34: REPORT—1904. 
is one negative pole and three positive ones, and the E.M.F. between 
any two of them may be measured. Such a cell not only indicates 
whether a particular paste is abnormal or not, but each of the three 
groups of elements may be compared with an external standard. It is 
possible, of course, that a change resulting in one of the pastes may affect 
the neutrality of the solution, and so the E.M.F. of all three groups. All 
observations were made in a constant temperature room, the cells being 
immersed in paraftin oil. 
The earlier results of the investigation are omitted, but the differences 
in E.M.F. due to pastes made from purchased samples of mercurous 
sulphate are shown by measurements made of cell No. 1 (4 limbs) and 
cell No. 28 (2 limbs), the observations covering a period of rather more 
than two years. The pastes have been distinguished by the letters K, H, 
and R ; all were subjected to the same treatment and advantage taken of 
the latest methods for their preparation known at that time. 
TABLE 
es Clark Cell, No. 1 (4 limbs). | Pit drareoea 
Observation. ; _ a= : hoe rraeibe 
H>R. K>R. | Hee, |) ee 
Sept. 8,1902 .| +0-00213 +0:00047 | +000166 | +0-00168 
Hep. 30, 95,7 195 45 | 150. 4 104 
hci aes 150 16 | 104 79 
WDece (De. A ei, 123 AB 80 59 
Feb. 24,1903 . 94 2 Pee 52 No obs. 
June 24, ,, . 62 37 25 eas Ey 
Mavewe =. ok 37 30 aie, a3 
Feb. 61904. 27 41 | —0-0v014 | —50 
only 9; ,, —.-| 000001 Bk = 52 Ee 
It is clear that although the effect of each paste is not known two of 
them have certainly changed, of which one is K. Jn the chart curve 
HR shows the change in E.M.F. of the H group, assuming the R group 
to remain constant ; similarly the H ~ K curve represents the change in 
voltage of this group, K being assumed constant, and like remarks apply 
to the third curve. There is a sudden break in the directions of the 
curves H K and KR shown after the observations of November 2, 
while none is shown in H_ KR; the deflections consequently indicate that 
the element K must have changed in an abnormal fashion. Indeed 
between November 2, 1903, and July 9, 1904, the E.M.F. of the K group 
apparently increased by at least 00003 volt ; a rise of exceptional 
magnitude. <A fall in voltage is the usual feature. 
The fact that the E.M.F. of a cell had changed by as much as 0:16 
per cent. was very disconcerting. It is true that a difference between 
H and R was anticipated, for H was a pale yellow colour, while R. was 
grey. On the other hand the paste K was also slightly yellow, yet no 
such difference is observed between K and R. It was thought that the 
mode of manufacture of the sulphate might influence the properties of the 
product. Mercurous sulphate is often prepared by precipitation, either 
Hg,(NO;), and Na,SO, or Hg,(NO;), and H,SO, being employed ; 
traces of the resulting nitrate in the final product would certainly intro- 
duce a disturbing element. Again mercurous nitrate is often associated 
