Mrs. (Jane Haldimand) Marcet.

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This retort is filled wuh carbonic acid gas. h will put a small
piece of potassium in it ; but for this combustion a slight elevation
of temperature is required, for which purpose I shall hold the retort
over the lamp. *

Caroline, Now it has taken fire and burns with violence ! )t has
burst the retort. -^

Jdrs. B. Here is a piece o^regenerated potash ijpan you tell me
why it has become so black ? /

JEmUy. No doubt it is blackened by the carbon, which, when its
oxygen entered into combination with the potassium, was deposited
an it surface.

Jtfrt. B, Tou are right. This metal is perfectly fluid at the tem-
peirature of one hundred degrees ; at fifty degrees it is solid, but
soft and maUeable; at thirty -two degrees it is bard and brittle* and
its fracture exhit>its an appearance of confused crystallization. It
is scarcely more than half as heavy as water ; its specific gravity be-
ing about six, when water is reckoned at ten ; so that this metal k
actually lighter than any known fluid, even than ether.

Potassium combines with sulphur and phosphorus, forminr snl-
phurets and pbosphorets ; it likewise forms alloys with severalmet-
als, and amalgamates with mercury.

Emily. But can ia sufficient quantity of potassium be obtained, by
means of the Voltaic battery, te admit of all its properties and rela-
tions to other bodies, being satisfactorily ascertained ?

Jir». B. Not easily ; but I must not neglect to inform you that a
method of obtaining tnis metal in considerable quantities, has since
been discovered. Two eminent French chemists, Thenard and
Gay Lnssac, stimulated by the triumph which Sir H. Davy had ob-

693. At how low a temperature will potassium bum in contaet
with water ?

694. Why, until the discovery of potassium, had carbonic fteid*
gas been considered incapable of supporting combustion.^

695. How does potassium decompose this gas?

696. What metal is lighter than any known fluidf

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METALS. 169

Uine^, tttempted to separate potassium from its combinattoii with
oxygen, bjrcoromoo chemical means, and without the aid of elec-
tricity. /They caused redrhot potash in a state of fusion, to filter
throB^h ftron iurning^ in an iron tube, heated to whitenessX Their
expenmeot was •crowned with the most complete succesf i more
potassium was obtained by a single operation, thap could have been
collected in many weeks by the most dili^en^t use of the Voltaic
battery. ^

Emtfy. In this experiment. I suppose thetoxyj^en quittedjts com-
bination with the potassium,/to unite witb the'iroo tnrnin^sl^

Mrs. B. Exactly so ; and thus the potassium was obtainea in its
simple state. From that time itiias become a most convenient and
powerful instrument of deoxygenation m chemical experiments.—
This im{>ortant improvement, en|;'rafled on Sir H. Davy's previous
discoYeries, served bat to add to his glory, since the facts which he
had estaMished, when possessed only of a few atoms of this curious
substance,^and the accuracy of his analytical statements were all
confirmed, .when an opportunity occurred of repeating his experi-
ments opoa this substance, which can now be obtained in unlimited
quantities.

CaroligM. What a satisfaction Sir H. Davy must have felt, when
by an isi^ort of genius, he succeeded in bringing to light, and actually
^ving existence to these curious bodies, which without him might
perhap»bave ever remained concealed from our view ?

Mr*, B. The next substance whichSir H. Davy submitted to the
iDflvence of the Voltaic battery, waa^odoi the othej; fixed alkali,
which yielded to the ^ame powers of decomposition ;Jrom this alkali,
too, a metallic substance was obtained, very ana^gl^s in its proper-
ties to that which had been discovered in potash | Sir H. Davy has
called itflODiuM^ It is rather heavier than potassium, though con-
8iderabI)Mighter>A)an water ; it is ;iot so easily fusible as potassium.

