ANALYTICAL EDITION
A p d , 1945
N A T U R E OF THE PREClPlTATE The orange color of the precipitate obtained in this test seems to be due to the presence of free mercuric iodide. This is shown by the fact that this substance can be extracted from the precipitate by inert solvents--e.g., ethyl alcohol-leaving a yel-
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low residue. This free mercuric iodide may represent an excess of mercuric iodide dissolved in the reagent, but more probably comes from a decomposition of either the reagent or the silver precipitate. Further study of the composition and stability of the iodomercurates is planned.
Combination Gas-Delivery T u b e and Stirrer ROBERT R. RUSSELL
AND
C A L V I N A. VANDERWERF
University of Kansas, Lawrence, Kanr.
THE
stirring device illustrated represents what the authors believe t o be the best method yet described for the rapid absorption, with efficient stirring, of gases in solid or heavy liquid suspensions, a common laboratory operation required by many varied types of reactions. Adaptation of the agitator itself as the gas-delivery tube is accomplished by the use of a glass tube stirrer shaft, A-A, which terminates a t the top as the inner tube of the revolving mercury seal, C. Gss-inlet tube B is clamped SO that the lower end dips a t least 8 cm. below the surface of the mercury. Either an ordinary mercury seal, H , or a liquid seal of the type described by Fieser (2)may be used for the flask. When properly aligned in the ball-bearing mountings (I?), D and E, E , the movable assembly turns freely and smoothly. Power is transmitted to the stirrer by means of the pulley, F, from the motor, G , set to one side. A suitable belt may be made by.twisting a heavy twine around itself four times, much as a grommet splice is made. To prevent clogging, the direction of stirring should be away from the orifice. When the e n t i r e s e t u p is m o u n t e d o n one ring s t a n d i t i s easily portable and can be weighed if desired. The apparatus is inexpensive and easily assembled. A d i s carded automobile generator bearing, available a t most junk yards, makes an excellent aligning ball-bearing, D, for the revolving mercury seal, C.
Little corrosion of the mercury was observed although, if the rotating seal is made sufficiently deep, other liquids may be employed as necessity demands. Modifications in the shape or orifice of the stirrer will be found superior in many other individual cases to which this device may be adapted. LITERATURE CITED
(1) Detoeuf, A., Bull. SOC. chim.,31, 102 (1922). (2) Fieser, L. F., "Experiments in Organic Chemistry", 2nd ed., pp. 309-10, New York, D. C. Heath and Co., 1941.
Use of Infrared H e a t in Determining A n i l i n e Points
k-
The authors found this device highly satisfactory for the chlorination of suspensions of urea and chalk in small amounts of water in the largescale synthesis of chlorourea ( 1 ) . Not only was the absorption time for the usual amount of chlorine reduced to one third of that required when the gas-inlet tube was independent of the stirrer, but it was also found that the chlorine absorption could easily be forced t o a point not reached during any reasonable length of time when a stationary gas-delivery tube was employed.
H A R O L D T. HOPKINS Standard Inspection Laboratory Standard Oil Development Company, Linden, N. J.
H
EATING by infrared radiation is particularly advantageous in the widely used aniline point test. The A.S.T.M. ( I ) version prescribes the alternate heating and cooling of 20 ml. of a mixture of equal parts of aniline and the product under test, in a glass-jacketed test tube equipped with a suitable stirrer. Heat is ordinarily supplied by the use of a liquid bath or a flame. The insulating effect of the glass air-jacket is troublesome during the heating periods, as the mixture is likely to be brought to an unnecessarily high temperature, thereby wasting time while the operator watches for the appearance of a cloud in the slowly cooling liquid. The substitution of an infrared heater for a liquid bath, or a flame, reduces lag to practically zero. The thermometer reading starts to go up or down almost immediately after turning the heat on or off. If an experienced operator keeps the liquid under close observation during the heating period, the range between minimum and maximum temperature need not exceed 3" C. Rate of heating can be regulated conveniently by changing the position of the infrared bulb. Protection of the apparatus from drafts is not necessary. An operator can cdnduct two simultaneous tests with ease, and there is an increase in safety and cleanliness. A further advantage is found in the fact that the tube may be vacuum-jacketed, which ensures a slow rate of cooling and improves the accuracy of the determination. The infrared heating devices used in the writer's laboratory are infrared lamps consisting of 260-watt bulbs with reflectors. They are inexpensive and easy to obtain. The working time consumed per test performed is reduced to less than two thirds that required when employing the older methods of heating. LITERATURE CITED (1) Am. SOC.Testing Materials, Aniline Point of Petroleum Products,
A.S.T.M. Serial Designation D611-43T.
