In the same year Berzelius discovered selenium in a deposit from sulphuric acid chambers, his masterly investigation including a study of the hydride, oxides and other compounds.
In his researches, Roscoe showed that the atomic weight of the metal as determined by Berzelius and the formulae given to the oxides were incorrect, and pointed out that the element falls into its natural place in group V of the periodic classification along with phosphorus and arsenic, and not in the chromium group where it had originally been placed.
Still, till the last Berzelius remained faithful to his original theory; experiment, which he had hitherto held to be the only sure method of research, he discarded, and in its place he substituted pure speculation, which greatly injured the radical theory.
The discovery of boron by Gay Lussac and Davy in 1809 led Berzelius to investigate silica (silex).
The hydrosulphide, KHS, was obtained by Gay-Lussac on heating the metal in sulphuretted hydrogen, and by Berzelius on acting with sulphuretted hydrogen on potassium carbonate at a dull red heat.
The results of Berzelius were greatly extended by Hermann Kopp, who recognized that carbon, boron and silicon were exceptions to the law.
The rapidity of the method, and the accurate results which it gave in the hands of a practised experimenter, led to its systematization by Jens Jakob Berzelius and Johann Friedrich Ludwig Hausmann, and in more recent times by K.
The preparation of the pure metal was successfully effected by Werner von Bolton in 1905, who fused the compressed product obtained in the Berzelius process in the electric furnace, air being excluded.
While successfully investigating the solid elements and their compounds gravimetrically, Berzelius was guilty of several inconsistencies in his views on gases.
Since the time of Berzelius many experimenters have entered the lists, and introduced developments which we have not space to mention.