Description
Three envelopes pH 4.0, 4 envelopes pH 7.0, 3 envelopes pH 10.0. Each envelope makes 500 mL of solution. Includes one vial of preservative solution. Powders keep 5 years; prepared solutions keep 3 weeks (or 3 months with preservative added). Preservative contains a pH indicator and colors each buffer solution for easy identification.