HI70004C is a premium quality pH 4.01 calibration buffer that is NIST traceable and supplied with a Certificate of Analysis. Each sachet has the lot number and expiration date stamped on it and is made of light block foil ensuring freshness each time one is opened. Hanna's line of technical calibration buffers have been specially formulated to have an expiration of 5 years from the date of manufacture for an unopened sachet. The HI70004C is for 25 sachets containing 20 mL of buffer. Supplied with Certificate of Analysis Accuracy of +/- 0.01 pH @ 25°C Temperature chart of the actual pH value at various temperatures printed on each sachet HI70004C is a premium quality pH 4.01 calibration buffer produced in accordance with ISO 3696/BS3978 standards using high purity salts, deionized water, certified weight-checked balances, and Class A glassware in a temperature controlled environment monitored with certified thermometers. Reported values are accurate to +/- 0.01 pH @ 25°C and are traceable to NIST Standard Reference Materials (SRMs). The HI70004C is supplied with certificate of Analysis Product code Lot number Mean lot value SRMs that were used Manufacturing date Expiration date Convenience of individual packaging Ideal for users that do not calibrate frequently Ideal for field use due to portability Every sachet is as fresh as the day it was packaged Light block packaging prevents oxidation from UV light that could alter the buffer value Each sachet marked with lot number and expiration date. Hanna buffers are specially formulated to have an expiration of 5 years from manufacture for an unopened sachet. Color coded label for easy pH buffer value identification Easy to identify different buffer values Solution does not contain any dyes that may stain the reference cell of a pH electrode