1906-7.] The Electric Conductivity of Sea-Water. 
233 
XXIV. — The Electric Conductivity and Refracting Power of ninety 
samples of Sea- Water, and a comparison of these with the 
Salinity and Density. By E. G. Hill, B.A. Oxon, D.Sc. Dublin, 
Professor of Chemistry, Muir College, Allahabad . Communicated 
by Sir John Murray, K.C.B. 
(MS. received June 6, 1907. Read June 24, 1907.) 
There has been considerable discussion as to whether any physical 
constant of sea-water can be used to give an accurate measure of its total 
salinity, and from theoretical reasoning it would appear obvious that, in 
so complex a mixture, no physical constant can give an accurate measure of 
either the total amount of dissolved salts or of the chlorine present. In a 
paper communicated to this Society,* Mr J. J. Manley showed that the 
optical method for distinguishing between various samples was as delicate 
as the relative density method, but the refractometer used was expensive 
and not fitted for use on board ship. In a second paper j* the same author 
compares the electric conductivities of a few samples of sea- water with the 
relative densities and the chlorine per litre. He comes to the conclusion 
that the conductivity bears no simple relation to either of these properties, 
and disagrees with Knudsen, J who considers that the conductivity of a 
water may be taken as a measure of its salinity. 
The present author gives, therefore, the measurements of the conductivity 
and deviation made by himself on ninety samples of water which were 
collected in the Mediterranean for Mr Manley ,§ and compares these with the 
values obtained by Mr Manley for the total chlorine and relative densities. 
The Water . — The samples of water were taken by a pipette from the 
bottles in which they had been collected. The water was part of the 
samples used by Mr Manley, and was used before he made the majority of 
his measurements. 
The Electrical Conductivity. The Wheatstone’s Bridge. 
The bridge used consisted of a calibrated platinum-iridium wire about 
a metre long. This was highly insulated, and stretched by a heavy weight 
at one end. The ends of the bridge had a resistance equal to that of 21 
mm. of the bridge wire, and the total length of the bridge was 1047 mm. 
* Proc. Roy. Soc. Edin., Jan. 1900. t Proc. Roy. Soc. Edin., Nov. 1902. 
% Berichte der Kommission zur wissenschaftlichen Untersuchung der ddnischen Fahrwasser 
(Copenhagen, 1900). § Proc. Roy. Soc. Edin., 1907, p. 210. 
