664. I shall have occasion in these Researches, also, to class bodies together according to certain relations derived from their electrical actions (822.); and wishing to express those relations without at the same time involving the expression of any hypothetical views, I intend using the following names and terms. Many bodies are decomposed directly by the electric current, their elements being set free; these I propose to call _electrolytes_.[A] Water, therefore, is an electrolyte. The bodies which, like nitric or sulphuric acids, are decomposed in a secondary manner (752. 757.), are not included under this term. Then for _electro-chemically decomposed_, I shall often use the term _electrolyzed_, derived in the same way, and implying that the body spoken of is separated into its components under the influence of electricity: it is analogous in its sense and sound to _analyse_, which is derived in a similar manner. The term _electrolytical_ will be understood at once: muriatic acid is electrolytical, boracic acid is not. [A] [Greek: elektron], and [Greek: lyo], _soluo_. N. Electrolyte, V. Electrolyze. 665. Finally, I require a term to express those bodies which can pass to the _electrodes_, or, as they are usually called, the poles. Substances are frequently spoken of as being _electro-negative_, or _electro-positive_, according as they go under the supposed influence of a direct attraction to the positive or negative pole. But these terms are much too significant for the use to which I should have to put them; for though the meanings are perhaps right, they are only hypothetical, and may be wrong; and then, through a very imperceptible, but still very dangerous, because continual, influence, they do great injury to science, by contracting and limiting the habitual views of those engaged in pursuing it. I propose to distinguish such bodies by calling those _anions_[A] which go to the _anode_ of the decomposing body; and those passing to the _cathode, cations_[B]; and when I have occasion to speak of these together, I shall call them _ions_. Thus the chloride of lead is an _electrolyte_, and when _electrolyzed_ evolves the two _ions_, chlorine and lead, the former being an _anion_, and the latter a _cation_. [A] [Greek: anion] _that which goes up._ (Neuter participle.) [B] [Greek: kation] _that which goes down._ 666. These terms being once well-defined, will, I hope, in their use enable me to avoid much periphrasis and ambiguity of expression. I do not mean to press them into service more frequently than will be required, for I am fully aware that names are one thing and science another.