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FORMALIN, or FORMALDEHYDE, CH2O

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Originally appearing in Volume V10, Page 667 of the 1911 Encyclopedia Britannica.
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FORMALIN, or FORMALDEHYDE, CH2O or H•CHO, the first member of the See also:series of saturated aliphatic See also:aldehydes. It is most readily prepared by passing the vapour of methyl See also:alcohol, mixed with See also:air, over heated See also:copper or See also:platinum. In See also:order to collect the formaldehyde, the vapour is condensed and absorbed, either in See also:water or alcohol. It may also be obtained, although only in small quantities, by the See also:distillation of See also:calcium formate, At See also:ordinary temperatures formaldehyde is a See also:gas possessing a pungent See also:smell; it is a strong antiseptic and disinfectant, a 40% See also:solution of the aldehyde in water or methyl alcohol, sold as formalin, being employed as a deodorant, fungicide and preservative. It is not possible to obtain the aldehyde in a pure See also:condition, since it readily polymerizes. It is a strong reducing See also:agent; it combines with See also:ammonia to See also:form hexamethylene tetramine, (See also:CH2)6N4, and easily " condenses " in the presence of many bases to produce compounds which apparently belong to the sugars (q.v.). It renders See also:glue or See also:gelatin insoluble in water, and is used in the See also:coal-See also:tar See also:colour See also:industry in the manufacture of See also:para-rosaniline, pyronines and rosamines. Several polymers have been described. Para formaldehyde, or trioxymethylene, obtained by concentrating solutions of form-aldehyde in vacuo, is a See also:white crystalline solid, which sublimes at about too° C. and melts at a somewhat higher temperature, changing back into the See also:original form. It is insoluble in See also:cold water, alcohol and See also:ether. A diformaldehyde is supposed to See also:separate as white flakes when the vapour is passed into See also:chloroform (Korber, Pharm. Zeit., 1904, xlix. p.

609); F. See also:

Auerbach and H. Barschall (Chem. Zentr., 1907, H. p. 1734) obtained three polymers by acting with concentrated sulphuric See also:acid on solutions of formaldehyde, and a See also:fourth by See also:heating one of the forms so obtained. The strength of solutions of formaldehyde may be ascertained by the addition of excess of See also:standard ammonia to the aldehyde solution (hexamethylene tetramine being formed), the excess of ammonia being then estimated by titration with standard acid. On the formation of formaldehyde by the oxidation of methane at high temperatures, see W. A. See also:Bone (Journ. Chem. See also:Soc.,' 1902, 81, p. 535; 1903, 83, p.

1074). Form-aldehyde also appears to be a reduction product of See also:

carbon dioxide (see See also:Annual Reports of the Chemical Society).

End of Article: FORMALIN, or FORMALDEHYDE, CH2O

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