66 FIRST YEAR COURSE IN GENERAL SCIENCE 



space at the same time. If the water reaches the 230 cu. 

 cm. line, the solid must have displaced 30 cubic centimeters 

 of water. Therefore its volume is 30 cubic centimeters. If 

 the weight is 96 grams, its density is" 3.2 grams per cubic 

 centimeter. (LABORATORY MANUAL, Exercise VI.) 



67. Finding the Density of a Liquid. The density of 

 a substance in the liquid form may be found in the following 

 way. Find the capacity of a flask or bottle by weighing it, 

 first empty, and then filled with water. If the flask when 

 filled with water weighs 75 grams more than when empty, 

 the capacity of the bottle is 75 cubic centimeters, because 

 1 cubic centimeter of water weighs 1 gram. Then find the 

 weight of the given liquid that is required to fill the same 

 bottle; for example, 79 grams. Make the same calculation 

 as in finding the density of a solid ; that is, divide the weight 

 of the liquid by the volume. 79 g. -=- 75 (cu. cm.) = 1.05 g. 

 per cu. cm., density. (LABORATORY MANUAL, Exercises 

 VII and VIII.) 



68. Specific Gravity. The expression specific gravity 

 is used to denote the relation between the weight of a 

 body and the weight of an equal volume of water. It is 

 really a comparison of densities. Specific gravity can be 

 determined by experiment without knowing the volume of 

 a body. 



It is well known that bodies seem to weigh less in water 

 than in air. It has been proved by repeated experiments 

 that this apparent loss of weight is always the same as the 

 weight of the water displaced. The volume of water dis- 

 placed is, of course, equal to the volume of the body 

 immersed. Therefore the apparent loss of weight is the 

 " weight of an equal volume of water." Hence, if we divide 

 the weight of the body in air by its apparent loss of weight 

 in water, we get the specific gravity. 



For example, a piece of marble weighs 230 grams. When 

 suspended from a balance so that it hangs in water, its 



