Identification of Dyestuffs

(A)                       Preliminary Tests

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Appearance of dye Powder	Amorphous	Direct, Acid, Basic, Sulphur, Mordant, Vat, Naphthols, Fast bases, Salts, Rapid fast, Indigosol etc.
		Crystalline	Some Basic dyes, Disperse dye
		Flakes like	Aniline salts
2.	Colour of Powder	Bright, Shining	Basic
		Bright	Direct, Acid, Basic, Vat, Mordant etc.
		Dull	Sulphur
		Light colour	Indigosols, Naphthols, Fast salts, Some Fast bases, Rapid fast, Rapidogen etc.
3.	Weight of Powder	Light	Basic, Direct, Vat, Acid etc.
		Heavy	Pigments
4.	Smell of Powder	Phenolic	Naphthols
		Aromatic	Fast bases, Salts
		Sweet Smell like chloroform	Indigosols

(B)                        Solubility Tests

Sr. No.	TESTS	OBSERVATION		INFERENCE
1.	Dye Powder + Water (Heat the Solution) Original Solution	A	Dissolves in warm but precipitated at boiling	Fast salts
		B	Dissolves very freely giving a faint coloured solution	Indigosols, Aniline salt
		C	Dissolves very freely giving a deep coloured solution (Transperent)	Direct, Basic, Reactive, Acid, Acid mordant etc.
		D	Insoluble particles in suspension condition	Naphthol, Vat, Sulphur, Fast bases, Pigments
		E	Insoluble particles in disperse condition	Disperse

Preliminary Tests For A

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution  + Naphthol Solution	Deep Coloured Solution	Fast salts

Preliminary Tests For B

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution  + NaNO2 + dil. HCl or H2SO4 & Heat	Deep Coloured Precipitates	Indigosol
		No ppts.	Pre –Aniline Salt

Preliminary Tests For C

Sr. No.	TESTS	OBSERVATION		INFERENCE
1.	Original Solution  + Tannin Reagent & Heat	Precipitates are obtained in few minutes		Basic Dye
		No ppts.		Direct, Acid, Acid mordant
2.	Original Solution + Wool + Tanned Cotton + Acetic Acid (2 – 3 drops) & Heat	I	Both Cotton & Wool dyed in full shade. Not fast to rubbing	Basic Dye
		II	Cotton dyed deeper then wool & fast to rubbing	Direct Dye, Reactive dye
		III	Wool is dyed & Cotton stained, it is stripped in hot dil. NH3	Acid, Acid mordant

Preliminary Tests For D

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original powder + dil. HCl + NaNO2. Drop by drop	A clear solution is obtained after few minutes which give coloured ppts. With naphthol solution	Base
		No ppts.	Naphthol, Vat, Sulphur etc.
2.	Powder + NaOH solution + Water & Heat	Dissolve freely giving clear solution	Naphthol, Rapidogen
		Insoluble	Sulphur, Vat
3.	Original Solution + dil. Acetic acid or Formic acid & Heat	Coloures ppts.	Rapidogen
		ppts. as Original substance	Naphthol
4.	Powder + Na2S & Heat	Dissolve freely with a change in colour	Sulphur
		Do not dissolves	Vat
5.	Powder + NaOH + Na2S2O4 & Heat	Dissolve with a change in colour	Vat

(C)                       Confirmative Tests

Confirmative Tests for Fast Salt

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution + Naphtholated yarn	Deep colour Yarn dyed in full shade	Fast Salt
2.	Fastness test	Not fast to rubbing	Fast salt

Confirmative Tests for Indigosols

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution + NaNO2 + Cotton, Warm squeeze & put in hot dil H2SO4 Solution	Cotton gets dyed, in full shade	Indigosol
2.	Dyed yarn + NaOH + Hydro, & Heat	Colour is reduced & restored in air or persulphite	Indigosol
3.	Fastness test	Fast to all	Indigosol

