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Hydriodic acid

Outline Toxicity Production method Chemical Properties Uses Category Explosive hazardous characteristics Flammability hazard characteristics Storage Characteristics Extinguishing agent
Hydriodic acid
Hydriodic acid structure
Chemical Name:
Hydriodic acid
Hydriodic;55-57 wt.%;hydrogen Hydrideiodine;caswellno482c;Hydrogeniodid;Hydroidic acid;Jodwasserstoff;HYDRIODIC ACID;HYDRIOTIC ACID
Molecular Formula:
Formula Weight:
MOL File:

Hydriodic acid Properties

Melting point:
Boiling point:
127 °C(lit.)
1.96 g/mL at 20 °C
Flash point:
storage temp. 
Refrigerator (+4°C)
-10(at 25℃)
colorless or yellow gas
Water Solubility 
Stable. Incompatible with bases, amines. Corrodes steel. May discolour on exposure to air and light.
CAS DataBase Reference
10034-85-2(CAS DataBase Reference)
NIST Chemistry Reference
Hydrogen iodide(10034-85-2)
EPA Substance Registry System
Hydriodic acid(10034-85-2)
  • Risk and Safety Statements
  • Hazard and Precautionary Statements (GHS)
  • NFPA
Hazard Codes  C
Risk Statements  34-35
Safety Statements  26-36/37/39-45-9
RIDADR  UN 1787 8/PG 2
WGK Germany  -
RTECS  MW3760000
HazardClass  8
PackingGroup  II
Hazardous Substances Data 10034-85-2(Hazardous Substances Data)
Signal word: Danger
Hazard statements:
Code Hazard statements Hazard class Category Signal word Pictogram P-Codes
H314 Causes severe skin burns and eye damage Skin corrosion/irritation Category 1A, B, C Danger P260,P264, P280, P301+P330+ P331,P303+P361+P353, P363, P304+P340,P310, P321, P305+ P351+P338, P405,P501
H318 Causes serious eye damage Serious eye damage/eye irritation Category 1 Danger P280, P305+P351+P338, P310
H335 May cause respiratory irritation Specific target organ toxicity, single exposure;Respiratory tract irritation Category 3 Warning
Precautionary statements:
P260 Do not breathe dust/fume/gas/mist/vapours/spray.
P261 Avoid breathing dust/fume/gas/mist/vapours/spray.
P280 Wear protective gloves/protective clothing/eye protection/face protection.
P310 Immediately call a POISON CENTER or doctor/physician.
P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
P303+P361+P353 IF ON SKIN (or hair): Remove/Take off Immediately all contaminated clothing. Rinse SKIN with water/shower.
P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.
P405 Store locked up.

NFPA 704

Diamond Hazard Value Description
3 0
Health   3 Short exposure could cause serious temporary or moderate residual injury (e.g. liquid hydrogen, sulfuric acid, calcium hypochlorite, hexafluorosilicic acid)
Flammability   0 Materials that will not burn under typical fire conditions, including intrinsically noncombustible materials such as concrete, stone, and sand. Materials that will not burn in air when exposed to a temperature of 820 °C (1,500 °F) for a period of 5 minutes.(e.g. Carbon tetrachloride)
Instability   0 Normally stable, even under fire exposure conditions, and is not reactive with water (e.g. helium,N2)

(NFPA, 2010)

Hydriodic acid price More Price(19)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
Sigma-Aldrich 210013 Hydriodic acid contains no stabilizer, distilled, 57 wt. % in H2O, 99.99% trace metals basis 10034-85-2 50ml $81 2018-11-13 Buy
Sigma-Aldrich 210013 Hydriodic acid contains no stabilizer, distilled, 57 wt. % in H2O, 99.99% trace metals basis 10034-85-2 250ml $271 2018-11-13 Buy
Alfa Aesar 036484 Hydriodic acid, ACS, 55-58% 10034-85-2 *4x500ml $757 2018-11-16 Buy
Alfa Aesar 036484 Hydriodic acid, ACS, 55-58% 10034-85-2 50ml $38.5 2018-11-16 Buy
Sigma-Aldrich 752851 Hydriodic acid 57 wt. %, distilled, 99.999% trace metals basis 10034-85-2 25g $31.6 2018-11-13 Buy

