SULPHURET OF POTASSIUM, AN EXCITING ELECTROLYTE. 
83 
sulphu retting solutions* * * § . In 1827 De la Rive quoted several such inversions of the 
states of two metals, produced by using different solutions, and reasoned from them, 
that the mere contact of the metals could not be the cause of their respective states, 
but that the chemical action of the liquid produced these states -f. 
18/8. In a former paper I quoted Sir Humphry Davy’s experiment (943.), and 
gave its result as a proof that the contact of the iron and copper could not originate 
the current produced ; since when a dilute acid was used in place of the sulphuret, 
the current was reverse in direction, and yet the contact of the metals remained the 
same. M. Marianini j adds, that copper will produce the same effect with tin, lead, and 
even zinc ; and also that silver will produce the same results as copper. In the case 
of copper he accounts for the effect by referring it to the relation of the iron and the 
new body formed on the copper, the latter being, according to Volta, positive to the 
former^. By his own experiment the same substance was negative to the iron across 
the same solution |j. 
1879. I desire at present to resume the class of cases where a solution of sulphuret 
of potassium is the liquid in a voltaic circuit ; for I think they give most powerful 
proof that the current in the voltaic battery cannot be produced by contact, but is 
due altogether to chemical action. 
1880. The solution of sulphuret of potassium (1812.) is a most excellent con- 
ductor of electricity (1814.). When subjected between platinum electrodes to the 
decomposing power of a small voltaic battery, it readily gave pure sulphur at the 
anode, and a little gas, which was probably hydrogen, at the cathode. When ar- 
ranged with platinum surfaces so as to form a Ritter’s secondary pile, the passage of 
a feeble primary current, for a few seconds only, makes this secondary battery effec- 
tive in causing a counter current ; so that, in accordance with electrolytic conduction 
(923. 1343.), it probably does not conduct without decomposition, or if at all, its 
point of electrolytic intensity (966. 983.) must be very low. Its exciting action 
(speaking on the chemical theory) is either the giving an anion (sulphur) to such 
metallic and other bodies as it can act upon, or, in some cases, as with the peroxides 
of lead and manganese, and the protoxide of iron (2046.), the abstraction of an 
anion from the body in contact with it, the current produced being in the one or the 
other direction accordingly. Its chemical affinities are such, that in many cases its 
anion goes to that metal, of a pair of metals, which is left untouched when the usual 
exciting electrotytes are employed ; and so a beautiful inversion of the current in re- 
lation to the metals is obtained ; thus, when copper and nickel are used with it, the 
anion goes to the copper ; but when the same metals are used with the ordinary elec- 
trolytic fluids, the anion goes to the nickel. Its excellent conducting power renders 
* Elements of Chemical Philosophy, p. 148. 
f Annales de Chimie, 1828, xxxvii. 231-237 ; xxxix. 299. 
+ Memorie della Society Italiana in Modena, 1837, xxi. p. 224. 
§ Ibid. p. 219. || Ibid. p. 224. 
