20 BULLETIN 312, U. S. DEPARTMENT OF AGRICULTURE. 



MECHANICAL TREATMENT OF PHOSPHATES. 



The patents listed in Table XI, Appendix, deal with the mechan- 

 ical treatment of either raw phosphates or the chemically treated 

 product. The first seven processes are primarily intended for the 

 treatment of bones or phosphates to be used in the manufacture of 

 baking powder. The other processes listed hardly require any more 

 detailed descriptions than those given in the tables. All the patents 

 covering these processes have long since expired, and they can there- 

 fore be used without payment of royalties. 



MISCELLANEOUS PROCESSES FOR THE PRODUCTION OF AVAILABLE 



PHOSPHATES. 



Under the head of miscellaneous are included all the processes 

 which can not very well be separately listed. Many of these processes 

 are on their face practically valueless, while others have features 

 which make it appear they might be successfully employed in the 

 production of fertilizers of some value. A list of the patents under 

 this head is given in Table XII, Appendix. 



The process in the above table which has probably attracted the 

 most attention is that of Coates, 1 in which the inventor claims to 

 produce available phosphoric acid and potash from minerals con- 

 taining these elements by the action of bacteria, which attack and 

 break down the rocks. His process consists in first obtaining a culture 

 by adding breaking-down or decaying rock to a sterilized culture 

 medium. He then inoculates sterilized phosphate rock or feldspar 

 with the culture thus prepared, with the result that the bacteria 

 attack the rock minerals, rendering the phosphoric acid and potash 

 contained therein soluble in the soil solution. 



It is understood that field experiments are being conducted to test 

 the fertilizer value of rock treated in this way, but the results of 

 these experiments have not yet been reported. 



i United States Patent No. 947795 (1910). 



