Chemistry and Physics. 431 



Hydrogen does not reduce it at a red heat. It burns with a 

 green flame in chlorine, forming boron and sulphur chlorides. 

 Sodium and potassium decompose it below dull redness with 

 incandescence. Water decomposes it violently, the reaction 

 being B 2 S 3 + (H 2 0) 6 = (B(OH,)) 2 + (H a S) 8 . Ammonia combines 

 with it to form a yellow powder, evolving great heat. Organic 

 compounds react energetically with it. 



Boron pentasulphide is a light white crystalline powder, fusing 

 sharply at 390° and having a density of 1*85. It is best made 

 by heating boron iodide with sulphur in a carbon disulphide 

 solution for 24 hours at 60°. The precipitated product is washed 

 with the disulphide to remove the iodine, with which it forms an 

 additive compound. It is hydrolysed by water into boric acid, 

 hydrogen sulphide and sulphur. When heated to its fusing 

 point in a vacuum it dissociates into the trisulphide and sulphur, 

 and is similarly decomposed when heated with mercury or silver. 

 — C. B., cxv, 203, 271 ; J. Chem. Soc., lxii, 1393, Dec. 1892. 



G. F. B. 



3. On the Oxidation of Different forms of Carbon. — Wies- 

 ister has examined different varieties of carbon under the micro- 

 scope while being subjected to the action of a mixture of sul- 

 phuric acid and potassium dichromate. Charcoal obtained by 

 heating soot in chlorine and hydrogen successively is rapidly 

 attacked owing to its finely divided state. Lignite consists of 

 brown transparent particles, becoming colorless by treatment 

 leaving a skeleton of cellulose. Anthracite, bituminous coal, 

 wood charcoal, soot and graphite, contain a small quantity of an 

 easily oxidizable substance which is readily dissolved by the 

 chromic solution, leaving a residue which is only very slowly 

 attacked. The black lung pigment acts like soot and hence must 

 be derived from the outer air. — Monatsb. xiii, 371 ; J. Chem. 

 Soc, lxii, 1273, Nov. 1892. g. f. b. 



4. On the Rise of Salt- solutions in Filter paper. — It was long 

 ago observed by Schonbein that, when a piece of filter paper is 

 immersed in a saline solution (1) the water rises more rapidly 

 than the dissolved salt and (2) the height to which the latter 

 rises is different for different salts. So that by this means it is 

 possible to recognize the different constituents of a complex so- 

 lution. E. Fischer and Schmidmer have investigated this phe- 

 nomenon more closely and have reached the conclusion that the 

 result is due to the differences in the diffusibilities of the dissolved 

 substances, that salt which has the greatest velocity of diffusion 

 rising most rapidly in the paper. Hence diffusion phenomena 

 can be studied in this way quite as well as by the use of mem- 

 branes ; the new method having the advantage that it is appli- 

 cable to all liquids which moisten filter paper. The authors used 

 in their experiments a glass tube 2 cm. in diameter and 70 cm. 

 long, containing six rolls of filter paper, each about 10 cm. long 

 and weighing about 7 grams. The paper had been purified by 

 washing with hydrochloric and hydrofluoric acids and the rolls 



