PRACTICAL STANDARDS FOR ELECTRICAL MEASUREMENTS. 103 
fitted with small corks, and the cell is finally sealed with marine glue. 
The position of the various parts is shown in the figure. (Both forms 
of glass vessels are stocked by Mr. A. C. Cossor, of 54 Farringdon 
Road, E.C.) 
In filling the vessels it is convenient to use small pipettes made of 
two glass tubes, the one about 3 inches long and 4 inch in diameter, and 
the other about 2 inches long and } inch in diameter. If the larger tube 
has one end drawn out in the form of a cone, a junction is easily made. 
The amalgam of type A is melted over a water-bath (its surface being 
flooded with dilute cadmium-sulphate solution), and is introduced by 
means of a previously warmed pipette into one of the limbs. After the 
amalgam has solidified this limb should be washed out with a little fresh 
cadmium-sulphate solution. If the amalgam of type B is used this wash- 
ing is unnecessary. The mercury is next introduced into the other limb, 
then the paste, using if necessary a tiny glass rod as a piston through the 
pipette, and afterwards a thick layer of finely pounded crystals is intro- 
duced into each limb. Saturated cadmium-sulphate solution is finally 
added. The cells are then to be exposed in a warm room for a week or 
more to allow some of the liquid to evaporate, and so loosely cement 
together the fine crystals. This crystalline plug keeps the contents in 
their proper places, and enables the cell to be transmitted through the 
post. The sealing of the cells is next completed, care being taken not to 
abnormally heat the contents. 
Cells which are submitted for comparison with the standards of the 
National Physical Laboratory should be accompanied with the following 
particulars :— 
1. Maker's name and address. 
2. Name! of the firms from whom the chemicals used in the manufacture of the 
materials were purchased 
3. Number of the method employed in the manufacture of the mercurous 
sulphate. 
4, Type of cadmium amalgam used. : 
5. Notes on any peculiarities observed in the preparations. 
The Transformation of Aromatic Nitroamines and Allied Substances, 
and its Relation to Substitution in Benzene Derivatives—Report of 
the Committee, consisting of Professor F.S. Kippine (Chairman), 
Professor K. J. P. Orton (Secretary), Dr. S. RuHEMANN, Dr. A. 
Lapworts, and Dr. J. T. Hewirr. 
I, Nitroamines. 
THE nitroamines of the benzene series, which were discovered by Bam- 
berger (1893), exhibit in a very marked degree a property frequently 
found in analogous derivatives of anilines—namely, of changing into an 
isomeride in which the group, the nitro group, &c., originally linked to the 
nitrogen atom, has become attached to the ortho or para carbon atom of 
the nucleus. 
The mechanism of this has in the case of the nitroamines been but 
!. This information is only required so that the number of different sources of the 
materials can be estimated. 
