1870.] BROOME — ON CANADIAN PHOSPHATES. 255 



absorptive powers ; and this is rendered the more likely by 

 the fact that all of the mineral waters occurring in the 

 Paloeozoic rocks of Canada, which Dr. Hunt beautifully 

 designates as fossil sea-waters,* contain traces of phosphoric 

 acid, resembling in this respect the waters of modern seas. 



The absorptive powers of soils are due to a combined 

 chemical and molecular action, the completeness of which is, 

 to a very great extent, dependent upon the mechanical 

 condition of the mass. 



Soluble phosphates of lime, when thrown over the surface 

 of the land, are quickly converted into the insoluble tribasic 

 salt, by the action of carbonates and basic compounds ; but 

 the product, being in a state of extreme division, is readily 

 dissolved by water charged with carbonic acid, and also, as 

 shown by Liebig, by solutions of ammoniacal salts, or of the 

 chlorides and nitrates of the alkalies. 



These modes of solution are exceeduigly important from an 

 agricultural point of view, since they shew the advantage of 

 compound manures, formed by the addition of ammonia or pot- 

 ash salts to the ordinary "super-phosphates," In an experi- 

 ment, recently made by me, for the purpose of ascertaining the 

 solubility of apatite in carbonic-acid water, it w^as found that, 

 by digestion of the finely pulverized mineral for twenty-four 

 hours, at a temperature of 60° F., agitating frequently, a 

 saturated solution of carbonic acid is capable of dissolvmo* 

 whi parts of the mineral. Similarly conducted experiments 

 with solutions of sal ammoniac, and of potassic chloride 

 gave respectively, the proportions t«V« and Tf-rx.f 



Alkaline carbonates also dissolve apatite, with the forma- 

 tion of carbonate of lime and a phosjohate of the alkali ; and 

 these reactions explain the existence of phosphate of lime 

 in sea-water, a fact long since demonstrated by Clemm and 

 Forchammer. J 



* Tide Geology of Canada, 1863, pp. 561-564. 



t Portions of a fine sea-green prismatic crystal of the Burgess apatite 

 vere used in these trials. For its composition, see Analysis on p. IS. 



X J. fur Prakt. Chim. xxxiy., 185; also Berzelius, Jahresb, xxiy., 393. 



