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UK: Manual for Colombo Aquatests
General Guidelines
• Always take care that the test tube is clean before use.
• Clean the tube directly after use.
• Take the volume of the water sample as precisely as possible.
• Keep the drop bottle perfectly vertical during dropping.
• Take care that no air bubbles are included in the drops.
For judging the colour of the water sample after adding all the test
fl uids, proceed as follows: put the test tube on the included colour
chart and look through the tube on to the chart from directly above it.
Do not look in direct sun light, but at indirect light. Compare the colour
of the water sample with the colours on the chart. The closest colour
shows the corresponding value. Generally the colours of the sample
and on the chart will not be exactly the same, as values in practice will
always be between the standard values, and thus a mixture of both
consecutive values. Therefore, one should estimate between which co-
lours the sample really lies.
In the test where drops are to be counted, like KH and GH, the mo-
ment at which the colour changes is the point at which the true value
is reached. The number of drops added to reach that point can be
converted to the true value. The colour change is reached within one or
two drops. Within the one or two drops the sample has an intermediate
colour. The true end value is only reached when the colour doesn’t
change anymore. These Colombo-tests are calibrated with professional
laboratory tests, ensuring the most precise test possible.
