which fully coincide with his. The formula of this body is Pd Cl + 2 NH3 + HO, or rationally, according to the principles I have elsewhere laid down for the copper salts, N H1. Cl + Pd O. N H3. When gently heated it evolves water and ammonia, and leaves the yellow substance Pd Cl + N H3. The same decomposition may be effected by evaporating its solution to dryness, in which case the yellow salt generally crystallizes in cubes. Were it not hazardous to draw any inference with regard to the isomorphism of bodies belonging to the regular system, I should notice this fact as illustrative of the equivalency of Pd Cl. N H, with K. By a very cautious application of heat to the colourless crystallized salt, some water may be expelled before the ammonia begins to come off, but I have never succeeded in rendering it quite anhydrous. It however partially assumes the formula N H. Cl + Pd. N H2, to which we shall find the ammonia-sulphate of palladium to present an equivalent.

3

By the action of solutions of caustic potash, on solutions of these ammonia-chlorides of palladium, a variety of products are formed, according to the proportions employed and the circumstances of temperature. For the complete investigation of these bodies I have not yet accumulated materials, but the results which have been already obtained, are not without interest as indicative of the analogies of palladium to other metals whose laws of combination are better known. I shall consequently describe those substances 1 have as yet examined, although I intend to resume and extend their investigation before long.

A. When the pink-red precipitate is boiled with a large quantity of water it dissolves, and on cooling but little of the isomeric yellow salt crystallizes out. On adding to the brownish yellow liquor so obtained a solution of caustic potash not in excess, a yellowish precipitate falls, which by boiling becomes brown red, and distinctly crystalline. If the pink red substance (Pd Cl + N H2) be dissolved in the hot water without much boiling, there is generally no precipitate on adding the caustic potash, and the solution is merely yellow, not brownish coloured. It appears necessary that by the boiling, partial decomposition should occur, and some ammonia be expelled to bring the liquor to the state suitable for the action of the caustic potash. This may also be effected by adding to the solution of the ammonia-chloride some solution of protochloride of palladium, so as to have in solution apparently a substance containing Pd Cl + Pd Cl. N H3, which is not known in the solid form.

The yellow precipitate which first falls is the ordinary crystalline body Pd Cl + N Ha, but by boiling in the liquor from which it has separated, its nature is completely changed. The properties of the crystalline brown red substance then produced are, that it dissolves

readily in muriatic acid, and gives by heat, sal-ammoniac, nitrogen, and water, and leaves metallic palladium. Its composition was determined by analysis to be us follows:

I. 14.601 grains having been ignited to perfect fusion with carbonate of soda, gave, when the saline material was dissolved in water, 8.072 grains of palladium, or 55 28 per cent.

The solution acidulated with nitric acid and precipitated by nitrate of silver, gave 14.802 grains of chloride of silver, equivalent to 101.4 per cent., containing 25.03 of chlorine.

II. 7.964 grains of substance, gave by the method pursued in similar instances, 3.3907 cubic inches of nitrogen, at a standard temperature and pressure. These weigh 1080 grains, equal to 13.64 per cent.

III. 9.231 grains of substance having been mixed with dry carbonate of soda, were introduced into a tube of Bohemian glass, and some pieces of platina foil being interposed, about four inches of the tube in front of the mixture were filled with oxide of copper. To this apparatus was adapted a tube containing recently fused chloride of calcium, and the whole being disposed and heated exactly as for an organic analysis, it yielded 3.212 grains of water, being 34.78 per cent., containing 3.85 of hydrogen.

After this operation, the tube being cut by a file, that portion of it which contained the saline mass was digested with dilute nitric acid, and the metallic palladium collected on a filter. It weighed 5.170 grains, or 56.02 per cent.

The solution treated in the usual way, gave 9.337 of chloride of silver, or 101.2 per cent., containing 24.92 of chlorine. The summary of these results is

The deficiency in the sum of the preceding results being counted as oxygen, these numbers lead to the formula Pd, Cl, O N, H,, which gives

3. Pd

159.9

55.20

24.44

2.76

3.10

14.50

100.00

This body may be considered as a compound of ammonia-chloride, with ammonia-oxide of palladium: thus 2 (Pd Cl. NH3) + PdO.NH,, and its origin explained, by an atom of potash producing with three atoms of ammonia-chloride, it and chloride of potassium, for 3 (Pd Cl. NH1)

3

and K O give Pd, Cl, O N, H, and K Cl. I shall, however, return to the notice of its rational constitution when the next substance has been described.

B. When the same kind of palladium liquid from which the brown red substance last noticed is prepared, is heated with an excess of solution of caustic potash in the cold, a whitish powder falls, which on drying, even by a very gentle heat, becomes dark olive coloured. If it be boiled its colour changes to yellow, and is then found to be identical with the yellow crystalline body (Pd Cl. N H2) which makes its appearance under such various circumstances. This olivecoloured substance when heated evolves water and vapours of salammoniac, leaving metallic palladium. Its analysis gave the following results:-

12.224 grains gave, by fusion with carbonate of soda and decomposition by nitrate of silver, in the usual manner, 8.242 grains of metallic palladium, equivalent to 67:43 per cent., and 5.938 grains of chloride of silver, being 48.48 per cent., containing 11.96 per cent. of chlorine.

12.113 grains, heated with oxide of copper as for an organic analysis, gave 2:423 of water, being 20:03 per cent., containing 2.22 per cent. of hydrogen.

