420 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



industrial chemists. This fact is the fouudiition of the methods of prepa- 

 ration of vermihon in the wet way, fii'st described by G. S. C. Kirclihoff 

 in 1799.' In 1829 C. Briinner' discovered the double soluble salt HgS, 

 K-S + 5H-0. Later, Dr. Reinhardt Weber' re-examined the properties and 

 formation of this salt, which he found could only exist in the presence of 

 free caustic alkali. In opposition to Professor Stein, Dr. Weber is extremely 

 positive in his statement that mercuric sulphide is entirely insoluble either 

 in the simple sulphides of sodium and potassium or in the sulphydrates of 

 these metals, excepting in the presence of free hydrates. In the light of 

 facts definitely ascertained since this chemist's investigation, so general a 

 statement does not seem to be borne out by his own observations; for he 

 says that if potassic hydrate be added to the sulphydrate the mixture dis- 

 solves mercuric sulphide with the greatest ease. Now, excepting when ex- 

 tremely dilute, a mixture of the two alkaline solutions produces potassic 

 protosulphide, IvS, and, unless more caustic potash was added than would 

 be sufficient to convert all the sulphydrate into the simple sulphide, Dr. 

 Weber's solution was not, as he evidently supposes, a mixture of hydrate 

 and sulphydrate, but of simple sulphide and sulphydrate. 



In 1864 Mr. C. T. Barfoed* investigated the behavior of mercuric 

 sulphide to sodium sulphides. He, like Dr. Weber, found the metallic 

 sulphide wholly insoluble in the sulph3'drate, but soluble in the simple sul- 

 phide, and in mixtures of the latter either with the sulphydrate or with the 

 hydrate. He insists that the necessary and sufficient condition for the sol- 

 ubility of mercuric sulphide is the presence of sodic protosulphide. 



The assertion is frequently made in chemical writings," in spite of the 

 results obtained by Weber and by Barfoed, that mercuric sulphide is solu- 

 ble in sodium sulphydrate; but, though Professor Stein and the other chem- 

 ists who have made this assertion may not have emplo3-ed fully satuiated 

 sulphydrate, as wnll appear later, none of them can have failed to carry the 

 saturation beyond 50 per cent , and none, therefore, can have dealt with 



' Allg. Jour, tier Cheniie, Scberer, vol. 2, p. 290. 



- Poggeiulorff, Anualen, vol. 15, \t. 593. 



^Ibiil., 4th series, vol. 7, l-.^jfi, p. 7C. 



'Jour. ]>r;ikt. Cliemie, vol. 9:!, 11(14, p. 'J:!0. 



'•For csainplc, Graliaiii-Otto. tilth edition, part:'., vol. -J, p. 1119. 



