286 PROGRESS IN CHEMISTRY. 



pole, and passing a current throuo-h a strong solution of the chloride 

 of calcium, strontium, or 1)arium, Davy succeeded in procuring mix- 

 tures with mercury or ""amalgams" of their metals, to which he gave 

 the names calcium, strontium, and barium. Distillation removed 

 most of the mercury, and the metal was left behind in a state of com- 

 parative purity. The alkali metals, potassium and sodium, were 

 found to attack glass, liberating the "basis of the silex," to which the 

 name silicon has since been given. 



Thus nearl}^ the last of the "earths" had been decomposed. It was 

 proved that not merely were the "calces" of iron, copper, lead, and 

 other well-known metals compounds of the respective metals with 

 oxygen, but Davy showed that lime and its allies, strontia and baryta, 

 and even silica or flint, were to be regarded as oxides of elements of 

 metallic appearance. To complete our review of this part of the sub- 

 ject, suffice it to say that aluminum, a metal now produced on an indus- 

 trial scale, was prepared for the first time in 1827 by Wohler, profes- 

 sor of chemistry at Gottingen, by the action of potassium on its 

 cliloride, and alumina, the earthy basis of clay, was shown to be the 

 oxide of the metal aluminum. Indeed, the preparation of this metal 

 in quantity in now carried out at Schatfhausen-on-the-Rhine and at the 

 Falls of Foyers in Scotland by electrolysis of the oxide dissolved in 

 melted cryolite, a mineral consisting of the fluorides of sodium and 

 aluminum, by a method difl'ering only in scale from that by means of 

 which Davy isolated sodium and potassium in 1806. 



Davy's important work. 



To Davy, too, belongs the merit of having dethroned oxygen from 

 its central position among the elements. Lavoisier gave to this im- 

 portant gas the name "oxygen," because he imagined it to be the 

 constituent of all acids. He renamed the common compounds of 

 oxygen in such a manner that the term oxygen was not even repre- 

 sented in the name — only inferred. Thus a "nitrate" is a compound 

 of an oxide of nitrogen and an oxide of a metal; a "sulphate," of the 

 oxide of a metal with one of the oxides of sulphur, and so on. Dav}^, 

 by discovering the elementary nature of chlorine, showed first that it 

 is not an oxide of hydrochloric acid (or muriatic acid, as it was then 

 called); and, second, that the latter acid is a compound of the element 

 chlorine with hydrogen. This he did by passing chlorine over white- 

 hot carbon — a substance eminenth" suited to deprive oxy-compounds 

 of their oxygen — and proving that no oxide of carbon is thereby pro- 

 duced; by acting on certain chlorides, such as those of tin or phos- 

 phorus with ammonia, and showing that no oxide of tin or phosphorus 

 is formed; and, lastly, by decomposing "muriatic acid gas" (gaseous 

 hydrogen chloride) with sodium and showing that the only product 

 besides conunon salt is hydrogen. Instead, therefore, of the former 



