i. ANALYSES OF FERTILIZERS— SPRING SEASON, 1908. 



BY B. W. KILGORE, STATE CHEMIST. 



The analyses presented in this Bulletin are of samples collected 

 by the fertilizer inspectors of the Department, under the direction of 

 the Commissioner of Agriculture, during the spring months of 1908. 

 They should receive the careful study of every farmer in the State 

 who uses fertilizers, as by comparing the analyses in the Bulletin 

 with the claims made for the fertilizers actually used, the farmer can 

 know by, or before, the time fertilizers are put in the ground whether 

 or not they contain the fertilizing constituents in the amounts they 

 were claimed to be present. 



TEEMS USED IN ANALYSES. 



Water-soluble Phosphoric Acid. — Phosphate rock, as dug from the 

 mines, mainly in South Carolina, Florida and Tennessee, is the chief 

 source of phosphoric acid in fertilizers. 



In its raw, or natural, state the phosphate has three parts of lime 

 united to the phosphoric acid (called by chemists tri-calcium phos- 

 phate). This is very insoluble in water and is not in condition to 

 be taken up readily by plants. In order to render it soluble in water 

 and fit for plant food, the rock is finely ground and treated with sul- 

 phuric acid, which acts upon it in such a way as to take from the 

 three-lime phosphate two parts of its lime, thus leaving only one 

 part of lime united to the phosphoric acid. This one-lime phosphate 

 is what is known as water-soluble phosphoric acid. 



Reverted Phosphoric Acid. — On long standing some of this water- 

 soluble phosphoric acid has a tendency to take lime from other sub- 

 stances in contact with it, and to become somewhat less soluble. This 

 latter is known as reverted or gone-back phosphoric acid. This is 

 thought to contain two parts of lime in combination with the phos- 

 phoric acid, and is thus an intermediate product between water- 

 soluble and the original rock. 



Water-soluble phosphoric acid is considered somewhat more valu- 

 able than reverted, because it becomes better distributed in the soil 

 as a consequence of its solubility in water. 