Confirmative Tests for Aniline Salt

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution + dil H2SO4 + Cotton + K2Cr2O7 (drop) & Heat	Cotton is dyed, from brown to black colour	Aniline salt
2.	Bleaching test	Turns brown or diminished	Aniline salt
3.	Fastness test to rubbing	Not fast to rubbing	Aniline salt

Confirmative Tests for Basic Dye

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Dyed wool + white Cotton + white Wool + Soap solution & heat	White Wool is dyed deeper than white Cotton	Basic dye
2.	Dyed wool + 10 % Sodium hydrosulphite solution	Dye is not stripped and no effect on original shade	Basic dye

                   

Confirmative Tests for Direct Dye

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original solution + Cotton + 2 – 3 drops Soda ash + NaCl Boil	Cotton is dyed in deep shade	Direct dye
2.	Dyed cotton + NaOCl solution	Colour is discharge within 5 – 7 minutes	Direct dye
3.	Dyed cotton + white Cotton + Soap solution, Boil	White cotton stained	Direct dye

Confirmative Tests for Reactive Dye

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution + Cotton & after dyeing add Cotton & H2SO4	Dye stained untreated cotton and partially stripped from dyed cotton	Reactive dye
2.	Above dyed cotton + Pyridine or Chloroform , Warm	No effect	Reactive dye

Confirmative Tests for Acid Dye

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution + Wool + CH3COOH + Cotton & Heat	Wool dyed deeper than Cotton or Cotton is not dyed	Acid dye
2.	Dyed wool + Strong hydrosulphite solution	Dye stripped from the dyed fibre	Acid dye
3.	Dyed wool + K2Cr2O7 + water & Heat for 5 minutes (Treated wool) + Soap solution, Boil & untreated dyed wool + soap solution & boil separately	Colour is stripped from both dyed samples	Acid dye

Confirmative Tests for Acid Mordant

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution + Wool + Cotton & Heat	Wool dyed deeper than Cotton or Cotton is not dyed	Acid mordant
2.	Dyed wool + drop of  K2Cr2O7 ­+ Water & Heat	Colour become deeper or changed on tone	Acid mordant
3.	Dyed wool (untreated with K2Cr2O7) + Soap solution & Heat	Colour stripped	Acid mordant

Confirmative Tests for Fast Base

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original Solution* + Naphtholated yarn	Yarn is dyed in deep full colour	Fast Base
2.	Fastness to rubbing	Not fast to rubbing	Fast Base
3.	Dyed cotton + NaOCl solution	No change in colour of the dyed cotton	Fast Base
4.	Dyed cotton + Rongolite – C + CH3COOH , Boil	Original colour of the dyed cotton is changed	Fast Base

·         Original solution made by HCl + NaNO₂ +Sodium acetate

Confirmative Tests for Rapidogen

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original solution + Yarn + Hot  Acetic acid	Yarns get dyed	Rapidogen

Confirmative Tests for Naphthol

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Original solution + Fast salt	Deep coloured ppts.	Naphthol
2.	Original Solution + Yarn & put it in fast salt solution	Yarn gets dyed in full shade	Naphthol

Confirmative Tests for Sulphur Dye

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Powder + SnCl2 + Conc. HCl & Heat	Lead acetate paper turns brown to black with silvery effect	Sulphur dye
2.	Fastness to bleaching	Loose to bleach	Sulphur dye
3.	Powder + Na2S + cotton & Heat	Cotton dyed with full deep colour	Sulphur dye

Confirmative Tests for Vat Dye

Sr. No.	TESTS	OBSERVATION	INFERENCE
1.	Dyed cotton + Soap solution  Boil for 2 minutes	Colour is not remove	Vat dye
2.	Dyed cotton + NaOCl	Fast to bleach	Vat dye
3.	Dyed fibre + Formic acid (85 %), Boil	Colour is not remove	Vat dye
4.	Dyed fibre + Na2S2O4 solution	No change in colour	Vat dye