tly
harmonious and simple if they be considered as secondary results, and will
accord in their proportions with the oxygen and hydrogen evolved from water
by the action of a definite quantity of electricity.

751. I have experimented upon many bodies, with a view to determine whether
the results were primary or secondary. I have been surprised to find how
many of them, in ordinary cases, are of the latter class, and how
frequently water is the only body electrolyzed in instances where other
substances have been supposed to give way. Some of these results I will
give in as few words as possible.

752. _Nitric acid._--When very strong, it conducted well, and yielded
oxygen at the positive electrode. No gas appeared at the negative
electrode; but nitrous acid, and apparently nitric oxide, were formed
there, which, dissolving, rendered the acid yellow or red, and at last even
effervescent, from the spontaneous separation of nitric oxide. Upon
diluting the acid with its bulk or more of water, gas appeared at the
negative electrode. Its quantity could be varied by variations, either in
the strength of the acid or of the voltaic current: for that acid from
which no gas separated at the _cathode_, with a weak voltaic battery, did
evolve gas there with a stronger; and that battery which evolved no gas
there with a strong acid, did cause its evolution with an acid more dilute.
The gas at the _anode_ was always oxygen; that at the _cathode_ hydrogen.
When the quantity of products was examined by the volta-electrometer
(707.), the oxygen, whether from strong or weak acid, proved to be in the
same proportion as from water. When the acid was diluted to specific
gravity 1.24, or less, the hydrogen also proved to be the same in quantity
as from water. Hence I conclude that the nitric acid does not undergo
electrolyzation, but the water only; that the oxygen at the _anode_ is
always a primary result, but that the products at the _cathode_ are often
secondary, and due to the reaction of the hydrogen upon the nitric acid.

753. _Nitre._--A solution of this salt yields very variable results,
according as one or other form of tube is used, or as the electrodes are
large or small. Sometimes the whole of the hydrogen of the water decomposed
may be obtained at the negative electrode; at other times, only a part of
it, because of the ready formation of secondary results. The solution is a
very excellent conductor of electricity.

754. _Nitra