Resistance and other Properties of Sulphur. 147 



In the course of the work it was found that the vessels in which sul- 

 phur was boiled for any length of time were attacked. Ordinary 

 test-tubes invariably gave way, becoming coated internally with a 

 thin black film, which remained fixed to the glass. 



Ordinary tubes and glazed porcelain under the same circumstances 

 showed a number of dark spots, which proved to be sulphide of iron ; 

 even combustion- tubing did the same thing. 



All these experiments had been made with the flame of a bunsen 

 lamp acting directly upon the vessel containing the sulphur, and it 

 appears that no material will resist the attack of that body under 

 such conditions. It seems to be caused by over-heating a portion of 

 the vessel from which the liquid has been separated by the vapour, 

 when bubbles are formed. When the liquid falls back upon this over- 

 heated surface, chemical action commences. 



Further experiment, however, showed that when combustion- tubing, 

 or retorts of Bohemian glass, are protected from the direct action of 

 the flame, sulphur may be boiled or distilled in them without any 

 action whatever taking place. 



Investigations were also made on the nature of the electrodes, by 

 means of which a current could be made to pass through sulphur, 

 and upon the best form to be used to avoid chemical action. In the 

 previous work I used ordinary thin platinum wire, and failed to get a 

 current to pass. 



In repeating this experiment I used a wire of one millimetre 

 diameter, which had been exposed to great heat for a considerable 

 length of time, and found that the current passed readily. 



The same thing took place when some thin, very hard, carbon rods 

 were substituted for the platinum. The liquid was, however, dirtied 

 by particles of carbon torn away from the rods, and consequently I 

 have not considered the numbers obtained worthy of being recorded} 

 but simply the fact that with hard carbon rods for electrodes, sulphur 

 will conduct ; probably electric lamp filaments may prove good enough 

 to resist disintegration, if not too thin for the purpose. 



To test the effect of sulphur upon the electrodes, the containing 

 vessel was placed in a second one, half filled with mercury, which was 

 kept boiling several hours : this produced a steady temperature of 

 350°. The platinum electrodes were immersed in the liquid, and after 

 allowing them to remain undisturbed until the whole mass had 

 assumed the proper temperature, measurements were taken at stated 

 intervals. The method was to use a steady electromotive force, with 

 the sulphur in circuit, and a high resistance galvanometer. The 

 numbers given below show a conductivity increasing with the time of 

 contact between the electrodes and the hot sulphur. After the 

 experiment I found that the platinum was considerably discoloured. 



