Gay Lussac Law of Gaseous Volume

Gay-Lussac's law of gaseous volumes, put forward by Gay-Lussac in 1808, states that whenever gases combine with each other, or are produced, in a chemical reaction, they always do so in a simple ratio by volume — as long as every volume being compared is measured at the same temperature and pressure. Two illustrations from the text make this concrete. First, under identical conditions of temperature and pressure, 100 mL of hydrogen gas combines with 50 mL of oxygen gas to give 100 mL of water vapour — the volumes of hydrogen, oxygen and water vapour (100 mL, 50 mL, 100 mL) work out to the simple whole-number ratio 2:1:2. Second, again under identical conditions, 1 L of nitrogen gas combines with 3 L of hydrogen gas to produce 2 L of ammonia gas — here the volumes of nitrogen, hydrogen and ammonia (1 L, 3 L, 2 L) work out to the simple ratio 1:3:2. This regularity in whole-number volume ratios is itsel …