Encouraged by these extraordinary results, Sir H. Davy next
4)erfonned A.aeries of beautiful experiments on AmmoMOy or the vo-
lalile alkaii, whi^b, from analog5 , he was led to suspect might aJao
contain oxygen. This be soon ascertained to be the fiust, but h%
•lias not yet succeeded in obtaining the bap«« "'' ammftnio it. « aa^*^
rate state ; it is firatm analogy, and from the i

alkali has, in its gaseous form, to oxydat< t

amalgams which can be pjbtained ftfmk amn
«s, that the proois of alkali being also a mi

Thus, then, the three alkalies, two of wh
sidered as simple bodies, have how lost all
have i«X3ordingly class^ the alkalies a
whose properties I shall treat of in a future

Emiiy» What are the other newly discovered metala which yon
haveaUud^ to in your list of |;imple bodies ?

697. H<m may potassium be .obtained in larjs^ qnantitiea ?

698. In the experiment for obtaining potassium, why :did,^he.QIr
ygen qnit that suDstance ?

699. What was the o^xt ||ubstance submitted to. the in^e|i(<|^«r
rthe Voltaic battery ?

' 700. What was the eibot ?

701. What is the substance produced , by the d^Q^PPffiionof
^Sodajp^led? . -

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170 UTAIJ.

Mrt. K They are the metals of the earth which beeame next the
object o( Sir H. Dary's researches ^rlhese bodies had nerer jet baeo
decomposed, though they were 8tro%ly suspected, not only of beiof^
compounds, but of beingf metallic oxyds. From the circomstaace
of their incombustibility, it was conjectured, with tome plaosi^ty,
that they mirbt possibly be bodies that had been already barnt\

Caroline. And metals, when oxydated, become, to all appelr-
ance, a kind of earthy substance.

Mr». B.fTh^ have, besides, several features of resemblance with
metallic oftydsl Sir H. Davy had, therefore, great reason to be
sanguine in hi/expectations of decomposing tl^m., and be was -not
disappointed. He could not, however, succeed in obtaining the ba-
sis of the earths in a pure separate state ; but metallic aUoj;s were
formed with other metals, which sufficient^ly proved the existence
of the metallic basis of the earths.

The last class of new metallic bodies which Sir H. Davy discov-
ered, was obtained from the three undecompounded acids, the bora-
cic, the fluoric, and the muriatic acids ; but as yon are entirely un-
acquainted with these bodies, l^hall reserve the account of their
decomposition, till we come to treat of their properties as acids.

Thus in the course of two years, l^ the unparalleled exertions of
a single individual chemical ecience has assumed a new aspect. —
Bodies have been brought to light^^which the human eye never be*
fore beheld, and which might have remained eternally concealed
under their impenetrable disguise.

It is impossible, at the present peridd, to appreciate, to their HXi
extent, the consequences which science or the arts may derive fhom
these discoveries ; we may, however, anticipate the most important
results.

In chemical analysis, we are* now in possessioa^f more eneiiget-
ic agents of decomposition than were ever before known.

In geology, new views are opened, which will probably operate m
revolution in that obscure and difficult science. It is already pror-
e^ that all the earths, and, in fact, the sol^surface of this globe>
A[re metallic bodies mineralized by exygep^and as our planet has
Vbeen calculated to he considerably more desee upon the whole then
it is on the sarface,fit is more reasonable to suppose that the interi-
orof the earth is cdm posed of a metallic roas^ the surface of whieh
only has been fiineralized by the atmosphere!)

The eruptions of volcanoes, those stnpendoini^roblenis of natave*
admit now of %i easy explanation.* /For if the bewalsof theearlli
are the grrand recess of these newly discovered inflammable bodies,
whenever wate| penetrates into them, combustions and explosions



>Mt is alwayfreasy to form a theory. But an explanation of these
*< stupendous prablems of nature,** we believe has no^et been de-
monstrated to ib^atisfaction of all, though great learning and im*
, > . * J — ■> ■■

702. What peculiarities* have the new meUls, discovered by Sir
H. Davy?

703. What reason had Sir ; H. Davy for aupposieg the metals
might be decomposed ?

704. What are earths supposed to be?

705. What is juipposed to form tbe prinoiphd int«ipif p%rt ofv enr

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OV THE AimUCnON (fF COMPOSITION. 171

iMMt take place ; and it is remarkable that the lata whicb is thrown
oat, is tbe verjr kind of sut^tance which might be expected to re-
salt from these combostion8|

I must now take my leav/of you ; we have had a yery loni^ con-
versation to^y, and I hope you will be able to recollect what you
hare learnt.' At our next interriew, we shall enter on a new sub-
ject.



