OF AMMONIA. 213 



acid to the atom of ammonia, and constituting, 

 therefore, the salt which I am just going to no- 

 tice. 



4. Sesquicarbonate of ammonia. This is the Scs r jicar - 

 name which ought to be given to the carbonate 

 of ammonia of the shops. It is usually in the state 

 of hard white cakes, having a strong ammoniacal 

 odour, and instantly giving a purple colour to cud- 

 bear paper. I have frequently examined this salt 

 at different times and in different places, to ascer- 

 tain whether there was any difference in its com- 

 position. It is only a sesquicarbonate when 

 newly prepared ; by keeping, it gradually loses 

 a portion of its ammonia, and I have obtained it 

 in a great variety of states between a sesquicar- 

 bonate and bicarbonate ; but never constituting a 

 true bicarbonate. I analyzed this salt in the fol- 

 lowing manner : 



7*375 grains of it were dissolved in water, 

 and mixed with a solution of 9 grains of oxalic 

 acid crystals. The mixture, when recent, pro- 

 duced no change on cudbear paper, and there- 

 fore contained no free ammonia. It reddened 

 litmus paper ; but the blue colour was speedily 

 restored when the paper was left exposed to the 

 air : hence, it- was owing to the carbonic acid 

 disengaged from the ammonia by the oxalic 

 acid. Now, 9 grains of oxalic acid crystals 

 contain 4%5 grains of true acid, which require 

 for saturation H25 grains of ammonia. This, 



Q2 



