756
ANALYTICAL CHEMISTRY
a 250-nil. Pyiex iodiiie-titration flask with about 20 to 30 ml. of s a t e r . After the addition of 5 ml. of a 20% sodium dihydrogen phosphate solution, 5 ml. of Chlorox commercial bleaching solution nere added and the solution was heated just to boiling. The addition of 5 ml. of a 50% sodium formate solution to this should be accompanied by vigorous effervescence. After cooling to room temperature, 10 ml. of 9 h’sulfuric acid, 1 drop of 0.5 N ammonium molybdate, and approximately 1 gram of potassium iodide were added, and the liberated iodine was titrated within 1to 2 minutes. The calculations are as follows:
79.97 (ml. of 0.01 S thiosulfate - blank correction) X 7
yo Br
u
=
weight of sample in mg.
iCKNOWLEDGRIE3T
The authors are indebted to Oskar P. \Viiitrrsteiiier or hi* interest and advice in this work. LITERATURE CITED
(1) Alicirio, J. F., AKAL.CHEY.,20, 85 (1948). ( 2 ) Elek, d.,and Harte, R. -I.,IxD. ENO. CHEN., ASAL. ED., 9, 502 (1937). (3) Kolthoff, I. M., and Tutzy, H.,Ibid., 9 , i 5 (1937). (4) Meulen, J. H., van der, Chem. Weekblad, 28, 238 (1931); 31,5.55
(1934).
The data in Table I show that satisfactory agreement with the calculated values was obtained with a wide variety of bromine compounds. Although no improvement in accuracy and precision over existing methods is noted, there is an advantage in time consumed for analysis. The average analysis requires only 1 hour. The convenient and usually preferred iodometric titration procedure might also be cited as an advantage.
( 5 ) Niederl, J . B., and Niederl, \‘., “Organic Quantitative Mier+ analysis,” 2nd ed., pp. 160 5, New York, John Wiley 81 Sons,
1942. (6) Sundberg, 0. E., and Royer. G . L., ISD. Eso. CHEW,da.4~. ED., 18, i 1 9 (1946). (7) Willard, H. H., and He>-n.Arno H. A , , Ihid.. 15, 331 (1943). HLCEIVKL,
.iugost 6, 1948.
Electrolysis with a New Type of Mercury Cathode Cell JOSEPH RYNASIEWCZ Knolls Atomic Power Laboratory, General Electric Co., Schenectady, .V. Y .
HE removal of various cations by electrolysis with a mercury Tenthode has been discussed ( 1 , 2 ) . I n such a procedure, the cation is deposited in the mercury cathode, usually from a dilute sulfuric acid solution. The amalgam is then separated from the electrolyte without inteirupting the flow of current, lest the cation be returned to solution. hIelaven ( 3 ) reviewed the operation of various mercury cathode cells and concluded that their disadvantage 1% as in the amalgam-electrolyte separation. Using a mercuryleveling bulb attachment to this cell, he was able to effect a clean and easy separation of the mercury and the electrolyte.
*
PLATINUM ANODE
The cell consists of vessel d with a rounded base attached to a special capillary stopcock, B, which permits continuous current flow (except for a fraction of a second) during electrolysis arid while the mercury is being drawn off. The stopcock was made from a three-way, solid stopper (plug) capillary stopcock. A tungsten wire (platinum may h e used), \vas sealed into the longitudinal bore of plug B I which was drilled out to the transverse opening, B?. A copper cable was ITelded to the tungsten wire t,o permit free rotation of the plug J-ihen the negative element was connect,ed to the cathode of storage battery. Operation. While the plug is in position B,, nierrury is added to the cell uritil the level is about 2 cm. from the bottom. The solution to be electrolyzed is introduced and a platinum anode is immersed in the electrolyte. The electrodes are counected t o a 6volt storage battery and the solution is elect,rolyzed with a current of about 2 amperes (0.24 ampere per sq. em.). The mercury and solution are st,irred with an electric stirrer, and the cell is cooled with a stream of air (a water-cooled jacket also may be used). After 3 spot test is made for complet,e removal of the cation, the s t o p c x k is rotated through 90” and the mercury is drawn off. Frejh mercury is added to the cell and removed as before, thus washing out any amalgam that may have adhered to the stem. A platinum wire may be used to dislodge the mercury left in the capillary. The cell is drained of the electrolyte and readily washed. \Then a solution containing 0.100 gram of iron was electrolyzed for 50 minutes using the cell, all the iron was removed from the electrolyte as indicated by the a,a-bipyridyl colorimetric test. .Ilt,hough this cell was used for micro and semimicro separations, it may be adapted to macrotechniques by increasing the capacity of the vessel and the diameter of t,he capillary stopcock.
TUNGSTEN
!
ACKIVOW LEDGMENT
The author is indebted to L. P. Pepkowitx for his consultation in this work, and to I. C. Peabody for his technical advice and assistance in making the cell. mm. CAPILLARY
Figure 1. Mercury Cathode Cell
The cell illustrated in Figure 1 was designed for electrolytic removal of iron and other heavy metals. It facilitates the amalgam-electrolyte separation without resorting to a mercury-leveling bulb attachment.
LITERATURE CITED
(1) Hillebrand, TV. F., and Lundell, G. E. F.,“Applied lnoiganic Analysis,” pp. 105-6, New York, John Wiley &Sons, 1929. (2) Lundell, G. E. F., and Hoffman, J. I., “Outlines of Methods of Chemical Analysis," pp. 94-6, Xev York, John Wiley & Sons, 1938. ( 3 ) Melaven, A. D., IWD.ENG.CHEY.,AI^%^. ED.,2, 180 (1930). RECEIVED September 21, 1948. T h e work reported here was rarriediout under contract No. W-31-109eng42.
