_Sulphurets._ Sulphuret of antimony, sulphuret of potassium made by
reducing sulphate of potassa by hydrogen; ordinary sulphuret of potassa.

Silicated potassa; chameleon mineral.

403. It is highly interesting in the instances of those substances which
soften before they liquefy, to observe at what period the conducting power
is acquired, and to what degree it is exalted by perfect fluidity. Thus,
with the borate of lead, when heated by the lamp upon glass, it becomes as
soft as treacle, but it did not conduct, and it was only when urged by the
blowpipe and brought to a fair red heat, that it conducted. When rendered
quite liquid, it conducted with extreme facility.

404. I do not mean to deny that part of the increased conducting power in
these cases of softening was probably due to the elevation of temperature
(432. 445.); but I have no doubt that by far the greater part was due to
the influence of the general law already demonstrated, and which in these
instances came gradually, instead of suddenly, into operation.

405. The following are bodies which acquired no conducting power upon
assuming the liquid state:--

Sulphur, phosphorus; iodide of sulphur, per-iodide of tin; orpiment,
realgar; glacial acetic acid, mixed margaric and oleic acids, artificial
camphor; caffeine, sugar, adipocire, stearine of cocoa-nut oil, spermaceti,
camphor, naphthaline, resin, gum sandarach, shell lac.

406. Perchloride of tin, chloride of arsenic, and the hydrated chloride of
arsenic, being liquids, had no sensible conducting power indicated by the