^hing^ly brilliant, and what beautiful
sparks it throws out !

Mn. B. The result of this combustion is the boracic <ecid, the
nature of which, you see,.is proved, both by analytic and synthetic
means. Its basis ba^ not, it is true, a metallic appearance ; but it
makes very hard alloys with other metals.

Etnily. But prdy,i!ifrs.''6. for what purpose is the boraoic acid
used in manufactured ?

Mrt. B. Its principal use is in conjunction with soda, that is, in
the stata^ of bor^ dfstfda, which in the arts is commonly called- bo-
rax. Mhis salt has a peculiar power of dissolving metallic oxy^
and o^promoting the fusion of substances capable of being meltMi
it ia accordingly employed in various metalbc arts ; it is used,ior
example, to remove the oxyd from the surface of metals, and is of-
ten employed in the assaying of metallic ores. jr>

Let us now proceed to the fluoric acid. /This acid is obtained
from a substance which is found frequently in inines, and particn-

996. Where is th^ boraoic acid obtained ?

997. What is the composition of borax .'

998. What is the basis of this acid ?

999. For what purpose is the boracic acid vsed id manufiaLCturaa?
VIOOO. From what is the. fluoriaaoid obtaioed^gigtized by Google


larly in those of Derbyshire, calledT^ii^/a name which it acquired
from the circumstance of its being useoW render the ores of met-
als more fluid when hessi^tedj ^

Caroline. Pray, is not Uifs thoDerbyshire span^f which so ma-
ny ornaments are made ? ^ — ^

Mrs* B. t*be same ; but thougbi it has long been employed for a
variety of purposes, its q.ature was unknown until Scheele, the great
. Swedish chemist, discovered that it consiste(^ lim^jinited with a
peculiar acid, which ohtamed the name of Jtmnc acM It is easily
separated from the lime by the sulphuric acid, and unless condens-
. ed in water, ascends in the form of ga3. A very peculiar property
of this acid, iuts union with siliceous earths, which 1 have already
mentioned, ut the distillation of this acid is performed in glass ves-
sels, they are corr^ed, and the siliceous pjirt of the glass comes
over, united with the ga^ if water is then admitted, part of the si-
lex is deposited, as you mzj observe in the jar.

Caroline. I see white flakes forming on the surface of the water;
is that silex ?

JUrg. B. Tes, it is. This power of corroding glass has been used
for engraving* or rather etching upon it. ^e glass is first oo7er-
ed with a coat of iwas., through;which the figures to be engraved are
to be scratched with a pin ; then pouring the fluoric acid over^^he
wax, it corrodes the glass where the scratches have been mad^

Caroline. I should like to have a bottle of this acid to make^n-

Mn. B' But you could not have it in a^^cut bottle ; for in that
case the acid would be saturated with silex, and incapable of exe-
cuting an engraving ; the same thii^ would happen were the acid
kept in vessels of porcelain or eartheni^are ; this acid^ust there-
fore be both prepared and pre^ervednn vessels cf silver
If it be distiiledifrom fluor spar and Attplic acid, \n silver or leaden
i vessels, the receiver being kept very cold during the distillatioD, it
assumes the form of a dense fluid, and in that state is the most in-
V tensely corrosive substance known* This seems to be the acid com-

*A bottle of flporic acid is not easily obtained. To make etch-
iiigv on glass, first^over the glass with a thvi coat of bees wax. —
This is done by warming it over a lamp, and passing the wax over
the surface. Then make the drawing by cutting through the wsul
..quite down to th^glass. Tddo the etching in thk small way, tal^e
a lead or tin cup, and on the bottom place about a table spoonful of
pulverized fluor jspar, and on this ..pour lulphuric acid enough to
moisten it — ^plaqe the glass on the^cup as a cover, with the side to
be etched downward-^tbi^n set the cop in warm water, or warm
the bottom oirer a lamp^iaking care not to melt the wax. In 15 or
20 minutes or more, the etching will be done. In this way, draw-
ings are easily and beautifully made on glass. C.

1601. From what does it derive its name ?

1002. Bv what other name is this acid called ?

1003. Of what does it consist.'

1004. What singular effect does it have on glass ?

. 1005.' How could you describe the method of etching on gliji^s^
, 10a6.'Jn what ktndpf voisels majit be preserr^? ^oQle


bined wit^ a little water. It mav be c9\ledUi^r(hJluic acM and
Sir A. DaTy has been led, from fate experimeDts od the subject, to
consider ^r« fluoric acid as a compound of a certain unknown prin-
ciple, whicb he CBllsmtiorinhwiih hydrogen.

