Methylene Blue

What is Methylene Blue?

Methylene blue is a colourful organic chloride salt compound used in medicine and by the biologists as a dye to help them see under the microscope. It is also known as Methylthioninium chloride or Swiss blue. It is represented by the formula C16H18ClN3S. It was discovered in the year 1876 by German chemist Heinrich Caro.  Historically, it has been widely used in Africa for treating malaria, but now it has been disapproved when chloroquine and other drugs entered the market. Its molecular weight is 319.85 g/mol. It can cause damage to RBCs and also decreases the ability of the blood to carry oxygen which is the primary health concern of humans when exposed to the methylene blue via oral or intravenous means. Methylene blue is a thiazine dye which is basic in nature. Methylene blue stains negatively charged cell components like nucleic acids. 

Structure of Methylene Blue

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Structure of Methylene Blue(C16H18ClN3S)

Formula of Methylene Blue

Methylene blue is represented by the formula C16H18CIN3S. It has  3,7-bis(dimethylamino) phenothiazin - 5 - ium as the counterion. Its IUPAC name is [7 - (dimethylamino) phenothiazin - 3 - ylidene] - dimethylazanium; chloride. 

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Preparation of Methylene Blue

  1. Methylene blue is prepared by the oxidation of dimethyl-4-phenylenediamine in the presence of sodium thiosulfate. 

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  1. By treating the solution of N, N-dimethyl-p-phenylenediamine and N, N, -dimethylaniline hydrochlorides with H2S and FeCl3 or another suitable oxidizing agent.

  2. By oxidation of p- amino dimethylaniline with ferric chloride in the presence of hydrogen sulfide. The dye is zinc chloride double salt of the chloride.

  3. N, N-Dimethyl - p - phenylenediamine reacts with sodium thiosulfate to produce thiosulfonic acid which then condenses with N, N-dimethylaniline when it comes in the presence of Na2Cr2O7 or sodium dichromate to form the indamine, then with copper sulfate and sodium dichromate to the methylene blue.

Related Compounds to Methylene Blue

  • Methylene Blue cation

  • Azure A

  • Azure B

  • Methylene green

  • 3-(Dimethylamino)-7-(methylamino)phenothiazin-5-ium

  • 3,7-Bis(dimethylamino)-4-nitrophenothiazin-5-ium

Properties of Methylene Blue

  • Methylene blue is deep blue in colour. 

  • Methylene blue exhibits antioxidant properties.

  • It also exhibits the property of antidepressants.

  • It is highly soluble in water, chloroform, ethanol, and glacial acetic acid.

  • It is insoluble in ethyl ether, xylene, and oleic acid.

  • It also has the property of antimalarial.

  • It gets decomposed while heating and emits toxic fumes of nitrogen oxides, sulfur oxides, and chlorides. 

  • It is non-carcinogenic in nature.

  • It is slightly soluble in pyridine. 

  • It is basic in nature. It's a basic thiazine dye. 

  • It also exhibits cardioprotective properties. 

  • It is non-combustible in nature.

  • It acts as the enzyme inhibitor. 

Uses of Methylene Blue

  • Methylene blue is used in aqua-farming for treating fungal infections.

  • It is used as an antiseptic in cases of urinary tract infections. 

  • It is also used as an indicator during the different chemical reactions.

  • It is also used for the treatment of Methemoglobinemia.

  • It is also used to dye paper and office supplies, but also to tone up silk colours.

  • It is also used in the treatment of septic shock and anaphylaxis.

  • It is also used as a dye for the number of staining procedures.

  • It is also used as a temporary hair colourant.

  • It is used as an oxidation-reduction agent in different chemical reactions.

  • It is used in the treatment of pediatric and adult patients with methemoglobinemia.

  • It is used as a reagent in oxidation-reduction titrations in volumetric analysis. 

  • It is used in the treatment of hypoxia.

  • It is used for dyeing cotton and wools. 

  • Earlier methylene blue was used to check whether the pasteurized milk is bacteria-free or not. If the colour remains blue, that means milk is pasteurized properly or else if blue colour disappears that means bacteria is consuming oxygen and the milk is not pasteurized properly.

Fun Facts

  • It is slightly irritant to the eyes.

  • It can cause redness in the eyes tissues if it gets in contact with the eyes.

  • If you are having a deficiency of glucose-6-phosphate dehydrogenase, then you should not be treated with methylene blue.

  • Symptoms of overdose of Methylene blue are Abdominal or stomach pain, bigger, dilated, or enlarged pupils, dark urine, difficulty breathing, fever, headache, increased sensitivity of the eyes to light, nausea, pale skin, blue staining of the urine, skin, and mucous membranes, rapid heart rate, rapid shallow breathing, etc. 

FAQ (Frequently Asked Questions)

1. What are the Effects of Methylene Blue on Health?

Ans. There are several effects of methylene on health, it causes vomiting, headache, shortness of breath, and high blood pressure. If used during pregnancy, It may also cause harm to the baby. It also converts ferric ions to ferrous ions present in the haemoglobin. It is also allergic to some people. It also causes chest pain. Common side effects also include abnormal urine or stool colour. There are some less possible side effects also such as mild bladder dizziness, headache, irritation, upset stomach, increased sweating, vomiting, abdominal pain, nausea, diarrhea, frequent urination, and stomach cramps. Side effects of large doses of Methylene Blue also include chest pain and  confusion as well. 

2. Is Methylene Blue Used as the Redox Indicator?

Ans. Methylene is used as the redox indicator in analytical chemistry. For example, it is used in the blue bottle experiment which is a colour-changing redox reaction. Redox indicator undergoes a definite colour change at a particular potential. A requirement for a fast and reversible colour change indicates that the oxidation-reduction equilibrium for an indicator redox reaction needs to be established very quickly.