Mrs. (Jane Haldimand) Marcet.

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fre<^uently, and most abundauAy, in its innumerablecombinations.
It is the basis of all calcareous earths and atdnes ; we find it like-
wise in the animal and vegetable cr^tionb.

Emily. And in the arts is not liine of very great utility ? ^

JUrs. jB. Scarcely any substance more so ; you know thatflt is a

850. What is the chemical name of chalk ?

851. JFhat 18 thtproceu of making lime-tDdter?

852. How may chalk be dissolveid ?

85a What will be the result if Seltzer water be poured into
lime-water ?
654 What is the basis of all calcareous earths and stones?
ii55. Of what use is lime in the arts ?



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MA&tmaiA. 201



most essential requisite in building, as it constitates the basis of all
t^ments, such as mortar, stucco, plaster, &^ ^

Lime is atso of infinite importance in agridfutu re ;/it lightens and

nsedtt



great a proportion of cla^ But it would be endless \o enumerate
the various purposes for wmich it is employed ; and you know enough
of it to form some idea of its importance ; we shall therefore, now
proceed to the third alkaline earth, magnesia.

CaroCtne. I am already pretty well acquainted with that earth ;
it is a medicine.

Mrs. B, It is in the state of carbonat that magnesia is usually
employed medicinally; it then differs but little in appearance from
its simple form, which is that of/fvery fine light white powdey It
dissolves in 2000 times its weighVof water, but forms with acicll ex-
tremely soluble salts. It has not so great an attraction for acids
as lime, and consequently yields them to the latter. It is found in
a great variety of mineral combinations, such as slate, mica, ami-
anthus; and more particularly in a certain lime-stone, which has
been di&povered by Mr. Tenant to contain it in very great quan-
tities, nt does not attract and solidify waten like lime ; but when
mixed with water afni exposed to the atmosfhere, it slowly absorbs
carbonic acid from the latter, and thus loses its causticity. Its chief
use in medicine is, like that of lime, derived from/ils readiness to
combine with, and neutralize, the acid which it meets with in the
stomach!\ . . ■ - v

Emiivl Yet, you said that it was taken/m the state of carbona|)
in which case, it has already combined wnb an acid ?

Mn, B. Yes ; but the carbonic is the last qf all the acids in the
order of affinities ; it will therefore yield the magnesia to any of the
others. It is, however, frequently taken in its caustic state as a rem-
edy for flatulence. Combined with sulphuric acid, magn^ia forfns
another and more powerful medicine commonly called fipsom stUA

Caroline, And properly, sulpkat of magnesia^ I suppose .'' Pray;
how did it obtain the name of Epsom salt ?

•Mn, B. ^ecause there is a spring in the neighborhood of Epdom
which contains this salt in great abundanceN

The last alkaline earth whieh we have to mention is strontian,
or STRONTiTBs, discovcred by Dr. Hope a few years ago. It so
strongly resembles baryte^n its properties, and is so sparingly
found in nature, and of so flittle use in the arts^ thart it will not be
necessary to enter into any particulars respecting it. i6ne of this re-
markable characteristic properties of strontites is,^ that its salts,
when dissolved in spirit of wine, tinge the flame a deep red, or
blood coloT.^

856. Of what use is lime in agriculture ?

857. What is the simple form of magnesia f
868. Does it attract water f

859. What is its chief use in medicine ?

860. In what state is it used in medicine f

861. What does it form combined with sulphuric acid ?

862. Why is the sulpbat of magnesia called Epsom salt f
663. Is strontian of any use ?

864. What is one of the i<emarkable properties of strontites ^

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V



202 ACID8,

CONVERSATION XVI.

ON ACIDS.

