ANALYSIS, RfcKININCi, AND COMPOSITION. 



11 



FRACTIONAL DISTILLATION. 



Five hundred grams of the turpentine to be analyzed are weighed 

 in a round-bottomed flask of about 1,000 cubic centimeter capacity; 

 the flask is connected Avith a condenser by a Hempel column of the 

 shape and .size shown in figure 1, in the top of which is placed a 

 thermometer with the bulb reaching to within 1 inch of the beads. 

 The flask is heated on a sand bath or a piece of asbestos board and, 

 in order to keep the liquid boiling smoothly, without 

 bumping, a small flat coil of copper or nickeled wire 

 is laid on the bottom of the flask. If the room tem- 

 perature is very low a shield of asbestos board 

 around the flask may also be desirable. The (list ilia - 

 lation is carried on at a maxi- 

 mum rate of two drops a sec- 

 ond 1 and the distillate is 

 caught in weighed flasks of 

 about 100 c. c. capacity. 

 Neither the size of the fractions that is, the 

 amount of distillate to be caught in each separate 

 flask nor the amount of undistilled residue to be 

 left in the distilling flask can be definitely speci- 

 fied, since the proper amounts may vary with 

 different kinds of turpentines. In general, how- 

 ever, the fractions may well be larger (10 to 12 

 per cent) when the temperature of the distillation 

 is changing slow r ly and regularly, but should be 

 smaller (4 to 5 per cent) when the temperature is 

 changing rapidly. Usually, also, it is unneces- 

 sary to continue the distillation after a tempera- 

 ture of 180 C. (corrected) is reached, because 

 this seems to be the temperature below which 

 almost all of the turpentine materials are distilled 

 over and above which the heavy oils begin to come 

 over in large quantities. This is especially true in 

 the case of wood turpentines. With gum turpen- *io.i.-Hempdcoi, 

 tines and some wood turpentines, however, especially those with a 

 small amount of heavy oil, the turpentine materials are all distilled 

 over before this temperature is attained. 



There are many details of manipulation which can not be com- 

 pletely specified in a method, which is to be applied to materials of 



1 A slower distillation gives, of course, a better fractionation, and the maximum rate 

 mentioned should never be exceeded ; there should, moreover, be no tendency to hasten 

 the distillation in order to save time, because the work of determining the amount and 

 properties of the fractions can be carried out at the same time as the distillation. In- 

 deed, a moderately rapid and experienced worker, with all the apparatus handy, can make 

 the necessary determinations and computations, and can record and plot the results on 

 six or seven fractions, while nine or ten are being distilled. 



