Fundamentals of multi-element analysis with electron and beta radiation. 4

Mass attenuation coefficients of liquid hydrocarbons and their oxygen, nitrogen and halogen derivates have been measured and compared with the values obtained according to the various calculation instructions (see pt.3). Using the most complete formula according to Schmidt the values obtained are systematically too low (up to 5 per cent), even with best parameter values. Only about half the values deviate by less than 3 per cent. Though the maximum deviations of 5 per cent are beyond the experimental errors (<= +-1 per cent) and the errors introduced by adaption of the general function to the mass attenuation coefficients of elementary absorbers (<= +-2.5 per cent), certain systematic deviation patterns (< 2.5 per cent) can be observed only for individual homologous series (alkanes, benzene derivatives), which may be caused by bonding effects or by remaining shortcomings of the model. The simple formula μsub(Σ) = Σpsub(i)μsub(i) provides effective mass attenuation coefficients, the error of which is up to 10 per cent. (author)