Urea compounds, complex treatment

Woehler published his modest memoir on the synthesis of urea in 1828 and a century and a quarter later Dr. Robert B. Woodward of Harvard University synthesized cortisone, a very complex hormone used in the treatment of arthritis. What a century of research between Woehler s urea and Woodward s cortisone Six hundred thousand compounds have been prepared in this branch of synthetic chemistry, while every year four thousand new ones are added. No wonder that when Gmelin was preparing his handbook of chemistry he pleaded for chemists to stop discovering to give him a chance to catch up with his work. Woehler, a modest man, would have been the last to claim for himself the distinction of being the forerunner of such tremendous achievements. 

Adductive crystallization, crystallization from a solution by forming an adduct (inclusion complex), such as with urea and thiourea as auxiliary substances is of increasing importance especially in crude oil treatment. Urea as a solid or a solution is added to the solution to be treated. A crystalline addition compound (an adduct) is formed with a straight-chain organic compound, which may then be mechanically separated from the remaining solution. This... 

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