8 COMMERCIAL TURPENTINES. 



conditions under which the crude gum is gathered and the time 

 which elapses before it is distilled, by the method of conducting the 

 distillation, and finally by subsequent storage conditions. When 

 the face of the tree over which the crude gum flows before it reaches 

 the box is long, the weather hot, and the gum is kept long before it 

 is distilled, there is more evaporation of the lighter constituents and 

 at the same time the oxidation and polymerization of the gum are 

 increased. It is customary to carry the distillation further on gum 

 from old than from new boxes. The temperature in the final 

 stages of the distillation rises higher, as a rule, and the product 

 obtained near the close of the distillation is more frequently colored 

 or burned. For these reasons turpentine from old boxes, as a rule, 

 is heavier, distills less completely below 170 C., and has a higher 

 refractive index than turpentine made from first-year gum or " virgin 

 dip." 



One of the chief causes of the observed variations in the constants 

 of turpentine freshly distilled from the gum lies in the practice 

 followed in the barreling of the product at the still. From time to 

 time during the distillation the turpentine is transferred to barrels 

 for shipment, and -as a rule the turpentine first distilled is placed in 

 one barrel, the middle portion in another, and the last off in a third 

 barrel. In the earlier stages of the distillation the turpentine having 

 the lowest specific gravity, refractive index, and distilling tempera- 

 ture passes over. As distillation proceeds the distillation tempera- 

 ture, gravity, and refractive index of the distilling turpentine steadily 

 increase, though with occasional lapses and not necessarily propor- 

 tionally. As a result the constants of the turpentine in the first 

 barrel may agree with the lower limits, while that in the last barrel 

 may approach the upper limits recognized for turpentine. 



Because of these conditions, exposure in the woods, variations in 

 distilling, differences in the product at successive stages of the dis- 

 tillation, and changes in composition after distillation, it is cus- 

 tomary to recognize variations in the specific gravity of turpentine 

 from 0.862 to 0.875, in refractive index from 1.4670 to 1.4750, both 

 at 15.5 C., and in the initial boiling point of from 154 C. to 159 

 C. (309 to 318 F.), while the percentage which distills below 170 

 C. (338 F.) varies from about 85 to 99 per cent. 



Old turpentine, even though it is kept in closed vessels, may 

 undergo changes and have a specific gravity as high as 0.9460 and a 

 refractive index of 1.480 or more, while the initial boiling point is 

 raised and the percentage distilling below 170 C. (338 F.) is lowered. 



It is desired in this bulletin to distinguish between old turpentine 

 and 'turpentine to which mineral, coal tar, or other dissimilar oils 

 have been added. While old, highly oxidized turpentines can not 

 properly be classed as normal turpentines, they are, nevertheless, 



