Donald J. Shombert Rutgers University N e w Brunswick, New Jersey
I I
A Variation of the Victor Meyer Experiment
The determination of the molecular weight of dry ice is an interesting variation of the classical Victor Meyer experiment. As an optional determination in beginning physical chemistry it tests the student's ability to adapt a standard method to different conditions and encourages ingenuity. The procedure is run in the traditional way except for the weighing of the sample. The weight of dry ice a t the time of volatilization is determined by plotting a graph of sample weight as a function of time and extrapolating the curve to obtain the true weight. Dry ice, freshly prepared by opening a CO1 fire extinguisher into a cloth bag, is placed on a weighed piece of paper and the paper folded into a packet. Several packets are weighed on a single pan balance a t regular time intervals until an average rate of snb-
lin~ationis obtained. The estimated sample weight is then calculated for the desired COz gas volume, allol~ing for the weight loss that occurs during transfer to the apparatus. The process is repeated on another packet until the dry ice has sublimed to the approximate size desired. A final weighing is obtained and the time recorded. The sample is immediately transferred to the Victor Meyer apparatus, the stopper replaced, and the time again noted. The sample weight a t the time the system was sealed may be calculated from the graph of weight versus time. Since the sublimation rate will vary it is necessary to determine a graph for each sample. Good results have been obtained by students even though considerable manipulative skill is required.
Volume 42, Number 6, June 1965
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343
