3
3. Density Measurement Principles
3-1. Density
Density refers to the total mass of a sample per unit volume.
M
ρ
=
(
Unit: g/cm
3
)
V
ρ
: Density of sample (g/cm
3
)
M :
Mass
(g)
V :
Volume
(cm
3
)
3-2. Specific
Gravity
Specific gravity refers to the ratio of the density of a sample to the density of pure water at 4°C under a pressure
of 1013.25 hPa.
M
ρ
=
(No
unit)
V
x
ρ
4
ρ
: Density of sample (g/cm
3
)
M :
Mass
(g)
V :
Volume
(cm
3
)
ρ
4
: Density of water at 4°C
(0.99997 g/cm
3
1.000 g/cm
3
)
3-3. Archimedes’ Principle Of Density Measurement
The GXA-14 is combined with an electronic balance to measure the density of a sample based on the
Arichimedes’ principle.
Arichimedes’ principle
A body immersed in a liquid (or a gas) is subject to an upward force equal to the weight of the liquid
(or the gas) it displaces. The upward force is buoyancy.
3-4. Density Of A Solid
The density of a solid can be obtained according to the weight of the sample in air, the weight of the sample in
liquid and the density of the liquid.
A
ρ
=
×
(
ρ
0
-
d)
+
d
A
-
B
ρ
: Density of sample (g/cm
3
)
A : Weight of sample in air (g)
B : Weight of sample in liquid (g)
ρ
0
: Density of liquid (g/cm
3
)
d
: Density of air (approx. 0.001 g/cm
3
)
3-5. Density Of A Liquid
The density of a liquid can be obtained according to the weight of float in air, the weight of float in liquid and the
known volume of float.
A
-
B
ρ
=
+
d
V
ρ
: Density of liquid (g/cm
3
)
A : Weight of float in air (g)
B : Weight of float in liquid (g)
V : Volume of float (cm
3
)
d
: Density of air (approx. 0.001 g/cm
3
)
