In 1812 Davy, studying the action of carbonyl chloride on ammonia (22), first synthesized and described but did not recognize urea, “a salt perfectly neutral and dry, but deliquescent by attracting moisture from the air. It is remarkable that on the formation of this ammoniacal salt, gas (phosgene) combines with as much as four times its bulk of ammoniacal gas.” The reaction so accurately observed was:
COCI, + 4NHS = COCNIDi + 2NH4C1
Thus it was left for Wohler (88) to announce the synthesis of urea, making memorable the year 1828 and destroying the existing sharp demarcation between organic and inorganic matter. Seventeen years elapsed before the next synthesis of an organic compound—acetic acid by Kolbe. That the Wohler synthesis could be reversed and urea converted back to ammonium cyanate was not established until 1895 (79).
In 1773 Rouelle (64.) had obtained a "saponaceous extract of urine” by alcoholic extraction of evaporated urine. Twenty six years later Fourcroy and Vaquelin (81) obtained urea in a comparatively pure state from the same source and, recognizing it as a new compound, gave it the name urée.
Twenty years later Prout (62) devised a method for obtaining pure urea from urine and published the first analysis of this compound. In 1829 large quantities of urea were required in the Hospital of St. Antoine in Paris for conducting experiments (which were unsuccessful) on diabetics, and Henry (88) developed a method for preparing it in quantity from fresh urine through the use of lead salts for the removal of acids and mucous substances.