!55 



experime.ufc* 

 with zinc aiid 





fsi bkiidt;. 



, D.'irW^ MINERAL. 



A similat efl^ect was lately produced on a platina spoon, ^ 

 which some c^alena was exposed to the blow-pipe. 



x\s the quantity of the nnneral imder examination detached 

 at different times did Bot in the whole amount to above 300 

 grains, of which the greater part had been wasted in the fore- 

 going" experiments, an analysis of so small a quantity would not 

 hme been publiBhed. but thai wnfortiinately another specimen 

 «ould not be procuxed of the same mineral, ; m order how- 

 ever, to render as satisfcictory as possible the results of aji 

 ?:nalysis conducted on so smali a scale, a few comparative 

 experiments were made on zinc, and on blende, of which last 

 sxibstaiice th?s miaeral evidently aj>pearcd, to be a variety; 

 anaccoimt of these experiments has been added, as not altoge- 

 *]ier Mnintererjting in themselves., but principally in confirmation 

 of the analysis : the reagents employed in these, were prei- 

 paj-ed by Messrs. Allen and Howard ; and the precipitates were 

 washed, separated, and drted^ without the iise of filters, except 

 in the case ef the precipitates by prus^iate of potash, 



grs. 

 Zinc, grs. 5, dissolved in nitric acid (1.47), precipita- 

 ted by potash, and di'ied at SOO Fahr. weighed ♦ • • • ^.40. 



Zine, grs, 20, dissolved, &r. • . 24.50, 



Zinc, grs. jtOO, dissolved, &.c. ................... 125. 



Sp. gr. of these precipitates Avas about 4.3. 

 According to Mv. Proust's analysis,, (vide Thompson, 2d. 

 edition, vol. l. p. 199,) the two first of the three preceding pre- 

 cipitates ought to have weighed respectively 6.25, and 25 : the 

 weight of the last is correct, 



grs. 

 Lamipatcd brown blende (sp. gr. 4.06'78), ^,'Ci. ICO, dis- 

 solved in nitric acid, precipitated by poiash, and dried 



at 300 Fahr. weighed t 75, 



Sp. gr. of the precipitate 4.54. 

 Zinc, grs. 5, dissolved in nitric oxid, precipitated by 



prussiate of potash, and dried at 300 Fahr. weighed 16.50. 



Zinc, grs. 20, dissolved, &c. • • . • • 65. 



Zinc, grs. 100, dissolved, &c. 330. 



'J'hc weights of the three last precipitates would bear equal 

 proportions to the respective weights of the zinc taken, if the 

 two lirst, instead of 16.50 and 65, were 16 and 6i\ 



As 



