20 PROPERTIES OF STEAM AND AMMONIA 



The various determinations of the mechanical equivalent seem to 

 justify the value established by Griffiths in 1893, namely, 



i im-an calorie - 4.184 joules 



I mean B.t.u. - 777.64 standard ft. Ib. 



ThU valur has been used. 



Various di-tiTin i nations of the absolute temperature of the ice-point 

 have been made. These indicate a value of 273.1 C. or about 459.6 F. 

 'I In- investigation of Rose-Innes (1908) points to the value 459.64, but 

 it does not appear that the degree of accuracy indicated by the fifth figure 

 is at present justified. The value 459.6 has been taken, and the relation 

 between absolute and ordinary temperatures is therefore given by 



r-/+ 459.6. 



