440 COMPOUND PRODUCTS. CHAP. I. 



juice flows. This juice, which is the proper juice 

 of the plant, is then exposed to the action of the 

 sun, by which in warm climates it is condensed 

 and inspissated, and converted into the gum-resin 

 of commerce. 



Properties. Gum-resins in their solid state are brittle, and 

 less transparent than resins. They have generally 

 a strong smell, which is sometimes alliaceous, and a 

 bitter and nauseous taste. 



They are partially soluble bath in water and in al- 

 cohol. When heated they do not melt like the resins, 

 nor are they so combustible. But they swell and 

 soften by heat, and at last burn away with a flame. 

 By distillation they yield volatile oil, ammonia com- 

 bined with an acid, and have a bulky charcoal.* 



Species. The following are the principal species of gum- 

 resins which have been hitherto applied to any 

 useful purpose. 



Galbanum. This substance is obtained from the 

 Bubon Galbanum, a perennial plant found at the 

 Cape of Good Hope. An incision is made in the 

 stem a little above the root, and the milky juice 

 flows out. When it concretes it constitutes gal- 

 banum. It is brought into this country in small 

 pieces composed of agglutinated tears. Its colour 

 is yellow, its taste acrid and bitter, and its odour 

 alliaceous. Water, vinegar, and wine, dissolve the 

 greater part of it, but the solution is milky. 



* Fourcroy, vol. viii. p. 2p. 



