GB491154A - Improvements in and relating to the determination of small quantities of gases or vapours in gaseous mixtures - Google Patents

Abstract

In determining a constituent (e.g. water vapour) of a gas mixture by measuring the heat of its absorption in sulphuric acid, a thermometer irrigated with the acid is subjected to a gas current of such cross-section that the outer portion of the current escapes the action of the absorbent, and preferably not more than 33 per cent of the absorbable constituent is absorbed from the whole of the gas passed. The relative rates of flow of the gas and the acid are such that the greater part of the heat of absorption is carried away by the gas, and a rate of gas flow is selected of which small variations do not appreciably affect the sensitivity of the instrument. The apparatus comprises two mercury thermometers 4, 5 inserted in passages in a block of metal 3 through which the gas is passed in series. The second thermometer 5 is surrounded by a coil 7 of platinum wire and irrigated by sulphuric acid from the siphon 8. A modified apparatus comprises two similar devices in parallel, the gas being passed directly through one while the other is preceded by a catalytic or other reaction chamber in which one of two constituents is modified before absorption, enabling <PICT:0491154/III/1> them to be separately estimated. For example ammonia and water vapour may be estimated together in one branch of the apparatus while the water vapour alone is measured in the other branch, the ammonia having previously been decomposed by passage over a catalyst. Also non-absorbable constituents, such as oxygen in a hydrogen-containing gas, may be converted by previous reaction into absorbable constituents such as water vapour.