𝐀𝐧𝐚𝐥𝐲𝐬𝐢𝐬 𝐨𝐟 𝐀𝐥𝐜𝐨𝐡𝐨𝐥

Introduction

• Alcohol is a depressant, sedative, and hypnotic drug, with ethanol being the most important alcohol of pharmacological interest. 
• It is a colourless, transparent liquid that is miscible in water and has a burning taste with a fruity odour. 
• Pure alcohol is a volatile, colourless, and flammable liquid at room temperature.

Fate of Alcohol in Body 

• Alcohol, being a CNS depressant at low blood levels, decreases the activity of neurons with behavioural stimulation and produces simultaneous changes in neurotransmitters in the brain. 
• If it is ingested in small doses, it affects cortical function, and if ingested in larger doses, it depresses the medullary processes.

Test for Ethyl Alcohol

• Iodoform Test

1. Take 1 ml of distillate (alcohol) in a test-tube and add 1 ml of 5% NaOH solution and then add iodine solution drop by drop until persistent dark brown colour appears. 
2. Then keep it for 3-5 minutes and add few drops of NaOH to it, hexagonal crystals of iodoform are formed which are yellow in colour, indicating the presence of ethanol.

• Dichromate Test

1. Take 1ml of sample in a test-tube and add 0.2 ml of 2% potassium dichromate which is followed by about 1-2 ml of concentrated sulphuric acid.
2. Colour of the dichromate changes from yellow to green indicates the presence of ethanol.

Test for Methanol

• Chromotropic Acid Test

1. Take 1 ml of sample in a test-tube and add 2 ml of potassium permanganate solution, then mix it well.
2. Then sodium bi sulphate crystals are added to it with continuous shaking till the colour of the solution disappear. 
3. Then add 1 ml of chromotropic acid and add concentrated sulphuric acid. Presence of methanol is indicated by the appearance of violet colour.

• Schiff's Test

1. Take 0.5 ml of sample and add 0.2 ml of 5% potassium permanganate solution and 0.2 ml of phosphoric acid and keep it aside for 10 minutes.
2. Then 1 ml of 10% oxalic acid is added followed by 1 ml of concentrated sulphuric acid. 
3. Cool the solution and add 5 ml of Schiff's reagent, keep it for 15-20 min. Appearance of purple colour indicates the presence of methanol.

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