thus facilitating decay and availability, as such bone 

 can be ground finer than raw bone, and thus becomes 

 more subject to the attack of soil moisture and 

 various dissolving agents. 



Raw bone contains from 3% to 42/2% nitrogen and 

 about 22% or 23% phosphoric acid. Steaming reduces 

 the nitrogen and correspondingly increases the phos- 

 phoric acid, so that steamed bone may run as low as 

 1% nitrogen and as high as 25% or 30 % phosphoric 

 acid. The best effect from the phosphoric acid of 

 steamed bone is had when the bone is used in connec- 

 tion with some ammoniate such as blood, or blood 

 and bone, or manure. Nitrogen or ammonia increases 

 the efficiency of phosphoric acid, and for this reason 

 phosphoric acid from animal or vegetable sources is 

 regarded as the best, the most effective and the most 

 readily available form. 



THOMAS PHOSPHATE SLAG ( POWDER). 



Thomas slag, a product of iron furnaces, is a 

 good source of phosphoric acid, though not so gene- 

 rally used as bone or rock. This material has to be 

 finely ground to be of value, as it is not acidulated. 

 It will analyze as high as 20% phosphoric acid. 

 Thomas slag also contains much lime, which fact 

 should be considered when it is used in presence of 

 ammonium sulphate, or barn manures, as the lime will 

 drive off the ammonia. One brand offered for sale in 

 Los Angeles contains 17.28 % phosphoric acid, 



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