Resistance and other Properties of Sulphur. 



151 



An improvement was introduced into the insulation of the elec- 

 trodes. The platinum wires were fused into glass tubes from 12 to 

 14 inches in length. These were fixed into hard dry wood at a dis- 

 tance of several inches from their ends. In this way the only part 

 that can possibly conduct is removed further from the source of heat. 



The ends of the electrodes were flat plates, formed by bending the 

 platinum wire upon itself three or four times, and then welding it 

 together, also for greater security a strip of platinum-foil was welded 

 to the back of each. 



The length of AB was 3*35 cm., the width 0*45 cm., and the 

 distance apart 0'2 cm. 



The tube in which the sulphur was boiled was formed by fusing^ 

 up the end of a piece of combustion -tubing about 9 inches long, and 

 wide enough to allow the glass tubes to be inserted in the sulphur 

 without danger of touching the sides, and thus forming a circuit 

 through hot glass. 



It was surrounded to the height of 3 inches by a copper tube, closed 

 at the bottom, the intervening space being filled with sand. 



To avoid the chemical action which has been shown to take place 

 when platinum is exposed for any length of time to sulphur at a high 

 temperature, the electrodes were kept out of the liquid until every- 

 thing was ready for taking a reading ; they were then inserted, and 

 the readings having been taken as quickly as possible, they were 

 removed. 



At the end of each set of experiments the wires were examined 

 and found in every case to be free from any appearance of the dark 

 film observed in the preliminary work. 



Before introducing them into the next specimen of sulphur they 

 were ignited in the blowpipe-flame until perfectly clean. 



The method used was to place the sulphur in circuit with a battery 

 and a high resistance galvanometer (R 11,700 ohms). In order to 

 avoid chemical action it was considered better to reduce the number 

 of observations and to commence with the boiling point. 



At 440° C. pure sulphur gave a deflection of 545 



to 570 divisions. 

 350° C. „ „ „ 75 



300° C. „ „ „ 15 



Those previously found, for precipitated sulphur at the same tem- 

 perature, were 512, 73, and 15. I have therefore concluded that the 

 two curves are identical. 



When the sulphur was removed from the circuit and a known 

 resistance inserted, the calculated specific resistance was about one- 

 fifth larger than that given by precipitated sulphur. 



