152 Generation of Sulphur in 



weighed wide-mouthed bottles with good stoppers should be 

 provided. When a specimen of mud is brought up from the 

 bottom, a sample of it is immediately taken with a spatula 

 and put into one of these bottles containing a known quantity 

 of ferric chloride solution, at least sufficient to completely 

 cover the sample of mud. Another sample, as nearly similar 

 to the first as possible, is taken and stoppered in another 

 bottle for drying. In this way a large amount of valuable 

 information might be gained; but it will be evident from the 

 nature of the case that the actual figures obtained in any one 

 particular case are affected by a considerable possible error. 



In the month of June 1881 I carried out a number of 

 laboratory experiments bearing on this subject, using the 

 sulphides of different metals of the iron group. These bodies 

 were all prepared in the same way, namely, by precipitating 

 the sulphates with sulphide of ammonium, and washing by 

 decantation in stoppered bottles, always filled up quite full. 

 A quantity of hydrated ferric oxide was also prepared by 

 precipitating ferric chloride with ammonia and washing. All 

 of these precipitates, when thoroughly washed, were preserved 

 suspended in distilled water in well-stoppered reagent bottles. 



Ferrous Sulphide and Ferric Oxide. When quite neutral 

 these substances do not re-act on one another, at least at once. 

 But if the water has the slightest acid reaction, reduction of 

 the sesquioxide and production of sulphur take place rapidly. 

 A mixture of Fe 2 O 3 and FeS in water and quite neutral was 

 corked up and allowed to stand for five days, when the sediment 

 was found to be separated into two sharply-defined layers the 

 upper red, consisting of the oxide, and the lower black, of the 

 sulphide. When brought together, therefore, in presence of no- 

 thing but distilled water, there is no appreciable resultant action. 



Manganous Sulphide can be preserved perfectly under 

 distilled water in well-stoppered bottles filled to the neck. 

 A considerable quantity was prepared in the summer of 1881, 

 and, when thoroughly washed, it was put away in three separate 

 bottles. The contents of only one bottle were used for experi- 

 mental purposes, and the upper part of it got coloured 

 immediately black with oxide of manganese, from the oxidation 

 of the flakes of sulphide which adhered to the surface of the 



