IDENTIFICATION OF FERTILIZER MATERIALS. 13 



Tankage is rather heterogeneous. Particles of bone and other 

 animal matter are present. It has an empyreumatic odor. 



Garbage tankage, on account of its extremely various and hetero- 

 geneous nature, can not be identified as a unit. Its heterogeniety, 

 however, affords an indication of its nature. 



Fish scrap has a characteristic odor. Flesh and bones are present. 

 The general microscopic appearance of the material and its odor will 

 usually serve to identify it. 



Lime, both quick and slaked, can be easily identified chemically. 



Superphosphate, in addition to water-soluble phosphoric acid and 

 calcium sulphate, contains quartz and various other mineral particles. 

 This can be best seen by leaching the material and studying the 

 residue with the microscope. 



Dissolved bone black contains much carbonaceous matter besides 

 phosphoric acid, calcium sulphate, etc. 



It thus appears that by far the larger number of the substances 

 examined admit of positive identification. The exceptions are sus- 

 ceptible of such tests as will at least indicate their nature. There 

 seems to be no doubt that by combining microscopic, petrographic, 

 and chemical methods of examination reliable information can be 

 gained as to the nature of the compounds constituting practically all 

 fertilizers. 



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