Friedrich Woehler (1800-1882): From medicine to chemistry lab
FRIEDRICH WOEHLER was born on July 31, 1800 in Frankfurt-am-Main, the son of a veterinary surgeon.
After attending the local gymnasium from 1814 to 1820, he studied medicine at the Universities of Marburg and Heidelberg. Woehler qualified for the M.D. degree specialising in gynaecology but he never practised.
From childhood Woehler had a passion for practical chemistry. The year (1823-24) he spent with Berzelius in the analysis of minerals indeed shaped his career.
The friendship with Berzelius was strengthened through voluminous correspondence.
His teaching career began at an industrial school in Berlin (1825-31) and in Kassel (1831-36). He finally settled at Goettingen as professor of chemistry, which chair he held for 46 years.
Both as a teacher and experimenter, Woehler was outstanding. It has been recorded that about 8000 students passed through his hands!
Preparation of artificial urea
Woehler's work on derivatives of cyanogens began when he was still a medical student. He discovered cyanic acid. In 1823 he showed that cyanogens and aqueous ammonia yielded onalic acid and a white crystalline solid that was recognised as `urea'.
Woehler considered this as a remarkable example of the preparation of a substance of animal origin from inorganic materials. The idea seemed to have come from his medical interests, as he observed the conversion in the human body of chemicals taken orally and extracted in urine.
From the study of benzoyl, (C{-7}H{-5}{-0}), he proposed the concept of compound radicals, which brought the beginnings of order into the then dreadful confusion of organic chemistry.
Extraction of aluminium
Earlier, Davy attempted in 1808 electrolysis of alumina and Brezelius succeeded in using mercury as a cathode for the electrolysis of moist lime.
But alumina would not yield aluminium for him or for Davy. In 1825, Oersted prepared aluminium chloride by a new method and decomposed it with potassium amalgam and distilled the product. But it did not yield pure metal.
Woehler obtained permission from Oersted — truly following an ethical consideration, and improved the method. His technique was to cover a small quantity of potassium in a platinum crucible with excess aluminium chloride and to heat the covered crucible gently. This yielded pure aluminium.
When aluminium became a common metal, Woehler was honoured by Napolean III. Subsequently, Woehler used the same technique to extract beryllium.
Some of his methods have since been developed industrially: the preparation of phosphorus by heating calcined bone with sand, the production of acetylene from calcium carbide by heating together zinc, calcium and carbon (1862).
Honours
Woehler received several honours: F.R.S. (1854), Officer of the Legion of Honor (1864), the Copley Medal (1872).
Woehler's most distinguished student was Hermann Kolbe and the latter and Liebig remained his life-long friends (1822). He continued to be a teacher, taking interest in what went on in his laboratory even in old age, till the end (September 23, 1822).
R. Parthasarathy
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