September 15,1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
it was found that the e. m. f. of the antimony electrode in a normal potassium chloride suspension, if read off from the calibration curve, gave a figure approximately 0.4 pH unit higher than the same suspension with the hydrogen electrode. This error was fairly constant for a large number of soils, though larger variations were occasionally experienced. If this salt error were entirely due to a surface action on the electrode, it would be expected that the effect of normal potassium chloride on a buffer solution would be comparable with that on a soil suspension. It was decided to measure the variation in pH of a number of buffer solutions made up normal with respect to potassium chloride, and compare these with the pH of the buffers without potassium chloride. The results of this work are stated in the early part of this pasper. Every series of buffers shows a difference of approximately 0.4 pH unit between the aqueous and the normal potassium chloride buffer solutions. As this figure agrees closely with the salt error experienced in measuring soils, it was thought that this second curve could be utilized for giving the relation between e. m. f. and pH for the soils in normal potassium chloride suspension. The curve obtained for the buffers in normal potassium chloride was parallel to the original curve and removed from it by approximately 0.4 pH unit. The slope of the curve remains constant, the equation for potassium chloride suspensions reading E = 0.041 0.0575 pH or E - 0.041 pH =
+
0.0575
I n Figures 4 and 5 are shown the values for the hydrogen and antimony electrodes on the 43 soils plotted against each other, and also the theoretical line. Figure 4 refers to the aqueous suspensions and Figure 5 to the suspensions in normal potassium chloride. The same series of 43 soils measured previously in aqueous suspension were used for this work, and the latter columns of Table I show the results obtained. The average error as compared with the hydrogen electrode is 0.058 pH unit, which is slightly larger than the error in aqueous suspension. The average positive deviation is 0.06 pH and the average negative deviation is 0.055 pH unit. These figures are considered fairly satisfactory for agricultural advisory or soil survey work where the sampling error is likely to exceed the error of the determination. For such operations the antimony electrpde is strongly recommended. It is robust in construction and does not appear to be affected by (‘poisons” of the type which affect the hydrogen electrode. Its range of applicability is considerable and is only limited by the pH at which antimony trioxide is soluble in the system under examination. It is proved to be a fairly reliable indicator of hydrogen-ion concentration and is accurate enough for certain avenues of soil work where extreme precision is not required. It is ideally suited for field work, particularly in the form illustrated by Harrison and Vridhachalam (5).
321
(10) Kolthoff and Furman, “Potentiometric Titrations,” W h y , 1926. (11) Kolthoff, I, M., and Hartong, B. D., Rec. trav. chim., 44, 113 (1925). (12) Lava, V. G., and Hemedes, E. D., Philippine Agr., 27, 337 (1928). (13) McGeorge, W. T., Soil Sci., 27, 83 (1929). (14) Oosting, W. A. J., Mededeel. Landbou. Wageningen, 1921, 3. (15) Prideaux, E. B. R., and Ward, A. T., J. Chem. Soc., 125, 426 (1924). (16) Roberts, E. J., and Fenwiok, F. J., J. Am. Chem. SOC.,50, 2125 f 1928). (17) ShLkovand Awsejewitch, Z . Elelctrochem., 35,349 (1929). (18) Snyder, E. F., Soil Sci., 26, 107 (1928). (19) Soil Research, Soil Reaction Com., 2, 144 (1930). (20) Uhl, A., and Kestranek, W., Monatsh., 44, 29 (1923). (21) Valeur, A., Ann. chim. phys., 21, 547 (1900). (22) Veibel, S., J. Chem. SOC.,123, 2203 (1923). (23) Worsley, R. R. le G., Ministry Agr. Egupt, Bull. 83, 16 (1929). RECEIVED November 15, 1932.
A Multiple Steam Bath WARRENL. BEUSCHLEIN AND WILLIAMM. DEHN Chemistry Laboratory, University of Washington, Seattle, Wash.
I
N MOST laboratories use of hot-water funnels of the ordinary
type is attended with inconvenience, danger, and loss of materials. The depicted copper steam-tight bath has solved these difficulties. A 6-funnel type was installed in a hood and was found to be instantly available for processes of hot filtering, drying of solids, and evaporating of liquids, and a source of heat for mild or stronger digestions. The construction of the metal bath can be made extremely simple. Soldered joints are sufficiently strong for the covered container and 60” cones. Inlet steam and condensate outlets are made by attaching appropriate pipes to threaded locknuts soldered on to the bath. Where legs are desirable, short lengths of pipe can be screwed into additional locknuts STEAM I N L E T
2pI
LITERATURE CITED Best, R. J., J. Agr. Sci., 21,337 (1931). Britton, H. T., and Robinson, R. A , , J. Chem. Soc., 1931, 458. Clark, W. M., “Determination of Hydrogen Ions,” Williams & Wilkins, 1923. Franke, K. W., and Willaman, J. J., IND. EKG.CHEM.,20, 87 (1928). Harrison, W. H., and Vridhachalam, P. N., Mem. Dept. Agr. India, 10, 157 (1929). Heintze, S . G., and Crowther, E. M., Trans. 2nd. Comm. I n tern. SOC.Soil Sci.. 19298. 102. Itano, A., Ber. Ohara. Inst. iand. Forseh. Japan, 4 , 2 7 3 (1929). Ibid., 4, 19 (1929). Kolthoff, I. M., J. Biol. Chem., 63, 135 (1925).
FIGURE1
soldered on to the bottom of the container. The funnels may be centered or, if the bath is to be used also as a hot plate, they may be inserted asymmetrically. Single or double funnel baths can be used as portable laboratory equipment, depending upon the usual steam can for heat. RECEIVEDAugust 1, 1933.
