222 Analysis of several Minerals. 



and sulphurous acid. The cobalt was next separated by the 

 hydrosulphuret of ammonia. The proportion, as drawn from 

 the mean of three nearly corresponding analyses, is, 



Lead 70-98 



Cobalt .... 0-83 



Selenium . . . 28-11 

 99-92 

 " With respect to the atomic constitution of this ore, Prof. 

 Stromeyer remarks, that ' its constituents are combined pre- 

 cisely in the proportion of their equivalents, and the quantity 

 of the selenium corresponds not only to the lead, but also 

 to the cobalt ; and that, therefore, both metals are to be re- 

 garded as in combination with selenium. The seleniate of 

 lead, too, agrees with the sulphuret of that metal in this re- 

 spect, — that, when both its constituents are oxidized, the sele- 

 nic acid and oxide of lead are in the precise proportion to 

 form a neutral seleniate of lead, just as the oxidation of galena 

 gives rise to a neutral sulphate of lead. The discovery of such 

 a compound is therefore to be anticipated whenever a native 

 seleniuret of lead exists.' — I take this opportunity to mention 

 that the native sulphuret of selenium which Professor Stro- 

 meyer detected among the volcanic products of the Lipari 

 Isles (of which I comm.unicated a short notice some months 

 since), was found among a mixed sublimed mass of muriate of 

 ammonia and sulphur. It was disposed in layers, and, from 

 its brownish-yellow colour, gives rise to the supposition that 

 the muriate of ammonia at such parts contained iron. A su- 

 perficial examination proved, however, that no iron was pre- 

 sent; and this observation led to the detection of the selenium. 

 In a letter which I have just received from Professor Stro- 

 meyer, he informs me that another ore has been found in the 

 Hartz, containing the seleniurets of lead, copper, silver, and 

 mercury, with the examination of which he is at present oc- 

 cupied." — Letter from Dr. Turner in the Ediii. Phil. Journ. 



ANALYSES OF SEVERAL MINERALS : BY PROF. GMELIN. 



" Since my last to you I have been much occupied with 

 analyses, and shall give you some of the results obtained. 



" I have discovered a beautiful mica in large laminae to be 

 a crystallized Lepidolite — that is to say, to contain lithion. It 



is composed of Silica 52-254 



Alumina 28-345 



Ox. of manganese . 3-602 



Potash 6-903 



Lithion 4*792 



Fluoric acid .... 3-609 



99-505 " This 



