48 GUMS AND RESINS. 



Camphor is a substance fitly associated with oils, since it is a volatile oil in a solid 

 Btate. It is derived from various sources, but the best is the Barus camphor, from 

 Borneo, the product of the Dryobalanope CampJiora, growing in Sumatra. It is chiefly 

 exported to China, where it realises a price one hundred times greater than that of 

 ordinary camphor. Its flavour is exceedingly fine. 



The Dutch camphor, or that obtained by the Dutch from Japan, is prepared by 

 boiling chips of the root ai)d stem with water in an iron vessel, to which an earthen 

 head containing straw is adapted. The camphor is volatilized by the heat, and con- 

 denses on the straw. The process is varied somewhat in the preparation of China 

 camphor. The chopped branches are steeped in water, and boiled until the camphor 

 begins to adhere to the stick used in stirring the fluid. The liquid is then strained, 

 and by standing the camphor concretes. It is then sublimed by placing alternate layers 

 of finely-powdered dry earth and camphor in a copper basin, with a similar one inverted 

 luted upon it, and heat applied, until the camphor passes off, and condenses upon the 

 upper vessel. 



Gums and Resins. These two classes of secretions are distinguished from each 

 other by the solubility of gums and insolubility of resins in water, and the solubility of 

 resins and insolubility of gums in alcohol. In some instances the substance is partially 

 soluble in both menstruums ; in which case it is called a gum-resin. Each of the classes 

 is used abundantly in the arts, and in medicine ; and almost every member of them is 

 obtained from Asia, Africa, and islands of the Southern Sea. 



The cheapest gum is that obtained from roasted starch, and is used largely in calico- 

 printing. 



Gum-arabic, obtained from many species of Acacia and other genera, is carefully 

 collected in Turkey, Egypt, Tripoli, and India. It stands at the head of this series in 

 the quantity imported ; and amounted to 33,136 cwts. in 1849, from the following 

 sources : India, 13,687 cwts. ; Egypt, 6,232 cwts. ; America, 6,OG4 cwts. ; South 

 Africa, 4,876 cwts. ; Italy, 664 cwts. ; Gibraltar, 460 cwts. ; Aden, 397 cwts. ; Australia, 

 372 cwts. ; France, 212 cwts. ; miscellaneous, 172 cwts. It varies very greatly in 

 quality ; and it appears that no very great care is exercised by the collectors in separating 

 the inferior from the better specimens. 



Of gum-senegal and the cherry-gum, or Tragacantha (Astragalus gwninif era), &c., from 

 Syria, there was an importation of 6,577 cwts. and 314 cwts. respectively, in the same 

 year. 



Of the resins and oleo-resins, the most abundant are turpentine and lac, both of which 

 are of essential value in the arts. 



Turpentine is obtained from the fir tribe of plants, and 

 chiefly from the Pinus palustris, by making incisions into 

 it, and subsequently distilling the exuded secretion. It is 

 found in special vessels in the plant, which were dis- 

 covered so early as the seventeenth century by the great 

 vegetable anatomist Green, and also in blisters under- 

 neath the bark (Fig. 94). It is of the utmost value in its 

 power of dissolving resins, and in mixing and drying 

 paints. The quantity imported in 1849 was 412,042 cwts., 

 Fig. 94.-Ite8ervoir8 of secre- nearl y tte whole of ^ hich was from fa Q United g tates of 



America. 

 The distillation of impure turpentine, or turpentine as it is obtained from the tree. 



