368 MR T. C. BALLLIE ON THE 



§ 6. Specific Heat of Nickel. — The determination of the specific heat of the nickel 

 has been found by far the most troublesome part of these experiments. A portion of 

 the cooling bar about 2*5 inches long had a hole drilled into it to receive the thermom- 

 eter. A little mercury was put into the hole along with the thermometer. It was 

 then heated and allowed to cool. At some instant the temperature was noted just as it 

 was let fall into a large calorimeter, and the heat given out by the nickel was measured 

 in the ordinary way by the method of mixtures. This was repeated at the same and 

 different temperatures, and the results were not quite concordant, but indicated that 

 the specific heat increased with temperature. As it was not quite certain that the 

 temperature in all parts of the interior of the piece of nickel was that of the mixture 

 when the readings were taken nickel turnings were tried. Several pieces of the turn- 

 ings made in turning down the nickel bars were tied together with a short piece of 

 thread, whose mass was negligible, and heated in the inner chamber of a double cylinder 

 of copper containing glycerine between the cylinders. This was heated to over 200°C. 

 and packed up with cotton wool in a wooden case provided with a contrivance for open- 

 ing a slide at the bottom and allowing the nickel to fall into the calorimeter at the 

 moment of opening. The calorimeter used was a small glass beaker of suitable dimen- 

 sions. With it the cooling correction was smaller than with a copper calorimeter of the 

 same size. It was hoped that as the heater cooled very slowly it would be safe to 

 assume that the temperature of the turnings after being in the heater some time would 

 be that of the thermometer whose bulb was inserted amongst them. As the heater 

 cooled, determinations of the specific heat could be done on the same day at lower and 

 lower temperatures. It was found that the sets of determinations obtained on separate 

 days did not agree no matter how long the nickel was kept in the heater, and as 

 all the quantities involved could be measured within 1 per cent., and the correction 

 for cooling was only about 1 per cent., the heater was regarded as the cause of the 

 irregularities. 



In some subsequent experiments the nickel turnings were heated in a steam jacket 

 of the usual laboratory pattern, and results agreeing within 2 per cent, were obtained 

 when the nickel was in the heater for not less than two hours. As the heat required to 

 raise the temperature of 1 gramme of water is not constant, but varies in a manner 

 depending on the thermometer used in the calorimeter, closer agreement than this is 

 not to be expected. The specific heat thus obtained was higher than that got for the 

 same temperature from the large mass cut off the cooling bar. At the same time there 

 is no reason for supposing that the specific heat would not be affected by the nickel 

 being cut up and distorted as it is in the form of turnings. 



The values of the specific heat given below were found from a solid piece of the 

 nickel weighing nearly 100 grammes, and as a glass calorimeter could not be used with 

 so large a mass, a copper calorimeter was made of thin sheet copper, the depth of it 

 being 5 inches, and the diameter 1\ inches. There was a slight recess along one side 

 to accommodate the thermometer and a flange round the lip by which it was suspended 



