APP. iv.] KUHNE'S NEW METHOD OF PURIFYING PEPTONES. 491 



the albumoses from peptones, the mixture containing these substances 

 should be -saturated, whilst boiling, with ammonium sulphate. In 

 whatever manner it may be carried out, a single saturation with 

 ammonium sulphate is not, however, sufficient to remove all the 

 albumoses. The difficulty, nay, the impossibility, of thus completely 

 separating all traces of these bodies from peptones was pointed out by 

 Neumeister 1 . 



The princi- " The sufficiently diluted mixture, containing albu- 

 pie of Kiihne's moses and peptones having been freed from coagulable 

 new method. albumin and from albumin ates in solution, is neutralised 

 and saturated, at the boiling temperature, with ammonium sulphate. 

 It is then allowed to cool and, thereafter, separated from the 

 crystallised salt and mixture of albumoses which have separated. 

 The filtrate is again heated and, as ebullition is commencing, it is 

 rendered strongly alkaline by the addition of ammonia and ammonium 

 carbonate ; it is then again saturated with ammonium sulphate and 

 allowed to cool. When cold, the mixture is filtered from the second 

 precipitate of albumoses and from the ammonium sulphate which has 

 separated. The filtrate is again heated (boiled) until all smell of 

 ammonia has disappeared, again saturated when boiling with 

 ammonium sulphate and then acetic acid is added, until the reaction 

 is distinctly acid, an operation which leads to a third precipitate, 

 which for the most part separates as the liquid cools. The quantities 

 of the albumoses which necessarily separate are, as would be imagined, 

 very different, according to the nature of the albuminous substance 

 employed; they are, as a rule, greatest after long-continued digestions 

 (i.e. in the latter, the amount of the second and third precipitations is 

 larger, as compared with the first, than in digestions which have 

 extended over shorter periods): it is greater in digestion with pepsin 

 than in digestion with trypsin, and it varies with the nature of the 

 albuminous substances which are acted upon. Thus the precipitate 

 of albumoses which separates when the product obtained by digesting 

 white of egg with trypsin is subjected to the third precipitation 

 previously referred to (viz. when acetic acid is added to the hot 

 solution saturated with ammonium sulphate) is surprisingly abun- 

 dant 2 ." 



Method of ^ n or( ^ er to btain large quantities of peptones free 

 obtaining large from albumoses, Kiihne recommends the use of Witte's 

 quantities of so-called ' peptonum siccum' (refer to page 129), a 

 amphopeptone substance which is prepared by digesting fibrin with 

 (Kuhne). pepsin and hydrochloric acid, and which contains the 



three chief albumoses (proto-, deutero-, and hetero-albumose) in re- 

 markably fluctuating proportions 3 . This preparation must be sub- 



1 E. Neumeister, ' Bemerkungen zur Chemie der Albumosen und Peptone,' Zeitsch. 

 /. Biologie, Vol. xxiv. (1888), p. 267. 



2 Freely translated from Kiihne, op. cit. pp. 2, 3. 



3 The experience of the Author, in reference to Witte's 'peptone,' agrees on this 

 point with that of Neumeister. Two samples which he investigated contained deutero- 



