34 



BULLETIN 314, U. S. DEPARTMENT OP AGRICULTURE. 



is poured into the filter tube, the temperature of which has been, 

 reduced to —20° C. From one to two grams of the well-mixed dis- 

 tillate obtained in the manner previously described is then accurately 

 weighed in a 100 cubic centimeter Erlenmeyer flask, mixed with 10 

 cubic centimeters of Squibbs' ether, and poured into the filter tube. 

 Ten cubic centimeters of absolute alcohol is next placed in the flask 

 to wash out the ether solution, poured into the filter tube, and the 



coyer carrying the 

 thermometer placed 

 on the tube. The 

 mixture is maintained 

 at a temperature of 

 -20° C. for 15 min- 

 utes, then the cork 

 stopper is removed 

 from the outlet of 

 the filter tube and 

 the filtering flask is 

 replaced. The corks 

 supporting the ther- 

 mometer are now 

 loosened and a strong 

 suction is applied to 

 the filter flask until 

 all of the solvent is 

 drawn off. The con- 

 tents of the filter tube 

 are next washed with 

 10 cubic centimeters 

 of a 1 to 1 mixture of 

 Squibbs 7 ether and ab- 

 solute alcohol, which 

 is chilled to -20° C. 

 in the filter tube be- 

 fore suction is applied. 

 When the washings 

 have been removed the vacuum is turned off and the filter tube removed 

 from the apparatus. The filter tube is then placed in a clean filter 

 flask which also contains a 6-inch test tube in which the dissolved 

 paraffin scale is later collected. About 10 cubic centimeters of warm 

 petroleum ether is poured into the filter tube and allowed to remain 

 until the paraffin scale has been dissolved! Vacuum is then applied 

 and the dissolved scale drawn into the test tube. This treatment is 

 followed by two washings, one of 10 cubic centimeters and the other 

 of 5 cubic centimeters of warm petroleum ether, which removes the 

 last traces of paraffin scale. The entire contents of the test tube are 



Fig. 17.— Freezing apparatus for determining paraffin scale. 



