ON THE SPECIFIC HEAT OF WATER. 



the calorimeter. That is to say, the contents of the external bath were kept at the 

 same temperature as the contents of the calorimeter, the obturator was kept 10 C. 

 higher and the stinvr was kept rotating at 340 revolutions per minute. Each 

 <-\|eriment lastnl tVuin (id t,, <0 minutes, and the results are tabulated in the 

 following table as degrees per hour rise in temperature of the contents of the 

 calorimeter (2950 gr. of water) : 



TAHLK IV. 



Rise of 



temperature 



per hour. 



0-22 



0-155 



0-24 



0-24 



0-21 



0-19 



0-19 



0-15 



0-09 



These results are set out in fig. 8, from which it will be seen that from 10 C. to 

 70 C. the rate of rise owing to obturating heating, &c., is 0'21 C. per hour. From 

 0. to 10 C., during which interval the obturator is kept at a steady temperature 



O-4 



0-t 



10 



20 



30^ 



40^ 



y> 



70 



~5o 



Fig. 8. 



of 20 C., the rise per hour follows a straight line law. From 10 C. to 60 C. the 

 steadiness of the heating shows that there is no sensible uncertainty introduced by 

 evaporation. Between 70 C. and 80 C. there appeal's to be considerable uncertainty, 

 especially from 75 C. to 80 C. This may be partly owing to differences in the 

 ami unit <(' air c'ontaiiied in the water, which tends to come off at about this 

 temperature ; but is piokiMy chiefly due to some variability in the amount of escape 



