770 



CHAPTER VI.* 



EXTRACTION OF OIL OF TURPENTINE AND ROSIN FROM 

 CRUDE RESIN. 



Section I. — Process of Manufacture. 



Casks of crude resin continue to reach the factories at La 

 Teste from March to October, the last consignments being dark- 

 coloured and inferior in quality. From it, oil of turpentine, the 

 chemical formula for which is CioHig is distilled, leaving deposited 

 an oxidised substance which is solid at ordinary temperatures and 

 termed rosin, or colophany. 



These substances are separated from one another in the 

 following way : 



i. By melting and filtering the crude resin, so that the 

 water, sand, pieces of bark and other impurities -f are separated 

 from it. 



ii. By distilling the crude resin, the oil of turpentine and 

 colophany are separated from one another, as these substances 

 have different boiling points. 



The crude resin, after being passed through straw filters, if 

 sufficiently fluid for this to be done, is placed in an uncovered 

 vat (fig. 340, No. 1) and heated until it is completely liquefied. 

 This allows heavy substances, such as sand, &:c., to fall to the 

 bottom of the vat, while light impurities, chips of wood, bark, 

 itc, float on the surface of the melted resin. This is a very 

 delicate operation, as if heated unequally, the resin is liable to 

 catch fire. 



The impurities are then separated from the resin, either by 

 ladling it through straw-sieves, or passing it through a grating 



* [This account is mainly taken from papers by N. Hearle and E. McA. Moir 

 in the Indiun Forester, June and July, ISSf). Both these gentlemen as well as the 

 translator in 1894 visited a resin-factory at La Teste, near Arcachon, belonging to 

 Mr. Lcsca, ami the information given in this chapter has all been supplied 

 through his kindn<"ss. — Tr.] 



t Chiefly larvae of insects. 



