WITH THE MARINE ACID. 323 



ccedingly difficult and tedious. 2d, That, by 

 the method of Lemery, Icfs corrofivc fublimate 

 is procured than by the ordinary method, 3clly, 

 It is ncccfTary to employ the common white fait 

 which always contains fomc muriatic magncfia 

 and lime. If the experiment were made with 

 common fait freed from thole earthy falts, not 

 a particle of corrofivc fublimate would be pro- 

 duced ; as appears evidently from the attention 

 Baumc has paid to this queftion *, as well as 

 from the experiments ivmdt' by Lemery. The 

 latter, when he had dillblvcd in water, the mat- 

 ter remaining after his operation, had filtrated 

 it, and formed it into cryilals, obtained the 

 purcit common fait ; but which, when triturated 

 again with mercury, andcxpofcd to the fire af- 

 forded no corrofivc fublimute. In this cafe the 

 acid of the common fait was not expelled by 

 tire as, it would have been from the earthy fails. 

 Nor, indeed, docs the experiment fuccecd bet- 

 ter, if, .inftcad of fait, its acid only is taken ; as 

 it does not net upon mercury, unlcfs that metal 

 has been prcvioufly divided minutely by precipi- 

 tation or rciblvcd into vapours. Bdldes, before 

 the fubliming vdlcl is penetrated with a degree 

 of heat fuflkient to raife the mercury to a (tatc 

 of vapour, the acid of the fait has already alUimcd 

 that form, as it polll-llcs a greater proportion of 

 volatility. It is therefore required, that the acid 

 X 2 ihoiild 



* Dift. dc ChcmJc dc Macq^cr. 



