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absorbing more muriatic acid, slowly passes into the deliquescent muriat, which flowing into the muriatic acid is changed by the action of the immersed copper into cuprane.

M. PROUST, the first modern chemist who examined cuprane, and who is commonly considered as the first discoverer of this compound, found it produced by the action of muriat of tin on muriat of copper; he named it white muriat of copper, and ascertained that a similar substance results from the decomposition of the common deliquescent muriat by heat.

Cuprane, by whatever means prepared, possesses the same properties. It is fusible at a heat just below that of redness, and in a close vessel, or a vessel with a very small orifice, it is not decomposed or sublimed by a strong red heat; but if air, on the contrary, is freely admitted, it is dissipated in dense white fumes. It is insoluble in water. It effervesces in nitric acid. It silently dissolves in muriatic acid, from which it may be separated by the addition of water, which precipitates it unaltered; and it is decomposed by a solution of potash; or by heating it with the fused hydrated alkali: when it affords the orange oxide of copper. Its colour, transparency, and texture appear alone to vary. It is generally opaque, of a dark brown colour, and of a confused hackly texture; but I have obtained it by cooling it slowly after it has been strongly heated, of a light yellow colour, semi-transparent, and crystallized, apparently in small plates.

Cupranea is only very slowly formed by heating cuprane in chlorine gas. The best mode that I have found, of procuring it, is by slowly evaporating to dryness, at a temperature not much above 400 of FAHRENHEIT, the deliquescent muriat of copper. Thus made, it has the same appearance

and the same properties, as when directly formed. It is of a yellow colour, and pulverulent. Exposed to the atmosphere, it is converted, by the action and absorption of water, into the deliquescent muriat, and its colour, during this alteration, changes from yellow first to white, and lastly to green. It is decomposed by heat; and even in chlorine gas when the experiment is made on a pretty large quantity, part of the chlorine is expelled, and assumes the gaseous state, and cuprane

remains.

I have employed the same methods for ascertaining the proportions of the constituent parts of both these combinations. I have separated the copper by iron, and the chlorine by means of nitrat of silver.

A solution of 80 grains of cuprane in nitro-muriatic acid, precipitated by iron, afforded 51.2 grains of copper, well washed, and perfectly dried.

A solution of the same quantity of cuprane in nitric acid, précipitated by nitrat of silver, afforded 117.5 grains of horn silver dried, till it ceased to suffer any loss of weight by exposure to a temperature above 500 FAHRENHEIT.

Since horn silver contains 24.5 per cent. of chlorine,* 80 grains of cuprane appear to contain 51.2 grains of copper and 28.8 of chlorine. And 100 appear to consist of

36 chlorine
64 copper

100

• This I have ascertained by synthesis; 12 grains of pure silver dissolved in nitric acid, and precipitated with muriat of ammonia, yielded 15.9 grains of fused horn silver. I do not give the particulars of the experiment, which was very carefully made; because the result very nearly agrees with that of KLAPROTH, and of other chemists.

A solution of 40 grains of cupranea in water, acidulated with muriatic acid, precipitated by iron afforded 18.8 grains of copper.

And a solution of 20 grains of cupranea in water, precipitated by nitrat of silver, afforded 43 grains of horn silver. Hence 100 of cupranea, omitting the very slight loss, appear to consist of

53 chlorine

47 copper

100

The deliquescent muriat and the native muriat of copper of Peru, belong to a class of compounds apparently distinct from the preceding combinations of copper and chlorine.

The deliquescent salt is well understood; and its composition may be inferred, independent of its. water, from that of

cupranea.

The native muriat is less known, I shall therefore relate the experiments I have made on this interesting mineral.

The specimen I have examined is part of a very fine one, presented to Sir HUMPHRY DAVY by WILLIAM JACOB, Esq. M. P. and deposited in the Museum of the Royal Institution. It consists of muriat and carbonat of copper, of red oxide of iron, and of green-coloured quartz. The muriat is partly crystallized; the crystals, from the trials I have made of them, appeared to be pure, and they were, on that account, made the subject of my experiments.

The crystallized muriat dissolves entirely and without effervescence, in all the acids in which I have tried it, and the deliquescent muriat of copper is in each instance formed, and

a combination of brown oxide of copper with the acid employed.

Heated slowly in a bent luted glass tube, connected with mercury, the native muriat affords water and oxygene gas, and the residue is an agglutinated brownish mass, which dissolves in muriatic acid and gives a greenish precipitate with potash, and is apparently a mixture of brown oxide of copper and cuprane. When the heat is raised rapidly to redness, the water expelled is impregnated with muriatic acid, and muriat of copper. I have obtained from 25 grains of the mineral heated to redness till gas ceased to be produced, just two cubic inches of oxygene. This expulsion of oxygene seems to be owing to the action of chlorine on the brown oxide to form cuprane; and there is, I have ascertained, a similar production of oxygene when heat is applied to a mixture of the deliquescent muriat and brown oxide of copper.

From these results, which perfectly agree with those obtained by eminent chemists on the Continent, who have examined different specimens of this mineral, it appears to be a submuriat of copper, differing in a chemical point of view from the deliquescent salt, merely in containing a smaller proportion of acid.

The following experiments were made with the design of ascertaining the proportions of its constituent parts,

50 grains of the crystals in powder, boiled in a solution of 50 grains of potash, afforded 36.5 grains of brown oxide of copper heated to dull redness.

And 20 grains dissolved in nitric acid, and precipitated by means of nitrat of silver afforded 12.9 grains of dry horn silver,

Hence, considering the deficiency of weight, as indicating the quantity of combined water, 100 of the native sub-muriat of

copper seem to consist of

73.0 brown oxide

16.2 muriatic acid =

10.8 water

[blocks in formation]

This analysis, allowance being made for difference of theory, nearly agrees with that of KLAPRoth.

M. PROUST, I believe, first discovered an artificial compound similar to the native sub-muriat of copper. He obtained it, in the preparation of the nitro-muriat of copper, and also by a partial abstraction of the acid of the deliquescent muriat, by means of an alkali. I have found that it may be procured in several other ways. It may be made directly by adding the hydrated blue oxide of copper to a solution of muriat of copper; and it may be very readily and economically prepared, by exposing to the atmosphere slips of copper partially immersed in muriatic acid; and it is also produced by the exposure of cuprane to the atmosphere. Its production in the last instance is accompanied with that of the deliquescent muriat; and the formation of both seems to be owing to the absorption of water and oxygene; for cuprane, I have found, though apparently not in the least acted on by dry oxygene gas, is quickly changed when moistened with water and confined in a jar of this gas, and there is a rapid absorption of oxygene.*

I have not examined all the specimens obtained by these different methods minutely, though sufficiently, I conceive, to

* I have been informed that submuriat of copper is sometimes found in the neighbourhood of volcanoes, particularly in that of Vesuvius. By means of the above facts, it is evident that its production might be accounted for in such situations.

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