Hydriodic acid Chemical Properties,Uses,Production


hydriodic acid is a strong acid. Chemical Formula is HI. The molecular weight is 127.91. Colorless gas, pale yellow liquid or blob solid. There is a strong pungent odor. Melting point is-50.8 ℃, the boiling point is-35.38 ℃, relative density is 5.660 (gas), 2.85-4.7 (liquid), the refractive index is 1.46616. And form a white acid mist with water vapor in the air, easily soluble in water and emit a lot of heat to generate Hydriodic acid. Slightly soluble in ethanol. Unstable, heated to decompose into hydrogen and iodine under the light. Significantly decomposition above 300 ℃. Its constant boiling solution is colorless or light yellow fuming liquid, boiling point is 127 ℃, relative density is 1.7015, strong acid (degree of dissociation of 0.1 mol·L-1 hydroiodic solution up to 95%), the solubility of Hydriodic acid in an organic solvent is much smaller than in water, present in non-electrolytes or weak electrolytes, its ionization constant in pyridine is 3 × 10-3. Easily break down into hydrogen and iodine in the air. With a strong reduction, It has the strongest reducibility in hydrohalic acids, may be oxidated to free iodine by Cl2, Br2, concentrated sulfuric acid. Oxidation by air at room temperature, can be oxidated by concentrated nitric acid, concentrated sulfuric acid. It reacts with most metals to form the corresponding iodide and hydrogen. Method: by heating reaction of sodium iodide and phosphoric acid or reaction of phosphorus with iodine, water was added dropwise on a mixture of phosphorus and iodine, can also be derived by suspending iodine in water and ventilation with hydrogen sulfide. Its constant boiling solution is derived by ventilating Hydriodic acid gas into the water. Uses: its constant boiling solution is often used as a reducing agent, a disinfectant, analytical reagents, preparation of iodized salt, synthetic drugs, dyes, perfumes and so on. It is synthesized by iodine vapor and hydrogen under platinum catalytic conditions or derived by hydrolysis of phosphorus triiodide.
The above information is edited by Yan Yanyong of Chemicalbook.


It is highly corrosive to most metals, Non-combustible. But it reacts violently with fluorine, potassium nitrate, potassium chlorate and so on. As hydrochloric acid, it has a strong irritation, gases or vapors can irritate the eyes and respiratory system. Liquid can burn the skin. The patient who inhaled vapors should immediately keep away from the contaminated area, put to rest and keep warm. Accidentally splashed into the eyes, rinse immediately with plenty of water for 15min. Contact with skin, wash immediately with plenty of water. Swallowed immediately rinse mouth, rushed to the hospital for treatment.

Production method

Slowly add iodine and red phosphorus to a reactor filled with water, and react under stirring, filter the reaction solution, and distill the filtrate, collect fractions of 125~130 ℃, obtain Hydroiodic.
2P + 5I2 → 2PI5
PI5 + 4H2O → 5HI + H3PO4

Chemical Properties

Hydroiodic acid is aqueous solution of Hydriodic acid. When fresh, it is colorless, soon precipitates iodine with yellow to brown in air and sunlight. Azeotrope (56.9% HI), the relative density is 1.70. Boiling point is 127 ℃. Goods hydroiodic are divided into three types: 57% HI, relative density is 1.70. 47% HI, relative density is 1.5. 1% HI, relative density is 1.1. Add 1.5% hypophosphorous acid to make it bleach. The critical temperature is 150 ℃: the critical pressure is 8.3MPa. The dielectric constant is 3.57 at-45 ℃. Conductivity is 8.5 × 10-10S · cm-1. Heat of vaporization is 19.76 Kj/mol, melting heat is 2.87 Kj/mol. Easily soluble in water, soluble in organic solvents.


1. Used for producing organic iodide. As general reagents and pharmaceutical intermediates.
2. Used as the analysis reagents, also used in the preparation of the iodide.
3. Used as a reducing agent, also used in the synthesis of alkyl iodine and other alkyl iodide.
4. Used for Determination of methoxy, ethoxy and selenium, dissolution of acid-insoluble inorganic substance, such as an alkaline earth metal sulfate and mercury iodide and so on. Used as a reducing agent. Used for the preparation of iodide.
5. Used for Determination of methoxy, dissolution of acid-insoluble (especially hot) inorganic substance, such as an alkaline earth metal sulfate and mercury iodide and so on. Used as a reducing agent.


Compressed gas and liquefied gas.

Explosive hazardous characteristics

Contacting with alkali metals can be explosive, thermal decomposition into toxic iodine vapor in the case of heat, produce toxic hydroiodic in the case of water.

Flammability hazard characteristics

Combustible in case of N,N-dinitroso pentamethylene tetramine, release hydrogen cyanide gas in case of cyanide toxic, thermal decomposition of toxic iodide gases.

Storage Characteristics

Treasury ventilation, low-temperature drying and stored separately from cyanide, N,N-dinitroso pentamethylene tetramine, bases.

