DEXTRIN

DEXTRIN:
      
               The term dextrin denotes a starch partly or completely broken down to water soluble bodies. White dextrin is a product in which the solubilising process is incomplete, leaving a high percentage of unconverted starch :It can be made from any type of starch .british gum is a light yellow product obtained by roasting starch at 150 deg. C.for some hours, after moistening with 0.2-0.4% nitric acid; this results in very considerable conversion of starch. It is almost always made from maize starch only. Dextrin proper is a dark co-loured,completely soluble,and completely converted form of British gum; it can be made from any type of starch.

The commercial products consists of a mixture, in varying proportions, of starch ,soluble starch, dextrin, and dextrose. They are insoluble in 50% and in 100% alcohol. The moisture of a good quality is not more than 8% and ash less than 0.5%. Only the starch free dextrins give a clear solution in water.

For most purposes in textile printing a good dark dextrin may be used at 8 IB .per gallon to replace gum senegal at 12 IB .per gallon, but the shades are somewhat yellower, as steaming "fixes" some of the yellow colouring matter , especially in wool and silks .for thickening strongly alkaline colours a maize starch gum should be used .

The analysis consists of extracting dextrose and dextrin by cold water, the residue beidue being dried and weighed as unconverted starch. the extract is boiled with fehiling's solution (i) as it stands ,and (ii) after hydrolysis with acid ; the former value gives dextrose, and the difference between the two values is calculated as dextrin.   

ANALYTICAL TESTS:

Burning test :
              
                 A small portion of cloth treated with synthetic resin is held to a Bunsen flame , and withdrawn after ignition. This test is of most value with coated fabrics on which there is a substantial amount of coating.
When only small percentages of resin are present, indications are often rather vague. Cellulose nitrate is very inflammable . Rubber has a characteristic  dour. Oxidized oil burns with a fatty smell.
The various odours indicated in test 3 may be recognized under favorable circumstances.

Sodium Fusion 
                
                    This should be the basis of the qualitative analysis of an unknown resin.It is carried out as in qualitative organic analysis by heating about 0.5 gm. cloth with a small pea-size piece of metallic sodium in a hard glass tube. Springy cloth may be cut into small shreds, made into a ball with very stiff methyl cellulose mucilage, and dried before carrying out the test. Alternatively, the cloth may be charred at low heat, and after cooling the tube to room temperature, the sodium may be added. After fusion, the red-hot tube is dropped into an evaporate- ing dish containing a few c.c. of distilled water ; this should be done at arm,s
length, with suitable precautions against possible flying sodium. The test is dangerous if cellulose nitrate is suspected; this is liable to explode. The following tests are carried out for the detection of elements.

   Cblorine. To a small portion of the extract add a little silver nitrate solution; a white precipitate of silver chloride ( which blackens on exposure to light ) indicates chlorine, which may be from chloroprene,
chlorinated rubber, chlorinated diphenyl, polyvinyl chloride, or poly-vinylidene chloride. A very beavy precipitate may indicate chlorine-ated rubber ,which contains up to 60% of chlotine.

Nitrogen. To a portion of the extract add a little ferrous sulphate ( containing a little iron oxide in suspension) and warm with nitric acid.A bluish-green colour or precipitate of Prussian Blue indicates nitrogen, which may be from aniline /formaldehyde, cellulose nitrate, melamine/formaldehyde, polyacrylonitrile, resins urea/formaldehyde, thiourea/formaldehyde.
  Add 2 c.c. of extract to 10 c.c.of ammonium moderated in nitric acid solution .A yellow precipitate of ammonium phospho-molybdate,soluble in alkalis, indicates phosphorus, which may be from casein ( or, more rarely, from certain unusual textile auxiliaries).This is the best distinguishing test between lanital and such other protein plastics; it distinguishes between lanital and such fibres as Ardil. 

YARN PROPERTIES

The strenght / strench properties of yarns are dealt with in the general chapter on that suhect .The principal test considered here are for yarn size, twisr, fold ,and regularity.
YARN "SIZE"
                      the size or .number of a yarn is stated in one of two ways:as the lenght per unit weight ,or as the weight per unit lenght. The former method is used for spun yarns and the latter for filament yanrs.
There are different units of lenght and weight for different fibres and in diffferent countries, and the position as it exists today is  chaotic and illogical . Various proposals have been made for international standardisation, but these have made little progress because any abrupt change would cause great dislocation of established customs and records.
For spun yarns the number of hanks of a standard lenght which together weight a standard amount gives the "counts ". For example,in worsted yarns the counts is the number of hanks of 560 yds. each,which weigh 1 IB.

