158 



ESSAY X. 



pure common salt in 6 or 8 Ib. of water ; pour this solution, 

 still boiling, into a glass vessel, and immediately afterwards 

 mix with it the above-mentioned solution of quicksilver, 

 which must also be boiling, in small quantities at a time, 

 with constant agitation. When the precipitate has settled, 

 decant off the clear liquor and pour hot water again on the 

 precipitate, with which it is to be edulcorated till the water 

 standing upon it shall be entirely tasteless. Put the whole 

 obtained by these means together ; filter and dry it in a 

 mild heat. 1 



SECTION II. 



If we consider how mercurius dulcis is obtained in the 

 dry way, or by sublimation, it will not be difficult to account 

 for the method I have proposed. Mercurius corrosivus albus 

 is a middle salt, and consists, as is well known, of marine 

 acid, combined with calx of mercury. This salt can dissolve 

 a good deal of quicksilver in its metallic form. In order to 

 this, they must meet one another when separated into their 

 smallest particles, which happens when, by means of heat, 

 they are converted into vapour. The same thing takes 



silver ; but it is always better to take too much than too little, for 

 the more metallic substance the mercurial solution contains, the more 

 mercurius dulcis is obtained. 



1 The mercurial solution must be cautiously poured into that of the 

 common salt, that no mercury may follow. 2 oz. of salt would be 

 sufficient for the precipitation of all the quicksilver ; but when so small 

 a quantity is used, it may easily happen that some superabundant 

 corrosive sublimate may adhere to the precipitate, which water alone is 

 incapable of entirely separating ; this is doubtless the reason why it is 

 generally supposed that white precipitate is corrosive. I have found 

 that common salt, as well as sal ammoniac, is capable of dissolving a 

 considerable quantity of corrosive sublimate. It is on this account that 

 I take 4iy oz. of salt, in order completely to separate all the corrosive 

 sublimate. From the above-mentioned quantity of quicksilver, about 

 8i oz. of mp.rcurius dulcis are commonlv obtained. 



