Sulaimani polytechnic university college of engineering petroleum and energy department

1. Technical College Of Engineering
Petroleum and Energy Engineering Department
Chemistry Laboratory
1st
stage
(2016-2017)
Lab # 1(Density and Specific Gravity)
(Density determination of liquids by using hydrometer)
Prepare By:Zanyar nawzad hama ali
Date : 19/2/2017
Group : B

2. INTRODUCTION
Accurate determination of the density or specific gravity of petroleum
and its products forthe conversion of measure volumes at the standard
temperature of, 15°C , 20°C or 25°C and also volume to mass and vice
versa. The hydrometer method is most suitable method for determining
the density or relative density (specific gravity) of mobile transparent
liquids. It can also be used for viscous oils by allowing sufficient time for
the hydrometer to reach equilibrium or for opaque oils by employing a
suitable meniscus correction. Hydrometer readings are obtained at
convenient temperatures, reading of density being reduced to 15°C or
20°C.
The aim of this experiment
The objective of this exp. is to measure and study density and specific
gravity of different liquids by using hydrometer., it will provide sufficient
information about light and heavy crude oils.

3. Theory
Hydrometer: is considered the simplest and the fastest method in
determination of density and specific gravity of a liquid.
The operation of the hydrometer is based on the Archimedes
principle that a solid suspended in a fluid will be buoyed up by a force
equal to the weight of the fluid displaced. Thus, the lighter the liquid
(that is, the less its specific gravity), the deeper the body sinks
because a greater amountof liquid is required to equal the body's
weight.
A hydrometer is usually made of glass and consists of a cylindrical
stem and a bulb weighted with mercury or lead shotto make it float
upright.
The liquid to be tested is emptied into a tall container, often a
graduated cylinder. The hydrometer is gently lowered into the liquid
until it floats freely.
The point at which the surfaceof the liquid touches the stem of the
hydrometer is noted.
Hydrometers usually contain a scale inside the stem, so that the
specific gravity can be read directly.

4. Density of a liquid: is its mass per unit volume at a given temperature
𝝆 =
𝑴
𝑽
( kg/m3, g/cm3 , Ibs/ft3)
Specific gravity of liquid (Sp. gr.): is the ratio of density of a
substance(Liquid) compared to the density of fresh water.
𝑺𝒑. 𝒈𝒓 =
𝝆 𝒔𝒖𝒃𝒔𝒕𝒂𝒏𝒄𝒆
𝝆 𝒘𝒂𝒕𝒆𝒓
For liquid petroleum fractions and crude oils, densities of both oil and
water are expressed at the standard condition (Temp. =15.6
o
C and Pre. =
1 atm), and they are usually indicated as SG at 15.6
o
C.

5. Tools
liquid(Sample).1
Thermometer.2
3. Graduatedcylinder (bottle)
4- Hydrometer

6. Experimental producer:
1. Fill the cylinder with the test liquid
2. Read the temperature of the liquid by the thermometer T
actual
3. Down the hydrometer into the sample slowly and carefully
4. Keep the hydrometer floating in center of the cylinder and from the
wall.
5.After stabilization of the hydrometer, note the point where the
surface of the liquid touches the stem

7. Calculation:
Temperature = 21°C actual
Sp.gr water= 15.6
Sp.gr naphtha = 0.695
Specific gravity at 15.6ºC = Sp. Gr. at (Ta) ± α ΔT
∆T = 21 – 15.6 = 5.4
α = 0.00048forNaphthalene
α × ∆T = 0.002592
sp = sp naphtha +or - α∆t
0.695+ 0.002592 = 0.697592
Sp =
𝑫 𝒏𝒂𝒑𝒉𝒕𝒉𝒂
𝑫 𝒘𝒂𝒕𝒆𝒓
D naphtha = sp naphtha × D water
0.698 × 0.999 = 0.697g/cm3

8. Discussion:
1- Hydrometer: is considered the simplest and the fastest method
in determination of density and specific gravity of a liquid.
2- Relative Density vs Density
Density and relative density are two closely related physical
properties of matter. Both parameters describe the amount of
matter in a unit volume. These terms are mostly used in fluid
statistics/dynamics and chemistry.
3- The difference between density and specific gravity is that
specific gravity is an expression of density in relation to the
density of a standard or reference (usually water). Also, density
has units, while specific gravity is a pure number or
dimensionless. Both density and specific gravity describe mass
and may be used to compare different substances.
4- If when used the better cylinder we can getbetter result
5- It is less dense than water, so it floats on top.
6- A study of the effect of increase in temperature on the specific
gravity of beawers worts has been made with special reference
to instrumentation in a continues brewery .
7- Yes we can use various liquid to this test.