Extracting Citric Acid From Lemons

Apoptosis

15 Jan 202303:52

Summary

TLDRThis video demonstrates a DIY method to extract citric acid from lemons. The process involves juicing lemons, neutralizing with sodium hydroxide to form sodium citrate, then precipitating with calcium chloride to form calcium citrate. After vacuum filtration, sulfuric acid is used to revert it to citric acid and gypsum. The final step involves vacuum drying and recrystallization for pure citric acid crystals.

Takeaways

🍋 **Juice Extraction**: The process starts by juicing lemons to obtain citric acid.
🧪 **Neutralization**: Sodium hydroxide is added to neutralize the excess acid in the lemon juice.
💧 **Filtering**: The solution is filtered to remove any lemon debris.
🔴 **pH Adjustment**: The pH is raised to 9 to convert citric acid into sodium citrate, indicated by a color change.
🌟 **Precipitation**: Calcium chloride is added to convert soluble sodium citrate into insoluble calcium citrate.
⏱️ **Settling Time**: The solution is left to allow calcium citrate to settle.
💦 **Vacuum Filtration**: Vacuum filtration is used to isolate calcium citrate, noting the requirement for a vacuum.
❄️ **Cold Water Rinse**: It's suggested to rinse the filtered calcium citrate with cold water for cleaner results.
🚮 **Discard the Filtrate**: The filtrate is discarded as it is not needed for further steps.
🔄 **Reformation**: Sulfuric acid is used to convert calcium citrate back into citric acid and gypsum.
🧊 **Freezing**: The solution is frozen to form citric acid crystals.
🌬️ **Final Purification**: The citric acid crystals are purified by recrystallization and vacuum filtration with ice-cold water.

Q & A

What is the first step in extracting citric acid from lemons?
-The first step is to slice up and juice a few lemons.
How much lemon juice is required to begin the process?
-The process begins with the juice of an unspecified number of lemons, which is then poured into a 1000 milliliter beaker.
What is the purpose of adding a sodium hydroxide solution to the lemon juice?
-A sodium hydroxide solution is added to neutralize the excess acid in the lemon juice.
What is the role of the coffee filter in the process?
-The coffee filter is used to remove any lemon debris from the solution after the sodium hydroxide has been added.
Why is the pH of the solution adjusted to 9?
-Adjusting the pH to 9 converts the citric acid from the lemons into sodium citrate, which is indicated by the solution's color shifting to a deep orange.
What is the function of adding calcium chloride solution to the mixture?
-The calcium chloride solution converts the soluble sodium citrate into insoluble calcium citrate.
Why is vacuum filtration used to isolate calcium citrate?
-Vacuum filtration is used to isolate calcium citrate because it allows for a more efficient separation of the solid from the solution.
What is the significance of rinsing the filtered calcium citrate with cold water?
-Rinsing with cold water is important to remove any remaining impurities and to make future steps cleaner.
How does the addition of a dilute sulfuric acid solution affect the calcium citrate?
-Adding a dilute sulfuric acid solution reacts with the calcium citrate to reform citric acid and precipitate white calcium sulfate, also known as gypsum.
Why is the filtered solution cooked down to 10 percent of its initial volume?
-Cooking down the solution to 10 percent of its initial volume helps to concentrate the citric acid, making it easier to form crystals.
What is the purpose of placing the resulting solution in the freezer?
-Placing the solution in the freezer allows the citric acid to crystallize, which can then be collected.
Why is recrystallization performed off-camera?
-Recrystallization is performed off-camera to keep the video short, and it helps to form larger, purer crystals of citric acid.
What is the final step in obtaining pure citric acid crystals?
-The final step is to dry the crystallized citric acid on a small filter, pulling a vacuum to rinse the crystals with ice-cold water.
What was the yield of citric acid from the process described in the script?
-The final yield of citric acid was larger than what was shown in the video, as the process was done in batches.