Hence the formula expressing the composition of this body appears to be Pd, Cl N O, H., the numbers being

I regret very much that the quantity of this substance at my disposal did not allow me to make a distinct nitrogen determination at the time of the above analysis, and the difficulty of procuring either this or the preceeding (A. red brown) body quite free from the crystalline yellow substance being very great, I have not had a subsequent opportunity. I shall however return to it, although I consider the arguments which might be brought forward in favour of the formula just now given to be very decisive for its reception indeed no other formula that can reasonably explain the circumstances of the production of this body, agrees with the numerical results of its analysis.

This empirical formula assumes more interest when rationally expressed it becomes Pd Cl + 3 Pd O + N H3 + 3 H O. It therefore consists of the ordinary oxychloride, with an atom of

ammonia in place of one atom of its water of hydration, or it may be written Pd Cl. N H, + 3 (Pd O. H O), being a compound of ammonia-chloride and hydrated oxide. But it is more consonant to analogy to consider it as containing a metallic amidide, and its formula is then written Pd Cl + 2 . Pd O + Pd N H2 + 4 H O. It is thus the perfect analogue to the yellow powder produced by the action of water on the white precipitate of mercury, except that like all the copper and palladium bodies, it is hydrated, while the corresponding mercurial compounds are anhydrous. Such I consider to be the real constitution of this olive powder, and by our knowledge of its existence we are enabled to view the other ammonia-chlorides of palladium more intimately than previously had been possible. Thus, the change of the pink ammonia-chloride to the yellow, must, as I conceive, be attended with an alteration in the mode of combination of its elements. The pink body is formed only by the direct union of ammonia with chloride of palladium. It appears to be truly and simply Pd Cl + N H3; but the yellow crystalline substance is produced only by processes in which the palladium has certainly passed, at least in a great degree, from union with chlorine, and has combined with oxygen or amidogene. It is hence most probable that the yellow substance cannot also be simply Pd Cl + N H3. The arrangement of its elements may be expressed by the formula H Cl+Pd. N H2, or else there may exist for palladium a compound analogous to the mercurial white precipitate, its formula being Pd Cl + Pd N H2, and this combined with sal-ammoniac may form the yellow substance, precisely as the true white precipitate (Hg Cl + Hg. Ad) by union with sal-ammoniac, forms Wöhler's white precipitate, the composition of which, as I have elsewhere shown, is expressed by the simple formula Hg Cl + N H3.

C. By boiling a solution of the colourless crystalline ammoniachloride of palladium (Pd Cl + 2 N H3 H O) with caustic potash in excess for a long time, an olive-green powder falls, which when heated deflagrates like loose gunpowder. A quantity of it which I had prepared for analysis, and incautiously heated, was thus lost, and I can therefore merely indicate the existence of this body, and defer the exact account of it to a future time.

In the memoir already often alluded to, Fehling has noticed that, on dissolving the pink ammonia-chloride in boiling water, a small quantity of a brown powder is sometimes left undissolved, and on analysing it (determining only the content of metal and chlorine,) he deduced that it had the formula Pd, Cl + 3 N H3. He remarks, however, that the origin of a body having that formula, is under the circumstances incomprehensible; it indeed assumes the existence of a peculiar chloride of palladium for which there is no other evidence whatsoever. I have on two occasions examined this trace of brown matter, and found its composition variable, and that it contains oxygen, as it evolves water when heated. It is most probable that the ammonia-chloride is partially decomposed by water into the olive

body (B.) and sal-ammoniac, thus 4 (Pd. Cl. N H1) and 2. HO give Pd, Cl O, N H2, and 3 N H, Cl, and that this olive substance (hydrated) combines with a certain quantity of ammonia-chloride, undecomposed, or is more probably but mixed with it. The formula Pd, Cl3 N3 H15 O12 Pà. Cl. N H, + 2 (Pd, Cl N H 06) gives

=

very accurately the result obtained by Fehling.

It may be remarked, however, that another and very interesting formula expresses the composition of Fehling's substance. It is this: Pd, Cl N, H6 O2, or rationally, Pd Cl + 2. Pd N H2 + 2 Aq. This gives

Theory.

Fehling.

It should then be an oxychloride of palladium united to ammonia, or a hydrated chloramidide of palladium, analogous in constitution to the very peculiar oxychloride of copper, Cu Cl + 2 Cu O, which I have elsewhere described.

The observations I have had occasion to make respecting the iodides and cyanide of palladium, and the bodies derivable from them, agree perfectly with those obtained by Fehling, and published in the memoir to which I have so often had occassion to refer, on the relation of the haloid compounds of palladium to ammonia, inserted in Liebig's "Annalen der Chemie und Pharmacie." I deem it hence unnecessary to notice any of those results in detail, as they already have been placed before the public.

Of the Sulphates of Palladium.

The sulphate of palladium is best prepared by dissolving the metal in a mixture of sulphuric acid and nitric acid, the former being in excess, and evaporating the deep brown red liquor so obtained to the consistence of a syrup. On cooling, it crystallizes, though very confusedly, and only when so concentrated as to become always completely solid.

In this state it tastes sour and metallic. It is reddish brown coloured, very soluble in water, and in damp air deliquescent. It contains water of crystallization. Its composition was determined as follows:

45.286 grains of the crystalline mass, dried between folds of bibulous paper, were heated cautiously as long as any traces of moisture were given off. The residual mass weighed 38 124 grains, or 84.19 per cent., having lost 15.81 per cent of water.

Of the material so dried, 32:043 grains were fused with carbonate