130 Cellulose 



standing. On treatment with a reducing agent such as dilute 

 sulphurous acid, the coagulum swells to a deep blue transparent 

 jelly. 



This interaction of gelatin and ferric ferricyanide is there- 

 fore rather of the character of a simple coagulation or combina- 

 tion of colloids by dehydration. 



We have reason for assuming a similar relationship between 

 the fibre-colloid and the ferricyanide as the first cause of the 

 precipitation. The conversion of the colourless into the 

 coloured cyanide may be then accounted for by what we know 

 of the constitution of the fibre-substance. 



We have in this complex all the conditions (i) for a 

 deoxidation of Fe'", (2) for union with ferric and ferrous 

 oxides, and (3) combination with HCN. 



Such changes as would be determined by these relations, 

 when brought into play, are of the minor order and consistent 

 with the characteristics of the product, i.e. an intimate mole- 

 cular union of the complex fibre-substance, slightly oxidised at 

 the expense of ferric oxide, and the ferroso-ferric cyanide. 



Further investigation has confirmed the interpretation 

 given in the communication which is reproduced above. It is 

 evidently a reaction in which the entire fibre -substance takes 

 part. The ferroso-ferric cyanide being a saline compound, and 

 the lignocellulose containing both acid and basic groupings in 

 combination, and being in that sense analogous to the inorganic 

 salts, the reaction may be regarded as in the main a species of 

 double-salt formation. In this respect it stands on the same 

 footing as the majority of dyeing reactions. But in the forma- 

 tion of the blue ferroso-ferric cyanide from the red ferricyanide 

 the special chemistry of the lignocellulose comes into play. 

 It may be fairly assumed that the deoxidation of the ferric 

 oxide is due to aldehydic groups, the fixation of hydro- 

 cyanic acid may be referred to aldehydic and ketonic oxygen, 



