120 THE ROLE OF NITROGEN IN PLANT-METABOLISM, iii., 



By quantitative precipitation with alcohol, in increasing 

 successive concentrations, a differentiation occurs into at 

 least two distinct proteins. The precipitation of the first 

 runs approximately proportional to the concentration of 

 alcohol, from the commencement to 40/^. From 40 to 60% 

 the nitrogen is nearly constant, and a second jirotein is 

 indicated at 60% concentration, by the sudden change in the 

 solubility of the precipitate, and the increase in amount of 

 nitrogen. 



ii. The n o n - p r o t e i n Nitrogen Compounds 



The experimental work may be grouped under the follow- 

 ing headings : — 



A. — Preparation of a protein-free solution containing 

 other nitrogen compounds, and proof of absence of protein. 



B. — Distillation of free ammonia in the solution. 



C. — Hydrolysis by dilute acids under a reflux condenser, 

 and subsequent distillation with magnesia, by Sachsse's 

 method for amides. 



D. — Continued and drastic hydrolysis, involving decompo- 

 sition of substances which yield more ammonia than C. 



E. — Precipitation of basic constituents with phospho- 

 tungstic acid. 



F. — Examination for compounds containing the amino- 

 group. 



A. — The non-protein nitrogen solutions are obtained by 

 two methods, (a) Cold saline extracts are precipitated by 

 tannic acid, lead acetate, and hydrogen sulphide, (b) Hot 

 distilled water extracts are precipitated in 80% alcohol. The 

 alcohol containing the non-protein constituents is distilled e 

 under reduced pressure, the aqueous residue diluted with 

 water, and filtered. Evidence is shown that these solutions 

 are practically protein-free. The solutions contain no nitrates 

 and no alkaloids, and when distilled no nitrogen is found in 

 the distillate. 



