Making 99.5% Absolute Alcohol - Lu Le Laboratory

Absolute or anhydrous alcohol refers to ethanol with a low water content. There are various grades with maximum water contents ranging from 1% to ppm levels. Absolute alcohol is not intended for human consumption. If azeotropic distillation is used to remove water, it will contain trace amounts of the material separation agent (e.g. benzene). Absolute ethanol is used as a solvent for laboratory and industrial applications, where water will react with other chemicals, and as fuel alcohol. Spectroscopic ethanol is an absolute ethanol with a low absorbance in ultraviolet and visible light, fit for use as a solvent in ultraviolet-visible spectroscopy. (Wikipedia)

In the experiment, we are going to use calcium oxide(quicklime) to remove the water from 95% ethanol by distillation.

Calcium oxide forms calcium hydroxide when it attach water, and calcium hydroxide would lose water only when the temperature is higher than 580℃ so that we can obtain 99.5% absolute alcohol.

CaO_(s) + H₂O_(l) → Ca(OH)_{2 (s)}

Chemical

1.      95% ethanol: 150mL

2.      Calcium oxide(quicklime): 10~15g

 Calcium oxide is so called quicklime

Smash the block into small pieces

Procedure

1.      Set up the distillation apparatus

2.      Place 10~15g calcium oxide and a stir bar in the flask

 

3.      Pour 150mL 95% ethanol into the flask, start to stir and distill the mixture.

 

4.      Collect about 100~120mL distillate. 

5.      The final product should be very clean and colorless. Store it in a flask and seal the stopper with some grease because the 99.5% absolute alcohol is easily deliquescence.

 Absolute alcohol is very clean 

A huge amount of calcium hydroxide and calcium oxide precipitate

It is a jelly mixture