248 CHEMISTRY OF THE PROTEIDS CHAP. 



Guckelberger on oxidising casein with manganese peroxide and 

 sulphuric acid found : l 



Aldehydes : acetic-, (?) propionic-, butyric-, benzoic aldehydes. 



Acids: formic-, acetic-, propionic-, butyric-, valerianic-, caproic-, 



benzoic acids. 

 Using chromic acid as the oxidising agent he obtained : 



Nitrites : hydrocyanic acid, valeronitrite. 



Aldehydes of benzoic and probably propionic acid. 



Acids : formic-, acetic-, propionic-, butyric-, valerianic-, caproic-, 



and benzoic acids. 



Seemann obtained from gelatine in addition to formic-, acetic-, and 

 butyric acids probably also propionic- and valerianic acids. He also 

 draws special attention to the fact that on oxidising boiling gelatine 

 or albumin with four times its weight of calcium permanganate, used 

 as a ten per cent solution, he never failed to smell hydrocyanic acid, 

 while Plimmer failed to notice HCN on using manganese peroxide and 

 sulphuric acid or potassium permanganate and sulphuric acid as oxidis- 

 ing media. (See index under hydrocyanic acid.) 



Bernert has drawn special attention to both oxidation and hydro- 

 lysing forces being at work during the oxidation of albumins, and 

 Cohnheim sums up by saying: "The dissociation and oxidation of 

 albumins with caustic potash and permanganate follows therefore the 

 same course as does the ordinary dissociation of albumins. A portion 

 of the albumin is dissociated in the usual manner, and the dissoci- 

 ation-products are then partly converted into final products and partly 

 preserved as intermediate substances. That portion of the albumin 

 which does not dissociate also undergoes a change, for though it 

 contains as much sulphur as does the mother substance, it is not 

 possible to split off more than a small portion of the sulphur by means 

 of lead acetate and sodium hydrate ; it still contains an aromatic 

 nucleus, but not the oxyphenyl group. This last fact may be explained 

 on the assumption that in the benzene-nucleus a change has occurred, 

 analogous to that taking place during iodisation. The most probable 

 explanation seems to be that the hemi-group, which is always readily 

 detached, is removed altogether by oxidation, while the more resisting 

 anti-group and a radical containing the carbohydrate is left over. Of 

 the two aromatic complexes the hydroxylated complex of the hemi- 

 group disappears, while the other one persists. The percentage 

 composition of the products of oxidation seems also to support the 

 suggestion offered, for Pick has shown that the anti- and the hemi- 

 groups (see index) hardly differ from one another as far as their general 

 1 G, Guckelberger, Liebig's Annalen, 64. 39 (1848). 



