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THE OLD AND THE NEW CHEMISTRY. 
By M. M. PATTISON MUIR, F.R.S.E. 
T HERE have recently appeared in the Gomptes Rendus , and 
in the Archives des Sciences physiques et naturelles , a 
series of communications by Wurtz, Berthelot, and Marignae 
upon the merits of the two systems of chemical notation based 
respectively upon the use of equivalents, and upon that of 
atomic weights. 
The echoes of the old strife, once so fiercely waged by the 
opposing schools, have almost died away in this country ; is it 
not possible that the lessons which the history of the warfare is 
fitted to teach are also beginning to be forgotten by the 
chemists of to-day ? 
Let us briefly glance backward at the page of chemical history 
which tells of the conflict of the atomists and the upholders of 
an equivalent notation. 
Until the time of Black, Cavendish, Priestley, Lavoisier and 
his associates, chemistry can scarcely be called an exact science. 
Many experiments had been performed by the older chemists, 
and many facts had been amassed ; but their experiments were 
for the most part vague, and their facts inexact. 
The rise of quantitative chemistry necessitated the adoption 
of a quantitative notation. 
In 1777 Wenzel determined, with very considerable accuracy, 
the amounts of potash and of lime which were required to 
neutralize given quantities of sulphuric and of nitric acid. He 
found that 123 parts of lime and 222 parts of potash severally 
neutralized 240 parts of nitric acid and 18L5 parts of sulphuric 
acid. Hence arose the idea of equivalency. So far as their 
power of neutralizing sulphuric or nitric acid was concerned, 
123 parts of lime were equivalent to 222 parts of potash. 
Passing over a period of about fifty years — a period fraught 
with all-important issues in chemical science — we find the idea 
of equivalency coming into general favour among chemists. 
The researches of Lavoisier, of Cavendish, of Berzelius, and of 
others had introduced an accuracy into chemical experiment 
