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iEt 



ed in them. The terms "raw bone," "fine bone," " boiled'and steamed' 

 bone," etc., are used to indicate methods'of preparation, and inasmuch 

 as bone is a material which is useful largely in proportion to its rate of 

 decay, its fineness has an important bearing upon availability, since the 

 finer the bone the more surface is exposed for the action of those forces 

 which cause decay or solution, and the quicker will the constituents be- 

 come available. In the process of boiling or steaming, not only is bone 

 made finer, but its physical character in other respects is also changed, 

 the particles, whether fine or course, being made soft and crumbly rather 

 than dense or hard ; hence it is more likely to act quickly tban if the 

 same degree of fineness be obtained by simple grinding. The phos- 

 phoric acid in fine steamed bone may all become available in one or two 

 years, while the coarser fatty raw bone sometimes resists final decay for 

 three or four years, or even longer. Tone, however, contains consider- 

 able nitrogen, a fact which should be remembered in its use, particularly 

 if used in comparison with other phcsphatic materials which do not con- 

 tain this element. 



Pure raw bone contains on an average 22 per cent, of phosphoric acid 

 and 4 per cent, of nitrogen. By steaming or boiling, a portion of the 

 organic substance containing nitrogen is extracted, which has the effect 

 of proportionately increasing the phosphoric acid in the product ; hence 

 a steamed bone may contain as high as 28 per cent of phosphoric acid 

 and as low as 1 per cent, of nitrogen. Steamed bone is usually, there- 

 fore, much richer in phosphoric acid than raw bone. 



Tankage is a bone product which, as a rule, contains more nitrogen 

 than bone proper. It is also more variable in its composition, depend- 

 ing upon the proportions of bone and meat used in its preparation. It 

 is not so largely used as a direct fertilizer as bone. 



Other phosphates derived from bone, as boneblack, bone ash, etc., are 

 but little used directly as sources of phosphoric acid ; for while they are 

 derived from organic sources, the treatment which they have received, 

 besides depriving them of their nitrogen, causes them to be a much less 

 valuable source of phosphoric acid than the various forms of bone already 

 discussed. In both cases the organic substances which show the greater 

 tendency to decay have been removed — in the case of boneblack by heating 

 the bone in air-tight vessels, and in bone ash by burning in the open air. 



The mineral phosphates differ from what may be termed "organic 

 phosphates" in that they contain no organic or animal matter, and that 

 they are more compact and dense in their nature. The chief sources of 

 these phosphates are the river and land phosphates of South Carolina, 

 the "soft," "pebble," and "rock" or "bowlder" phosphates of Florida, 

 the " apatites" of Canada, the phosphate mines of Tennessee, and phos- 

 phatic slag, 1 a waste product from the manufacture of steel from phos- 

 phatic iron ores. With the exception of the latter, which is not an 

 abundant product in this country, these phosphates are not yet used to 

 any considerable extent, even when very finely ground 2 without having 

 been treated with acid. They are however, the chief raw materials from 

 which superphosphates are made. 



1 Also known as Thomas Phosphate Powder, Thomas slag, and Odorless Phos- 

 phate. 



2 Finely ground mineral phosphate known as "floats" has been used to a 

 limited extend in some localities. 



