The analysis and grading of creosotes . fractions which dis-tinguish most accurately the varia-tions in value between different these distillations the bulb wassupported on an asbestos board, inwhich a hole was cut almost asFIG. 16.—Hempel distilling flask. y^{^Q as the largest diameter of the bulb. The outline of this opening was not regular, but notched toallow small portions of the flame to play up around the bulb. Theportion of the distilling bulb above the asbestos board and belowthe Hemj)el column was surrounded by an asbestos box. The sourceof heat was an Erlenmeyer-Argand burne
The analysis and grading of creosotes . fractions which dis-tinguish most accurately the varia-tions in value between different these distillations the bulb wassupported on an asbestos board, inwhich a hole was cut almost asFIG. 16.—Hempel distilling flask. y^{^Q as the largest diameter of the bulb. The outline of this opening was not regular, but notched toallow small portions of the flame to play up around the bulb. Theportion of the distilling bulb above the asbestos board and belowthe Hemj)el column was surrounded by an asbestos box. The sourceof heat was an Erlenmeyer-Argand burner. With this arrange-ment a moderate amount of heat was sufficient to give an excellentdistillation through the Hempel column. The distillations were runat the rate of a drop per second. The thermometer was placed with200° the first emergent reading, and observations showed that thevalue t was almost exactly the same as with the ordinary 500 c. c. a distillation the beads and platinum plug were removed before [Cir. 112]. 31 complete cooling caused them to become too sticky. The i)latiniimplug was held in the flame until clear, and the beads were allowed tocollect in a wide-mouth bottle of alcohol until a sufficient (juantitywas collected for a wash-up. Not only do the percentage weight curves show that this newdistilling bulb is giving a much better fractionation, but tlie in- soso 7570 1 ^ ,v >^ ,{ f^ Y X ^ r f ^ >- 60 56 5t <J Q: ^^JSJO zs 20 /s /O s --^ .y //O /S0° /so ZOO Z/0° ZZO° ZJO° Z40 ZSO Z60 Z70° Z80° Z90 JOO J/O JZO TCMPEBA TU/?£Fig. 17.—Comparison between distillation with Hempel flask and redistillation with common flask. dices of refraction and the specific gravities of the fractions showa much sharper separation of the constituents of the creosote. Thesefacts are illustrated in figures 18 and 19. The shape of the range curve into which the indices of refractionof the portions of pure coal-tar creosote
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