☣️ UN 1626 • CLASS 6
Mercuric potassium cyanide
Placard: Toxic. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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Quick details
UN 1626
Class: 6
Placard type: Toxic
ERG: Guide 157 (check current ERG)
Isolation: ERG 157: isolate spill/leak area immediate 25-50m all directions; large spill isolate 100m, downwind evacuate 300m daytime, 800m night
Chemical & Response Details
| Also known as | Potassium mercuric cyanidePotassium mercury cyanideMercuric potassium cyanide solutionPotassium tetracyanomercurate(II) |
| CAS Number | 591-89-4 |
| Appearance | White to off-white crystalline solid or powder. Odorless or faint cyanide odor. May be encountered as an aqueous solution. |
| Flash Point | Not applicable (non-flammable inorganic salt) |
| Boiling Point | Not applicable (decomposes before boiling) |
| Vapor Density | Not applicable (solid, negligible vapor pressure) |
| Water Reactivity | Dissolves in water releasing toxic cyanide and mercury compounds; reaction with acids releases highly toxic hydrogen cyanide gas |
| Extinguishing | Water spray to reduce vapors, CO2, dry chemical; avoid acids which liberate hydrogen cyanide |
| PPE | ⚠️ Level A or B required; full-face SCBA, chemical-resistant suit, gloves, boots; prevent all skin/eye contact due to extreme toxicity |
| Isolation | ERG 157: isolate spill/leak area immediate 25-50m all directions; large spill isolate 100m, downwind evacuate 300m daytime, 800m night |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
- Reaction with water or moist air may release toxic, corrosive or flammable gases.
- Reaction with water may generate much heat that will increase the concentration of fumes in the air.
- Fire will produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above
- Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.).
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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UN 1626 — Mercuric potassium cyanide HAZMAT RADIO NOTE — UN 1626
Product: Mercuric potassium cyanide
Class 6 / Toxic / ERG 157
PPE: Level A or B required; full-face SCBA, chemical-resistant suit, gloves, boots; prevent all skin/eye contact due to extreme toxicity
ISOLATION: ERG 157: isolate spill/leak area immediate 25-50m all directions; large spill isolate 100m, downwind evacuate 300m daytime, 800m night
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 1626 — Mercuric potassium cyanide
Class: 6 | Placard: Toxic | ERG Guide: 157
Appearance: White to off-white crystalline solid or powder. Odorless or faint cyanide odor. May be encountered as an aqueous solution.
Water Reactivity: Dissolves in water releasing toxic cyanide and mercury compounds; reaction with acids releases highly toxic hydrogen cyanide gas
Extinguishing: Water spray to reduce vapors, CO2, dry chemical; avoid acids which liberate hydrogen cyanide
PPE: Level A or B required; full-face SCBA, chemical-resistant suit, gloves, boots; prevent all skin/eye contact due to extreme toxicity
Isolation: ERG 157: isolate spill/leak area immediate 25-50m all directions; large spill isolate 100m, downwind evacuate 300m daytime, 800m night
— Key Hazards —
• TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
• Reaction with water or moist air may release toxic, corrosive or flammable gases.
• Reaction with water may generate much heat that will increase the concentration of fumes in the air.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/1626 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1626 Mercuric potassium cyanide Cls6 ERG157 | allfirefighter.com/hazmat/un/1626SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/1626
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FAQ
TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance Reaction with water or moist air may release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.).
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level A or B required; full-face SCBA, chemical-resistant suit, gloves, boots; prevent all skin/eye contact due to extreme toxicity
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 157 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.