Abstract: A plastic coupling for plastic tubing having a groove annulus formed between a first circumferential groove on the outer periphery of the enlarged diameter portion of a connection tube and a second circumferential groove on the inner periphery of a cap nut 5 when the cap nut 5 is mounted on a joint body, and an enlargeable split ring having an internal diameter smaller than the external diameter of the enlarged diameter portion and loosely fitted into the second groove, the split ring being adapted to slide on the enlarged diameter portion to the first groove until the split ring falls within the first groove and is located within the groove annulus when the cap nut is mounted on the joint body.

Abstract: A method for recirculating a high-temperature etching solution according to the present invention comprises the steps of continuously removing, from a bath for etching a wafer for a semiconductor device, a portion of an etching solution contained in the etching bath, injecting a predetermined amount of pure water for adjusting the concentration of the etching solution into the removed etching solution, heating the resulting solution to a predetermined temperature, and recirculating the heated solution into the etching bath.