COMMERCIAL FERTILIZERS AND THEIR USE 241 



potash are soluble in water and belong to the first class. 

 In some states the fertilizer laws recognize only the 

 water-soluble potash. In the second class are found 

 materials like tobacco stems and other organic forms of 

 potash. Substances like feldspar, which contain insol- 

 uble potash, are of no value in fertilizers. As a rule, 

 the potash in commercial fertilizers is soluble in water ; 

 in only a few cases are acid-soluble forms met with. 

 Insoluble potash is considered an adulterant 



289. Misleading Statements on Fertilizer Packages. - 



Occasionally the percentage amounts of nitrogen, phos- 

 phoric acid, and potash are stated in misleading ways : 

 as ammonia, sulphate of potash, and bone phosphate of 

 lime. Inasmuch as ammonia contains 14 parts nitro- 

 gen and 3 parts by weight of hydrogen, it follows the 

 ammonia content is proportionally greater than the 

 nitrogen content, because of the additional hydrogen 

 carried by the ammonia. And so with sulphate of 

 potash, which contains about 50 per cent potash and 50 

 per cent of sulphuric anhydride. This method of stat- 

 ing the composition can be considered in no other way 

 than -as a fraud, especially when the fertilizer contains 

 no sulphate of potash, but cheaper materials, and the 

 phosphoric acid is not derived from bone. 



290. Estimated Commercial Value of Fertilizers. 



The estimated value of a commercial fertilizer is ob- 

 tained from the percentage composition and the trade 



