PHOSPHORUS, ITS SOURCES AND USE IN PLANT FEEDING 67 



effect on the immediate annual crop you had better get the dissolved rock or 

 acid phosphate. With most farmers, the question of immediate returns for 

 the expenditure is the most important point. 



SOME ERRONEOUS POPULAR NAMES. 



In some parts of the country farmers call all commercial fertilizers 

 "phosphate." This is an error which all should rid themselves of as quickly 

 as possible. The term phosphate is applicable only to compounds of phos- 

 phoric acid and a base, making what is called a salt. Thus the phosphate of 

 lime is a salt composed of a certain number of parts of lime with phosphoric 

 acid. A commercial fertilizer in which the phosphoric acid is only one of the 

 constituents cannot correctly be called a phosphate. It is simply a fertilizing 

 mixture in which phosphoric acid is one of the constituents. The proper 

 term to apply to all mixed goods is commercial fertilizer. 



Then, too, the popular name "acid phosphate" as applied to the dissolved 

 phosphate rock is not strictly correct. Phosphate is the original condition in 

 which the phosphoric acid is found in the rock. When dissolved in sulphuric 

 acid it becomes a superphosphate. But the term "acid phosphate" has be- 

 come so fixed in popular use that it answers all purposes, and suits our Ameri- 

 can liking for brevity better than the longer word, superphosphate. Super- 

 phosphates, whether made from rock, bones or bone charcoal, are identical, 

 varying only in the percentage of phosphoric acid with the amount in the 

 article from which they are made. Hence a superphosphate made from bones 

 will have a higher percentage of phosphoric acid than one from rock, but one 

 per cent, in the one is just as good as one per cent, in the other. Acid phos- 

 phate is always better when freshly made than after being stored for a long 

 time, since there is a tendency to reversion to a less soluble form in long 

 standing, and there is a decrease of the soluble and an increase of the form 

 soluble only in ammonium citrate. Acid phosphate, then, which has been 

 kept over a season, is less immediately available than a freshly made article. 

 This takes place more readily in superphosphates made from the mineral 

 phosphates than in those made from bones or bone charcoal. Superphos- 

 phates made from bone and bone charcoal are more uniform than those from 

 mineral phosphates, and their phosphoric acid is nearly all soluble, while 

 those from mineral phosphates may run all the way from 12 to 14 per cent, 

 in the South Carolina, to 16 or even 18 per cent, in the Tennessee. Super- 

 phosphates from raw animal bone usually have about 12 per cent, available 

 phosphoric acid, and about 5 per cent, insoluble, but having also a percentage 

 of ammonia, they have a higher value commercially than the dissolved rock, 

 but their agricultural value may be no higher. 



