CLEAVAGE PRODUCTS OF GASTRIC DIGESTION 



405 



filtrate with i per cent, potassium hydrate. A precipitate makes its appear- 

 ance, and can be collected on the filter-paper, washed with distilled water, 

 and dissolved in i per cent, hydrochloric acid, acid metaprotein. Test 

 for the protein reactions. 



After twelve hours or more filter the remaining 400 cc., exactly neutralize 

 to remove any traces of acid albumin, and filter. The filtrate contains pro- 

 teoses and peptones. Concentrate the filtrate over a water-bath to one- 

 fourth its volume, add an equal quantity of saturated ammonium sulphate 

 solution, a sticky precipitate of primary proteases separates out. Collect on 

 a filter-paper or in a centrifuge, wash with half-saturated ammonium 

 sulphate, redissolved in very dilute salt solution, and test for protein 

 reactions. The primary proteoses are precipitated by nitric acid. 



To the filtrate from the half-saturated ammonium sulphate add crystals 

 of ammonium sulphate until complete saturation with the salt. Deutero- 

 albumoses separate out. Collect on a filter-paper, wash, dissolve, and test 

 for proteins. The secondary proteoses are not precipitated by nitric acid. 



Finally the filtrate contains peptone. It can be isolated and tested by 

 concentrating over the water-bath, adding barium hydrate to slight excess 



