54 JUNIOR GRADE SCIENCE 



Relative density of a substance which floats in water. In the 

 case of a body which is lighter than water, this method can be used 

 with the assistance of a sinker, of sufficient weight to sink the body. 

 The method is exactly the same as before, with the exception that the 

 sinker is suspended in water throughout the experiment. Its weight 

 does not in any way affect the results, as it is for the time being a part 

 of the balance, just as the pans are. 



Relative density of a liquid. If a stopper be weighed in air, in 

 a liquid, and in water, the loss of weight in each case is equal to the 

 weight of a portion of liquid of the same volume as the stopper. From 

 these numbers the density of the liquid can be calculated. 



The relative density of the\ _ weight of a given volume of liquid 

 liquid J . weight of an equal volume of water* 



The volume of a solid which is soluble in water. This method 

 can be used to find the volume of a solid which dissolves in water. 

 Instead of weighing the solid in water it can be weighed in some liquid 

 in which it does not dissolve. The loss of weight gives the weight of 

 a volume of the liquid equal to the volume of the body. From this 

 the weight of an equal volume of water can be obtained, by dividing 

 by the relative density of the liquid. In this way the density of solids 

 soluble in water may also be obtained. Sugar may be weighed in 

 alcohol. Many substances which are soluble in water are insoluble in 

 petroleum. 



