Patent GB-884146-A (GB)
Title: Analysis of gases emanating from solids and liquids
IPC: G01N31/12
Filed: 1958-08-22
Abstract: Combustible gases which can be evolved from a solid or liquid substance are determined by contacting said substance with a stream of carrier gas to which is added before or after contact sufficient oxygen to react with any combustible gas picked up, passing the gas through a combustion chamber and leading the resultant product gases through a continuous oxygen analyser, the reduction in the output signal of which compared with that given before combustion or when the gases by-pass the combustion chamber is a measure of the quantity of combustible gas evolved. The oxygen analysis may be performed by known electro-chemical reduction, galvanic, coulometric, polarographic or magnetic methods.  The oxygen, e.g. as air may be added to the gas stream e.g. by means of a liquid piston syringe (literature reference given) or by passing the carrier gas through the anode compartment of a cell in which acidified water is decomposed electrolytically. Combustion may take place in a heated tube and be facilitated by a hot filament or catalyst bed.  The following analyses are exemplified or referred to: (1) hydrogen in a series of steel samples contained in a single quartz tube using nitrogen from which moisture and oxygen are eliminated as carrier gas, successive samples being heated with a travelling furnace to 1000 DEG  C. when the result from the previous sample has been obtained, oxygen added to the resultant gas stream and the mixture passed through a further quartz tube containing a platinum on silica wool catalyst heated to 5-600 DEG  C., (2) determination of hydrogen evolved from aluminium, (3) determination of the vapour pressure of a sparingly volatile organic substance by passing nitrogen containing a small amount of oxygen over the sample and passing the mixed gases through a mullite tube at 1500 DEG  C.  By exposing a large surface area of the sample, equilibrium conditions are established and the vapour pressure obtained, (4) determination of permeability of a metal membrane to hydrogen in which a stream of dry, oxygen-free argon is passed through a tube surrounded by oxygen: the permeability of other metals or of rubber, plastics or ceramics to hydrogen and carbon monoxide may be similarly determined, (5) determination of hydrogen dissolved in water (e.g. as a continuous stream) by scrubbing the water with nitrogen, passing the gases through an oxygen absorbent, and adding a constant amount of oxygen before combustion: the nitrogen may be recirculated, together with additional make-up nitrogen.  If not all the hydrogen is removed from the water, calibration e.g. when p  a mixture of hydrogen-free and hydrogen-saturated water is necessary.  Dissolved organic matter, if at least sparingly volatile can be similarly determined, (6) determination of oxygen in a metal or oxide by analysis of carbon monoxide released from a sample melted in a graphite crucible and similarly determining carbon in a metal by melting in the presence of an excess of reducible oxide, (7) determination of methane derived from magnesium iodide with an "active" organic hydrogen atom; determination of acetylene from carbide and moisture; and estimation of efficiency of hydrogen carrying catalysts by determining the rate at which they cause hydrogen to be evolved from aqueous hypophosphite.