How to make 0.1% Methyl Orange pH Indicator

Methyl orange is an indicator commonly used in chemistry laboratories to determine whether the solution is acidic or basic. It particularly comes in handy in titrations to establish endpoint of reactions between strong acids and weak bases. Preparation of a 0.1% Methyl orange solution is relatively easy but requires proper weighing mixing.

This guide will take you through the step-by-step preparation of a 0.1% Methyl Orange pH indicator, the materials needed and the possible purity adjustments required to achieve a good pH indicator.

What is Methyl Orange?

Methyl orange is an organic pigment that is used as a pH detector and the color of the pigment depends on the acidity or alkalinity of a given solution.

The pH indicator changes color depending on the pH of the solution.

 Examples:

When the pH Indicator is added to the Hydrochloric acid (Strong acid) – the solution turns red. In neutral solution like water appears orange/yellow while in basic solution like Sodium hydroxide the solution becomes yellow.

Materials Required

1. Methyl Orange powder – 85% purity
2. Distilled water
3. Analytical or digital weighing balance
4. Conical flask
5. Measuring cylinder
6. Volumetric flask

Understand Concentration

A 0.1% (w/v) solution means:

0.1  g of solute dissolved in 100 ml of solvent.

In my case, I’m going to prepare 100ml of the solution. Therefore, to prepare 100 ml of 0.1% methyl orange solution:

• Methyl orange = 0.1 g`
• Distilled water = 100 ml

But our dye is 85% pure. In this case we will need to adjust for purity.

Calculation

Since purity is 85% Let’s find the mass of the powder needed

Weight required = Required pure dye/ Purity

Where purity = 85% = 0.85g of the powder

0.85x = 0.1g

X= 0.1/0.85 = 0.118g

Therefore, you need 0.118g of the Methyl Orange powder to perform the procedure.

Procedure

1. Weigh 0.118 g of Methyl Orange powder (85% purity) using the Analytical balance
2. Place the measured powder into a conical flask
3. Using the volumetric flask, measure 75 ml of distilled water
4. Add the 75 ml distilled water into the conical flask
5. Mix Gently
6. Measure 25 ml of the distilled water using the volumetric flask
7. Top up the 25 ml of the distilled water and mix the solution well to achieve a consistent solution

Conclusion

Preparation of the Methyl Orange is important in the lab as the indicator is used in many areas to define the acidity or the alkalinity of a solution. When added to certain solutions, the indicator changes the colour of the suggesting a certain Ph.

It is essential to be careful when preparing the indicator in order to achieve the best final outcome when doing the tests in the laboratory. We have a tutorial on how to prepare the Methyl Orange pH Indicator in the laboratory and understand the correct procedure. Watch the tutorial now to learn the full preparation process step by step!