DESTRUCTIVE DISTILLATION OF MANILA COPAL. 215 



considerable quantity of high-melting, resinous substance in addition to the copal 

 oil. It melted at approximately 75° to 80°. This residue was melted and mixed 

 with linseed oil, and finally thinned with turpentine, in the same proportions 

 used in the above experiment. Samples taken before and after the addition of 

 turpentine remained clear after cooling. 



It was found that the precipitated portion gave up the solvent by spontaneous 

 evaporation. In a few hours it could be crumbled between the fingers and after 

 twenty-four hours was completely converted into a dark brown powder weighing 

 35 grams. The substance melted at 185° to 190°. It was melted and heated 

 to 230° and the same proportions of linseed oil added as in the first case. Pre- 

 cipitation occurred even at this temperature and test-tube samples, taken before 

 and after the addition of turpentine, gave such an abundant fiocculent precipitate 

 on cooling that the whole appeared as if gelatinized, and the tubes could be held 

 for several minutes in an inverted position without the contents flowing out. 



Since the precipitation method gives only a partial separation of oil 

 and resin, .an attempt was made to remove the copal oil by distilling 

 under reduced pressure. 



A sample of melted resin, the same as was used in the above experiments, was 

 melted and a reduced pressure of 20 millimeters applied. The sample, weighing 

 150 grams, was heated gradually to 200°. The oily distillate collected up to this 

 point weighed 27 grams, or 18 per cent of the amount taken. This was deemed 

 sufficient to determine whether or not the solubility of melted copal was markedly 

 affected by the oil. The distillate was a light yellow, viscous oil having a greenish 

 fluorescence. The portion coming over at about 260° and 20 millimeters pressure 

 had very much the consistency of soft vaseline. The residue left in the flask 

 was extremely brittle and friable. 



A portion of the residue weighing 50 grams was melted and heated to 230°. 

 Boiled linseed oil, heated to a temperature of about 200°, was then slowly added 

 until drop tests showed a marked and unmistakable cloudiness. A small test-tube 

 sample taken at this point also showed an abundant precipitate on cooling. The 

 copal oil which had been removed by distilling under diminished pressure, was 

 then added in the proportions corresponding to the composition of the sample 

 before distillation. The hot mixture was stirred for several minutes, and a drop 

 then tested showed no cloudiness on cooling and small test-tube samples, taken 

 before and after thinning with 25 cubic centimeters of turpentine, remained per- 

 fectly clear after cooling. 



The amount of linseed oil added in the above experiment lip to the point at 

 which unmistakable precipitation occurred on cooling was 130 grams, which is 

 about equivalent to the composition of a 21-gallon varnish, the calculation being 

 made on the weight of the sample before heating. 



For comparison, an experiment was made on a portion of the original 

 melted sample used in the above experiments with the object of determin- 

 ing how much linseed oil could be added to it before partial precipitation 

 would take place. 



The resin was heated to about 230°, as in the previous experiments, and hot 

 linseed oil slowly added until drop tests showed unmistakable cloudiness. The 

 amount of linseed oil used up to this point was found to correspond very closely 

 to the amount required for a 30-gallon varnish. 



