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On heating this body it gives off ammonia with fumes of iodine and of hydriodate of ammonia: water also separates. It may, however, be exposed to a temperature of 350° Fahr. without losing water, which does not escape until complete decomposition has commenced.

The analysis of this body was effected as follows :

32.490 grains were fused with carbonate of soda, and the residual mass digested in water. The platinum which remained behind weighed 12.472, or 38:01 per cent.

The alkaline solution being rendered acid by acetic acid, was decomposed by nitrate of silver. The iodide of silver, being collected, dried and weighed, was 29.295 grains, or 89.8 per cent., containing 48.37 of iodine.

47.226 grains, ignited with oxide of copper in the manner already described, gave 9.215 cubic inches of dry nitrogen, equivalent to 6.26 per cent. in weight.

44-468 grains, ignited with oxide of copper, gave 4.584 of water, equivalent to 1.15 of hydrogen per cent.

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These results lead directly to the formula Pt IN H, O.. or Pt O, NH,.I., for which the numbers are

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The hydrogen being found below the quantity assigned by theory, I endeavoured to ascertain whether a portion of it could be eliminated as water, and I exposed a quantity of the substance to a current of dry air at 300° Fahr. until all traces of water ceased to pass. The quantity of water which escaped was 1.95 per cent. If this were not hygrometric, the formula of the dry substance should be Pt I+Pt O2 + 2. NH3. and the hydrogen should be 1.20 per cent., nearly what was furnished by analysis. The specimen analysed for hydrogen was probably so dried.

It is interesting to and here the form assumed by the ammoniacal compounds of quicksilver, but still hydrated, and so rendered much more complex. It is curious also to recognise in the two hydrated states of this red platinum body, the analogues to the two formulæ assigned to the mercurial white precipitate before its true constitution was known. Thus Pt O2+NH,. I. corresponds to the formula Hg 0 + NH, Cl given by Mitscherlich, and Pt I + Pt O2+2. NH, is equivalent to that suggested by Mr. Richard Phillips, Hg Cl + Hg O2+ 2. NH3. I do not believe, however, that the perfectly anhydrous condition of white precipitate can be given to this platinum body.

On the Action of Ammonia on the Perchloride of Platinum.

A. When a dilute solution of perchloride of platinum is added to water of ammonia, also dillute, a pale yellowish precipitate is produced, insoluble in cold water, but decomposed by boiling water, or even by much washing; the double chloride of platinum and ammonia being dissolved out, and the colour of the residue becoming much less yellow.

When this powder is heated it gives out sal-ammoniac, chlorine, nitrogen, and leaves metallic platinum. No trace of water appears: it hence does not contain ogygen as a constituent. With muriatic acid it is changed into the common double chloride of platinum and ammonium.

This substance was analysed as follows:

21.098 grains were carefully mixed with an excess of carbonate of soda, and ignited until the mixture was completely fused. The saline matter was then dissolved out with distilled water, and the metallic platinum remaining being collected and ignited, weighed 10.881 grains, 51.6 per cent.

The solution having been acidulated by nitric acid was precipitated by nitrate of silver, the chloride of silver produced was collected and fused, it then weighed 18.521, equivalent to 38.8 of chlorine per cent.

45.332 grains of another quantity, treated in a precisely similar way, gave 23.614 of platinum, 52.1 per cent., and 70.151 of chloride of silver, equivalent to 38-20 of chlorine per cent.

These results indicate for the composition of this substance the very simple formula Pt Cl2 + N H3, which gives the numbers

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From the circumstance of no water being produced when this body is decomposed by heat, and the relation between the chlorine and platinum showing that these constituents are directly combined, the loss must necessarily be nitrogen and hydrogen in the proportions to form ammonia. This constituent, therefore, was not directly estimated; the analysis showing that the brownish yellow powder consists of an equivalent of perchloride of platinum united to an equivalent of ammonia.

This substance is by no means always formed by the action of water of ammonia upon a solution of chloride of platinum; on the contrary, it is difficult to obtain it unless by using both solutions very weak, and by having the platinum quite free from muriatic acid in excess. In the great majority of cases, this first product is

either rendered impure by the passage of a portion into the second stage of the reaction, or else by the precipitation of the double chloride of platinum and ammonium which is generated at the same time. With moderately weak solutions, the platinum being in excess, and avoiding too much washing of the precipitate, the substance may generally be obtained pure.

B. When the solutions of chloride of platinum and ammonia are boiled together, the precipitate rapidly assumes a remarkable fawn colour. In this state it is insoluble in water. It dissolves in muriatic acid, producing a yellow liquor. When heated, it gives off chlorine and muriatic acid gases, water, a trace of sal-ammoniac, and leaves metallic platinum.

The analysis of this body was effected as follows:

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I. 27.999 ignited with an excess of carbonate of soda, gave by the same mode of treatment as that described in paragraph a, 12·332 of platinum, being 44.24 per cent., and 47.365 of chloride of silver, equivalent to 41.94 in 100.

