Helo, reders welcome to “textilesgreen” today i m going to explain about all basic information of azo dyes and azo dye test. i m writing all information in this article with my personal view. so, read complete article.
All basic information of azo dyes
azo dye are soluble in water therefor azo dye is easily dissolve in water and azo dye are also called chemical class of dyes. and this dye are highly organic compound. and this dye are windly used for cellulosic materials. and this dye gives good effect on cellulosic materials such as cotton. and azo dye have also ability to dyed proteins fibres such as wool and silk.
This dye have some important colouring Fuction this is the reason it gives good colour or shade on materials. some azo dyes is harmful for skin but not all azo dyes. because azo dye is highly soluble in water it is easy to dissolve in water. this is the reason it easy for the body to absorb during dyeing or during processing. when dyes are contect on skin then it may increase chances of skin cancer. This dyes are easily accumulated and easy to absorb in the body. and also increase the chances of exposure when wering garments. so, some company are banned of azo dyes.
• why azo dyes are banned?
azo dye having “aminogroup” but some amines are careinogenic in nature. and some amines persent in azo dye but this amines are highly effected for skin. and azo dyes could be banned from skin contact because When dyes are contect on skin then this amines are easy to absorb or accumulated in the body and easy to absorb by the skin then thet cause skin cancer. this is the reason some azo dyes are banned. this dyes are very harmful for skin if you are not use properly.
Azo dye structure
Azo dye is a one type of organic compound. it contains function group such as (N=N). this is also known as azo compound and this is also used as a azo dyes. It is windly used to treatment of textile and some foods. it is also be used as a azo pigment. but it Is insoluble in water.
Azo dye list
• Acid Red 13
• Acid orange 7
• Brown FK
• Congo red
• Direct Blue 15
• methyl yellow
• methyl red
• orange G
• orange B
• Sudan yellow 3G
• solvent red 26
• Black 3
• pigment yellow
preparation of azo dyes
preparation of azo dye is done with the help of diazotization process. here I m going to explain about preparation of an azo dyes with the help of flow chart. First of all aromatic amine (aniline) are transferred to diazonium component and the azo coupling reaction is carried out (reaction with coupling components process with phenol and napthol) then make azo dye. this is the complete reaction for preparation of an azo dye.
Aromatic amine (aniline)
Cuppling reaction with cuppling component process with phenol or nepthole
This are the complete preparation of an azo dye.
Azo dye test
Azo dye test is carried out in textile laboratory with the help of lab instruments.
Materials required for azo dye test
• test tube
• p glass
• glass rod
• gas burner
• bekar with ice
In Azo dye test process take some important chemicals such as
• Aromatic amine (aniline)
• Beta Nepthole
Here, first of all
Aromatic amine (aniline – C6H5NH2)
Heat (10- 15 sec)
Again add NaNO2
Keep the test tube in ice cold bekar
Diazonium salt formed
Then again take second test tube
and again take,
beta napthol in second test tube
Heat (for few seconds)
Keep the second test tube in ice bekar
Beta- Nepthol solution
Then add both solutions
diazonium salt + Beta – Nepthol solution
Azo dyes. (Red colour)
Azo dyes test reaction with phenol, aniline,beta nephthol.
• Azo dye test Reaction with phenol and aniline
1. In this reaction first phenol is directly react with benzene diazonium chloride and then make azo component, and it gives yellow product, this is called yellow azo dyes.
2. In second reaction, aniline solution is react with same benzene diazonium chloride then it gives yellow product and this produt is called yellow azo color or yellow azo dyes.
Azo dye test reaction with beta nephthol
3. In this azo dye test reaction first beta nephthol (napthelene+alcohol = beta nephthol) is react with benzene diazonium chloride then make azo dyes component this is called red colour azo dyes.
• Azo dye reaction|preparation of azo dyes
Azo dye reaction with phenol
In this reaction, first phenol is react with NaOH then it gives sodium phenoxide. and then keep in ice bath and then add cooling benzene diazonium chloride solution then it react between sodium phenoxide and benzene diazonium chloride. and then make yellow – orange azo dye.
• Azo dye reaction with aniline
In this reaction, first of all some liquid of phenylalanine (aniline) is add in cooling solutions of benzene diazonium chloride. and mixed properly of both solutions. A yellow solid will produce. and yellow colour is formed. this strong color is azo compound. this is used as a azo dyes or this is called azo dye.
• Azo dye reaction with beta nephthol
In this reaction, First of all
beta naphthalene is dissolved in NaOH (sodium hydroxide) and this solution will keep in ice bath for few time and then mixed properly with benzene diazonium chloride solution and it gives results as a orange-red color produced. this product is also called red azo dye.