The effects of Ammonia on the electrification of freezing and splashing water drops

Experiments were undertaken in which 2 mm diameter water drops contaminated with NaCl and/or (NH₄)₂CO₃ were allowed to fall through a cold environment and impinge on an ice target. Charge deposited on the target was measured as a function of environment temperature (0°C to −30°C) and concentration of the solution (10−6 M to 10⁻² M). Maximum negative charge of 2.04 esu/g was produced by 10⁻⁴ M NaCl at an environment temperature of −20°C. Maximum positive charge of 2.79 esu/g was produced by 10⁻³ M (NH₄)₂CO₃ at an environment temperature of −30°C. It was possible to suppress and even reverse the usual negative charge of salt by mixing with ammonia, suggesting the possibility of modifying thunderstorm electricity. All solutions weaker than 10⁻⁵ M gave complictated waveforms with a net negative charge.