136 AMPHO-PEPTONES. [BOOK II. 



Methods of Preparation of A mpho-peptone. 



It appears desirable to describe in the first instance the methods 

 which have been employed in preparing . the mixed peptones, by 

 several investigators of repute, and then those modifications will be 

 pointed out in them which the progress of research has suggested. 



Hennlnger's Henninger 1 has made careful researches on the peptones 



method of pre- obtained by the peptic digestion of fibrin, albumin and 

 paring pep- casein, employing the following method of preparation. 



The proteid substance, whose peptone was required, was 

 purified as completely as possible and was then digested with five times its 

 weight of a solution containing 0*3 per cent, of sulphuric acid, together 

 with pepsin, the temperature being maintained at about 44 C. After 

 digestion had gone on for some time an additional quantity of dilute acid 

 was added, and the digestion continued for three or four days, after which 

 the sulphuric acid which the fluid contained was exactly precipitated with 

 barium hydrate and the filtrate from barium sulphate was concentrated to 

 a syrupy consistence on a warm bath. 



The syrupy liquid was first of all treated with alcohol containing some 

 water; this precipitated some peptone and a large proportion of the colouring 

 matter present. The fluid was now poured, in a thin stream, into absolute 

 alcohol, when the peptone was precipitated it was redissolved in water, 

 and again treated with alcohol containing water, and lastly with absolute 

 alcohol, by which it was thrown down free from colour. The solid was 

 then extracted with ether. 



The method employed by this observer, in preparing 

 thod S peptones of egg- albumin 3 , appears to possess considerable 



merit. 



The whites of 50 60 hard-boiled eggs were reduced to a fine state of 

 division and then digested, during 24 30 hours, in a solution containing 

 1 per cent, of phosphoric acid ; they were then separated from this solution 

 and extracted with hot water, the object being to get rid as much as possible 

 of earthy salts which had been rendered soluble by the digestion in acid. 

 The egg-albumin was then placed in 4 litres of a solution containing 

 0*65 per cent, of H 3 P0 4 , and to this 40 c.c. of a clear dialysed solution of 

 pepsin was added ; the temperature was now raised to 40 C. In about 

 five hours, the whole of the albumin had dissolved, though the process was 

 continued for many hours more. The liquid was now heated on a sand- 

 bath, and freshly precipitated, well-washed PbCO 3 was added, until the 

 clear yellow liquid had a perfectly neutral reaction to litmus paper, and 

 gave no longer the reactions of phosphoric acid, this having been removed 

 as Pb 3 (PO 4 ) 2 . The solution contained a small quantity of lead, but so little 

 that 100 c.c. of aqueous solution of sulphuretted hydrogen sufficed to 

 precipitate it. After separating the lead in this way, the liquid was 



1 Henninger, ' De la nature et du role physiologique des peptones.' Comptes Eendus 

 (1878), Vol. LXXXVI. p. 1413 and 1464. 



2 Herth, ' Ueber die chemische Natur des Peptons und seine Verhaltniss zum 

 Eiweiss (aus dem Lab. von Prof. Maly).' Hoppe-Seyler's Zeitschrift f. phys. Chemie, 

 Vol. i. (1877), p. 277. 



