Conversations on Chemistry Part 2

PHOSPHORUS, _forming_ phosphoric acid.

CARBON, _forming_ carbonic acid.

BORACIUM, _forming_ boracic acid.

FLUORIUM, _forming_ fluoric acid.

MURIATIUM, _forming_ muriatic acid.

DIVISION 3.

_Metallic bodies forming alkalies._

POTa.s.sIUM, _forming_ potash.

SODIUM, _forming_ soda.

AMMONIUM, _forming_ ammonia.

DIVISION 4.

_Metallic bodies forming earths._

CALCIUM, _or metal forming_ lime.

MAGNIUM, _forming_ magnesia.

BARIUM, _forming_ barytes.

STRONTIUM, _forming_ stront.i.tes.

SILICIUM, _forming_ silex.

ALUMIUM, _forming_ alumine.

YTTRIUM, _forming_ yttria.

GLUCIUM, _forming_ glucina.

ZIRCONIUM, _forming_ zirconi.*

[Footnote *: Of all these earths, three or four only have as yet been distinctly decomposed.]

DIVISION 5.

_Metals, either naturally metallic, or yielding their oxygen to carbon or to heat alone._

_Subdivision 1._

_Malleable Metals._

GOLD, PLATINA, PALLADIUM, SILVER*

MERCURY TIN, COPPER, IRON, LEAD, NICKEL, ZINC.

[Footnote *: These first four metals have commonly been distinguished by the appellation of perfect or n.o.ble metals, on account of their possessing the characteristic properties of ductility, malleability, inalterability, and great specific gravity, in an eminent degree.]

[Footnote : Mercury, in its liquid state, cannot, of course, be called a malleable metal. But when frozen, it possesses a considerable degree of malleability.]

_Subdiv. 2._

_Brittle Metals._

a.r.s.eNIC, BIs.m.u.tH, ANTIMONY, MANGANESE, TELLURIUM, COBALT, TUNGSTEN, MOLYBDENUM, t.i.tANIUM, CHROME, URANIUM, COLUMBIUM _or_ TANTALIUM, IRIDIUM, OSMIUM, RHODIUM.*

[Footnote *: These last four or five metallic bodies are placed under this cla.s.s for the sake of arrangement, though some of their properties have not been yet fully investigated.]

CAROLINE.

Oh, what a formidable list! You will have much to do to explain it, Mrs. B.; for I a.s.sure you it is perfectly unintelligible to me, and I think rather perplexes than a.s.sists me.

MRS. B.

Do not let that alarm you, my dear; I hope that hereafter this cla.s.sification will appear quite clear, and, so far from perplexing you, will a.s.sist you in arranging your ideas. It would be in vain to attempt forming a division that would appear perfectly clear to a beginner: for you may easily conceive that a chemical division being necessarily founded on properties with which you are almost wholly unacquainted, it is impossible that you should at once be able to understand its meaning or appreciate its utility.

But, before we proceed further, it will be necessary to give you some idea of chemical attraction, a power on which the whole science depends.

_Chemical Attraction_, or the _Attraction of Composition_, consists in the peculiar tendency which bodies of a different nature have to unite with each other. It is by this force that all the compositions, and decompositions, are effected.

EMILY.

What is the difference between chemical attraction, and the attraction of cohesion, or of aggregation, which you often mentioned to us, in former conversations?

MRS. B.

The attraction of cohesion exists only between particles of the _same_ nature, whether simple or compound; thus it unites the particles of a piece of metal which is a simple substance, and likewise the particles of a loaf of bread which is a compound. The attraction of composition, on the contrary, unites and maintains, in a state of combination, particles of a _dissimilar_ nature; it is this power that forms each of the compound particles of which bread consists; and it is by the attraction of cohesion that all these particles are connected into a single ma.s.s.

EMILY.

The attraction of cohesion, then, is the power which unites the integrant particles of a body: the attraction of composition that which combines the const.i.tuent particles. Is it not so?

MRS. B.

Precisely: and observe that the attraction of cohesion unites particles of a similar nature, without changing their original properties; the result of such an union, therefore, is a body of the same kind as the particles of which it is formed; whilst the attraction of composition, by combining particles of a dissimilar nature, produces compound bodies, quite different from any of their const.i.tuents. If, for instance, I pour on the piece of copper, contained in this gla.s.s, some of this liquid (which is called nitric acid), for which it has a strong attraction, every particle of the copper will combine with a particle of acid, and together they will form a new body, totally different from either the copper or the acid.

Do you observe the internal commotion that already begins to take place?

It is produced by the combination of these two substances; and yet the acid has in this case to overcome not only the resistance which the strong cohesion of the particles of copper opposes to their combination with it, but also to overcome the weight of the copper, which makes it sink to the bottom of the gla.s.s, and prevents the acid from having such free access to it as it would if the metal were suspended in the liquid.

EMILY.

The acid seems, however, to overcome both these obstacles without difficulty, and appears to be very rapidly dissolving the copper.

MRS. B.

By this means it reduces the copper into more minute parts than could possibly be done by any mechanical power. But as the acid can act only on the surface of the metal, it will be some time before the union of these two bodies will be completed.

You may, however, already see how totally different this compound is from either of its ingredients. It is neither colourless, like the acid, nor hard, heavy, and yellow like the copper. If you tasted it, you would no longer perceive the sourness of the acid. It has at present the appearance of a blue liquid; but when the union is completed, and the water with which the acid is diluted is evaporated, the compound will a.s.sume the form of regular crystals, of a fine blue colour, and perfectly transparent*. Of these I can shew you a specimen, as I have prepared some for that purpose.

[Footnote *: These crystals are more easily obtained from a mixture of sulphuric with a little nitric acid.]

CAROLINE.

How very beautiful they are, in colour, form, and transparency!