Density and SG
 

 

HOME page for Main Menu

SECTION 1 - PROPERTIES OF FLUIDS 

1.1  DENSITY 

The density of any fluid is defined as the mass per unit volume and is denoted by "ρ " 

             

since, any volume is proportional to a linear dimension cubed. 

It should be noted that the density of a liquid remains sensibly constant because the volume occupied by a given mass of liquid is almost invariable.  But in the case of gas, the density will vary as the volume occupied by a given mass of gas varies.  From this it may be deduced that a liquid may be taken as virtually incompressible while, of course, gases are compressible. 

1.2    SPECIFIC GRAVITY OR RELATIVE DENSITY 

The specific gravity or relative density of a fluid is defined as the mass of a given volume of a fluid divided by the mass of the same volume of water and is denoted by  

                         

If V is the volume of a liquid and of the water, ρ1 is the density of the liquid and ρw is the density of the water 

then     

1.3   THE HYDROMETER 

The principle of the common hydrometer depends upon the fact that when a body floats in a liquid the gravitational force on the mass of the volume of liquid displaced is equal to the gravitational force on the mass of the body.  That is, it depends upon Archimedes' principle.


MEASUREMENT OF DENSITIES AND SPECIFIC GRAVITIES 

Object:  To determine densities and specific gravities. 

Apparatus: 

Universal Hydrometer
4 No. Hydrometer Jars

 

 

 

 

 

 

 

 

 

 

 

 Analysis: 

The specific gravity is read directly from the scale in the hydrometer.  

Method: 

(a)        Fill one hydrometer jar with sufficient water to float the hydrometer and check that the scale marking corresponding to the depth of immersion reads 1.00. 

(b)       Fill three hydrometer jars with the liquids to be tested with sufficient of the liquids to float    the hydrometer and note for each liquid the scale reading. 

Since                   then       and the units are kg/m3

 

Return to Lab experiments

Home page for Main Menu

 

horizontal rule

Last Edited :  20 February 2015 12:29:04