87 



fragments of quartz, felspar, calcareous spar, a brownish- yellow mica, 

 and particles of attractable oxide of iron. 



The paper closes with some account of corundum, which, contrary 

 to the received opinion, that this stone was only found in the East 

 Indies, has been thought to exist in other parts of the world. The 

 author dwells mostly upon the appearances of a stone he himself dis- 

 covered in the mountainous parts of the Forez in France, and which 

 the Abbe Hauy considers only as a species of felspar. The Count al- 

 leges his reasons for classing it with the perfect blue corundum, 

 known by the name of Sapphire. As to various stones found in 

 Germany, in the Isle of Tirree on the western coast of Scotland, on 

 Chesnut-hill near Philadelphia, and elsewhere, which have by some 

 been considered as corundum, the author cautions us against acqui- 

 escing in those assertions till more conclusive arguments shall appear 

 in their favour. 



Analysis of Corundum, and of some of the Substances which accompany 

 it ; with Observations on the Affinities which the Earths have been 

 supposed to have for each other, in the humid Way. By Richard 

 Chenevix, Esq. F.R.S. and M.R.I.A. Read May 20, 1802. [Phil 

 Trans. 1802,;?. 327.] 



After a detail of several unsuccessful attempts to analyse this stone, 

 which on account of its great hardness is both difficult to pulverize 

 and to be reduced by saline agents, we find an ample description of 

 the process, which was attended with the desired success. A piece 

 of corundum, weighing 100 grains, was made several times red hot, 

 and plunged into cold water ; it was then pounded, first in a steel, 

 and next in an agate mortar, and thus reduced into an impalpable 

 powder. This powder was by means of dilute muriatic acid cleared 

 from the ferruginous particles which adhered to it from the steel 

 mortar. It was then put into a platina crucible with 200 grains of 

 sub-borate of soda, and the mixture was exposed for an hour or two to 

 a violent heat : the glass produced by this fusion was in about twelve 

 hours dissolved, by boiling it in a proper quantity of muriatic acid. 



The silica might now have been separated by evaporating the 

 whole to dryness, but it was thought preferable to get rid of all the 

 salts contained in the liquor by a precipitation effected by means of 

 an alkaline carbonate. The precipitate thus obtained was then re- 

 dissolved in muriatic acid, and the silica was hence cleared by eva- 

 poration. The remaining liquor was afterwards boiled with potash, 

 by which means the alumina was precipitated. It was then redis- 

 solved by the excess of potash, from which the earth was finally ob- 

 tained by muriate of ammonia. A small proportion of iron was se- 

 parated by muriatic acid. Both these earths being now washed and 

 dried, were ignited, and thus the exact weight of each was accurately 

 ascertained. The author paid particular attention to the silica pro- 

 duced in this process ; as Mr. Klaproth, who had formerly analysed 

 this stone, declares that he never found any of this ingredient. 



