Packaging has been designed to keep air and light from damaging the solution. TDS solutions are produced with high quality potassium chloride in various concentrations. They are standardized using a conductivity meter calibrated with NIST potassium chloride. TDS value: 1500 ppm ( milligrams per liter) at 25 degree C. TDS conversion factor 4-4-2: 0.65 ppm = 1 microsiemens/cm (approximately). Size: 500ml.