212 BROOKS. 



Further investigations of the products given off during the second 

 stage of the decomposition were not undertaken because of the impos- 

 sibility of drawing an} 7 conclusions from them as to the nature of the 

 original substances. The complete distillation of Manila copal is more- 

 over not a commercial practice. 



The fact that high-boiling resin oils are carried over by the gases 

 shows that a certain amount of resin oil must be left in the melt. The 

 presence of resin oil in the melt may in part account for the solubility 

 of the melted resin in linseed oil. 



No chemical examination of the copal oil has been made. The fractions boiling 

 from 190° to 200° probably contain oxidation products of the terpenes contained 

 in the resin. These fractions possess a fine, camphor-like odor and have specific 

 gravities ranging from 0.880 to about 0.910. Guedras 3! has suggested that copals 

 may contain oxidation products of the terpenes. 



Numerous patents have been taken out on processes which have for 

 their object the minimizing of the loss in weight caused by the heating 

 of the resins. 



In some processes the resin oil is condensed and returned to the melting kettle." 4 

 According to other methods the resins are heated under pressure: 5 The resin 

 oil thus retained in the melt undoubtedly assists in the solution of the resin 

 and less heating is probably required than when the oil is lost. 



THE EFFECT OE HEATING MANILA COPAL' ON ITS SOLUBILITY IN OILS. 



The formation of copal oil during destructive distillation at tem- 

 peratures which did not exceed the common working temperature of 

 varnish manufacture suggested that perhaps the presence of this oil 

 in the melted resin plays an important part in the solution of fused 

 copal in linseed oil. 



I have found that copal oil is formed at the common working 

 temperature of varnish manufacture. It assists in the solution of the 

 resin in linseed oil, and samples of melted resin containing a large per 

 cent of copal oil can be dissolved in greater quantities of linseed oil, 

 without separating on cooling, than those having a smaller per cent. 

 If the copal oil is removed from a sample of fused resin by distilling 

 under reduced pressure, the solubility of the residue in linseed oil is 

 much diminished. The substance thrown out of a solution in ligroin 

 or benzene by diluting with ligroin contains no resin oil and is extremely 

 insoluble in linseed oil. It is converted into a dark oil if further 

 decomposed by strong heat, or to pale oil varnish at much lower tempera- 

 tures by the use of partially saponified linseed oil. 36 



sz Gompi. rend. Acad. sci. (1902), 135, 797. 

 M Tixier, Jpum. Soc. Chem. Ind. (1906), 25, 996. 



35 Hempel, Journ. Soc. Chem. Ind. (1901), 20, 818; Smith, Ibid. (1901), 20, 

 1076.; Lippert, Ibid. (1901), 20, 1122. 



38 Richmond. This Journal, Sec. A (1910), 5, 199. 



