288 INDUSTRIAL PLANTS 



poor in oxygen and rirh in hj'drogcu and carbon, A'ory in- 

 flammable, and, from their largo ]iro]oortion of carbon, burn- 

 ing with a sooty flame. 



More 01' less resinous material is contained in the great 

 majority of ])lants, and in man,y cases it is abundant and 

 valuat.ile for use industrial!}'. Rosin and copal, which are 

 among the most impoi'tant resins, wiU .serve as t^-pical ex- 

 amples. 



Rosin is so mucli the most widely Icnown of resinous ma- 

 terials that it is commonly called ''resin" as if it were the 

 on!}' substance to wliich that name could apply. Chemically 

 it is known as colophony. It is one of the ]ii'oducts obtained 

 by distilling turpentine. What is properly called turpentine 

 as already stated is the ole(jresin which flows from wounded 

 surfaces of pines and similar cone-ljcaring trees. AVhen this 

 is distilled the volatil(> iwirts that pass over and are con- 

 densed form the familiar oil or spirits of turpentine, while 

 the residue is rosin. The largest ciuantities are ]:)roduced in 

 our South(>rn States. Rosin is used as an ingredient in com- 

 mon varnishes, is combined witli tallow in cheap candles, 

 and is extensively used in the making of yellow soap, inferior 

 kinds of sealing-wax, and A'arious cements. In shoemaker's 

 wax and certain medicinal plast(>rs and ointments it enters 

 as an important part. Musicians depend u]ion it to rosin 

 the bows of stringed instruments, tin-men and plimibers 

 use it as a flux in soldering, and it serves man}' other purposes 

 in the industrial world. Its propert}' of generating, when 

 vigorously rubbed, that sort of frictional electricit}- called 

 "resinous" has led to the use of rosin in certain forms of 

 electric apparatus for experimental jnu-poses. 



Copal is a name ajiplied rather indefinitely to a large variety 

 of resins without much in common to distinguish them, but 

 as strictly <l(>fined it is understood to include onl\- such as 

 occur natural!}' in liard masses resembling amfier in appear- 

 ance, and like that substance melting and dissolving only 

 at a comparative!}' higli temjierature — a ])rocess requiring 

 special precautions lo ))reven1 tlie resin and t!i(> soh'cnt from 

 catcliing fire. Tliese resins make the best \'arnislies, and 

 tliat is th(>ir main use. The botanical origin has long hi'ni 