Mrs, B. We may now proceed to the acids. Of the metallic
ozyds, you have already acquired some g-eneral notions. This sub-
ject though highly interesting in i^ details, is not of sufficient im-
portance to our concise view of chemistry, to be particularly treated
of; but it is absolutely necessary that you should be better acquaint-
ed with the acids, and likewise with their combinations with the
alkdlies, which form the triple com poeinds, called neutral salts.
p^his class of acids is characterized by very distinct properties.
Tney all change blue vegetable infusions to a red color ; they are
more or less sour to the taste; and have a general tendency to
combine with the earths, alkalies and metallic ozyds. ]

You have, I believe, a clear idea of the nomenclaftire by whicli
^e bas^(or radical) of the acid, and the various degrees of acidifi«
Wtion, are expressed ?

Emily. Yes, 1 think so /ine acid is distinguished bjr the name of
its base, andjis degree of oxydation, that is, the quantity of oxygen
it contains^my the termination of that name in ous or ic ; thus, sul-
phureous flRrid, is that formed from the smallest proportion of oxygen
combined with sulphur ; sulphuric acid is that which results from
the combination of sulphur with the greatest quantity of oxyge^

J^rs, B. A still greater latitude may, in many cases, be allowed
to the proportions of oxygen that can be combined with acidifiable
radicals ;por several gf these radicals are susceptible of uniting
with a qifantity of oxygen so small as to be insufficient to give them
the properties of acidQ in these cases, therefore, they are convert-
ed into oxyds. Such is sulphur, which, by/exposure to the atmos-
phere with a degree of heat inadequate tcr^produce inflammation,
absorbs a small proportion of oxygen, which colors it red or browni
This, therefore, may be considered as the first degree of oxygena/
tion of sulphur ; the 2d converts it into sulphurnow* acid ; the 3d
into the sulphuric acid ; and 4thl^, if it was found capable of com-
bining jpth a still larger proportion of oxygen, it would then be
teuneduiiperoxT/genateayulpkuric acid,

Emil^. Are t^ese various degrees of oxygenation common to all
the acids ?

Mra, B, ^o^ they vary much in this respect ; some are suscep-
tible of onl^one jje^ree of oxygenation : others of two or three ;
there are but very few that will admit of more.



865. What is an acid?

866. How are acids distinguished ?

867. What is meant by the radical of an acid ?

868. What substance npites to the radical to/orm an acid?

869. How does the language of chemistry distinguish the stronger
from the weaker acid ?

870. What term is used to denot^.the first degree of oxygenation ?

871. When a radical unites with another proportion of oxygen
after that denoted by ie^ what term is Vaed ?

872. Are all acids susceptible of thQ 9ame degrpe of oxygenation ?



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ACIDS. 203

Caroline. The modern nomenclature must be of immense ad-
vantage in pointings out so easily the nature of the acids, and their
various degrees of oygenation.

Mrs, B. Till lately many of the acids had not been decomposed ;
but analogpy afforded so strong a proof of their compound nature,
that I could never reconcile myself to classing them with the sim-
ple bodies, though this division has been adopted by several chem-
ical writers. At present the murialic and the fluoric, are the only
acids which have not had their bases distinctly separated.

Caroline. We have heard of a great variety of acids ; Pray how
many are there in all ?

Mrs, B. \ believe there are reckoned at present^irty-four) and
their number is constantly increasing as the sciencl improves; but
the most important, and those to which we shall almost entirely
confine our attention, are but few. I shall, however, give you a
general view o( the whole ; and then we shall more particularly ex-
amine those that are the most essential,
^rhis class of bodies was formerly divided into mineral, vegetable
aW animal acids, according to the substances from which they
were commonly obtaineJl

Caroline, That, I should think, must have been an excellent ar-
rangement j why was it altered ?

Mrs, jB.mecause, in many cases it produced confusion^ In which
class, for iMtance, would you place carbonic acid ? X

Caroline, Now I perceive the difficulty. I should be at a loss
where to place it, as you have told us that it exists in the animal,
vegetable and mineral kingdoms. ,

Emily, There would be the same objection with respect to phos-
phoric, which (hough obtained chiefly from bones, can also, you
said, be found in small quantities in stones, and likewise in some
plants. .

