56 SALTS 



2 atoms carbonic acid 5-5 



1 atom potash 6 



1 atom water . 1*125 



12-625 



The crystallized bicarbonate of commerce always 

 contains a little more than an atom of water. 

 This surplus varies in quantity, and is, I suppose, 

 lodged mechanically between the plates of the 

 crystals. The greatest quantity of water which 

 I have met with in this salt is 14 atom, and the 

 least about 11 atom. This uncertainty in the 

 aqueous portion of this salt renders it difficult to 

 employ it in chemical analyses, where an exact 

 quantity of potash is wanted for any particular 

 purpose. But, if we expose the salt to a red heat 

 we convert it into an anhydrous carbonate, com- 

 posed of 



1 atom carbonic acid 2 '75 



I atom potash . 6 



8-75 



So that 8'75 grains of it contain just 6 grains of 

 potash in this way I use it. 



Phosphate, 7. Phosphate of potash. This salt is not very 

 easily obtained in a state of purity ; however, by 

 neutralizing a solution of carbonate of potash 

 with phosphoric acid, concentrating the solution, 

 and setting it aside for some days, a neutral phos- 



