burgess: a micro pyrometer y 



standing error will be but a residual one. In the case of substances 

 of dissimilar properties such as salts and metals, this apparatus 

 must be used with caution, for, in general, a calibration made in 

 terms of the metal melting points, for example, will not serve for 

 the exact determination of the melting points of salts. 



The precision of the method is dependent mainly upon the 

 character of the melting of the substances observed. With metals 

 such as gold and nickel, which melt very sharply, a precision of 

 1° or 2° C. is obtainable. 



Fig. 1. A Micropyrometer 



The apparatus as constructed at the Bureau of Standards, 

 largely from suggestions due to Messrs. Crowe and Foote of this 

 Bureau, is shown in figure 1 ; in which L is the pyrometer lamp, R 

 the monochromatic glass, A the absorption glass, P the platinum 

 strip carrying the specimen, C the furnace window, B an air 

 blast for cooling the furnace. The microscope has a Bausch and 

 Lomb 48 mm. single achromatic lens and 6.4 X eye-piece and gives 



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