Field and Laboratory Methods Used by the Geological Survey of Canada in Geochemical Surveys

Résumé du livre

The following is a method of determining light hydrocarbons in soil by gas chromatography. To prepare the sample the soil is dried at 110°C, lightly crushed and sieved through a 200 mesh Tyler screen. A weighed portion of the minus 200 mesh fraction is placed in a reaction flask and the system evacuated. The sample is heated after addition of 2N hydro chloric acid and the evolved gas passed through a series of traps to remove C02 and moisture. The hydrocarbons are finally removed in a trap immersed in liquid nitrogen. The last trap is removed from the system, brought to room temperature, and attached to a gas chromatograph. The gas mixture is flush e d in to the instrument, the hydrocarbon components separated, and determined quantitatively by means of a hydrogen flame ionization detector. Fourteen or fifteen samples may be processed per 8-hour day with a precision of + 10 per cent.