SS 



Next follow the tables of the contents of six kinds of corundum, 

 viz. the sapphire, the ruby, and the corundum from the Carnatic, 

 from Malabar, from China, and from Ava. The proportions of the 

 first species are 5^ silica, 92 alumina, 1 iron, and 1|- loss. The pro- 

 portions of the other kinds do not differ very considerably from these. 



The matrices of these stones being more easily fused than the six 

 kinds above mentioned, the usual and well known mode of treatment 

 by potash was found sufficient to render them soluble in acids. Al- 

 though this mode be now very familiar to chemists, the author, how- 

 ever, in order to leave no cause for suspicion, describes the process 

 he used with the matrix of the corundum from the peninsula of India. 

 The results gave 42| silica, 37 alumina, 15 lime, 3 iron, and 2 loss, 

 with a trace of manganese. By similar treatment the various sub- 

 stances contained in this and some other matrices, viz. felspar, fibro- 

 lite, and three sorts of thallite, were analysed, and the results are 

 given in tables. It is remarkable that while all the other substances 

 yield in different proportions the same ingredients as the matrices 

 themselves, the fibrolite was found to consist only of silica and alu- 

 mina, the quantity of iron it contained being so small as hardly to 

 deserve notice. 



In the prosecution of this inquiry Mr. Chenevix observed, that if 

 a quantity of potash be for some time kept in fusion in a platina cru- 

 cible, the latter will be found to lose some grains of its weight. The 

 quantity of the metal thus lost he actually found in the potash ; and 

 hence he infers the affinity between these two substances, which af- 

 finity, it seems, is made use of by the Spaniards for detecting the 

 platina contained in the ingots of gold sent from their American 

 possessions. He also has occasion to show that potash which has 

 usually been denominated a fixed alkali is not so, strictly speaking, 

 since there is a degree of heat by which it may be totally volatilized. 



In a second part of the paper the author treats of the affinities 

 which the earths are supposed to exercise towards each other when 

 held in solution by acid or alkaline menstrua. There being a dif- 

 ference of opinion on this subject among some of the most eminent 

 chemists, Mr. Chenevix has repeated many of their experiments, 

 especially those of Guyton de Morveau. After descanting largely on 

 the probable causes of error in this eminent chemist, as well as in 

 Mr. Kirwan and others, he derives from his results the following 

 general conclusions. 



1st. That there exists an affinity between silica and alumina. 



2ndly. That there exists a very powerful affinity between alumina 

 and magnesia. 



3rdly. That alumina shows an affinity for lime. 



4thly. That Mr. Guyton was mistaken in every instance of affinity 

 between the earths, except in one which had been observed before 

 his experiments ; and that he has attributed to a cause which does 

 not exist, phenomena that must have resulted from the impurity of 

 his re- agents. 



And lastly, That neither the experiments of Mr. Guyton, nor an 



