ce, ee ee ee ee ee eae 
S. B. Christy—Genesis of Cinnabar Deposits. 457 
Tt seems much more probable, however, that the salt of mer- 
cury usually regarded as the most insoluble is the one in which 
we are directly interested, i. e. the mercuric sulphide. This 
salt, while insoluble in almost every thing else, is well known to 
be soluble in solutions of the alkaline sulphides containing free 
alkali: This fact is recognized both by Rose and Fresenius, but 
I have been unable to find any exact statements as to the de- 
gree of solubility. Prof. V. Stein, in Dingler’s Polytecbnisches 
Journal, vol. cxxxviii, p. 890, states: ‘I found that sulphydrate 
of sodium as well as potassium dissolved cinnabar even in the 
cold with the same ease as water dissolves sugar.” is state- 
ment is, to say the least, a great exaggeration. He also states 
that the polysulphides of thé alkalies failed to dissolve any 
noticeable trace of the sulphide of mercury. Fresenius* finds 
that yellow sulphides of ammonium dissolve traces of sulphide, 
of mercury, particularly in the cold. Barfoedt+ states that while 
sulphides of sodium and _ potassium dissolve mercuric sulphide 
sulphydrates of the alkalies, as well as sulphydrates to which 
sulphur has been added, fail to do so. 
On the other hand, Dr. R. Webert states that he found that 
sulpbide of potash dissolves the mercuric sulphide only in the 
presence of free potash or soda. Moreover, that the addition 
of carbonic acid, sulphydric acid, or flowers of sulphur, precipi- 
tates the mercury from such a solution completely. ; 
Again it is well known that the polysulphides of the alkalies 
change the black variety into cinnabar, which could hardly 
the case unless partial solution had taken place. Also, that 
when mercuric sulphide is slowly deposited from such solu- 
tions cinnabar results, but when rapidly deposited as by dilu- 
tion, ete, the black or amorphous modification ; finally, that 
cinnabar volatilizes out of contact with the air at a little below 
red heat, depositing cinnabar when slowly cooled, and the 
amorphous variety when rapidly cooled. : 
Such in brief is at present the not altogether satisfactory state 
of knowledge on this subject. 
Tarrp.—ExPERIMENTS UPON THE SoLuBILITy oF Mercurio Sut- 
PHIDE IN SOLUTIONS OF THE AL SULPHIDES AT HIGH 
TEMPERATURES AND PRESSURES. 
The t difficulty of accounting for the deposits of cinna- 
bar in oo wet wie ine always been the difficulty of finding 
any natural solvent for this substance. The experiments 
of Weber, cited above, show that as soon as the free alkali is 
neutralized either by carbonic or sulphydric acid the mercuric 
sulphide is precipitated completely from its solution in the alka- 
* Zei ift fi lytische Chemie, vol. iii, p. 140. 
Jooasi me aakeete Chex, vol. ay ty 244, 
{ Poggendorff's Ann. d. Phys. u. Chem., vol. xcvii, p. 76. 
