PURPOSE: To always feed same quantity and quality of a volatile soln. in the state of constant temp. and concn. by storing the prescribed quantity of the volatile soln. in such a state that volatilization of a solvent is controlled, namely without changing the concn. at the prescribed temp. in a storage part with a collecting means and a feeding means.

CONSTITUTION: A volatile soln. of quantity correspondent to the quantity of the volatile soln. dropt at once is stored in an airtight state in the storage parts 15, 16 provided to the inside of a thermostatic chamber 14. Further the fed volatile soln. is collected to the storage parts with a first valve 17. Further more all the parts of the volatile soln. collected and stored in the storage parts are fed to a dropping port 33 by the means consisting of a gaseous nitrogen cylinder 12, a second valve 18 and a pipeline 34. As a result, regardless of the volatile soln., the solvent is not volatilized and the concn. is not changed and also the volatile soln. in the state regulated to the prescribed temp. can be dripped to the last from the first and dropt in equal quantity.