7774-29-0 Usage
Description
Mercury(II) iodide, also known as mercuric iodide, is an inorganic compound with the chemical formula HgI2. It is a yellowish, crystalline solid that is sensitive to light and decomposes upon exposure. Mercury(II) iodide is a heavy and toxic compound, and it is soluble in water and ethanol.
Uses
Used in Analytical Chemistry:
Mercury(II) iodide is used as an analytical reagent for the analysis of ammonia. It is a key component of Nessler's reagent, which is an alkaline mercuric potassium iodide solution used for the detection and measurement of ammonia in various samples.
Used in Animal Chemistry:
In animal chemistry, mercury(II) iodide is used for the preparation of Nessler's reagent, which is employed for the detection of the presence of ammonia in biological samples.
Used in Semiconductor Industry:
Mercury(II) iodide is a semiconductor material, which makes it useful in some x-ray and gamma-ray detection and imaging devices that operate at room temperatures.
Used in Veterinary Medicine:
In veterinary medicine, mercury(II) iodide is used in blister ointments for the treatment of skin diseases such as exostoses and bursal enlargement in animals.
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.
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
