1 eq. of copper, therefore, produces 2 eq. protochloride of iron. When the copper is all dissolved, the solution is diluted and titrated with permanganate; 56 iron represent 31.7 copper.

If the original solution contains nitric acid, bismuth, or lead, the decomposition by zinc must take place in ammoniacal solution, from which the precipitates of either of the above metals have been removed by filtration; the zinc must be finely divided and the mixture warmed; the copper is all precipitated when the colour of the solution has disappeared. It is washed first with hot water, then with weak hydrochloric or sulphuric acid and water, to remove the zinc; again with water, and then dissolved in the acid and perchloride of iron as before.

e. OTHER COPPER ASSAYS, BY LEVOL, BYER AND ROBERT, RIVOT, AND WOLCOTT GIBBS.

1. Levol treats a solution of ammonio-oxide of copper, with exclusion of air, with a weighed strip of copper, by which the oxide of copper is reduced to suboxide. From the loss which the strip of copper suffers, the quantity of copper in the solution can be calculated. This assay is indeed accurate, if no other substances are present which oxidise copper, but it requires several days' time, and the copper is determined by a difference, which is always more uncertain than a direct determination.

A similar assay, in which, however, instead of an ammoniacal solution, a hydrochloric acid solution is used, has been given by Runge.

2. Robert and Byer precipitate the copper from its solution, by a simple galvanic apparatus, on a weighed plate of copper, whose increase in weight then gives the quantity of copper in the assay. The operation lasts ten to twelve hours, and no other similarly precipitable metals should be present.

3. Rivot precipitates the suboxide of copper from its solution as sulphocyanide of copper Cu,CyS, and from the weight of this salt calculates the amount of copper directly,

or after it has been converted into CuS by igniting with sulphur in a covered porcelain crucible at a red heat.

This method is indeed accurate, and generally practicable, but it requires a complete acquaintance with the analytical operations and the observance of a mass of small precautions, so that it does not differ from an analytical process.

Professor Chapman, of Toronto, gives the following directions for the detection of minute traces of copper in iron pyrites and other bodies:

Although an exceedingly small percentage of copper may be detected in blowpipe experiments by the reducing process as well as by the azure blue coloration of the flame when the test-matter is moistened with chlorhydric acid, these methods fail in certain extreme cases to give satisfactory results. It often happens that veins of iron pyrites lead at greater depths to copper pyrites. In this case, according to the experience of the writer, the iron pyrites will almost invariably hold minute traces of copper. Hence the desirability, on exploring expeditions more especially, of some ready test by which, without the necessity of employing acids or other bulky and difficultly portable reagents, these traces of copper may be detected. The following simple method will be found to answer the purpose:-The test substance, in powder, must first be roasted on charcoal, or, better, on a fragment of porcelain,† in order to drive off the sulphur. A small portion of the roasted ore is then to be fused on platinum wire with phosphor-salt; and some bisulphate of potash is to be added to the glass (without this being removed from the wire) in two or three suc

In blowpipe practice-as far, at least, as this is possible-the operator should make it an essential aim to render himself independent of the use of mineral acids and other liquid and inconvenient reagents of a similar character. If these reagents cannot be dispensed with altogether, their use, by improved processes, may be greatly limited.

In the roasting of metallic sulphides, &c., the writer has employed, for some years, small fragments of Berlin or Meissen porcelain, such as result from the breakage of crucibles and other vessels of that material. The test substance is crushed to powder, moistened slightly, and spread over the surface of the porcelain; and when the operation is finished, the powder is easily scraped off by the point of a knife-blade or small steel spatula. In roasting operations, rarely more than a dull red heat is required; but these porcelain fragments may be rendered white-hot, if such be necessary, without risk of fracture,-Canadian Journal, September 1860.

cessive portions, or until the glass becomes more or less saturated. This effected, the bead is to be shaken off the platinum loop into a small capsule, and treated with boiling water, by which either the whole or the greater part will be dissolved; and the solution is finally to be tested with a small fragment of ferrocyanide of potassium (yellow prussiate'). If copper be present in more than traces, this reagent, it is well known, will produce a deep red precipitate. If the copper be present in smaller quantity-that is, in exceedingly minute traces-the precipitate will be brown or brownish-black; and if copper be entirely absent, the precipitate will be blue or green-assuming, of course, that. iron pyrites or some other ferruginous substance is operated upon. In this experiment the preliminary fusion with phosphor-salt greatly facilitates the after solution of the substance in bisulphate of potash. In some instances, indeed, no solution takes place if this preliminary treatment with phosphor-salt be omitted.

