j52 Coinpofifin of Alunnne and the new Earth in the Beryl. 



re-diflblving it In water, I added a few drops of fulphatc of pot-afli to the folutlon, and ob- 

 tained o£lahedral cryibls of alum. 



Now it is evident that the earth of beryl has more affinity with the nitric acid than alu- 

 mine has, and confequently that it is not the fame earth. If the earth of beryl be not alu- 

 mine, there is much greater reafon to decide, that it is not one of the other known earths ; 

 for it differs much more from them than from alumine. I therefore confider this earth as rt 

 vew fubftance, different from all thofe we are yet acquainted with. It is true, that it in 

 fome meafure refembles a'.umine, namely, in its foftnefs to the touch, its adhefion to the 

 tongue, its levity, its folubility in pot-afh, and its precipitation from its folutions by 

 ammoniac. But it differs from alumine in its other properties. Its combinations with 

 acids have a very faccharine tafle ; it has a flronger afEnity with thcfe foivenrs ; it does not 

 afford alum with the fulphuric acid and potafli ; it is totally foluble in carbonate of ammo- 

 niac -, and laflly, it is not, like alumine, precipitable from its folutions by the oxalate and 

 the tartrite of pot-afli. 



This earth being foluble in cauftic pot-afli, like alumine, we can no longer trufl: to this 

 (imple charafter to afcertain the prefence of the latter earth ; for it m*ay happen that the 

 eanh of beryl fliould be taken for alumine, or a mixture of both for one or the other of 

 thefe pure earths. It will therefore be necefiary, whenever an earth foluble in pot-afli is 

 found, to endeavour to convert it into alum by the known methods. If it do not afford 

 alum, it may be certainly concluded that it is not alumine. But it may poffibly afford 

 alum, and neverthelefs contain the earth of beryl j a mother water will then remain, in 

 ■which this laft earth will be fufpendcd. 



To feparatc the fmall quantity of alum, which likcwife remains in this mother water, 

 It will be proper to decompofe it by a folution of the carbonate of ammoniac added in ex- 

 eefs ; by .this means alum will be entirely precipitated, and the earth of beryl will remain 

 diffolved in the carbonate of ammoniac. This earth may afterwards be readily feparated 

 by boiling the folution for a certain time. The heat will drive off the carbonate of ammo- 

 niac, and the earth will fall down in the form of a powder. 

 • ' By comparing the refults of the analyfis of the beryl with thofe which Klaproth and my- 

 felf obtained from that of the emerald, we might conclude, that thefe two ftones are very 

 different from each other ; for I found that the emerald was compofed of 64 of filex, 29 

 alumine, 2 lime, between 3 and 4 of the oxide of chrome *, and i or 2 of water ; 

 whereas the beryl is compofed of 69 filex, 21 alumine, 8 of the peculiar earth, and ij of 

 the oxide of iron. 



But fince that time I have found that the emerald likewife contains this new earthy 

 whence it follows, that the emerald and the beryl are one and the fame fubftance, differing 

 only in their colouring matter. 



With regard to the proportion in which I have obtained this earth of the beryl, I do not 

 give it as ftriftly accurate ; for it is poffible that part may have been diffolved at the fame 

 time as the alumine by the pot-afh f . 



• This it the metallic acid difcovered in the red-lead of Siberia, of which a (hort account was given in our 

 Journal, II, 145. The memoir gt length, with additional infonnation, will appear in our next. N. 



f Since the above was written, I have afcertained, that there was in fact a certain quantity of the earth of 

 tcryl diffolved by the pot-afh with tlic alumine; and that inftead of i per cent, the beryl contains 16. 



1 have 



