ON ELECTROANALYSIS. 145 
apparatus described by Dr. Sand (Trans. Chem. Soc. 91, 373 (1907) 
and 93, 1572 (1908) more portable and readily set up without sacrificing 
any of its essential features. The stand has been made completely 
portable by. providing it with a special cap which hinders the mercury 
forming the connection between the stationary and moving parts from 
being split during transport. A special clutch has also been designed 
which allows the moving parts to be readily thrown in and out of gear 
with the motor without stopping the latter. Such an arrangement 
becomes necessary when it is desired to actuate several sets of apparatus 
from a single shaft driven by one motor, or when a small motor-generator 
is employed for the double purpose of supplying the current and rotating 
the electrode, or lastly, when a water or hot-air motor is employed which 
cannot be stopped instantly while the electrodes are in a wet state. All 
the apparatus for measuring the potential of the cathode has been 
assembled in a single portable potentiometer-box, which is also arranged 
to show the potential difference between the anode and the cathode. 
For this purpose it became necessary to design a special new form of 
portable capillary electrometer. A full description of all the apparatus 
referred to will be published shortly. It was exhibited to Section 1 of 
the International Congress of Applied Chemistry. 
Experiments are also in progress with anodes made partly of glass and 
partly of platinum, and with cathodes of metals other than platinum. 
A very careful study has also been made of the composition of the 
deposit of lead peroxide obtained during the analysis of lead solutions. 
Results differing by more than 1 per cent. have been found in the labora- 
tories of Hollard. (Analyse des Bétaux (190) and Classen (‘ Quantitative 
_ Analyse durch Elektrolyse,’ 5th edition, 1908, p. 125.) It has now beer 
found that in a moist atmosphere lead peroxide will take up water at a 
temperature of about 200°, but will lose it exceedingly slowly at this 
temperature in a perfectly dry atmosphere. These facts are quite suffi- 
cient to explain the discrepancies observed. On the other hand, it has 
been found that lead peroxide deposited with a suitable current density 
at about 90-95° contains only about 4 per cent. of water after drying 
with alcohol and ether. It is here desiccated as a result of electric 
endosmose, and this method of depositing is recommended as by far the 
most trustworthy and simple. These results will also be published 
shortly. 
The Study of Hydro-aromatic Substances.—Report of the Com- 
mittee, consisting of Dr. K. Divers (Chairman), Professor 
A. W. Crosstgy (Secretary), Professor W. H. Perxin, Dr. 
M. O. Forster, and Dr. H. R. Le Sueur. 
1. Nitro Derivatives of O-Xylene. 
In the last Report? mention was made of the fact that when the mixture 
of two isomeric dimethylcyclohexadienes, obtained by elimination of two 
molecules of hydrogen bromide from 3:5-dibromo-1: 1-dimethylcyclo- 
hexane, was treated with a nitrating mixture, two substances melting at 
1 B.A. Report, 1908, p, 221. 
1909. iv; 
