alents of simple _ions_.

835. x. Electro-chemical equivalents are always consistent; i.e. the same
number which represents the equivalent of a substance A when it is
separating from a substance B, will also represent A when separating from a
third substance C. Thus, 8 is the electro-chemical equivalent of oxygen,
whether separating from hydrogen, or tin, or lead; and 103.5 is the
electrochemical equivalent of lead, whether separating from oxygen, or
chlorine, or iodine.

836. xi. Electro-chemical equivalents coincide, and are the same, with
ordinary chemical equivalents.

837. By means of experiment and the preceding propositions, a knowledge of
_ions_ and their electro-chemical equivalents may be obtained in various
ways.

838. In the first place, they may be determined directly, as has been done
with hydrogen, oxygen, lead, and tin, in the numerous experiments already
quoted.

839. In the next place, from propositions ii. and iii., may be deduced the
knowledge of many other _ions_, and also their equivalents. When chloride
of lead was decomposed, platina being used for both electrodes (395.),
there could remain no more doubt that chlorine was passing to the _anode_,
although it combined with the platina there, than when the positive
electrode, being of plumbago (794.), allowed its evolution in the free
state; neither could there, in either case, remain any doubt that for every
103.5 parts of lead evolved at the _cathode_, 36 parts of chlorine were
evolved at the _anode_, for the remaining chloride of lead was unchanged.
So also, when in a metallic solution one volume of oxygen, or a secondary
compound containing that proportion, appeared at the _anode_, no doubt
could arise that hydrogen, equivalent to two volumes, had been determined
to the _cathode_, although, by a secondary action, it had been employed in
reducing oxides of lead, copper, or other metals, to the metallic state. In
this manner, then, we learn from the experiments already described in these
Researches, that chlorine, iodine, bromine, fluorine, calcium, potassium,
strontium, magnesium, manganese, &c., are _ions_ and that their
_electro-chemical equivalents_ are the same as their _ordinary chemical
equivalents_.

840. Propositions iv. and v. extend our means of gaining information. For
if a body of known chemical composition is found to be decomposable, and
the nature of the substance evolved as a primary or even a secondary result
(743. 777.) a