For filament yarns the weight in grams of a standard hank of 9,000 meters gives the so-called "legal denier" but othe r hank lengths and other weight units are employed. In practice both counts and denier are determined in the same way i.e., by winding a definite number of yarns or metres into a hank, and calculating according to the appropriate system. The standard yarn reel (fig. 59) in general use cousists of six arms, of such a length that a single circuit of a hexagon is exctly 1,1/2 yds. for the counts system, or surface of the reel. A constant speed normally tension device should be incor porated.The winding speed normally varies between 100 and 300 revolutions per device should be just sufficient to take out crimp from the yarn without stretching it. A revolution counter must be fitted to record the number of turns of the it is fuseful to have a bell which gives warning when the required number of turns is being approached. The hankof yarn produced is weighed on any suitable and sufficiently sensitive balance; if many determinations of counts or denier are to be  carried out is canvenient to employ either the so-called "grain scales, or a quadrant-scaled balance , both of which can be arranged to give ditect reading of the counts. The quadrant scales are not usually accurate enough for analytical purposes, though excellent for works control. Weighings are usually carried out in the air dry state, preferably conditioned to standard regain. For precise purposes, or where no humidity control is available, weighing in the , oven-dry , state and calculating to canditioned weight at standard condition or regain should be adopted.

There are two general methods of procedure . in both cases the yarn is conditioned in the standard atmosphere of 65% R.H. at 68 deg. F.( conditioning from the dry side), before winding on to reel. method A. The reeled tarn is dried to constant weight, weighed, and the dry weight calculated to standard regain by adding the accepted percentage; the yarn count is as reeled is weighed, and the yarn count calculated from this " conditioned weight".
The two methods will usually give slightly different counts, dependent upon the degree to which the standard regain differs from the actual regain ( conditioned regain ) in equilibrium with the standard atmosphere. Method A is suitable for yarn of mixed fibres  ( e.g.,wool /cotton mixtures) and for fibres where the standard regain often differs appreciably from the conditioned regain (e.g. wool, viscose ). Method B is suitable for fibres whose standard regain does not differ greatly from the conditioned regain (e.g., cotton acetate,) for many commercial and technical purposes , and for cases where the yarn carries volatile oils or finishes.
    The textile institute tentative specification No.11 (1947) recommends reeling conditions such that the girth of the skein when removed from the reel is within 0.5% of the girth of the reel, when the skein is under a load of 440 yds . of the yarn under test. In this specification details are given of a skein gauge suitable for determining the skein girth.

In determining the grey counts of yarn from measurements on finished cloth, For example, in the case of cotton cloth, the average ptocessing losses may be taken as follows : designing -3% ; designing and bleach- ing- 5% ; designing bleaching , and dyeing to a light shade -7% ; designing and dyeing to dark shade ( no bleaching )-3%; aniline -black  dyed material gain of 2% ; mineral khaki gain of 5%. Writing G= estimated grey count F = count found in finished cloth, and L= loss factor in finishing ,then G= f(100-L /100).  

HALPHEN-HICKS TEST

Boli a little cloth with a solution of (1 part phenol, 2 parts carbon tetrachltide)
settle, pour bromine  vapour on to the surface: colora- tion (varuing according to
the ptoduct) indicates resin oils.
PHENOLS (a) Heat a little cloth with 1 gm. phthalic anhydride containing 2-3
drops of conc. sulphuric acid until a rich brown melt is obtained. Cool, dilute
with water , make alkaline with NaOH : pink indicates phenols.
(B) boil a little cloth or resin with 5 c.c. water containing 1 drop conc. H2SO4
cool, add a few drops of carbazole (1-2% in 95% ethyl alcohol ) and 1-2 drops of
conc. H2SO : blue indicates phenol/formaldehyde resin. (C) place a litle cloth on
a spotting plate, add one or two drops conc. HCI< then 1 drop of phenol- cresol
bodies.
The test may be used on resin solution . (D)see test 21 (indophenols).

DETERGENTS AND WETTING AGENTS :


This group of bodies include true sopas, sulphonated castor-oil sops, sulphonated and sulphated fatty alcohols, synthetic detergents, quaternary compounds, and saponins, with which may be incorporated solvents, alkalis, disinfectants, builders, or oxidising agents. The  prooery which they have in common is the power to wet dirt oils and fats and textile fibers ;
detergent power is a property which may be regarded as wetting agents for oils and waxes, though their simplle action is probably merely one of blending with the fatty body , reducing its melting point and viscosity, and waxes, thereby making emulsification mechanically easier. If the wetting solvent is polar in character it may most also act as a bridge between the fat and deter-gent molecules.
The most common solvents are carbon tetrachloride, trichlorethylene, pyridine, cyclohexanol, pine oil, and in stringly alkaline liquors, cresylic acid .(continue)

NITRATE TEST

A little diphenylamine is dessolved in 1 c.c. 90% sulphuric acid.
A drop of resgent is placed on the fabiric: deep blue indicates nitrate,
e.g. cellulose nitrate.

