Formaldehyde preparation from paraformaldehyde

Formaldehyde freshly prepared from paraformaldehyde powder, in 0.1Mcacody-late buffer, pH 7.2, or 2% paraformaldehyde + 0.1% glutaraldehyde in 0.1Mcacody-late buffer, pH 7.2. 

Tissue specimens are fixed with 4% formaldehyde (freshly prepared from paraformaldehyde) for 12-18 hr at 4°C, and embedded in Epon (Groos et al., 2001). 

The primary fixative was a mixture of 3% glutaraldehyde, 1% formaldehyde freshly prepared from paraformaldehyde, and 0.75% tannic acid in 0.05 M piperazine-N,N -bis(2-ethanesulfonic acid) (PIPES) buffer, pH 7.0. As tannic acid may lower the pH of the fixative, it is recommended that this is checked before use and adjusted to 7.0 with 1N NaOH if necessary. The addition of low-molecular weight tannic acid to the primary fixative consistently improves the preservation of membranes and microtubules.2... 

For immunostaining formaldehyde should be freshly prepared from paraformaldehyde powder or purchased as an EM grade aqueous paraformaldehyde solution sealed in ampoules under nitrogen. 

Formaldehyde should either be freshly prepared from paraformaldehyde or purchased as a purified solution (see Note 2). 

Commercial preparations of formaldehyde (a gas that dissolves in liquid) are stabilized by additives such as methanol, or are packaged in ampoules under nitrogen and are thus fairly costly. For most fixation procedures, it is preferable to make formaldehyde fresh from paraformaldehyde on the day it will be used. 

Formaldehyde, freshly prepared from paraformaldehyde (Section III,A) 2X SSCT (0.3 M NaCl, 0.03 M Na citrate, 0.1% Tween-20)... 

Special preparations invoKing formaldehyde are also employed as deodorants. A patented deodorant powder is prepared from paraformaldehyde, hexamethylenetetramine, a powdered emollient material, and ammonium chloride .. According to a Biitish process, cakes or balls for disinfecting and deodorizing am formed from mixtures containing paraformaldehyde, rice flour, pine-needle oil, potassium permanganate, etc. ... 

Formals and acetals prepared from the reaction of polynitroaliphatic alcohols with formaldehyde and acetaldehyde have found use as explosive plastisizers for nitrocellulose and in plastic bonded explosives (PBXs). Formals of polynitroaliphatic alcohols are commonly prepared via reaction with trioxane or paraformaldehyde in the presence of sulfuric acid as a condensing agent. Bis(2,2-dinitropropyl)formal (175) is prepared from the reaction of trioxane with 2,2-dinitropropanol (25). The reaction of 2,2,2-trinitroethanol (159) and 2,2-dinitro-l,3-propanediol (19) with formaldehyde in the presence of sulfu-... 

Preparation of cyclonite from hexamine. ntlrtc acid and ammonium nitrate 3. Preparation of cyclonite from sulphamic acid, formaldehyde and nitric acid 4 Preparation of cyclonite from paraformaldehyde, amtrumtum nitrate and acetic anhydride... 

Technical grade metal hexacarbonyls (96-98%) are suitable. While 1,3,5-trimethyl- 1,3,5-triazacyclohexane (1,3,5-trimethylhexahydro-1,3,5-triazine) is commercially available, it is also conveniently prepared from aqueous methyl-amine and aqueous formaldehyde solution or paraformaldehyde following the method of Graymore and purified by distillation (60-61°C at 12mmHg).n... 

Prins reactions with formaldehyde have been used to prepare prostaglandin intermediates. Reaction of norbomadiene with paraformaldehyde and formic acid at -80 °C gives (6) in 67% yield (equation 3). Reaction of unsaturated lactone (7) with formaldehyde in acetic acid at 60-80 C gives prostaglandin intermediate (8) in 75-85% yield (equation 4). Addition of protonated formaldehyde occurs from the less-hindered face of the double bond followed by trans addition of acetate to the carbocation. 

Ca. 5% excess dry paraformaldehyde added in small portions with occasional cooling to gently refluxing ethereal p-tolyllithium prepared from p-iodotoluene and lithium, stirring continued 10-15 min. p-methylbenzyl alcohol. Y 95%. — It is not necessary to prepare monomeric formaldehyde from the paraformaldehyde. F. e., also C-hydroxymethylation of acetylene derivatives, s. A. Schaap, L. Brandsma, and J. F. Arens, R. 8A, 1200 (1965). 

In the preparation of high molecular weight polyformaldehyde the initial operation consists of the production of pure formaldehyde, free from low molecular weight polymers and other hydroxy compounds which cause chain transfer and termination. In a typical process [4, 5] potassium hydroxide-precipitated paraformaldehyde (degree of polymerization approximately 200) is carefully washed with water and dried for several hours in vacuo at 80°C. The dried polymer is then decomposed in nitrogen at 150—160°C the product is passed through several traps at —15°C to remove water, glycols, and other... 

Gaseous formaldehyde from dried paraformaldehyde passed into a stirred ethereal suspension of K-diphenylmethide (prepared from equimolar amounts... 

Numerous methylene aceuds, especially of sugar alcohols, have been prepared [126] by treating glycols with formaldehyde in the presence of an acid catalyst. Condensations have often been effected in 40% aqueous formaldehyde solution, but paraformaldehyde and polyoxymethylene have 2dso been used as formaldehyde sources [127]. In a few cases, methylene acetals have been prepared under basic conditions from glycols and CH2Br2—NaH in dimethylformamide solution [130]. 

Do not use commercial formaldehyde for histological preparations as it is unstable. Prepare formaldehyde from paraformaldehyde and store as a 20% stock at 4 C for 1-2 weeks, depending on the preparation. 

Formaldehyde (37%) prepared fresh from paraformaldehyde Liquid nitrogen in a Dewar flask, or an aluminum block on dry ice, to freeze slides Ethanol (95%), chilled to -20°C in a Coplin jar or other slide-staining container 2x SSCT (see p. 43)... 

We recommend freshly preparing tlie formaldehyde from paraformaldehyde powder (reagent grade). Liquid 37 % formaldehyde solutions ( formalin ) contain methanol as stabilizing reagent, which quickly leads to a loss of GFP fluorescence even when highly diluted. 

---