410 Scientific Intelligence. 



Senderens have now produced this gas \>y the action of finely 

 divided metallic nickel upon mixtures of hydrogen and carbon 

 monoxide or of hydrogen and carbon dioxide. In each case the 

 only products are methane and water vapor. In the case of car- 

 bon monoxide the reaction takes place readily at 250°, but it 

 ceases when the temperature is allowed to fall below 180°. A 

 slightly higher temperature is required for the reduction of 

 carbon dioxide. The nickel used for this purpose should be 

 freshly reduced at a temperature approaching 300°. — Comples 

 Reiidus, cxxxiv, 514. h. l. w. 



3. Calcium silicide. — Moissan and Dilthey have re-investi- 

 gated the compound CaSi 2 , which was first obtained by Wohler, 

 and has since been prepared by several other chemists, but with 

 conflicting statements in regard to its properties. The method 

 of preparation consisted in heating an intimate mixture of equal 

 weights of silicon and calcium oxide in a carbon tube in an elec- 

 tric furnace. It is necessary to interrupt the heating as soon as 

 the mass has fused, for the prolonged action of carbon on the 

 fused mass gives calcium carbide, and finally silicide of carbon. 

 The following reaction takes place : 



2CaO + 5Si = 2CaSi 2 + Si0 2 . 

 The silica unites with the excess of lime, forming calcium sili- 

 cate. The calcium silicide thus produced has a metallic appear- 

 ance and forms brilliant crystals of a grayish color. Its specific 

 gravity is about 2*5. When heated in the air it is only super- 

 ficially oxidized, but it burns when exposed to cold fluorine and 

 when heated in contact with chlorine, bromine and iodine. Water 

 acts slowly upon the powdered substance with the evolution of 

 hydrogen. Cold, concentrated hydrochloric acid attacks the 

 substance with the production of a mixture of hydrogen and 

 hydrogen silicide, while the dilute acid produces with it only 

 hydrogen. — Comptes Rendus, cxxxiv, 503. h. l. w. 



4. Specific Heat, and Volumetric Determination of Vanadium. 

 — Matignon and Monnet, by the use of iron-vanadium and 

 aluminum-vanadium alloys have obtained the values '1258 and 

 *1235 for the specific heat of vanadium. These values taken in 

 connection with the accepted atomic weight, 51, give the values 

 6 "4 and 6 '3 for the atomic heat, which are in accordance with 

 Dulong and Petit's law. The authors state that they determine 

 vanadium very simply and accurately by oxidizing V 2 4 to V 2 5 , 

 by means of potassium permanganate. The reduction is made 

 by a current of sulphur dioxide in sulphuric acid solution ; then 

 the excess of the gas is boiled off. The end of the reaction in 

 the titration is very sharp and the color is persistent. Aluminum 

 does not interfere with the determination. In the case of the 

 iron vanadium alloy the separation of iron was effected by fused 

 potassium hydroxide, or better by attacking the powdered alloy 

 directly with sodium peroxide. The latter operation gives a rapid 

 separation and it is recommended for the determination of vana- 

 dium in steels, etc. — Comptes JRendus, cxxxiv, 542. h. l. w. 



