Raymond says that the nitrate of lead is decomposed by phosphuretted hydrogen water, but with less force than salts of silver and mercury; and that a phosphuret of lead is formed, of which he gives no character, except that it becomes in time a phosphate. Thomson says a slight white powder is formed by the mixture. This was the case with me; but I suspected that the white powder was merely a little sulphate of lead, arising from the impurity of the (rain) water; and this was found to be the fact; for the milkiness was just the same with like water unimpregnated with the gas. Besides, after the phosphuretted hydrogen water has been saturated with nitrate of lead till no more effect is produced, still the water retains its peculiar smell, and a copious black precipitate is instantly produced by nitrate of silver or mercury. It appears then that phosphuret of lead cannot be formed this way. Neither does phosphuretted hydrogen water seem to have any effect on the recently precipitated oxide of lead. 17. _Phosphuret of zinc._ Both zinc and its oxide seem to combine with phosphorus, according to Pelletier; but the proportions were not ascertained. By theory, zinc should take 32 per cent. of phosphorus. 18. _Phosphuret of potassium._ Some account was given by Davy, of the combination of potassium and phosphorus in essays from 1807 to 1810; and by Gay Lussac and Thenard in others from 1808 to 1811. According to Davy, when potassium and phosphorus are heated together, they combine in one uniform ratio of 8 to 3 nearly; and the compound, when acted upon by muriatic acid, gives out from .8 to 1 cubic inch of phosphuretted hydrogen gas, resulting from one grain of the former and ⅜ of a grain of the latter substances combined. Also be observed that half a grain of potassium decomposed nearly 3 cubic inches of phosphuretted hydrogen, and set free more than 4 cubic inches of hydrogen; the phosphuret seemed to be of the same kind as the former, or that by direct combination of the two elements. Gay Lussac and Thenard combined the elements by heat; the potassium is scarcely fused till the phosphuret is formed. The excess of phosphorus sublimes, and the phosphuret is always of a chocolate colour; the proportions were not ascertained. By treating this phosphuret with warm water, a quantity of phosphuretted hydrogen was uniformly given out, about 40 per cent. more than the hydrogen which would have been yielded by the potassium alone in water. But if the phosphuret was treated with dilute acid instead of water, then less gas was given out than otherwise; and the stronger the acid the less gas, so as sometimes to reduce the gas in volume to that yielded by potassium alone. They also found, as Davy had done, that potassium heated in phosphuretted hydrogen decomposed it, uniting with the phosphorus and producing the same compound as in the direct way.