SPECIFIC GRAVITY. 137 



it. Find the loss in weight of the combined mass when 

 weighed in water. Do the same for the heavy body. 

 Subtract the loss of the heavy body from the loss of the 

 combined body. Divide the weight of the given body by 

 this difference. (Show that this divisor is as indicated in 

 243.) A modification of this method is to balance the 

 sinker in water. Then attach to it the light substance in 

 question, e . #., a cork, and determine the buoyant effort of the 

 cork, /. e., the weight of its bulk of water. Divide as before. 



(a.) The first method is illustrated by the following example : 

 (1.) Weight of cork and iron in air ... 82.4 g. 



(2.) 

 (3.) 

 (4.) 

 (5.) 

 (6.) 

 (7.) 

 (8.) 



water 52.4 g. 



water displaced by cork and iron 30. g. 



iron in air 77.8 g. 



" water 67.8 g. 



water displaced by iron 10. g. 



cork (3) -(6).... 20. g. 

 cork in air (1) (4). . . 4.6 g. 



(9.) Spec fie gravity of the cork (8) -s- (7) 23 



(10.) " " iron (4) -f- (6) 7.78 



246. To Find the Specific Gravity of 

 Liquids. The principle is unchanged. A simple 

 method is as follows : Weigh a flask first empty ; next, 

 full of water ; then, full of the given liquid. Subtract the 

 weight of the empty flask from the other two weights ; 

 the results represent the weights of equal volumes of the 

 given substance and of the standard. Divide as before. 

 A flask of known weight, graduated to measure 100 or 

 1000 grams or grains of water is called a specific gravity 

 flask. Its use avoids the first and second weighings above 

 mentioned, and simplifies the work of division. 



247. Another Simple Method.-The specific gravity of 

 a liquid may be easily determined as follows : Find the loss of 

 weight of any insoluble solid in water and in the given liquid. 



