[ 161 ] 



XXXIT. On the Ident'Uy of Silex and Oxygen. By 

 Mr. Hume, of Long- Acre, London. 



[Concluded from vol. xxx. p. 363.] 



J. HE solution of silex in water, by means peculiar to na- 

 tural agency, is not confined altogether to hot-springs, as 

 it has been frequently detected in other mineral waters; and 

 in no case can its presence be ascribed to an alkali acting as 

 a medium, because this is not always to be found, and, 

 when it is detected, it is combined with carbonic acid, which 

 destroys effectually the solvent power of the alkali over silex. 

 In three mineral springs, analysed bv M. Stucke, the whole 

 contained silex*; and in a sulphureous water, which was 

 examined by the Marquis df Bicze, a considerable portion of 

 the same inflexible and universal niaterial was extracted f . 



A great deal of the siliceous principle exists in the warm- 

 baths of Pozzello ; for, besides the 10 grains derived from 

 every 100 pounds of the water, there was likewise a pellicle, 

 which formed itself upon the surface of the bath ; and this, 

 when examined, consisted of silex, carbonate of lime, and 

 carbonate of magnesia %. 



From the experiments of M. Volta, we are informed, that 

 all the waters of Verona contain silex in the state of carbo- 

 nate of lime or chalk, and, agreeably to this philosopher's 

 opinion, this is held in solution by means of oxygen§. 

 Here, I think, we may perceive that graduation of silex 

 into lime, which I mentioned in a former paragraph, and 

 which forms another example of the prevalence of this con- 

 stant association in all native carbonates. In the same warm 

 baths of Pozzello, which I have just noticed, there is also a 

 quantity of carbonates; thus, each hundred grains of the 

 pellicle consisted of 86 grains of carbonate of lime, 1 1 grains 

 of the carbonate of magnesi^ and only three grains of silex ; 

 seemingly, as if these carbonates had derived their saturation 

 with the oxygenating principle, from that which had origi- 

 nally consisted of a mucii larger stock of silex. If this con- 



* Crell'i Journal, 1791. f Mfin. ile I'Acad. de Turin. 



J A/Ill. i/c Cliiiiiic, t'jiiic xii. § Ann. de Chimie, tome xii. p. I-IV. 



Vol.31. No. 1^3.-^//^. 180S. L version 



