464 Scientific Intelligence. 



of mercury at the temperature of ice-water. The liquid is then 

 distilled and freed from the remaining bromine by means of 

 powdered antimony. In the pure condition the oxybromide is a 

 fuming, colorless, mobile liquid boiling at 64-65°. It is unstable, 

 decomposing somewhat upon distillation, and being almost com- 

 pletely decomposed when its vapor is subjected to a red heat. It 

 acts but slowly upon water at ordinary temperature. Its specific 

 gravity is 245 at 15°. — Liebig's Ann., cccxlv, 334. h. l. w. 



3. The Industrial Preparation of Calcium Hydride. — It was 

 shown by Moissan that metallic calcium absorbs hydrogen when 

 heated, forming the colorless hydride CH 2 , and it is interesting 

 to learn from an article by Jatjbeet that this substance has 

 already been made on a commercial scale for the purpose of pre- 

 paring hydrogen for balloons. It is well adapted for this purpose 

 since it reacts with water according to the equation 



CaH 2 + 2H 2 C- = Ca(OH) 2 + 2H 2 . 



One kilogram of the substance thus liberates a cubic meter of 

 pure hydrogen. Metallic calcium is manufactured by the electro- 

 lysis of the fused chloride. The electrical energy required for 

 producing 100 kilograms of the metal in 24 hours is about 20 volts 

 and 7,500 amperes, or 150 kilowatts. The hydride is prepared 

 by heating the metal to a high temperature in horizontal retorts 

 in which hydrogen circulates. The gas is slowly absorbed, and 

 after several hours all the calcium is transformed into the 

 hydride. The commercial product occurs in white or gi*ay, 

 irregular porous pieces, having considerable hardness. It is 

 insoluble in the common organic solvents, but is instantly decom- 

 posed by cold water, similarly to calcium carbide. The product 

 is about 90 per cent pure, the impurities being chiefly oxide and 

 nitride. — Comptes Hendus, cxlii, 788. h. l. w. 



4. The Synthesis of Cyanogen and of Hydrocyanic acid from 

 the Elements. — It is stated in most of the chemical text-books 

 and reference-books that cyanogen gas has been produced (by 

 Morren) by the passage of the induction spark between carbon 

 points in an atmosphere of nitrogen. Theodore Wallis shows 

 that the electric arc, instead of the induction spark, was probably 

 used in the original experiments, and he shows further that by 

 neither of these means is cyanogen produced. The error has 

 arisen from the fact that hydrocyanic acid gas is formed in the 

 presence of moisture under the conditions of the experiment, 

 and the mistaking of this gas for cyanogen. The author has 

 made a careful study of the methods of distinguishing and 

 determining HCN and (CN) 2 in the presence of each other. The 

 most satisfactory means of separating them appears to be based 

 upon the fact that neutral or acid silver nitrate solution does not 

 absorb (CN) 2 while it does absorb HCN. — Liebig^s Ann., cccxlv, 

 353. h. L. w. 



5. A Gaseous Hydride of Calcium in Acetylene. — Hoffmeistee 

 has noticed that acetylene when prepared from certain specimens 



