METHODS OF ANALYSIS USED. 19 



refractive index and limpidity. The undistilled portion of pure 

 turpentine when treated in the same way either foamed out of the 

 flask or was instantly reduced to a charred mass and left no measur- 

 able residue. 



ROSIN SPIRITS. 



If rosin spirits is present in notable quantities, it may be detected 

 by the amount of residue on polymerization in conjunction with 

 lowered initial boiling point and the deep coloration produced by 

 mixing portions of the original turpentine or the first fraction with 

 sulphurous acid and with hydrochloric acid. 



If the initial distilling temperature of the turpentine is less than 

 154 C. and the original sample gives a reddish color with sulphurous 

 acid and a greenish red with hydrochloric acid, and the residue from 

 polymerization is less than 5 per cent, 1 it is probable that the sample 

 is adulterated with rosin spirits. An odor of rosin spirits in the 

 sample, or in any fraction, would be confirmatory, and all tests 

 should be repeated on the first fraction, obtained with a fractionating 

 column. At best the detection of small amounts of rosin spirits is 

 very difficult, and the procedure outlined may often fail to detect its 

 presence. 



COAL-TAR OILS. 



The presence of marked quantities of coal-tar oils, benzol, toluol, 

 and xylol is detected by the odor, the lower initial distilling tem- 

 perature, i. e., between 80 and 155 C. (176 and 311 F.), and by 

 further examination of the first fractions which distill below 155 C. 

 (3 1 1 F.) . The rise of temperature on shaking during polymerization 

 is also indicative of the nature of the sample. Coal-tar and petroleum 

 oils do not raise the temperature more than 35 or 40 C. (95 or 

 104 F.), when mixed with sulphuric acid. When the temperature 

 of turpentine mixed with 38 normal sulphuric acid does not rise 

 above 50 or 60 C. (122 or 140 F.), it is evident that mineral oil, 

 coal-tar oil, or some other oil than turpentine is present in large 

 quantities. The older the sample of turpentine, the greater, or at 

 least the more rapid, the rise of the temperature of the mixture. 

 When the initial distilling temperature of the sample is less than. 

 154 C. (309 F.) and there is less than 1 per cent of residue on 

 polymerization, the presence of coal-tar oils is to be suspected. The 

 sample should be carefully fractionated with a column, the initial 

 distilling temperature noted, and that portion distilling below 157 C. 

 (315 F.) carefully examined. A refractive index at 20 C. greater 

 than 1.475 is strongly indicative of coal-tar oils and the test should be 

 repeated, distilling a sufficient quantity of the sample to obtain at 

 least 50 cc fractionating below 157 C. (314 F.), which should be 



1 Rosin spirits leaves a small residue on polymerization. 



