To measure the specific latent heat of ice by the method of mixtures
The first step is to measure the specific heat capacities of copper and water by the methods described earlier in this chapter. For our present purpose we may assume the following values, using the SI sub-unit Jig K.
Specific heat capacity of water = 4.2 Jig K
Specific heat capacity of copper = 0.40 Jig K
In this experiment we shall use a polished copper calorimeter in a polished copper jacket similar to that shown in Fig. 42.3. The copper calorimeter and stirrer are first weighed empty, and then with the calorimeter about two-thirds full of water warmed to a temperature about 6 K above room temperature.
A thermometer is placed in the water, and some small pieces of ice are carefully dried on a cloth or filter paper. The water is stirred, the temperature noted, and immediately the dry ice is added. Stirring continuously, sufficient ice is added to bring the final steady temperature down to about 6 K below room temperature. This final steady temperature is noted and the calorimeter and its contents weighed
In this experiment the heat given out by the calorimeter, stirrer and water in cooling from the initial to the final temperature is equal to the heat received by the ice. ow the ice may be regarded as receiving two lots of heat. First, the latent heat necessary to melt it to form water at 0 cC; and secondly, the heat to raise the now melted ice from 0 C to the final temperature 10.0 “C. Thus.
It will be noted that Rumford’s cooling correction, mentioned earlier, had been
applied in this experiment. It is important not to allow the temperature to go more than 5 or 6 K below room temperature otherwise water vapour in the atmosphere may condense to form dew on the outside of the calorimeter and give up latent heat to it.