MERCURY(II) IODIDE Property

Melting point:

259 °C(lit.)

Boiling point:

354 °C(lit.)

Density 

6.36

vapor pressure 

0.006 hPa (80 °C)

Flash point:

350°C subl.

storage temp. 

Store at RT.

solubility 

potassium iodide solution: passes test

form 

beads

Specific Gravity

6.271

color 

White

Odor

Odorless

PH

6-7 (50g/l, H2O, 20℃)(slurry)

Water Solubility 

Insoluble inwater. Slightly soluble in alcohol, ether, acetone, chloroform, ethyl acetate, olive oil and castor oil.

Sensitive 

Light Sensitive

Merck 

14,5879

Solubility Product Constant (Ksp)

pKsp: 28.54

Exposure limits

ACGIH: TWA 0.025 mg/m3; TWA 0.01 ppm (Skin)
NIOSH: IDLH 10 mg/m3; TWA 0.05 mg/m3; Ceiling 0.1 mg/m3

Stability:

Stable. Incompatible with strong oxidizing agents, potassium, sodium, interhalogens. Light-sensitive.

CAS DataBase Reference

7774-29-0(CAS DataBase Reference)

EPA Substance Registry System

Mercuric iodide (7774-29-0)

Safety

Hazard Codes 

T+,N

Risk Statements 

26/27/28-33-50/53

Safety Statements 

13-28-45-60-61

RIDADR 

UN 2025 6.1/PG 2

WGK Germany 

3

RTECS 

OW5250000

F 

8

TSCA 

Yes

HazardClass 

6.1

PackingGroup 

II

HS Code 

28521000

Hazardous Substances Data

7774-29-0(Hazardous Substances Data)

Toxicity

LD50 orally in Rabbit: 18 mg/kg LD50 dermal Rat 75 mg/kg

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H373May cause damage to organs through prolonged or repeated exposure

H410Very toxic to aquatic life with long lasting effects

Precautionary statements

P262Do not get in eyes, on skin, or on clothing.

P273Avoid release to the environment.

P280Wear protective gloves/protective clothing/eye protection/face protection.

MERCURY(II) IODIDE Chemical Properties,Usage,Production

Physical Properties

Exists in two allotropic forms: red tetragonal allotropic modification (alpha form) and the yellow rhombic modification (beta form).
The red iodide has a density 6.36 g/cm3 at 25°C; transforms to yellow form at 127°C; also converts to yellow form at –180°C; slightly soluble in water (100 mg/L at 25°C); moderately soluble in acetone and alcohol.
The yellow iodide has a density of 6.09 g/cm3 at 27°C; melts at 259°C; vaporizes at 354°C; practically insoluble in water; low-to-moderately soluble in alcohol, benzene and other organic solvents.

Uses

Mercury(II) iodide is used as an analytical reagent, in Nesslers reagent for the analysis of ammonia. The compound also is used in ointments for the treatment of skin diseases.

Preparation

Mercury(II) iodide is precipitated in its yellow form by adding a stoichiometric amount of potassium iodide to an aqueous solution of mercury(II) salt (e.g., HgCl2):
Hg2+ + 2I¯ → HgI2
The yellow precipitate rapidly turns red and dissolves in solution when excess potassium iodide is added.
Also, mercury (II) iodide is formed when mercury is rubbed with iodine moistened with ethanol.

Reactions

Mercury(II) iodide reacts with excess iodide ion forming complex tetraiodomercurate(II) ion, [HgI4]^2¯:
HgI2 + 2I¯ → [HgI4]^2¯
In caustic soda or caustic potash solution, mercury(II) iodide forms complex salts, Na2HgI4 and K2HgI4, respectively. Alkaline solution of this complex in excess potassium hydroxide is known as Nessler’s reagent, used to analyze ammonia. The reaction of Nessler’s reagent with ammonia may be written as:
2[HgI4]^2¯ + NH3 + 3OH¯ → I—Hg—O—Hg—NH3 +7I¯ + 2H2O
Similar complexes of silver, copper and other metals are known. Some of them change colors on heating and are used in heat-sensitive paints and applied to machine parts made out of brass or iron:
2Cu²⁺ + Hg²⁺ + 6I¯ → Cu2HgI4 + I2
               (red)
2Ag⁺ + Hg²⁺ + 6I¯ → Ag2HgI4 + I2
             (yellow) In general, mercury(II) iodide forms neutral complexes of compositions M2(HgI4) and M(HgI3) with alkali and alkaline metal iodides.
When heated with dilute caustic potash solution, a yellow brown powder of composition HgI2•3HgO is obtained.

