706 



good, 10 c\vt. per acre, and even more than that. They are mixed 

 and sold in enormous quantities every year for making sun 

 phosphate, which is the principal use they are put to. 



SUPERPHOSPHATES, OR DISSOLVED MINERAL PHOSPHATES. 



These manures are made from coprolites, bone ash, bone 

 charcoal, and phosphatic or mineral guanos. They are made in 

 very large quantities in almost every part of the world. So great is 

 the demand for these manures that about 600, coo tons are made 

 annually in England alone. This will give an idea of the great 

 faith the farmers in England have in superphosphates, and that not 

 without good reason, as the results derived from the use of them 

 fully justifies anything that has been said in their favor. They are 

 made by mixing ground coprolites, apatite, bone ash, bone black, 

 or phosphatic guanos, with sulphuric acid, specific gravity r6o to 

 1*70. The mixing is done by machinery constructed for the pur- 

 pose, and the mass is then run into a closed pit which is connected 

 with a Hume that carries the fumes or gases (fluorine, carbonic acid, 

 etc.) to a condensing tower, or otherwise they would be very 

 annoying to the workmen, as well as dangerous to their health. 

 After the mas-> has spent itself in the pit, when it becomes some- 

 what dry it is thrown out by workmen with wooden shovels. It is 

 then ground in a roller mill for the purpose of more thoroughly 

 mixing and breaking up the lumps into a state fit for the market. 

 The action of the sulphuric acid on the phosphates is to 

 convert the insoluble tricalcic phosphate into soluble mono- 

 calcic phosphate. The sulphuric acid does this by com- 

 bining with the lime that is in combination with the phosphoric 

 acid. Thev are made in two qualities or quantities of phos- 

 phate of lime made soluble. The lower class contains ab mt 

 25 per cent, soluble phosphates, and the high class 30 to 40 per cent, 

 soluble phosphates. This does not mean, as might appear, 

 that there is 25, 30, or 40 per cent, of the soluble mono- 

 calcic phosphate in the manure, but that these are the percentages 

 of tricalcic phosphate made soluble. There are also the concen- 

 trated or double superphosphates, containing from 60 to 85 per 

 cent, of soluble phosphates. These concentiated manures are very 

 costly to make and necessarily are dear. Whether it is any benefit 

 to use them will greatly depend on whether they have to be con- 

 veyed long distances where the carriage is high, otherwise there 

 is no special benefit from them over the ordinary superphosphates. 

 By using them you lose the benefit of the sulphate of lime that is 

 in the ordinary manure, which might necessitate the use ot gypsum 

 or sulphate of lime. The enormous extent to which the manure is 

 used in every country proves it is the universal method of applying 

 phosphates to the SOll to obtain a quick and increased return for 

 the money invested. 





