Progress of Foreign Science. 319 



acid soUilion of gold treated with potash, was considered by M. 

 Pelletier as a mere mixture of the two chlorides. By evapo- 

 rating a mixture of the muriate of gold and muriate of potash, 

 M. Javal obtained crystals of a fine golden yellow, having the 

 form of elongated quadrangular prisms. These crystals did 

 not lose their colour by washing ; on the contrary, they con- 

 tinue to possess the colouring power in a very high degree. M. 

 Javal afterwards analyzed these crystals, and found them com- 

 posed as follows : 



Chloride of potassium 24.26 1 atom by Berzelius 25.21 



of gold . . 68.64 2 atoms .... 68.71 



Water 7.10 2 atoms .... 6.08 



100.00 100.00 



Mr. Grouvelle, (not Granville, as misprinted in the last 

 Number of our Journal, p. 174), has published in the Annales 

 de Chimic et de Physique for last August, a paper on some 

 compounds of chromium, and on several combinations, in 

 which one of the elements enters only in a very small propor- 

 tion. He says that bichromate of potash, when calcined 

 strongly, melts, and passes to the state of neutral chromate, 

 giving up the half of its acid which is decomposed, and leaves 

 a crystallized oxide of chromium in spangles of a magnificent 

 green colour. The neutral chromate obtained was analyzed by 

 a solution of sulphurous acid, which converts it instantly into 

 sulphate of potash, sulphate and sulphite of chronium. The 

 metallic oxide was precipitated by anmionia, and the sulphate 

 of potash evaporated. 



M. Grouvelle says, that Vauquelin, by pouring sulphuric 

 acid and potash into chromic acid, obtained a brown preci- 

 pitate, which he regarded as an oxide of chromium, with 

 more oxygen than the green oxide. It is not, says M. 

 Grouvelle, an oxide, but a carbonate of chromium. Surely then 

 it must have been a carbonate of potash which M. Vauquelin 

 employed. It dissolves, he adds, with cttervescence in di- 

 lute acids. When boiled in distilled water, it is decomposed, 

 and we obtain green oxide, and carbonic acid. Consequently, 

 we must avoid washing it with hot water. 



We can also obtain this carbonate of chromium, by eva- 

 porating to dryness, a mixture of nitrate of ammonia, chromate, 

 and carbonate of potash, or of muriate of annnonia, and an 

 alkaline nitrate, carbonate, and chromate. The matter dried 

 at a gentle heat blackens. It is to be re-dissolved in water, 

 and a drop of water of ammonia is to be poured in, to se[)arate 

 a small quantity of carbonate of chromium, which, he believes, 

 the nitrate of ammonia had rendered soluble. If it be loo 

 Hlrougly heated, the excess of nitrate would re-produce sonu: 

 cliruaiulc. Here it is the protoxide of azote in the nascent 



