1&2 ESSAYS AND OBSERVATIONS 



by violent agitation: then make them juft to- 

 boil over a brifk fire. 



Add now to the mixture three or four 

 times its quantity of hot water ; after a little 

 agitation, allow the magnejia to fettle to the 

 bottom, and decant off as much of the water 

 as poffible. Pour on the fame quantity of 

 cold water j and, after fettling, decant it oft 

 in the fame manner. Repeat this wadiing 

 with the cold water ten or twelve times : or 

 even oftner, if the magnefia be required per- 

 fectly pure for chemical experiments. 



When it is fufEciently wafhed, the water 

 may be flrained and fqueezed from it in a 

 h'nen cloth ; for very little of the 7nagnefia 

 pafTes thro'. 



The alkali in the mixture uniting with the 

 acid, feparates it from the magnefia ; which not 

 being of itfelf foluble in water, mufl confe- 

 quently appear immediately under a folid form. 

 But the powder which thus appears is not 

 intirely magnefia; part of it is the neutral fait, 

 formed from the union of the acid and alkali. 

 This neutral fait is found, upon examination, 

 to agree in all refpeds with vitriol ated tartar, 

 and requires a large quantity of hot water to 

 dilTolve it. As much of it is therefore dif- 



folved 



