Transactions . demonstrated by the top- and bottom-samples. These assays were repeated several times, while therest were all made singly. The samples and assays of the edge-zone are, of course, in-correct representatives of the true contents of the plate andthe furnace-charge which it represents. The correct figureshould be the average of assays I. to IX. inclusive, or , or the average of A, top, and A, bottom, Thetwo figures are very close together. The plate from which the above figures are derived was cast 118 PRECIOUS METALS AND IMPURITIES IN COPPER. in a mould with very he
Transactions . demonstrated by the top- and bottom-samples. These assays were repeated several times, while therest were all made singly. The samples and assays of the edge-zone are, of course, in-correct representatives of the true contents of the plate andthe furnace-charge which it represents. The correct figureshould be the average of assays I. to IX. inclusive, or , or the average of A, top, and A, bottom, Thetwo figures are very close together. The plate from which the above figures are derived was cast 118 PRECIOUS METALS AND IMPURITIES IN COPPER. in a mould with very heavy bottom and thin sides. The solidi-fication, therefore, took place much more rapidly from the bot-tom than from the sides and top. Fig. 10 illustrates this pro-cess, representing a vertical section through the edge and partof the plate. At z would be the highest or lowest point ofconcentration, according to the class of copper, the moleculesmeeting there from top, sides and bottom. At I would be the Fig. Vertical Section Through Edge and Part of Plate (Fig. 9). highest or lowest concentration of the layers, the moleculesmeeting from top and bottom. For practical sampling plates from 8 to 10 inches square are Fig. II. — Top i Center ^— Bottom Diagram Showing Positions of Samples in a Liquid Charge of Copper of ample size, but they should not be more than 1 inch thick, andthe drillings should be taken at least 1 inch away from theedge through the entire plate. Having seen how a correct shot-sample, or a reliable sample-plate is obtained, we may now investigate how copper in itsmolten state is constituted. The table below gives the results of tests, made for aboutthree weeks, with furnace-charges of from 90,000 to 110,000pounds of refined converter-copper. The copper having beenpoled, was, therefore, well mixed. Sample-plates were taken PRECIOUS METALS AND IMPURITIES IN COPPER. 119 in the middle of every third of the charge as it was tappedfrom the furnace, a practice
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
