How to Prepare Potassium Cyanide
Summary
TLDRThis 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
🧪 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.
Mindmap
Keywords
💡Potassium cyanide
💡Blueprints
💡Urea
💡Potassium hydroxide
💡Decomposition
💡Isocyanic acid
💡Tripotassium cyanurate
💡Reduction
💡Methanol
💡Prussian blue pigment
💡Sodium bicarbonate
💡Soxhlet extractor
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.
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