28 COMMERCIAL TURPENTINES. 



which is in turn connected with the pressure regulator and with the 

 manometer. By connecting a blast or vacuum with the air chamber, 

 which in turn is connected with the free end of the proper tube of 

 the pressure regulator any desired pressure (within the limits of the 

 apparatus) can be produced in the system. The apparatus is shown 

 in figure 1. All corks and- connections must be absolutely air tight. 

 If they are not, the fact will be indicated by the sudden fluctuation 

 of the thermometer when the cock between a receiving cylinder and 

 the pressure flask is opened. 



OPERATION. 



Place 200 cc l of the turpentine and several small pieces of pumice 

 in the distilling flask, connect with the condenser, set the distilling 

 flask in the bath, and heat. Stopper the distilling flask with a cork 

 through which passes a standardized thermometer graduated from 

 150 to 200 C. (302 to 392 F.). The mercury bulb is placed 

 opposite the side tube and the 175 C. (347 F.) mark must be below 

 the cork. Open the stopcock from the air chamber to the first 

 ylinder and also the two-way cock connecting the condensers with 

 the first cylinder, in order that the condensed turpentine may flow 

 into it. According as the pressure is above or below 760 mm connect 

 the pressure regulator with the vacuum or the blast and manipulate 

 the regulator until the manometer indicates in millimeters the re- 

 duced or added pressure needed to bring the pressure within the flask 

 to 760 mm. 2 Heat the bath slowly, and when distillation begins 

 regulate the heat so that the turpentine distills at the rate of 2 

 drops per second. When the thermometer reaches 160 C. (320 

 F.) close the stopcocks to the first cylinder and open those to the 

 second. When the thermometer reaches 165 C. (329 F.) close 

 the stopcocks to the second cylinder and open those to the third. 

 When the temperature reaches 170 C. (338 F.) discontinue distil- 

 lation. Measure or weigh each fraction and determine its specific 

 gravity and refractive index. A polymerization test is also made 

 on each fraction and the residue when it appears advisable. 



When the residue not volatile at 170 C. is large, and it is desired 

 to continue distillation for any purpose, a clean cylinder may be put 

 in the place of the first or second one and distillation continued as 

 long as is deemed necessary. Of course as many fractions may be 

 made as are desired, one with each change of 1 C. in the distillation 

 temperature, or with the distillation of definite volumes. Such a 

 procedure, however, adds but little, if any, information of technical 

 value. 



1 The sample and the fractions may be weighed if preferred. 



2 In exact work the barometer should be corrected to 0. 



