Standard Radium Solution for Drinking (c. 1915-1920) - This bottle (empty) of radium water was produced by the Standard Chemical Company of Pittsburgh. The recommended dose was 1 bottle after every meal. Each bottle contained a maximum-equilibrium constant of radium emanation [radon], 5400 mache units. One mache unit represented 364 pCi of radon per liter. Today, the maximum containment level for radium in public water supplies is 5 pCi/L.