Sir H. £>a7y has aUo attempted to decompose the fluoric acid by
burning potassium in contact with it ; but be has not yei been able
by this or any other method, to obtain its basis in a distinct separate

We shall conclude our accoudt of the acids with that of the muri-
atic AcipjU^hich is, perhaps, the most curious and interesting of all
of them, fit is found in nature combined with soda, lime^ and mag-
nesia^ MuHat of ioda is the common sea salt ; and from this sub-
8tan<^ the acid is usually disengaged by means of the sulphuric acid.
The natural state of the rpuriatic acicWs that of an invisible, perma-
nent gas, at the commontemperaiure of the atmospber^ but it has
a remarkahje strong attraction for water, and assumes 'Ae form of a
whitish cloud whenever it meets any moisture to combine with. This
acid is remarkable for its peculiar aod Yery pungent smell and pos-
sesses, in a powerful degree, most of the acid properties. Here is a
bottle containing muriatic acid in a liquid state.

Caro/ine. And how is it liquefied ?

Mr». B. my impregnating water with it ; its strong attraction for
water makes it very easy to obtain it in a liquid form'x Now, if I
open the phial, you may observe a kind of vapour rinng from it,
which is muriatic acid ^, of itself invisible, but made appai^ntby
combining with the moisture of the atmosphere.

Emily, Have you not anv of the pure muriatic acid gas ?

^ Jifrs, B. This jar is full of that acid in its gaseous state-r-it is

Qi^Terted over mercui^ instead of water, because, being absorbable.

J^ water« this gas cannot be confined by it. — 1 shall now raise the

jar a little on oae side, and suffer some of the gas to escape. Yoi^

see that it immediately becomes visible in the fonm of a cloud.

EmUy* It must be, no doubt, from its uniting with the moisture of
the atmosphere, that it is converted into this diwy vapour. ^

^ri.B. Certainly; and for the same reason, that is to saj,£it8
extreme eap^erness to unite withwaterlpis gas will cause snowto
melt as rapidly as an intense ixh ^^

This acid proved much more mractorj, when Sir H- Davy at-
tempted to decompose it, than the other two undecomposed acids.
Jt is singular that potassium will bum in muriatic acid, and be con-
verted into potash, without decomposing tbe acid and the result of
Hkkin combustion is a maritU o/votath ; rar the potash as soon an it is
isgenerated, combines with the muriatic acid.

Caroline. But how can the potash be regenerated if the muriatic
acid does not oxydate the potassium ?

Mr», B. The potassium in this process, obtains oxygen from tbe
moisture with which tbe muriatic acid is always combined, and, ac

1007. What did Sir H. Davy call this acid ?

1008. Where is muriatic acid found ?

1009. What is the natural state f

1010. How is it li<|uefied ?

lOl 1. How can this gas be coiifined without a mercurial bath ?
lOH. What effect will muriatic acid gas hare on snow ?
1013. Why will it ilielt snow ?

_^ Digitized by LjOOQIC

20 ^


cordiog^ly, hydrog^, resulting from the decomposition of the mois^
ture, is invariably evolved.

Emily. But why not make these experiments with dry muriatic adtf?
Mrs. B. Dry acids cannot be acted on by the Voltaic battery be-
cause acids are non-conductors of electricitjr, unless moistenedTyq
the course of a number of experiments* which Sir H. Davy mfde
upon acids in a state of dryness, he observed that the presence of
water appeared always necessary .to develope the acid properties, so
that acids are not even capable of reddening vegetable blues if they
have be6n carefully deprived of moisture. This remarkable cir»
cumstance led hiin to suspect, that water, instead of oxygen, may be
the acidifying principle ; but this he threw out rather as a conjec-
ture than as an established point.

SirH. Davy obtained very curious results from burning potassium
in a mixture of phosphorus and muriatic acid, and also of sujphur
and muriatic acid ; the latter detonates with great violence. All his
experiments, boijever, failed in presenting to his view the basis of
the muriatic aicidjof which he was in search ; and he was at last in-
duced to form aiApinron respecting the nature of this acid, which
1 shall presently .e^tplain.

Emily. f^h\s acid susceptible of different degrees of oxygenation ?

J(fr«. ^.(Yes| for though it cannot be deoxygenated, yet we may
add oxygento it.

