494 



Mr. J. E. Petavel. An Experimental 



Table VI. (See fig. 9.) 



Superficial area of Platinum Ingot 30 sq. cm. 



Intensity of the Light from 1 sq. cm. of Platinum at the Temperature 

 of Solidification = 1-012. 



Time. 1 



Photometer 

 reading. 2 



Light. 3 



10 



145 -7 



1-119 



20 



148 -2 



1-054 



30 



150-1 



1-005 



40 



149-8 



1-013 



50 



150-1 



1-005 



60 



150 -3 



1-001 



70 



151 -5 



0-972 



80 



151-7 



0-967 



90 



163-3 



0-730 



100 



178 -8 



0-502 



1 The time is counted from the instant at which the blow -pipe was stopped. 



2 The photometer reading is the distance in centimetres between the photometer 

 head and the incandescent lamp which served as a standard of reference. 



3 The unit of light is the mean of a number of determinations made under the 

 " normal " conditions. 



Fia. 9. — Superficial area of platinum ingot, 30 sq. cm. (or 76 per cent, above the 

 normal) ; intensity of the light at the temperature of solidification, 1-012 (or 

 0*012 above the normal). 



10 



10 BO 



30 40 50 60 70 



Time in Seconds. 



60 90 too 



no 



melting point. In this case there is no flash up of the light, the three 

 parts of the curve being continuous. The photometric readings, re- 

 duced as shown below, vary but little from those obtained when the 

 curves are discontinuous, but for several reasons the results are likely 

 to be less consistent than when the conditions are so regulated as to 

 obtain the " flash." shown in fig. 8. 



