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15 cc. concentrated, and with 7 cc. fuming, acid sufficed to prevent the 

 residue of pure oils from exceeding 3°/o. The time required for the treat- 

 ment was found to be 6 hours for the first and from 40 to 45 minutes 

 for the second manipulation. The method was carried out in a specially- 

 constructed burette; the samples examined consisted of a large number 

 of crude and rectified turpentine oils and pine-tar oils of various origin, 

 age, and degree of purity as well as of a few distillates of petroleum and 

 benzene. Of these samples the commercial turpentine oils (and pine-tar 

 oils), when treated with the quantities of acid mentioned above all gave 

 a residue of less than 3°/o; when those fractions of the various oils which 

 distilled over at 153 to 180° were submitted to the same treatment, the 

 maximum residue was only 2,1 °/o. Two detailed tables are given showing 

 the refractive indices of the oils themselves, of their fraction boiling 

 between 153 and 180° and, in some cases, of the residue also. The 

 tables also indicate the percentage of residue in each instance. The pe- 

 troleum distillates, Sc were subjected to the same treatment, and 

 here residues of 61,5 to 90°/o, all showing a greatly decreased index of 

 refraction, were obtained. Adulterated oils of turpentine, diluted with 

 benzenes or petroleum in quantities rising successively by 5%, and like- 

 wise treated with 15 cc. concentrated, and afterwards with 7 cc. fuming 

 acid, gave values which showed that the action of the same quantity of 

 acid upon a proportion of turpentine oil varying naturally according to 

 the degree of adulteration, resulted in different reaction-temperatures and 

 in different degrees of action upon the benzene and, consequently, upon the 

 residue. It was found that in the case of minor adulterations (5 to 10%) 

 the correct value was only obtained by the treatment with fuming acid, 

 while in the case of oils mixed with from 65 to 70°/o petroleum distillate 

 treatment with concentrated acid was sufficient, and the subsequent 

 shaking with fuming acid left behind a smaller percentage of residue 

 than corresponded with the original adulteration. In accordance with this 

 fact the quantity of fuming acid applied in the case of adulterations bet- 

 ween 5 and 70°/o was made to vary from 7 to cc, but as the quanti- 

 ties then ascertained gave somewhat deviating values in the neigh- 

 bourhood of 10 and of 55°/o adulterant, it was necessary to carry out a 

 correction (the extent of which is shown in a special table) of the quantities 

 of fuming acid which must be used according to the degree of adulteration. 

 When this voluminous preliminary work had been done, a large number 

 of samples of different turpentine oils and pine-tar oils were mixed with 

 different kinds of benzene and petroleum in an increasing ratio and exam- 

 ined in the light of the results above-mentioned; deviations not exceeding 

 1 °/o being detected. The indices of refraction of almost all the oils which 

 had been thus adulterated and of their residues were determined. In 

 contradistinction to Valenta, Eibner and Hue found that the difference 

 in the refraction of turpentine oil and pine-tar oil was not sufficient 



