Tuesday, January 4, 2011

SULPHURIC ACID TEST :


Some fabric is heated with 20% H2 so4; cool dilute, diazotise by
addition of a little sodium nitrite, couple with alkaline Rsalt solution : 
red indicates aniline from aniline formaldehyde resins. some of 
the above uniazotised solution is steam destilled into liebermann storch reagent; 
return of coloul may indicate a urea formaldehyde resin.

Fuse a little cloth with na OH, extract with water , add to about IO
c.c. of extract, two drops of a I% suspension in water of dinrom- quinone 
chlorimide; add oI % naOH solution drop by drop to ph 9.4; blue purple 
indicates phenols, cresols , xylenols and their p-tert- alkyl derivaties.

The fabtic is steeped for one hour in a saturated aqueous solution of the resgent, 
then for fifteen minutes in 20 vol. hydrogen peroxide:
mauve- brown indicates cellulose fibres and urea formaldehude resins; 
yellow indicates thermoplastic resins.


Alittle fabric is steeped for several hours in a cold soluion of kiton blue v at
ph 3.1; blue indicates lignified celluloses, urea form aldehyde resins ,and 
polyamides; no colour indicates cellulose fibres and phenol-formaldehyde types.

 (A) Scbiff;s reagent, see test 13. (b) A small piece of cloth 
is placed in 2 c.c. of 66% v/v H2SO 4,and a few crystals of cbromotropic acid heat 
at 60-70 deg, c. for ten minutes: bright violet indicates formaldeghde. 
A blank is necessary to allow for impurities in the air. (C) scbryver's 
test; to 5 c.c of solution prepared by hydrolysing resin coated fabric with 
2% HCI at the boilfor ten minutes, add I c.c. fp freshly prepared I% 
phenylhydrazine hydrochloride stand two to three minutes, add I C.c.5% 
potassium ferricyanide and 5 c.c. conc. HCI : purple red indicates formaldehyde.  
(D)To 5 c.c. of hydrolysate (as test (C) add a little pbloroglucinol and neutralise 
with NaOH : deep red indicates formaldehyde.

IO% NITRIC ACID:

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.

WATER SWELLING;

Cameron and Morton's test; steep 0.5 gm. regenerated cellulose rayon in cold water,
centrifuge for five minutes at 1000 g. and weigh immediately. untreated fibres adn
borax treated fibres show 100% absorption; one per 40 glucse residues gives 35%
imbibition.

63% SULPHURIC ACID SWELLING :



Cameron and ,orton's test consists in steeping cellulose rayon
fibres for five seconds in the reagent; air five seconds, and wash with
an excess of water. uncross bonded viscose is completely parch mintised. Cross
bonded rayon varies from little change to high swenlling.

CUPRAMMONIUM SWELLING :


Cameron and morton's test; a few threads of cellulose rayon are shaken in Io
c.c. of (15 gms. copper.200 gms. NH3 per litre) for five
hours at room temperature. untreated viscose is completely soluble.
Highly cross bonded celluloses (e.g. one bond per 40 glucose residues)
are largely unchanged in appearance. intermediate cross bonding
(one bond per IOO glucose residues) gives rise to a highly swollen
condition.

WATER SOULBILLITY:

Soluble cold, insoluble hot; cold water solutions gel on heating :
lower methy celluloses. soluble in hot water and dilute alkalis;
higher methyl cellulose. soluble in cold and hot water : sodium
carbocymethyl cellulose. insoluble in water : ethyl cellulose.

LANTHANUM NITRATE TEST;

To a piece o ffabric in a test tube add a few drops conc. hCI, add I C.C.water, warm ten
minutes, decant off, add a few drops of 5 % lanthanum nitrate, add one drop of
( I gm. iodine, 20 gms. KI, in 500 c.c water), add a few drop of 0.880 ammonia; brown
or blue indicates vinyl acetate or cellulose acetate.



(a)To 0'I gm, resin add 7c.c. chloroform, I C.C. glacial acetic acid, 
I C.C. I O% gromine in chloroform, shake, stand in a closed vessel: 
permanent red indicates coumarone or indene. (b) bromine in carbon 
tetrachloride, below O deg. C. gives the dibromide of indene, m.p.
31.5-32.5 deg. C. which is converted by boiling water into hydroxy-
fromide, m.p. 130'5 deg.C.:



Place a little fabric in I.C.C. of (0'0I% azobenzene phenylhydrazine 
sulphonic acid in IOO c.c. water) add 04 c.c. H2 SO4,heat in a 
steam bath for two to three minutes, cool , add a few drops of pure 
indicates a aldehyde.: