194 RICHMOND. 



Second fraction, 200° to 250° ; 13.3 grams of reddish oil which contained no 

 water. 



Third fraction, 250° to 300° ; 35.5 grams of greenish, mobile oil. 

 Fourth fraction, 300° to 350°; 191 grams green oil. 

 Residue, above 350°; 98 grams by difference. 



Nearly 65 per cent of the crude distillate boiled between 250° and 

 350°. The properties of this main fraction showed a general agreement 

 with those of the known diterpenes and it is regarded as belonging to 

 this class of compounds. 13 



CHANGES WHICH TAKE PLACE WHEN "MANILA COPAL" IS FUSED IN AN OPEN 

 RECEPTACLE OVER A FREE FLAME. 



The surfaces of the pieces first soften and adhere to each other and to 

 the sides of the kettle. As the heating is continued the resin becomes 

 less viscous and sticky and can readily be stirred, and heavy, gray vapors 

 of a strongly acid reaction are thrown off. During the disengagement of 

 the steam and acid fumes the semifluid mass froths and shows a tendency 

 to rise over the sides of the kettle unless constantly stirred, and some- 

 times the removal of the flame is necessary .to prevent loss in this manner. 

 Eventually, the fused mass subsides to a clear, dark, amber-colored 

 mobile fluid which boils gently at a temperature between 300° and 350°. 

 Upon cooling, the solution quickly becomes viscous and finally sets to 

 a transparent, glassy mass which may readily be powdered. 



The copper kettles employed in varnish factories for melting Manila 

 copal become coated with a greenish incrustation which is undoubtedly 

 due to the action of the acid fumes liberated during the melting process. 



That profound chemical and physical changes take place when organic 

 matter like resins and vegetable oils are subjected to elevated temper- 

 atures is very manifest. 



A study of the finished product offers almost insurmountable difficulties in 

 the way of determining its composition, for the varnish is a mixture of complex 

 ingredients rendered still more complex by the temperature to which they are 

 subsequently subjected. No better illustration of this fact can be cited than the 

 results obtained in this laboratory on a sample of varnish manufactured by a 

 well-known and reliable firm and claimed by them to consist only of resin and 

 vegetable drying oil and containing no resin oil whatever. Exhaustive examina- 

 tion of the varnish in question showed conclusively the presence of resin oil, 

 which, if not added directly, is undoubtedly a product of the process of manu- 

 facture. 



It would seem that a much better method of attacking the problem 

 of what an oil varnish consists of and the changes which the raw materials 

 undergo during the process of its manufacture would be to study the 

 effect of heat upon the unmixed ingredients ; for, aside from the possible 

 difference in the effect of heating the oil and the resin for the same 



15 For a detailed study of the dry-distillation products of Manila copal see 

 Brooks, This Journal. See. A : 5, 203. 



