72 Hofmann and Modern Chemistry. [Jan., 
Nicholson, Maule, Simpson, Medlock, and others were pupils of the 
College. While Dr. Hofmann has been earnestly engaged in work- 
ing out the theory of this imteresting subject, he has not forgotten 
its practical application. The beautiful red colouring matter known 
as Magenta was first observed and described by him, although he 
never produced it on a commercial scale. Again, the splendid 
violet, so much in vogue at present, is a discovery of Dr. Hofmann’s, 
who produced it by the action of iodide of ethyl upon Magenta. 
It is a curious coincidence that the same agent which contributed so 
much, as will presently be seen, to his scientific successes, should 
also assist him im a brilliant industrial achievement. 
We must now sketch, although we can do so but briefly, the 
progress of scientific inquiry in Dr. Hofmann’s hands. 
By continuing his researches on Aniline and its derivatives, he 
worked step by step to a clearer conception of the relation in which 
these substances stand to ammonia. He proved the volatile bases to 
be compound ammonias, derived from ordinary ammonia gas by the 
substitution of compound atoms consisting of carbon and hydrogen, 
for either one, two, or three of the hydrogen atoms in ammonia, 
and he gave a method as general as simple for the artificial con- 
struction of an endless variety of these substances.* 
These researches have exercised a powerful influence upon the 
progress of Chemistry both practical and philosophical. Iodide of 
ethyl, in general the iodides of the alcohol radicals, with the aid of 
which the new reactions were accomplished, appear in these re- 
searches for the first time as agents of the substitution of compound 
hydrocarbon atoms for hydrogen, and substances which had been 
seen by few chemists at that time, became at once some of the most 
frequently employed agents of research. Ever since the publication 
of Dr. Hofmann’s Memoirs, these agents have played a most im- 
portant part in all researches in Organic Chemistry, by which the 
most interesting theoretical questions have been elucidated, and 
these agents are now manufactured upon a colossal scale for indus- 
trial purposes. 
Nor was the influence of this investigation upon the general 
progress of Chemistry less marked in Dr. Hofmann’s researches on 
Ammonia, in which he exhibited this substance as the source of an 
unlimited number of derivatives similar in construction but modified 
* This beautiful series of researches should be studied by the aid of Dr. Hof- 
mann’s papers, published in the following Journals :— 
‘ Liebig’s Annalen,’ vol. liii., p. 1. 
‘Researches on the Volatile Bases,’ ‘Quarterly Journal of the Chemical 
Society, vol. i, pp. 159-269 ; vol. ii., pp. 36, 104, 300. 
‘Researches regarding the Molecular Construction of the Volatile Organic 
Bases,’ ‘ Phil. Trans.,’ vol. exli. (1850), p. 93. 
‘Researches into the Molecular Constitution of Organic Bases’ (this paper is 
devoted to such as are not volatile, and continued in papers subsequently pub- 
jished), ‘ Phil. Trans.,’ vol exli. (1851), p. 372. 
