Total hardness is the sum of amount of Ca2+ and Mg2+ ions and is determined via complex-titration. Here is the stoichiometric point found by using different complex ions with different colours. The solution is titrated with ethylenediaminetetraacetic acid disodium salt or in other words with trilone-B solution which can be simply notated as Na2H2Y
Na2H2Y → 2Na+ + H2Y2–
Chromogen black ET-00 (eriochrome black T) is used to determine the total hardness of water. Along with the Ca2+ and Mg2+ ions it forms a lilac purple complex ion. So after adding the buffer solution and indicator ET-00, the solution containing Ca2+ …show more content…
The first was determinging the carbonate hardness. I started the experiment with washing the 100 cm3 pipette 2 times with a small amount of the test water. Then I washed the conical flask with distilled water and pipetted into the conical flask 100 cm3 of the test water. After that I added 3 drops of indicator mo or mr. The next step was preparing the burette, hence I removed any air bubbles from the nozzle and filled it with 0,025 M hydrochloric acid till zero (the lower meniscus has to coincide with the scales 0-notation). Then I titrated the water sample with a 0,025 M hydrochloric acid solution, while stirred the water in the flask with intense circular movements. At the stoichiometric point, the colour of the water changed from yellow to pink red. I then read the consumed volume of hydrochloric acid for titration from the burette with a 0,05 cm3 precision. The las experimental step was to wash the conical flask carefully with distilled water and to repeat the titration with a new amount of water. After this the following data was