Acetic Acid

Acetic Acid MSDS

Acetic acid is a clear colorless liquid with a very strong vinegar type smell (only waft it, don't stick your nose above the bottle since the fumes are harmful). Anhydrous acetic acid is refered to as glacial acetic acid because of the crystals that form when its frozen (it freezes at 16C). Acetic acid is seen used for making esters with the acetate ion (such as ethyl acetate or amyl acetate which I am working on as I'm typing this). It is made by reacting sodium acetate with sulfuric acid and distilling.

This is the reaction that proceeds:

2CH3COONa + H2SO4 ----> 2CH3COOH + Na2SO4 (We will be using high temps so the sulfate forms instead of the bisulfate)

Materials Equipment
Sodium Acetate Distilation Apparatus w/ 500ml boiling flask
Sulfuric Acid Oil bath
Calcium Chloride or Magnesium Sulfate (Anhydrous)  

Synthesis:

Into the boiling flask of the distillation apparatus, pour in 160grams of anhydrous sodium acetate. Measure out 75mls of concentrated sulfuric acid and add it quickly the to flask with the sodium acetate. Quickly seal up the distillation apparatus. Once the sulfuric acid is mixed with the sodium acetate, a vigorous reaction will occur and poisonous white fumes will be produced at a great volume. It is important that the distilation apparatus is sealed up before this happens so that the fumes don't fill up your lab. On a side not, acetic acid of any concentration will not eat up rubber stoppers, even as a vapor.

Begin heating the flask with an oil bath and bring the oil bath's temperature up to 150C. Hold it there until you've collected at least 95mls of acetic acid (you should be able to get about 100-105mls). When you get all the acetic acid that you think you'll get without permanently fastening the by-products into the distillation flask, stop the distillation.

To make this anhydrous (glacial), pour the acetic acid into a clean 500ml boiling flask (with ground glass joints) and add ~50grams of anhydrous magnesium sulfate or anhydrous calcium chloride. Reflux this for an hour or so. It would also be wise to put a calcium chloride drying tube at the end of the reflux column, just to make sure no moisture enters the flask). After this, take the reflux column off and set the flask up for distilation. Collect the fraction between 116C and 120C.

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