Chemical Affinity in terms of Electromotive Force. 337 



described for the determination of the radiation-correction 

 during the experiment: thus, in the illustration given, 



Millims. 

 per hour. 

 Observed rate of alteration after experiment concluded + 2*0 

 Calculated „ „ „ +1*95 



Mean +1*97 



Hence the losses by radiation during 8, 10, and 12 minutes 

 are respectively, +0'26, +0*33, and +0*39; and the true 

 rise in temperature of the calorimeter is found thus : — 



t=8. £ = 10. t=12. 



Reading of calorimeter-ther- ^ 



mometer t minutes after V 201-05 201-0 200'9 



conclusion of experiment ) 

 Radiation-loss during t mi- \ ,Q.%a _j_033 4- 0-^9 



nutes J 



Calculated temperature of" 



calorimeter at close of > .'/:' 



experiment . . . 



Average 201-31 millims. 



Reading of calorimeter-thermometer at 1 -ip^.7 

 commencement of experiment . . .J 



?j 



Calculated rise of thermometer .... 34*61 „ 

 Correction for radiation during experiment — 0*31 „ 



Corrected rise of thermometer .... 34*30 „ 



Since the water-equivalent of the calorimeter &c. is 1094*5, 

 and 11*28 millims. of the thermometer-scale represent 1°C, 

 the amount of heat actually produced is 



34*30 



1 g x 1094*5 = 3328 gramme-degrees. 



44. Two other small corrections also have to be applied to 

 the heat-evolution thus determined. In the first place, the 

 escaping gases pass out saturated with moisture, the evapo- 

 ration of which absorbs a certain amount of heat. In each 

 experiment the average temperature was close to 15°, at which 

 temperature the tension of aqueous vapour is 1*27 centim. or 



1*27 



—=w- atmosphere, =1*67 per cent. Hence every 1000 cub. 



centims. of evolved gas would contain 16*7 cub. centims. of 

 water-vapour (at 0° and 760), weighing 0*0134 gramme; the 



