392 Scientific Intelligence. 



substance, probably N 4 S 3 6 , was obtained by the action of nitro- 

 gen dioxide upon N 4 S 6 Br 2 . The authors intend to complete the 

 study of the substances that have been mentioned, and to extend 

 the investigation to the action of chlorine, iodine and the chlor- 

 ides of phosphorus upon nitrogen sulphide. — Berichte, xxix, 

 340. h. l. w. 



2. Manganese carbide. — Moissan has prepared, by means of 

 his electric furnace, a well-characterized compound CMn 3 . This 

 result confirms that of Troost and Hautefeuille, who obtained the 

 same substance by the use of a wind-iurnace. Moissan used 200 

 parts of manganese protosesquioxide and 50 parts of sugar char- 

 coal and heated the mixture in a carbon tube, closed at one end. 

 The compound is readily attacked by various chemical agents, 

 and the action of water upon it is especially interesting from the 

 fact that equal volumes of marsh-gas and hydrogen are evolved. 

 The following equation represents the reaction : 



CMn 3 + 6H 2 = 3Mn(OH) 2 + CH 4 + H 2 



No acetylene or ethylene is produced. — Compt. Rend., cxxii, 421. 



h. l. w. 



3. The preparation of pure strontium compounds. — Sorensen 

 has made a critical study ol various methods of obtaining stron- 

 tium salts free from barium and calcium. The process which he 

 recommends, after an elaborate series of experiments, is briefly as 

 follows: The greater part of the barium is removed by adding 

 concentrated hydrochloric acid to a solution of the chlorides until 

 strontium chloride begins to crystallize out upon cooling. A 

 precipitation by means of sulphuric acid is then made in the 

 hydrochloric apid solution, whereby most of the calcium is left in 

 solution. The sulphates are decomposed by warming with strong 

 ammonium carbonate solution, the washed carbonates are dis- 

 solved in nitric acid, the solution is evaporated to dryness, the 

 residue is dissolved in water and filtered, and the barium is com- 

 pletely removed by repeated fractional precipitations with small 

 amounts of dilute sulphuric acid in a solution containing -fa of its 

 volume of 66 per cent nitric acid. This separation is not con- 

 sidered complete until the last precipitate of sulphate is free from 

 barium. The nitrate solution is evaporated to a semi-solid condi- 

 tion, the mass is extracted with alcohol and the residue is washed 

 with the same liquid. This residue is dissolved in water and the 

 operation is repeated until the calcium has been completely 

 removed. The author obtained a yield of 76-77 per cent by this 

 method. 



The author calls attention to a rule which has an important 

 bearing upon the separation of barium, strontium and calcium 

 compounds from each other. He considers the rule to be quite 

 self-evident, but he believes that it has not always been taken 

 into consideration in the preparation of chemical products. It is 

 expressed by the statement that " Corresponding, isomorphous 

 salts of closely-related elements are more difficult to separate than 



