JOURNAL OF CHEMICAL EDUCATION
348
A MODIFICATION OF THE VICTOR MEYER MOLECULAR WEIGHT APPARATUS WARD V. EVANS and F. P. CASSARETTO Loyola University, Chicago, Ninois
F O R SEVERAL years we have had trouble with students reporting abnormally high molecular weights in their determinations in the physical chemistry laboratory. One source of error was found, on investigation, to be in the faulty introduction of sample. Some of the sample was frequently lost through the glass ground stoppers in the weighing bottles usually used for this purpose, or some air was allowed to escape when the sample was introduced. A trigger release has been devised, as shown in Figure 1, which eliminates these sources of error and has given acceptable results for student determination of molecular weights by the Victor Meyer method. A piece of #18 copper wire ( A ) 4 inches in length was soldered to a a/16-inch solid brass rod, 5 inches long (B). The brass rod passed easily througk the 8-mm. bore glass tubing (C). A piece of small diameter rubber tubing (D) was forced over the solid brass rod, resulting in a snug, air-tight fit. A piece of larger rubber tubing ( E ) was wired over the rubber tubing .(D)and the glass tubing. A book, small enough to slide readily inside the glass tubing, on the end of the copper wire carried a small sealed bulbet (F). By raising the brass rod, the tip of the bulbet was broken off and the sample fell to the bottom of the vaporization chamber. Enough resiliency in the rubber tubing connection ( E ) permits an inch to au-inch and a half of vertical movement without the introduction or escape of air. The bulbets are easily blown from small-bore glass tub'mg and samples sealed in them. Best results were obtained when samples of 0.1000 gram or less were used in the bulbets. The bottom of the vaporiza-
tion tube was protected from the impact of the falling bulbet by either glass wool or mercury. -. I Some representative student determinations, using this release, are recorded: STUDENT RESULTS Benzene (78.11)
Ethyl Alcohol (46.07)
Carbon Tetrachloride (153.84)
