Kraus and Hunt — Sulphur and Celestite. 241 



The sulphur was calculated from the hydrogen sulphide 

 obtained directly by the liberation with hydrochloric acid, 

 absorbed in potassium hydroxide, acidified and titrated with 



iodine solution. 



100 



The silica is present, no doubt, as free silica. The value of 



the ratios of the oxides of the calcium and magnesium, as also 



that of the carbon dioxide, give the following proportion : 



CaO (-3493) ) . CQ ( . 105Q) __ ,. 004 . j 

 MgO (-3795) j ■ 0i M 7 ~ 5y J - 1 UU4 • l - 



Hence, this rock may be considered as a siliceous dolomite. 

 The sulphur trioxide represents the total amount of sulphur 

 present as sulphate and sulphide, whereas the hydrogen sul- 

 phide is to be considered as being derived from a sulphide 

 only. Hence, if we consider the hydrogen sulphide as being 

 due to the decomposition of the strontium sulphide and, 

 therefore, deduct from the percentage of strontium oxide given 

 in the analysis, the amount necessary to unite with the 0*02 per 

 cent of sulphur* to form strontium sulphide, the following 

 relationship between the ratios of the strontium and barium 

 oxides and the sulphur trioxide, actually present, is revealed : 



I BaO I '° 061 ' 74 : S0 3 '00516 = 1-099 : 1. 



These values are so close that we must consider the evidence 

 in support of the above theory as very conclusive, namely, that 

 the celestite as the source of the sulphur is partially reduced 

 to strontium sulphide, which, when acted upon an acid and 

 even by water under certain conditions, f will liberate hydrogen 

 sulphide. Oxidation of the hydrogen sulphide will, of course, 

 then give rise to the sulphur. That the sulphur should be 

 associated with celestite is from the foregoing self-evident. 



Osann,^: in reviewing Sherzer's theory of the origin of sul- 

 phur at the Woolmith quarry, suggested that it was doubtlessly 

 due to the reduction of the strontium sulphate, as is now 

 revealed by the analysis above to be the case. As to how the 

 strontium sulphate has been reduced to the sulphide, nothing 

 definite can be said at this time. Doubtlessly, it is the result 

 of the action of the organic matter present, which may in 

 some cases be quite high. Whether organic matter alone, or 

 perhaps with moisture, but unaided by bacteria, can cause a 

 reduction of the sulphate, is now being investigated. 



* Determinations from other portions of this same layer showed as much 

 as 0'12 per cent hydrogen sulphide. The analysis was, however, not complete 

 and, hence, is not given. These figures show, nevertheless, that sulphureted 

 hydrogen may be liberated in appreciable amounts. 



t Compare Bischof 's Chemische Geologie, 1863, i, 833. 



X Groth's Zeitschrift fur Krystallographie, etc., xxviii, 321, 1897. 



