Recovery of Iodine from Metallic Iodides by Oxidation with Technical Nitric Acid RUSH Fox MCCLEARYAND ED. F. DEGERING,Chemical Laboratory, Purdue University, Lafayette, Ind.
IN
THE preparation of zinc ethyl in this laboratory, it seemed advisable to devise a simple procedure for the recovery of iodine from the zinc iodide residues. The various methods for iodine recovery suggested by Torossian (6),
E
a zinc iodide cake. The procedure proposed by Lachman (3) involves the hazard of breaking the flask while crushing the hard cake of zinc iodide and unreacted zinc, and the procedure is a little involved. The apparatus shown in the figure eliminates this hazard, and also has the advantage of a simple procedure which gives a good initial yield of crude iodine. Flask A contains the hard residue from the zinc ethyl distillation. B is an ordinary bell jar fitted with a ground-glass lid, and is surrounded by an ice bath. The system may be kept slightly evacuated through the water trap E by partially closing stopcock d. Crude concentrated nitric acid in slight excess of the calculated amount is introduced into flask A , in small portions, through funnel D. Stopcock d is left partly open and air is slowly and continuously drawn through the water trap E . This entrains the iodine vapors efficiently into the bell jar. lodine which collects on the walls of flask A is easily removed by heating gently with a direct flame. Flask C is kept cool by means of circulating tap water.
F
I n a recovery of zinc iodide residues which were calculated to contain 315.8 grams of iodine, 308.7 grams of crude iodine were recovered in the initial sublimation. This initial sublimate showed a purity of 90.83 per cent when titrated with standardized thiosulfate solution. By resublimation in the same apparatus, additional purification may be effected. LITERATURE CITED (1)
Arndt, F., Ber., 52B, 1131-4 (1919); Chem.-Ztg., 47, 16-17
(2) (3)
Kleinstuck, M., and Koch, A., Zellstof u. Papier, 3, 261 (1923). Lachman, A., Am. Chem. J., 24, 31-9 (1900).
(1923).
(4) Puig, I., Q u h . e ind., 2, 1-4 (1926).
(5)
Stephenson (5), Arndt ( I ) , Kleinstuck and Koch (Z), and Puig (4) are applicable to solutions or finely divided solids, and are not readily adapted to the recovery of iodine from
Stephenson, Ha F.1 A n a l ~ t t431 165-6 (1918).
Torossianl
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68 83 (1914''
RECEIVED July 21, 1933
Modified Design for Mercury Bulb of Thermostat G. B. HEISIGAND A. E. CAMERON, School of Chemistry, University of Minnesota, Minneapolis, Minn.
T
HE conventional thermostat regulator bulb is filled with
toluene, and exPan'ion of the toluene Cu'SS' change in height of a mercury column which makes or breaks the relay circuit. I n spite of the smaller thermal expansion of mercury it is preferable as liquid for a control bulb because creeping of the setting due to seepage of toluene past the mercury column is avoided. Since only the layer of mercury which is in contact with the glass of the bulb can be effective for small and comparatively rapid fluctuations in bath temperature, it is desirable that the surface of the bulb be large. Filling a large bulb with mercury entails a considerable expense and supporting the heavy and rather fragile bulb becomes inconvenient. The authors have designed and used a bulb which is mercury-filled, has a large surface, and yet uses a small amount of mercury.
tube, B, of 0.8-mm. bore was sealed to one end of the cylinder. A small bulb, C, was provided to catch any overflow of mercury from the capillary. For the adjustable contact an iron or platinum wire was inserted into this capillary. Diametrically opposite the capillary was sealed a stopcock, D. A tungsten wire Was Seded though the
~ ~ ~ ~ ~ . c :$:k T ~ ~ i ~C ~ b ' ,
Two pieces of Pyrex tubing, as thin-walled as was consistent with mechanical strength, of diameters 3.5 and 2.5 cm., respectiveiy, were placed one inside the other and sealed together at the ends to form a double-walled cylinder, a longitudinal section of which is shown at A in the accompanying sketch. A ca,pillary 420
filled with mercury and a wire dipped into it to make contact t o the mercury in the control bulb The bulb was filled by it and running clean, dry mercury in through t h e c a p i l l a r y or through the stoPcoCk, a5 was
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~~~it~o$v~~$$.in bulb could be varied by opening the stopcock and allowing mercury t o run into the bulb from the tube above the stopcock or by sucking mercury out o f , t he bulb into this
reservoir.