CONVERSATION XtH.

ON THB ATTRACTION OF COMPOSITION.

Jtfr#. B* Haying completed our examination of the simple or el-
ementary bodies, we are now to proceed to those of a compound
nature ; but, before we enter on this extensive subject, it will be
necessary to make jou acquainted with the principal laws by which
chemical combinations are gfoverned.

Ton recollect, I hope, what we formerly said of the nature of the
attraction of composition, or chemical attraction, or affinity, as it
is also called. ^

Emiljf. Yes, I think, perfectly ;nt is the attraction that subsists
between bodies of a different natuns, which occasions t^m to com-
bfiire and form a compound, when they come in cootao^ aind Ac-
cording to Sir H. Davy^s opinion, this effect is prod)A;ed byithe
attraction of ^opposite electricities, which prevailed in bomesof
different kindsT^

Mrs. B. Vefy well ; your definitibU condprehends the first law
of chemical attraction, which is, Xh^udtaket plaas orUy between hod-^
ittof a differetU natuinlx as, for insta(pe, between an acid and an
alkali ; between oxyflpin and a metal, &c. ^

Caroline, That we understand of course ; forahe attraction be-
tween particles of a similar nature i« (hat of aggregation, or cohe-
sion, which is independent of any chemical power.'^ ^

Mre, B. The second law of chemical attract iqifvJs, Xh^tnt takes
place ordy bettoeen the most minute particles of bodies M tberefmre, the

roense labor has been bestowed on the subject. If the ** easy ex-
planation'' is founded on the data here proposed, viz. that the solid
surface of our globe consists of notbnilg except metals and oxygen,
such a theory in the present state of knowledge, must chiefly con-
sist of supposition piled on supposition ; there being as yet no proof
that the crust of tne earth is formed only of these two elements.—
C.



706. How are volcanoes accounted fbr ?

707. What do you understand by the attraction of composition ?
70S. What cause does Sir H. I>avy assign for the attraction be-
tween bodies of a different nature ?

709. What is the first law of chemical attraction ?

710. What is the attraction between particles of a similar na-
ture called ?

711. What the second law of chemical attraction \

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172 .ON THB ATTRACTION

more you divide the particles, of tbe bodies to be combioed, the
more readily they act upon each other.

Caroline. That is again a circumstance whioh we might have in-
ferred ; for tbe ^oer the particles, of the two substances are, the
more easify and perfectly they will come in contact with each other,
which must greatly facilitate their union. It was for this purpose,
you said, thai you used iron filiogfs, in preference to wires or pieces
of iron, for t&e decomposition of water.

Mrs, B, It was once supposed that no mechanical power could
divide bodies into panicles sufficiently minute for them to act on
each other ; and that^ order to produce the extreme division re*
quisite for a cheimcalabtion, one, if not both of tbe bodies, should
be in a fluid stat^ There are, however, a few instances in whidi ,
two solid bodief^ery finely pulverized, extiit k ohemieal action on
one another ;''' but such exceptions to the gieneral rule are very
rare indeed.

Emily, In all the combinations that we have hitherto seen, one
of the cpnstitueuts has, I believe, been either liquid or aeriform.-—
In combustion, for instance, the oxygen is taken from the atmos-
phere, in which it existed in a state of ^ ; and whenever we
have s^en apids combine with metals or with alkalies, they were
either in a liquid or an aeriform state. ^

Mn. B, The third law of chemical attraction is, thairii con Ud^
place between hro, three, four^ or even a greater numb^4^ hodietS

Qarpliru, Oxyds and acids are bodies composed of two constitu-
ents, but ( recollect no instance of the conu)ination of a greater
nuinbbr qf principles.

