MANUAL FOR SUGAR GROWERS. 69 



a dry mass which can be ground, and is then in a 

 very suitable form for use as manure. Phosphate 

 of lime submitted to this process is known as super- 

 phosphate. 



Phosphate of lime suitable for conversion into 

 superphosphate is found very widely distributed in 

 nature, in .the fossilized remains of animals and 

 their excreta ; of this character are the coprolites 

 of the eastern counties of England, the phosphate 

 beds of Sombrero, Aruba, Florida, Canada, etc. 

 These mineral phosphates are found in various de- 

 grees of purity from those containing seventy or 

 eighty per cent, of phosphate of lime down to those 

 containing a mere trace. 



Good superphosphate should contain fifteen to 

 twenty-four per cent, of the soluble or mono- or 

 acid- phosphate of lime, as it is variously termed, 

 equal to about twenty to thirty-two per cent, of in- 

 soluble or tri-calcium phosphate rendered soluble. 



Finely ground mineral phosphates are sometimes 

 used without being treated with acid ; it is neces- 

 sary that the substance be used in a state of very 

 fine powder. In this condition good results have 

 been obtained in the case of the sugar-cane. If 

 lime be added to superphosphate, the mono-calcium 

 phosphate is reconverted to tri-calcium phosphate. 

 This is sold under the name of precipitated phos- 

 phate. Ground mineral and precipitated phos- 

 phates, from the fact that they are not acid, are well 

 suited for soils containing but traces of lime. 



Intermediate in character between natural ma- 

 nures and mineral phosphates are the manures known 