Mn. B. You see, therefore, the propriety of changing this mode
of classification. These objections do not exist in the present no-
menclature ; for the composition and nature of each individual acid
is in some degree pointed out, instead of the class of bodies from
which it is extracted ; and, with regard to the more general divi-
sion of acids, they are classed under these ibree head?^

First, Acids of known or supposed simp& bases, which are form-
ed by th^oion of these bases with ogcygen^ They are the follow-
in? : J



873. How many acids are there ?

874. How t^'ere acids formerly divided ?

875. What objection was there to this division ?

976. Under how many general heads or divisioda are acid* at
presentjplaced ?
877. What kind of atids make the first class ?



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• Acids of knowD and simple bases.



20i ACIUS.

Hihe Sulphuric
^ Carbonic
Nitric
Photphorie
Artcnicfll
Tungttenie
Moljfbdenic
Boracic
Fluoric

Jtfma/A J

This class cemprcbeDds the most anciently known and most im-
portant acids. /The sulphuric, nitric, and muriatic^were formerly,
and are ^ill frequently called mineral acids. ^

2d!y. ^Acids. that have double or binary radicals, and which con-
sequently consist of tripljB co;^binations\ These are the TegetahlqL
acids, whose common radicalis a compouiga of hydrogen and carbonT)
Caroline. But if the basisW all the vegetable acids be the same
it should form but one acid ; it may inde^ combine with different
proportions of oxygen, but the nature of the acid mast be the same.
Mrs. B. The only difference that exists in the bases of vegetable
acids/ls the various proportions of hydrojgen and carbon from
whicfr'they are severally compose^ But this is enough to produce
a number of acids apparently very dissimilar. That they do not
however, differ essentially, is proved by their susceptibility of being
conyerted into each other, by the addition or subtraction of a por-
tion of hydrogen of carbon. The names of these ^cids are,
Thejdcetic
/Dxalic
^^artarotu
CHric
MaHc
OalHe
Mucous
Benaoie
Suceime
Camphoric
^ Suberic\ J
fTfae Sd class of acids consist of those whioli km triple miioalf,
strittmre therefore of a still more compoiriid attnreJ Ttei diM oom-
pr^bends the animal acids, which are, ^

^The Lactic
'^ Prussic
Formic
BomJbic
Sebaeic
^ooni^
Liihic\



Acids of doable bases, being of vegetable origin/



» Acids, of triple b»ief, or i^inml ^idi;



878. What are their names ?

879. What ones of this class are called mitMrai acids f

880. What ones make the second divisioD.'

881. What is the common radical of vegetable acids f
88S. What is the difference in the bases of vegetable aoidt ?



883.

884. What ones make

885. Name the acids with triple radicalt '



What are the nanes of the ve^^table ao&s ?
le the third division of acids?



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ACIDS. 205

I have i^veD you this summary account or enumeration of jthe
acids, as you may find it mo-e satisfactory to have at once an out-
line or a general notion of the extent of the subject : but we shall
now confine ourselves to the first class, which requires our more
immediate attention ; and defer the few remarks which we shall
have to make on the others, till we treatof the chemistry of the ani-
mal and vegetable kingdoms-

The acids of simple and knospn radicals are in most instances ca-
pable of being dwiomposed ^y combustible bodies, to which they
yield their o&yge^ If, for iiWance, I pour a drop of sulphuric acid
on this piece of irni, it will produce a spot of Tust ; you know what
it is ?

Caroline. Yes; it is an oxydj/ornoe^l hy the ojcygenof the acid
combining with the iron. ,^

•Mr9. B. In this case you seaKhe sulphur deposits the oxygen by
which it was acidified on the nmlalj And again, if we pour some
acid on a compound combustible suogtance, (we shall try it on this
piece of wood) it will combine with one or more of the constituents
of that substance, and occasion a decomposition.

