[Halo]

Say, I preheat 50ml of 98% H₂SO₄ (sulphuric acid) and proceed with adding 25ml of 85% HCOOH (formic acid).
The result of which is:

H₂SO₄ + HCOOH -> CO + H₂O

Sulphuric acid will dehydrate formic acid producing CO, however gas could still be contaminated with vapor. What is the correct way of removing these impurities?

[Borek]

First of all, you should add acid to the solution, not the other way around.

Drying a gas is a standard lab procedure, have you tried googling it?