472 Mr. E. E. Hughes on some Properties 



partial. Tho experimental tube was contained in a water- 

 bath in which was placed a thermometer, so that the action at 

 different temperatures might be investigated. It was noticed 

 that where the dried hydrogen-sulphide gas came in contact 

 with the filaments of cotton-wool covered with the pentoxide, 

 a yellow deposit, presumably sulphur, was obtained. Whether 

 this decomposing action is due to the finely divided oxide 

 superficially covering the filaments, or not, is an open question. 

 Moreover, it was observed that whilst the hydrogen-sulphide 

 gas passed, the white oxide assumed a yellowish tint, which 

 disappeared entirely when subsequently the hydrogen passed 

 through. 



The hydrogen was first passed through the apparatus for 

 about one hour and a half to displace the air ; the tube was 

 then weighed, replaced in the water-bath, and the hydrogen 

 sulphide passed through for about two hours, and the hydrogen 

 sulphide again displaced by hydrogen before a second weighing 

 was made. The temperature of the bath was read at intervals, 

 and the mean of the readings taken as the temperature of 

 investigation. 



In an experiment conducted at a temperature of about 

 15°, the weight of magnesia taken was 0*7597 gram ; after 

 passing hydrogen sulphide, and again displacing this by 

 hydrogen, the weight was found to be 0*7600 gram, or an 

 increase of 0*0003 gram. Another experiment, conducted 

 under precisely similar conditions, gave the following details. 

 Weight of oxide taken was 0*6360 gram, which, after the 

 passage of the gas, was found to weigh 0*6368 gram, showing 

 an increase of 0*0008 gram ; both of these increases are 

 within the limits of errors of experiment and may safely be 

 considered as such. 



In an experiment conducted at a mean temperature of 40°, 

 the result was of a similar character. Thus, having taken 

 0*8315 gram of the oxide, the increase in weight of this was 

 0*0011 gram. Hence it may be concluded that, under the 

 conditions of these experiments, this change, which is an 

 exothermic change, and therefore one which might be expected 

 to take place, does not take place. 



An experiment was made in which a drop of water from 

 a pipette was dropped on to the magnesia, and the tube 

 weighed. On passing the hydrogen sulphide through this 

 mixture a rapid change is evident, the white oxide becoming 

 of a greenish-yellow colour. 



The temperature of the bath during this experiment was 

 15°. The weight of the oxide and water in the tube before 



