ELECTRICAL PROPERTIES OF PURIFIED SULPHUR. 245 
No. 8.—EXPERIMENTS ON SOME ELECTRICAL 
PROPERTIES OF PURIFIED SULPHUR. 
By Prorrssor THRELFALL, M.A., and J. Bernarp ALLEN, B.Sc. 
(Read January 10, 1898. ) 
Norr.—The experiments described in this paper form part of a more 
elaborate investigation. Other results of the investigation have already 
been published ‘‘ The Electrical Properties of Pure Sulphur,” Threlfall and 
Brearley, Phil. Trans. Vol. 187 (1896) A. In that paper many matters, 
here merely referred to, are fully dealt with, e.g., the methods of purifying 
the sulphur. Quantitative results are given for the conductivity of sulphur 
under various conditions of solubility. Section III of this paper deals with 
the general character of sulphur conductivity when the sulphur is much less 
soluble. The general bearings of this section will be plainer if read in 
connection with the paper above referred to. 
SECTION I.—CONTACT FORCE BETWEEN DIFFERENT KINDS OF 
SULPHUR. 
Ir has been shown that when two metals are in electrical contact 
a difference of potential exists between them. The same thing 
has also been found to be true of different non-conductors. It 
seemed probable, therefore, that a similar difference of potential 
might occur between the same substance in different molecular 
conditions. The following experiments were undertaken with a 
view to determine whether any such voltage could be detected 
between sulphur in the soluble and insoluble states. 
As a first method an electrometer needle was made of sulphur, 
half of it being soluble, and the other half insoluble. This was 
hung within the quadrants of an electrometer, which were joined 
in adjacent pairs, so as to be virtually semicircles at different 
potentials. If, then, one end of the needle were at a higher 
potential than the other, a deflection would be produced reversing 
in direction upon interchanging the potentials of the semicircles. 
As an alternative method sulphur quadrants were made, alternate 
quadrants being formed of the soluble and insoluble modifications. 
Above these was hung an ordinary electrometer needle. If any 
voltage existed between the quadrants the needle would be 
deflected from its position of equilibrium upon charging it. 
The principal obvious source of error to be guarded against 
was the disturbing effect of ordinary electrostatic induction. The 
electrometer used was of the Clifton pattern. The case was lined 
with tinfoil, except at the front and back, which were of glass. 
Cardboard shutters covered with tinfoil were made to cover these 
