[ «9* 3 



SECT. XIX. 



After the mineral bodies have been tried in thfc 

 fire by themfelves, they ought to be melted with 

 fluxes, to find out if they can" be diffblved or not, 

 and fome other phosnomefia attending this opera- 

 tion. To this purpofe three different kinds of 

 falts are ufed as &uxes, vh. Sal S'od$> Bor#\\ and 

 Sal fufible mkrccofmicur.i (Seel. xi). 



SECT. XX. 



The Sal Sodre is a mineral alcaii well known* 

 prepared from the herb Kali or Saltwort; this Jaft 

 is however not much ufed in thefe friiall expert 

 ments, its effects upon the charcoal rendering it, 

 for the mod part, unfit for it •, becaufe, as foon as 

 the flame begins to act upon it, it melts inffahfly, 

 and is almolt wholly attracted by the charcoal. 

 When this fait is employed to make any experi- 

 ment, but a very little quantity thereof is wanted 

 at once, viz. about the cubical contents of an 

 eighth part of an inch, more or left \ This is laid 

 upon the charcoal, and the flame blown on it with 

 the Blow-pipe •, but as this fait commonly is iri 

 form of a powder, it is neceffary to go ori very 

 foftly, that the fo'*ce of the flame may riot difperfe 

 the minute particles of the fait. As fopn as ic 

 begins to melt it runs along on the charcoal al- 

 mot as melted tallow, and when cold, it is a 

 glaffy matter of an opaque dull colour fpread on 

 the coal. The moment it is melted the matter 

 which is to be rried ought to be put into it, be- 

 caufe otherwife the greateft part of the fait will 

 be (baked into the charcoal, and too little of it 

 left for the intended purpofe •, the flame ought 



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