80 Intelligence and Miscellaneous Articles. 



This augmentation varies, too, a great deal, from one metal to an- 

 other. We remark that tin, thallium, cadmium, zinc, lead, are 

 found together towards the upper part : at about 200° and 230° their 

 resistance has doubled. Still above them are found steel and iron : 

 the resistance of the latter has doubled at 180°, quadrupled at 430°, 

 at 860° is about nine times as great as at zero. Palladium and 

 platinum, on the contrary, approach the axis of the temperatures ; 

 it is only in the vicinity of 400° and 450° that the augmentation 

 has acquired a value equal to that of the primitive resistance. Gold, 

 copper, silver, form an intermediate group. It may therefore be 

 said generally that, the less elevated the fusing-point of a metal, the 

 more rapidly does its conductivity diminish : iron and steel form 

 an exception to this law. In alloys the variation is always less 

 than in the metals which constitute them. In certain of them 

 (Grerman silver for example) it is very slight; and this renders 

 them valuable for the construction of standards and resistance-coils. 

 Approximately, it is in the metals in which the resistance is great- 

 est that its increase, under the influence of heat, is relatively the 

 most rapid. The slight differences of composition which alter so 

 profoundly the absolute resistance, have but a feeble influence on 

 the relative value of its augmentation by rise of temperature. — 

 Biblioiheque Universelle, Archives des Sciences Phys. et Nat., vol. li. 

 pp. 284-287. 



ON THE CONSERVATION AND THE PROPERTIES OF A PLATE OF PAL- 

 LADIUM SATURATED WITH HYDROGEN BY ELECTROLYSIS. BY 

 R. BOTTGER*. 



The Author has found that it is only after being heated to redness 

 that a plate of palladium, charged with hydrogen by electrolysis, 

 loses the hydrogen which it held by occlusion. This is readily 

 ascertained by immersing the plate in a solution of ferridcyanide of 

 potassium. In fact, as long as hydrogen is still present at the sur- 

 face of the palladium, reduction of the ferridcyanide into ferro- 

 cyanide is observed, which is easily recognized by means of the 

 properties of the salts of protoxide of iron. 



There are also other metals which thus absorb electrolytic hy- 

 drogen — as nickel, zinc, and cobalt. 



When a plate of palladium is coated with palladium-black, it 

 becomes saturated with hydrogen much more rapidly. If when 

 thus saturated it is wrapped in gun-cotton, the latter explodes at 

 the end of a few seconds, and the plate burns during five or six 

 minutes with a flame of feeble brightness. 



A plate of palladium charged with hydrogen and left in the air, 

 loses in time the gas occluded. Placed under water deprived of 

 air, under absolute alcohol, or ether, it loses at first a part of its 

 hydrogen with effervescence, but retains the rest without apparent 

 change. — Bibliotheq tie Universelle, Archives des Sciences, vol. li. p. 185. 



M. L. de la Rive, by a sudden and very great diminution of the conductivity; 

 nevertheless bismuth and antimony form an exception, and become, on the 

 contrary, better conductors on melting. 

 * Pogg. Ann. Jubclband, p. 150. 



