Mil. Ti:\nent on the Yellow Pruswite of Potash Cake. ttl 



the tube containing the acid. After the action had completely ceased, 

 the cork was removed from the flask for a short time, so that the carbonic 

 acid remaining in the tube might mingle with the air, and thus be expelled 

 from the flask. It was then weighed. The loss in weight was 4 # 61 grains 

 = 9*22 grains per cent, from the expulsion of carbonic acid, equivalent 

 to 29.3 carbonate of potash in 100 parts of the cake. 



2. Estimation of the Caustic Potash. — 50 grains were treated in the 

 same manner as the first, and through the solution a current of carbonic 

 acid was passed, so as to convert the caustic potash into carbonate, and 

 the solution heated to expel the excess of carbonic acid. Chloride of 

 barium was added, which gave a bulky precipitate, consisting of carbonate 

 and sulphate of barytes, which were treated in the same manner as in the 

 former experiment. The excess of carbonic acid over the former experi- 

 ment gave the quantity of carbonic acid taken up by the free potash, ami 

 from this the quantity of caustic potash was calculated. The total 

 loss of carbonic acid amounted to 6*72 grains = 13*44 grains per cent, 

 from which, if we deduct 9*22 grains, we obtain 4*22 grains of carbonic 

 acid as saturating the free potash. The hydrate of potash required to 

 saturate this amount of C0 2 , is 10*93 grains per cent. 



3. Estimation of the Sulphate of Lime and Potash. — After digesting 

 the carbonate of barytes in hydrochloric acid, and filtering, the sulphate 

 remained upon the filter equal to BaO S0 3 11*96 = 4*12 SO s . Oxalate 

 of ammonia was added to a fresh portion, and boiled for some time, so as 

 to decompose the sulphate of lime, which, after being burned, left 1*04 

 carbonate of lime = 1*90 sulphate of lime. I'll grains of SO s being 

 required to unite with the lime, there remain 3*01 grains SO s to combine 

 with potash. Hence the amount of sulphate of potash is 6*62 grains per 

 cent. 



4. Estimation of the Chloride of Potassium. — The solution from 100 

 grains was treated with nitrate of silver, and boiled with nitric acid, so as 

 to decompose any cyanide of silver that might have been formed. The 

 precipitate was then washed, dried, burned, and weighed, when it gave 

 3 grains chlorido of silver = 1*58 chloride of potassium. 



5. Estimation of the Cyanide of Potassium. — 100 grains of the black 

 cake were washed in a covered filter with cold water until all soluble 

 salts were removed. To the solution, which was carefully protected from 

 tin- air, nitrate of silver was added a3 long as a precipitate, consisting of 

 chloride, cyanide, carbonate, and oxide of silver, fell. The whole was 

 then thrown upon a filter and washed. It was boiled with nitric aeid, 

 and the silver dissolved was precipitated, as chloride of silver, by hydro- 

 chloric acid ; this precipitate was then ignited and weighed. After 

 deducting the quantity of chloride of silver equivalent to the carbonate, 

 caustic potash, and also the chloride of potassium, from the excess of 

 chloride of silver, the cyanide of potassium was calculated, thus: — 



\,„ II. — No. 4. 



