1. The document describes an experiment to determine the density and API gravity of kerosin and gas oil samples using two methods: a hydrometer and a pycnometer. 2. The results found the API gravity of kerosin to be 48.53 using the hydrometer method but 35.56 using the pycnometer method, showing a difference between the methods. 3. The pycnometer method is considered more accurate as it is less affected by factors like temperature, bubbles, and alcohol content that influence the hydrometer readings.

1. 1
Experiment NO.1
Density and relative density
Name: Yasir Ammar Ahmed
Department of Petroleum
Engineering
Class – 2 –
2nd Year

2. 2
Contents :
Introduction --------------- Page 3
The Objectives --------------Page 4
Materials and Instruments --------------Page 4
Procedure ----------------Page 6
Calculations and Results -------------Page 8
Discussion ------------ Page 11
Theory ------------------ Page 13
Conclusion -------------Page 13

3. 3
Introduction
The purpose of this experiment is to understand the meaning
and significance of the density of a substance. Density is a basic
physical property of a homogeneous substance; it is an
intensive property, which means it depends only on the
substance's composition and does not vary with size or
amount. The determination of density is a nondestructive
physical process for distinguishing one substance from another.
Density is the ratio of a substance's mass to its own volume.
𝜌 =
𝑚𝑎𝑠𝑠
𝑣𝑜𝑙𝑢𝑚𝑒
=
𝑣
𝑚
In the metric system the unit of density for a liquid or solid is
measured in g/mL or g/cm3.l
By determining the density of matter and in our case we will
take the density of (kerosin and Gas oil ) we can calculate the
API (American Petroleum Institute) by the equation :
API K =
141.5
𝑅𝐷
− 131.5
Where (RD) is the relative density of the matter and we can
find it by dividing the density of matter to the density of water ,
API gravity, is a measure of how heavy or light
a petroleum liquid is compared to water: if its API gravity is
greater than 10, it is lighter and floats on water; if less than 10,
it is heavier and sinks.

4. 4
The Objectives :
The objectives of this experiment is :
1. To learn how to determine the density of sample.
2. To learn how to determine the relative density of sample.
3. To learn how to use the hydrometer and pycnometer and
how to take dimensions of them.
4. To learn how to calculate the API gravity by relative
density.
5. To distinguish between the different density samples.
Materials and Instrument
The Materials that we have used in the experiment are :
1. Graduated cylinder(500mL): is a piece of laboratory
equipment used to measure the volume of a liquid,the
inside diameter of the cylinder shall be at least 25mm
greater than the outside diameter of the hydrometer and
the height shall be such that the appropriate hydrometer
floats in the test portion with at least 25mm clearance
between the bottom if the hydrometer and the bottom of
the cylinder.(fig1)
2. Pycnometer(50mL) : A pcynometer or specific gravity
bottle is a flask with a stopper that has a capillary tube
through it, which allows air bubbles to escape. The
pycnometer is used to obtain accurate measurements of
density.(fig2)

5. 5
3. Hydrometer ( 0.7 – 0.8) and (0.8 – 0.9) : is an instrument
used to measure the specific gravity (or relative density)
of liquids; that is, the ratio of the density of the liquid to
the density of water.(fig3)
4. Two samples of (Kerosin) and (Gas Oil)
5. Scientific Balance : Used for determining the weight or
mass of a sample.(fig4)
Fig1 Fig2
Fig3 Fig4

6. 6
Procedure:
In our experiment we have not adjust the temperature of the
sample (Just for this time because it was the first lab &Exp.)
Method 1 : Hydrometer
1. First take a clean and dry graduated cylinder 500mL ,the
inside diameter of the cylinder shall be at least 25mm
greater than the outside diameter of the hydrometer and
the height shall be such that the appropriate hydrometer
floats in the test portion with at least 25mm clearance
between the bottom if the hydrometer and the bottom of
the cylinder.
2. Fill the graduated cylinder with the test portion (in our
case they were Kerosin & Gas oil ), we fill it with only one
test portion till it reach the 500mL dimension.
3. Now lower the appropriate hydrometer into the liquid
and release when in a position of equilibrium.
4. Allow sufficient time for the hydrometer to come to rest.
5. When the hydrometer is flow freely take the scale reading
where the principle surface of the liquid cuts the scale by
placing the eye slightly below the level of liquid and
slowly go up till you read the scale at the liquid sureface.
6. When you record the reading immediately lift the
hydrometer and clean it.
7. Now we got the relative density (specific gravity ) value ,
by applying it at the API gravity formula we get the API
gravity value , and that's our goal of this experiment.
API =
141.5
𝑅𝐷
− 131.5

7. 7
Method 2 : Pycnometer
1. First take a clean and dry Pycnometer 50mL and weigh
it by using scientific balance.
2. Record the weight of empty , dry and clean
pycnometer and after recording the weight lift it.
3. Fill the pycnometer fully with the test portion (the
sample) , and after that weigh it again by using the
balance.
4. Record the weight of fully filled pycnometer with test
portion(the sample).
5. By the records of weights of empty and fully saturated
pycnometer we can calculate the weight of the test
portion(the sample) , and by dividing it on the volume
of the pycnometer we will get the Density of the test
portion(the sample).
6. Now take the room temperature and record it.
7. By the room temperature we can determine the
density of water from the table below(Table 1).
8. Now we have the density of the sample and the
density of water , by applying the relative density (
specific gravity ) formula we can get the relative
density ( specific gravity) value.
9. Now we have the relative density (specific gravity )
value , by applying it at the API gravity formula we get
the API gravity value of the sample , and that's our goal
of this experiment.
API gravity =
141.5
𝑅𝐷
− 131.5

