Experimental study of absorbency,concentration and the ratio of degradation's changes when power ultrasonic irradiates p-nitrophenol(PNP)liquor that original concentration is 117mg/L after 60 minutes.The result shows that the PNP solution's ratio of degradation within the frequency's scope from 368kHz to 1.7MHz decreases with the frequency increases,and the absorbency of solution and the PNP's concentration increases with the frequency increases,and the rate of changes change sharply in the scope of frequen...