The methyl orange or methyl orange It is an azo derivative compound, used as a colorant and pH indicator. Its scientific name is sodium salt of (p - [[p- (dimethylamino) phenyl] azo] benzenesulfonic acid and its chemical formula C14H14N3NaO3S.
It is also known by other names such as: heliantine, Poivrier orange, III orange and gold orange. The color of methyl orange is orange-red. Its cornering zone ranges from 3.1 to 4.4. Below 3.1 it is red and above 4.4 it is yellow-orange.
This azo-derived dye has various applications. These include: analysis of chemical and pharmaceutical substances, especially in the titration of acids and also as a colorant in textile products and biological fabrics.
This substance is a skin and mucous irritant. Therefore, safety implements should be used to handle this compound, such as a gown, gloves, closed shoes, and safety glasses. It also has mutagenic activity.
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The methyl orange pH indicator has a solid physical state and can be dissolved in water to form an aqueous solution. It is orange-yellowish in color and has no odor (odorless).
It has a boiling point at> 300 ° C, the density is equal to 1.28 g / cm3. It is soluble in 500 parts of water and is insoluble in alcohol. Its molecular mass is 327.34 g / mol.
The reaction comprises diazotization and dimethyl aniline coupling. For its synthesis we proceed as follows. The first thing is to prepare the following solutions separately:
When the solutions are cold, proceed as follows:
- Arrange an ice bath (between 0 and 5 ° C). On it, (1) add the solution (2) drop by drop, shaking frequently.
- In that temperature range (inside the ice bath), slowly add the solution (3), then add the solution (4).
- Remove from the ice bath and mix until it reaches room temperature. Little by little, the mixture will acquire a dark red color.
Then add 10% sodium hydroxide solution (NaOH) until reaching a slightly alkaline pH (approximately 40 ml). If the solution is very dark, a little more 10% NaOH can be added until it takes on the characteristic color..
30 g of NaCL (common salt) is added and subjected to a heat source at 50 or 60 ° C. Let cool and filter by suction method. Expose for 10 minutes to a stream of air. Subsequently, the drying is finished using an oven or a desiccator, and finally it is weighed to determine the performance.
An aqueous solution of methyl orange can be prepared from the powder..
Many chemicals require titration. The pH indicators help in this procedure. In this case, it is very useful especially with acidic substances.
Methyl orange, in addition to serving as a pH indicator, has the property of dyeing substrates such as cotton. That is why it is widely used in the textile industry.
There are histological tissue staining techniques where a variety of stains are used, where Fuschin acid, methylene blue and gold orange or methyl orange participate..
With this technique, connective tissue and collagen are stained dark blue, muscle tissue is colored bright orange, while chromatin is stained yellowish-brown, and erythrocytes are stained orange-red..
The methyl orange pH indicator is toxic, therefore direct contact with skin and mucous membranes should be avoided. It is also toxic by inhalation or ingestion. In all the cases mentioned it has an irritating effect, being able to redden the affected area.
The NFPA (National Fire Protection Association) classifies substances according to 3 categories identified by color: health hazards (blue), flammability (red) and radioactivity (yellow). Each one is weighted with a numbering that goes from 0 to 4.
According to the NFPA this substance was classified with a health risk 2, which means moderate risk. Regarding flammability, it is classified as 1, which means slight risk; and in terms of reactivity it is classified as 0, that is, there is no risk of this nature.
The methyl orange pH indicator can be toxic to the environment, therefore, its waste must be disposed of in accordance with the provisions of the laws of each country..
Its waste is found in effluents from the textile industries, which use this dye to dye fabrics, paper, and leather, among other products..
The maximum limit allowed is 200 mg / L in total suspended solids of colorants.
The absorption technique today is seen as one of the best options to remove organic compounds from water..
For this reason, research is being done to remove the methyl orange dye among other organic compounds with low-cost absorbent materials, such as: orange peel, cotton, rice, activated carbon, bentonite, powdered leaves, coconut shell, charcoal. sawdust, ZnO nanoparticles and lamellar double hydroxides.
In the event of some type of accident with this substance, proceed as follows:
- If the methyl orange pH indicator splashes on the ocular mucosa, it should be rinsed with plenty of cold water for 15 minutes..
- In case of direct skin contact, rinse with plenty of water and then treat the irritation with an anti-inflammatory cream..
- If it splashes on clothing or shoes, these should be removed and washed before reuse.
- In case of inhalation, move the patient to a place with plenty of fresh air. If he has difficulty breathing, assist him with artificial respiration, and if possible oxygen should be administered.
- Finally, if the substance was ingested, you should not induce vomiting, and you need to drink plenty of water. In all cases, medical assistance should be sought immediately..
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