184 



Mr. A. B. Nortlicote on the Function of Salt 



Now as soon as the solution of carbonate of ammonia is 

 dropped into these salt solutions, there occurs (as might have 

 been anticipated) a precipitation of the sulphate of lime which 

 they contain as carbonate ; this must be attended with a corre- 

 sponding fixing of the ammonia, the latter combining with the 

 sulphuric acid to which the lime was previously united ; and by 

 this reaction, the imuiense difference observed between the ab- 

 sorbing power of these solutions and that of a solution of pure 

 chloride of sodium would appear to be accounted for. Whether, 

 then, by its own immediate agency, as in the case of manuring 

 with gypsum, or by the intervention of the absorbent power of 

 the chloride of sodium, the soluble lime-salt present is really the 

 most powerful agent in the absorptive process — a fact which was 

 still further demonstrated by the addition of a few drops of solu- 

 tion of chloride of calcium to some of the pure chloride of sodium 

 solutions, to which, iu the previous experiments, the maximum 

 of ammonia solution had been added, — instant absorption, and 

 consequently diminished action on the test-paper, was of course 

 the result. 



The absorptive power of the specimens examined ought there- 

 fore, if so dependent upon the amount of lime-salt, to be almost 

 in the ratio in which that exists in their soluble portion. The 

 subjoined Table will, however, show a discrepancy in this par- 

 ticular. 



Composition of the portion soluble in water, calculated 

 to 100 parts. 



If, now, we compare the quantity of sulphate of lime which these 

 salts respectively contain with the amount of ammonia which they 

 are capable of absorbing, wc find no such proportion as might have 

 been expected. This arises from the extreme insolubility of the 

 sulphate of lime compared with the solubilities of the other con- 

 stituents of the salt ; and fresh lime-determinations in the solu- 

 tions actually employed in the absorption experiments showed, 

 that notwithstanding the different composition of the three salts, 

 the amount existing in the solutions prepared as before described 

 was very much the same. The other constituents, from their 



