Page 109 - My FlipBook
P. 109
: ;
Dr. D. O. M. Le Crcn designed a form of
Pyrometers. pyrometer (Fig. 117) which gives more accurate
results than the pure gold test. The device is ex-
ceedingly simple and the designer says of it
"A small cube of soapstone is excavated to resemble an hour glass
in the upper expanded cavity is placed a small spherical mass of an alloy
composed of platinum and gold. The relative proportion of the two
metals governs the fusing points of the alloy. By varying the propor-
tions the temperature may be graduated to any extent within the limits
Fig. 118.
desired. The proper temperature of fusing for a given body is matched
with a pellet of alloy. The pyrometer is set in the muffle, and when the
temperature at which the porcelain fuses has been reached, the little
metal ball melts and runs down into the lower chamber." This method
makes possible a fair degree of accuracy, provided it is used each time
under similar conditions.
Since the introduction of electrical dental pyrometers, the fusing
of porcelain has been simplified, and positive results can be obtained.
To Dr. W. A. Price, of Cleveland, belongs the credit of placing the first
electric dental pyrometer on the market. The pyrometer designed bv Dr.
Price depends upon the principle of the thermo-pile or the thermo-couple
system (Fig. 118).
105
Dr. D. O. M. Le Crcn designed a form of
Pyrometers. pyrometer (Fig. 117) which gives more accurate
results than the pure gold test. The device is ex-
ceedingly simple and the designer says of it
"A small cube of soapstone is excavated to resemble an hour glass
in the upper expanded cavity is placed a small spherical mass of an alloy
composed of platinum and gold. The relative proportion of the two
metals governs the fusing points of the alloy. By varying the propor-
tions the temperature may be graduated to any extent within the limits
Fig. 118.
desired. The proper temperature of fusing for a given body is matched
with a pellet of alloy. The pyrometer is set in the muffle, and when the
temperature at which the porcelain fuses has been reached, the little
metal ball melts and runs down into the lower chamber." This method
makes possible a fair degree of accuracy, provided it is used each time
under similar conditions.
Since the introduction of electrical dental pyrometers, the fusing
of porcelain has been simplified, and positive results can be obtained.
To Dr. W. A. Price, of Cleveland, belongs the credit of placing the first
electric dental pyrometer on the market. The pyrometer designed bv Dr.
Price depends upon the principle of the thermo-pile or the thermo-couple
system (Fig. 118).
105
