SULPIIUK AT SULPHUR BANK. 255 



the most fomiliar tacts of chemical geology and of experimental chemistry. 

 The relations of the two processes are readily seen from a thermo-cliemical 

 standpoint, for the reaction 



H=S + 40r=H-8O* hberates 201,500 calories and 

 IPS+ — IPO + S liberates 59,100 calories. 

 Hence if oxygen is present in excess, as it is at the surface of sulphur 

 springs and in porous sinters partially saturated with solutions of liydro- 

 sulphuric acid, this will simply bo oxidized to sulphuric acid. But if oxy- 

 gen is deticient, as it must be a short distance from the surface, a single 

 atom of oxygen by combining with \JVii to ^ffSO' would produce only 

 50,375 calories, or 8,725 less than it sets free according to the second of 

 the above reactions. Assuming, therefore, that the two reactions are ac- 

 complished in nearly the same time, sulphuric acid will be formed at the 

 surface of such a region as the Sulphur Bank and free sulphur below the 

 surface. This is in cori-espondence with observations at sulphur springs the 

 world over and with laboratory experiments. When sulphides of the alka- 

 lis are present the reactions are more complex, but sulphur is also separated 

 while hyposulphites are formed. There is thus nothing strange or novel in 

 the occurrence of sulphur under the conditions present at Sulphur Bank. 



A portion of the sulphur occurring at the Sulphur Bank is formed by a 

 slightly different reaction. Both on the surface and in the mine sulphurous 

 acid may be smelt, and earl}^ in 1887 the odor of this gas was suffocatingly 

 strong, even at some distance from the Flermann shaft. The sulphurous 

 acid undoubtedly comes up with the other volcanic emanations, though per- 

 haps not in direct contact with the hydrogen sulphide. Hydrogen sulphide 

 and sulphur dioxide decompose nuitually, forming water and sulphur. As 

 a conserpience, the timbers of the building above the shaft were coated with 

 incrustations of sulphur crystals in February, 1887, and, at the Fiedler 

 shaft as well, sulphur crystals had deposited in smaller rpuxntity by the same 

 method. 



Sulphuric acid and its effects—Tlie sulphuric ucid fomiod at or close to the sur- 

 face percolates downward to some extent and is eventually neutralized by 

 free bases and by salts of feebler acids. The neutralization of the acid is 

 chieflv effected bv the sodium cnrbonate Ijrought ui) in the hot waters and 



