With eighteen different voltaic couples, by rise of temperature from
60° to 160° F., the electromotive force in twelve cases was increased,
and in six decreased, and the average proportions of increase for the
eighteen instances was 0.10 volt for the 100° F. of elevation.

A great difference in chemical composition of the liquid was attended
by a considerable change in the order of the volta-tension series, and
the differences of such order in two similar liquids, such as
solutions of hydric chloride and potassic chloride, were much greater
than those produced in either of those liquids by a difference of 100°
F. of temperature. Difference of strength of solution, like difference
of composition or of temperature, altered the order of such series
with nearly every liquid; and the amount of such alteration by an
increase of four or five times in the strength of the liquid was
rather less than that caused by a difference of 100° F. of
temperature. While also a variation of strength of liquid caused only
a moderate amount of change of order in the volta-tension series, it
produced more than three times that amount of change in the
thermo-electric tension series. The usual effect of increasing the
strength of the liquid upon the volta-electromotive force was to
considerably increase it, but its effect upon the thermo-electro-motive
force was to largely decrease it. The degree of potential of a metal
and liquid thermo-couple was not always exactly the same at the same
temperature during a rise as during a fall of temperature; this is
analogous to the variations of melting and solidifying points of
bodies under such conditions, and also to that of supersaturation of a
liquid by a salt, and is probably due to some hinderance to change of
molecular movement.

The rate of ordinary chemical corrosion of each metal varied in every