504 SPECIAL METHODS OF DISCOVERY. 



in the sea-water of the Pacific, the copper having dis- 

 solved and the silver be^ng precipitated upon it by electro- 

 chemical action. A peculiar substance ' the red-lead ore 

 of Siberia had early drawn the attention of chemists on 

 account of its beauty ; and various atempts had been 

 made to analyse it. Among others, Vauquelin tried his 

 skill upon it in 1789, in concert with M. Macquart, who 

 had brought specimens of it from Siberia; but at that 

 time he did not succeed in determining the nature of the 

 acid with which the oxide of lead was combined in it. 

 He examined it again in 1797, and succeeded in sepa- 

 rating an acid to which, from the beautifully coloured 

 salts which it forms, he gave the name of chromic. He 

 determined the properties of this acid, and showed that its 

 basis was a new metal, to which he gave the name of 

 chromium. He succeeded in obtaining this metal in a 

 separate state, and showed that its protoxide is an exceed- 

 ingly beautiful green powder. This discovery has been of 

 very great importance to different branches of manufacture 

 in this country.' Also, ' Vauquelin was requested by Haiiy 

 to analyse the beryl, a beautiful light-green mineral, crys- 

 tallised in six-sided prisms, which occurs not unfrequently 

 in granite rocks, especially in Siberia. He found it to 

 consist of silica, united to alumina, and to another earthy 

 body very like alumina in many of its properties but 

 .differing in others. To this new earth he gave the name 

 of glucina^ on account of the sweet taste of its salts.' 

 ' This discovery of glucina confers honour on Vauquelin, 

 as it shows the care with which his analyses must have 

 been conducted. A careless experimenter might easily 

 have confounded glucina with alumina? l 



h. By examining rare substances. As every new 



1 Thomson, History of Chemistry, vol. ii. p. 214. 



