While the instruments were making the measurements, which took a couple of days, the chemist turned to the remaining solutions and began the analyses for radium.
A painting being sampled under a stereo-binocular microscope.
Lead white weighing twenty-thousandths of a gram (20 milligrams). This is the amount needed to measure lead-210 and radium-226 to determine if the lead white is old.
In a series of chemical steps, he purified the solutions, removing the lead and other materials so that finally he had a small amount of solution that contained little else but the original radium and a very small amount of barium (an element that he deliberately added and one which is very similar to radium in its chemical properties). By adding dilute sulfuric acid, he prepared an insoluble material, barium sulfate, which was barely visible suspended in the solution.
Polonium plating apparatus. A heated solution of lead white in acetic acid is stirred with silver discs for 4 to 8 hours.
The disc above appears clean after removal, but on its surface it retains a minute amount of polonium which can be measured.