7774-29-0 Usage
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
Different sources of media describe the Uses of 7774-29-0 differently. You can refer to the following data:
1. 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.
2. In animal chemistry for preparation of Nessler's Reagent (alkaline mercuric potassium iodide solution).
3. 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.
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+ + 2Iˉ → 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]2ˉ:
HgI2 + 2Iˉ → [HgI4]2ˉ
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]2ˉ + NH3 + 3OHˉ → I—Hg—O—Hg—NH3 +7Iˉ + 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+ + 6Iˉ → Cu2HgI4 + I2
? ? ? ? ? ? ? ?(red)
2Ag+ + Hg2+ + 6Iˉ → 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.
Chemical Properties
Different sources of media describe the Chemical Properties of 7774-29-0 differently. You can refer to the following data:
1. 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
2. Red Solid
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.
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)
Check Digit Verification of cas no
The CAS Registry Mumber 7774-29-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,7,7 and 4 respectively; the second part has 2 digits, 2 and 9 respectively.
Calculate Digit Verification of CAS Registry Number 7774-29:
(6*7)+(5*7)+(4*7)+(3*4)+(2*2)+(1*9)=130
130 % 10 = 0
So 7774-29-0 is a valid CAS Registry Number.
InChI:InChI=1/C9H12N2O.Hg.2HI/c1-11(2)9(12)10-8-6-4-3-5-7-8;;;/h3-7H,1-2H3,(H,10,12);;2*1H/q;+2;;/p-2
