104 



Fahrion considers that the polymerisation of wood oil is not 

 analogous to that of styrol. Polymerised styi'ol, on further heating, 

 yields styrol, but not so in the case of wood oil (Farb. Zeit., 17, 25, 83, 

 1912, and Ber., 49, 11, 94, 1916). Schumann concludes that a 

 dipolymerised glyceride is first formed which has the power of forming 

 molecular complexes under favourable conditions, giving an insoluble 

 coUoidal mass, not, however, accompanied by any further loss of 

 double linkages beyond those diappearing in the first stage of the 

 change. 



The presence of decomposition products from the oU prevents the 

 gelation; rosin has the same effect. The soHd gel is stated to be 

 transformable into the dipoljrmer on heating with rosin or with the 

 decomposition products of the oU. It is stated that if the decomposi- 

 tion products of linseed oil are removed while the oil is heated linseed 

 oil will gel rapidly. Schumann concludes that the polymerisation 

 is mesomorphic. 



The writer (MorreU, J.8.C.I., 37, 181, 1918) can confirm the 

 formation of the dipolymer ^Wth its subsequent gelation, but he 

 AV'ishes to lay stress on intramolecular changes occurring during the 

 heating of other drying oils ; thus Cyclohn or Polyolin (sohd polymerised 

 linseed oU) is difficult to saponify, insoluble in amyl alcohol and is 

 considered by de Waele to be of a ring structure (Jour. Ind. Eng. 

 Chem., 19, 1, 1917). 



Krumbhaar states that the speed of polymerisation of Tung oil 

 constitutes the greatest difference between it and linseed oil, and 

 agrees mth Fahrion that the polymerisation product is partially 

 soluble in the unchanged oU. The viscosity increases Avith the amount 

 of the polymer untU saturation is reached, when the polymer is thrown 

 out. (Chem. Zeit., 40, 937, 1916.) 



This property of thickening is only markedly shown by the more 

 liighly imsaturated oUs of the open chain series. Union of molecule 

 with molecule undoubtedly occurs and the polymeride remains 

 dissolved in the Hquid oil with increasing viscosity until the fluid 

 coagiilates. In the writer's esperience half the oil has been poly- 

 merised short of the point of setting, beyond that point the mass 

 consists of a gel of the dipolymeride whose viscosity is influenced by 

 the presence of specific substances as in the case of gelatine in water. 



The problems of polymerisation and of thickening of drjong oils 

 are of the highest practical importance. Further investigation of 

 the Polyolin of China wood oil would throw fight on the properties 

 of the thickened oils, especially in their emulsions in water and in other 

 media. 



The formation and properties of linoxyn, the oxidation product 

 of linseed oil, are those of a gel, due to oxidation and not to heat, as 

 in the polyolins or cj-clofins (Annual Reports of the Society of Chemical 

 Industry, 1916-18). In the manufacture of linoleum (A. de Waele, 

 Jour. Ind. andEng. Chem., 9, 1, 1917, and M. W. Jones, J.S.C.I., 1919, 

 38, 26) four oxidation products result of wliich linoxyn is one. These 

 diiier in degree of oxidation and finoxyn may be considered as solid 

 oxidised linseed oil. It must again be noted that the degree of 

 unsatiu'ation plays an important part, because olein gives no linoxyn 



