1819.] the Turquoise a?id the Calaite. 413 



a. Two hundred parts of the mineral in fine powder were 

 mixed with 10 times their weight of nitric acid, and subjected 

 to ebullition for an hour. The mixture diluted with water and 

 filtered left a brownish-grey powder on the filter. After washing 

 and drying it, I put it aside for further experiments. 



b. The nitric acid solution being evaporated to dryness, and 

 the residue redissolved in water, left about one part of silica. 

 The solution was divided into two parts. 



c. A polished plate of iron plunged into one of these parts 

 precipitated in a dendritical form 3-i- gr. of copper. 



d. The solution freed from copper was boiled with an excess 

 of caustic potash. After having washed and dried the resulting 

 precipitate, I obtained oxide of iron which contained a trace of 

 alumina. 



e. The liquid remaining from d having been saturated with 

 nitric acid was decomposed by carbonate of ammonia. The 

 earth precipitated in this way was separated from the liquid by 

 filtration. Being redissolved in sulphuric acid, and mixed with 

 a little potash by evaporation and crystallization, pure alum was 

 obtained. 



f. After having boiled the other half of the solution with 

 caustic potash, a dark-brown precipitate fell, which was washed 

 and dried, and digested for an hour in nitric acid. There 

 remained one grain of oxide of iron. 



g. After saturating the blue liquid thus freed from iron with 

 ammonia, M. John added to it prussiate of potash. A brick-red 

 precipitate fell, which, being washed, dried, and calcined, 

 weighed 4-i- gr. and consisted of oxide of copper. If we subtract 

 the small quantity of iron shown to exist in this precipitate by 

 prussiate of potash, the true weight of the oxide of copper will 

 be 4-1, corresponding to the 3i of copper above-mentioned. 



h. The hquid freed from copper was neither altered by oxalic 

 acid nor by the carbonate of potash. 



i. The alkaline lixivium /was saturated with nitric acid, and 

 decomposed by carbonate of ammonia. The earth precipitated 

 in this way was separated from the liquid by the filter. After 

 being washed and calcined, it weighed 70 gr. and was alumina. 



k. The residue remaining from a was boiled with caustic pot- 

 ash. The mixture being diluted with water, then dissolved in 

 nitromuriatic acid, evaporated to dryness, and redissolved in 

 water, left a powder, which, being collected on the filter, washed, 

 and calcined, weighed l-±- gr. It was silica proceeding from the 

 pulverisation of the turquoise in the mortar. 



/. On adding caustic ammonia to the nitromuriatic acrd solu- 

 tion, a gelatinous precipitate fell, which, being collected on the 

 filter and washed, was boiled with caustic potash. In that way 

 three grains of oxide of iron were obtained. 



m. The alkaline ley being saturated with an acid and decom- 



