Chemistry and Physics. 395 



copper being obtained by reducing copper oxide by means of 

 hydrogen or carbon monoxide. It has the composition Cu 2 N0 2 

 whether made with pure tetroxide or with tetroxide containing 

 nitrogen. Nitrocopper is permanent in dry air, but decomposes 

 into copper and nitrogen tetroxide above 90°. It is violently de- 

 composed by water, with the evolution of pure nitrogen dioxide 

 and the formation of a solution of copper nitrite and nitrate. 

 Hydrogen has no action in the cold but ammonium nitrate and 

 free ammonia are formed when the temperature is rapidly raised 

 to about 180°. Carbon monoxide likewise has no action in the 

 cold but on heating nitrogen tetroxide is evolved and reduced 

 copper is left. Sulphur dioxide on heating unites with the nitro- 

 gen tetroxide evolved forming the well known crystalline com- 

 pound, and leaving a residue of partly oxidized copper containing 

 some copper sulphate. Gaseous ammonia attacks it in the cold, 

 forming water vapor and white fumes of ammonium nitrite and 

 nitrate, the mass becoming suddenly incandescent, forming a large 

 quantity of ammonium salts and leaving a residue of copper and 

 ammonio-copper oxides. In short nitrocopper behaves as if while 

 the copper and the nitrogen tetroxide were intimately associated 

 together, each retained its own properties. — C. i?., cxvi, 756 ; J. 

 Chem. Soc, lxiv, II, 374, August, 1893. g. f. b. 



7. A Dictionary of Applied Chemistry ; by T. E. Thoepe, 

 assisted by eminent contributors. Vol. III., 1058 pp., 8vo. Lon- 

 don, 1893 (Longmans, Green & Co.). — This substantial volume of 

 upwards of 1000 pages marks the completion of a work of no 

 small magnitude, the successful accomplishment of which is a 

 matter for congratulation, not only for the editor-in-chief and his 

 associates but also for the chemical public as well. The general 

 scope of the work and its relations to the original edition of 

 Watts' Dictionary of Chemistry were explained in a notice in 

 this Journal (vol. xxxix, 519, also xxxviii, 409) of volumes I and 

 II. The third volume now issued contains more than two-thirds 

 the amount of matter in the other volumes taken together. It 

 is hardly necessary to state that the same high standard of excel- 

 lence is maintained in the many interesting and well digested 

 articles. Some of the subjects treated in greatest detail are the 

 following : Petroleum, by Boverton Redwood; photography, by 

 J. M. Thomson; soap, sulphur, sulphuric acid, by C. R. Alder 

 Wright; spectrum analysis by W. N. Hartley; starch, by John 

 Heron ; water, by P. F. Frankland; the articles upon the metals 

 and metallic salts are also to be noted. The value of the articles 

 is increased by liberal illustrations and by the references to the 

 general literature often given at the end. 



8. Connection between ether and matter. — Since Fresnel's time 

 the question has been debated whether (1) the earth carries with 

 it the ether in its immediate neighborhood, thus causing a dis- 

 turbance, or (2) rushes through it, and it through the earth, each 

 being independent and moving indej:>endently. Dr. Lodge has 

 endeavored to discover whether a rapidly revolving steel disc 



