o chemical research in
1851, when they prepared cyanamide by the action of ammonia on cyanogen
chloride in ethereal solution. In the same year he was appointed
professor of physical chemistry at the National College of Alexandria,
where he discovered that aromatic aldehydes are decomposed by alcoholic
potash into a mixture of the corresponding acid and alcohol, e.g.
benzaldehyde into benzoic acid and benzyl alcohol ("Cannizzaro's
reaction"). In the autumn of 1855 he became professor of chemistry at
Geneva university, and six years later, after declining professorships
at Pisa and Naples, accepted the chair of inorganic and organic
chemistry at Palermo. There he spent ten years, studying the aromatic
compounds and continuing to work on the amines, until in 1871 he was
appointed to the chair of chemistry at Rome university. Apart from his
work on organic chemistry, which includes also an investigation of
santonin, he rendered great service to the philosophy of chemistry when
in his memoir _Sunto di un corso di Filosofia chemica_ (1858) he
insisted on the distinction, till then imperfectly realized, between
molecular and atomic weights, and showed how the atomic weights of
elements contained in volatile compounds can be deduced from the
molecular weights of those compounds, and how the atomic weights of
elements of whose compounds the vapour densities are unknown can be
ascertained from a knowledge of their specific heats. For this
achievement, of fundamental importance for the atomic theory in
chemistry, he was awarded the Copley medal by the Royal Society in 1891.
Cannizzaro's scientific eminence in 1871 secured him admission to the
Italian senate, of which he was vice-president, and as a member of the
Council of Public Instruction and in other ways he rendered important
services to the cause of scientific education in Italy.

CANNOCK, a market town in the western parliamentary division of
Staffordshire, England, in the district known as Cannock Chase, 130 m.
N.W. from London by the London and North Western railway. Pop. of urban
district (1891) 20,613; (1901) 23,974. The church of St Luke is
Perpendicular, enlarged in modern times. The famous political preacher,
Henry Sacheverell, held the living early in the 18th century. Cannock
has tool, boiler, brick and tile works. Cannock Chase, a tract generally
exceeding 500 ft. in elevation, extends on an axis from north-west to
south-east over some 36,000 acres. It was a