AN:o24) The melting- and boilingpoints of metalloidsulphides. 3 



any protectiiig casing. In this way a close accordance of 

 the variations in the indications of the millivoltmeter and 

 the temperature of the bath was secured. Repeated trials 

 showed, that the thermoelements were not injured by the 

 liquids, and that their electromotive force was not changed 

 through the influence of the baths. The thermoelement 

 used consisted of 0,2 mm wire. It was checked by a comparison 

 with an element of the same kind made of 0,6 mm wire 

 tested at the Physikalische Reichsanstalt of Charlottenburg 

 and by experiments with several standardmaterials: The 

 meltingpoint of gold 1063,5° was determined in the usual way, 

 thus a small piece of goldwire was soldered between the 

 wires of the thermoelement and slowly heated in a bath and 

 the increase of the number of millivolts observed until the 

 gold melted and the needle of the millivoltmeter instantly 

 returned to Zero. The meltingpoint of pure sodiumchloride 

 801°, was measured from the coolingcurve of 15 g of this 

 material. The boilingpoints of sulphur, 444.5°, and of mer- 

 cury, 356,9°, were found in a way similar to the procedure 

 used at the experiments proper, a small testtube containing 

 sulphur or mercury was heated in the bath, until the ma- 

 terial started to boil regularly. The temperature of the bath 

 was taken at this moment. Repeated determinations gave 

 numbers, which seldom differed more than 2° — 3° from the 

 mean value, which was used. The correction of the thermo- 

 element at 200° was obtained through comparison with a 

 standard thermometer (Normaltermometer) approved of by 

 the Physikalische Reichsanstalt in Berlin. The O-position 

 of the millivoltmeter was in addition controlled with melt- 

 ing ice. 



The mineralsamples were kept in small testtubes, capil- 

 laries of refractory glass drawn över the blast (K- 

 glass, jenaglass, quarzglass), or in tubes of similar material 

 3 mm in diameter. The temperature of the bath 

 was raised by degrees and the behaviour of the sample 

 observed with magnifying glass or with the naked eye. Very 

 conspicuous is the beginning of the fusion of such substances, 

 which, as for inst. NaCl, before the fusion are awhitepowder 



