Abstract: The present invention provides an apparatus for performing a process for producing standard gas mixtures which entailspurifying a raw gas using a gas purifier (3) such as a known two stage gas purifier system, thereby generating a high-purity diluent gas;mixing the high diluent gas and at least one high-concentration standard gas, by generating a medium-concentration gas mixture; dividing the medium-concentration gas mixture into a first flow and a second flow;selectively mixing the first flow with a sample gas or a high-purity diluent gas or a mixture thereof, thereby obtaining a standard low-concentration gas mixture; andcontrolling the pressure of the sample gas, the second flow of the medium-concentration gas mixture and the standard low concentration gas mixture.

Abstract: The present invention provides a process for producing standard gas mixtures which entails purifying a raw gas using a gas purifier (3) such as a known two stage gas purifier system, thereby generating a high-purity diluent gas;mixing the high-purity diluent gas and at least one high-concentration standard gas, by generating a medium-concentration gas mixture;dividing the medium-concentration gas mixture into a first flow and a second flow;selectively mixing the first flow with a sample gas or a high-purity diluent gas or a mixture thereof, thereby obtaining a standard low-concentration gas mixture; andcontrolling the pressure of the sample gas, the second flow of the medium-concentration gas mixture and the standard low concentration gas mixture.

Abstract: This invention relates to a process for producing gas mixtures by a plurality of dilution steps of a high concentration standard gas with a high purity diluent gas. According to the invention, as soon as the high purity diluent gas is generated, no further contaminants such as gaseous impurities are added during the further mixing of diluting steps of the process. Only orifices or needle valves are used in the mixing or diluting lines while mass flow controllers and pressure regulators are placed upstream, at the output of the gas sources and/or downstream, i.e. in the gas-venting lines. The invention particularly applies to trace analysis of gas with Atmospheric Pressure Ionization Mass Spectrometry.

Abstract: A process for depositing tungsten silicide films on a silicon substrate by chemical vapor deposition, comprises the steps of producing a silicon sub-fluoride by passing SiF.sub.4 over pieces of silicon heated in a tubular oven about 1200.degree.-1500.degree. K., mixing gaseous WF.sub.6 with the silicon sub-fluoride, and then immediately depositing the tungsten silicide films on said silicon substrate.