YSI 9300 Photometer - Manual (Page 66)

Test Procedure
1 Filter sample if necessary to obtain a clear solution.
2 Fill test tube with sample to the 10 ml mark.
3 Add one Hardicol No 1 tablet, crush and mix to dissolve.
4 Add one Hardicol No 2 tablet, crush and mix to dissolve. Ensure all particles
are completely dissolved.
5 Stand for two minutes to allow full color development.
6 Select Phot 15 on the photometer.
7 Take photometer reading in the usual manner (see photometer instructions).
8 The Total Hardness result is displayed as mg/l CaCO
3
.
Interferences
1 Unusually high levels of iron (above 10 mg/l) will cause low results for total
hardness.
2 The pH required in the test is closely controlled by a buffer mixture included
in the tablet formulation. However, to avoid exceeding the buffer capacity
strongly acid or alkaline samples should be adjusted to within the pH range 4
to 10, prior to the start of the test.
Notes
1 The expression of hardness results sometimes causes confusion. It is normal
practice to express the result of hardness tests as mg/l CaCO
3
(calcium
carbonate). This is merely a convention to allow the comparison of different
results and does not necessarily indicate that the hardness is present in the
water in this form.
2 This test measures total hardness. For the specific measurement of calcium
hardness or magnesium hardness refer to the YSI Calcicol (PHOT.12) and
Magnecol (PHOT.21) tests respectively.
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