CARBON. 137 



pound of 1 atom lime and 1 atom carbonic acid) 

 the atomic weight of carbonic acid is 2 '75. The 

 following experiment, which I have repeated 

 more than once, will show that this determina- 

 tion is rigidly exact. 



2. I must begin by statins*, what will be after- Atomic 



weight of 



wards proved, that an atom of potash weighs 6. carbonic 

 This alkali combines in two proportions with car- mined! 

 bonic acid, forming a carbonate, composed of 1 

 atom potash, united to 1 atom carbonic acid ; 

 and a bicarbonate, composed of 1 atom potash, 

 and 2 atoms carbonic acid. The latter of these 

 salts crystallizes in large transparent and perma- 

 nent crystals, not affected by exposure to the air. 

 It can easily be procured in this state in this 

 country, very nearly pure, being only occasion- 

 ally contaminated by a little lime and a little 

 iron. If we dissolve these crystals in distilled 

 water, filter the solution, evaporate it to dry- 

 ness, and expose the saline residue to a red heat, 

 we obtain anhydrous carbonate of potash in a 

 state of great purity. Dissolve 87i grains of 

 this salt in water ; dissolve in muriatic acid 62i 

 grains of pure anhydrous carbonate of lime ; eva- 

 porate the solution to dryness, in a gentle heat, 

 to drive off the excess of acid ; and dissolve the 

 muriate of lime formed in distilled water. Thus 

 we have two solutions, containing each determi- 

 nate quantities of a particular salt : the first so- 

 lution, 87i grains of carbonate of potash, and the 



