AUGUST. 1950
463
EQUIVALENT WEIGHT BY REDUCTION OF COPPER OXIDE-A FIED PROCEDURE DANIEL B. MURPHY University of Scranton, Scranton,Pennsylvania
MODI-
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EVERYchemistry teacher is familiar with the experi- laboratory manual for the determination of equivalent ment in which the equivalent weight is determined by weight. The apparatus is constructed as in the illustration, reducing a known weight of copper oxide with hydrogen, and, from the loss in weight, corresponding to the oxy- using 1.5 to 2.0 g. of cupric oxide in a porcelain boat in gen removed, calculating the weight of copper which the one test tube and a mixture of 5 g. of ammonium would combine with 8 g. of oxygen. I n many institu- chloride and 4 g. of powdered calcium oxide in the other, tions, however, this experiment, despite its value both as with a drying tube between. The time necessary for a quantitative exercise and as a demonstration of reduc- complete reduction to be effected is about 15 minutes tion by hydrogen, is undertaken with misgivings, or and in an average freshman class, the per cent error avoided altogether because of the hazards present when ranged from 0.19 to 6.8 per cent with an average error of 3.1 per cent. hydrogen is heated by an inexperienced student. Here a t the University of Scranton, we have carried out this determination using ammonia instead of hydrogen as the reducing agent. In this way all dangers inherent in the handling of hydrogen are eliminated, and the experiment may be safely performed by the most inexperienced student. To our knowledge, this procedure has never been included in a general chemistry
