Notes to the text 1. the results are ... reported in per cent by volume rather than per cent by weight - результаты даются в
процентах относительно объема, а не относительно веса
2. over the course of the analysis - в течение всего процесса анализа
SOME PHYSICAL METHODS USED IN GAS ANALYSIS The relative proportions of various components of gas mixtures can be determined by merely measuring some physical constants of the mixture: the density, the viscosity, the thermal conductivity, heat of combustion, ionization potential.
Condensation methods are often applicable in the separation of complex mixtures of gases. This method has been applied to the gases of the argon group and of natural gas mixtures.
The application of the methods of mass spectrometry to gas analysis has been extensive. The use of a mass spectrometer in analysis enables one to determine the components of mixtures of hydrocarbons, fuel gases, rare gases, etc.
Thermal conductivity applied to gas analysis is rapid, simple to carry out and adaptable to continuous operation .and process control. Some attempts to apply the methods of emission and absorption spectroscopy to gas analysis have been made.
Other miscellaneous methods include magnetic susceptibility, micro-wave analysis, acoustical method based on the principle that the velocity of sound in a gas is a function of the molecular weight of the gas, inferometric methods, diffusion methods and others.
Notes to the text 1. enables one - обеспечивает
2. simple to carry out - прост в производстве
3. based on - основан на
ANALYSIS OF MIXTURES Many problems of quantitative chemistry are more complex than determining the amount of a pure substance or the composition of an aqueous solution of a pure compound. Often the problem arises simply because the compound or solution has an unknown or complex composition.
There are three fundamental schemes than can be used in the problem at hand.
1. Phase separation: The metal ion, A, can be determinedwithout interference front B if we separate A from B. We do this by preparing a two-phase system such that all of A is in one phase and all of B is in the other phase.
2. Selective determination: The metal ion, A, can be determined in the presence of B if we can find a determination which is selective toward A, ignoring B.
3. Combined determination: The two metal ions, A and B, can be determined together.
This type of measurement combined with another independent measurement gives the amount of each ion.