1835.] Scientific Intelligence, 473 



sure is sufficient to extract carbonic acid from a solution of the salt 

 at the usual temperature. The way in which sesqui-carbonate of 

 potash is formed is explained by the sixth and seventh experiments. 



Rose has often evaporated a solution of bi-carbonate of potash 

 in vacuo over sulphuric acid, to obtain sesqui-carbonate of potash as 

 recommended by Berth ollet. He obtained a mass, of which a part 

 deliquesced in moist air, while, in the dry portion, crystals of bi-car- 

 bonate could be detected. The deliquescent mass afforded a precipi- 

 tate in the cold with sulphate of magnesia. Hence, it contained 

 simple carbonate. It is, therefore, proper to determine whether an 

 alkaline carbonate is a simple or double salt by this means. 



SODA AND CARBONIC ACID. 



10. 1-9705 grms. (30*338 grs.) of bi-carbonate of soda were dis- 

 solved in 8'442 ounces of water, and evaporated to dryness in vacuo 

 over sulphuric acid. The discharged carbonic acid was occasionally 

 removed by the action of the pump. In the solution remained 38*28 per 

 cent, of carbonic acid, nearly the quantity to form a sesqui-carbonate. 



11. The 8th experiment was repeated by boiling 1*26*4 grms. 

 (19*465 grs.) of bi-carbonate of soda dissolved in water. The solu- 

 tion contained 31*74 per cent, of carbonic acid. This is a larger 

 quantity than is contained in the carbonate, and less than is necessary 

 to form a sesqui-carbonate — the former requiring 26-10, and the 

 latter 39*15 per cent, of carbonic acid. It appears from this result 

 and others which Rose obtained, that if the solution were boiled lono- 

 enough, especially in an open vessel, the bi-carbonate would be com- 

 pletely changed into carbonate. Soltmann, a large manufacturer, 

 prepares sesqui-carbonate by evaporating a solution of bi-carbonate, 

 but never by mixing the bi-carbonate with carbonate. These crystals 

 are small, and possess the exact shape of trona or native sesqui-car- 

 bonate ; they are, however, mixed with some carbonate. 



12. 0*821 grms. (12*64 grs.) bi-carbonate of soda were dissolved 

 in '469 ounces of cold water, and at the usual temperature and pres- 

 sure evaporated over sulphuric acid, the solution being surrounded 

 with caustic potash; the dried mass weighed 0*666 (1025 grs.) : it 

 was again dissolved in the same quantity of water and again evapo- 

 rated. It now weighed -643 grms. (9902 grs.). The solution of 

 this residue in water gave *564grms. (8*684 grs.) carbonate of lime = 

 *2465 grms. (3*78 grs.) carbonic acid. The mass consisted of *3043 

 grms. (4-68 grs.) soda, '2465 grms. (3*78 grs.) carbonic acid, and 

 •0922 grms. (1 *41 grs.) water. The usual method of determining the 

 quantity of carbonic acid in mineral waters, it is obvious from these 

 experiments, cannot be correct. To obtain the true quantity, the 

 water should be precipitated with chloride of calcium, or rather 

 chloride of barium, the solution of one of these salts should be added 

 to the water, along with a quantity of ammonia, and the precipitate 

 allowed to subside in a well corked flask. The precipitate contains 

 sulphate and phosphates, should the water contain these acids. Hav- 

 ing weighed them, after ignition, the sulphate is treated with an 



