x 293 j 



SECT. xxn. ' 



The quantity of thefe tv/o falts required for an 

 •experiment is almoil the fame as the Sal Sod& 

 (Seel:. xx.)' 3 but as thefe falts are crifhallifed, and 

 ■confequently include a great deal of water, parti- 

 cularly the borax, their bulk is confiderably re- 

 duced when melted, and therefore a little more of 

 thefe may be taken than the before- mentioned 

 quantity. 



SEC T. XXIII. 



Both thefe falts, (Seel, xxi.) when expofed to 

 the flame of the Blow pipe, bubble very much 

 -and foam before they melt to a clear glafs, but 

 more (o the borax, which for the mod part de- 

 pends on the v/ater they contain : And as this 

 would hinder the affayer to make due obfervations 

 on the phcenomena of the experiment, the fait 

 which is to be ufed, muft firft be brought to a clear 

 .gla!>,, 'Sect, xxi.) before it can ferve as a flux ; 

 it muft therefore be kept in the fire until it is 

 become fo tranfparent that the cracks in the char- 

 coal may be feen through it. This done, whatfo- 

 ever is to be tried, is put to it, -and the fire 

 ■continued. 



^ECT, XXIV. 



Here It is to be obferved, that for the aflays 

 -made with any of thefe tv/o fluxes (Se6L xxii ) 

 on mineral bodies, no larger pieces of thefe 

 muft be taken, than that altogether they may 

 keep a globular form upon the charcoal ; becaufe 

 then it may be better diftinguifhed in what man- 

 gier the flux acts upon the matter during the ex* 



U 3 perimenjc; 



