266 M. Scheerer 07i the Products of Oxidized Pyrites. 



The second layer forms a light yellow mass distinctly sepa- 

 rated from the first, and forming incrustations similar to those 

 which occur in (dolomitic) limestone caverns : B. 



The third is clothed with a layer of small white crystals : C. 



The analysis of A gave : 



80*73 peroxide of iron 



6*00 sulphuric acid 

 13*57 water 



100-30 

 which corresponds to a combination of 1 4 atoms of peroxide 

 of iron, 2 atoms of sulphuric acid, and 21 atoms of water, 

 which is expressed by the formula, 



2 (Fe7 SJ + 21 H; 

 or, 



2(F^ S^+ 20 Fe) + 63H, 



according to the manner in which the formula is written. This 

 iron-salt may be called, after the nomenclature of Berzelius, 

 the twenty-fold basic sulphate of the peroxide of iron; it is 

 the most basic salt as yet known. The oxygen of the oxide 

 amounts to the double of that in the water. It is perfectly 

 insoluble in water. 



Two analyses of the substance B gave the following results : 

 1 ' 2 



49*37 49-89 peroxide of iron 



32-42 32-47 sulphuric acid 



5-03 5-37 soda 



13*13 13-09 water 



99-95 100-82 



The soda was found in both analyses to contain a small quan- 

 tity of potash, which, however, is of no importance for the 

 formula, which may be thus expressed, 



4 Fe S + N S -{- 9 H ,* 



namely 4< atoms of peroxide of iron, 5 atoms of sulphuric 

 acid, 1 atom of soda, and 9 atoms of water. 



The substance C was found to be pure gypsum. 



In explaining the commencement and continuation of this 

 process, it must be supposed that the sulphate of the protox- 

 ide of iron was at first formed by the oxidation of the iron 

 pyrites ; this became gradually oxidized, and was deposited 