Extinguishing agent


Chemical Properties

Hydrogen iodide is a colourless to yellow/brown with an acrid odour non-flammable gas. Hydrogen iodide is incompatible with water and other halides. Hydrogen iodide, upon contact with moisture in air, releases dense vapours. Hydrogen iodide reacts with water to form corrosive acids and reacts violently with alkalis. Most metals corrode rapidly on contact with wet hydrogen iodide, and prolonged exposure of hydrogen iodide to fire or intense heat has been reported to cause the container to rupture and rocket.


Reducing agent, manufacture of inorganic iodides, pharmaceuticals, disinfectants. The 57% acid is also used for analytical purposes, such as methoxyl determinations.


Hydriodic acid is used in the manufactureof iodides, as a reducing agent, and indisinfectants and pharmaceuticals.


hydrogen iodide: A colourless gas,HI; m.p. –51°C; b.p. –35.38°C. It canbe made by direct combination ofthe elements using a platinum catalyst.It is a strong acid dissociating extensivelyin solution (hydroiodic acid or hydriodic acid). It is also a reducingagent.

General Description

A colorless to yellow liquid with a pungent odor. Consists of a solution of hydrogen iodide in water. Fumes irritate the eyes and mucous membranes. Corrosive to metals and to tissue.
It is prepared by the reaction of iodine and hydrosulfuric acid or by the reaction of phosphorus plus iodine plus water followed by distillation. Concentrated hydroiodic acid reacts with the oxygen of the air to form free iodine, which gives a brownish color to the solution. It also gives an idea of the reducing nature of this acid. It is an important reagent in organic chemistry and is used commercially in the preparation of iodides.

Air & Water Reactions

Soluble in water with release of heat.

Reactivity Profile

HYDROIODIC ACID reacts exothermically with organic bases (amines, amides) and inorganic bases (oxides and hydroxides of metals). Reacts exothermically with carbonates (including limestone and building materials containing limestone) and hydrogen carbonates to generate carbon dioxide. Reacts with sulfides, carbides, borides, and phosphides to generate toxic or flammable gases. Reacts with many metals (including aluminum, zinc, calcium, magnesium, iron, tin and all of the alkali metals) to generate flammable hydrogen gas. Reacts violently with acetic anhydride, 2-aminoethanol, ammonium hydroxide, calcium phosphide, chlorosulfonic acid, 1,1-difluoroethylene, ethylenediamine, ethyleneimine, oleum, perchloric acid, b-propiolactone, propylene oxide, silver perchlorate/carbon tetrachloride mixture, sodium hydroxide, uranium(IV) phosphide, vinyl acetate, calcium carbide, rubidium carbide, cesium acetylide, rubidium acetylide, magnesium boride, mercury(II) sulfate [Lewis]. Mixtures with concentrated sulfuric acid can evolve toxic hydrogen iodide gas at a dangerous rate. Decomposes at high temperatures to emit toxic products. Reacts with fluorine, dinitrogen trioxide, nitrogen dioxide/dinitrogen tetraoxide, and fuming nitric acid.


Strong irritant. Poison.

Health Hazard

TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Health Hazard

Hydriodic acid is a corrosive liquid thatcan produce burns on contact with the skin.Contact of acid with the eyes can causesevere irritation. The gas, hydrogen iodide, isa strong irritant to the eyes, skin, and mucousmembranes. No exposure limit has been setfor this gas.

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.

Purification Methods

Iodine can be removed from aqueous HI, probably as the amine hydrogen triiodide, by three successive extractions using a 4% solution of Amberlite LA-2 (a long-chain aliphatic amine) in CCl4, toluene or pet ether (10mL per 100mL of acid). [Davidson & Jameson Chem Ind (London) 1686 1963.] Extraction with tributyl phosphate in CHCl3 or other organic solvents is also suitable. Alternatively, a De-acidite FF anion-exchange resin column in the OH--form using 2M NaOH, then into its I--form by passing dilute KI solution through, can be used. Passage of an HI solution under CO2 through such a column removes polyiodide. The column can be regenerated with NaOH. [Irving & Wilson Chem Ind (London) 653 1964]. The earlier method was to reflux with red phosphorus and distil in a stream of N2. The colourless product is stored in ampoules in the dark [Bradbury J Am Chem Soc 74 2709 1952, Heisig & Frykholm Inorg Synth I 157 1939]. It fumes in moist air. HARMFUL VAPOURS.

Hydriodic acid Preparation Products And Raw materials

Raw materials

Preparation Products

Hydriodic acid Suppliers

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Hydriodic acid Spectrum

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