1194
ANALYTICAL CHEMISTRY
bearings fit into bearing cylinders of thin tray supports, F , which suspend the tray in the rinsing tank; the basket, G, 11.75 X 5.375 X 12.25 inches, is made of perforated stainless steel with flanges to take a sliding screen, H , the top of which is provided with a handle with three notches. This basket holds about 400 15 X 125 mm. tubes; the stainless steel tank, 8 X 13 X 18 inches, contains the acid-dichromate cleaning solution.
Cell for Rapid Polarographic Analysis. Louis JIeites and Thelma ?\kites, Sterling Chemistry Laboratory, Yale I-nivereity, S e w Haven, Conn. of deaerating a solution rapidly, and the possiT bilitydifficulty of introducing cont,aminants from the agar bridge. HE
have led many polarographers t,o forego the use of H-cells (3’ in favor of less versatile cells with mercury pool anodes. Based on the cell design of I d i n e n and Burdett ( 2 ) in which the gas stream is dispersed by a fritted-glass disk, and the older design by Carritt (1‘1which eliminated the effects of contact with the agar plug, a modified H-cell which is free from these disadvani ages has been designed. Referring to Figure 1, the gas ent,ering a t a enters the solution through a sintered borosilicate glass gas dispersion cylinder, b, which brings the gas stream into intimate contact with the solution. IVhen deaeration is complete, the gas is diverted over the solutio11 in compartment c, and tube d is filled by suction a t a. Any reaction then occurring a t the agar-solution interface is isolated from the main body of the solution until the reaction prod.ucts diffuse through the entire length of d , and contamination of the solution is thereby effectively prevented. The iK correction corresponding to t,he resistance of the solution in d may gmerally be ignored, 01’ it may be detc~rminedarid applied in precise work. When contact with an agar bridge is not harmful. a more conventional design is used, in which t,he gas-entry tube of the usual €€-cell ( 3 ) is replawd by a gas-dispersion cylinder, ringsealed through the wall of the solut’ioncompartment oppwite the I)ridge, tlnd positioned as show1 in Figwe I .
Figure 1.
The tubes are placed in the basket with their mouths toward the open side. The screen is slipped into place and the basket I‘ immersed in the tank of cleaning fluid, inclined so that the tubes will fill without trapping air. After the required soaking time, the babket is lifted from the cleaning solution in an inclined posltion, snd the fluid is allowed to drain from the tubes. This operntion is most easily accomplished by means of a hook attached to i~ chain rigged from a pulley above the tank. The three notches in the handle of the basket are designed t o allow the different inclinations while the basket is being immersed or removed from the cleaning tank. The basket is now lowered into the swingirig tray. The tray bearings have been adjusted previously, so that the mouths of the tubes are downward when the tank is empty. The water is started flowing into the tank. The water level raises the float, tipping the tray and basket backward, thus allowing the tubes t o fill without trapping air. As the water level resches the siphon height, all the tubes are full. At this level the siphon starts and the tank is drained rapidly. As the water level falls, the tray tips forward so that all the tubes dlain. The siphon “breaks” and the tank starts filling again. Thls cycle will repeat itself indefinitelv. After ten or more cycles have been completed, a few millifiters of saturated sodium hydroxide are added and the tank is filled to a point just below that a t which the siphon starts, After sufficient soaking, the water inflow is resumed for the desired time. Distilled water may be poured into the tank for the final rinses. The basket is removed from the tank, drained, and placed in a drying oven with the mouths of the tubes downward.
I n practice it is efficient t o have two or more baskets; a second basket may be filled with tubes while the first is being washed. T h e dimensions noted are those necessary for the cleaning of 15 X 125 mm. test tubes. If tubes of other sizes are employed, the dimensions of the apparatus should be adjusted accordingly.
Figure 1. Modified H-Cell a. Gas-entry tube, 4 - m m . outside diameter
b. Corning 39533 12C gas dispersion cylinder Solution compartment, 45 mm. outside diameter X 12 cm. d . 9 mm. outside diameter X 18 c m . total length e. Corning 39570 2031 fritted disk f. 25 m m . outside diameter X 3 c m . 4. Reference electrode compartment, 22 m m . outride dianieter X 12 c m . Length of arrow corresponds t o 10.0 c m . c.
K h e n i 5 nil. of air-saturated 3 M potassium chloride in a cell like that shown in Figure 1 were deaerated by a rapid stream of hydrogen, the diffusion currents a t -1.6 volts us. the saturated calomel electrode indicated t h a t oxygen removal was 84% coniplete in 20 seconds and 9Sw0 complete in 10 seconds: oxygen could not be detected after 1 minute. LITERATURE CITED
(1) Carritt, D. C., Ph.D. thesis, Harvard University. 1947. (2) Laitinen, H. A4., and Burdett, L. W.. AF.AL. CHEM.,22, 833 (1950). (3) Lingane, J. J., and Laitinen, H. A , ISD. END.C H E W.,~ N . < I . .ED.,
11,504 (1939). Work supported by Contract AT(30-1)-842 between the Atomic Energy Commission and Yale t-niversity.
