118 Messrs Morrell and Crofts, Modes of Formation of Osones. 



zones, and reduces strongly a Fehling's solution. The dioxim has 

 not' been obtained crystalline. An aqueous solution of the dioxim, 

 on being allowed to stand with phenylhydrazine at the ordinary 

 temperature, gives phenylrhamnosazone (mp. 178°). 



The third method for transforming carbohydrates into osones 

 is by careful oxidation of hexoses or pentoses, in dilute aqueous 

 solution, by hydrogen peroxide in the presence of a small quan- 

 tity of ferrous sulphate [Morrell and Crofts, J.G.S. Lxxv. 786 ; 

 lxxvii. 1219, lxxxi. 666; Cross, Bevan and Smith, J.G.S. lxxiii. 

 463]. 



Hydrogen peroxide and ferrous sulphate, acting as oxidising 

 agents, have been referred to earlier in this paper in connection 

 with the oxidation of mannitol to mannose, and these combined 

 oxidising agents have been used by Fenton to transform tartaric 

 acid into dihydroxymaleic acid [Fenton, J.G.S. lxv. 899]. 



In the oxidation of a carbohydrate by hydrogen peroxide in 

 the presence of ferrous sulphate, the peroxide must be added in 

 small quantities at a time. The ferrous iron is first oxidised to the 

 ferric state and slowly passes back to the ferrous condition. 

 The action of the ferrous sulphate may be compared with that of 

 manganous sulphate in cases of oxidation by oxydases. 



According to Bertrand [Gomptes Rendus, cxxiv. 1356] manga- 

 nese is present in combination as a manganous salt in oxydases, 

 and is transformed into manganese dioxide by the oxygen 

 rendered active by the enzyme ; the manganese dioxide acts as 

 an oxidiser, and is reduced to manganous oxide, which combines 

 with the acid albuminous material present to form a manga- 

 nous salt. 



Bach and Chodat [Ber. xxxv. 2466] have stated that they 

 have discovered the formation of peroxides in living cells of plants, 

 caused by the action of a class of enzymes known as oxydases or 

 oxygenases. In addition to these enzymes Bach and Chodat 

 have shewn the existence of peroxydases, which possess the power 

 of making active the hydrogen peroxide formed by the oxygen- 

 ases. It was difficult to separate peroxydases from oxygenases, 

 though a partial separation could be effected by dialysis, the per- 

 oxydases passing through the dialyser into the water [Bach and 

 Chodat, Ber. xxxvi. 606]. The peroxydases contained small quanti- 

 ties of manganese and aluminium, but no iron. They possessed no 

 reducing properties towards a Fehling's solution, and were not 

 oxidisers [Bach and Chodat, Ber. xxxvi. 600]. It would appear 

 as if the oxydases were reducers, absorbing oxygen to form per- 

 oxides, which in the presence of an ' acceptor ' give up their active 

 oxygen. The acceptor passes this oxygen on to any easily oxidisable 

 substance. Investigations on the action of autoxidisers such as 

 benzaldehyde in the presence of metallic salts (peroxydases) are in 



