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.

Outlines

00:00

🧪 Synthesis of Potassium Cyanide for Blueprints

This paragraph introduces a video on the synthesis of potassium cyanide, which will be used to produce potassium ferricyanide for blueprints in a future project. The video warns of the extreme toxicity of cyanide compounds and emphasizes that it should not be attempted at home. The synthesis requires charcoal, urea, and potassium hydroxide, with an alternative of sodium hydroxide for sodium cyanide. The process involves heating these substances to produce tripotassium cyanurate, which is then reduced to potassium cyanide. The video also mentions the use of methanol for processing the cyanide and a test for cyanide ions using iron II and iron III ions to confirm the presence of cyanide.

Keywords

💡Potassium cyanide

Potassium cyanide is a highly toxic chemical compound with the formula KCN. In the script, it is prepared for the purpose of producing potassium ferricyanide, which is used in the creation of blueprints. The video emphasizes the extreme toxicity of this compound, warning viewers that as little as a third of a gram can be lethal. This serves as a critical safety message within the educational context of the video.

💡Blueprints

Blueprints are a type of reproduction of a technical drawing, historically used in architecture and engineering. In the video, the motivation for synthesizing potassium cyanide is to produce potassium ferricyanide, which is a key component in the creation of blueprints. This keyword ties into the practical application of the chemical process described.

💡Urea

Urea is an organic compound that is a key intermediate in the industrial synthesis of several chemical products. In the script, urea is sourced from fertilizer and is used as a starting material in the synthesis of potassium cyanide. It decomposes upon heating to form isocyanic acid, which is a crucial step in the process.

💡Potassium hydroxide

Potassium hydroxide is a strong base with the chemical formula KOH. It is used in the script to react with isocyanic acid, derived from urea, to form tripotassium cyanurate. The script also mentions that sodium hydroxide can be used as a substitute if sodium cyanide is desired, highlighting the versatility in chemical reactions.

💡Decomposition

Decomposition in chemistry refers to a chemical reaction where a compound breaks down into simpler substances. In the context of the video, urea decomposes to isocyanic acid and ammonia when heated, which is an essential step in the synthesis of potassium cyanide.

💡Isocyanic acid

Isocyanic acid is an unstable intermediate compound formed during the decomposition of urea. It reacts with potassium hydroxide to form tripotassium cyanurate, which is a precursor to potassium cyanide. The script explains this as a part of the chemical process, illustrating the transformation of starting materials into the desired product.

💡Tripotassium cyanurate

Tripotassium cyanurate is a compound formed when isocyanic acid reacts with potassium hydroxide. It is a key intermediate in the synthesis of potassium cyanide, as described in the script. The video details how further heating of tripotassium cyanurate leads to the formation of potassium cyanide.

💡Reduction

Reduction in chemistry is a process where a substance gains electrons, often involving the addition of hydrogen or the removal of oxygen. In the script, the reduction of potassium cyanurate by carbon is described, leading to the formation of potassium cyanide, which is the end product of the synthesis.

💡Methanol

Methanol, also known as methyl hydrate, is an organic compound used as a solvent. In the video, methanol is used to dissolve the reaction products and extract the potassium cyanide. The script describes the use of methanol to facilitate the separation and purification of the desired chemical compound.

💡Prussian blue pigment

Prussian blue is a pigment formed when iron(II) and iron(III) ions react with cyanide ions. In the script, the formation of Prussian blue is used as a test to confirm the presence of cyanide ions in the solution, serving as a visual and chemical indicator of the success of the synthesis process.

💡Sodium bicarbonate

Sodium bicarbonate, commonly known as baking soda, is used in the script to neutralize residual potassium hydroxide in the methanol solution. This step is crucial for safety, as the script warns against using acids which could react with potassium cyanide to produce toxic hydrogen cyanide gas.

💡Soxhlet extractor

A Soxhlet extractor is a piece of laboratory equipment used for the extraction of a solid using a solvent. The script mentions the potential use of a Soxhlet extractor to improve the recovery of cyanide in a future process, indicating a method for optimizing the chemical synthesis.

Highlights

Introduction to the educational video on preparing potassium cyanide for a future blueprint project.

Warning about the extreme deadliness of cyanide compounds and the video's educational intent only.

List of required materials: charcoal, urea, and potassium hydroxide, with a note on sodium hydroxide substitution.

Mention of a previous video demonstrating potassium hydroxide preparation and sourcing urea from fertilizer or cold packs.

Detailed quantities of materials used: 25g potassium hydroxide, 23.3g urea, and 10g charcoal.

