HazMat Tool — substance information
Reference only — not a shipping paper, placard mandate, or CVI record.
Isothiocyanic acid
HMT 15 June 2026- UN / ID
- —
- Hazard class
- Forbidden
- Packing group
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- ERG guide
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- Special provisions
- —
- Source
- 49 CFR §172 (15 June 2026)
Isothiocyanic acid
Thiocyanic acid is a chemical compound with the formula HSCN and structure H−S−C≡N, which exists as a tautomer with isothiocyanic acid (H−N=C=S). The isothiocyanic acid tautomer tends to dominate with the compound being about 95% isothiocyanic acid in the vapor phase. It is a moderately strong acid, with a pKa of 1.1 at 20 °C and extrapolated to zero ionic strength. One of the thiocyanic acid tautomers, HSCN, is predicted to have a triple bond between carbon and nitrogen Wikipedia
Hazardous Materials Table
Source: 49 CFR §172 (15 June 2026)(3) Hazard classForbidden |
(4) Identification number |
(5) Packing Group |
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(6) Labels — |
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(7) Special Provisions (§172.102)
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(8) Packing Authorizations (§173.***) 
| (8A) Exceptions | — |
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| (8B) Non-bulk | — |
| (8C) Bulk | — |
(9) Quantity Limits
| (9A) Passenger aircraft/rail | — |
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| (9B) Cargo aircraft only | — |
(10) Vessel stowage
| (10A) Location | — |
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| (10B) Other | — |
Segregation chart for load, transport, and storage
This chart shows whether loading, transport, or storage with other hazard classes is permitted, prohibited, or restricted. Based on 49 CFR §177.848.
This Hazmat is classified as "Forbidden". This means the material may not be offered for transportation or transported in the applicable mode of transport.
Similar substances
| UN / ID | Proper shipping name | Hazard class |
|---|---|---|
| UN 1545 | Allyl isothiocyanate, stabilized | 6.1 |