Abstract
The method outlined will serve to supplement the ester method, and to characterize proteins when relatively small amounts of material are available. Two and a half grams of protein are hydrolyzed by 15 to 18 hours boiling with 20 per cent. hydrochloric acid. The solution is concentrated to a syrup, then transferred to a one-liter Claissen distilling flask with 200 cubic centimeters of water. Saturated barium hydrate solution to 25 cubic centimeters excess is added and the ammonia is distilled in vacuo into N/10 sulphuric acid from a bath at 45° C. The residual solution is acidified with sulphuric acid and boiled while silver sulphate is added until all the hydrochloric acid is precipitated. The precipitate, which carries the melanine with it, is Kjeldahled to determine the melanine nitrogen. The filtrate is brought to 100 cubic centimeters and 5 cubic centimeter duplicates taken for total and amino nitrogen determinations. 1
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