The double Sing-around method was conceived by which the difference ofsound velocities in sample liquid and in standard liquid would be preciselymeasured.The method could not be ultimately realized，but from the processto test the conception， an idea in which a binary scaler is combined to asingle Sing-around circuit was yielded. It was confirmed by experiment andtheory that the latter method has a comparable precision to and muchsimpler circuit construction than the former. By this improved Sing-aroundmethod，velocities in dilute water-solution of alkali-halide could be measuredin the concentration range 0.01～0.05 mol/1.
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