Alkalinity
Reagents
LaMotte total alkalinity indicator, Part # 7038-G (Amazon $12.94)
Baking soda
Distilled water
Prepare Calibration Solutions
Weigh out 12.63 g of baking soda. Add to 500 mL of distilled water. Mix until dissolved.
Dilute 100-fold to yield a 8.42 dKH (150 ppm CaCO3 equivalent) working stock.
Dilute the working stock as outlined in the Table below
Method
To each 5 mL sample, add 5 drops of alkalinity solution. Cap and mix by inverting tube several times. An image of all of the calibration solutions after the reagents are added is shown above.
Transfer approx. 1mL of each calibration solution to a cuvette.
In the colorimeter plotting program, select the custom 610 nm LED and ppm as units. Calibrate the colorimeter with the 0 ppm alkalinity solution and measure absorbance of all of the solutions in duplicate.
Sample calibration data
To view/use: Download the file and open in the colorimeter plotting software as described here.