102 DIVERS AND SHIMIDZU 



form two series of salts in which they are strongly basic. Thus 

 differentiated from most metals, their behaviour ought to throw light 

 upon the relations of oxygen salts to 'haloid' salts; and in order to 

 show that they may thus be used, we shall take sulphates to represent 

 oxygen salts, and sulphides as haloid salts. 



A sulphate may be constituted as a sulphide with its sulphur 

 oxidised, or it may be oxidised metal combined with oxidised sulphur, 

 or, again, have other constitutions which we here pass over. An 

 examination of the mercury and, say, the magnesium salts seems at 

 once to settle this point, because mercury sulphide is one of the most 

 stable compounds known, and mercury sulphate is instantly decom- , 

 posed by water, while magnesium sulphide is decomposed by water, and 

 magnesium sulphate is a most stable salt, quite unaffected. For mag- 

 nesium here preserves its oxylic union with sulphur, {}Ig=02=S0<^, 

 and drops that with sulphur direct, (Mg=S), while mercury behaves in 

 the reverse way, as the result, we may well conclude, of the well- 

 known affinity of mercury for sulphur rather than oxygen, and that of 

 magnesium for oxygen rather than sulphur. 



Many elements, and sulphur is one of them, form more than 

 one oxygen acid and corresponding series of salts, and the question 

 suggests itself, whether in the less oxidised salts there will not be a 

 constitution intermediate to those of haloid and fully oxidised salts. 

 In organic chemistry this question has long been answered, and the 

 less oxidised salts, distinguished by the termination, — onatcs, re- 

 cognised as constituted partly as oxylic salts, partly as haloid salts, 

 as the following names and furmulœ will serve to make clear : — 

 Ethyl potassium sulphate Et K SO, = ^^ \ SO^ 



Ethyl potassium sulphonate Et K SO^ = ^^ > SO^ 



Et 1 



Ethyl potassium sulphide Et K S = k ( ^' 



