Nitrogenous Fertilizers 



41 



tankage, which is the richer in nitrogen, ranging from 10 

 to 12 per cent, and which contains very little phosphoric 

 acid; and second, crushed tankage, which is of several 

 grades, ranging from 4 to 9 per cent nitrogen, and from 

 3 to 12 per cent of phosphoric acid. Products are some- 

 times sold as tankage, which contain much more than the 

 maximum of phosphoric acid and less than the minimum 

 of nitrogen here given, in which case they are to be classed 

 with bone, rather than with tankage. Tankage varies 

 so much, both in its content of phosphoric acid and nitro- 

 gen, that in the trade it is always sold on the basis of its 

 composition. The percentage of nitrogen and phosphoric 

 acid is distinctly stated, and because it contains very con- 

 siderable amounts of phosphoric acid, its commercial value 

 is not wholly based on its content of nitrogen, as is the case 

 with dried blood, dried meat and concentrated tankage. 

 The market recognizes several distinct grades indicated 

 by the following guarantees : 



Care should be taken in the purchase of tankage be- 

 cause it is sometimes mixed with garbage tankage, a 

 material less valuable and more variable. Adulterations 

 of this kind are not easily detected. They are more 

 common in the less concentrated tankage products. 



