76 A TREATISE ON THE CONNECTION OF 



PHOSPHAT OF MAGNESIA. 



This is a very soluble salt; seldom occurs in nature ; 

 l^romotes vegetation. It may be formed in soils con- 

 taining phosphat of lime and uncombined magnesia, 

 by watering ground, containing these substances, with 

 water acidulated by the vitriolic acid, or by an acid py- 

 riteous liquor ; or the acid may be applied, by moistening 

 mould with water properly acidulated by the vitriolic 

 acid, and then sowing, or spreading the mould on the 

 ground. In this case the vitriolic acid will join with 

 the calcareous matter of the phosphat of lime, and form 

 gypsum ; whilst the phosphoric acid, thus disengaged, 

 will join with the magnesia in the soil, and form phos- 

 phat of magnesia. 



If phosphat of lime can be decomposed by suJphat of 

 iron, (on the principles of the double elecitivc attrac- 

 tions) and form sulphat of lime (or gypsum) and phos- 

 phat of iron, the phosphat of iron may, in that case, be 

 decomposed by magnesia, forming phosphat of mag- 

 nesia. 



PHOS- 