Emily, It has changed the cc lour of the wood to l)lack. How ia
that? ^ , .,

J\ir8. B. /The oxygen deposited by the acid has burnt it ^ you
know that wood in burning becomes black before it is reduced to
ashes. Whether it derives the oxygen which burns it from the at-
mosphere, or from any other source, the chemical efiect on the
wood is ^heeame. In the case of real combustion, wood becomes
black,.l)ecause it is reduced ^o the state of charcoal by the evapora-
tion orits other constituents aI But can you tell me the reason why
■ivood turns black whenbumtfby the application of an acid f

Caroline, First tell me what are the ingredients of wood ?

J^rg. B.f^Ydrogen and carbol^ are the chief constituents of
«wood, as ofVll other v^etable substances.

Caroline, Wellf then, I suppose that the oxygen of the acid com-
bines with the hydrogen of the wood, to form water ; and that the
^carbon of the wood, remaining alone appears of its usual black col-
our.

Mtm, B' Very well indeed, my dear; that is certainly the most
,]^ausible explanatioii.

Emily. Would not this be a.good method of making charcoal ?

jMrs. B. It would be an extremely expensive, and 1 believe v^rjr
imperfect method ; for the action of the acid on the wood, and the
heat produced by it, are far from sufficient to deprive the wood of
•all its evaporable parts.

Caroline. What is the reason that vinegar, lemon, and the acid
of fruits* donot produce this efiect on the. wood?

Jlfrt. B, 4]Tbey are veg^etable acids, whose bases are composed of

886. How* can acids of simple radicals be decomposed?

887. If a drop of sulphuric acid falls on a piece of iron, why dpep
it produce rust ?

888. .Why does acid turn wood black ?

889. Why doQB wood become black in real combuttioD ?

890. What are the chief constituents of wood ?

891. Why do not vinegar, lemon, and the other^ vegetable acitlf
j>coduce the. $ame ^ect qip. wood ?

X9

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206 OP THE SVLPHtTBIO



hydrogen and carbon; the oxygen, therefore, will not bed|8po0ed
to quit this radical, where it is already united with hydrogenj The
strongest of these may, perhaps, yield a little of their oxygei^o the
wood, and produce a stain upon it. but the carbon will not be suffi-
ciently uncovered to assume its black colour. Indeed, the several
mineral acids themselres possess this power of charring wood in
very different degrees.

Emily. Cannot vegetable acids be decomposed, by any combus-
tibles ?

Jfrs. B. No t/oecause their radical is composed of two substan-
ces which have agreater attraction for oxygen than any known bo-



dy^



Caroline, And are those strong acids, which burn and decom-
pose wood, capable of producing similar effects on the skin and
flesh of animals?

Mm. B. Tes ; all the mineral acids, and one of them more es-
pecially, possess powerful caustic qualities, /They actually corrode
and destroy the skin and flesh ; but they do hetproduce upon these
exactly the same alteration they do on woool probably/oecause
there is a great proportion of nitrogen and othmr substanc^ in ani-
mal matter, which prevents the separation of carbon from being so
conspicuous7\



CONVERSATION XVH.

pW THJfi SULPHITBIC AND PHOSPHOBIC ACIDS ; OB THE COVr
BINATION8 OF OXTGEN WITH SULPHUB AND PH0SPH0BU8 ;
AND OP THE SUIiPHATB A^O) PH0SPHAT8.

JIfrf. B, In addition to the general survey which we have taken
of acids, I think you will find it interesting to examine individually,
m few of the most important of them, and likewise some of their
principal combinations with the alkalies, alkaline earths, and metali.
The first of these acids, in point of impiortance, is the^LPHU&ic^
formerly called oi/^wfrto/. I y

Caroline. I have known it a long time by that name, bni had ii«
idea that it was the same fluid as sulphuric acid. What resemblanoe
or connection can there be between oil of vitriol and this acid?