8. 8
Calculation and Result
Method 1 : Hydrometer
Givens :
RD = SGk = 0.786
RD = SGD = 0.827
Required: API of Kerosin(K)
API of Gas Oil(D)
Solution :
API K =
141.5
𝑅𝐷
− 131.5
=
141.5
0.786
− 131.5 = 180.03 − 131.5
= 48.53
API D =
141.5
𝑅𝐷
− 131.5
=
141.5
0.827
− 131.5 = 171.10 – 131.5
=39.60

9. 9
Method 2 : Pycnometer
Givens : For kersoen
Volume of Pycnometer = 50 mL
M0 = 19.2 g M1 = 61.5 g T = 21.5oC
Requireds :
SG K = ? API K = ?
Solution :
SG K =
𝜌 𝑘
𝜌 𝑤
𝜌𝑘
=
𝑀 𝑘
𝑉
→ Mk = M1 - M2 = 61.5 g – 19.2 g = 42.3 g
𝜌𝑘
=
42.3 𝑔
50 𝑚𝐿
= 0.846 g/mL
While T = 21.5oC So 𝜌 𝑤 = 0.9978845 g/mL
SG K =
0.846 𝑔/𝑚𝐿
0.9978845 g/mL
= 0.847
API K =
141.5
0.847
− 131.5 = 167.06 − 131.5 = 35.56

10. 10
Givens : For Gas Oil
Volume of Pycnometer = 50 mL
M0 = 18 g M1 = 60 g T = 21.5oC
Required :
SG D = ? API D= ?
Solution :
SG D =
𝜌 𝐷
𝜌 𝑤
𝜌𝐷
=
𝑀 𝐷
𝑉
→ MD = M1 - M2 = 60 g – 18 g = 42 g
𝜌𝐷
=
42 𝑔
50 𝑚𝐿
= 0.840 g/mL
While T = 21.5oC So 𝜌 𝑤 = 0.9978845 g/mL
SG D =
0.840 𝑔/𝑚𝐿
0.9978845 g/mL
= 0.842
API D =
141.5
0.842
− 131.5 = 168.05 − 131.5 = 36.55
Note : How I Got the Temperature at 21.5 while it is not included at the Table
I did this calculation
The 𝜌 𝑤 at 21o
C = 0.997991 and 𝜌 𝑤 at 22o
C = 0.997769
𝜌 𝑤=(0.997991+ 0.997769) / 2 = 0.9978845

11. 11
Discussion
In this experiment , there are a lot of questions we should know
there answers , first of all is our results that we got
After calculations and got the results of the both methods
(Hydrometer & Pycnometer) we can see the different in API
results that we got it , in the first method we got API gravity of
Kerosin equal (48.53) while in the second method equal(35.56
) as you see there is a high range between the two methods ,
and here the question is , which method is much accurate ?
My answer is , the method 2 is more accurate than the method
1 , the reason belongs to that the hydrometer method is
affected by many factors that can make the reading not
accurate , the factors are :
1. Temperature : Temperature has an effect on the
hydrometer reading , because when the temperature is
increase the density of the sample will decrease and then
the reading of hydrometer will be not accurate, and cause
the hydrometer float slightly low , so when we use the
hydrometer it should be at fixed temperature , at 60oF .
2. carbon dioxide bubbles : produced by yeast rise and
dissipate into the air above. Early in fermentation when
the must is visibly bubbling, the bubbles will attach
themselves to the hydrometer and cause it to float
higher, increasing the reading slightly.
3. Presence of Alcohol : Alcohol is less dense than water and
thus makes a hydrometer float a little lower.

12. 12
4. Other errors should taking the read from non-parallel site
to the eye , that could make the calculations and results
not accurate.
So after all that factors affecting on the result of hydrometer
, we see that the results are not accurate with method 1 .
Method 2 is more accurate than method 1 , and the wrong
or error percentage is less than method 1 , in method 2 we
take the mass of the liquid , which is constant and also the
volume of pycnometer is constant , if we do the experiment
at fixed temperature we will get accurate results about
density therefore accurate results about API gravity .
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 , because all
people are looking for gasoline to operate their machines ,
so the more API gravity value contain more gasoline and
that's what we looking for .
only about less percentage of crude oil can be transfer to
gasoline , only 5-6 % of Tawke crude oil at (Kashi mini
Refinery ) can be transferred to gasoline.
The other advantage of API gravity value that we can
determine the sulfur 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 .

13. 13
Theory
When greater accuracy is required or when only small
quantities are available, liquid densities are best obtained from
the mass required to fill a vessel of accurately defined volume,
e.g., a specific gravity bottle(p.217) or a pycnometer. With
careful technique, the densities measured with pycnometers
are precise to five significant figures. For not too viscous liquids
available in sufficient amounts, density is more conveniently
determined by buoyancy devices namely Westphal balance or a
Hydrometer. These devices are based on Archimedes principle
according to which the buoyant effect(the upthrust acting on
an object immersed in a liquid) is directly proportional to the
weight of the liquid displaced.
Conclusion
In this Experiment we learn how to measure the density of
sample and how to calculate the API gravity by density , and
the other thing is how to use the hydrometer and
pyconmeter to determine the density of samples , and we
learn what does the API gravity different values mean , and
the error s sources that can make the measurements not
accurate.