Chemistry and Physics. 421 



3. On the Industrial production of Liquid Carbon dioxide.— 

 In a report lately made to the Societe d'Encouragement, Troost 

 has called attention to the extent to which liquid carbon dioxide 

 is prepared for commercial purposes, the chief use in Germany 

 being in the preparation of beer and in France for the prepara- 

 tion of salicylic acid by the reaction of liquid C0 2 on sodium- 

 phenol. At the works of the Cornpagnie Generate des Produits 

 Antiseptiques, the carbon dioxide is produced by the combustion 

 of coke and is collected in a gasometer; from this it is drawn, 

 dried and compressed into iron bottles under pressures of 5, 25 

 and 71 atmospheres. Most of it is used in the manufacture of 

 salicylic acid, though it has other uses. At present the daily 

 output is 300 kilograms, but the capacity of the works is to be 

 increased to 1000 kilograms. It is sold at sixty centimes per 

 kilogram. It is used in making aerated waters, in the filtering 

 of wine, for cooling purposes in consequence of the absorption of 

 heat on vaporizing and for producing a high pressure in the 

 solidification of metals. — Bull. Soc. Pnc, July, 1892; Nature, 

 xlvi, 399, Aug., 1892. G. f. b. 



4. On the Oxidation of Nitrogen by the Spark. — The produc- 

 tion of small quantities of nitrous and nitric acids during the 

 passage of electric discharges through moist air, is well known. 

 Lepel has undertaken an investigation to determine the precise 

 nature of the chemical changes taking place, with a view of in- 

 creasing the yield. The first product, when the spark passes 

 through air, apparently, is nitrogen dioxide; which becomes tetr- 

 oxide by the oxygen of the air. This reacts with the aqueous 

 vapor, forming nitric acid and setting free nitrogen dioxide again, 

 thus: (NO a ) e + (H 9 0) s = (HN0 8 ) 4 + N a 2 . On further passing the 

 sparks, however, decomposition of the nitrogen oxides into their 

 constituents takes place ; so that in a closed space a limit is soon 

 reached beyond which there is no further increase in the produc- 

 tion of nitric acid. Hence the author has used a slowly moving 

 atmosphere, varying the pressure and the spark through a wide 

 range; and he has already increased the amount of combination 

 up to ten per cent of the air employed. The best effect is ob- 

 tained when the air is exposed under increased pressure to a 

 series of parallel spark-discharges in the same tube. The air in 

 the tube is changed intermittently, the gases passing into a large 

 absorption vessel containing water or alkali-solution. In his later 

 experiments Lepel has used a Topler machine having 66 revolv- 

 ing plates; and he thinks that with the high voltage discharges 

 lately produced by Tesla and others, the problem of producing 

 nitric acid from the atmosphere may be a commercial success. — 

 Ann. Chem. Phys., II, xlvi, 319, June, 1892. g. f. b. 



5. On the Inorganic sgnthesis of Azoimide. — Hitherto, azoi- 

 mide N 3 H has been obtained only from organic substances. 

 Wislicestus has now effected its synthesis from purely inorganic 

 materials. His method depends upon the interaction between 

 nitrogen monoxide gas and ammonia in presence of sodium. 



