ON THE ELECTRICAL PROPERTIES OF PURE SULPHUR. 
133 
the Chance sulphur given to us by Mr. Chance. This was melted and strained" to 
get rid of particles of dirt, and was then twice distilled. 
With this sulphur we made a film on April 17th, 1893, and put it in the box while 
still warm with phosphorus pentoxide and sulphuric acid. 
The data are—corrected area, 156*64 sq. centims. (including edge correction); 
thickness, *022686 centim. 
It consisted of soluble prismatic sulphur (probably without admixture of octahedral 
sulphur), with 5 per cent, of insoluble sulphur. Colour, clear lemon-yellow. When 
the plates were separated the greater part of the film was still transparent, but 
it became opaque on rubbing or attempting to detach it from the plates. We think 
it probable that since the film was much broken and torn up in forcing the plates 
apart, that it was in the transparent form during the experiments, at all events before 
it was heated. In this case, it must be considered to have consisted entirely of 
monoclinic and amorphous sulphur. 
An elaborate investigation of the properties was made but, as nothing new turned 
up, the table will afford sufficient information. The resistance is uniformly higher 
than in the case of the film of similar composition of November 9th, 1892. We 
attribute this to the fact that, having now a great deal more material, we probably 
succeeded with the purification rather better than before. Of course the test of 
burning two hundred grammes weight was carried out, and resulted in such an 
almost inappreciable residue that we must have succeeded better than was to be 
expected in keeping the dust off during the burning, or rather boiling. 
* Sulphur is conveniently filtered by means of glass wool in a zinc funnel. A bit of platinum wire 
gauze, folded several times, should be placed below the funnel to catch any shreds of glass that may 
come through. This precaution is very necessary. Chance sulphur treated like this has a horrible smell 
of gas lime when it is broken up after cooling, which shows that it requires to be distilled if sure results 
are to be obtained. 
