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Thiourea ( CASNO:62-56-6 )
Identification and Related Records
- CAS Registry number:
- Molecular Formula:
- Molecular Weight:
- Canonical SMILES:
Chemical and Physical Properties
- white crystals
- Melting Point:
- Boiling Point:
- 186.8 °C at 760 mmHg
- Refractive Index:
- 1.637 (30 C)
- Flash Point:
- 66.8 °C
- 13.6 g/100 mL (20℃)
- 13.6 g/100 mL (20 °C)
- White crystalline solid
Almost colorless, rhombohedral crystals or needles from ethanol
White lustrous crystals
- Stable. Incompatible with strong acids, strong bases, strong oxidizing agents, metallic salts, proteins, hydrocarbons. May react violently with acrolein.
- HS Code:
- Storage temp:
- Store at RT.
- Spectral properties:
- MAX ABSORPTION (H2O PH 7.4): 238 NM (LOG E= 4.1); SADTLER REF NUMBER: 3962, 12062 (IR, PRISM); 8315 (IR, GRATING)
Max absorption (methanol): 241 nm (UV)
IR: 4841 (Coblentz Society Spectral Collection)
UV: 3292 (Sadtler Research Laboratories Spectral Collection)
Raman: 941 (Sadtler Research Laboratories Spectral Collection)
MASS: 52446 (NIST/EPA/MSDC Mass Spectral Database 1990 version)
- Computed Properties:
- Molecular Weight:76.12086 [g/mol]
Rotatable Bond Count:0
Topological Polar Surface Area:84.1
Heavy Atom Count:4
Isotope Atom Count:0
Defined Atom Stereocenter Count:0
Undefined Atom Stereocenter Count:0
Defined Bond Stereocenter Count:0
Undefined Bond Stereocenter Count:0
Covalently-Bonded Unit Count:1
Feature 3D Acceptor Count:1
Feature 3D Donor Count:2
Effective Rotor Count:0
Conformer Sampling RMSD:0.4
CID Conformer Count:1
Safety and Handling
- Hazard Codes:
- Risk Statements:
- Safety Statements:
- Hazard Codes:?Xn,?N
Risk Statements: 22-40-51/53-63?
R22:Harmful if swallowed.?
R40:Limited evidence of a carcinogenic effect.?
R51/53:Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.?
R63:Possible risk of harm to the unborn child.
Safety Statements: 36/37-61?
S36/37:Wear suitable protective clothing and gloves.?
S61:Avoid release to the environment. Refer to special instructions / safety data sheets.
RIDADR: UN 2811 6.1/PG 3
WGK Germany: 2
HS Code: 29309070
Hazardous Substances Data: 62-56-6(Hazardous Substances Data)
- Skin, Eye, and Respiratory Irritations:
- ... Skin irritant ...
- Cleanup Methods:
- SLUDGE WAS TREATED WITH 5% AQ SOLN OF THIOUREA, SAND & PORTLAND CEMENT AT PH 12.5. LEACHING TEST OF RESULTING CONCRETE SHOWED THAT DISSOLVED CONCN OF MERCURY, CADMIUM,LEAD, COPPER, & ARSENIC WERE FAR BELOW REGULATION LEVELS.
PRECAUTIONS FOR "CARCINOGENS": A high-efficiency particulate arrestor (HEPA) or charcoal filters can be used to minimize amt of carcinogen in exhausted air ventilated safety cabinets, lab hoods, glove boxes or animal rooms. ... Filter housing that is designed so that used filters can be transferred into plastic bag without contaminating maintenance staff is avail commercially. Filters should be placed in plastic bags immediately after removal. ... The plastic bag should be sealed immediately. ... The sealed bag should be labelled properly. ... Waste liquids ... should be placed or collected in proper containers for disposal. The lid should be secured & the bottles properly labelled. Once filled, bottles should be placed in plastic bag, so that outer surface ... is not contaminated. ... The plastic bag should also be sealed & labelled. ... Broken glassware ... should be decontaminated by solvent extraction, by chemical destruction, or in specially designed incinerators. /Chemical Carcinogens/
Cover with a weak solution of calcium hypochlorite (up to 15%). Transfer into a large breaker. After 12 hours, neutralize with 6m-hydrochloric acid or 6m ammonium hydroxide, if necessary. ...
