MANILA COPAL. 187 



THE EESIX ACIDS. 



Over 80 per cent of the crude resin is soluble in dilute aqueous solu- 

 tions of the fixed alkalies and is precipitated as a pale yellow, amorphous 

 resinous solid when neutralized. Like the original resin, it has no well- 

 defined melting point, but begins to soften at 100° and fuses to a clear, 

 viscous, amber-colored resin with slight decomposition at 150°. It is 

 completely soluble in ethyl alcohol and phenol, partly soluble in ether, 

 benzene, and chloroform, and very slightly soluble in petroleum ether and 

 ligroin. Its solution in absolute alcohol is partly precipitated with 

 alcoholic potash or alcoholic lead acetate in slight excess. 



The alcohol soluble -and insoluble potash salts were approximately 

 separated in about equal proportions by decantation of the neutral alco- 

 holic solution. The latter was evaporated, the residue dissolved in water, 

 and the free resin acid liberated with dilute hydrochloric acid. The resin 

 acid thus obtained could not be crystallized. It began to soften at about 

 70° and was quite fluid at 100°. It was completely soluble in ether 

 and contained an acid soluble in a dilute solution of ammonium carbonate. 



Tschirch and Koch 10 obtained a crystalline acid by extracting an ether solution 

 of soft Manila copal with a 1 per cent solution of ammonium carbonate, to which 

 he assigned the formula C s H 12 O s , based upon elementary analyses, molecular weight 

 determinations, and analyses of its potassium salt. The acid crystallized from a 

 mixture of ethyl and methyl alcohol in needles. Its melting point was 175° 

 and a 2 per cent alcoholic solution gave a rotation of 2° 24'. 



From Kauri copal {Darnmara australis) he obtained 11 a crystalline acid in 

 the same manner which melted at 192° and which gave a rotation of 2° 24'. Its 

 analysis and meloeular weight corresponds to the composition C in H li; 0o. 



To obviate the tediousness of repeated extractions with 1 per cent 

 ammonium carbonate which Tschirch experienced, the etherial solution 

 of the resin acid was shaken with a large excess of 5 per cent ammonium 

 carbonate solution in a 10-liter bottle on a motor-driven shaking machine 

 for several days. A vent through the stopper of the bottle allowed of 

 equalization of the pressure. Complete extraction gave 4 per cent of 

 an acid calculated on the amount of the original resin. It was precip- 

 itated in an amorphous form -when the ammonium carbonate solution 

 was acidified. It was dissolved in dilute alcohol, from which it crystal- 

 lized upon long standing in the cold in needles. The recrystallized acid 

 was perfectly white and melted at 185° to 187°. In addition to the 

 solvents of the crude resin acids, the crystalline acid is also completely 

 soluble in ether, benzene, methyl alcohol, and chloroform. 



10 hoc. cit., 209. 



11 Arch. d. Pharrn. (1901), 239, 152. 

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