MANILA COPAL. 193 



surfaces. As is well known, "Manila copal" is employed almost ex- 

 clusively in the varnish industry and together with Kauri copal, a 

 closely related product of the same genus of tree, enjoys the most 

 extensive use of all varnish resins. 



In common with all other resins employed for the same purpose, 

 "Manila copal" is almost invariably heated to such a temperature and for 

 such a period as to render it perfectly liquid. Whether the operation is 

 termed roasting, fusing, melting, or running, the reason is the same, 

 namely, to render the resin miscible with linseed oil. Its behavior on 

 fusion- is therefore, from a practical standpoint, the most important prop- 

 erty to determine. 



ACTION OF HEAT UPON "MANILA COPAL." 



Continued roasting of the powdered resin at 100° causes a slight 

 darkening in color. 



The recent surface resin becomes somewhat softened, but older, mined 

 specimens are not affected at this temperature. Both varieties show 

 a very appreciable gain in weight on continued exposure at 100°. One 

 gram of finely powdered mined resin gained 4 per cent in weight in 

 seventy-two hours. Coarsely powdered surface resin showed a slightly 

 less increase. As both samples contained water and volatile hydrocarbons, 

 a gain in weight under the above conditions is significant of quite pro- 

 nounced oxidation. 



One hundred grams of coarsely powdered copal were placed in a distilling 

 flask and heated continuously for forty-eight hours at a temperature of 100°. 

 Approximate!}- 2 grams of water vapor were condensed. Instead of the equivalent 

 loss in weight the residue showed a slight gain. Coarsely powdered resin in a 

 desiccator over sulphuric acid, either at ordinary pressures or in a partial 

 vacuum, quickly discolors the acid, which in a few days becomes wine red, showing 

 that volatile organic matter is easily liberated under these conditions. 



DRY DISTILLATION OF MANILA COPAL. 



'Five hundred grams of coarsely powdered resin were heated in a large 

 flask connected with a long condensing tube. Some water and aromatic 

 oil was condensed between 100° and 200° as registered by a thermometer 

 in the vapor. 



Considerable care in heating was necessary to prevent the swollen, 

 semifused mass from passing over into the condenser. Finally, the 

 mass subsided and boiled gently with an occasional liberation of gray, 

 uncondensible vapor. Three hundred and fifty grams of greenish-yellow 

 oil were collected below 350°, leaving a pitch-like residue, amounting 

 to 30 per cent of the original copal. 



The oily distillate was fractioned at ordinary pressures without appreciable 

 decomposition. 



First fraction, 140° to 200°; 122 grams of reddish oil containing a little water. 



