formaldehyde - Sciencemadness Dot Org

USES OF FORMALDEHYDE 341
that a reaction product of formaldehyde with pyrogallol in the »re.si-nce *A
an acid catalyst precipitates glue from solution and behaves somewhat like
a tannin was reported by Baeyer 1 in 1S727 but the product wa^ apparently
not evaluated as a tanning agent at that time.
Most of the syntans which have been prepared since Stiasny s disco vei-y
have been sulfonic-aeid derivatives; and considerable study has wen given
to the effect of different methods of synthesis, variations in .-ubstituent
groups, and other modifications. Although generally used as free acid?,
neutral syntans are also employed. "Whereas mineral acid- may cause
trouble in tanning, this is not true of the acidic syntans. A~ a result, it
has been found desirable to remove free mineral acids from the=e products,
The effect of variations in methods of synthesis has been studied in considerable
detail by Wolesensky 40 , who points out that products obtained from
sulfonated phenols and formaldehyde have little or no filling action, whereas
syntans with filling properties are obtained when the preformed phenolformaldehyde
condensates are sulfonated. He also demons! rates ss that
non-phenolic compounds such as the condensation product of toluene
sulfonic acid and formaldehyde show little or no tanning action.
It is impossible to give exact information concerning the chemical structure
and synthesis of the syntans which are now actually in use. However,
examination of the patent literature indicates that» in addition to the more
traditional syntan types, considerable attention has also been given in
recent years to nitrogenous products prepared by reactions involving urea,
thiourea, amines, etc. Geigy 5 produces water-soluble products hy the action
of concentrated sulfuric acid on phenols in the presence of urea, condenses
these with formaldehyde and aromatic hydroxy carboxylic acids in
strong sulfuric acid, and neutralizes the resulting materials. Somerville
and Reterink 25 react phenolsulfonic acid with formaldehyde in the presence
of thiourea. Hassler v condenses a sulfonated phenol with formaldehyde
in the presence of ammonia or an alkylamine. Swain and Adams 28 treat
sulfonated phenols or sulfonated aromatics with formaldehyde and melamine.
Miscellaneous Uses of Formaldehyde in the Leather and Hide Industry.
The preservative and disinfecting action of formaldehyde is also employed
in the leather industry. For example, it is stated that extensive deterioration
of skins may be avoided by treating with formaldehyde prior to lime
pit or tanner's pit processes 10 . Treatment of raw calf hide with solutions
containing 1 to 2 per cent formaldehyde alone or with 8 per cent sodium
chloride plus 0,1 per cent soda His bacteria, but is reported to make soaking
diffioult after storage and to prevent easy unhairing. This undesirable
effect is reduced when soda is omitted from the solution 23 .
Formaldehyde feds use in the treatment of fur or hair. For example, it