# Purify gas produced after reactions with sulfuric acid

Say, I preheat 50ml of 98% $\ce{H2SO4}$ and proceed with adding 25ml of 85% $\ce{HCOOH}$. The result of which is:

$$\ce{H2SO4 + HCOOH -> CO + H2O}$$

Sulfuric acid will dehydrate formic acid producing $\ce{CO}$, however, gas could still be contaminated with vapor. What is the correct way of removing these impurities?

## 1 Answer

Pass the gas mixture through Anhydrous Calcium Chloride or Silica Gel. Calcium Chloride is quite hygroscopic and absorbs water vapors from the gas mixture. Alternatively you can use Silica gel, which adsorbs water due to its nature as a good adsorbent.

Edit: To get rid of the acids present in the vapor, bubble the mixture through a concentrated base solution. Acids would react with the base, while $\ce{CO}$ being a neutral oxide, simply doesn't react and can be collected.

• It'll absorb water vapor, but there should be some vapor from the acids still present, I guess.
– Halo
Apr 27 '17 at 12:24
• @Halo I have made the edit :) Apr 27 '17 at 12:32