Copper and Iron Samples for Analytical Chemistry Copper and iron samples are required in large numbers for quantitative analysis courses. In our laboratory we have found copper wire and steel raear blades to be convenient substitutes for the traditional materiah. A thin, high purity, copper wire may be employed as a primary standard. Once the purity 28, 299 of the wire is determined, uniform lengths of the wire may be cut [see THIS JOURNAL, (1951)l for student determinations without further weighing. Best results have been obtained with 10 mil wire. Thicker wire is difficult to cut uniformly. A steel razor blade may be used as a satisfactory sample for iron determination. Because hydrogen gas is given o t i during dissolution of the blade, the iron is maintained in the iron(I1) state. This simplifies the analysis by eliminating the usual reduction procedure using SnCln, which in turn requires HgCh for removal of the excess reagent. The average weight of a razor blade was found to be 0.7 g. When it is dissolved and diluted to the mark in a 250-ml flask, each 50-ml aliquot contains approximately 2.5 milliequivalents of iron. This represents the usual amount required for a titration. Average percentage of iron determined by a class of 25 students was 97.94% with 8. standard deviation of 0.42y0. Samples of iron ore previously used had a standard deviation of 0.53%.
SAMUELY. SEEN UNIVERSITY LONGISLAND B ~ o o k l w NEW , YORE
264 / Journal of Chemicol Education
