pH – its the level of acidity or alkalinity. In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. pH stands for the power or potency of Hydrogen. pH of water is around 7. Gastric acid sits at 1 while bleach measures at 13. Wikipedia has a colorful scale.
Upendra, my uncle who farms in Bhagmalpur, has asked me about pH meters to help with assessing the soil on different fields he has. The pH of a field may determine its suitability for a crop or what needs to be added to the soil so that he can grow a certain crop (sugarcane, peas, mustard, wheat, etc.). There are several simple pH meters available at Home Depot in the garden section, but the fact that they have XOs now leads to a new possibility.
We recently did some fun experiments with Copper and Zinc nails during a recent OLPC San Francisco meeting. Stick the nails into a lemon (acidic solution) and fire up the Measure Activity. Then strip bare a earphone cable or fashion one using a 3.5mm TRS (Tip-Ring-Sleeve) mono audio plug. The minute amount of electricity generated by the electrodes plugged into the lemon can then be measured by the Measure activity.
I wonder if the pH of a soil sample can be measured this way, using two electrodes and the Measure activity. One major hurdle would be calibration of scales in Measure, but using some referential samples, we should be able to “zero” the scale.
Perhaps an exercise for Arjun?