what is density, specific gravity and API ? how to measure density, specific gravity and API gravity? what is advantages of API gravity? using hydrometer and pycnometer for measuring density and specific gravity What are factor effecting on the hydrometer?

1. UNIVERSITY OF ZAKHO
Faculty of Engineering
School of Petroleum Engineering
Practical Petroleum Properties Lab.
2nd
Year Level
Name of student : Bilal Mohammed Taha
Class: A
Name of Experiment: Measurement of Density, S.G, and API gravity for
petroleum fraction.
No. of Experiment: 2
Date: 13/12/2015

2. Experiment No. -2-
Measurement of Density, Specific Gravity, and API Gravity
Objective:
Determination of Specific Gravity, and API Gravity for petroleum products
Introduction:
Determining the density, specific gravity and API gravity of the fliud is very
important to classify the fuil. This experiment will shows us how to determine API
and S.G via two method.
Density is mass per unit volume or Density is a characteristic property of a
substance. The density of a substance is the relationship between the mass of the
substance and how much space it takes up (volume).
Specific gravity the ratio of the density of any substance to the density of some
other substance taken as standard, water being the standard for liquids and solids,
and hydrogen.
API gravity is used to quantify the quality of petroleum priducts and it has ranges
that measures the quality. And it depends on specific gravity , the higher S.G the
lower API gravity.
Apparatus and material:
ü Hydrometer:
ü Pyconmeter:
ü Graduated cylinder:
ü Scientific balance:

3. Procedure:
Hydrometer method:
At first we take a suitable graduated cylinder 500 ml and it should be clean. The
cylinder should be big enough because when we put the hygrometer it should
(move) floats easily in the cylinder.
So, we fill the cylinder with the sample (in our experiment we just used diesel for
this method). After filling the cylinder with the diesel we allowed sufficient time
for the hydro meter to come to rest. And when the hydrometer is flowed freely we
took the scale reading. And at the end we brought out the hydrometer and cleaned
it.
Pycnometer method:
At first we took the emptied pyconmeter and weigh it (M1). Then we filled the
pyconmeter with the sample that we wanted and weigh it again (M2). (To yield the
weight of the sample we subtract M2 from M1.)
The volume of the pyconmeter that we used for kerosene was 5.305 ml and for
diesel was 4.928ml.
After those steps we measure the the density of fluid and API gravity and Specific
Gravity according to what we did in the lab.
API gravity = 141.5/S.G(at 15.6 °C) – 131.5
Note:
Ø API gravity > 40 paraffinic (or light) based crude oil
Ø API gravity = 33-40 mixed (or intermediate) based crude oil
Ø API gravity < 33 napthenic ( asphaltic or heavy)based crude oil

4. Calculations:
Hydrometer method
The specific gravity of diesel is 0.832
API gravity =
.
.
- 131.5 èAPI gravity =
.
.
– 131.5 = 38.572
(we didn’t measured the S.G of kerosene by hydrometer)
Pycnometer method
Kerosene
M1 of empty pycnometer = 14.723 g
M2 of filled pycnometer = 18.882 g
Volume of pycnometer = 5.305 ml
M= M2-M1 =èM= 18.882- 14.723= 4.159g
k= =
.
.
= 0.784
S.G =
k
w
=
.
= 0.784
API gravity =
.
.
- 131.5
=
.
.
- 131.5 = 48.8

5. Deisel
M1 of empty pycnometer = 15.295 g
M2 of filled pycnometer = 19.357 g
Volume of pycnometer = 4.928 ml
M= M2-M1 =èM= 19.357- 15.295= 4.062g
d= =
4.062
4.928
= 0.82427
S.G =
d
w
=
.
= 0.82427
API gravity =
.
.
- 131.5
=
.
.
- 131.5 = 40.167
We can classify them according to the ranges of API, that have been wrote after procedure
Discussion:
In the lab we we measured the API and S.G of kerosene and Diesel . we measured
the API of diesel by hydrometer and pycnometer(but we didn’t measured the S.G
of kerosene via Hydrometer ), on hydrometer method the API value of diesel
sample was 38.57 but in pycnometer method API was 40.167. The pycnometer
method is more accurate because hydrometer is affected by many things that
makes reading not accurate
1- Explain which method is much accurate?
Method two (pycnometer is more accurate than the hydrometer and the
reasons belongs to those factors that affect the hydrometer like temperature,
carbon dioxide, and presence of alcohol..

6. 2- What are factor effecting on the hydrometer?
The factors that effects the hydrometer are:
Ø temperature that causes the change in density
Ø carbon dioxide
Ø presence of alcohol
3- What are the advantages of API value?
The more API gravity value of crude oil is more expensive and more effectual
because its contain more gasoline and it is the most wanted product at the whole
world. The other advantage of API gravity value that we can determine the sulphur
contain in crude oil , the higher value if API gravity means the less contain of
sulfur , the high levels of sulfur contains can be toxic and dangerous and can cause
breathing hazards .
References:
www.wikipedia.org
http://whatis.techtarget.com
http://study.com