Description of the blending and heating process to initiate the chemical reaction.

Explanation of the chemical decomposition of urea and the formation of isocyanic acid and ammonia.

Safety note on performing the reaction outdoors due to toxic ammonia gas.

Chemical process of isocyanic acid reacting with potassium hydroxide to form tripotassium cyanurate.

Further heating to break down tripotassium cyanurate into potassium cyanide.

Use of a stoichiometric excess of potassium hydroxide and charcoal to ensure complete reactions.

Observation of the reaction until cessation of bubbling and subsequent cooling.

Caution regarding the highly toxic nature of the resulting cyanide mixture.

Processing of the cyanide with methanol and the use of a plastic tote for safety.

Confirmation of cyanide presence through the formation of Prussian blue pigment with iron II and III ions.

Neutralization of residual potassium hydroxide with sodium bicarbonate to avoid dangerous hydrogen cyanide gas.

Gravity filtration to remove insoluble impurities from the solution.

Evaporation of methanol to obtain potassium cyanide powder and yield calculation based on starting urea.

Reflection on the yield and consideration of using a Soxhlet extractor for better cyanide recovery in the future.

Conclusion and sign-off for the video, with an invitation to future projects.

Transcripts

Hey guys, and welcome back to another video.  Today we will be preparing some potassium cyanide,  

which will be used to produce potassium  ferricyanide for making blueprints in a  

future project. As a quick warning, cyanide  compounds are extremely deadly, and as  

little as a third of a gram of potassium  cyanide will kill you in a few minutes.  

Do not attempt this at home. This video  is strictly for educational purposes.

To start the synthesis, we will  only need some charcoal, urea,  

and potassium hydroxide. Sodium hydroxide can  be substituted if sodium cyanide is the desired  

product. I demonstrate how to prepare  potassium hydroxide in a previous video,  

and the urea was obtained from fertilizer. It  can also be found in some instant cold packs.

25g of potassium hydroxide, 23.3g of urea,  and 10g of charcoal were ground in a blender  

and added to a steel can and placed on a  stove. As the mixture is heated and reacts,  

first the urea decomposes to isocyanic acid and  ammonia around 160C. Ammonia gas is toxic, so this  

step must be preformed outside. The isocyanic acid  then reacts with potassium hydroxide to produce  

tripotassium cyanurate, and water. Further  heating breaks the tripotassium cyanurate  

into potassium cyanurate, which then is reduced  by carbon to form the final potassium cyanide.

The mixture was heated to around 600C to ensure  a complete reaction occurred. As a side note,  

a stoichiometric excess of potassium  hydroxide was used as the carbon dioxide  

produced will react with some of the potassium  hydroxide to produce potassium carbonate. An  

excess of charcoal was also used to ensure the  cyanate is completely reduced to the cyanide.

The reaction was run until all bubbling ceased,  and then it was allowed to cool. At this point,  

the mixture contains highly toxic cyanide, so  extreme caution must be used. The remaining  

chemistry was preformed in a plastic tote incase  of spills. To start processing the cyanide,  

the can was filled completely with methanol.  Methanol can be purchased as methyl hydrate from  

hardware stores. The beaker was left overnight so  everything could dissolve, and then the material  

was carefully transferred into a 1L beaker.  To check for the presence of cyanide ions,  

a few drops of the methanol solution can be added  to a solution containing iron II and iron III  

ions. Prussian blue pigment was immediately  formed, confirming the presence of cyanide.

To destroy residual potassium  hydroxide in the methanol solution,  

an excess of sodium bicarbonate was added.  This forms sodium and potassium carbonate,  

which is insoluble in methanol and precipitates  out. It is important to destroy the potassium  

hydroxide with a base such as sodium bicarbonate  and NOT with an acid, as a strong acid will  

react with the potassium cyanide in solution  forming extremely dangerous hydrogen cyanide  

gas. After the sodium bicarbonate was added,  the solution was gravity filtered to remove  

all insoluble impurities. The final solution  should now only contain potassium cyanide.

The methanol was evaporated in a dish over a  day or so to give some nice potassium cyanide  

powder. In total, 3.08g of potassium cyanide  was obtained, corresponding to a 12.3% yield  

based on the starting urea. This poor yield is  likely because the reaction products were not  

broken into a powder prior to dissolution in  the methanol. I wanted to avoid this however,  

because grinding cyanide in a blender scares  me. In the future, I think I will try cycling  

solvent over the reaction products using a soxhlet  extractor to better recover the cyanide produced.  

Anyhow, I hope you guys enjoyed this video, and  I’ll see you in a future project. Okay, bye.