Solutions of uranyl salts (nitrate, &c.) behave to reagents as follows: sulphuretted hydrogen produces green uranous salt with precipitation of sulphur; sulphide of ammonium in neutral solutions gives a black precipitate of UO 2 S, which settles slowly and, while being washed in the filter, breaks up partially into hydrated UO 2 an sulphur; ammonia gives a yellow precipitate of uranate of ammonia, characteristically soluble in hot carbonate of ammonia solution; prussiate of potash gives a brown precipitate which in appearance is not unlike the precipitate produced by the same reagent in cupric salts.
Potassium ferrocyanide, K 4 Fe(NC) 6, (yellow prussiate of potash), was first obtained by decomposing Prussian blue with caustic potash: Fe4[Fe(NC)6]3 + 12KHO = 3K 4 Fe(NC) 6 +4Fe(OH) 3; it may be also obtained by warming a solution of ferrous sulphate with an excess of potassium cyanide: FeS04-I-6KNC = K4Fe(NC)6+ K2S04.
Potassium ferricyanide, K 3 Fe(NC)s, red prussiate of potash, is obtained by oxidizing potassium ferrocyanide with chlorine, bromine, &c., 2K 4 Fe(NC) 6 + C1 2 = 2K 3 Fe(NC) 6 + 2KC1.
For his time he was a skilful chemical analyst; he knew how to distinguish potash and soda by the different colorations they produce in flame, and how to test for iron with prussiate of potash: he was aware that sulphate of potash, gypsum and heavy spar, in spite of their different appearances, all contain sulphuric acid; and he recognized that there are different varieties of urinary calculi.
Cyanogen compounds also are present in the gas, and in large works, where the total quantity is sufficient, their extraction is effected for the production of either prussiate or cyanide of soda.