The apparatus consists of a small, electrically heated thermocouple bent into a loop at its extremity so as to hold the specimen, in the form of a bead, in contact with the thermojunction. It is based on the apparatus described by Ordway* but has new and simpler electrical arrangements. For convenience, the bead is normally observed through a 25 mm microscope objective, though a 16 mm objective (5 mm working distance) can be used without any special precautions.
The heating current is taken from any convenient 50 c/s supply and a vibrating switch driven from the same supply permits the heating current to flow only during alternate half-cycles, the measuring circuit being employed during the intermediate half-cycles. The power dissipated by the heater at maximum temperature (1750° C) is only about 6 W.
The apparatus gives extremely rapid results in comparison with normal techniques when put to such uses as melting-point determinations, studies of glass devitrification, growing single crystals for X-ray structure determinations, and delineation of phase equilibria; it should find widespread application in the fields of glass and ceramic technology.