Colloidal Silver 500 PPM- {PPM =s Parts per million}. In 1912 an article in the “The Lancet” compared various concentrations of Colloidal Silver for efficacy. The authors of the article determined that 500 PPM or above was the most reliably effective concentration. Amino Acid & Botanical Supply colloidal silver which is made electrostatically to drive individual molecules of silver of therefore very small particle size into colloidal suspension in triple-distilled water is 500 parts per million plus or minus 50 P.P.M. Assay of particle size as well as concentration in P.P.M. Available by calling 1-{800}-952-7921.