320 USGS OP QUICKSILVER, &C. 



nins; mercury again. He then inquired into the change which re. 

 peated distillation could produce ; after each pperation he found a 

 red acrid powder remaining in the retort ; and he observes, that 

 this powder was as copiously separated, after the mercury had 

 been above 500 times distilled, as at first ; and thence reasonably 

 concludes, that it ought rather to be attributed to a change of the 

 mercury itself, than to any impurity contained in it. This pow- 

 der, like the preceding, by a superior degree of heat became run. 

 ning mercury ; except about a seventy-second part, which, though 

 fixed in a strong fire, and verifiable with borax, could not sup- 

 port the action of lead, but vanished entirely, leaving no signs of 

 any metallic substance upon the cupel ; this shews the little pro- 

 bability of converting mercury into gold or silver by the action of 

 a violent fire. In the following year he presented a memoir to the 

 Royal Academy of Sciences, at Paris, upon the same subject. We 

 there learn, that mercury, kept in digestion for fifteen years, with 

 a constant heat of 100, was not fixed, nor any how changed, ex. 

 cept that a little black powder (which by simple grinding in a 

 mortar became running mercury) was found floating upon its sur- 

 face. Hence is inferred, the impossibility of mercury's being 

 changed in the bowels of the earth into any other metal, the heat 

 in mines scarcely ever amounting to 100. Though it might be 

 impossible to change mercury into a metal, yet the philosophers by 

 fire contended, that mercury, united to a particular kind of sul- 

 phur, entered into the composition of all metals, and might 

 by art be extracted from them ; lead was of all others thought the 

 most likely, and the experiment had been reported to succeed by 

 Van Helmont, and others ; but Boerhaave is positive, that nothing 

 can be expected from its combination with salts, and lead, or tin. 

 It was still thought by the alchemists, that mercury could never be 

 freed from its original impurity, but by being joined to some pure 

 body of the same nature with itself : this they thought gold and 

 silver to be. Boerhaave, in order fully to subvert their high pre- 

 tensions, gave in, to the Royal Society, another paper, in the latter 

 end of the year 1736, containing an account of the unchangeable- 

 ness both of mercury and gold, how often soever they were dis. 

 tilled together. He repeated the distillation of mercury from gold 

 above 850 times ; the mercury was not in any respect changed ; 

 its specific gravity was the same as at first^ nor had it lost the pro- 

 perty of being converted into a red powder by a due degree of 



