OBITUARY NOTICES. 
Professor A. W. Williamson. By Professor 
A. Crum Brown. 
(Read January 8, 1906.) 
Alexander William Williamson was bom at Wandsworth, May 
1st, 1824. He studied chemistry under Gmelin in Heidelberg 
and under Liebig in Giessen, where he graduated as Ph.D. In 
1848 he studied mathematics under Comte in Paris. In 1849 he 
was appointed Professor of Practical Chemistry in University 
College, London ; and in 1855, in addition, Professor of Chemistry. 
He was elected Fellow of the Royal Society of London in 1855, 
and was Foreign Secretary of the Society from 1873 to 1889, and 
Vice-President in 1889, 1890. He was President of the British 
Association in 1873. He was elected Hon. Fellow of this Society 
in 1883. In 1887 he resigned his chair and retired to Haslemere, 
where he died May 6th, 1904. 
Williamson’s chemical work was not great in quantity, but was 
of the very highest importance, and his name will always remain 
in the history of chemistry in the list of the great leaders. 
Berzelius gave H 2 0 as the formula of water, but the duplicity 
of the hydrogen in this formula was deduced from physical 
considerations only, and was not used to explain any chemical 
phenomena. The chemical unit of hydrogen was to Berzelius and 
his followers the “ equivalent ” H 2 and not the atom H, and they 
wrote hydrochloric acid and ammonia H 2 C1 2 and U 2 H 6 , until a 
special symbol, a barred letter, was invented for the equivalent in 
the case of each element the equivalent of which consisted of two 
atoms. It was Williamson who brought to light the chemical 
meaning of the 2 in H 2 0, and showed that these two atoms are 
not permanently tied together, but are each separately united to 
the one indivisible atom of oxygen. 
By the action of potassium on alcohol one-sixth of the hydrogen 
