PURPOSE:To measure exactly the concn. of the salt content in sand with high reliability by measuring the concn. of the salt content in washing liquid for agitating and washing the sand. CONSTITUTION:A driving device 11 is controlled via a control circuit 10 during the prescribed time set by a timer circuit and the sand through a sand measuring part 5 is supplied together with the washing liquid through a water measuring part 6 to an agitator 2, by which the sand is washed and the salt content of the sand is removed. The salt content in the washing water is detected by a sensor 8 to which a measurement signal is applied from the oscillation modulating circuit of the circuit 10. The salt content in the sand is converted and discriminated by the built-in detection signal adjusting circuit in accordance with the ratio of the amt. of the sand supplied and the amt. of the washing water when the detection signal is supplied thereto. The circuit 10 controls a concn. display device 12. The concn. of the salt content in the sand is thus exactly measured with high reliability even during the removal of the salt content.
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