pH test (phenol red method)

The test kit consists of a measuring tube with lid and color comparison scale as well as 20 phenol red tablets.
The test tube is rinsed with the water to be tested and then filled up to the 10ml mark. Add a tablet, close the lid and swivel the tube until the tablet has completely detached. Now the pH value can be determined by comparing the water color with the color gamut next to the tube.

Replacement tablets are available in a pack of 10.

Why Phenolred? Isn't that an 'old hat'?
The method has indeed been known for a very long time and is or has been used in many applications in medicine and biology. In the professional laboratory, this pH test has long since been replaced by electronic measurement methods, because they are much more precise and cover a wider area; but it has a decisive advantage for the non-professional user: it is relatively reliable!
Electronic measuring instruments must be constantly calibrated, and the correct measurement requires experience. With only occasional use and insufficient training and experience of the user, the risk of measurement errors is very high - especially with simple hand-held measuring devices.
In short, the electronic meter provides a very precise value with two decimal places, but this may be completely wrong. The phenol red test provides an inaccurate value, but it is reliable.