c Hydrogen chloride Put rock salt sodium chloride into a 100 mL filtering flask Coarse rock salt causes less frothing than the fine salt Carefully add concentrated sulphuric acid down the thistle funnel You can collect hydrogen chloride gas by upward displacement of air as in the diagram i Collect four test tubes of the gas and cork them Remove the cork from one of these test tubes under water Note the solubility of hydrogen chloride ii Hold a piece of cotton wool soaked in ammonium hydroxide at the mouth of a testtube of hydrogen chloride iii Shake a testtube of the gas with water to obtain a solution of hydrogen chloride Test the solution with an acidbase indicator Put a piece of magnesium ribbon in the solution Collect any gas formed and test for hydrogen with the glowing splint test