Title or Type of Procedure: Generation of an ether solution of hydrogen cyanide (HCN) for
synthetic purposes (extraction approach)
P.I.: Romas Kazlauskas
Lab Location: 174 Gortner Laboratories
Original Issue Date: November 2012-11-26
Revision Date: none
Prepared by: Jan von Langermann
Approval Signature: not required
This procedure yields an unknown ether solution of HCN mainly for synthetic purposes. For experiments that require a known HCN-concentration, measure the HCN concentration using: Andexer et al. (2006). (Another option is to distill HCN, but this is not recommended for this laboratory due to its high toxicity and explosive nature in combination with air.)
CAUTION: !! PERFORM ALL EXPERIMENTS IN A WELL VENTILATED FUME HOOD!!
(CHECK HOOD FUNCTION WITH A TISSUE TEST.) IF AVAILABLE, USE AN ELECTROCHEMICAL HYDROGEN CYANIDE-DETECTOR! TELL OTHERS IN THE LAB
ABOUT YOUR EXPERIMENT. HYDROGEN CYANIDE (HCN) IS A VERY STRONG POISON AND SHOULD NOT BE INHALED. FURTHERMORE, HCN WITHIN AQUEOUS SOLUTIONS CAN PENETRATE SKIN SO USE GLOVES, LAB COAT AND GOOGLES!
The lethal dose of HCN is ~1 mg/kg absorbed for humans. This procedure generates 135 mg of
HCN. For a 70 kg human, absorption of approximately half of this amount of HCN is lethal, so
follow all safety procedures carefully.
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I. Required materials and glassware
1. 50-mL two-neck-round-bottom flask
2. pH-electrode with an internal temperature probe
3. dropping funnel
4. separating funnel for the extraction of HCN (ca. 50 mL volume)
5. at least 2 round-bottom flasks for a) the final HCN-ether-solution and b) storage-flask for the
aqueous HCN-solution
6. glass stoppers to ensure no leakage of HCN-solutions
7. ice for cooling
8. distilled water
9. tert-butyl-methyl-ether (TBME)
10. 245 mg NaCN or 325 mg KCN
11. 5 M HCl-solution
12. a HCN-waste container to store excess HCN-solutions
13. 30 wt% H2O2 for the oxidation of HCN-waste solutions
14. aqueous sodium hypochlorite solution (bleach) for the oxidation of small hydrogen cyanide
spills.
15. cyanide test strips (from U-Store: ‘CYANIDE TEST STRIP, EMD-10044-1)
16. cyanide antidote (May not be available due to restriction, contact the lab safety officer for
more information + a doctor visit may also be required to learn how to use the kit. Currently the
‘Cyanide Antidote Kit’ is the most widely used kit. It is also known as the Lilly Kit, Pasadena Kit
or the Taylor Kit.
II. ‘Synthesis’ of hydrogen cyanide
The weighted amount of NaCN (or KCN) is transferred into the two-neck-round-bottom flask and
dissolved in 20 mL water. From this point onwards the two-neck-round-bottom flask should be
cooled externally with ice to ensure internal temperatures below 10 °C.
Higher temperatures may result later in an outgassing of HCN. Subsequently the pH-electrode is
added to the two-neck-round-bottom flask and placed into the aqueous cyanide-solution. Please
ensure that the tip of the electrode is covered by the aqueous solution. The position of the electrode within the neck of the flask (ground glass) can be fixed with Parafilm, which also seals a
little bit this position. At this point the dropping funnel should also be added to close the experimental set-up.
After an internal temperature of <5 °C is reached the 5 M HCl-solution is added dropwise slowly
via the dropping funnel (2.5 M H2SO4 may also be used). Simultaneously the pH-value and the
temperature need to be monitored throughout the whole process! The temperature should NOT
exceed 10°C!!
Due to the cyanide–hydrogen cyanide buffer, the pH-value will drop very slowly until the buffer
capacity is depleted.
Eventually very low pH-values (<1.5) will be obtained, which indicates that cyanide was fully
‘transferred’ to hydrogen cyanide. The resulting solution is cooled to <5 °C for the extraction.
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III. Extraction of hydrogen cyanide
Note: Due to the low partition coefficient of HCN the extraction has to be carried out twice. If
required the exact HCN-concentrations can to be measured to ensure correct values for e.g. kinetic measurements (see also references).
The resulting solution is poured from the two-neck-round-bottom flask into the separating funnel
and 10 mL of cooled tert-butyl-methyl-ether (TBME) is added. The combined solutions are shaken vigorously for 30 s to 1 min and left for phase-separation. The lower (aqueous) phase is transferred into a pre-chilled round-bottom-flask and kept on ice. Alternatively the two-neck-roundbottom flask can be used for this purpose. The upper (organic) phase with hydrogen cyanide is
poured into an additional pre-chilled flask, which is also kept on ice. Do not allow the solutions
to warm up, because gaseous HCN may be formed.