- UN 2877/2811
- Thiourea is available in the USA as a lab chemical containing 99% active ingredient. The specifications for a West German commercial product were as follows: 99% minimum active ingredient, 0.15% maximum water, 0.1% maximum ash, 0.4% maximum dicyanodiamide and traces of sulfate ion.
Grades: Technical; reagent
- Exposure Standards and Regulations:
- Substances generally prohibited from direct additiion or use as human food. a) Thiourea is the chemical thiocarbamide, CH4N2S. It is a synthetic chemical, is not found in natural products at levels detectable by the official methodology, and has been proposed as an antimycotic for use in dipping citrus. (b) Food containing any added or detectable level of thiourea is deemed to be adulterated under the act.
- Reactivities and Incompatibilities:
- The solid peroxide produced by action of hydrogen peroxide & nitric acid on thiourea (& possibly a hydrogen peroxidate of thiourea dioxide) decomposed violently on drying in air, with evolution of sulfur dioxide & free sulfur.
REACTS WITH VARIOUS SULFHYDRYL-OXIDIZING AGENTS; COMPLEXES & ADDUCTS WITH ORGANIC CMPD, PROTEIN & CERTAIN HYDROCARBONS.
Acrolein polymerizes with release of heat on contact with thiourea.
Incompatible with acrylaldehyde; hydrogen peroxide; nitric acid.
- Other Preventative Measures:
- In the case of the precursor /to aminothiazole/, thiourea, particular attention should be given to the hazard of skin absorption by the provision of protective clothing and adequate sanitary facilities incl showers.
PRECAUTIONS FOR "CARCINOGENS": Smoking, drinking, eating, storage of food or of food & beverage containers or utensils, & the application of cosmetics should be prohibited in any laboratory. All personnel should remove gloves, if worn, after completion of procedures in which carcinogens have been used. They should ... wash ... hands, preferably using dispensers of liq detergent, & rinse ... thoroughly. Consideration should be given to appropriate methods for cleaning the skin, depending on nature of the contaminant. No standard procedure can be recommended, but the use of organic solvents should be avoided. Safety pipettes should be used for all pipetting. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": ... Operations connected with synth & purification ... should be carried out under well-ventilated hood. Analytical procedures ... should be carried out with care & vapors evolved during ... procedures should be removed. ... Expert advice should be obtained before existing fume cupboards are used ... & when new fume cupboards are installed. It is desirable that there be means for decreasing the rate of air extraction, so that carcinogenic powders can be handled without ... powder being blown around the hood. Glove boxes should be kept under negative air pressure. Air changes should be adequate, so that concn of vapors of volatile carcinogens will not occur. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": Vertical laminar-flow biological safety cabinets may be used for containment of in vitro procedures ... provided that the exhaust air flow is sufficient to provide an inward air flow at the face opening of the cabinet, & contaminated air plenums that are under positive pressure are leak-tight. Horizontal laminar-flow hoods or safety cabinets, where filtered air is blown across the working area towards the operator, should never be used. ... Each cabinet or fume cupboard to be used ... should be tested before work is begun (eg, with fume bomb) & label fixed to it, giving date of test & avg air-flow measured. This test should be repeated periodically & after any structural changes. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": Principles that apply to chem or biochem lab also apply to microbiological & cell-culture labs. ... Special consideration should be given to route of admin. ... Safest method of admin of volatile carcinogen is by injection of a soln. Admin by topical application, gavage, or intratracheal instillation should be performed under hood. If chem will be exhaled, animals should be kept under hood during this period. Inhalation exposure requires special equipment. ... Unless specifically required, routes of admin other than in the diet should be used. Mixing of carcinogen in diet should be carried out in sealed mixers under fume hood, from which the exhaust is fitted with an efficient particulate filter. Techniques for cleaning mixer & hood should be devised before expt begun. When mixing diets, special protective clothing &, possibly, respirators may be required. