Marketing InformationThis 250 mL bottle ProCal™ primary turbidity standard has been certified by HF® Scientific for use in the Hach® 2100N turbidimeter (0.0, 20,200,1000, 4000 NTU). No formazin is used, making the standard safer, easier to use, accurate and less expensive that the equivalent Hach® product. In addition to being approved by the EPA, ProCal™ has been certified through testing conducted by HF® Scientific demonstrating that ProCal™ performs as well as Hach® primary turbidity standards in selected Hach® instruments.