v| _ RATE OF EMISSION OF ENERGY 159 
found from these experiments that the heat emission from the 
1 gram of radiferous barium, containing about 1/6 of its weight of 
pure radium chloride, was 14 gram-calories per hour. Measure- 
ments were also made with 0:08 gram of pure radium chloride. 
Curie and Laborde deduced from these results that 1 gram of pure 
radium emits a quantity of heat of about 100 gram-calories per 
hour. This result was confirmed by the experiments of Runge and 
Precht! and others. As far as observation has at present gone, 
this rate of emission of heat is continuous and unchanged with 
lapse of time. Therefore, 1 gram of radium emits in the course of 
a day 2400, and in the course of a year, 876,000 gram-calories. 
The amount of heat evolved in the union of hydrogen and oxygen 
to form 1 gram of water is 3900 gram-calories. It is thus seen 
that 1 gram of radium emits per day nearly as much energy as is 
required to dissociate 1 gram of water. 
In some later experiments using 0°7 gram of pure radium 
bromide, P. Curie? found that the temperature of the radium 
indicated by a mercury thermometer was 3° C. above that of the 
surrounding air. This result was confirmed by Giesel who obtained 
a difference of temperature of 5° C. with 1 gram of radium bromide. 
The actual rise of temperature observed will obviously depend upon 
the size and nature of the vessel con- 
taining the radium. 
During their visit to England in 
1903 to lecture at the Royal Insti- 
tution, M. and Mme Curie performed 
some experiments with Professor 
Dewar, to test by another method the 
rate of emission of heat from radium 
at very low temperatures. This method 
depended on the measurement of the 
amount of gas volatilized when a 
radium preparation was placed inside 






a tube immersed in a liquefied gas 

at its boiling point. The arrange- 
ment of the calorimeter is shown in 
Fig. 31. 
1 Sitz. Ak. Wiss. Berlin, No. 38, 1903. 2 Société de Physique, 1903. 
Fig. 31. 