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": When ... admin in diet or applied to skin, animals should be kept in cages with solid bottoms & sides & fitted with a filter top. When volatile carcinogens are given, filter tops should not be used. Cages which have been used to house animals that received carcinogens should be decontaminated. Cage-cleaning facilities should be installed in area in which carcinogens are being used, to avoid moving of ... contaminated /cages/. It is difficult to ensure that cages are decontaminated, & monitoring methods are necessary. Situations may exist in which the use of disposable cages should be recommended, depending on type & amt of carcinogen & efficiency with which it can be removed. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": To eliminate risk that ... contamination in lab could build up during conduct of expt, periodic checks should be carried out on lab atmospheres, surfaces, such as walls, floors & benches, & ... interior of fume hoods & airducts. As well as regular monitoring, check must be carried out after cleaning-up of spillage. Sensitive methods are required when testing lab atmospheres for chem such as nitrosamines. Methods ... should ... where possible, be simple & sensitive. ... /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": Rooms in which obvious contamination has occurred, such as spillage, should be decontaminated by lab personnel engaged in expt. Design of expt should ... avoid contamination of permanent equipment. ... Procedures should ensure that maintenance workers are not exposed. ... Particular care should be taken to avoid contamination of drains or ventilation ducts. In cleaning labs, procedures should be used which do not produce aerosols or dispersal of dust, ie, wet mop or vacuum cleaner equipped with high-efficiency particulate filter on exhaust, which are avail commercially, should be used. Sweeping, brushing & use of dry dusters or mops should be prohibited. ... Contaminated cleaning materials should not be re-used. ... If gowns or towels are contaminated, they should not be sent to laundry, but ... decontaminated or burnt, to avoid any hazard to laundry personnel. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": Doors leading into areas where carcinogens are used ... should be marked distinctively with appropriate labels. Access ... limited to persons involved in expt. ... A prominently displayed notice should give the name of the Scientific Investigator or other person who can advise in an emergency & who can inform others (such as firemen) on the handling of carcinogenic substances. /Chemical Carcinogens/
SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.
- Protective Equipment and Clothing:
- Wear rubber gloves & gas mask.
PRECAUTIONS FOR "CARCINOGENS": ... Dispensers of liq detergent /should be available./ ... In animal laboratory, personnel should remove their outdoor clothes & wear protective suits (preferably disposable, one-piece & close-fitting at ankles & wrists), gloves, hair covering & overshoes. ... Clothing should be changed daily but ... discarded immediately if obvious contamination occurs ... /also,/ workers should shower immediately. In chemical laboratory, gloves & gowns should always be worn ... however, gloves should not be assumed to provide full protection. Carefully fitted masks or respirators may be necessary when working with particulates or gases, & disposable plastic aprons might provide addnl protection. If gowns are of distinctive color, this is a reminder that they should not be worn outside of lab. /Chemical Carcinogens/
- ?Thiourea (CAS NO.62-56-6) is also named as 2-Thiopseudourea ; 2-Thiourea ; AI3-03582 ; CCRIS 588 ; Caswell No. 855 ; EPA Pesticide Chemical Code 080201 ; HSDB 1401 ; Isothiourea ; NSC 5033 ; Pseudothiourea ; Pseudourea, 2-thio- ; RCRA waste number U219 ; Sulourea ; THU ; Thiocarbamide ; Thiocarbonic acid diamide ; Thiomocovina ; Thiomocovina [Czech] ; Thiuronium ; Tsizp 34 ; USAF EK-497 ; Urea, 2-thio- ; Urea, thio- ; beta-Thiopseudourea?.?Thiourea (CAS NO.62-56-6) is white crystals or powder . It is water soluble.?Thiourea is?toxic and carcinogenic. When heated to decomposition?Thiourea emits very toxic fumes of oxides of sulfur and oxides of nitrogen. Violent exothermic polymerization reaction with acrylaldehyde (acrolein), violent decomposition of the reaction product with hydrogen peroxide and nitric acid , spontaneous explosion upon grinding with potassium chlorate. Poisonous inhaled or swallowed. Irritating to skin; may cause allergic skin eruptions.
