HazMat Tool — substance information

Hydrogen iodide, anhydrous

HMT May 2026

UN / ID: UN 2197
Hazard class: 2.3
Packing group: —
ERG guide: ERG 125
Special provisions: SP 3, SP B14, SP N86, SP N89
Source: 49 CFR §172 (2026/05)

On this page

Hydrogen iodide, anhydrous

Hydrogen iodide (HI) is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under standard conditions, whereas the latter is an aqueous solution of the gas. They are interconvertible. Wikipedia

Substance Data

Source: PubChem

CAS-Number

10034-85-2

Flash Point

n/a

Boiling Point

n/a

Emergency Response Guide No. 125

Hazardous Materials Table

Source: 49 CFR §172 (2026/05)

(3) Hazard Class

2.3
Poisonous gas

(4) Identification number

UN 2197

(5) Packing Group

n/a

(6) Labels

(7) Special Provisions (§172.102)

×Note:
Special provisions may be very complex. The extracts are taken from 49 CFR §172.102. Please be careful with the information, as necessary, additional conditions may be applied that are not written here. Please check the original source and report bugs.

3	This material is poisonous by inhalation (see §171.8) in Hazard Zone C (see §173.116), and must be described as an inhalation hazard under the provisions of this subchapter. Browse special provision 3
B14	Each bulk packaging, except a tank car or a multi-unit-tank car tank, must be insulated with an insulating material so that the overall thermal conductance at 15.5 °C (60 °F) is no more than 1.5333 kilojoules per hour per square meter per degree Celsius (0.075 Btu per hour per square foot per degree Fahrenheit) temperature differential. Insulating materials must not promote corrosion to steel when wet. Browse special provision B14
N86	UN pressure receptacles made of aluminum alloy are not authorized. Browse special provision N86
N89	When steel UN pressure receptacles are used, only those bearing the “H” mark are authorized. Browse special provision N89

(8) Packing Authorizations (§173.***)

(8A) Exceptions	None
(8B) Non-bulk	304	see 49 CFR §173.304
(8C) Bulk	314, 315	see 49 CFR §173.314, 315

(9) Quantity Limits

(9A) Passenger aircraft/rail	Forbidden
(9B) Cargo aircraft only	Forbidden

(10) Vessel stowage

(10A) Location

Stowage category “D” means the material must be stowed “on deck only” on a cargo vessel or on a passenger vessel carrying a number of passengers limited to not more than the larger of 25 passengers or one passenger per each 3 m of overall vessel length, but the material is prohibited on a passenger vessel in which the limiting number of passengers is exceeded.

Source: 49 CFR §172.101(k)

(10B) Other

40	see 49 CFR §176.84

Source: 49 CFR §176.84

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.

Note: In this segregation and separation chart are HazMat of hazard class 2.3 considered depending on their poisonousness by inhalation (Hazard zone A/B). See PHMSA Interpretation #09-0252.

Scope & sources (important)Click to show CFR references

This check evaluates segregation per 49 CFR §177.848. Additional loading/unloading and handling requirements may still apply; see 49 CFR §177 Subpart B (Loading and Unloading):

§177.834 - General requirements
§177.835 - Class 1 materials
§177.837 - Class 3 materials
§177.838 - Class 4 (flammable solid) materials, Class 5 (oxidizing) materials, and Division 4.2 (pyroforic liquid) materials
§177.839 - Class 8 (corrosive) materials
§177.840 - Class 2 (gases) materials
§177.841 - Division 6.1 and Division 2.3 materials
§177.842 - Class 7 (radioactive) material
§177.843 - Contamination of vehicles

Similar substances

UN / ID	Proper shipping name	Hazard class
UN 3165	Aircraft hydraulic power unit fuel tank (containing a mixture of anhydrous hydrazine and monomethyl hydrazine) (M86 fuel)	3
UN 0508	1-Hydroxybenzotriazole, anhydrous, dry or wetted with less than 20 percent water, by mass	1.3C
UN 1382	Potassium sulfide, anhydrous or Potassium sulfide with less than 30 percent water of crystallization	4.2
UN 1385	Sodium sulfide, anhydrous or Sodium sulfide with less than 30 percent water of crystallization	4.2
NA 2845	Ethyl phosphonous dichloride, anhydrous pyrophoric liquid	6.1
UN 2075	Chloral, anhydrous, stabilized	6.1
NA 2927	Ethyl phosphonothioic dichloride, anhydrous	6.1
UN 1048	Hydrogen bromide, anhydrous	2.3
UN 1050	Hydrogen chloride, anhydrous	2.3
UN 1052	Hydrogen fluoride, anhydrous	8
UN 2202	Hydrogen selenide, anhydrous	2.3
UN 1725	Aluminum bromide, anhydrous	8
UN 1726	Aluminum chloride, anhydrous	8
UN 1463	Chromium trioxide, anhydrous	5.1
UN 1768	Difluorophosphoric acid, anhydrous	8