XXI. The magnetic susceptibilities of copper, silver and gold and errors in the Gouy method

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Abstract
A direct determination has been made of the absolute magnetic mass susceptibility of copper, silver and gold. The values at 23°c are: Copper, −0·08599±0·00027 × 10−6; silver, −0·18128±0·00054 × 10−6; gold, −0·14216±0·00048 × 10−6 c.g.s. e.m.u. per gram. The probable errors of the relative values are 0·09%, 0·07% and 0·16% respectively. The correction for ferromagnetic impurities is discussed. From an experimentally determined magnetization curve of the ferrromagnetic impurities in a silver specimen, it is shown that, although the error inherent in the long specimen method is greatly reduced by using a short specimen, an error may remain even when the smallest field acting on any part of the specimen is 6000 gauss. The method of calibrating the field by means of a current-carrying loop and of making allowance for the variation of the field strength in the plane normal to the axis of the specimen are described in detail. A pole piece design which is particularly suitable for the short specimen method is given.