Chemistry and Physics. 375 



ured in the special apparatus, and from this gas volume the 

 weight of water present is calculated. The reaction taking 

 place is as follows : 



2CH 3 MgI + H 2 = 2CH 4 + MgI 2 + MgO. 



For the preparation of the reagents, which requires special pre- 

 cautions, as well as for the description of the apparatus, the 

 measuring part of which is based upon Lunge's nitrometer, refer- 

 ence must be made to the original article. — Zeitschr. analyt. 

 Chem., li, 680. h. l. w. 



5. Reduction of Vcmadic Acid in Concentrated Sulphuric Acid 

 Solution. — Cain and Hostetter have found that vanadium pen- 

 toxide in concentrated sulphuric acid solution is reduced imme- 

 diately and quantitatively to the quadrivalent condition by 

 hydrogen peroxide. All that is necessary is to evaporate the 

 solution until fumes are given off freely, cool, add a slight excess 

 of 3 per cent hydrogen peroxide, cover the flask and fume strongly 

 for a few minutes to destroy the excess of hydrogen peroxide, 

 after which the solution may be titrated with permanganate. It 

 was found that molybdenum, titanium and iron are not similarly 

 reduced, and that persulphates and also Caro's acid have the 

 same effect as hydrogen peroxide upon the vanadium pentoxide. — 

 Jour. Amer. Chem. Soc, xxxiv, 274. h. l. w. 



6. Die Zersetzang von Stickstoffdioxyd im elektrischen Glim?n- 

 strom. — An easily reproducible, beautiful and instructive demon- 

 stration experiment was performed by J. Zenneck before the 

 Physical Section of the 83d Convention of German Scientists at 

 Karlsruhe, on September 26, 1911. The apparatus was con- 

 structed of glass, and it may be described as follows. 



A cylindrical bulb with its long axis vertical was partly filled 

 with pure nitrogen tetroxide, N 2 <J 4 , which was maintained in its 

 more complex molecular condition and liquid state by surround- 

 ing the bulb with a freezing mixture of ice and common salt. A 

 horizontal glass tube of convenient diameter connected the top of 

 the bulb with a discharge tube, to be described later on. The 

 horizontal tube was drawn down to capillary dimensions not far 

 from its union with the bulb. Beyond the capillary section this 

 tube was provided with a glass stopcock. The discharge tube 

 was shaped like a vertical U, with relatively long " legs" or par- 

 allel branches which were comparatively close together. Near 

 the upper end of each leg a short, horizontal section of glass 

 tubing was sealed in place. These inlet and outlet tubes were at 

 the same level and both were situated in the plane of the U-tube. 

 The object of these tubes was to enable the experimenter to con- 

 nect the discharge tube with the above-mentioned horizontal 

 tube leading from the bulb, and with the rest of the train of 

 apparatus, by means of short pieces of rubber " connecting tub- 

 ing." Above the common level of the horizontal tubes each leg 

 of the U-tube was sealed to a vertical, cylindrical bulb. Each 

 bulb contained an electrode whose wire was sealed into the top of 



