Sunday, January 2, 2011


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.


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   A small portion of cloth treated with synthetic resin is held to a Bunsen flame, and withdrawn after ignition.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.