This reagent discolours cellulose acetate butyrates but one cellulose acetate.
Distillation with syrupy phosphoric acid will split off acetic, pro pionic, and
other volatile acids from combination in resins. steam destillation is advisable,
and the method may be made quantitative by following the method on p. 280.
Fusion with sodium or with Na OH produced sodium thiocyanate
(which gives a red colour with ferric chloride ) if thiourea resins, are
present.
NITRATION OF PHENOLS :
Alittle resin is biled with cone. HNO3, and the reaction mixture steam distilled,
yielding 0-nitrophenol, a yellow solid dessolving in Na OH solution to an intense orange
colour; m.p. 45 deg. C.
(N.B. potassium and ammonium pocrates are explosive when dry.)
The solution from acid hydrolysis, of certain resins may be used to produce characteristic
picrates, identifiable by their melting points after rec rysteristic Coumarone piccrate:
m.p. 102 103 deg.c. indene picrate, m.p. 98 deg. c. melamine : m.p. 312 325 deg.c. candlin
(J.S.D.C. 1947 p. 144) gives the following method for melamine /formaldehyde finishes. add
5 cms. resin to 250 c.c. dilute H2SO4 warm to 70 deg. c. add solid potassium permanganate
until there is no further decolorisation,filter to remove mno2 and carbonaceous matter,
just decolorise the filtrate, add escess na Oh to precipitate dissolved mn, boil, filter,
make neutral with H2 SO4, add excess of saturated aqueous picric acid, when the melamine
picrate is precipitated. ( N.B. the solubility of melamin ein water is rather low.
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