74 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVI.) 
potassium for its electrolyte ( 1824 .); for although it could conduct the thermo 
current of antimony and bismuth in a certain degree, yet that degree was very small 
compared to the power possessed by the former arrangement, or to that of a circle 
in which the nitrous acid was between two platinum plates ( 1816 .). This remarkable 
retardation is consequent upon the assumption by the iron of that peculiar state 
which Schcenbein has so well described and illustrated by his numerous experiments 
and investigations. But though it must be admitted that the iron in contact with 
the acid is in a peculiar state ( 1951 . 2001 . 2033 .), yet it is also evident that a cir- 
cuit consisting of platinum, iron, peculiar iron, and nitrous acid, does not cause a 
current though it have sufficient conducting power to carry a thermo current. 
1844 . But if the contact of platinum and iron has an electromotive force, why does 
it not produce a current? The application of heat ( 1830 .), or of a little chemical ac- 
tion ( 1831 .) at the place of contact, does produce a current, and in the latter case a 
strong one. Or if any other of the contacts in the arrangement can produce a cur- 
rent, why is not that shown by some corresponding effect ? The only answers are, to 
say, that the peculiar iron has the same electromotive properties and relations as 
platinum, or that the nitrous acid is included under the same law with the metals 
( 1809 . 1835 .) ; and so the sum of the effects of all the contacts in the circuit is nought, 
or an exact balance of forces. That the iron is like the platinum in having no electro- 
motive force at its contacts without chemical action, I believe ; but that it is unlike 
it in its electrical relations, is evident from the difference between the two in strong 
nitric acid, as well as in weak acid ; from their difference in the power of transmitting 
electric currents to either nitric acid or sulphuret of potassium, which is very great ; 
and also by other differences. That the nitrous acid is, as to the power of its con- 
tacts, to be separated from other electrolytes and classed with the metals in what is, 
with them, only an assumption, is a gratuitous mode of explaining the difficulty, 
which will come into consideration, with the case of sulphuret of potassium, hereafter 
( 1835 . 1859 . 1889 . 2060 .). 
1845 . To the electro-chemical philosopher, the case is only another of the many 
strong instances, showing that where chemical action is absent in the voltaic circuit, 
there no current can be formed ; and that whether solution of sulphuret of potas- 
sium or nitrous acid be the electrolyte or connecting fluid used, still the results are 
the same, and contact is shown to be inefficacious as an active electromotive con- 
dition. 
1846 . I need not say that the introduction of different metals between the iron and 
platinum at their point of contact, produced no difference in the results ( 1833 . 1834 .) 
and caused no current ; and I have said that heat and chemical action applied there 
produced their corresponding effects. But these parallels in action and non-action 
show the identity in nature of this circuit, (notwithstanding the production of the 
surface of peculiar iron on that metal,) and that with solution of sulphuret of po- 
tassium : so that all the conclusions drawn from it apply here ; and if that case 
