AN IMPROVEMENT IN THE VICTOR-MEYER METHOD A. R. RONZIO AND K. A. GAGOS, UNIVERSINOF COLORADO. BOULDER, COLORADO The classic method of performing the Victor-Meyer experiment for vapor-density and molecular-weight determinations is subject to several sources of error. The small glass-stoppered bottles which contain the liquid to be determined will almost invariably allow a small amount of liquid to evaporate during weighing. When the bottle is allowed to drop to the heated portion of the inner tube, the stopper is not always forced out by the pressure generated within the bottle even though it has been loosened previously to inserting in the upper part of the inner tube. If the bottom of the inner tube has not been cushioned from the shock of the dropping bottle, the inner tube is sometimes broken. If mercury or a mat of asbestos has been used to absorb the shock of the falling bottle, difficulty in cleaning the inner tube after each run is encountered. The method outlined below has the following advantages. No failure will ever be encountered due to the inability of the liquid to be evaporated. The weight of the liquid to he determined can be obtained to a high degree of accuracy. There is no danger of the inner tube breaking due to the fall of a heaw container. therefore doing away with any asbestos mat or mercury layer. Small glass bulbs are blown from 6-mm. tub'mg as shown in Figure 1. Heating of the glass tubing by a pointed flame should be done a t the point that the m o w indicates and in the direction of the arrow. The bulbs are weighed as accurately as is desired, then filled by the following method with the liquid to be determined. The body of the bulb is first warmed in a luminous flame, then the tip of the capillary tube is submerged in the liquid. As the bulb cools, a small drop of liquid is drawn into the bulb. The bulh is then again heated until the contents boil, whereupon the tip is again immersed in the liquid. The condensing of the vapor in the bulh will fill it with liquid. The end of the capillary tube is then sealed and the entire bulb is again weighed. The bulb is then suspended from a breaker attachment (see Figures 2 and 3). This attachment acts as a holder for the bulh and its contents, and as a breaker for the capillary 1827
1828
JOURNAL OF CHEMICAL EDUCATION
OCTOBER,1932
tube in order to release the bulb and allow it to fall to the heated portion of the inner tube. The plunger should he so adjusted that it will not bear down on the capillary tube sufficiently to break it and yet enough so that there is no danger of the bulb falling out. The complete assembly is then affixed to the top of the inner jacket and the experiment performed in the usualmanner. The capillary tube is broken and the bulb released by pressing on the plunger. Q
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a-a brass sleeve soldered to the plunger f . b--a short length of rubber tubing, preferably wired on. c-a rubber stoooer. d-a brass tube in which the ~ l u n e e rf slides, -a slat in the'tube d which acts as a guide for the bluuier: f-the plunger. g-the capillary tube of the bulb containing the liquid to be determined. h-the upper end of the inner tube of a Victor-Meyer apparatus.
It is recommended that Hempel burets be used to measure the gas displaced. As a precaution against possible leakage the reservoir buret should be lowered as the air is being displaced, lowering a t such a rate that the two menisci are always a t the same level. The small glass bulbs should preferably not exceed 7 mm. in diameter.
