METHOD FOR SAMPLING LIQUID

PURPOSE:To facilitate sampling by interrupting the gas supply into a vessel by a 1st piping switching means, stopping the discharge of liquid from the vessel by a 2nd piping switching means, reducing the pressure in the vessel via the 1st piping switching means, sucking the liquid via the 2nd piping switching means and transferring the liquid into the vessel. CONSTITUTION:The front end of the piping 45 is immersed into the liquid chemical 20 in a tank 5. Three-way valves 31, 32 are controlled to discharge the gas 2 remaining in a bottle 4 by a pump 1 and to store a prescribed volume of the chemical liquid into the bottle 4. The valves 32, 31 are controlled to feed gaseous N2 2 of a specified pressure through a pressure valve 7 and to inject the gas into the bottle 4 after dust is removed therefrom by a filter 8 to prevent the foaming of the liquid chemical. The quantity of the fine particles in the liquid chemical 20 is measured by a measuring instrument 6 and the liquid is discharged as a waste liquid 20a via a flow rate control valve 9 and a flow meter 10. The liquid is easily and rapidly sampled according to this method.