TRITON, a genus of argillaceous earth, much used in the polishing of metals. It has its name from Tripoli in Barbary, from whence it was formerly brought to us, and has the following properties: 1. It does not effervesce with any of the acids. 2. It hardens in the fire; and by a considerable heat, its surface becomes vitrified. 3. Every kind of it, excepting that found in England, becomes red by calcination. 4. It is fusible by mixture with calcareous earth, as well as by means of borax and microcosmic salt. 5. Generally no salt can be extracted by washing, though sometimes the marine and vitriolic acid may be extracted by distillation. 6. When crude it imbibes water, but is not diffusible in it. 7. It tastes like common chalk, and feels sandy between the teeth, though no sand can by any means be extracted from it.
Tripoli is found of two different kinds: 1. Solid, and of a rough texture; brown, yellowish, and spotted like marble. 2. Friable and compact; granulated, brown, or yellowish; this last being the kind met with in England. This last kind has also been found in Scotland; but the rotten stone found in Derbyshire, and likewise much used in polishing, is quite another substance. According to Ferber, the rotten stone is tripoli mixed with a calcareous earth. In the memoirs of the academy at Paris, for 1769, it is asserted, that tripoli is a volcanic product. In proof of this, we are there informed, that a coal-mine at St. Etienne having accidentally taken fire, and the fire having extended to some beds of ichitus and bitumen, tripoli was found in the burnt parts of the strata, but nowhere else. Cronstedt is of opinion, that 100 parts of it contain 90 of siliceous earth, 7 of argill, and 3 of iron; but the red sort probably contains more iron.