The application of Cherenkov photometry gives a new possibility in isotope dilution analysis for determination of specific
activity in a simple way. If the compound of the isotope is coloured or it can be converted into a coloured compound, it is
possible to measure the activity and the concentration of the compound in one sample in one series of measurement. Methods
were worked out for the determination of32P specific activity by measuring the32P efficiency, activity and the phosphorus content of the same sample. It is possible to measure the specific activity in an
automatic mode with some modification of the liquid scintillation spectrometer.