- Octanol/Water Partition Coefficient:
- log Kow = -1.08
- Disposal Methods:
- Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number U219, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste. [
A potential candidate for rotary kiln incineration at a temperature range of 820 to 1,600 deg C and residence times of seconds for liquids and gases, and hours for solids. A potential candidate for fluidized bed incineration at a temperature range of 450 to 980 deg C and residence times of seconds for liquids and gases, and longer for solids.
The following wastewater treatment technology has been investigated for thiourea: Concentration process: Biological treatment.
PRECAUTIONS FOR "CARCINOGENS": There is no universal method of disposal that has been proved satisfactory for all carcinogenic compounds & specific methods of chem destruction ... published have not been tested on all kinds of carcinogen-containing waste. ... Summary of avail methods & recommendations ... /given/ must be treated as guide only. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": Total destruction ... by incineration may be only feasible method for disposal of contaminated laboratory waste from biological expt. However, not all incinerators are suitable. ... Most efficient type ... is probably the gas-fired type, in which a first-stage combustion with a less than stoichiometric air:fuel ratio is followed by a second stage with excess air. Some ... are designed to accept ... aqueous & organic-solvent solutions, otherwise it is necessary ... to absorb soln onto suitable combustible material, such as sawdust. Alternatively, chem destruction may be used, esp when small quantities ... are to be destroyed in laboratory. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": HEPA (high-efficiency particulate arrestor) filters ... can be disposed of by incineration. For spent charcoal filters, the adsorbed material can be stripped off at high temp & carcinogenic wastes generated by this treatment conducted to & burned in an incinerator. ... LIQUID WASTE: ... Disposal should be carried out by incineration at temp that ... ensure complete combustion. SOLID WASTE: Carcasses of lab animals, cage litter & misc solid wastes ... should be disposed of by incineration at temp high enough to ensure destruction of chem carcinogens or their metabolites. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": ... Small quantities of ... some carcinogens can be destroyed using chem reactions ... but no general rules can be given. ... As a general technique ... treatment with sodium dichromate in strong sulfuric acid can be used. The time necessary for destruction ... is seldom known ... but 1-2 days is generally considered sufficient when freshly prepd reagent is used. ... Carcinogens that are easily oxidizable can be destroyed with milder oxidative agents, such as sat soln of potassium permanganate in acetone, which appears to be a suitable agent for destruction of hydrazines or of compounds containing isolated carbon-carbon double bonds. Concn or 50% aqueous sodium hypochlorite can also be used as an oxidizing agent. /Chemical Carcinogens/
PRECAUTIONS FOR "CARCINOGENS": Carcinogens that are alkylating, arylating or acylating agents per se can be destroyed by reaction with appropriate nucleophiles, such as water, hydroxyl ions, ammonia, thiols & thiosulfate. The reactivity of various alkylating agents varies greatly ... & is also influenced by sol of agent in the reaction medium. To facilitate the complete reaction, it is suggested that the agents be dissolved in ethanol or similar solvents. ... No method should be applied ... until it has been thoroughly tested for its effectiveness & safety on material to be inactivated. For example, in case of destruction of alkylating agents, it is possible to detect residual compounds by reaction with 4(4-nitrobenzyl)-pyridine. /Chemical Carcinogens/
Use and Manufacturing
- Use and Manufacturing:
- Methods of Manufacturing
Production of thiourea is now carried out by treating technical-grade calcium cyanamide with hydrogen sulfide or one of its precursors, e.g., ammonium sulfide or calcium hydrogen sulfide. The calcium cyanamide must contain at least 23% nitrogen and must be free from calcium carbide, /or/ explosive acetylene is liberated by water or hydrogen sulfide.
