Myron L pH Buffer Solutions are factory calibrated with NIST traceable standard solutions having specific conductivity/ppm values. Myron L Company standard solutions are made under strictly controlled conditions using reagent grade salts. These salts are mixed with deionized water having a resistivity of at least 5 megohms-cm purity. pH solutions are mold inhibited and accurate to within + 0. 01 pH units @ 25C and are traceable to NIST certified pH references and are color-coded for instant identification.