506 Scientific Intelligence. 



difficulty than the diamond. At a dull red heat potassium 

 hydroxide attacks it, as also does a mixture of sodium and potas- 

 sium carbonates. Though friable, carbon boride is hard and can 

 be used to polish even the diamond, producing distinct facets. — 

 C. J?., cxviii, 556, 1894. G. F. B. 



4. On the Carbides of Calcium, Barium and Strontium. — By 

 placing a mixture of 120 grams calcium oxide and 70 grams car- 

 bon in the crucible of the electric furnace and subjecting it to the 

 action of a current of 350 amperes and 70 volts for 15 or 20 min- 

 utes, Moissan has obtained calcium carbide, the yield being from 

 120 to 150 grams. It has the composition CaC 2 and appears as a 

 homogeneous black mass, distinctly crystalline and readily cleav- 

 able. The crystals are brilliant but opake and have a sp. gr. of 

 2*22. They are insoluble in all ordinary reagents, are not altered 

 when heated in hydrogen or nitrogen at 1200°, or with silicon 

 or boron at a bright red heat ; neither sodium nor magnesium 

 attacks it at the melting point of glass, nor does tin at a red heat 

 or iron at a dull red : but at a higher temperature, an alloy of 

 iron and calcium is formed which contains carbon. Dry chlorine 

 does not attack it in the cold but at 245° it becomes incandescent 

 and yields calcium and carbon chlorides. Bromine acts similarly 

 at 350° and iodine at 305°. It burns in oxygen at a dull red 

 heat, and in sulphur vapor at 500°. It rapidly decomposes water, 

 developing heat and evolving almost pure acetylene. Fused 

 chromic trioxide oxidizes calcium carbide, evolving carbon dioxide. 

 Heated with absolute alcohol to 180° in sealed tubes it yields 

 acetylene and calcium ethoxide. 



Barium carbide is obtained by a similar reaction as a fused 

 black brittle mass composed of large lamellar crystals", having a 

 sp. gr. of 3*75 and a fusing point lower than the other carbides of 

 this group. Strontium carbide has a lustrous crystalline fracture 

 and asp. gr. of 3*19. Both these carbides are decomposed by 

 water, yielding the hydroxides and pure acetylene. Heated suffi- 

 ciently in the gaseous hj^dracids, the carbide becomes incandes- 

 cent. C 2 Sr becomes incandescent in dry chlorine at 197 and 

 C„Ba at 140°— C. R., cxviii, 501, 683, lw94. g. f. b. 



5. On the Size of the molecule of Mercurous chloride. — The 

 earlier determinations of vapor density in the case of mercurous 

 chloride gave numbers agreeing with the formula HgCI. But 

 since Odling showed that gold leaf immersed in the vapor became 

 amalgamated, dissociation was inferred. Y. Meter and Harris 

 now show that the gold leaf is instantly amalgamated in the 

 vapor of mercurous chloride, but that it becomes pure gold again 

 if allowed to remain in the vapor. Moreover by Meyer's method, 

 the authors have determined the vapor density at the temperature 

 of boiling sulphur (448°) and phosphorus pentasulphide (518°) 

 and find their results to agree with the early ones in correspond- 

 ing to the formula HgCI. A second series of experiments with a 

 mixture of free mercury and mercuric chloride gave almost iden- 

 tical results. The bulb of the density aj>paratus was then made 