Jurt. B, /The compound ^alts, formed bjr th^nion of the met- ,
als with acids, are composed of three principles^ And there are
salts formed by the combination or the alkalies with the earths
which are of a similar description.

Clarblinp. Are they of the same kind as the metallic salts ? .

Mrs. B. Yes ; they are very analogous in their nature, although
different in many of their properties.

At methodical nomenclature, sfmilar to that of tbe apids, has been
adopted for the comppund salts. Each individual salt derives its
name from its. constituent parts, so that every name implies a
knawledge of the composition of the salt,
^he three alkalies, the^lkalinp earths, and the metals, are catled
s^i^fiable bases or radicals^ and/the acids, scUifying prtndp/e<^ff he
name, of each salt is comfosed both of that of the acid and tbtfiaKfi-
able base ; stnd it terminates in at or it according to the degree of the
oxygenation of the acid. Thus, for instance, all those salts which
are formed by the combination pf the sulphuric acid with any of the
salifiable bases, are called sulphate, and the name of the radical is

*This is the case with muriate of ammonia and quick lime. — C«

■ — > ii 111 „ ■

712. What is necessary in order that chemical action take place
between different bodies r

713. What the third law of chemical attraction f

714. How are compound salts formed ?

716. What are called salifiable bases or radicals ?

716. What are called salifying principles ?

717. How do salts ending m ate differ from those ending in sfs ?

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or cbxposmoN. 173

idded for the specific distincUoD of the salt ; if it be potash, it will
compose a sulphat of patath ; ifamrooDia, sulphai of ammonia^ kc.
Emify, The crystals which we obtaiDcd from the combinatioa of
iron and sulphuric acid were therefore atUphat of ironS

Mri. B, Precisely ; and those which we prepared bf dissolving^
ooppflp in nitric acid, mtrat of copper^ and so on. But this is not
all ;w the salt be formed by that class of acids which end in oti#,
(wlueh joo know indicates a less degree of oxygenation) the termi-
nation of the name ^ the salt will be in t/, as sulphit qfpotath, iul"
phii of^ wnmania^ UBk

Emiiy, .IFhere mint be an immense number of compound salts,
since there is so great a variety of salifiable radicals, as well as of
sailing principles.

JIfrf. B, Their real number cannot be ascertained, since it in-
creases every day. But we must pot proceed further in the investi-
gation of the compound salts, until we have completed the exami-
nation of the nature of the ingredients of which they are composed.

The fourth law of chemical attraction is, th^fachan^fif temper-
ahire aiwaye takee place at the moment of combinati^ Imiis arises
from the extrication of the two electricities in the f<miFbf caloric,
which always occurs when bodies united and also sometimes in
part from a change of capacity in the bdflies for heat, which always
takes place when the combination is attended with an increase of
density, but moreespeciallv when the compound passes from the li-
quid to the solid form. I shall now ^how you a strikingrlnstance of
a change of temperature from chemical union, merelyn»y pouring
Bope nitrous acid on this small quantity of oil of turpentine, the oil
Will instantly combine with the oxygen of the acid, and produce a
considerable change of temperature^

Caroline. What a blaze ! The temperature of the oil and the
acid must be greatly raised, indeed, to procure such a violent com-
bustion.

Mn,B. There is, however, a peculiarity in this combustion,
which is, that the oxygen, instead of being derived from the atmos-
pheric air alone, is principally supplied by the acid itself.

Emily. Andare not all combustions instances of the change of
temperature produced by the chemical combination of two bodies ?

