ADVANCED PHYSIOLOGICAL CHEMISTRY 449 



mum sulphate crystals. This precipitates most of the proteases. Filter 

 and wash the precipitate with saturated ammonium sulphate solution. 

 Preserve the filtrate and washings which contain peptone and traces of 

 secondary proteoses (label it ), and proceed to examine the precipitate 

 (label it A). 



(4) Dissolve the proteose precipitate A in distilled water. Remove 

 samples from the resulting solution, and apply the tests for proteoses 

 (nitric acid, salicyl sulphonic acid, biuret, etc. (see p. 223). Place the 

 remainder in a large evaporating dish, and boil with powdered barium 

 carbonate till no more ammonia gas is evolved. This removes 

 ammonium sulphate from the solution, the barium uniting with the sul- 

 phuric acid to form insoluble barium sulphate, and the liberated carbonic 

 acid and ammonia being driven off by the heat. Filter. The filtrate 

 contains the proteoses. Saturate it with sodium chloride. A precipitate 

 of primary proteoses results (label it (7). Filter. The filtrate contains 

 the secondary proteose which has not been precipitated by sodium 

 chloride (label it D). The precipitate of primary proteoses (C) is 

 washed with a saturated solution of sodium chloride, and dissolved 

 in distilled water. The resulting weak saline solution is placed in a 

 dialyser against running water for several days, and then against 

 distilled water. The precipitate, which forms in the dialyser, is hetero- 

 proteose as this is insoluble in distilled water. Collect it on a filter 

 paper, wash and dry. The filtrate contains proto-proteose, which may 

 be precipitated by the addition of alcohol, and the precipitate filtered 

 and dried. The filtrate (D) containing secondary or deutero-proteose is 

 acidified with acetic acid, whereby the proteose is precipitated. It is 

 washed with alcohol and dried. 



The Impure Peptone Solution (B) is now saturated with ammonium 

 sulphate crystals at boiling temperature, first in acid reaction, and 

 then in alkaline reaction. It is then cooled and filtered. By this 

 means all traces of proteose are removed. The filtrate is then boiled 

 with solid barium carbonate till no more ammonia is given off, cooled, 

 and filtered. The peptone in the filtrate may be precipitated by adding 

 alcohol. The peptone, thus obtained, is of two kinds, anti- and hemi- 

 peptone. These may be separated from one another by subjecting the 

 powder to tryptic digestion, whereby the hemi-peptone is further 

 digested, the anti-peptone remaining unchanged (see Tryptic Digestion, 

 p. 226). Anti-peptone, prepared by this method, has recently been 

 shown to be impure containing both basic and acid organic substances. 

 By another method of preparation (precipitation with iron salts) 

 Siegfried has however shown that such a body does actually exist 

 and appears to be identical with carnic acid (see p. 445). 



2F 



