98 ELEMENTARY GENERAL SCIENCE CHAP. 



such as brass, sulphur, copper, zinc, lead, glass, coal, and 

 flint. 



EXPT. 90. (1) Weigh a piece of india-rubber. Cut a strip 

 of lead, or of other metal, sufficient to act as a sinker 

 to the india-rubber, and weigh it (2) in air and (3) in water. 

 Attach the india-rubber to the lead, and find (4) the combined 

 weight in water. 



Then from 2-3 you know the weight of the volume of 

 water equal to the volume of lead, and from (1 + 2) -4 the 

 weight of the volume of water equal to the combined volume 

 of the lead and rubber, and hence the difference between these 

 values gives the weight of the volume of water equal to the 

 volume of the rubber. 



EXPT. 91. Repeat the preceding experiment with different 

 kinds of wood, cork, and other solids which float in water, 

 using a piece of lead as a sinker in each case. 



EXPT. 92. Weigh a glass stopper in air, then immerse it 

 successively in water, turpentine, methylated spirit, olive oil, 

 and petroleum, and notice the loss of weight in each case. 

 The loss of weight experienced by the glass stopper in each 

 experiment is equal to the weight of a portion of liquid of 

 the same volume as the stopper. The numbers obtained 

 therefore represent the weights of equal volumes of water, 

 turpentine, methylated spirit, olive oil, and 

 petroleum, and by dividing each by the 

 number obtained in the case of water, the 

 relative densities of the liquids are 

 obtained. 



Determination of Relative Densities by 

 Relative Density Bottle. The method of 

 determining the relative densities of liquids 

 by means of the principle of Archimedes is 

 an indirect one ; a simpler plan is to use a 

 specific gravity or relative density bottle. 

 Such a bottle (Fig. 43) consists of a small 



g lass flask > h ldin S ab ut 50 S 8 f Wftter ' 

 Gravity Bottle. It is provided with a nicely-fitting ground 



stopper, which is in the form of a tube 

 with a very small bore through it. It is used in determining 

 the relative density of liquids and powders. To use it, we must 

 first know the weight of the empty bottle and stopper. The 