J|fr«. S.n^itriol is the common name for sulphat of iroe, a saftt
^hich is formed by the combination of sulphuric acid and iron : (he
•mlphuric^acid .was formerly obtained by distillation from this salt,
ana it very naturally received lits name from the substance which
afforded it/\

892. Why cannot vegetable acids hedecomposed by combustibles^

893. Do tbe mineral acids ^ave ihe same effect on the skin nnd
flesh of animals asvon wood ?

894. If they do ngot what is the reasonrf

895. What is the )>roper chemical name Mioil of vitriol ?
696. Why was it called oil of vitriol ?



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Aim 817I.PHUBIO AClU>8« 207

CaroHne, Bbtit is still nsoally ealled oil of vitrtol i||f

Mn. B, Yes : a sufficient Icogtb of time has mryet elapsed,
siDce the inventioa of the new Domenclature, for it to be generally
disseminated; bat, as it is adopted by all scientific chemists, there
is every reason to suppose that it will gradually become aniversal.
When 1 received this bottle from the chemists, oil of titriol was in-
scribed on the label ; but as I knew you were very punctillious in re-
gard to the nomenclature, 1 changed it, and substituted the words
tulphuric ^pd.

Emily, rrhis acid has neither colour nor smell, but it appears
much thicser than water!|

Mn. B. f\. is nearly tvwce as heavy as water^'^nd has, you see,
an oily consistence. J

Caroline, And it is probably from this circumstance that it has
been called an oil ; for it can have no real claim to that name, as it
does not contain either hydrogen or carbon, which are the essential
constituents of oil.

JMr*. B, Certainly, and therefore, it would be the more absurd
io retain a name which owed its origin (o such a mistake^^anaiogy.

Sulphudc acid, in its purest state would probably befa concrete
substance jbu^s attraction for water is such, that it is^ impossible
to obtain IRat acid perfectly free from it: it is. therefore, always
seen in a liquid form, such as you here find it j ft)ne of the most
striking propertiea of sulphuric acid is that ofe^mng a considera-
ble quantity of heat when mixed with watert this 1 have already
shown you. /

Emily. Tes, I recollect it ; but what was the degree of heat pro-
duced by that mixture ? iv

J^rs. B. The thermometer may be raised t>y ityfo 300 degrees, )
which is considerably above the temperature of boil^Qg water. /

Caroline, Then the water may be made to boil in that mixture ?

Jlfr«. B. Nothing more easy, provided that you employ sufficient
quantities of acid and of Water, and in the due proportions. The
greatest heat is produced by a mixture of^e part of water to four
of the acidl we shall make a mixture <R these proportions, and
immerse iw4t this thin glass tube, which is full of water.

Caroline. The vessel feels extremely hot, but the water does not
boil yet.

Jnrs. B. You must allow some time for the heat to penetrate the
tube, and raise the temperature of tlte water to the boiling point —

Caroline, N,ow it boils — and with increasing violencet.

J\ir*. B, But it will not continue boiling long : fo^he mixture
gives out heat only while the particles of the water anekth^ acid are
mutually penetrating each other ; as soon as the new arrangement

. _— Sl^. :

897. What is the colour and smell of this acid?

898. Whaiis its weight?

899. What wonid sulphuric acid be in its purest state ?

900. What is the consequence of mixing it with water ?

901. What is one of its most striking properties ? ^

902. How high may a thermometer be raised by it ?

903. In what proportions must sulphuric acid and water be mix-
ed in order to produce the greatest degree of heat ?

904. Why does the mixture iif sulphuric acid and water give out
beat only for so short a time .'



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■J



S08 OF THB 8ULPHTmiC

of these parties is affected, the mixture^ill gradually cool, and
the water return to its former temperaturej

You have seen the manner in which sijjiphuric acid decomposes
all combustible substances, whether animal, vegetable, or mioeraly
and burns them by means of its oxygen ?

