40 



ELEMENTS OF LABORATORY WORK 



One form of an ice- calorimeter consists of several vessels 

 with ice arranged so that a hot body placed inside may cause 

 some of the ice to be melted and allow it to be measured. 

 With the construction shown in fig. 11, the quantity of water 

 which runs out into A measures the amount of ice melted by 

 the body placed in B. The ice-jacket c c prevents the ice in D 

 being melted by an external change of temperature. 



A calorimeter yielding more accurate results is one in which 

 the quantity of ice melted is measured by the diminution of 



Fig. 11. 



Fig. 12. 



volume then taking place. Water in B (fig. 12) is caused to 

 freeze around the tube A by a cold body placed within it. The 

 tube c is connected with a mercury gauge which indicates 

 changes of volume, and the body to be investigated is dropped 

 into A. This instrument requires more care in manipulation 

 than the former, especially in fixing on the gauge. The ex- 

 periment need not be performed at this stage. 



33. To Measure the Corresponding Temperature-changes 

 in Water and Copper. Weigh about 20 grams of copper wire 

 rolled into a ball ; attach a thread of silk, place it in a large 

 test tube together with a thermometer, and then immerse 

 both for five minutes in boiling water. The thermometer 

 will indicate the exact temperature. At the same time have 

 ready a known quantity of water in a glass beaker, with a 



