Letts and Rea — The Chemistry of Foul Mud Deposits 173 



hydrogen sulphide was evolved and eventually it was found that the reaction 

 was quantitative, namely : — 



Na 2 S + 2C0 2 + 2H 2 = 2Na (HC0 3 ) 2 + H 2 S. 



Action of Carbon Dioxide on Calcium Sulphide, 



The next experiments were performed with calcium sulphide. When 

 some of this was placed in water and a stream of carbon dioxide passed 

 through the mixture, it was found that about 4^3 per cent, was decomposed 

 in the sense of the reaction : — 



OaS + 2C0 2 + 2H 2 = H a S + Ca(HC0 3 ) 2 . 



Action of Carbon Dioxide on Magnesium, Sulphide. 



At first this was obtained from Kahlbaum, but later it was prepared by 

 heating magnesium metal in a stream of hydrogen sulphide. This magnesium 

 sulphide was then placed in water and a stream of carbon dioxide passed 

 through, and the liberated hydrogen sulphide collected in a standard solution 

 of arsenic chloride, when it was found that all the magnesium sulphide was 

 decomposed, probably thus : — 



MgS + 2C0 2 + 2H 2 - H 2 S + Mg(HC0 3 ) 3 . 



Action of Carbon Dioxide on Ferrous Sulphide. 



Mr. McKee proceeded as follows 1 : — 



" A preliminary experiment showed that when carbon dioxide was passed 

 through recently precipitated ferrous sulphide suspended in water, the 

 escaping gas blackened lead paper. 



" An experiment was next made to ascertain the amount of sulphuretted 

 hydrogen which might be formed. 



" For this purpose an apparatus was constructed, consisting of a carbonic 

 anhydride generator (Kipp) connected with a wash-bottle containing water, 

 and a second one containing a mixture of sodium carbonate and ferrous 

 sulphate (solution, to remove oxygen, or traces of it) ; and finally the carbon 

 dioxide passed into a flask provided with a cork and two tubes which 

 contained water and ferrous sulphide. The purified carbon dioxide was led 

 into this flask through a tube passing nearly to its bottom, and could either 

 be allowed to escape through a shorter tube in the cork, or could be plugged 

 with a clip. 



" The method employed was as follows : — 



"All the various parts of the apparatus were first filled with carbon dioxide. 



1 hoc. cit., p. 124. 



2 f2 



