AMMONIA WITH CARBONIC ACID. 137 



ammonia, and is not capable, even when employed in great 

 quantity, of decomposing it, although pure ammonia combines 

 easily, and in great quantity, with the chloride of calcium. 



The f carbonate of ammonia only feebly retains that portion 

 of carbonic which it contains, more than is requisite to form the 

 bicarbonate. It is only when the salt has separated in crystals 

 that it resists speedy decomposition. But even in the soUd state 

 it loses the last portion of carbonic acid, and easily effloresces 

 into the bicarbonate : on which account the crystals, when once 

 formed, under the air-pump, must not be allowed to remain there. 

 But the salt not only effloresces and passes into the bicarbonate, 

 when exposed to the air, but even in the closed vessels in which 

 it is intended to preserve it. 



The preparation of this salt, moreover, is very uncertain, and 

 I have succeeded but very rarely. It seems to depend on the 

 concentration of the solution, and on the evaporation under the 

 air-pump, which must neither be too quick nor too slow. If a 

 saturated solution of the sesquicarbonate is evaporated over sul- 

 phuric acid, without being placed in vacuo, the whole of the 

 carbon disappears with a slower evaporation of the water, and 

 nothing is left behind. 



If we regard the 4 carbonate of ammonia as a double salt, we 

 must admit the presence of the carbonate, together with the 

 bicarbonate ; and the quadricarbonate contained in the -J- car- 

 bonate of ammonia, and the very compound formula would 

 be (C + NH3) -I- (4 C + 2 NH^) + (4 C + NH") + 7 H, or 6 

 H, if 9 atoms of water are contained in the salt. 



It must be evident to every one that the number of combina- 

 tions of carbonic acid with ammonia might easily have been in- 

 creased had I continued further my experiments on this subject ; 

 for the subhmation of the various kinds of bicarbonate, of -J-, and 

 of the various kinds of the -f- carbonate of ammonia, would cer- 

 tainly have produced new double salts, which may be imagined 

 as formed of the carbonate, united with bicarbonate and the 

 quadricarbonate. I thought it best, however, after having con- 

 tented myself with indicating the possibility of the existence of 

 this great number of double salts, to discontinue the examination. 



Among the combinations of carbonic acid with ammonia, it 



