Principle

The pH value of the soil, whether the soil is acidic or basic.

Calibration

pH standards based on buffer solutions should be supplied to you. You shoule have standards of pH 4, 5, 6, 7, 8, 9 and 10.

Take 5 ml of the pH standard, say 4, and add 1 drop of the pH indicator.

  • Take the resulting coloured solution and fill it into the white cuvette provided.
  • Place the cuvette under the light box and turn it on.
  • Place the phone over the stand.
  • Go to Settings > Colorimetric Test > Calibrate and choose pH.
  • Select the calibration point, 4 in this case.
  • Click on Start Camera.
  • Position the cuvette so that the middle, most uniformly lit portion is within the circle.
  • Select Analyze.
  • You should have your first calibration point. Repeat similarly with the other calibration points.

Extraction

  • Take 5 ml of soil in the measuring spoon.
  • Fill 25 ml of distilled water in the measuring tube, and add the 5 ml of soil.
  • Close the tube, shake well and leave to settle.
  • Filter out the top clear layer of extracted solution.

Test

This test uses the pH indicator.

  • Collect 5 ml of extracted solution, add 1 drop of pH indicator and place in the white cuvette.
  • Place the cuvette under the light box and turn it on.
  • Place the phone over the stand.
  • From the home screen choose Colorimetric Test > Soil > pH.
  • Choose No Dilution if this is the first test, you might have to dilute the sample and retry later if you get an error.
  • Click on Start Camera.
  • Position the cuvette so that the middle, most uniformly lit portion is within the circle.
  • Select Analyze.
  • After some time, the app will display a result.