HIGH GRADE NITROGKNOUS FKRTILIZKK MATKRIALS 53 



Tankage is composed entirely of animal matter. It is the re- 

 fuse from slaughter houses and consists of meat, bone, etc. (from 

 which the fat has been extracted) and more or less dried blood. 

 Animals condemned as unsuitable for food are made into tankage. 



The phosphoric acid in tankage is slowly available as it is sup- 

 plied principally by ground bone. The nitrogen is derived prin- 

 cipally from meat and blood. When the percentage of bone 

 is large, the phosphoric acid is high, and the nitrogen content is 

 low, and when there is an excess of blood and meat, the ni- 

 trogen is high and the phosphoric acid low. 



Grades of Tankage. — There are several grades of tankage found 

 on our markets. The most popular nitrogenous grades are those 

 containing 8, 9, and 10 per cent, ammonia which are equivalent 

 to 6.58, 7.41, and 8.23 per cent, nitrogen, and 6.56, 7.64, 10, and 

 12 per cent, bone phosphate of lime, which are equivalent to 

 3> 3-5) 4-58. and 5.5 per cent, phosphoric acid. There are many 

 other grades of tankage sold that carry more phosphoric acid and 

 less nitrogen, but these are classed as bone tankages and will 

 be later described under phosphates. 



Concentrated tankage is still another grade and the richest 

 of all since it contains more nitrogen and is a more uniform 

 product. It is made by evaporating, wastes that contain animal 

 matter in solution, or in other words the tank water. It us- 

 ually contains 10 to 12 per cent, nitrogen and small amounts 

 of phosphoric acid. 



Variation in Tankage. — Because of the great variation in the 

 chemical composition of tankage (no two shipments hardly ever 

 run alike, for the manufacturers cannot seem to control the com- 

 position of their output on account of the variation in the by- 

 products), great care must be exercised in purchasing. The prod- 

 uct should be bought on its chemical composition and not nec- 

 essarily on its guarantee, for it may or may not reach its stated 

 composition. Hoof meal and hair are sometimes present in 

 shipments of tankage. For sugar-cane, cotton-seed meal has 

 been found to be more valuable than tankage of the same ni- 

 trogen content. Nevertheless, tankage is a valuable fertilizer 



