A Calorimeter for the Human Body. 



239 



From these experiments the mean error is 218 calories, or on, say, 

 70,000 (emitted in forty minutes) = 0'3 per cent. 



I now felt able to rely on the work undertaken with the calori- 

 meter ; still the instrument had to be tested, and with this object it 

 was applied to the determination of the heat lost by a jar holding 

 6 or 7 litres of hot water and comparing the heat recovered with the 

 heat lost by the water ; the calorimeter was also used towards the 

 estimation of the heat produced by the combustion of a known 

 volume of pure hydrogen gas, comparing the heat recovered with 

 that known to be produced by the combination of that volume of gas 

 with oxygen, and this work I undertook in conjunction with 

 R. B. Floris, F.C.S. 



The first set of experiments with hot water proved very trouble- 

 some. It was found necessary to mix the layers of water in the jar 

 before and after the experiment, and to read correctly and quickly a 

 thermometer registering up to 0*02 of a degree centigrade ; more- 

 over the loss of heat could not be determined while the jar was being 

 carried to and shut up in the calorimeter ; and a similar difficulty 

 was experienced on removing the jar from the calorimeter at the end 

 of an experiment. Notwithstanding these many causes of error, as 

 will be seen in the following table, the mean of the results approxi- 

 mated very closely to the calories calculated from the loss of heat of 

 the water. 



If, for instance, the jar contained 6 litres of water or 6000 grams, 

 and lost 10 of temperature in the calorimeter, say, from 75 to 65 C., 

 then 60,000 calories, with slight corrections for the specific heat of 

 water at that temperature, and the thermal capacity of the jar, would 

 have to be found in the calorimeter. 



These experiments are tabulated as follows : 



Difference. 

 1'74 per cent. 

 -8-04 

 + 1-15 

 + 0-49 

 -M5 

 -1-66 

 + 4-66 

 -1-04 

 + 3-87 

 -4-88 



-5-62 



Mean.. 59,785 



60,642 



-1-41 



