174 Scientific Proceedings, Royal Dublin Society. 



The ferrous sulphide was then prepared and transferred to the flask, made 

 ready for it by means of a litre of air-free water which had been saturated 

 with carbon dioxide. A rapid current of that gas was then passed through 

 the contents of the flask for about ten minutes, and finally the shorter tube 

 was plugged on account of the rapidity with which ferrous sulphide is 

 oxidised by contact with the air ; no attempt was made to weigh it, but the 

 quantity precipitated from excess of ferrous sulphate solution by 10 c.c. of a 

 particular solution of ammonium sulphide (freshly prepared) was rapidly 

 washed and transferred to the flask with as little loss as possible, the amount 

 transferred being determined afterwards (see below). 



" The flask had a capacity of about 1| litres, so that there was about § litre 

 of carbon dioxide above the liquid. As the carbon dioxide was absorbed, the 

 pressure above the liquid decreased, and more gas bubbled in, keeping the 

 solution saturated. 



" The sulphide flasks were kept in an incubator at 35° C, the rubber tube 

 connecting them passing through a small hole in the top. The apparatus 

 was left undisturbed until all absorption of the carbon dioxide had ceased, 

 which took about eight days. The sulphide flasks were then disconnected 

 and the free hydrogen sulphide and undecomposed ferrous sulphide 

 determined in the following manner : — 



" 10 c.c. of the clear supernatant liquid were run into excess of standard 

 iodine solution (1 c.c = 0'2 mgm. hydrogen sulphide) and titrated back again 

 with sodium thiosulphate of corresponding strength. Next the flask was 

 well shaken in order to distribute the ferrous sulphide evenly throughout the 

 liquid, and, still shaking, 10 c.c. were withdrawn and run into excess of iodine 

 solution strongly acidified with hydrochloric acid, and the excess of iodine 

 determined as before. The first determination gave the amount of hydrogen 

 sulphide set free, the second, the hydrogen sulphide equivalent of the ferrous 

 sulphide, originally present, thus : — 



(1). FeS + Distilled Water. 



HjS originally present (as FeS) 

 „ evolved (free) 

 (2). FeS + Sea Water. 



H 2 S originally present (as FeS) 

 „ evolved (free) 



"The above figures show that quite enough hydrogen sulphide can be 

 obtained to cause a serious nuisance, from the action of carbon dioxide on 

 ferrous sulphide. 



