Ch. 2: Platinum in 1915

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	150 MINERAL RESOURCES, 1915—PART I.

	containing no heated metal parts. * * * The loss of weight due to heating per 100 centimeters of practically iron-free crucible surface at 1,200° C. ranged from 0.71 Mg. to 2.69 Mg. per hour, the lesser losses being for crucibles containing rhodium and the greater losses being associated with iridium. * * * Iron appears to lessen somewhat the loss of weight on heating, but its presence is objectionable on account of the soluble oxide formed on the crucible surface. * * * It appears to be possible, from a thermoelectric and microscopic examination of a crucible, to predict its probable loss of weight on heating within limits close enough for analytical purposes. * * * Suggestions are offered concerning the specifications of highest grade platinum crucibles, including the substitution of rhodium to 5 per cent for iridium, and the practical elimination of iron. Much attention has been given to the perfection of substitutes for platinum for use in chemical work. Although several alloys are employed for certain purposes in which platinum was formerly used, it does not appear that any successful substitute has been found for platinum for the dishes and crucibles used in analytical work. These dishes must of necessity be such that they are not affected by the reagents used. Eecent. experiments conducted by Prof. Parr ¹ have resulted in the development of an alloy which is resistant to nitric acid. The alloy was conceived on the idea of combining elements of positive and negative electric properties in such a manner that the alloy would have a zero electric potential. The analysis ² of one of the alloys made during these experiments, which satisfied the conditions required, is given below.



	As stated in the report for 1914,³ a considerable quantity of platinum is used by the makers of sulphuric acid in what is known as the contact process. How great a quantity is so utilized has probably not heretofore been generally realized. Through the courtesy of most of the makers of sulphuric acid by the contact process, an estimate can be given for the quantity of platinum used in the industry; but as a few of the operators have not supplied figures, the quantity stated approximately is known to be less than that actually used. From the best information available at present it would seem that approximately 43,888 ounces of platinum are contained in about 1,487,000 pounds of contact mass used in the various sulphuric-acid plants of the United States, which use the contact process. The losses reported by these companies range from a negligible minimum to a maximum of 0.25 grams per ton of acid. Under the best practice it is believed that there should bo little or no loss of platinum, for even though the mass may become "sickened," because of impurities in the gases that enter the contact chamber, it is possible to rejuvenate the mass with almost no loss.

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