14 COMMERCIAL TURPENTINES. 



The methods as applied to the samples analyzed in this investiga- 

 tion are as follows: 



Specific gravity was determined with the Westphal balance at 20 C. 



Refractive index was determined at 20 C. with the Zeiss refractometer. 



Color was determined by means of the Lovibond colorimeter, and is, for simplicity 

 of standardization, expressed in terms of the depth in millimeters of the liquid which 

 gives a color equal to the Lovibond tintometer glass No. 1 yellow. 



Distillation. One hundred and fifty cubic centimeters of turpentine were put in a 

 200 cc flask having a neck 20 mm in diameter and the side tube 10 cm from the bulb. 

 The bulb of an accurate thermometer was placed opposite the side tube, the flask 

 set in a glycerin or oil bath, connected with condenser, heated, and distillation 

 conducted at the rate of two drops per second. 



The results obtained on the commercial samples have not been cor- 

 rected for the emergent stem of the thermometer, and for this reason 

 the recorded readings are on the average, by actual comparison, about 

 3.5 lower, and as a maximum on the higher boiling fractions, about 

 6 lower, than the actual temperatures. Neither has correction been 

 made for variation in barometric pressure. The most serious conse- 

 quence of not making these corrections is found in determining the 

 exact initial distilling point and the percentage of turpentine distilling 

 at successive temperatures. As a matter of fact, these corrections 

 would have but little effect in the case of a normal turpentine on the 

 total percentage distilling below the upper limit for turpentine, which 

 may very properly, as the work indicates, be put at 170, when the 

 reading is taken with the scale of the thermometer entirely within the 

 neck of the distilling flask. 



EFFECT OF EMERGENT THERMOMETER. 



The differences in temperature readings, due to emergent stem, and 

 the effect of these differences on the quantity of turpentine distilled 

 at various temperatures as determined by actual comparisons, are 

 shown in the following table. In all cases the bulbs of the thermom- 

 eter were opposite the side neck of the flask. 



