708
KAROL J. MYSELS
and Guntelberg. Severtheless, the deviation from linearity indicated by these A-values is very large and beyond the experimental error. It may be pointed out that Harned and Harris (2) found a maximum deviation from linearity of 1.95 mv. for sodium hydroxide-sodium chloride mixtures at a total molarity of 5 ill. The deviations found for zinc chloride-calcium chloride mixtures are much larger and, me suggest, can be accounted for by the formation of complex ions, such as ZnCIT-, in these solutions. We have also made a few measurements of the density and conductance of equimolar mixtures of these salts a t 25”C., as shown in table 4. Concentrations in the first column have been expressed as moles of either salt per liter, but the equivalent conductances have been evaluated with a concentration unit based on (0.5 CaCll 0.5 ZnC12). I graphical comparison of these equivalent conductances (figure 1) with those of the single salts suggests that zinc chloride and calcium zinc chloride belong to the same family, while the behavior of calcium chloride is different. This would be consistent with the formulation Zn(ZnC14)and Ca(ZnClr) for zinc chloride and the mixed salt, respectively.
+
REFEREKCES
(1) CARMODY, W. R . : J. Am. Chem. SOC.61, 2901 (1929). (2) HARNED, H.S., AID HARRIS,J. M . : J. Am. Chem. SOC. 60, 2633 (1928). H.s.,. ~ N DOWES, B. B.: The Physical Chemistry of Electrolytic Solutions, (3) HARNED, Chap. 14. Reinhold Publishing Corporation, Xew York (1943). J. E.:J . .&In. Chem. SOC.64, 4.180 (1932). (4) HAWKINS, (5) h f E A D , D . J., A I D F r o s s , R. 31.:J. Phys. Chem. 49,490 (1945). (6) ROBISSOS,R..4.,A K D STOKES, R. H . : Trans. Faraday Soc. 36, 740 (1940).
CONDUCTIVITY OF SOME SALTS I S MOIST ACETOKE‘ KAROL J . XYSELS2
Department of Chemistry, Stanford Cniuersitu, California Received December 3,1946
In 1932 Lannung (1) studied the solubility of certain salts in acetone by measuring the conductivity of saturated solutions, both “anhydrous” and containing small amounts of water. He found varying conductivities and varying susceptibilities to water. A r&xamination of Lannung’s data suggests a somewhat different interpretation and also a simple method for determining moisture in acetone. 1 Study conducted under contract OEMsr-1057 between Stanford Cniversity and the Office of Emergency Management, recommended by Division 11.3 of the Sational Defense Research Committee, and supervised by Professor J. W. McBain. * Present address: Department of Chemistry, Sew York University, University Heights, K e a York 53, New York.
CONDUCTIVITY OF SALTS IN MOIST ACETONE
709
The salts studied by him fall into two classes. Saturated solutions of cesium iodide and sodium bromide have a high conductivity in “anhydrous” acetone which is relatively little affected by added moisture. All others have relatively low conductivities strongly affected by traces of moisture as shown in figure 1,
-A !
--A
MOISTURE FIG.1. Conductivity of some salts in moist acetone
on which Lannung’s data are replotted. The conductivities of these latter solutions increase linearly with moisture content, as has been pointed out by Lannung, but furthermore they all extrapolate to zero conductivity a t a moisture content of 0.2-0.3 per cent less than Lannung’s “anhydrous” acetone. This coincidence suggests strongly that the conductivity of saturated solutions of these salts is actually close to zero in really anhydrous acetone and that Lannung’s anhydrous acetone contained 0.2-0.3 per cent of moisture. In view of
710
K. J. PALMER, R. C. MERRILL, H. S. OWENS, AND M. BALLANTYNE
the difficulty of drying acetone (2) and Lsnnung’s method of drying (distillation from potassium carbonate and protection by calcium chloride), it would be surprising if a much higher degree of dryness n-ere obtained. Lannung’s own criterion of dryness-conductivity of saturated sodium chloride solution-suggests a variation of 0.05 per cent moisture in the acetone used. If this view is correct, the conductivity of saturated solutions of a salt such as cesium fluoride would be a simple and sensitive method of determining traces of moisture in acetone and their conductivity in anhydrous acetone would be of a smaller order of magnitude than reported by Lannung. REFERESCES
(1) LANNUNG, A.: Z. physik. Chem. 161, 255, 269 (1932). (2) TIMMERMANS, J., A N D GILLO,L . : Roczniki Chem. 18, 812 (1938).
AN X-RAY DIFFRACTIO?: INVESTIGATIOS OF PECTINIC AND PECTIC ACIDS K. J. PALMER, R. C. MERRILL, H. S. OWENS, AND M. BALLANTYNE Weelern Regional Research Laboratory,’ Albany, Californaa Received January 8, 1947
It has been recognized for some time (10) that pectinic acid is composed of an essentially linear polygalacturonide chain of length sufficient for the production of fibers. However, the only published x-ray data on fibers of this important natural high polymer are those of Wuhrmann and Pilnik (19). In 1933 Van Iterson and Corbeau (18) obtained optically negative, uniaxial. birefringent fibers by spinning concentrated aqueous solutions of commercia. citrus pectin into an alcohol-ether mixture. These authors claimed that x-ray photographs of these fibers showed the presence of oriented crystallites. Henglein and Schneider (7) have since reported that x-ray photographs of nitropectin fibers show weak crystallite orientation. Kringstad and Lunde (9) have published a power photograph of a pectinic acid, but they gave neither the values of the spacings nor data from which they could be calculated. Astbury and Bell (2) have reported results obtained by K. L. Scott on commercial lemon pectin. Only Wuhrmann and Pilnik (19) have attempted to deduce any structural information from their x-ray photographs. These authors suggest, on the basis of the x-ray patterns obtained from oriented films and fibers of pectinic and pectic acids, that the fiber identity period is about 8.8 A. In the present paper it will be shown that this value is too small, the fiber identity period actually being about 13 A. This value of 13 A. is similar to that found to occur in sodium pectate (14, 15). tion
Bureau of Agricultural and Industrial Chemistry, Agricultural Research AdministrsU. S. Department of Agriculture.
