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A saturated water solution, of about 40% formaldehyde by volume or 37% by mass, is called "100% formalin". A small amount of stabilizer, such as methanol, is usually added to suppress oxidation and polymerization. A typical commercial-grade formalin may contain 10–12% methanol in addition to various metallic impurities.
As a salt of a weak acid (formic acid) and a strong base (sodium hydroxide) sodium formate reacts in aqueous solutions basic: + + A solution of formic acid and sodium formate can thus be used as a buffer solution.
Although available commercially, the salt can be prepared from sodium dithionite and formaldehyde: . Na 2 S 2 O 4 + 2 CH 2 O + H 2 O → HO-CH 2-SO 3 Na + HO-CH 2-SO 2 Na. This reaction proceeds quantitatively, such that dithionite can be determined by its conversion to Rongalite, which is far less O 2-sensitive and thus easier to handle.
In organic chemistry, the Mannich reaction is a three-component organic reaction that involves the amino alkylation of an acidic proton next to a carbonyl (C=O) functional group by formaldehyde (H−CHO) and a primary or secondary amine (−NH 2) or ammonia (NH 3). [1] The final product is a β-amino-carbonyl compound also known as a Mannich base.
If the two solutions have hydrogen ions and hydroxide ions as the counterions, they will react with one another in what is called an acid–base reaction or a neutralization reaction to form water. [12] Alternately the counterions can be chosen to ensure that even when combined into a single solution they will remain soluble as spectator ions. [11]
Aldehydes (except those without an alpha carbon, or without protons on the alpha carbon, such as formaldehyde and benzaldehyde) can exist in either the keto or the enol tautomer. Keto–enol tautomerism is catalyzed by either acid or base. In neutral solution, the enol is the minority tautomer, reversing several times per second. [15]
At 25 °C (77 °F), solutions of which the pH is less than 7 are acidic, and solutions of which the pH is greater than 7 are basic. Solutions with a pH of 7 at 25 °C are neutral (i.e. have the same concentration of H + ions as OH − ions, i.e. the same as pure water). The neutral value of the pH depends on the temperature and is lower than 7 ...
The solution is expected to be neutral only when K a = K b. [12] Other possible factors that could vary pH level of a solution are the relevant equilibrium constants and the additional amounts of any base or acid. For example, in ammonium chloride solution, NH + 4 is the main influence for acidic solution.