M 6038 (OTTO) Magnesium chloride, puriss, 99.99% Cas 7786-30-3 - used for dust control, and road stabilization. M 6038 (OTTO) Magnesium chloride, puriss, 99.99% Cas 7786-30-3 - used in fire extinguishers, polymerase chain reaction (PCR) and hydrogen storage. It is a precursor for magnesium metal and other magnesium compounds.