For the determination of the hydrogen and nitrogen, the same methods were employed as in the analyses of organic bodies, and the details of which need not be inserted.

20 064 grains burned with oxide of copper, gavc 19.386 of water, or 2.17 per cent. of hydrogen.

20.049 grains of substance produced 4.29 cubic inches of dry pure nitrogen, equivalent at standard temperature and pressure to 1.420 grain, or 7.09 per cent.

II. Another quantity of substance prepared at a different time and at a much lower temperature, gave the following result :

23.599 grains ignited with carbonate of soda, gave by treatment with nitric acid and nitrate of silver 40.223 chloride of silver, equi.. valent to 41.20 of chlorine per cent., and left 10.507 of platinum, equal to 44-47 in 100.

The hydrogen being determined, as in the former case, there was obtained from 24.925 grains of substance 5.170 of water, equivalent to 2.30 of hydrogen per cent..

In this instance the nitrogen was not determined. The formula to which these results lead is very remarkable, and will hereafter give origin to some observations; for the present I shall only put it forward in a purely empirical form, as follows: Pt, Cl5 H11 N2 O4, which gives the following numbers :

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III. The substance used in analysis No. I. was again boiled for a short time in water of ammonia, but without allowing the colour to become perceptibly altered, it was then dried at a temperature of 120°, and analysed.

14.462 grains of substance gave, by the usual treatment 6·467 of metallic platinum, equivalent to 44.72 per cent., and 23.799 of chloride of silver, equivalent to 40'61 of chlorine.

24.139 grains of substance burned with oxide of copper gave 4.799 of water, or 2.21 of hydrogen per cent. 27.968 gave, by the usual method, 5.602 cubic inches of pure dry nitrogen, weighing at standard temperature and pressure 1.7961 grain, and hence equivalent to 6.44 per cent.

The experimental results are hence as follows:

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It is very remarkable that in all these results the chlorine appears to be a little (about 1 per cent.) above the theoretical number; this is perhaps due to the presence of traces of the double chloride of platinum and ammonium, which, from its sparing solubility, if once formed is very difficult to be removed, and is not changed, except when the accompanying bodies are also decomposed. The composition of this substance is, however, evidently the same, although prepared under varied circumstances; and it may also be produced, even in the cold, by allowing chloride of platinum to remain in contact with an excess of water of ammonia for a considerable time.

When this substance is heated to about 250° or 300° it abandons some water, but no ammonia. The quantity of water thus given off, was found to be 2.57 per cent. By the loss of one equivalent it should be 2 per cent., and hence probably the perfectly dried substance has the composition of Pt2 Cl5 N2 H10 O3.

The formula of this body presents a remarkable relation, which may be at the present moment noticed. It may be considered as the ordinary double chloride of ammonium and platinum, Pt Cl + NH Cl, united to a compound of chloride of platinum and oxide of ammonium, and then two atoms of water added. Thus

Pt. Cl2+ NH, CN

Pt. Ch+NHOS + 2 Aq = Pt2 Cls N2 H10 O2.

Whether this be its true constitution will be discussed in the sequel. It may be also composed of the chloride of platinum and ammonium united to the body described in paragraph A., and to water.

Thus

Pt Cl2+N H. CI.

Pt Cl2 + NH3

Ptą Cls N2 H11 04.

H4 04

This is a more likely supposition than the former.

C. When the fawn-coloured substance last described is continually boiled in water of ammonia, it ultimately dissolves, but it may be observed to become dark brown before it disappears. This brown substance dissolves almost as soon as formed, and hence it is difficult to obtain a quantity of it for analysis; even a large quantity of chloride of platinum yielding by the action of ammonia only traces of it. This brown powder is not acted on by boiling water. With muriatic acid, it partly dissolves, giving a yellow liquor, and is partly converted into a white powder, sparingly soluble in water.

When heated it gives off sal-ammoniac, water and nitrogen, and metallic platinum remains. To determine the composition of this substance the same methods of analysis were used as in the former

cases.

21.608 grains ignited with carbonate of soda, gave 13.455 of platinum, or 61.80 per cent., and then 9.939 of chloride of silver, corresponding to 11.35 of chlorine in 100.

23.799 grains gave, by ignition with oxide of copper, 7.085 of water, indicating 3.31 per cent. of hydrogen.

14.663 grains gave 6.2247 cubic inches of pure nitrogen reduced to 30 inches barometer and 32° Fahr., indicating 13.50 per cent. in weight.

The formula to which this analysis leads is remarkable; it is Ptą CI N3 H10 04, which gives the following numerical results :

Two equivalents of platinum.... 197'6

62.28

61.80

One equivalent of chlorine.....

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The specimen employed in the above analysis had been dried at a temperature of 310°, and had lost a quantity of water which it retains when dried at lower temperatures; the quantity of water thus loosely combined was found to be three equivalents.

When we look to the constitution of the formula just described, we may probably consider the chlorine to exist as sal-ammoniac, and then combined with an ammonia oxide of platinum, such as is found really to exist; thus the formula may become

2 (Pt O2 + NH3) + CIN H..

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