formaldehyde - Sciencemadness Dot Org

REACTIONS WITH HYDROXY COMPOUNDS 143
The temperature of gelatinization of potato starch is reported to decrease
on treatment with formaldehyde. The magnitude of this effect increases
with the concentration of formaldehyde employed in the treating solution
and with the duration of its action 45 . A 38 percent formaldehyde solution
pauses gelatinization after two days, even at as low a temperature as
15-16°C. On heating, the reaction takes place rapidly. Starch treated
with formaldehyde in this way loses its characteristic property of giving a
Hue color with iodine 35 . Woker claims that formaldehyde acts like a
diastase causing the hydrolysis of starch to sugar 41 - 42 ' 71 - 72 ' 73 . However,
her conclusions have been contested by other investigators 34 - 35 - 48 - 70 , who
have demonstrated that starch can be recovered unchanged from formaldehyde-starch
reaction products on heating or on reacting with a formaldehyde
acceptor, such as ammonia, ammonium acetate, or phenyl hydrazine,
The simple formaldehyde-starch complexes of the type described in the
above paragraph are colorless powders which are comparatively stable to
heat. They may or may not form gels, depending on the method of
preparation* Their production does not involve the use of acid catalyst,
although in some cases 5 dilute alkalies are employed. Their use in antiseptic
surgical dressings has been suggested by Classen 11,12 and others 25 ' 52 .
In most instances, these compounds are probably hemiacetals of formaldehyde.
Highly stable water-resistant formaldehyde-starch compounds can be
obtained by the use of acidic catalysts. Stolle and Kopke 59 have prepared
a compound of this type in which the starch is treated with formaldehyde
at a low temperature in the presence of a rather concentrated acid. Leuck 38
obtains a water-resistant product by dehydrating starch to remove all
adsorbed water plus some water of hydration and reacting this material
with formaldehyde and acid. Similar results are also achieved by treating
the starch with alkali before reacting with formaldehyde 39 . Products
obtained under acid conditions are probably formals or cross-linked polyformals.
Resins are obtained by heating formaldehyde and starch under various
conditions. A rubber-like product is claimed on heating starch and formaldehyde
at 150-175°F under pressure in the presence of metallic magnesium 4 .
Alkali-treated starch that has been reacted with formaldehyde under acidic
conditions acts as an adhesive when subjected to heat and pressure 15 .
Cellulose. Although considerable research has been carried out on the
industrial utilization of formaldehyde for the modification of paper, rayon,
cotton, and other cellulosic materials, the study of the chemistry of its
reaction with cellulose has received comparatively little attention.
Reaction with formaldehyde in the presence of alkalies causes temporary
alterations in the physical characteristics of cellulose; but it is apparent