ffem builds water and soil tests based on colorimetry or titration. We ocassionally ship third party meters to complete functionality provided by our kits.


Colorimetry is principle of measuring the concentrations of analytes by measuring a change in colour induced by a reagent. Usually this would be done by eye comparing against a colour card in the field, or using a colorimeter, or for best results, using a spectrometer. ffem’s colorimtric tests work by using the camera on an Android phone and produces results that are close to that of a standard laboratory test.

Before you begin to test using colorimetry, you need to calibrate your phone. The calibration step creates an internal table with which colours captured by the camera are compared with. There are two kind of calibrations offered: the minimal calibration and the complete calibration.

Colorimetric testing is carried out by mixing the sample with the reagent in the quantities and method specified. The resulting solution is then placed in the appropriate cuvette. Clip the ring light over your phone and turn it on to its brightest setting. Place the cuvette under the light stand and the phone over the light stand. Position the cuvette so that it is directly under the camera and the sampling circle is in the brightest central spot. On analysing the colour, the app with match it with the calibration table and produce an interpolated result.

The exact steps to be followed for testing are listed against each parameter.


ffem offers some simplified titration tests. First the sample is to be prepared for titration by adding one or more reagents. Add the titrant dropwise to the sample and shake, while keeping count of the drops. At some point there will be a colour change, the app will convert the number of drops added till the change in colour to the concentation of the analyte.

The steps to be followed for each titration is listed against the respective parameter.