A NOTE ON PROTEIN PRECIPITATION IN GRASSES. 



By Maegaeet H. O'Dwtee, B.Sc, Science Researcli Scholar in the University 

 of Sydney. 



[Read 27th September, 1922.] 



Dr. Petrie, writing on the amount of non-protein nitrogen found in the seeds 

 of Acacia pycnantha and of various other legumes, cereals, etc., (Pro'c. Linn. 

 Soe. N.S.W., 33 (4), 1908, p. 837) drew attention to the views of several well- 

 known scientists on the precipitation of proteins by Stiitzer's Reagent. He him- 

 self found, as the result of a series of experiments, that tannin and alcohol were 

 practically equal in precipitating power, and that Stiitzer's Reagent (copper 

 hydroxide) precipitated 13 per cent, more nitrogen than either of the other two 

 reagents. As copper hydroxide is the only reagent mentioned in this connection 

 in the Methods of Analysis of the Association of Official Agricultural Chemists 

 of America (1921), it would appear that no special work on the precipitation 

 of the proteins in feeding stuffs has, so far, been carried out in the United States. 



It occurred to me, therefore, that an attempt to precipitate the proteins in 

 some of the gi-ass samples by the various reagents mentioned by Dr. Petrie might 

 give some interesting results. These are shown in the subjoined Table. It will 

 be seen that higher results are given by Stiitzer's Reagent than by either tannin 

 salt solution, or by alcohol. In Technical Methods of Chemical Analysis (Lunge 

 and Keane, 1911, p. 449) a method based on that of 0. Kellner and worked out 

 by Barnstein is mentioned. The grasses given in the Table have also been 

 treated by this method, but still higher results than those given by Stiitzer's Re- 

 agent have been obtained in each ease. Lunge and Keane state that the results 

 obtained by this method and Stiitzer's have been found to agi-ee in the case of 

 most feeding stuffs, but that vegetable products containing alkaloids and other 

 nitrogenous compounds, such as amides, give a precipitate containing a little more 

 nitrogen when treated by Barnstein's method than when that of Stiitzer is used, 

 this difference, they say. never exceeding 0.2 per cent, of nitrogen. 



ET^jerimental. 



The various preeipitants were prepared as follows, an aqueous extract of 

 the material being made in each ease. 



