Product Short Description: Metal-indicator complexes red indicator to Blue colour changes VERY SIMPLE to TEST Product Description: This test measures the amount of soluble calcium and magnesium ions in a mud filtrate. When measured simultaneously, the result is called total hardness. The calcium ion concentration can be determined separately and when it is subtracted from the total hardness, the magnesium ion concentration can then be determined. Different buffer-indicator combinations may be used for these determinations. It is imperative however not to intermix the various buffers and indicators.