Dr. Wolcott Gibbs recommends the electrolytic precipitation of copper and nickel as a method of analysis. He says:

The precipitation of copper by zinc, in a platinum vessel, with the precautions recommended by Fresenius, leaves nothing to be desired, so far as accuracy, ease, and rapidity of execution are concerned. The method labours, however, under a single disadvantage-the introduction of zinc renders it difficult, or at least inconvenient, to determine with accuracy other elements which may be present with the copper. It has occurred to me that this difficulty might be overcome, the principle of the method being still retained, by precipitating the copper by electrolysis with a separate rheomotor. The following numerical results, which are due to Mr. E. V. M'Candless, will satisfactorily show the advantages of the method for the particular cases in which it is desirable to employ it. The copper was in each case in the form of sulphate the deposition took place in a small platinum capsule, which was made to form the negative electrode of a Bunsen's battery of one or two cells, in rather feeble action. The positive electrode consisted of a stout platinum

wire, plunged into the surface of the solution of copper at its centre. The following table gives the results obtained in the analysis of pure sulphate of copper :

In seven determinations of copper in the alloy of copper and nickel employed by the Government for small coins the following results were obtained :

The percentage of copper required by the formula CuO, SO,+5HO is 25 42, while the Government standard alloy of nickel and copper contains 87.50 per cent. of copper. The time required for precipitation varied from one to three hours, the separation of the last traces of copper being in each case determined by testing a drop of the liquid upon a porcelain plate with sulphuretted hydrogen water. The copper after precipitation was washed with distilled water, dried in vacuo over sulphuric acid, and weighed with the platinum vessel. The only precaution necessary is to regulate the strength of the current so that the copper may be precipitated as a compact and bright metallic coating, and to dry as quickly as possible. When the copper is thrown down in a spongy condition, it not only oxidises rapidly, but it is impossible to wash out the last traces of foreign matter contained in the solution. This is well shown by No. 3 and No. 4 of the second series, in both of which cases the copper was precipitated too rapidly. The solution from which the

copper has been deposited contains the other elements. present in the original substance. It may be easily poured off without loss, and the washings added.

It appears at least probable that nickel may be determined by electrolysis in the same manner as copper, the solution employed being the ammoniacal sulphate with excess of free ammonia. Mr. M'Candless obtained in two determinations in a commercial sample 91.36 and 91.60 per cent. of nickel. In both cases the nickel was thrown down completely as a bright, coherent, metallic coating upon the platinum.

BLOWPIPE REACTIONS OF COPPER.

MINERALS OF COPPER.

SULPHIDE OF COPPER.-Alone, on charcoal, gives off sulphurous acid, fusing readily in the outer flame.

In the inner flame it is covered with a crust, and does not fuse.

In the open tube sulphurous acid is disengaged, but no sublimate is produced. The residue, treated with soda and borax, gives a button of copper.

ARGENTIFEROUS SULPHIDE OF COPPER.-Alone, fuses easily, giving off sulphurous acid. Cupelled with lead, on bone-ash, it leaves a large bead of silver, and the cupel appears a blackish green.

SULPHIDE OF ANTIMONY AND COPPER, BOURNONITE.—Alone, in the open tube, gives off the antimonial smoke, with an odour of sulphurous acid. A slip of Brazil-wood paper, on being placed within the tube, is bleached.

On charcoal, a deposit of antimony, but no trace of lead. The bead diminishes in size, becoming grey, and semi-malleable. Fused with soda, it gives a grain of copper.

COPPER PYRITES, SULPHIDE OF IRON AND COPPER.-Alone, on being heated, blackens, becomes red by cooling, and fuses more easily than the sulphide of copper, finally giving a bead attractable by the magnet. This bead is brittle, and reddish-grey in the fracture. If after a long exposure to the oxidising flame it be treated with a small quantity of borax, a regulus of copper is obtained.

BB