Chemistry and Physics. 389 



nitrogen when heated in a muffle with fuel instead of being 

 heated in an electric furnace. The black product, containing 

 lime and carbon as impurities, impure calcium cyanamide with 

 20 to 23^ per cent of nitrogen, can be treated for the production 

 of cyanides in various ways. It has been found possible, how- 

 ever, to produce the calcium cyanamide by a single operation in 

 the electric furnace according to the equation, 



CaO + 2C + N, = CaCN, + CO. 

 This direct process is more economical than the indirect one by 

 means of calcium carbide, and it will be of great practical import- 

 ance not only for the production of cyanides, but also for the 

 preparation of the substance for fertilizing purposes. 



It was found that calcium cyanamide, by a simple leaching 

 process, yields crystallized dicyandiamide : 



2CaCN', + 4H,0 = 2Ca(0H), + (CNNH J, . 

 The latter salt, then, by a simple fusion process, gives pure alka- 

 line cyanides : 



4CNN H, + 2Na,C03 + 4C = 4NaCN + 2NH3 + H^ + 6C0 + IST, 

 Another important result is the production of a substitute for 

 potassium cyanide, to be used in gold extraction, by fusing crude 

 calcium cyanamide with common salt. The product corresponds 

 to 30 per cent potassium cyanide, is extraordinarily cheap, and 

 answers the purpose as well as the pure salt. — Zeitsehr. angeio. 

 Chem., xvi, 533. 11. l. w. 



3. The Separation of Gaseous ^fixtures by Centrifugal Force. 

 — In the preceding number of this Journal a process for separat- 

 ing gases of different density by centrifugal force was noticed. 

 It seemed necessary, therefore, to mention here the fact that 

 Claude and Demoussy have reached the conclusion that this 

 method produces only very slight results, if, indeed, there is any 

 separation at all. These experimenters used a strong steel tube 

 about 50^'^' long and 3^™ in internal diameter, provided with stop- 

 cocks at the ends and with interior spring-valves near the ends. 

 The tube was charged with gaseous mixtures under pressure, so 

 that the differences in density were augmented, then it was ro- 

 tated about an axis perpendicular to its center at the rate of 3600 

 revolutions per minute. It did not seem prudent to exceed this 

 speed, which was greater than that used in the industrial machines 

 that have been referred to. The internal valves were adjusted 

 by springs in such a way that they opened by the action of cen- 

 trifugal force, and closed tightly after the speed became slower. 

 Analyses showed that the gases collected beyond the valves after 

 rotation did not differ appreciably from the original mixtures in 

 the cases of air, oxygen and carbon dioxide, and even hydrogen 

 and carbon dioxide. — Comptes Rendus, cxxxvii, 250. h. l. w. 



4. Investigations on Double Salts by Physical Means. — Dr. 

 H. W. FooTE of the Sheffield Laboratory has devised a method 

 for determining what double salts are formed by two single salts 

 with a common ion. The method depends chiefly on well-known 



