421 



CHAPTER XXVI. 



RESINS, (CONTINUED). 



MASTIC SANDARACH DRAGON'S BLOOD ANIMI 



ELEMI COPAL JAPAN VARNISH BENZOIN LAB- 



DANUM. 



ALTHOUGH the general name of resin is used to de- 

 signate that alone which is obtained from turpentine, 

 there are a considerable number of similar sub- 

 stances obtained from other sources, which are 

 classed under the common term of resin. These 

 are distinguished as being solid, brittle, inflammable, 

 and somewhat transparent substances, of vegetable 

 origin, totally insoluble in water, but soluble in 

 alcohol, volatile oils, and sulphuric ether. When 

 these solutions are evaporated the resin is restored 

 unaltered ; if thinly spread on any surface the alcohol 

 or other solvent will speedily evaporate, leaving the 

 resin behind, to cover the body with a smooth, 

 shining, transparent coat, which cannot be washed 

 off with water. This process is called varnishing. 

 Resin is with difficulty acted upon by acids. Alkalis 

 combine with it, but their combination is not easily 

 effected. 



Resins are considered by chemists to be nothing 

 but volatile oils rendered concrete by their combina- 

 tion with oxygen, and this belief is confirmed by the 

 results of several experiments. 



Mastic is a resinous substance collected in the 

 form of tears; it is of a very pale yellow colour, 

 having but little smell, and scarcely any taste. It 

 forms the basis of several dyeing varnishes, is one of 



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