Biography of Berzelius. 311 
portant researches, they did not pursue this subject further, and 
especially did not study with sufficient accuracy the phenomena 
which presented themselves when potassium was heated in fluorid 
of silicium. 
Berzelius, in the first instance, prepared the most important 
metallic fluorids ; then he went on to the remarkable compounds 
which hydrofluoric acid forms with electro-negative fluorids, 
especially fluorid of silicium, and fluorid of boron, besides fluorid 
of titanium and others. It was through him that we first ac- 
quired a correct conception of the composition of hydrofluosilicie 
acid and the fiuosilicates, as well as of the action of water 
upon fluorid of silicium. But the most productive part of this 
same results as the French chemists: namely, the brown non- 
metallic substance which they regarded as a complex compound 
of fluosilicid of potassium and of fluorid of potassium with silica. 
Berzelius found that it was impure silicium, which, when washed 
with water, could be obtained free from all fluorine compounds. 
It then contained only an admixture of silica, which could be ex- 
tracted by concentrated hydrofluoric acid, after having previously 
been slowly heated to redness. He moreover shewed that the 
silicium could be obtained in different states of density, and with 
different characters. 
This unexpected result induced him to undertake similar inves- 
tigations with fluorid of boron. We are indebted to him for a 
correct knowledge of the decomposition of fluorid of boron by 
Water, and of the composition of fluoborids, as well as an easy 
method of preparing boron, by treating fluoborid of potassium 
with potassium. He likewise discovered at this time the gaseous 
chlorid of boron, and corrected the views of the composition of 
boracic acid by his own experiments and those of Arfvedson. He 
Moreover prepared the compounds of fluorid of titanium with 
metallic fluorids, especially fluorid of potassium, from which bod 
he shewed how metallic titanium was to be obtained by means of 
potassium. This is the only method by which titanium can be 
obtained in a pure state; for the experiments of Wéohler have 
proved that the substance found in the slags of iron furnaces, and_ 
formerly called metallic titanium, contains nitrogen and cyanogen. 
compounds of fluorid of tantalum with metallic fluorids were 
So prepared, and he obtained metallic tantalum in the same way 
as titanium. He then reduced zirconium from the zirconio-fluorid 
oi 
