Letts and Rka — The Chemistry of Foul Mad Deposits. 175 



" Probably the reaction is a reversible one, thus : — 

 Excess 



FeS + 2C0 2 + 2H 2 v Fe(HC0 3 ) 2 + H 2 S 



Excess 



" The ferrous sulphide used was liable to contain traces of its oxidation 

 products, but that would only reduce the amount of hydrogen sulphide 

 evolved. 



"The decomposition of ferrous sulphide in oceanic deposits has been 

 frequently denied ; but in the light of the experiments described above, there 

 cannot be any doubt that this reaction does take place, though probably 

 much less readily than the decomposition of the sulphides of the alkaline and 

 alkaline earth metals by carbon dioxide." 



Repetition of Mr. McKee's Experiments. 



Eather more than one half gram of ferrous sulphide ('526 grm.) was 

 prepared by the action of (colourless) ammonium sulphide on a weighed 

 quantity of ferrous sulphate, and was placed in a flask containing one litre of 

 distilled water (previously boiled to get rid of air and then saturated with 

 carbon dioxide). This flask was connected with a Kipp's apparatus for 

 generating carbon dioxide, and bulbs through which the latter passed, one 

 containing ferrous carbonate (or rather mixed solutions of ferrous sulphate 

 and sodium carbonate) to absorb traces of oxygen. 



The flask containing the water and ferrous carbonate was closed with an 

 india-rubber cork, through which three holes passed and glass tubes inserted 

 one leading to the bottom of the flask, and two shorter ones ; one of these 

 latter being attached to a stopper, consisting of a short length of india-rubber 

 tube and a piece of glass rod, while the other was attached to a Geissler bulb 

 containing an acid solution of arsenious chloride. 



From time to time the plug of the bulb containing the arsenious chloride 

 was removed so that a stream of carbon dioxide passed through the flask and 

 its contents. 



The flask containing the ferrous sulphide was placed in an incubator, 

 where it remained for about nine weeks, when all the ferrous sulphide had 

 disappeared and a colourless solution of ferrous bicarbonate remained. 



It is quite evident, therefore, that when ferrous sulphide is treated with 

 carbon dioxide (and water), the two following reactions eventually occur : — ■ 

 (1). FeS + CO, + H,0 = FeC0 3 + H 2 S. 

 (2). FeC0 3 + C0 2 + H 2 = Fe(HC0 3 ) 2 



Action of Hydrogen Sulphide on Metallic Carbonates or Bicarbonates. 

 The action was investigated in the case of the bicarbonates of the same 

 metals as those employed in the examination of the action of carbon dioxide 



