Liquid Scintillation Counters measure beta-emitting isotopes by dissolving the sample in a scintillation cocktail, which converts each beta particle into a flash of light that photomultiplier tubes count. Counting efficiency reaches 50 to over 65% for tritium and 90 to 95% for carbon-14, the two main isotopes in tracer work. Quench correction by 3/2 and four-parameter fitting adjusts for colour and chemical quenching, converting counts to DPM, and an automatic changer runs 25 vials unattended. High-end models add alpha and beta discrimination across 3 to 10 MeV alpha and 0 to 5 MeV beta. Typical uses include tritium in drinking water, radiolabelled drug studies and receptor binding assays.