Caroline. Why, then, is not the least degree of oxygenation of
the acid called the muricUouSf and the higher degree the muriatie
acid ? ^

Mrs. J9. (Because, instead of becomiflg, like other acids, more
dense, and more acid by an addition of oxygen, it is rendered, on the
contrary, mo^e volatile, more pungent, but less acid, and less absorb-
able by wate^ These circumstances, therefore, seem to indicate
the propriety^f making an exception to the nomenclature. ' The
highest degree of oxygenation of this acid has b^en distinguished by
the additional epithet of oxygenated, orj for the sake of brevity, oay,
so thatit i8called^:;yg:ena/edfor oxy-muriatie aeic^ This likewise
exists in a gaseous'^fcrm, at the temperature of^he atmosphere ;
it i^ also susceptible of being absorbed by water, and can be con-
gealed, or solidified, by a certain degree of cold.

Emly. Apyd how do you obtain th^ oxy-muriatic acid ?

Mrs. B.flu various ways ; but it may be most conveniently oV»
tained by distilling liquid muriatic acid over oxyd of manganese,
which supplies the acid with the additional oxygen. One paK of the
acid being put into a retort, with twp parts of the oxyd of nranga-
nese, and the beat of a lamp applied, the gas is soon diseng^aged, vol

iOI4. Why cannot dr^ acids be acted en by the Vdtaic battopj ?
J 015. What is the basis of muriatic acid f

1016. Is this acid capable of combining with different propor-
tions of oxygen ?

1017. Why is not the least deg^ree of oxygenation called the onu-
riatous acid ?

1018. What is the highest degree of oxygenation of this acid called ?

1019. How it the oxy-muriatic acid obtained ?

• Digitized by LjOOQIC '


may be repeived over water, as it is but sparingly absorbed by im
I have collected some in this jar — * - /

Caroline. It is not invisible, like the generality of g^ases ; for it is
of a yellowish color.

Jart, B. The mariatic acid extinguishes flame, whilst, on the
contrarv, the oxy-muriatic makes the dame lai:ger, and gives it a
dark red color. Can you account for this difference in the two acids ?
Emily* Yes, I think so ; ^e muriatic acid ^ill not supply the
flame with the oxygen n^essary for i(.s support ; but when this
acid is further oxygenated, it will part with it^ additional quantity
of oxygen, and in this way support combustionf

J\ir8. B. This is exactly the case : indeed tie oxygen added to
the muriatic acid, adheres so slightly to it, that it is separated by
mere exposure to the sua's rays. This acid is decomposed also by
combustible bodies, many of which it burns, and actually ioflameS)
with6ut any previous increase of temperature.

Caroline, That is extraordinary indeed ! I hope you mean to in-
dulge us with some of these experiments ?

Mrs. B. I have firepared several glass iars of oxy muriatic acid
gas for that purpo^. In the first we shall introduce some Dutch
l^ld lekf.-^Uo jrou observe that it takes fire f

Emily. Yes, indeed it does — how wonderful it is ! It became im-
mediately red hot, but was soon smothered in a thick vapor.
Caroline. What a disagreeable smell !

Mri. B. We shall trv the same experiment with phosphorous in
another jar of this acid. Tou had better keep your l^andk^rchief to
yonr nose when I open it— now let us drop into it this little piece of
phosphorus — '

Caroline. It baros teally ; and almost as brilliantly as in oxygen
gas ! But what is most extraordinary, these combustions take place
without the metal or phosphorus being previoqsly lighted, or even
in the least heated.

Jtfr#. B' AH these carious efEeots arerawing to the very gpreat fa-
cility with which this acid yields c^ryAn to such bodies as are
strongly disposed to com^bine with it!\ It appears extraordinfiiry in-
deed to see Dodies, and metals in pmicular, melted down and in-
flamed by a gas, without any increase of temperature, either of the
gas, or of the combustible. The phenomenon, however, is, you see,
well accounted for.

Emily. Why did you burn a piece of Dutch gold leaf rather than
a piece of any other metal ?
JIfrt* B. Because, in the first place, it is a composition of metals

* Breathing only a few bubbles of the g2B is attended with bad«-
sometimes with dangerous consequences. The young chemisti
therefore, bad better not undertake to make it.— C.

f According to ihis new theorv of chlorine, as will be explained
at the end of this conversation, this coitibustion is effected m ^con-
lequenceof the union of chlorine (or oxy-moriatic acidj with the
hydrogen of the combustible body.

