A definite volume of the gas being analysed is passed from initial measurement vessel 1 through absorbing vessel 2, filled with a compound that absorbs the gas being analysed. The unabsorbed remainder of the gas passes into bell-shaped vessel 3, displacing it. Flexible cord 5, running over round pulley 6 which turns about fixed axis A, is linked to vessel 3 at B and to counterbalancing weight 7 at C. On scale 4, hand a, rigidly secured to flexible cord 5, indicates the reduction in volume corresponding to the absorbed volume of gas.
$3719$SHP,M$