Solubility Paraformaldehyde

It is marketed as a 35-40 per cent, solution in water (formalin). The rpactions of formaldehyde are partly typical of aldehydes and partly peculiar to itself. By evaporating an aqueous solution paraformaldehyde or paraform (CHjO), an amorphous white solid is produced it is insoluble in most solvents. When formaldehyde is distilled from a 60 per cent, solution containing 2 per cent, of sulphuric acid, it pol5unerises to a crystalline trimeride, trioxane, which can be extracted with methylene chloride this is crystalline (m.p. 62°, b.p. 115°), readily soluble in water, alcohol and ether, and devoid of aldehydic properties ... 

Cellulose dissolved in suitable solvents, however, can be acetylated in a totally homogeneous manner, and several such methods have been suggested. Treatment in dimethyl sulfoxide (DMSO) with paraformaldehyde gives a soluble methylol derivative that reacts with glacial acetic acid, acetic anhydride, or acetyl chloride to form the acetate (63). The maximum degree of substitution obtained by this method is 2.0 some oxidation also occurs. Similarly, cellulose can be acetylated in solution with dimethylacetamide—paraformaldehyde and dimethylformamide-paraformaldehyde with a potassium acetate catalyst (64) to provide an almost quantitative yield of hydroxymethylceUulose acetate. 

Formaldehyde is a colorless gas that is soluble in water (3). Commercial aqueous preparations of formalin contain 37 0% w/w solubilized gas. They also contain formic acid (<0.05%) and 10-15% methanol, which is added to prevent the polymerization of formaldehyde into paraformaldehyde (3,11). Methanol and formic acid make these solutions an unacceptable fixative for fine structures (9). Paraformaldehyde is a polymerized form of formaldehyde that dissociates at 60°C and neutral pH. Freshly prepared solutions of paraformaldehyde are preferred for most immunochemical procedures because they provide a fixative free of extraneous additives and are usually the conservative fixatives of choice when beginning the development of a fixation protocol (3,5). 

FORMALDEHYDE. CAS 50-00-0], HCHO. formula weight 30.03. colorless gas with pungent odor, mp — 92 C, bp -2 °C, sp gr 0.815 (at —20"C). The gas is very soluble in H2O. alcohol, and ether. Formaldehyde usually is produced and marketed as a 37% (weight) solution in water. From 3 to 15% methyl alcohol normally is added as a stabilizer 10 prevent paraformaldehyde formation. The commercial trend is 10 furnish a more concentrated product (up 10 50% HCHO hy weight) which contain as... 

HEXAMINE. CAS 100-97-0], (CH-),N . formula weight 140,19, white crystalline solid, mp 280rC. decomposes at higher temperatures. Alsu known as hexamethylenetetramine, nicihenuiniiie. and urotiopitie. the compound is soluble in H2O and only very slightly soluble in alcohol or ether. Although used to some extent in medicine as an internal antiseptic, the primary use of hexamine is in the manufacture of synthetic resins where the compound is a substitute for formalin (aqueous solution of paraformaldehyde) and its NaOH catalyst. Hexamine also is used as an accelerator for rubber. 

Alkali is not capable of dissolving native cellulose. Only depolymerized cellulose fragments with a low degree of polymerization are alkali soluble. Certain quaternary ammonium compounds are more effective resulting in full solubility, A mixture of dimethyl sulfoxide and paraformaldehyde (DMSO-PF) has interesting properties as a cellulose solvent. However, its effect depends at least partly on the formation of a hydroxymethylcellulose derivative. The most important cellulose solvents are metal complexes of... 

Paraformaldehyde is a white crystalline powder with an odor of formaldehyde. It is slowly soluble in cold water, and more readily soluble in hot water with evolution of formaldehyde. It is insoluble in alcohol, and ether. Keep paraformaldehyde in tightly sealed bottles. Paraformaldehyde is prepared by the polymerization of formaldehyde, and is commercially available. 

Glacial acetic acid, acetyl chloride, and acetic anhydride have been compared as acetylating agents for solutions of cellulose in dimethylsulphoxide-paraformaldehyde. Mixtures of pyridine and acetic anhydride were demonstrated to acetylate the cellulose rapidly to yield beige to amber acetone-soluble cellulose acetates which were partially oxidized. These thermoplastic resins exhibited softening points between 80 and 110 °C and thermal stabilities similar to those of native cellulose. 

U/F resins get their name from their main ingredients urea and formaldehyde. Both are soluble in water urea, a white crystalline solid melting at 133" C, to the extent of 80 g in 100 g of water, while formaldehyde is usually supplied as the 37 per cent aqueous solution, formalin , or the solid, paraformaldehyde. Paraform is the condensation homopolymer produced by evaporating formalin ... 

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