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Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a chemical compound with the chemical formula (CNOH)3. Like many industrially useful chemicals, this triazine has many synonyms. This white, odorless solid finds use as a precursor or a component of , disinfectants, and . In 1997, worldwide production was 160 000 .Klaus Huthmacher, Dieter Most "Cyanuric Acid and Cyanuric Chloride" Ullmann's Encyclopedia of Industrial Chemistry" 2005, Wiley-VCH, Weinheim. doi 10.1002/14356007.a08 191
Cyanuric acid is noted for its strong interaction with melamine, forming insoluble melamine cyanurate. This interaction locks the cyanuric acid into the tri-keto tautomer. Melamine cyanurate is cited as an example of supramolecular chemistry.
CYA crystallizes from water as the dihydrate.
Cyanuric acid can be produced by hydrolysis of crude or waste melamine followed by crystallization. Acid waste streams from plants producing these materials contain cyanuric acid and on occasion, dissolved amino-substituted triazines, namely, ammeline, ammelide, and melamine. In one method, an ammonium sulfate solution is heated to the "boil" and treated with a Stoichiometry amount of melamine, by which means the cyanuric acid present precipitates as melamine-cyanuric acid complex. The various waste streams containing cyanuric acid and Amine-substituted may be combined for disposal, and during upset conditions undissolved cyanuric acid may be present in the waste streams.
As temperature exceeds 190 °C, other reactions begin to dominate the process.
The first appearance of ammeline occurs prior to 225 °C and is suspected also to occur from decomposition of biuret but is produced at a lower rate than that of CYA or ammelide.
Melamine, C(NH2)N3, formation occurs between 325–350 °C and only in very small quantities.
This species is typically converted to its sodium salt, sodium dichloro-s-triazinetrione. Further chlorination gives trichloroisocyanuric acid, C(O)NCl3.
These N-chloro compounds serve as disinfectants and Algaecide for swimming pool water. The aforementioned equilibrium stabilizes the chlorine in the pool and prevents the chlorine from being quickly consumed by sunlight.
The experimental antineoplastic drug teroxirone (triglycidyl isocyanurate) is formed by reacting cyanuric acid with 3 equivalents of epichlorohydrin. It works by cross-linking DNA.M. Budnowski, Angew. Chem., 7, 827 (1968).
However, when cyanuric acid is present together with melamine (which by itself is another low-toxicity substance), it will form an Solubility and rather nephrotoxic complex, "Melamine and Cyanuric Acid Interaction May Play Part in Illness and Death from Recalled Pet Food" , American Veterinary Medical Association (AVMA), Press Release, May 1, 2007. Accessed 2008-09-27. as evidenced in dogs and cats during the 2007 pet food contamination and in children during the 2008 Chinese milk scandal cases.
Precursors to crosslinking agents
Because of its trifunctionality, CYA is a precursor to Cross-link, especially for polyurethane resins and polyisocyanurate thermoset plastics.
Analysis
Testing for cyanuric acid concentration is commonly done with a turbidometric test, which uses a reagent, melamine, to precipitate the cyanuric acid. The relative turbidity of the reacted sample quantifies the CYA concentration. Referenced in 1957, this test (dead link 8 April 2018) works because melamine combines with the cyanuric acid in the water to form a fine, white precipitate of the insoluble complex melamine cyanurate that causes the Colloid in proportion to the amount of cyanuric acid in it. More recently, a sensitive method has been developed for analysis of cyanuric acid in urine.Panuwet P, Wade EL, Nguyen JV, Montesano MA, Needham LL, Barr DB. Quantification of cyanuric acid residue in human urine using high performance liquid chromatography-tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2010 878(28):2916-2922.
Animal feed
FDA permits a certain amount of cyanuric acid to be present in some non-protein nitrogen (NPN) additives used in animal feed and drinking water. Cyanuric acid has been used as NPN. For example, Archer Daniels Midland manufactures an NPN supplement for cattle, which contains biuret, triuret, cyanuric acid and urea.
2007 pet food recalls
Cyanuric acid is implicated in connection to the 2007 pet food recalls, the contamination and wide recall of many brands of cat and dog foods beginning in March 2007. Research has found evidence that cyanuric acid, a constituent of urine, together with melamine forms poorly soluble crystals which can cause kidney failure (see Analysis section above).
Safety
Cyanuric acid is classified as "essentially nontoxic". The 50% oral median lethal dose (LD50) is 7700 mg/kg in rats.U.S. Food and Drug Administration, "Interim Melamine and Analogues Safety/Risk Assessment; Availability", Federal Register: May 30, 2007 (Volume 72, Number 103). Accessed 2008-09-27.
Natural occurrence
An impure copper salt of the acid, with the formula Cu(C3N3O3H2)2(NH3)2, is currently the only known isocyanurate mineral, called joanneumite. It was found in a guano deposit in Chile. It is very rare.Mindat, http://www.mindat.org/min-42755.html
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