On Superphosphate of Lime. 



219 



coprolite mig-ht, from a variety of circainstances, be found to 

 vary from time to time, and the above statement is therefore only 

 applicable as a general rule. It is said that the carbonate of lime 

 in particular is sometimes in considerably larger proportion than 

 that given above. In dissolving coprolite powder in sulphuric 

 acid an escape of hydrofluoric acid takes place, and some of the 

 sulphuric acid is neutralized by the lime of the fluoride of cal- 

 cium. In the case of the coprolites it is needless, however, 

 to complicate the matter by making allowance for this cir- 

 cumstance. 



To convert the phosphate of lime of 100 lbs. of Suffolk copro- 

 lite entirely into bi-phosphate would require, of 



Oil of vitriol, to neutralize the carbonate . 10 lbs. 

 For the phosphate . . . . . 31 „ 



41 „ 



The product, when dried up, vvould have something like the fol- 

 lowing composition in 100 parts: — 



Moisture ........ 10 



Hydrated sulphate of lime (gypsum) , . .49 

 Bi-phosphate of lime ...... 25 



Sand, cla}^ &c. . . . . . . .16 



100 



In the above products there would not of course be any animal 

 matter, as phosphate of lime is a purely mineral substance ; but 

 it is very seldom that a mixture of sulphuric acid and coprolites 

 alone would be sold as superphosphate of lime, unless it were dis- 

 tinctly so stated. By conventional understandins^ the commercial 

 " superphosphate " is a mixture of soluble phosphate with animal 

 substances or ammoniacal salts — more or less resembling, in 

 fact, the product that would result from the treatment of bones 

 with acid. 



The phosphoric fossils of the upper and lower greensand 

 formations may of course, when obtainable in sufficient quantity, 

 be substituted for those of the crag. It will be sufficient here 

 to state that the fossils of the upper greensand contain from 55 

 to 60 per cent, of phosphate, and 8 to 10 of carbonate ; and those 

 of the lower greensand from 38 to 40 per cent, of phosphate, 

 with little or no carbonate. This latter circumstance is of much 

 advantage in the economy of the acid, and in spite of their lower 

 percentage of phosphate they would furnish more soluble phos- 

 phate for a given expense than those of the crag or the upper 

 greensand. 



Superphosphate from the Phosphorite of Estremadura and the 

 United States. — The phosphorite of Spain has not been imported 



