Methylene Blue Test (MBT) - Basic Mud School

Summary

This video demonstrates the methylene blue method for measuring the concentration of reactive clays, such as bentonite, in a mud sample. The process begins with preparing the sample by adding water, hydrogen peroxide, and sulfuric acid to digest organic compounds. After slow boiling and cooling, the sample is titrated with methylene blue. As the methylene blue is absorbed by the reactive clays, a greenish-blue halo forms, indicating saturation. The final amount of methylene blue used correlates to the concentration of clays, with the sample in this case containing 25 pounds per barrel of sodium montmorillonite.

Takeaways

• 😀 The methylene blue method is used to measure the concentration of reactive clays, such as bentonite, in a mud sample.
• 😀 A 10 mL sample of distilled or deionized water is first added to an Erlenmeyer flask.
• 😀 1 mL of the mud sample is then introduced into the flask using a pipette.
• 😀 15 mL of 3% hydrogen peroxide is added to oxidize organic compounds in the sample during the digestion process.
• 😀 Half a milliliter of 5N sulfuric acid is added to raise the pH and help in digestion.
• 😀 The mixture is heated to a slow boil for 10 minutes, and periodic stirring ensures uniform exposure to reagents.
• 😀 After boiling, the solution is cooled and filtered using a specially prepared filter paper.
• 😀 The titration process begins by adding half a CC of methylene blue to the solution.
• 😀 As methylene blue is added, the color intensity increases, and a greenish-blue halo forms when the reactive clays reach saturation.
• 😀 The final point of titration is reached when 5 CCs of methylene blue create a green halo, indicating saturation of reactive clays.
• 😀 The concentration of reactive clays is calculated by multiplying the milliequivalents of methylene blue used by the sample volume to determine the amount in pounds per barrel.

Q & A

What is the methylene blue method used for in this procedure?

The methylene blue method is used to measure the concentration of reactive clays in a sample, such as bentonite or smectite, by observing how much methylene blue is absorbed by the clays in the sample.

Why is hydrogen peroxide added during the digestion process?

Hydrogen peroxide is added to oxidize and break down organic compounds in the sample, such as lignite, ensuring that methylene blue only interacts with the reactive clays and not with organic materials.

What is the purpose of adding sulfuric acid to the mixture?

The sulfuric acid is added to raise the pH of the mixture, which helps in the digestion process and ensures that the methylene blue will absorb only into the reactive clays.

How long does the digestion process last, and why is it necessary?

The digestion process lasts for 10 minutes, during which the sample is slowly boiled to oxidize organic matter and ensure that only reactive clays interact with the methylene blue.

What is the significance of controlling the boiling temperature during the digestion?

The boiling temperature is carefully controlled to prevent the water from evaporating, ensuring that there is enough solution left for the titration and preventing the formation of a precipitate at the bottom of the flask.

Why is the solution stirred during the digestion process?

The solution is stirred to ensure that all phases of the mixture are exposed to the digesting additives (hydrogen peroxide and sulfuric acid) and that the reaction is homogeneous.

What is the purpose of adding distilled water after the digestion process?

Distilled water is added after digestion to dilute the solution and help cool it down to room temperature, preparing it for the next steps in the procedure.

How is the methylene blue titration carried out in this method?

Methylene blue is added incrementally to the sample, with each half-cc addition followed by stirring for 20 seconds. A green halo around the blue spot indicates the saturation of reactive clays with methylene blue.

What does the green halo indicate during the titration?

The green halo indicates that the reactive clays in the sample have reached their saturation point, meaning they can no longer absorb any more methylene blue.

How is the concentration of reactive clays calculated in this method?

The concentration is calculated based on the volume of methylene blue required to reach the saturation point, which is then multiplied by a factor to give the final concentration in pounds per barrel, in this case, 25 pounds per barrel of sodium montmorillonite (bentonite).