SCHIFF'S TEST:

Schiff's reagent is made by dessolving 0.2 gm. rosaniline (fuschsine)
in 10 c.c. of cold water previously saturated by sulphur diocide. On
standing, the pink colour disappears. The reagent is kept in a dark- coloured,
stoppered bottle. The addition of aldehyde restores the pink colour.

SULPHAMIDE TEST:

Ammonium sulphamide is sometimes used in conjunction with synthetic
resins for fireprooofing. To 5c.c. of a water extract, add an equal
volume of 5% mercuri chloride: a precipitate may indicate sulphamide.
Confirmation: heat 5 c.c. of the original solution with IO% KOH solution
when vapours alkaline to litmus are given off.

CASEIN :

Boil the fabric in water ,cool, to 5c.c. add 1-2 drops of conc. H2 SO4and
I1 drop of 3% formaldehyde; pour gently on to c.c. of conc. H2 SO4 containing
1 drop of 10% ferric chloride, without mix- ing: violet indicates casein, provided it
is present in a from sufficiently soluble for extraction.

Biuret test:

(A) A little cloth is boiled with conc. HCI to hydrolyse any protein present into 

amino-acids. A small portion of solution is made alkaline with dilute NaOH and a 

drop of delute copper sulphable proteins (e.G.,glue) give the reaction by extraction 

with water onle. (B) spot the fabric with copper sulphate solution, stand several minutes, 

then dip in dilute NaOH solution : deep vidicates protein.

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.

GIBB'S INDOPHENOL TEST:

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.

P-PHENYLENE DIAMINE TEST;

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.

KITON BLUE V TEST ;

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.

FORMALDEHYDE TEST:

 (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.

PHOSPHORIC ACID DISTILLATION:

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.

THIOCYANATE TEST:

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.

PICRATE TEST:

(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.

COUMARONE INDENE TESTS:

(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.:

ALDEHYDE IN ACETAL RESINS:

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.:

ANALYTICAL TESTS:

Xanthydrol test 

     The following test is given by the textile Institute ( Tentative Textile specification No.13). Hydrolyse the resin by warming at 50-60deg. C.
a small sample of the fiber in N / IO H2SO4 for a few minutes. Reduce the acidity in the usual way with sodium acetate and ass 1.5 c.c. glacial acetic acid. Add a few drops of IO %solution of xanthyrdol in methyl alcohol to I c.c of the aqueous hydrolysate. which may take some hours to form if only small amounts of urea or thiourea are present.

Vinyl Alcohol Test :
     Reflux the resin or treated cloth with methyl alcoholic KOH (N/2 concentration), filter, concentrate the solution to precipitate polyvinyl alcohol; filter, dissolve the precipitate in water, and acidify, when a blue co lour indicates polyvinyl alcohol.

Reducing Tests :
    (@) Fehilng's Solution: see pp. 42 and 44.
(b) Benedict's qualitative solution : see p.241.
Of these two methods, the Benedict soultion is much to be preferred for qualitative work, because it is stable as a single solution over long periods if kept in a stoppered bottle ,and is always resdy for use; moreover, some indication of the amount of sufar present may be obtained from the colour obtained, which ranges from green to red, with increasing amounts of glucose.

Basic Lead Acetate Test: 
    The reagent is made by pasting 30 gms. lead acetate, IO gms.litharge, with 5 c.c.water; stir stir on water -bath intl white, stir in IOO c.c.water , settle ,and filter. the test consists of adding a few drops of reagnt to a solution of the extract from cloth: a precipitate indicates gum,
moss, or albumen.
  

ANALYTICAL TESTS:

Burning test:

   A small portion of cloth treated with synthetic resin is held to a Bunsen flame, and withdrawn after ignition. This
test is of most value with coated fabrics on which there is a substantial amount of coating. When only small percentages of resin are present, indications are often rather vague. Cellulose nitrate is very inflammable. Rubber has a characteristic odour.  Oxidised oil burns with a fatty smell. The various odours indicated in test 3 may be recognised under favorable circumstances.

WOOL QUALITY :

WOOL QUALITY:


It is frequently desirable to determine the quality of wool used in the blend from which a yarn or fabric the been made. Results of sufficient accuracy may be obtained by fiber-diameter measurements.
The general division of wool qualities is into merino, crossbred,and cares grades.   Spanish merino is probably the best type of wool: crosses of this with native varieties have given various" crossbreds" and of these the best is botany wool. Of English wool, the coarsest ( longest staple ) are Lincoln,Leicester, Cots wold, Romney Wansley-dale ,and Devon; medium wools are south down, Shropshire, Hampshire, oxford, Suffolk downs, sorts, Rowns, sorest, and Ryland.There are various very coarse wools, used for carpers, on rained mainly from Iran, India, China and Mongolia, these contain unusually large amounts of hair and beard fibers.