The analysis and grading of creosotes . (Fig. 5.) The distillate was rejected up to the point where it had a specificgravity greater than that of water, and the heavy distillate was col-lected from that point until the residue in the still was either a softor hard pitch. In making fractional distillations of the various oils, 250 grams ofcreosote were distilled from a 500 c. c. distilling flask and a largenumber of separate fractions collected.[Cir. iiaj 16 INDEX OF REFRACTION. The index of refraction is the ratio between the sines of the anglesof incidence and of refraction of light, expresse
The analysis and grading of creosotes . (Fig. 5.) The distillate was rejected up to the point where it had a specificgravity greater than that of water, and the heavy distillate was col-lected from that point until the residue in the still was either a softor hard pitch. In making fractional distillations of the various oils, 250 grams ofcreosote were distilled from a 500 c. c. distilling flask and a largenumber of separate fractions collected.[Cir. iiaj 16 INDEX OF REFRACTION. The index of refraction is the ratio between the sines of the anglesof incidence and of refraction of light, expressed by the formula n sine / JD where V^ means the index of refraction referred to sodium sine,.^, D light, / equals the angle of incidence, and R the angle of index of refraction varies with the temperature, but is constantfor any given oil at a stated temperature. In making measurementsof the index of refraction of the different fractions of a creosote dis-tillation, it was necessary to make the measurements at 60°. The. /70° /SO /90 ^00 Z/0 ZZO ZdO Z40 ZSO 260 Z70 Z80 230 JOG J/0 J20° JJO JfO J-SO J60 TEMPERATURE. Fig. 6.—Distillation of creosotes 40 and 62. determinations were made with an Abbe refractometer provided witha light compensator. By means of this instrument the index of re-fraction may be read with great accuracy, and the measurement isone of the most exact which can be applied to such an oil. The distillations and the indices of refraction of two very differentoils, Nos. 40 and 62, are shown in figures 6 and 7. As shown by thedistillations. No. 40 is a rather light, low-boiling creosote, and No. 62one of the extremely heavy tar oils. [Cir. 112] 17 /.65 ^ c /57 200^ Z/O 220 230 2^0 ZSO 260 270 280° 290 SOO 3/0 TEMPERATURE Fig. 7.—Indices of refraction of creosotes 40 and 62. In figure 8 is given the range of index of refraction within whichhave fallen all the creosotes the purity of which was withoutquestion. /.66 o / / . OT^ .^
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