98 REPORT—1905. 
It is suggested that persons interested in the matter might help by setting 
up cells in accordance with this specification and submitting them for 
test at the laboratory. 
' Of the grant made to the Committee in 1904 a balance of 37. 4s. 10d. 
remains. 
The work which remains to be done on the standard cell, and with the 
Ampére Balance, will all involve considerable expense, and to meet this 
the Committee ask for reappointment, with a grant of 25/. in addition to 
the balance now in their hands. 
APPENDIX. 
On the Preparation of a Cadmium Cell. By ¥. E. Surru. 
(From the National Physical Laboratory.) 
The research on standard cells has been continued at the National 
Physical Laboratory on the lines indicated in the last Report to the 
Association. Taken as a whole, the results are very satisfactory, but it 
is thought desirable to still continue the observations on some of the 
older cells before publishing the results in detail, 
Mr. G. A. Hulett, of Michigan, has completed a chemical research on 
mercurous sulphate, which throws considerable light on the anomalies 
reported to the Association last year. Very slight changes can still, 
however, be traced to this salt, but fortunately they are of no commercial 
significance. The 125 per cent. amalgam also produces slight variations 
in the E.M.F. of the cell : these again are commercially unimportant, and 
a manner of overcoming them in cells employed at a standards labora- 
tory is indicated in this paper. The latter cells are set up with an 
amalgam entirely liquid at 0° C. 
At this stage of the research it is thought desirable to describe the 
methods by which the materials of the cell can be best prepared in the 
light of present information, and an appeal is made to those interested in 
the subject to set up one or more cells by these methods and submit them 
for comparison with the standards of the National Physical Laboratory. 
More light will thus be thrown on the slight discrepancies already 
referred to, and the degree of accuracy with which the cell can be con- 
structed will be established. In this way it is hoped to specify a cell for 
commercial purposes accurate at all ordinary English working temperatures 
to 1 part in 2,000, applying no temperature correction, or to 1 part in 
10,000 if the temperature correction be applied. 
In the specification which follows there are four methods of preparing 
the mercurous sulphate. The first of these is due to Professor H. S. 
. Carhart, Mr. G. A. Hulett, and Dr. Wolff, jun. ; the main features of the 
second method were suggested by Mr. Swinburne to Dr. Glazebrook, while 
the third and fourth methods have resulted from some experiments at 
the National Physical Laboratory. It is suggested that one only of these 
methods be eventually employed ; the observations on submitted cells 
will largely determine the choice, 