Description

Mercuric iodide is a heavy, scarlet red, odorless, crystalline solid. It may be shipped as a red solution. It turns to a yellow powder at 127℃ and red upon cooling. Molecular weight= 454.40;Boiling point=(sublimes) 354℃; Freezing/Melting point=259℃. Hazard Identification (based on NFPA-704 M Rating System): Health 3, Flammability 0, Reactivity 0. Slightly soluble in water.

Chemical Properties

Mecuric iodide is a heavy, scarlet red, odorless, crystalline solid. It may be shipped as a red solution. It turns to a yellow powder @ 127℃ and red upon cooling

Chemical Properties

Red Solid

Uses

In animal chemistry for preparation of Nessler's Reagent (alkaline mercuric potassium iodide solution).

Uses

Mercury(II) iodide is is used for preparation of Nessler's reagent, used for detection of presence of ammonia. It is a semiconductor material, used in some x-ray and gamma ray detection and imaging devices operating at room temperatures. In veterinary medicine, it is used in blister ointments in exostoses, bursal enlargement, etc.

Definition

ChEBI: Mercury diiodide is a mercury coordination entity composed of mercury and iodine with formula HgI2.

General Description

A scarlet-red odorless tasteless powder. Sensitive to light. Insoluble in water and sinks in water. At elevated temperatures turns yellow but turns back to red upon cooling. Poison.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

MERCURY(II) IODIDE is a mild reducing agent. Reacts with sodium azide to form mercury(II) azide, which is shock, friction, and heat sensitive. Incompatible with acetylene, ammonia, chlorine dioxide, azides, chlorine trifluoride, calcium (because of amalgam formation), sodium carbide, lithium, rubidium, copper .

Hazard

Highly toxic by ingestion, inhalation, and skin absorption; strong irritant.

Health Hazard

All forms of exposure to MERCURY(II) IODIDE are hazardous. Acute systemic mercurialism may be fatal within a few minutes; death by uremic poisoning is usually delayed 5-12 days. Acute poisoning has resulted from inhaling dust concentrations of 1.2-8.5 mg/m 3 of air; symptoms include tightness and pain in chest, coughing, and difficulty in breathing. Ingestion causes necrosis, pain, vomiting, and severe purging. Contact with eyes causes ulceration of conjunctiv a and cornea. Contact with skin causes irritation and possible dermatitis; systemic poisoning can occur by absorption through skin.

Fire Hazard

Special Hazards of Combustion Products: Fumes from fire may contain toxic mercury vapor.

Safety Profile

A poison. When heated to decomposition it emits very toxic fumes of Hg and I-. See also MERCURY(I1) IODIDE.

Potential Exposure

Mercuric iodide is used in medicine and in analytical chemistry.

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. Medical observation is recommended for 2448 h after breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a corticosteroid spray. Antidotes and special procedures for medical personnel: The drug NAP (n-acetyl penicillamine) has been used to treat mercury poisoning, with mixed success. Note to physician: For severe poisoning BAL [British AntiLewisite, dimercaprol, dithiopropanol (C3H8OS2)] has been used to treat toxic symptoms of certain heavy metals poisoning including mercury. Although BAL is reported to have a large margin of safety, caution must be exercised, because toxic effects may be caused by excessive dosage. Most can be prevented by premedication with 1-ephedrine sulfate (CAS: 134-72-5).

storage

Color Code—Blue: Health Hazard/Poison: Store in a secure poison location. Prior to working with this chemical you should be trained on its proper handling and storage. Mercuric iodide must be stored to avoid contact with chlorine trifluoride, sodium, and potassium, since violent reactions occur. Store in tightly closed containers in a cool, well-ventilated area away from light, acids, and heat. Protect containers from physical damage.

Shipping

This compound requires a shipping label of “POISONOUS/TOXIC MATERIALS” (solution). It falls in Hazard Class 6.1 and Packing Group II.

Purification Methods

Crystallise it from MeOH or EtOH and wash it repeatedly with distilled water (solubility is 0.006% at ~25o). It has also been mixed thoroughly with excess 0.001M iodine solution, filtered, washed with cold distilled water, rinsed with EtOH and Et2O, and dried in air. It changes colour reversibly to yellow at ~130o. [Friend Nature 109 341 1922.] POISONOUS.

Incompatibilities

Violent reaction with active metals; potassium, sodium, acids, chlorine trifluoride. Inorganic mercury compounds are incompatible with acetylene, ammonia, chlorine dioxide; azides, calcium (amalgam formation), sodium carbide, lithium, rubidium, copper. Mercury iodide is a mild reducing agent. Keep away from oxidizers. Reacts with sodium azide to form mercury(II) azide, which is shock-, friction-, and heat-sensitive. Incompatible with acetylene, ammonia, chlorine dioxide, azides, chlorine trifluoride, calcium (because of amalgam formation), sodium carbide, lithium, rubidium, copper (NIOSH, 1997)