Its a solution made up of water, Amonia-Amoniun chloride with Black T. Its used in the titration process, used to check the thickness of water.
A certain amount of Carbonates of calcium and magnesium is usually present in water and this amount varies in different sources of water. In fresh water a little of these carbonates is present but in well water they are found in larger quantities. These compund interfere with the lather producing and cleaning action of soap. A soap is a sodium or potasium salt of long chain fatty acids like palmitic acid(found in palm oil).
So its has disadvantages. That's why we used this solution to know the thickness of water, in case if it's too hard for use it's transferred to RO(reverse osmosis) Plants.
