SEPARATION OF PROTEID 387 



content of the thiocyanate in the unknown body. The process 

 is of great exactitude and permits the rapid determination of 

 thiocyanic acid in the presence of chlorids, cyanids, etc., which 

 remain without action upon the permanganate. In case chlorids 

 and cyanids are absent the thiocyanate can be determined directly 

 by silver nitrate either by weighing the precipitate or by the pro- 

 cess of Volhardt, based upon the precipitation of the silver by 

 thiocyanate in the presence of a ferric salt. The end of the 

 reaction is indicated by the red coloration which the liquid shows 

 when the thiocyanate is in excess. 



338. Separation of Proteid from Amid and Other Forms of 

 Nitrogen in Organic Fertilizers. It may be of interest to the 

 dealer, farmer, and analyst to discriminate between the proteid 

 and other nitrogen in fertilizers, such as oil-cakes, etc. The final 

 value of the nitrogen for plant nourishment is not greatly dif- 

 ferent, but the immediate availability for the use of plants is a 

 matter of some importance. The most convenient process in such 

 a case is the copper hydroxid separation process as improved by 

 Stutzer. 31 The process is conveniently carried out in accordance 

 with the method prescribed by the official chemists. 32 



Total Crude Protein. Determine nitrogen as directed for nitro- 

 gen in fertilizers and multiply the result by 6.25 for the crude 

 protein. 



Determination "of Albuminoid Nitrogen. To 0.7 gram of the 

 substance in a beaker add 100 cubic centimeters of water, heat 

 to boiling, or, in the case of substances rich in starch, heat on 

 the water bath 10 minutes, and add a quantity of cupric hydroxid 

 mixture containing one-half gram of the hydroxid; stir thor- 

 oughly, filter when cold, wash with cold water, and put the filter 

 and its contents into the flask containing the concentrated sulfuric 

 acid for the determination of nitrogen. The filter papers used 

 must be practically free of nitrogen. Add sufficient potassium 

 sulfid solution to completely precipitate all copper and mercury, 

 and proceed as in the moist combustion process for nitrogen. If 



31 Journal fiir Landwirtschaft, 1880, 28 : 103. 



Chemiker-Zeitung, 1880, 4 : 360. 

 Bureau of Chemistry, Bulletin 107, 1907 : 38. 