1030. Why will the muriatic acid extinguish flame, and oxy 0911-
riatic acid make it larger, giving it a dark red color ?

1021. Whj^ will some combustible bodies buroin tip
out aDyprerioQs increase of temperature? g*^^""

232 &XY-l^EtATIC Acn^.

(consisting chiedy of copper) which burns re^ily ; add I use a thite
metallic leaf in preference to a lump of metal, because it offers to
the action of the g:a8 but a small quantity of matter under a larg^e
surface. Filings, or shavings, would answer the purpose nearly as
well ; but a lump of metal, though the surface troula oxydate with
jpreat rapidity, wMld not take fire. Pdre gold is not inflamed by
pxy-muriatic aciwas, but it is rapidly ox;^dated, and dissolved by
TtT indeed, this acid is the only one that will dissolve gold.

Emily. This, I suppose, is what is commonly called aqua Yegia^
which you know is the only thing that will act upon gold.

Jdrk, B. This is not exactly the case either; for axiua regia is
composed of a mixture of muriatic acid «nd nitric acid. — Biit,/iQ
fact, the result of this mixture is the formation of ozy-muriaitie
acid, as the muriatic acid oxygenates itself at the expeiyse of the
nitric ; this mixture, therefore, though it bears the name of nt/ro-
muriatic acid, acts on^old merely in virtue of the oxy-muriatic
acid which it containsT

Sulphur, volatile oiR, and many other substances, will bu1*n in the
same manner in oxy-muriatic acid gas-; but I have not pr^ared a
sufficient quantity of it, to show combustion of all thebe booies.

Caroline, There are several jars of the gas yet remaining.

Jlfr#. B. We must reserve these for future experiments. The
oxy-muriatic acidiloes not, like other acids, redden the blue tege-
table colors ; butvt totally destroys all color, and turns vegetables
perfectly white\ Det us collect some vegetable substances to put
into this glass, which is full of g^s.

Emily. Here is a sprig of mvrtle—

Caroline. And here some colored paper —

Mrs, Bi We shall also put in this piece of scarlet riband, and a

Emily. Their colors begin to fade immediately. But how does the
gas produce-ihis effect ?

Jnn, B. (The oxygen combines Vith the coloring matter of these
substances, and destroys it ; that is to say, destroys the property
which these colors had of reflecting only one kind*of rays, and ren-
ders them enable of n^ecting them all, which, you know, will
make them appear whit^ ^M prints may b6 cleaned by this acid,
for the paper will be wlMffenCd without injury to the impression, as
printer's ink is made of materials (oil and lamp black) which are
not acted upon by acids^

jlThis property of theoxy-muriatic acid has lately been employed
iiPCDanufkctures in a variety of bleaching processes^ but for these
purposes the gas must be dissolved in water, as the acid is thus ren-
dered much milder and less powerAil in its effects ; for in a gaseous,

10^. By what aci^ is gold oxydated and dissolved f

1023. Why does a mixture of nitric, and muriatic acids dissolve
gold, wheu neither of them will do it alone ?

1024. What effect does the oxy-muriatic acid have on vegetable
colors ?

1025. Why does it produce this effect?

1026. Why is it, that the paper of old prints may he cleansed by
this acid, without any injury to the impression?

1027. Of what use is the oxy-muriatic acid in maniiAtctores ?

Digitized by LjOOQIC


itote, it would destroy tke textnre, a» weU as the oobr of the sub-
stance submitted to its aoUoii.

CaroUne. Look at the things which we put ifito the .gas ; they
ba?e now entirely lost their color !

Jklr*. B, The effect oi the aoidii almost eomplete^^ aod if we
were to exaimoe the i|uaDtitythat remains, we riiould find it tocon^
sisu^iefly of muriatic acid.

^he oxy-moriatic «3id has been used to purify the air in ferei
ho^itals andprisoos,as it bums and destroys putnd.efflufiaef ev^ij
kind. The infection of the smail-pox is likewise destroyed by ^s
«is, and matter ^hat has be^ submitted to its influence will oa
longer generate that disorden

CanHne. hideed, I think (Be remedy must be nearly as bad as
the disease; the oxy-mCiriatio acid has such a dreadfully suffocat-
ing smell.

Jtfrt* B. It is certainly extremely offeosiye ; but^y keeping the

Online LibraryMrs. (Jane Haldimand) MarcetConversations on chemistry .. → online text (page 28 of 43)