YSI 9300 Photometer - Manual (Page 60)

Test Procedure
1 Filter sample if necessary to obtain a clear solution.
2 Fill the test tube with sample to the 10 ml mark.
3 Add one Calcicol No 1 tablet, crush and mix to dissolve.
4 Add one Calcicol No 2 tablet, crush and mix to dissolve.
5 Stand for two minutes to allow full color development.
6 Select Phot 12 on the photometer for result as mg/l CaCO
3
, or Phot 60 for result
as mg/l Ca.
7 Take photometer reading in the usual manner (see photometer instructions).
Interferences
1 Magnesium hardness (up to 200 mg/l as CaCO
3
) does not interfere with the
test.
2 Iron at levels above 10 mg/l may cause low results. Zinc above 5 mg/l may
cause high results.
3 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 results 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.
Results may also be expressed as mg/l Ca. To convert mg/l CaCO
3
to mg/l Ca
multiply by 0.4.
2 Magnesium hardness may be determined using the YSI Magnecol method (see
PHOT.21), or by taking the difference between the Total Hardness (PHOT.15)
and Calcium Hardness test results.
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