VOLATILE OILS AND RESINS 89 



(c) Copal is a name applied to a number of valuable 

 resins. Some are obtained from living trees in Java, Sumatra, 

 and the Philippines. Others are found as fossils in west 

 Africa, Madagascar, and East Indies. Copal resins may be 

 white, yellow, red, brown, or brownish black. The softer 

 varieties are the recent resins and are readily soluble in the 

 usual solvents. The harder kinds are the fossil resins and 

 are practically insoluble in the usual solvents until they 

 have been melted and partly decomposed, when they dis- 

 solve in hot turpentine or linseed oil. The latter copals 

 are the more valuable. They are complex in composition, 

 consisting largely of acids and resenes. They are used in 

 making .the better grades of varnish. 



(d) Dragon's Blood is found in Sumatra, and is a clear, 

 deep red resin composed of resenes and esters. It is soluble 

 in alcohol and ether, and is used in making red varnishes. 



(e) Lac or Shellac is either a secretion of the lac insect 

 or produced from the plant sap by the sting of this insect 

 on the twigs of certain East Indian trees. It is sold in sticks 

 as "stick lac;" melted, purified, and poured on cold surfaces 

 to cool in thin plates as "shellac;" or poured into moulds to 

 form "button lac." It is pale orange or red when pure, much 

 darker when impure. The red shade is due to a dye secreted 

 by the insect. Bleached shellac is made by passing chlorine 

 through a solution of lac in alkali. This precipitates white 

 lac which is melted and pulled. It is soluble in alcohol and 

 alkalies, partly soluble in ether. Lac is composed of resenes 

 and acids. It is used extensively in varnishes, for stiffening 

 hats, as a constituent of sealing wax, etc. 



(/) Mastic and Sandarac are similar resins found in Africa 

 and Australia, occurring in the form of "tears" or "solid 

 drops" of rather yellow, translucent material. They are 

 partly soluble in alcohol and turpentine, completely soluble 

 in ether. They are composed of acids, resenes, and bitter 

 principles, probably alkaloids. They are used in varnishes 

 and pharmacy, in the latter for tooth cements and plasters. 



79. Some of the Gum-resins, (a) Asafetida is found on 

 the roots of certain plants in Thibet and Turkestan in the 

 form of tears and masses. It is usually yellowish or brownish 



