CHAP. II.] PREPARATION OF AMPHO-PEPTONES. 137 



concentrated on the water-bath, precipitated with, and afterwards digested 

 in, strong alcohol, again dissolved in water and re-precipitated with alcohol, 

 the process being repeated three^rmes in succession. 



Kuhne and 3800 grams of washed, but not boiled, fibrin were 



Chittenden's digested in two litres of a solution of hydrochloric acid con- 

 method of pre- taming 0'4 per cent, of HC1, with which had been mixed a 

 paring Ampho- purified pepsin obtained from 1220 grams of isolated mucous 

 peptone from membrane of the fundus of the stomachs of two pigs. The 

 mixture was allowed to remain at 37 40 C. for a fort- 

 night, so as to ensure as completely as possible the conversion of albumoses 

 into peptones. At the end of that time filtered portions of the solution 

 gave only slight precipitates on neutralisation, but a heavy precipitate was 

 obtained with ammonium sulphate, with sodium chloride, with sodium 

 chloride and acetic acid, and still further with sodium chloride and nitric 

 acid and with metaphosphoric acid. Nevertheless the filtrate saturated 

 with ammonium sulphate contained much peptone. 



In order to separate and purify the peptone present in the filtrate the 

 following processes were carried out : the filtrate was neutralised with 

 sodium hydrate, filtered through linen, with the special object of removing 

 the impurities of the fibrin, the filtrate slightly acidified with acetic acid, 

 concentrated to about 4 litres, precipitated with an excess of ammonium 

 sulphate, filtered and pressed, the solution boiled with barium hydrate, and 

 finally with barium carbonate and a large quantity of water, until ammonia 

 could no longer be detected. The barium sulphate was then removed by 

 filtration through linen bags which were repeatedly washed and pressed, 

 the solution evaporated to about 4 litres, the barium peptone decomposed 

 with a very slight excess of sulphuric acid, the new precipitate of barium 

 sulphate filtered off, the solution concentrated to 2 litres, the pure acid 

 neutralised with ammonia and, after cooling, 6 per cent, of English 

 sulphuric acid, previously diluted, was added. The sulphuric acid-peptone 

 solution was then precipitated with a large excess of phospho-tungstic acid, 

 the precipitate washed first with 6 per cent, sulphuric acid and afterwards 

 with a large quantity of water, after which the compound was decomposed 

 by means of excess of barium hydrate, and the excess completely removed 

 from the filtrate, by adding sulphuric acid. The peptone solution, thus 

 obtained, had a distinctly acid reaction and, strange to say, contained 

 hydrochloric acid, which was hardly to be expected after the very careful 

 washing which the precipitate had received. 



The solution was neutralised with ammonia, to render the acid 

 harmless on concentration. Then by repeated precipitation, and 

 boiling, with alcohol, some peptone was obtained, which was free 

 from ammonium chloride. 



The peptone, prepared in this way, was most difficult to obtain in 

 a dry state, though it was ultimately converted into a fine exceedingly 

 hygroscopic powder, by long heating in vacuo, at 105 C. In order 

 to effect the drying, the alcohol was first displaced by boiling with 

 water. 



1 Kiihne und Chittenden, ' Ueber die Peptone.' Zeitschrift /, Biolog. Vol. xxn. 

 (1886), p. 425. 



