It is mixed, then separated, and the ether/oil layer is siphoned off. The bicarbonate of soda solution is discarded and the previous step (washing with pure water) is repeated twice. The ether is evaporated from the ether/oil solution, as was done previously in the first purification, using the stew pot apparatus. The pure ether is collected in the pan held in the colander. The oil now contains a much higher percentage of THC (determined by the amount of cannabidiol originally present). The THC is of the high-rotating isomeric form, and all of the toxins have been removed from the oil. THC is formal numbering and D1 is monoterpenoid numbering. Many readers especially those with some exposure to chemistry, may be curious about what happens to the molecules during the isomerization. The structural formulas for the reaction are given above (Fig. 2 .1B). For the non-organic chemist, this is an opportunity to overcome your fear of formulas. The first credits for finding this reaction go to Roger Adams, who first described it in 1940; a detailed account appeared in 1941 (Adams et al., 1941), but the correct formulas were not discovered until the 1960s.