Outlines

00:00

🍋 Citric Acid Extraction Process

The script describes a process for extracting citric acid from lemons. It starts with juicing lemons and adding sodium hydroxide to neutralize the excess acid. The mixture is filtered to remove debris, and additional sodium hydroxide is added until the pH reaches 9, indicated by a color change to deep orange. This converts the citric acid to sodium citrate. A calcium chloride solution is then added to convert the sodium citrate into insoluble calcium citrate, which is allowed to settle. After vacuum filtration, the calcium citrate is treated with a dilute sulfuric acid solution to reform citric acid and precipitate calcium sulfate (gypsum). The citric acid solution is then concentrated and frozen to form crystals, which are purified through recrystallization and vacuum filtration with ice-cold water.

Mindmap

Keywords

💡Citric Acid

Citric acid is a weak organic acid that naturally occurs in citrus fruits, particularly lemons. It is used widely in food and beverages as a natural preservative and flavor enhancer. In the video, citric acid is the target compound to be extracted from lemons, highlighting its importance as the primary substance of interest.

💡Lemons

Lemons are citrus fruits known for their high citric acid content, which gives them their characteristic sour taste. They serve as the raw material in the video for extracting citric acid. The process begins with juicing lemons, which is the first step in isolating citric acid.

💡Sodium Hydroxide

Sodium hydroxide, also known as lye or caustic soda, is a strong base used in various chemical processes. In the video, it is added to the lemon juice to neutralize excess acid and facilitate the conversion of citric acid into sodium citrate, which is a key step in the extraction process.

💡pH

pH is a scale used to measure the acidity or alkalinity of a solution. A pH of 7 is neutral, values below 7 are acidic, and values above 7 are alkaline. In the video, the pH is adjusted to 9 to ensure that all citric acid is converted to sodium citrate, as indicated by a color change to deep orange.

💡Calcium Chloride

Calcium chloride is a salt of calcium that is used in the video to convert soluble sodium citrate into insoluble calcium citrate. This reaction is crucial as it allows for the precipitation of calcium citrate, which can then be isolated from the solution.

💡Vacuum Filtration

Vacuum filtration is a technique used to separate solids from liquids under reduced pressure, which speeds up the filtration process. In the video, it is used to isolate calcium citrate from the solution, demonstrating its utility in purifying chemical compounds.

💡Sulfuric Acid

Sulfuric acid is a strong mineral acid that is used in various industrial processes. In the video, a dilute solution of sulfuric acid is added to the calcium citrate to reform citric acid and precipitate calcium sulfate, which is a critical step in the purification of citric acid.

💡Gypsum

Gypsum, also known as calcium sulfate dihydrate, is a mineral that forms as a byproduct when sulfuric acid reacts with calcium citrate. In the video, gypsum is filtered out after the reaction with sulfuric acid, as it is not the desired product.

💡Recrystallization

Recrystallization is a process used to purify a substance by dissolving it in a solvent and then allowing it to crystallize again. In the video, recrystallization is mentioned as an off-camera step to form larger citric acid crystals, which is a common practice to improve the purity and size of crystals.

💡Yield

Yield in chemistry refers to the amount of product obtained from a reaction relative to the maximum amount that could theoretically be produced. The video mentions that the final yield of citric acid was larger than what was shown, indicating the efficiency of the extraction process.

Highlights

Extraction of citric acid from lemons begins with juicing them.

Juice is poured into a 1000 milliliter beaker.

10 sodium hydroxide solution is added to neutralize excess acid.

Solution is filtered through a coffee filter to remove lemon debris.

Additional sodium hydroxide is added until pH reaches nine.

Citric acid is converted to sodium citrate at pH 9.

Strong calcium chloride solution is added to form insoluble calcium citrate.

An hour is given for calcium citrate to settle out of solution.

Vacuum filtration is used to isolate calcium citrate.

A cold water rinse of filtered calcium citrate is recommended for cleaner results.

Filtered calcium citrate is transferred to a fresh beaker.

A dilute sulfuric acid solution is used to reform citric acid and precipitate calcium sulfate.

Calcium sulfate, also known as gypsum, is formed.

Filtered solution is kept, and gypsum is discarded.

Solution is reduced to 10 percent of its initial volume.

Citric acid crystals are formed by freezing the solution.

Crystallized citric acid is rinsed with ice cold water.

Recrystallization is done to form larger citric acid crystals.

Highly pure, disc-shaped citric acid is the final product.

The final yield of citric acid is larger than shown due to batch processing.