We use to have to test each lot and shipment of chlorx coming in to the hospital by spec gravity. We used a refractometer and had a chart that would allow us to get a 6000 ppm dilution for sanitizing surfaces. We logged each test and the variances would astound you even with in lot test. The hospital where I work doesn’t test due to the HIV scare is winding down. Like Richard mentioned you may have to test each time.
Steve