2447700 Total Hardness Reagent Set, Buret, HR, 100-25000 mg/L CaCO₃

Total Hardness Reagent Set measures total hardness in the range from 100 to 25000 mg/L as CaCO₃ in water, wastewater and seawater. Article 2447700 uses EDTA Titration method (8226). The product may be used to perform analysis of 100 samples.

Total Hardness Reagent Set includes:

• ManVer 2 Hardness Indicator Powder Pillows (p/n 85199)
• Hardness 1 Buffer Solution (p/n 42432)
• EDTA Standard Solution, 0.200 N (p/n 102149)

Before starting analysis:

• It is recommended to collect samples in glass or plastic bottles cleaned with a detergent and rinsed with 1:1 nitric acid and deionized water.
• It is required to dilute the sample with deionized water if the sample volume is less than 50 mL.
• It is necessary to adjust the pH to 7 with sodium hydroxide solution before analysis.

Procedure for CaCO₃ determination

In order to conduct total hardness analysis, choose sample volume and titrant. Add titrant to the 25-mL buret and fill 250-mL Erlenmeyer flask with the sample. Pipet 1mL of Hardness 1 Buffer Solution and swirl the content of the Erlenmeyer flask. Pour the content of the ManVer 2 Hardness Indicator Powder Pillow and swirl to mix. Continue adding titrant from the buret until the color changes from red to pure blue and calculate the concentration:

mL of titrant × multiplier = mg/L Ca as CaCO3.

Summary of method

A buffer solution adjusts the sample pH to 10.1. An organic dye, calmagite, is the indicator for the test that enters into reaction with calcium and magnesium ions and gives red complex. The EDTA reacts with all of the free calcium and magnesium ions in the sample. After the EDTA reaction with all of the free magnesium ions, the EDTA removes the magnesium ions from the indicator that changes from red to blue.

Sample preparation

It is required to adjust the sample pH to 2 or less with concentrated nitric acid to conserve the sample for later analysis. It is recommended to store the sample at the temperature below 6 °C (43 °F) for up to 7 days.