Colloidal zinc is a liquid dispersion consisting of water and zinc nanoparticles. The zinc is finely dispersed in distilled water.
In colloidal zinc, the concentration is measured in ppm, which stands for parts per million. This term actually refers to the ratio of the active ingredient (zinc) to one million parts of the solvent, suspension, or dispersion medium (water).
In the case of colloidal zinc, this measurement represents the weight ratio between the zinc and the water in mg/kg. Since 1 litre of water weighs 1kg, a concentration of 15ppm means that 15 milligrams of zinc are suspended in 1 litre of water.