CHAPTER VIII 



PHOSPHATES 



Practically all of the clay lands of the country and 

 many of the other soils stand in need of phosphates, and 

 the higher the standard of farming the greater is the 

 amount required. There are three main sources from 

 which supplies are drawn : bones, superphosphate, and 

 basic slag. 



Bones 



Bones have long been applied as manure in isolated 

 parts of the country, but they were not commonly used 

 until the beginning of the 19th century. Such remark- 

 able results were then obtained in certain districts, e.g., 

 in Cheshire, that the demand became very great, and 

 the rather large accumulations of the past in various 

 parts of the world had to be drawn upon to satisfy it. 

 The demand stiU continues ; the butchers' shops, meat 

 markets and marine store dealers of the great cities are 

 ransacked to keep up the supply. In modern practice 

 the bones are sent to the works, put on to a perforated 

 band and sorted; clean shank bones are picked out for 

 cutlery, hard bones for glue making and the remainder 

 for crushed bone : the separate batches are steamed at 

 low pressure (15-20 lbs.) to remove fat, nowadays a 

 valuable commercial product. In some works the bones 

 are degreased with benzene, and this process is more 

 efficient than steam, so that the residual bone meal is 

 richer in nitrogen and in phosphate. 



