80 PROTEIN POISONS 



one-half times its weight of strong hydrochloric acid under a 

 reflux condenser until it failed to respond to the biuret 

 test. The humus substance was filtered out, repeatedly 

 extracted with hydrochloric acid, and the concentrated 

 extracts added to the filtrate from the humus. From this 

 filtrate glutamic acid was isolated as a hydrochloride by 

 saturation with hydrochloric acid gas and standing for some 

 days in the ice-box. The deposited glutamic acid was 

 collected on a filter with the aid of a pump. The filtrate 

 was concentrated in vacuo to a syrup, diluted with an equal 

 volume of alcohol, and esterified by saturating with hydro- 

 chloric acid gas, the solution being warmed to complete 

 the esterification. The alcohol was distilled off at a tem- 

 perature under 40, more alcohol added, and removed by 

 distillation, this being repeated three times. At this point 

 glycocoll, as the hydrochloride of the ethyl ester, crystal- 

 lized out on account of difficult solubility in alcohol. For 

 convenience, the thick syrup containing the esters of the 

 hydrochlorides of the amino-acids was divided into portions 

 and each treated separately but in the same way. The 

 syrup was diluted with half its volume of water, cooled in a 

 freezing mixture, and made slightly alkaline with sodium 

 hydrate. This alkaline solution was extracted with ether, 

 the liquid being kept alkaline by the addition of a few drops 

 of a saturated solution of sodium hydrate. The liquid was 

 then converted into a paste by the addition of solid potas- 

 sium carbonate and repeatedly shaken with ether. The 

 combined ethereal extract was dried by shaking with solid 

 potassium carbonate for a short time, and by being left for 

 twelve hours over fused sodium sulphate. The ether was then 

 distilled off and the free esters subjected to fractional dis- 

 tillation in vacuo. The highest vacuum that I was able to 

 obtain varied from 20 to 30 mm. The pasty mass left after 

 the distillation of the esters, according to Abderhalden's 

 recommendation, was made acid with hydrochloric acid, 

 concentrated, and the inorganic salts allowed to crystallize. 

 The filtrate freed from these crystals was again esterified. 

 furnishing a further but smaller amount of esters. 



