Best conditions to increase the
continuous flow of methyl
orange
also commonly used in the textile industry as
a dye product 3). The synthesis of methyl
orange is an exothermic 4-step reaction. The
two main reactions in the synthesis are:
-The nitrosonium ion reacts with the amino of
the sulfanilic acid, attaching a second N-atom
at the sulfanilic acid to produce a diazonium
salt (the process of diazotation):
Team member: Fazal Iqbal
School: Cygnus Gymnasium
Studentnumber:98295
Teamnumber:4
16 April 2012
Summary
Methyl orange is an extensively used product
in the textile industry as a dye product. It has
an intense coloring compound. Chemists use it
as an indicator in the titration of weak bases
with strong acids. Methyl orange is best
produced in a micro reactor where
temperature and flow rate can be controlled.
In my initial experiment a continuous flow of
0.0028 mol/L was achieved. With regard to its
production the following question raises in
our minds: What effect does the temperature
or flow rate have on the continuous flow of
methyl orange?
Methyl orange indicator
-The diazonium salt is coupled with N,Ndimethylaniline, the coupling takes place in
the opposite position from the – N(CH3)2
group:
There are certain conditions in the mechanism
that are needed for the synthesis of methyl
orange such as flow rate and temperature.
This raises the following question: what effect
does temperature or flow rate have on the
increase or decrease of the continuous flow of
methyl orange? Therefore I want to examine
what the effects will be on the methyl orange
production when I vary the temperature or
flow rate. My hypothesis on the inquiry
question is:
 Increase in the temperature will
increase the continuous flow of
methyl orange.
 Increase in the flow rate will increase
the continuous flow of methyl orange.
Introduction
My theoretical assumption is that:
Methyl orange is a pH indicator in the
chemistry. It is widely used in titrations
because one of the major characteristics of
methyl orange is that it changes color clearly
and distinctive. It changes from red (at pH 3.1)
to orange-yellow (at pH 4.4). However methyl
orange also has mutagenic properties, it is
Chemical reactions require collisions
between reactant molecules or atoms. At
higher temperatures collisions will be
more violent and the frequency of
collisions will increase 2). This means that
the chemical reactions will speed up. The
higher the flow rate the more the
molecules will spread over the time and
thereby increasing continuous flow of
methyl orange.
The product methyl orange is analyzed using
an Ocean Optics spectrometer.
Results
The graph with flow rates of 100 µL/min and
65°C is as follows:
Experimental design
Methyl orange can be best produced in a
micro reactor. This device consists of three
inlets and one outlet. Solution A is lead
through the first inlet. Solution A consists of
16.7 mmol sulfanilic acid, 16.7 mmol sodium
carbonate, 16.7 mmol sodium nitrate, 166.7
mL water and 83.4 mL ethanol. The flow rate
at which solution A is lead through inlet 1 is
100 µL/min.
Figure: schematic design of micro reactor
Solution B is lead through inlet 2 . Solution B
contains 3.16 mL N,N-dimethylaniniline, 6.3
mL mL 12 M HCl and 238.7 mL water. This
solution is flowed into the reactor with a rate
of 100 µL/min.
The graph with flow rates of 100 µL/min and
75°C is as follows:
Solution C is lead through inlet 3. This solution
contains 18.8 mmol NaOH, 62.5 mL water and
187.5 mL ethanol. The flow rate for solution C
is set at 100 µL/min. The temperature of the
micro reactor is set at 65°C. The same
experiment is repeated with the same set up
and flow rates but with a different
temperature of 75°C in the micro reactor. To
research the influence of the flow rates of the
three solutions on the flow rate of methyl
orange I chose to set the rates at 100 µL/min
and 125 µL/min at 75°C.
In this experiment the control variables are
the flow rate and temperature. The
independent variable is the time. The
dependent variable is the continuous flow of
methyl orange in mol/L.
The graph with the different flow rates of 125
µL/min and the same temperature of 75°C is
as follows:
With same circumstances but increase of the
temperature with 10° to 75° a continuous flow
of methyl orange was found of 0.0034 mol/L.
The concentration that is constantly produced
increases with 0.0006 mol/L to 0.0034 mol/L .
So at all an increase in the temperature
increases the evolvement of the reaction in
which methyl orange is produced so that the
yield of the methyl orange gets higher.
Thereby the first hypothesis could be
accepted.
As is notable increase in the flow rates of
the three solutions with 25 µl/sec and the
same temperature retained, decreases the
concentration of flow rate of methyl
orange that is reached. The main reason
could be that the reaction happens at a
quicker speed. The yield of methyl orange
is reached sooner but the concentration of
the methyl orange is a little bit lower. So
the second hypothesis wasn’t right at all.
We did each of these three experiments two
times and in the table you can see all the
results:
Experim
ent 1
Tempe
rature
65°
65°
Experim
ent 2
75°
75°
Experim
ent 3
75°
75°
Flow
rate
100
µl/sec
100
µl/sec
100
µl/sec
100
µl/sec
125
µl/sec
125
µl/sec
Concentration
Methyl Orange
0.0028 mol/L
0.0024 mol/L
0.0034 mol/L
0.0038 mol/L
0.0023 mol/L
0.0019 mol/L
Discussion and conclusion
From the results shown above there is an
important finding observed. First, at 65°C and
flow rates of 100 µL/min a continuous flow of
methyl orange was reached of 0.0028 mol/L.
Evaluation
The experimental set up could have been
improved by making more measurements.
This would have enhanced the reliability and
validity of the results. But there was not
enough time. In future it will be better to have
more time to extend the experiment. This way
more measurements can be done.
My suggestion for a future experiment will be
to have the following inquiry question. What
effect does the concentration of solution A, B
and C have on the continuous flow rate of
methyl orange?
Bibliography
1. Kijdna, A.ea. Synthesis of methyl
orange in a micro reactor
2. http://www.800mainstreet.com/7/00
07-005-rea-t-cat.html
3. http://antoine.frostburg.edu/chem/se
nese/101/acidbase/faq/methylorange.shtml
4. http://en.wikipedia.org/wiki/Methyl_
orange