10 COMMERCIAL TURPENTINES. 



become thoroughly liquid, and the cap is replaced in position and 

 connected with the condenser while the heating of the kettle is 

 slowly continued. Slow, cautious heating is made necessary by the 

 presence of water in the gum, which causes frothing when the gum 

 begins to boil, and if the heating is unduly hastened the gum will 

 froth over, causing loss and delay. The presence of water in the 

 gum lowers the boiling point of the mixture, so that both turpentine 

 and water begin to distill at about 94 to 95 C. (201 to 203 F.) ; 

 alone it distills at from 155 to 170 C. (311 to 338 F.). 



When the danger of frothing over has passed, which means usually 

 that most of the water has boiled off, a small stream of water is 

 allowed to run into the still through the cap, as in this way the dis- 

 tillation is conducted at a much lower temperature than would other- 

 wise be possible. 



The condensed turpentine and water are collected in a separator, 

 where the turpentine collects on top and may be drawn off from 

 time to time. The separated spirits of turpentine is then run into 

 tight white-oak barrels, which have been well driven and glued to 

 prevent the turpentine soaking through the wood. The barrels are 

 filled to within 1 gallon of their capacity, leaving room for expansion 

 of the turpentine, which takes place with a rise of temperature and 

 would cause leakage if the barrel were filled at the ordinary tempera- 

 ture. The barreled turpentine is then ready for the market. 



The residue in the kettle from the turpentine distillation is rosin, 

 which while still hot is run out of the opening in the bottom through 

 wire screens and then strained through cotton cloth or batting to 

 remove the remaining chips, straw, and dirt, after which it is barreled 

 and cooled. 



When distillation is properly conducted with water all of the 

 turpentine distills below 150-160 C. (302-320 F.), and there is 

 little apparent breaking up of rosin or discoloration of the turpentine. 

 If the temperature is allowed to rise above 160-170 C. (320-338 

 F.) toward the end or the distillation is prolonged, or if water is 

 not used in distillation, both the turpentine and the rosin are darker 

 colored. 



The color of turpentine is due primarily to overheating the gum 

 and possibly partly to the chips, pine straw, etc., left in the kettle 

 during the distillation. Wood begins to color decidedly above 150 

 C. (302 F.), so that it is almost impossible to make a colorless 

 rosin if there are any chips or bark in the still. Prolonged heating 

 of the rosin at 130 C. will lower the color several grades. Hence, 

 to make turpentine and rosin having but little color the gum should 

 be free of wood, bark, and pine straw, the contents of the still should 

 never rise above 160 C. at any point, and the distillation should 

 be conducted as rapidly as is practicable. 



