Patent ID: 8171956

Claim:
A liquid supply method that prepares a solution by continuously supplying a supply liquid to a primary fluid that is circulating in a primary fluid circulation tube, that uses a liquid supply apparatus that comprises: a supply section that delivers the supply liquid; and a supply liquid circulation tube formed in a hollow fiber shape that causes the supply liquid to flow from the supply section to the primary fluid circulation tube, the internal diameter of the supply liquid circulation tube being between 0.05 and 0 0.5 mm, when the supply solution is supplied from the supply section to the primary fluid circulation tube via the supply liquid circulation tube, a pressure P 1 of the supply liquid in the supply section and a pressure P 2 of the primary fluid in the primary fluid circulation tube always satisfy the formula P 1 −P 2 >0; P 1 /P 2 is 1.01 to 10; P 1 is controlled so as to maintain a constant level; the primary fluid is ultrapure water; the supply liquid is an electrolytic aqueous solution; and an electrolyte concentration of the primary fluid to which the supply liquid is supplied is between 0.00001 and 0.1 percent by mass, wherein a supply quantity of the supply liquid can be determined without performing feedback control, the supply liquid circulation tube is made from a material selected from the group consisting of fluorine resin and poly(4-methylpentene-1) based resins, and a ratio X/Y between a flow quantity X of the supply solution and a flow rate Y of the primary fluid is between 1/1000000 and 1/1000.