Micro H-Cell for Polarographic Analysis. Thelma LIritrs and Louis Meites, St,erling Chemistry Laboratory, Tale 1-niversity, Xew Haven, Conn. the obvious inherent utility the polarograph the I> analysis of ext,remely small amouiits of material, the literaure contains no descriptiom of a polarographic cell that may be, I~SPITE
of
in
t
wed to secure an exactly dt~finetlpotrntial axis in work with very Pinall volumes of solution in t,hr, abseuce of air. Such microcells :IS have been described either allow only the use of a mercury pool aiiode, which is unsatisfactory rvhrii the solution contains no
the ;tuthors' cell, 0.3 ml. of solution suffices to fill a from below d to above h. \Vhen less solution is used, or when d and h are more widely separated, the deaeration is carried out with the mercury level in a just below d; then mercury is added to c so that the solution is raised until it rovers the surface of the disk se arating the solution compartment from the agar bridge. In tgis way the volume of solution required for satisfactory operation can be retluced to about 0.1 ml. ACKNOU'LEDGMENT
The cell was constructed by Frank Lynsky, glassblowrr for the Xlacnalaster Bicknell Co. of Connecticut, 181 Henry St., Xew Haven, Conn. The authors are indebted to him for a number of valuable suggestions which it is a pleasure to acknowledge. This xork was supported by Contract S o . ,4T (30-11-842 between the I'. S. Atomic Energy Commission and Yale I-nivrrsity.
Simplified Apparatus for Extraction of Solids from Mixtures of Solids by Means of Selective Solvents. Joseph A. Napoli and lIorton Schmall, Physical Chemistry and Products Control 1,aboratories. Hoff niann-La Roche, Inc., Nutley, N.J. separation of solids from mixtures of solids, niany Itail lengthy extractions and transfers are required, which may enloss due spillage aa well undue loss of time, ITsing a N THE
to
as.
simple apparatus (Figure 1) with a sintered-glass plate to separate
depolarizing anion, or require eitended periods of time for coniplete deaeration of the solution. There is here described a cell which can be used for the electrolysis of as little rn 0.10 ml. of solution, which contains both a built-in saturated calomel reference electrode and a mercury pool anode which may be used a heriever the composition of the solution permits, a d in which a solution may be completely deaerated within a few minutes. The solution IS contained in a narrow tube, a , inside diameter about 3 mm., sealed a t the top t o a tube, b, inside diameter 22 nim., to allow the use of larger volumes of solution when desired and to prevent lass of solution during deaeration. The bottom of tube a is sealed t o a much larger arallel tube, c, which in use is filled with mercury to just beneat! the bottom of the deaeration tube, d. Tube c acts as a leveling bulb and eliminates the iirvessity for constant readjustment of the level of the capillaSy during use. Electrical connection can be made to the mercury 111 c when a mercury pool anode is desired. Air is removed from the solution in a by turning sto cock e so that oxygen-free hydrogen is led in through tube d. T i i s tube is . ibonnected to a through a medium-porosity sintered borosilicate glass disk about 3 mm. in diameter, which disperses the bubbles of gas and causes more efficient deaeration than would otherwise be aecured. With this arrangement the authors have found that oxygen can no longer be detected in a solution after hydrogen has heen passed through it for 4 minutes. When deaeration is complete, stopcock e is reversed so that hydrogen passes through tube f into b and prevents access of air to the solution. The electrolysis chamber, a , is also connected to a saturated calomel electrode compartment, g, by a short tube, h, which terminates in a second fritted disk. This allows filling h with a 4% xgar-saturated potassium chloride gel which serves as a salt bridge. The resistance of a typical bridge is. about 3000 ohms, aiid the potential applied to the cell can readily be corrected for the iR drop thus introduced for the exact measurement of halfwave potentials. When the mercury pool anode is used, the cell resistance is naturally much less, and can generally be ignored. The cell should be constructed so that tubes d and h are as nearly on the same level as the glasqblower's skill will allow. I n
1! .4
5
c
li
Figure 1. Apparatus
.I.
60-ml. tube with glass stopper and sintered-glass plate, utilising +topcock .4pparatus in use with a suction 5ask using ordinary rubber stopper If it is necessary to keep solv'ents free from moisture Good resul< a ca1ci;m chloride tube may be placed on to may be obtained by pressing out solvents wit{ compressed air or nitrogen instead of using suction Apparatus as designed for 40-ml. centrifuge tube. Each vessel can hold 20 ml. of liquid. Top vessel contains sintered-glass plate and ground-glass stopper. No stopcock is necessary, but a cork may be inserted to keep solvent above sinter plate. T,he bottom vessel has a lip which serves a twofold purpose; i t facdxtates transfer of solvent, and acts as an air escape during centrifuging. The two vessels are kept apart b y a rubber plate be-
.
*...^^" ....,.I+ Y n r r Y "YOlY
Apparatus in conjunction with bell jar and volumetric flask
