by means of a computerized calculation program , a simplified estimate of the ion-activity product of calcium oxalate was derived ( ap ( caox ) -index ) , based on the 24-h urinary excretion of calcium ( ca ) , oxalate ( ox ) , magnesium ( mg ) , citrate ( cit ) and the urine volume ( v ) : ( formula : see text ) with urinary electrolyte values within the normal range , there was a good correlation between the ap ( caox ) -index and the more laboriously obtained ion-activity product ( r = 0.997 ) .
C0013832
electrolyte
C0022023
ion