Glycerol Viscosity Tables 1 1 . 4~1~0~ L. SHEELY, Armour Soap Works, Chicago, Ill.OTWITHSTAKDING some statements in the literature to the effect that glycerol and its aqueous solutions N are not entirely suitable liquids for use as viscosity standards in calibrating technical viscometers, these solutions have come into common use for this purpose. The principal objection offered against them lies in the fact that solutions above approximately 85 per cent glycerol are hygroscopic, whereas those below this concentration give up water when evposed to average humidity conditions. Evperience has shown that these properties do not offer serious difficulties if the facts are recognized and precautions taken to obviate changes in concentration on these accounts.The principal points in favor of their use for calibrating purpose are the ready availability in pure form, wide range of viscosities, and ease of standardization as to glycerol content; c. P. glycerol of exceptionally high purity is available on the present market in concentrations from 95 to 99 per cent. The difference represents largely water, there being usually less than 0.01 per cent foreign impurities present in the c. P. grade.Consequently, the range of viscosities obtainable upon the more highly concentrated grade and its aqueous solutions is from 12.00 to 0.01 poises. By means of an accurate specific gravity determination the percentage glycerol concentration can be determined within *0.02 per cent. With this information a t hand, a table showing the absolute viscosities of varying concentrations would complete the information necessary for the purpose.The literature contains several references to the viscosity of glycerol; the data of Archbutt and Deeley (1) and of Herz and Wegner (8) are perhaps the most widely quoted and used. The former authors worked with an instrument of their own design and determined absolute values for viscosities a t 20" C.for eight concentrations of glycerol from approximately 40 to 97 per cent. These, together with their value for water, were used in constructing a table of viscosities corresponding to specific gravities from 1.000 to 1.260 a t 20"/20° C.While the data of these authors no doubt represent the best a t present available, they are of questionable value for accurate calibrating purposes, principally because of the fact that only eight points of the viscosity curve were determined, thus necessitating interpolation between widely separated points. Moreover, the purity of the original glycerol which was purchased in 1896 would be open to question, since methods of glycerol manufacture a t that time were quite crude when compared with present-day equipment and processes.The purpose of this paper was to determine accurately the concentration-viscosity curve of solutions of commercial c. P. glycerol of highest purity over a limited room-temperature range-namely, 20" to 30" C.-and to show a comparison with the published values. A secondary purpose of the investigation was to determine sufficient data in the higher conce...

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