In Germany, thiourea is produced in a closed system by reaction of calcium cyanamide with hydrogen sulfide ... A reaction vessel is charged continuously with an aqueous suspension of calcium cyanamide and a mixture of hydrogen sulfide and carbon dioxide ... The converted reaction mixture is removed continuously from the reactor and excess H2S is removed by stripping. Waste-gas from the reactor contains hydrogen sulfide, which is purified in a scrubber connected to the reactor. The stripped thiourea solution is filtered to remove the precipitated calcium carbonate formed as one of the reaction products. The filtrate is evaporated in vacuum and thiourea is crystallized by cooling. It is filtered, washed, and dried in an air stream.
Made by fusing ammonium thiocyanate: Powers and Powers, Mitchchell, US 2552584; US 2560596 (both 1951 to Koppers); by treating cyanamide with hydrogen sulfide: Robin, Jr., US 2173067 (1940 to Am. Cyanamid); Lewis, US 2393917 (1946 to Monsanto); Van de Kamp, US 2357149 (1944 to Merck & Co.).
DERIVATION: (1) By heating dry ammonium thiocyanate, extraction with a concentrated solution of ammonium thiocyanate, with subsequent crystallization; (2) action of hydrogen sulfide on cyanamide.U.S. Production
(1991) Exceeded 5000 lb or US $5000 in value
Thiourea is listed as a High Production Volume (HPV) chemical (65FR81686). Chemicals listed as HPV were produced in or imported into the U.S. in >1 million pounds in 1990 and/or 1994. The HPV list is based on the 1990 Inventory Update Rule. (IUR) (40 CFR part 710 subpart B; 51FR21438).
Production volumes for non-confidential chemicals reported under the Inventory Update Rule. Year Production Range (pounds) 1986 >1 million - 10 million 1990 >1 million - 10 million 1994 >1 million - 10 million 1998 >1 million - 10 million 2002 >500 thousand - 1 million
- Photographic fixing agent and to remove stains from negatives, manufacture of resins, vulcanization accelerator, a reagent for bismuth, selenite ions.
Biomedical Effects and Toxicity
- Pharmacological Action:
- - Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)
- Therapeutic Uses:
- Thiourea had a former use in the treatment of excessive thyroid gland activity. The doses of thiourea recommended vary considerably. Originally, a dose of 2-3 g daily was used, especially as an initial dose. This was later reduced because of the associated side-effects. The side-effects of thiourea have been described from observations of the former therapeutic use of thiourea in the 1940s as a thyroid depressant. Forty-nine (i.e., 9.3%) of 525 patients who were treated with thiourea suffered from one or more of the following side-effects as specified by the respective number of individual cases quoted in parentheses: agranulocytosis (1), leukopenia (4), elevated temperature (24), erythema (9), swollen lymph nodes (1), pains in muscles and joints (4), gastrointestinal disorders (17), and various other symptoms. Elevated temperature was observed almost immediately after commencement of the therapy and regressed upon its termination. Both attacks of feverishness, which occur within 7-14 days after the onset of the therapy, and skin reactions have been attributed to sensitization.
- Biomedical Effects and Toxicity:
- WHEN (35)SULFUR LABELLED CMPD WAS GIVEN BY IP INJECTION TO RATS 98% OF ADMIN RADIOACTIVITY APPEARED IN URINE WITHIN 48 HR AFTER INJECTION. CHROMATOGRAPHY OF THE URINE SHOWED THAT MAJOR PRODUCT WAS UNDEGRADED THIOUREA, WITH SMALL QUANTITIES OF INORGANIC SULFATE (6.2%) & ETHEREAL SULFATE (5.9%).
... SMALL AMT (1.95% OF THE IP ... DOSE) OF (35)SULFUR LABELLED THIOUREA WAS CONCN IN THYROID OF RATS. MOST OF (35)SULFUR IN THE GLAND WAS PRESENT AS SULFATE (56%) OR BOUND TO PROTEIN (13%) ... IN SERUM, 75% OF THE (35)SULFUR LABEL OCCURRED AS THIOUREA & 15% AS SULFATE. ... (35)SULFUR THIOUREA READILY CROSSES THE RAT PLACENTA, & THE FETAL THYROID:FETAL SERUM CONCN RATIO ... ELEVATED ABOVE 1 ON THE 17TH DAY OF GESTATION & CONTINUED TO INCREASE UNTIL THE 20TH DAY.
