MANILA COPAL. 195 



period at a given temperature separately, or in admixture, the results 

 should be comparable aud at the same time the problem would be very 

 much simplified. 



Williams 10 examined samples of Kauri and copal not only in their original 

 condition, but also after being subjected to the melting or ''running" process, 

 which is used for converting them into varnish. He observed an appreciable 

 decrease in the acid, saponification and iodine values upon melting. 



Lewkowitsch 17 determined the constants of the more common varnish resins both 

 before and after heating them to 300°. For a reputed specimen of Manila copal 



he obtained the following results: 



Raw copal. Fused copal. 



Acid value 127.6 68.21 



Saponification value 175.17 136.3 



Iodine value 137.9 133.3 



Per cent unsaponifiable 15.98 22.99 



Lewkowitsch also observed that the fused resin gained in weight upon heating 

 for fifteen hours at 100° and noted that this fact indicates oxidation. 



It was . thought that further study of the changes which take place 

 when Manila copal is heated at different temperatures and for periods 

 corresponding to the heating which it subsequently receives in the cooking 

 stage after the oil is added would be of value. 



Experiment 1. — One hundred and twenty grams of nut and thumb sized pieces 

 of mined resin were heated in a porcelain casserole over a free flame with constant 

 stirring with a thermometer until the temperature of the mass reached 250°. 

 At this point the mass was not entirely homogeneous and did not drop freely 

 from the stirring rod. Upon cooling it set to an amber-colored, brittle solid 

 filled with gas bubbles. It weighed 104 grams, a loss of 13.3 per cent. 



Experiment 2. — One hundred and twenty grams of the resin were heated until 

 the temperature registered 275°, when the melted mass was a homogeneous, 

 mobile liquid which dripped from the stirring rod in free, oily drops. The residue 

 weighed 101.5 grams, a loss of 15.4 per cent. 



Experiment 3. — One hundred and twenty-five grams of resin were heated up 

 to 300° and the cooled mass weighed 105 grams, a loss of 16 per cent. 



Experiment .'/. — One hundred and twenty-five grams of resin were heated to 

 325° and the cooled mass weighed 103.3 grams, a loss of 17.4 per cent. 



The residues from experiments 2 and 3 were separated into their constituents 

 exactly in the same manner as the raw resin was treated, namely, dissolved in 

 alcohol, filtered, neutralized with alcoholic potash, and the aqueous solutions of 

 the alcohol soluble and insoluble potassium salts extracted with ether. 



From 100 parts by weight of the fused residues there were obtained 

 the following : 



Experiment 2. Experiment 3. 

 Dirt and foreign matter insoluble in alcohol 0.36 0.4 



Amorphous resin acids the potassium salts of 



which were soluble in alcohol 42.00 ■ 39.5 



Amorphous resin acids the potassium salts of 



which were insoluble in alcohol 

 Neutral oil soluble in ether 

 Neutral resin by difference 



10 Analyst (1898), 23, 254. 

 17 Loo. cit. (1901). 26, 37. 



53.40 



52.7 



0.00 



2.5 



4.24 



4.9 



