218 



Mr. Graham on the Relation 



[Jan. 14, 



4. Magnetism. — It is given by Faraday as the result of all his experi- 

 ments, that palladium is "feebly but truly magnetic ;" and this element 

 he placed at the head of what are now called the paramagnetic metals. 

 But the feeble magnetism of palladium did not extend to its salts. In 

 repeating such experiments, a horseshoe electromagnet of soft iron, about 15 

 centims. (6 inches) in height, was made use of. It was capable of supporting 

 60 kilogs., when excited by four large Bunsen cells. This is an induced 

 magnet of very moderate power. The instrument was placed with its poles 

 directed upwards ; and each of these was provided with a small square 

 block of soft iron terminating laterally in a point, like a small anvil. The 

 palladium under examination was suspended between these points in a 

 stirrup of paper attached to three fibres of cocoon silk, 3 decimetres in length, 

 and the whole was covered by a bell glass. A filament of glass was attached 

 to the paper, and moved as an index on a circle of paper on the glass shade 

 divided into degrees. The metal, which was an oblong fragment of electrc- 

 deposited palladium, about 8 millims. in length and 3 millims. in width, 

 being at rest in an equatorial positon (that is, with its ends averted from 

 the poles of the electromagnet), the magnet was then charged by connecting 

 it with the electrical battery. The palladium was deflected slightly from the 

 equatorial line by 10° only, the magnetism acting against the torsion of 

 the silk suspending thread. The same palladium charged with 604*6 

 volumes of hydrogen was deflected by the electromagnet through 48°, 

 when it set itself at rest. The gas being afterwards extracted, and the 

 palladium again placed equatorially between the poles, it was not deflected 

 in the least perceptible degree. The addition of hydrogen adds manifestly, 

 therefore, to the small natural magnetism of the palladium. To have some 

 terms of comparison, the same little mass of electro-deposited palladium 

 was steeped in a solution of nickel, of sp. gr. 1*082, which is known to be 

 magnetic. The deflection under the magnet was now 35°, or less than with 

 hydrogen. The same palladium being afterwards washed and impregnated 

 with a solution of protosulphate of iron of sp. gr. 1*048, of which the 

 metallic mass held 2*3 per cent, of its weight, the palladium gave a deflec- 

 tion of 50°, or nearly the same as with hydrogen. With a stronger 

 solution of the same salt, of sp. gr. 1*17, the deflection was 90°, and the 

 palladium pointed axially. 



Palladium in the form of wire or foil gave no deflection when placed in 

 the same apparatus, of which the moderate sensitiveness was rather an 

 advantage in present circumstances ; but when afterwards charged with 

 hydrogen, the palladium uniformly gave a sensible deflection of about 20°. 

 A previous washing of the wire or foil with hydrochloric acid, to remove 

 any possible traces of iron, did not modify this result. Palladium reduced 

 from the cyanide and also precipitated by hypophosphorous acid, when 

 placed in a small glass tube, was found to be not sensibly magnetic by our 

 test ; but it always acquired a sensible magnetism when charged with 

 hydrogen. 