PHARMACOKINETIC STUDY OF (14)CARBON THIOUREA IN RAT ... REVEALED THAT PARENT CMPD &/OR A METABOLITE IS BOUND SELECTIVELY TO PROTEIN IN LIVER, KIDNEY, & LUNG.
(14)carbon labeled thiourea was given iv or orally to rats at a low (0.16 mg/kg) or high (160 mg/kg) dose. Following iv admin, the radioactive label was covalently bound to macromolecular fractions such as proteins or peptides. The elimination of thiourea from plasma was greatly delayed following the high iv dose (half-life beta 7.0 hr) as compared with that after the low dose (high-life beta 0.69 hr). After the low dose, very high radioactivity was present in the lung, thymus and Harder's gland at 60 min following iv admin, whereas when the high dose was admin the radioactivity was distributed almost homogeneously throughout the body. [Hirate J et al; Chem Pharm Bull 30 (9): 3319-27 (1982)] PubMed Abstract
The whole blood levels and whole-body autoradiography following iv admin of thiourea which is considered to covalently bind to the macromolecules in the body, were investigated in 1 day old, 1 wk old, 3 wk old and 8 wk old mice in order to clarify the change of disposition kinetics accompanied by growth. The total body clearance for thiourea was remarkably lower in 1 day old and 1 wk old mice than in more aged mice. The lower metabolic clearance as well as renal clearance in 1 day old and 1 wk old mice seemed to be responsible for this observation. The whole body autoradiograms obtained at 60 min following iv admin of (14)carbon labeled thiourea showed the homogeneous distribution of radioactivity throughout the body in 1 day old and 1 wk old mice, but highly localized radioactive areas in the liver and lung of more aged mice. This remarkable difference was assumed to be brought about by the difference in quantity of the macromolecules in the liver and lung which can covalently bind with thiourea. This assumption was supported by gel filtration of lung and liver homogenates on Sephadex G-10. [Hirate J et al; J Pharmacobio-Dyn 6 (5): 323-30 (1983)] PubMed Abstract
... WORKERS HANDLING THIOUREA PRODUCTS SHOWED READY PENETRATION THROUGH SKIN ...
Environmental Fate and Exposure Potential
- Environmental Fate/Exposure Summary:
- TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 3(SRC), determined from a log Kow of -1.08(2) and a regression-derived equation(3), indicates that thiourea is expected to have very high mobility in soil(SRC). Volatilization of thiourea from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 2.0X10-9 atm-cu m/mole(SRC), derived from its vapor pressure, 2.8X10-3 mm Hg(4), and its water solubility, 1.42X10+5 mg/L(5). Thiourea is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(4). Thiourea was shown to degrade in soil by both chemical and microbial degradation, although high levels of thiourea may suppress microflora activity for extended periods of time(6), suggesting that biodegradation is not an important environmental fate process in soil(SRC).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 3(SRC), determined from a log Kow of -1.08(2) and a regression-derived equation(3), indicates that thiourea is not expected to adsorb to suspended solids and sediment in water(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 2.0X10-9 atm-cu m/mole(SRC), derived from its vapor pressure, 2.8X10-3 mm Hg(4) and water solubility, 1.42X10+5 mg/L(8). According to a classification scheme(5), a BCF of
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), thiourea, which has an extrapolated vapor pressure of 2.8X10-3 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase thiourea is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 3 hours(SRC), calculated from its rate constant of 4.2X10-11 cu cm/molecule-sec at 25 deg C(3) determined using a structure estimation method(3). In methanol solution, the ultraviolet absorption spectrum shows weak absorption from 290 to 310 nm with no absorption above 310 nm(5) suggesting a potential for direct photolysis(SRC). The GSF Test for photochemical degradation resulted in only a 0.23% thiourea degradation(4). Thiourea, adsorbed on silica gel and irradiated with light, resulted in 4.7% degradation(6).
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