CHAPTER XIII. 



Experiments with the salts of ammonia continued. Proportions of nitrogen 

 contained in the nitrates and in the salts of ammonia. Comparison of these 

 proportions with the effects they have been found to produce upon the 

 quantity of the crop. The state of chemical combination in which the nitro- 

 gen exists in a manure affects its influence. Comparative experiments with 

 gelatine, with rape-cake, and with the sulphate of ammonia, on the quantity 

 of the crop. Influence of the quantity of nitrogen, and of the state of chemical 

 combination in which it exists in a fertilising substance, on the quality of a 

 crop to which it has been applied. Suggestions for experiments with the 

 carbonate, nitrate, muriate, and sulphate of ammonia. Suggestions for experi- 

 ments with the acetate and oxalate of ammonia. Suggestions for experiments 

 with the phosphate of ammonia, the ammoniacal phosphate of soda, and the 

 ammoniacal phosphate of magnesia. Suggestions for comparative experiments 

 with gelatine, oil-cakes, urea, uric acid, and nitrate of urea. 



1. Are the effects of the salts of ammonia and of the nitrates 

 on the quantity of the crop in direct proportion to the quantity 

 of nitrogen they respectively contain ? 



THE relative proportions of nitrogen contained in the nitrates 

 of potash, soda, and lime, and in the salts of ammonia employed 

 in the comparative experiments, of which the details were given 

 in the preceding section, are represented by the following 

 numbers : 



Nitrogen per cent. 



Sulphate of ammonia contains . . . . 21.2 



Muriate of ammonia, (sal-ammoniac,) . . . 26.2 



Nitrate of ammonia, . . . . . . 35.1* 



Nitrate of potash, 13.97 



Nitrate of soda, 16.58 



Nitrate of lirne, . . ... . . 17.14 



With the aid of these numbers we shall examine, the above 

 experiments. They will enable us to test the influence of the 



* Of this nitrogen one-half is in the state of nitric acid, and one-half in that 

 of ammonia. 