Jlfr#. B. Undoubtedly ; when oxygen loses its gaseous form, in
order to combine with a solid body, it becomes condeosedv^nd the
caloric evolved produces the elevation of temperature. (The spe-*
cific irravity of bodies is at the same time altered by chemi^kl com-
bination ; for in consequence of a^obange of capacity for heat a
cbangeof density must be produced^ ' ^

Caroline. That was the case witlrtne sulphuric acid and wateVt
which, by being mixed together, gave out a great deal of heat,
and increased in density.



2'?' ^97^ ^^ *®'^* ending In ic differ from those endine in eii# .'
Jl^- Whatis the fourth law of chemical attraction?
720. Prom what does the cbangeof temperature arise ?
781. What IS an instance of increase of temperature from chem-
ical unioo r

T^ Is the specific gravity of bodies affected by chemical oom*

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16*

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174 ON THE ATTRACTION

Mn, B. The fifth law of chemical altractioii is, thatwte jMropw*
ties which characterixt bofUetf when teparaUf are alter Jhr dedray*
ed by their combination^

Caroline. Certainly'^^hat, for instance, can be so different firom
water, as the hydrogen and oxygen gases ?

tUnUiy, Or what more unlike sulphat of iron* than iron or sul-
phuric acid?

Mrt. £l. 'EFory chemical combination is an illustration of this
fnle. But let us proc o^ ■

The sixth law is, t!tiaxbie/oree ff chemical aJginUy between the csn*
Hiiuenii, t^La kody^ it emmated by that which ie required far theitr
Mifd^ati(m\ This force is not always proportional to the Acifity
with #hiclAbdies unite ; for manganese, for instance, which yoa
kaow, is so much disposed to unite with oxygen, that it is nerer
foufiid in a metallid state, yields it more easiljr thanjany other metal.

Ethily, But, Mrs. B.,you speak of estimating the force of attrac-
tion between bodies, by the force required to separate them; bow
^ssuDj'ou. measure these forces ?

Mn, B» Tfae^ cannot be precisely meawred. but they are com-
paratiFcly ascertained by experiment, and can be represented by
numbers which express, at least by approximation, the relatire de-
grees of attraction. ^

The serenth law ji. thsAaodiet have amongit ihemaetoes different de-
greet of atlraelion^Wipon mis law, (which you may hare discoTer-
ed yourselTes, loifMnce,) the whole science of chemistry depends,
font is by means of the Tariou» degrees of affinity which bodies
hare for each other, ^hat all the chemical compositions and decoro-
posiUc^bsareeffectedj Eyery cheinical fact or experiment is aa
mstantfd of the samniod ; andnrhenever the decMmipositioo of a



body is performed by the addition %f any sin|^ new substance, itL
saidto TO effected by tingle eleetive attraetionr)/6nt it often happens
that no simple substance will decompose a be^, and that, in order
to effect tills, you must offer to the compound a body which is itself
oomposM of two, or sometimes three principles, which would nol»
each s^panltel^, perform the decomposition. In this case there ar«
two new compounds formed in consequence of a reciprocal decom-
position and recomposition. All instances of this kind are called
dumiie eUeiite ditriudioniS

Caroline. I confess I db not understand this clearly.

Jtfrf. J^. You wiU.easiljF comprehend it, by tbeassistanoe of this
diagram, in whichftbe teciph)cal forees of attrii^tion are represent*
edby numbersY ^

7t3. What is the fifth law of oihfimical aitractioii t .

724. What is (ne Aixth law of chemical attraicUdn t

725. What is the seventh law of chemical attraction ?

726. IJpon what does the whole science of cd^mistty depend f

727. What is a sitiiple electire sittraction ?

728. Whatisad4«ble#leeti?«attr8€tioii?



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4>F conpoftmoir.



175



Original Conmnrnd.
Sulphat of Soda.



