V O L U M E 23, N O . 5, M A Y 1 9 5 1
803 is used as the inert gas. Catalytic hydrogen-oxygen combination should take place during the shaking process, and should cause complete oxygen removal to be accomplished somewhat sooner. This procedure is not necessary for ordinary polarographic work, which requires only that the oxygen content shall be reduced to :I small value.
E’iyiire I .
Diagram of Apparatus
‘1’111~:ilip:tratus is shon.ti
oxygen froiii liioIo,~,ii~~~l wlutioii.. Figure 1.
iir
i t end and is c c t u d to rock T h e board, ‘1, is pivoted a t i through an angle of aboLit 20 ducer, which rotates a t a s:)eetl clips on the board holtl fuur g can be placed. I*>achvess ,I is :I little iiiorc~than 10 cm. in overall length, and 1 cni. i n esrt:rii&l dianieter. I t i p designed to holtl about 3 to 4 ml. of solution. l‘he openings, C, of the veswls a w connected hy rul)t)er tubing to a tank of pure hydrogen or nitrogen (only one connection is shown in the figure), aiid the vessels are flushed out with hydrogen for a feiv niiriut8eclbefore the solutions are introduced through D. T h e board shou when the solutions are introduced, and the vessil more than half filled. Openings D are then tightlj the solutions are rocked for about 1 hour. A beaker, E , filled with a salt solution with about the same vapor pressure as t)hr solutions in the vessel$, acts as a safety valve t o prevent build-up of g:is pressure. T h e gas flow during so adjustcd ,that very slow bubbling the rocking operat . The rcrlang inn? be stopped after occurs a t this safet 30 minutes and the agaiii flwhrtl o u t to remove the small amount of oxygen accumulated i n thc, atmosphere a t that time. In any event equilibrium is established after about 1 hour, and only a negligibly small fraction of the osygt’n originally present in the solution remains.
Polarograms obtained with a 1% solution of bovine serum albumin in tartrate medium before and after treatment are shown in Figure 2. For solutions containing no substances which are reducible by hydrogen, an additional refinement is possible. A platinized platinum disk, sealed into glass tubing, is wedged tightly into opening D in place of the stopper described above, and hydrogen
Figure 3. Diagram of Polarographic Cell
Because it is generally not desirable to use a large volume of solution where biological materials are involved, the familiar Htype polarographic cell developed by Lingane and Laitinen ( 2 ) , which contains an internal reference electrod?, has been modified for use with 2 to 3 ml. of solution, and to take account of the fact that oxygen need not be removed in the cell. Provision has been made for the passage of a stream of inert gas over the solution during analysis, but none for passage of gas through the solution. -1 diagram of the cell is shown in Figure 3. Deoxygenated solutions can be poured directly into these cells for immediate analysis, No appreciable reosggenation ordinarily occurs. ACKNOW LEUGMENT
The authors wish to express their appreciation to Homer Hall for designing and constructing the shaking apparatus. LITERATURE CITED
(1) Clark, W. M., “Determination of Hydrogen Ions.” 3rd ed., Baltimore, Williams & Wilkins Co., 1928. (2) Kolthoff, I. hl., and Lingane, J. J., “Polarography,” p. 212, Xew
York, Interscience Publishers, 1941. (3) Ibid., p. 411. RECEIVED August 1.1, 1950.
1 s ; /I -
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Figure 2.
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/
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Polarograms of 1% Solution of Bovine Serum Albumin Before ( u p p e r ) and after
( l o w o r ) ov-yqen removal
Converting Platinum Resistance to Temperature-Correction I n the article on “Converting Platinum Resistance to Tem~ . 22, 13336 (1960)l an error perature” [Eggenberger, - 1 5 ~CHEW, occurs in one of the formulas.
should read t , = .2
-
n 4s
+ 1011z
