A potassium cyanide solution is required to calibrate absorbance curves in a cassava cyanide quantification protocol.
Therefore, to obtain a stock KCN solution (5mM) for calibration of absorbance values:
1. Dry KCN over concentrated sulfuric acid (H2SO4) in a desiccator for at least 12h
2. Dissolve 125 mg in 500 mL of 0.2M NaOH b
3. Dilute the above 100 times in 0.1 M pH 6 phosphate buffer in a volumetric flask to give a 2.5 μg / mL solution.
The question is about the drying process of potassium cyanide over concentrated sulfuric acid, how is it carried out in the laboratory and what amount of KCN and H2SO4 would be necessary to carry out this step?
Thank you very much in advance
Check out some book of fundamental laboratory procedures eg https://biocyclopedia.com/index/chem_lab_methods/drying.php
Be careful that KCN doesn't come into contact with H2SO4, otherwise you have created a gas chamber.
Dear Angélica Niño thank you for asking this very interesting technical questions. Due to the high potential risk of toxic HCN formation I would strongly suggest to stay away from drying KCN over concentrated sulfuric acid (H2SO4) in a desiccator! As already mentioned by Jukka Salminen an accidental contact of your KCN sample with concentrated siulfuric acid could lead to a potentially deadly accident due to liberation of highly toxic hydrocyanic acid.
If you want to use a desiccator for drying your KCN sample, my suggestion would be to use solid P4O10, although even this drying agent could also present a problem when it forms a layer of phosphoric acid on the surface. Much less risky is the use of anhydrous CaCl2 as drying agent in the desiccator.
Personally I would place the KCN in a round-bottomed flask and dry the sample under vacuum, perhaps with slight heating.
Good luck and please stay safe and healthy! 👍
Jukka SalminenJukka Salminen and Frank T. Edelmann , thanks so much for your answers and recommendations. I wil be careful!
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