How to Prepare Potassium Cyanide

Summary

This educational video demonstrates the synthesis of potassium cyanide, a highly toxic compound, for a future blueprint project. It cautions against home experimentation and details the chemical process involving charcoal, urea, and potassium hydroxide. The video explains the precautions taken, the chemical reactions involved, and the final steps to obtain potassium cyanide powder, despite a low yield due to the method of dissolution.

Takeaways

• 🚫 The video provides a strict warning against attempting the synthesis of potassium cyanide at home due to its extreme toxicity.
• 🔬 The process requires specific chemicals: charcoal, urea, and potassium hydroxide, with the latter being demonstrated in a previous video.
• 🌡️ The synthesis involves heating the mixture to temperatures around 160°C and then up to 600°C to ensure a complete reaction.
• 🔥 The reaction involves the decomposition of urea and the formation of tripotassium cyanurate, which is then reduced to potassium cyanide.
• 🌿 An excess of potassium hydroxide and charcoal is used to ensure complete reaction and reduction of cyanate to cyanide.
• 🧪 The presence of cyanide ions is confirmed by the formation of Prussian blue pigment when the methanol solution is added to a solution containing iron II and iron III ions.
• ⚠️ Extreme caution is advised when handling the mixture due to the presence of highly toxic cyanide.
• 🧴 Methanol is used to dissolve the potassium cyanide, and the solution is left to dissolve overnight before being filtered.
• 🧪 Sodium bicarbonate is added to the methanol solution to neutralize any residual potassium hydroxide, avoiding the formation of dangerous hydrogen cyanide gas.
• 🌀 The use of a Soxhlet extractor is suggested for future projects to improve the recovery of cyanide from the reaction products.
• 📊 The video concludes with a yield of 3.08g of potassium cyanide, which is a 12.3% yield based on the starting urea, and notes the potential for improved yields with different methods.

Q & A

What is the purpose of preparing potassium cyanide in the video?

The purpose of preparing potassium cyanide is to produce potassium ferricyanide for making blueprints in a future project.

What warning does the video give about handling potassium cyanide?

The video warns that cyanide compounds are extremely deadly and as little as a third of a gram of potassium cyanide can kill a person in a few minutes, stressing not to attempt this at home.

What are the initial materials needed to start the synthesis of potassium cyanide?

The initial materials needed are charcoal, urea, and potassium hydroxide. Sodium hydroxide can be substituted if sodium cyanide is desired.

How is urea obtained according to the video?

Urea can be obtained from fertilizer or found in some instant cold packs.

What happens when the mixture of potassium hydroxide, urea, and charcoal is heated?

Upon heating, urea decomposes to isocyanic acid and ammonia, which is toxic and requires the process to be performed outside. Isocyanic acid then reacts with potassium hydroxide to produce tripotassium cyanurate and water.

Why is it necessary to heat the mixture to around 600C?

The mixture is heated to around 600C to ensure a complete reaction occurs, breaking tripotassium cyanurate into potassium cyanurate, which is then reduced by carbon to form potassium cyanide.

What is the role of methanol in processing the cyanide?

Methanol is used to dissolve the potassium cyanide. The can containing the reaction mixture is filled with methanol, and the solution is left to dissolve overnight.

How is the presence of cyanide ions confirmed in the methanol solution?

The presence of cyanide ions is confirmed by adding a few drops of the methanol solution to a solution containing iron II and iron III ions, resulting in the immediate formation of Prussian blue pigment.

Why is sodium bicarbonate used to destroy residual potassium hydroxide in the methanol solution?

Sodium bicarbonate is used to destroy residual potassium hydroxide because it forms sodium and potassium carbonate, which is insoluble in methanol and precipitates out. Using an acid is not recommended as it would react with potassium cyanide to form dangerous hydrogen cyanide gas.

What is the final step to obtain potassium cyanide powder?

The final step is to evaporate the methanol from the solution in a dish over a day to yield potassium cyanide powder.

What was the yield of potassium cyanide obtained in the video?

The yield of potassium cyanide obtained was 3.08g, which corresponds to a 12.3% yield based on the starting urea.

What could be a reason for the poor yield mentioned in the video?

The poor yield is likely because the reaction products were not broken into a powder prior to dissolution in methanol, which could have affected the efficiency of the extraction process.

What alternative method is suggested for better recovery of cyanide in the future?

The video suggests using a Soxhlet extractor to cycle solvent over the reaction products as an alternative method for better recovery of cyanide.