Caroline. I have very unintentionally repeated the experiaent
on my gown, by letting a drop of the acid fall upon it, and it has
made a btain, which I suppose will never wash out.

J>lr8. B. No, certainly ; for before you can put it into water, the"
spot will become a hole, as the acid has literally burnt the muslin.

Caroline, So it has indeed ! Well, I will fasten the stopper, and

Eut the bottle away, for it is a dangerous substance — On, now f
ave done worse siill, for I have spilt some on my hand !

J^rs. B. It is then burned, as well as your gown, for you knovr
that oxygen destroys animal as well as vegetable matter ; and as
far as the decomposition of the skin of your finger is effected, there
is no remedy ; but by washing it immediately in water, you will di^
lute the acid, and prevent any further injury.

Caroline, It feels extremely hot, I assure you..

Mrs. B, You have now learned by experience, how cautiously
this acid must be used. Yon will soon become acquainted with
another acid.^ie nitric, which, though it produces less heat on the
skin, destroysNt still quicker, and makes upon it an indelible stainll
You should never handle any substances of this kind without pre^
viously dipping your fingers into water, which will weaken their
caustic effect. But, since you will not repeat the experiment, I
must put in the stopper, for the acid attracts the moisture from the
atmosphere, which would destroy its strength and purity.

Emily. Pray, how can sulphuric acid be extracted from sulphat
of iron by distillation ?

JWr*. JB. The process of distillation, you knoMT^onsists in sepa»
rating substances from one another by means of iVeir different de-
grees of volatility, and by the introduction of a new chemical agent,
caloric^ Thus, if sulphat of iron be exposed in a retort to a proper
degree jif heat, it will be decomposed, and the sulphuric acid wiH
be volatilized.

Emily. But now that the process for forming acids by the com-
bustion of their radicals is known, why should not -ihh. method b^
used for making sulphuric acid ? A^Jf

JJt8. B. I'his is actifally done in most manufactiSK' but^e
usual method of preparing sulphuric acid does not con^Tin bln^
ing the sulphur in oxygen gas (as we formerly did by way of ex-
periment,^ but in heating it together with another substance, nitre,-
wbich yields oxygen in sufficient abundance to render the combus-
tion in common airiepid and complete!^ ^

Caroline* This substance, then, answers the same purpose as ox-
ygen gas?

J^rg, B. Exactly. In manufactures the combustion is performed
in a leaden chamber, with water at the bottom, to receive the va-
pour and assist its condensation. The combustion is "^Kiwever, never
so perfect but that a quantity of sulphureotk* acid %' formed at the



905. How does sulphuric compare with nitric acid ?

906. In what consists the procesflpf distillation?

907. How is sulphuric acid obt Jbed ?

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AND 8VLPHUBB0VS ACIDS.

same time ; for, if you recoUect tbaj^the sulphureous acid, accord-
ing^ to the chemical nomegclatureydiffers from the sulphuric only
. by cootaioiog less oxygeA V^

From its own powerful ffroperties, and from the various combina-
t^ns ii>to which it enters, sulphuric acid is of great importance io
ikiany of the arts.

It is used also in medicine in a state of great dilution ; for were
it taken iniernaliy, in a concentrated state, it would prove a most
dangerous poison.

Caroline, I am sure it would burn the throat and stomach.

Mrs. B. Can you think of any thing that would prove an anti-
dote to this poison ?

Caroline. A large draught of water to dilute it.

Mr8. B That would certainly weaken the caustic power of the
acid, but it would increase the heat to an intolerable degree. Do
you recollect nothing that would destroy its deleterious properties
more effectually ?

Emily. An Alkali might, by combining with it ; but, then, a pure
alkali is itself a poison, on account of its causticity.

Mrt. B. There is no necessity that the alkali should be caustic.
Soap, in which it is combined with oil ; o/magnesia, either in the



Online LibraryMrs. (Jane Haldimand) MarcetConversations on chemistry .. → online text (page 25 of 43)