Dec., I913.] C U R R E N T T O PIC S . 7 3 7

Tantalum as a Cathode Material . G. OESTERHELD. (Z. Elek- trochem., xix, 585.)---Tantalum electrodes have a potential differ- ence against sulphuric acid about midway between those of copper and lead. They possess the disadvantage, for many electrolytic pur- poses, of readily absorbing cathodic hydrogen, which produces a considerable change of structure even when less than o.I per cent. is absorbed. The hardness and elasticity of the metal disappea L and it becomes useless as an electrode material. The paper contains measurements relative to the velocity of absorption of hydrogen and to its influence on the overvoltage.

l~'ormation of Methane. L. VlGNON. (Comptes Rendus, clvii, I 3 I . ) - - Me tha ne is formed from water vapor and carbon monoxide when they are heated together to temperatures ranging from 500 ° C. to 12oo ° C. in the presence of catalysts--iron, nickel, copper, silica, alumina, magnesia--in greater or less degree, sometimes in considerable quantity. In some cases there is an intermediate for- mation of carbides, which react with the steam; in others hydrogen is produced, which in presence of the catalyst reacts with the carbon monoxide.

Mel t ing-Points of Refractory Metals. ANON. (Brass World, ix, IO, 349 . ) - -These are recent determinations made by G. K. Burgess and R. G. Waltenberg, and the results are given in the Jour- nal of the Washinyton Academy of Science. They are :

C. o p. o

Ti tan ium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1795 3263 Vanad ium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172o 3128 Chromium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152o 2768 Manganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126o 2300

I r o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153o 2786 Cobalt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478 2692

Nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452 2545

The determinations were made with a micro-pyrometer, and the metals were melted in hydrogen gas to prevent oxidation. In some cases the metals were melted in an Arsem electric vacuum furnace.

A Ref rac to ry Furnace Lining. ANON. (Brass World, ix, IO, 3 6 o . ) - - F o r certain purposes, a furnace lining of a refractory nature may be made from asbestos and water-glass. I t is useful for patch- ing or pIugging cracks, as it does not crumble as readily as other similar compositions made from clay. The materials used are:

Fine asbestos . . . . . . . . . . . . . . . . . . . . . . . . . 4o pounds Wate r -g la s s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6o pounds

The water-glass is the sodium silicate of commerce, which is soluble in water. The asbestos and water-glass are mixed to a paste with water so that it can be worked.