216 AMMONIACAL PHOSPHATE OF MAGNESIA. 



phosphoric acid, three substances very necessary to plants, 

 make it desirable to ascertain, by comparative trials, its special 

 effects upon vegetation. 



a Alone, applied in different quantities under different cir- 

 cumstances, to different crops, and on different soils. 



b In comparison with the several substances of which it con- 

 sists, with the view of eliminating, as far as possible, the special 

 effects or influence of each. In these experiments, the effects 

 produced respectively by the carbonate of ammonia, the phos- 

 phate of ammonia, the carbonate of soda, and the phosphate of 

 soda, on separate portions of the same field and crop, if carefully 

 observed and noted, would afford us the means of drawing very 

 probable deductions. 



3. The ammoniacal phosphate of magnesia is produced during 

 the fermentation of human urine, and falls as a white crystal- 

 line powder when a solution of sulphate of magnesia is mixed 

 with one of phosphate of ammonia, or of the ammoniacal phos- 

 phate of soda. It is sparingly soluble in water, and consists of 



Ammonia, . . . . . . 6.9 per cent. 



Magnesia, . . . . . . 16.3 ... 



Phosphoric acid, ..... 29.1 



Water, 47.7 ... 



100 

 Its equivalent number is 307. 



All the constituents of this salt are necessary to the growth 

 of plants. Independently of any supposed special action of the 

 salt as a chemical compound, there is reason, therefore, to anti- 

 cipate very striking effects from its application to growing plants. 

 This anticipation has been so far verified by an experiment of M. 

 Boussingault. He treated young plants of maize with this sub- 

 stance, to the extent of about half-an-ounce for each plant, and 

 found that not only did they grow faster and larger, but that, 

 while plants to which no phosphate had been applied produced 

 one perfect and one abortive head, those which had been treated 

 with it produced two perfect and one abortive head, and the 

 grains were also double those of the others in size. This en- 

 couraging result suggests the propriety of further and more 

 enlarged experiments. 



