808 ANNUAL REPORT OF THE Off. Doc. 



While, as has been stated, mills for grinding bones existed early 

 in the nineteenth century in France and England, and enterprising 

 men went ?o far as to dig up battlefields and unearth thousands of 

 tons of bones for agricultural purposes, and as it is even claimed 

 that the credit for making the first super-phosphate is due to Sir 

 James Muri ay, which was done in 1877, yet it was made without any 

 real knowledge of the change which took place or application of the 

 practical value accomplished. 



As a result of his researches, Leibig pointed out that by treating 

 bones and mineral phosphates with sulphuric acid, the insoluble 

 phosphoric acid would be changed to a soluble form, and a consider- 

 able quantity of gypsum (sulphate of lime or land plaster), would 

 be formed at the same time. The experiments of Leibig were sub- 

 stantiated bv those conducted bv the Duke of Richmond in com- 

 paring fresh and degelatinized bone from which he came to the 

 conclusion that bones owed their fertilizing value not to gelatins 

 or fatty matter, but to their large percentage of phosphoric acid. 

 These experiments were still further confirmed by the results, 

 shortly afterwards published by Boussingault. This set all uncer- 

 tainty with regard to the value of phosphoric acid at rest and es- 

 tablished its value and necessity on a permanent foundation, marked 

 a distinct epoch in the uses of phosphates, which, from that time, 

 has rapidly spread and been constantly increasing. 



THE ROLE OF PHOSPHORIC ACID IN PLANTS. 



The function which phosphoric acid performs in plants is quite 

 varied, yet in all cases exceedingly essential. The present status 

 of this subject has been fully set forth by Dr. Oscar Loew. in Bulletin 

 Xo. IS, of the Division of Vegetable Pathology, U. S. Dept. of Agri- 

 culture. "On the Physiological Role of Mineral Nutrients." The 

 principal points which it might be well to mention here are that the 

 chlorophyll to which the green color of plants is due, can only be 

 formed in the presence of phosphoric acid and. hence, all the essen- 

 tial functions which are closely related to the chlorophyll are 

 dependent upon this element. Relatively large proportions are 

 found in yeast cells, in seed just forming and numerous other 

 microscopic organizations which are playing so important a part 

 in the growth of plants. Proper embryo development of seeds seems 

 to be dependent upon phosphates, and some observers have claimed 

 that the total mass of protein in seeds is increased by an increased 

 supply of phosphoric acid. 



THE IMPORTANCE OF PHOSPHORIC ACID TO CROPS AND THE NEED 

 FOR SUPPLYIXG IT IN FERTILIZERS. 



It has already been stated that phosphoric acid was very neces- 

 sary to the growth of crops and particularly essential to the ma- 



turitv of seeds. 