Afterward the aqueous phase is extracted again with another 10 mL of ether in an identical way.
The ether phases are combined and stored on ice until its later usage.
Please note that hydrogen cyanide-solutions should NOT be stored in a fridge due to its high toxicity-level and low shelf life stability.
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IV. Disposal of HCN-waste-solutions
All unused HCN-containing solutions are combined and stored within a fume hood for its later
disposal. The following steps should be executed within a well ventilated fume hood.
All waste solutions are combined within a high beaker (DO NOT fill above 50%) and adjusted to
pH 10-11. The mixture is stirred and hydrogen peroxide (30 wt%) is slowly added. Gas formation
may occur (mainly NH3), which shows the ongoing oxidation reaction. Continue adding hydrogen peroxide until no more gas is formed. The reaction is highly exothermic and needs to cool
down afterwards. Then the pH is adjusted to 8-9, which will results in additional gas formation.
Again, the solution is allowed to cool, the final cyanide concentration tested with a cyanide test
stripe, and poured down the drain as nonhazardous aqueous waste.
Hazard identification and risk of exposure to the hazards:
Hydrogen cyanide is a very strong poison, explosive within an air/hydrogen cyanide mixture and
should be handled very, very carefully.
Broken flasks: Do not handle broken glassware directly. Remove it using a brush and dustpan,
tongs or forceps. Plasticware should not be used due to the use of ethers.
Exposure Controls Specific to Above Risk of Exposure
Use only small amount of cyanide to prevent intoxication. Wear gloves, a lab coat and a suitable
eye protection! Cool all relevant solutions and glassware to prevent the generation of gaseous hydrogen cyanide. The ether TBME is chosen because it will not form peroxides.
Fume hood: Execute all relevant procedure steps within a well ventilated fume hood. For your
own safety, store all reactants and waste solutions within the fume hood. Inform your colleagues
about the HCN-experiments and label all flasks correctly.
Biological Waste Disposal Procedures
not required
Spill Response Procedures:
Small hydrogen cyanide spill: small quantities of hydrogen cyanide-solutions are wiped away
with a paper towel or tissue and left in the fume hood. Hydrogen cyanide will slowly evaporate
from the towel and the towel can be disposed after a week without any further treatment.
If available, a sodium hypochlorite solution (bleach) can be used to oxidize small spills directly.
Huge hydrogen cyanide spill: With large quantities of hydrogen cyanide-spill the risk of intoxication arises significantly and in this case of large amounts of free HCN the laboratory should be
evacuated as fast as possible. If possible open the windows! Warn all persons in laboratories near
and above you. The room may only be entered with a working gas mask, which is equipped with
an effective HCN-filter until the HCN-concentration is low enough (e.g. 10 ppm, which can be
tolerated without any health-risks for 8h/day).
Accident Response Procedures
If spills result in a hazard exposure (e.g. face or eye splash, cut or puncture with sharps,
contact with non-intact skin):
 Wash exposed skin with soap and water, flush eyes for 15 min.
 Call 911 and seek medical attention. If symptoms of hydrogen cyanide poisoning appear
medical attention needs to very, very fast due to fast internal suffocation of the patient! Mention the possible risk of hydrogen cyanide intoxication to all relevant persons!
 If available, use a cyanide antidote. Unfortunately most antidotes require an intravenous (IV)
injection, which can only be used by trained personal.
 DO NOT perform mouth-to-mouth/nose ventilation due to the risk of secondary intoxication.
 For urgent care employees you may also go to HealthPartners Occupational and Environmental Medicine (M/F day time or Urgent Care after hours), or UMMC-Fairview Hospital
(24hrs). You may seek medical attention at the closest available medical facility or your own
healthcare provider.
(Follow-up must be done by HealthPartners Occupational and Environmental Medicine.)
 Report the incident to your supervisor, fill out the appropriate documentation. The documents
are needed to collect workers compensation should any complications from the hazardous exposure arise.
- Employee First Report of Injury
- Supervisor Incident Investigation Report
References
J. H. Wolfsie, C. B. Shaffer (1959) Hydrogen cyanide – hazards, toxicology, prevention and
management of poisoning, J. Occup. Med. 281-8.
J. Andexer, J. K. Guterl, M. Pohl, T. Eggert (2006) A high-throughput screening assay for hydroxynitrile lyase activity, Chem. Commun, 4201-3.