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mum values of M o (eq 29 ) assuming minimum and maximum values for both R m ax and~. The range of ,~ may be taken as 0.7 to 0.9. Compu te the corl'esponding valu es for J.I. M o and mark out the vertical band corresponding to these limits in figure 1. 5. For the m aximum and minimum limits assumed for both L and ~, compute the corresponding limits for L o (eq 28 ). Compute the corresponding values ·of QLo/t:.p and mark out the horizontal band C01'-l'esponding to these limits in figure 1. Steps (4) and (5) result in a design rectangle on figure 1 within which a solution is possihle.6. Further limit this design r ectangle by excluding regions of figure 1 representing greater and lesser area A (really J.l.A ) than desired.7. For gas flow, compute the maximum tolerable value of the coefficient of the Knudsen term band the corresponding minimum val ue of fib er diameter d. Exclude regions of figure 1 r epresenting smaller values of d (really d! p,). One may then choose design parameters corresponding to any point in the design region that has not been excluded.8. When the flowm eter is built and tested, adjustment of the resistivity can then be made by the principal techniqueiof changing the weight of glass wool used. Journal of Research of the Nationa l Bureau of StandardsFinancial support for this investigation was provided by the Office of Naval Research under a project on Basic Instrumentation of Scientific R esearch. Grateful acknowledgement is also due W . A. Wildhack, at ~vhose suggestion and under whose sup ervision the development of the glass wool flowm eter was carri ed on. D e nsity (at 20°, 25°, and 30° C), refractive index (at se ven wav elengths at 20°, 25°, and 30° C), vapor pressure, and boiling point (from 48 to 778 mm Hg) of 16 h~ghly purifi ed samp les of hydrocarbons of the API-N BS series wer e m easured for 8 monoolefin (l-a lkene), 6 pe ntadiene, and 2 cyclomonoolefin hydrocarbons.The data on r efractive index were adju sted by m eans of modified Cau ch y and Hartmann equations, and values of t he constants are given for each compound.The data on vapor press ure were adjusted by mea ns of the method of lea st squares and the three-constant Antoine equation. The values of th e constants are given for each compound .Values were calcula ted for the specfic dispersions,As a cooperative investigation of the National Bureau ' of Standards, the U. S. Office of Rubber R eserve, and the American Petroleum Institute R esearch Proj ect 6, measurem ents of density, refractive index, vapor pressure, and boiling point wer e made on highly purified samples of eight monoolefin (I-alkene), six pentadiene, and two cyclomonoolefin hydrocarbons of the API-N BS series.The compounds m easured were mad e available

For the isomeric hexenes, highly purified hydrocarbons of the API Research series, the following properties were measured : densities a t 20,25 and 30"; refractive indices a t seven wave lengths at 20,25 and 30" and boiling points and vapor pressures a t 80 to 780 mm. The data on refractive indices were correlated by means of modified Cauchy and Hartmann equations, and values of the constants are given for each compound, to ermit precise evaluation of the refractive index as a function of wave length. The data on vapor pressures were correlateiwith the Antoine equation and values of the three constants are given for each compound. Also included are calculated values of the specific dispersions, (ns -nc)/d and (no -nD)/d, and of heats of vaporization a t 25' and the normal boiling point.

Data for the density and refractive index of mixtures of acetone and water are presented. Deviations from ideality for such data are clearly shown if data are correlated with ideal volume per cent composition. If there is no deviation from ideality, density and refractive index may be exactly calculated from the ideal volume per cent composition. With deviation from ideality, a plot of refractive index vs. density in which the actual points are connected with the ideal points is very revealing. The slope of these tie lines may be related to the slopes corresponding to various specific refraction equations In the case of the acetone-water blends, the simple Gladstone and Dale relation accurately represents the change of refractive index in relation to the change of density owing to the contraction on mixing. The possible effect of hydrogen bonding on the relation between refractive index and density for binary aqueous mixtures is pointed out, The presence of hydrogen bonding, or absence of it, may determine which specific refraction function best represents the data for a particular aqueous binary mixture.THE study of data for binary mixtures of liquids, and of simple solutions of solids in liquids, is important for developing a better understanding of the liquid state (5, 6, 20, 2 2 , 2 3 ) . T h e properties of binary mixtures of liquids, particularly aqueous solutions, cannot be predicted with certainty from the properties of the pure materials but must be quantitatively evaluated from experimental d a t a (5, 6. 20, 22, 23). This paper contributes d a t a on binary mixtures of acetone and water and discusses briefly the application of refraction functions to the generalization of such data. D a t a on binary mixtures of acetone and water were obtained some time ago for analytical use. These data have been checked recently in a second laboratory. These two sets of data are presented in Tables I and 11. T h e composition d a t a are recorded both a s ideal volume "C and weight "c. Deceased.Mole per cent composition is used in many discussioris of binary mixtures (19. 21. 22, 28), b u t consideration from the volume c70 point of view still has some advantages. T h e space separating molecules is, of course, closely related to volume clc composition, Table 111 compares three sets of data a t 50.26 ideal volume 5 water. T h e agreement among the three sets of data is satisfactory. Table IV compares the experimental density and refractive index data for the acetone and water used in this work with literature data. A s the agreement is good, one may conclude that the materials used were of adequate purity. Ideal volume % is the volume cc calculated from the weight 5 assuming no volume change on mixing. By definition, density must plot linearly against ideal volume CC if there is no volume change on mixing (13, 19. 23. 2 5~, therefore the deviation from linearity when density 1s plotted against ideal volume CC is a direct measure of deviation from 330 JOURNAL OF CHEMICAL AND ENGINEERING DATA

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