Visual Kits

Range	MDL	Method	Kit Catalog No.	Refill Catalog No.
50-500 ppm as CaCO3	50 ppm	EGTA (calcium)	K-1705	N/A
100-1000 ppm as CaCO3	100 ppm	EGTA (calcium)	K-1710	N/A
2-20 ppm as CaCO3	2.0 ppm	EDTA (total)	K-4502	N/A
20-200 ppm as CaCO3	20 ppm	EDTA (total)	K-4520	N/A
100-1000 ppm as CaCO3	100 ppm	EDTA (total)	K-4585	N/A
250-2500 ppm as CaCO3	250 ppm	EDTA (total)	K-4530	N/A

Hardness (calcium)

The EGTA Method 

Reference: West, T. S., DSC, Ph.D., Complexometry with EDTA and Related Reagents, 3^rd. ed., pp. 46, 164 (1969).

The EGTA method is specific for calcium hardness. The EGTA titrant in alkaline solution is employed with a zincon indicator. Results are expressed as ppm (mg/L) CaCO₃.

 

Shelf-life: eight months. Although the reagent itself is stable, the end point indicator has a limited shelf-life. We recommend stocking quantities that will be used within seven months.

 

Hardness (total)

The EDTA Method

References: APHA Standard Methods, 21^st ed., Method 2340 C (2005). USEPA Methods for Chemical Analysis of Water and Wastes, Method 130.2 (1983).

The total hardness method is applicable to drinking, surface, boiler, and brine waters.

 

The EDTA titrant is employed in alkaline solution with a calmagite indicator. This method determines the combined calcium and magnesium concentration of a sample. If no magnesium is present, the end point of the titration normally appears sluggish. Results are expressed as ppm (mg/L) CaCO₃.