Soda



8 Snlpharic Acid



Result.
Nitrat
of Soda



7 DiveUmt ^ JlUraeiiinii 6-13 \ -



Nitric Acid 4 Lime
Vt



RenUl.
Sulpbat
ofLimtf



Original Compound.
Nitrate of Litte.
, We here BupikM^ that we are to decompose sulphflio/soda; that
18, to separate the acid from the alkali ; if for this purpose, we add
tome Ume, in order to make it combine with the acid, we shall fail
m onr attempt, because the soda and the snlpharic acid attract each
other by a force which is superior, and, (by way of supposition) is
r^resented by the number 8 ; while the lime tends to unite with
this acid by an affinity equal only to the number 6. It is plain
therefore, that the sulphat of soda will not be decomposed, since a
force eanal to 8 cannot be orercome by a force equal only to 6.

Caroline. So far^ this appears rery clear.

Jtfrf. B, If on the other hand we endearoor to decompose this
•ah br nitric acid, which tends to combine with soda, we shall be
equally unsuocessftil, at nitric acid tends to unite with thetdkali by
a force equal only to 7. ^

In neither of these cases of simple electire attraction, therefore,
out we accomplish our purpose.. Bat let us preriously combine
tofether the lime and nitric acid, so as to form a nitrate of lime, a
compound salt, the constituents c^ which are united by a power
equal to 4. If then we present this compound to the sulphat of so.
da, a decomposition wiU ensue, because the sum of the forces which
tend to preserre the two salts in their actual state, is not equal lo
that of the forces which tend to decompose thcni, and to form new
oombinationt. The nitric acid, thet«fore« will combine with the
toda, and the tulphnrio acid with the lime.*^

« Suppose WO tay thOs. piie tulnhuric add attracis sodkiwidia
•troB^er force than it does lime, and toAihas a stronger affinity for
mOfkurie dtid than it has for nUrit oHd. It » plain then, that nei-
ther lime nor nitric add ak»e wiU decompose the sulphat of soda.
Now if we Hdte the nitric acid and lime, we form ndiraie <f tme.-^



7t9. What it represented in the diagram?

790. 7P%alifi(tMliA<4enote<y'(^fiiVee<^.ftoiKdfniMr



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j[7dr OH Tus ▲ttBAcnoir

Carniine. t mi^erstftDd you now T«ry well. This double effect
tmkes piece becaute the oumbert 8 end 4, which represent the de-
crees of attraction of the constituents of the two orig^inal salts, make
a sutn less than the numbers 7 and 6, which represent the degreee
of attraction of the two new compounds that will in cons^uence
be formed.

JUrt. B. Precisely so.

Caroline, But what is the meaning of qideiceni and divellent for-
cee, which ajee written in the diagram ?

Jtfrt. B/h^^^^^^ forces are those which tend to pMserj e com-
pounds in a state of rest, or such as they actually ara; ^rifellenC
forces, those which tend to destroy that state of commnation, and
to form new compoundni

These are the principn circumstances relatire to the doctrine of
chemical attractions, which have been laid down as rules by mod-
em chemists : a few others might be mentioned respecting the
tame theory, but of less importance, and such as would take us too
far from our plan. I should however, not omit to mention that Bfr.
Berthollet, a celebrated French chemist, has questioned the uni-
form operation of elective attraction, and has advanced the opinion
mat, in chemical combinations, the changes which take place and
The proportions in which bodies combine, depend not only upon the
affinities, but, also, in some degree, on the respectire Qualities of
the substances concerned, on Uie heat applied during the processt
and some other circumstancewi

Caroline, In that case, I suppose, there would hardly be two
compounds exactly similar, thoueh compose^ of the same materials ?

Jdrt. B. On the contrary it is found tha^remarkable uniformity
prevails, as to prcmortions, between theNngredients of bodies oif
•imilar composition^ Thus water, as you may recollect to have
seen in a former o^versation, is composed of two volumes of bj-
drogen g^ to one of oxygen, and this is always found to be precise-
ly the proportion of its constituents, from whatever source the wa* ,
ter be derived. The same uniformity prevails with re^pird to the
various salts ; the aCid and alkali, in eacn kind of salt, being always



Online LibraryMrs. (Jane Haldimand) MarcetConversations on chemistry .. → online text (page 21 of 43)