186 S. HADA; HOW MERCUROUS AND 



mercurous chloride is rendered grey by boiling water, or by long 

 boiling with water, and that it imparts mercury and chlorine to the 

 water. Then, as to the greying, that is attributed to the formation of 

 metallic mercury, or hypomercurous chloride, or oxy mercurous 

 chloride ; while, as to the mercury going into solution, that is as 

 mercuric chloride, or mercuric oxychloride, or both mercurous and 

 mercuric chloride. In so far as these results, mostly obtained in con- 

 nection with pharmacological studies, differ from those of Guibourt 

 and Simon, and those here described, they may be attributed to the 

 action of impurities derived from the exceedingly large proportions of 

 water used, probably not always carefully distilled, and derived also 

 from vessels of inferior glass and porcelain, or to the action of light, or 

 to the heating having been carried out in long-necked flasks which 

 allowed some of the volatilising mercury to condense and run down 

 into the water. 



The decomposition of mercurous chloride into mercuric chloride in 

 presence of hot hydrochloric acid solution has long been well known ; it 

 was described by Proust and by Boullay early in the century. Petten- 

 kofer, Pfaff, Hennel are early authorities for the also well known 

 decomposition of mercurous chloride in presence of warm solutions of 

 ammonium, sodium, and potassium chlorides. Of special interest are 

 the grounds of belief that mercurous chloride and hydrochloric acid 

 become mercuric chloride by the action of the air. Guibourt stated 

 that all the mercurous chloride becomes mercuric chloride when it is 

 boiled with water containing hydrochloric acid, and Fresenius 

 (Quantitative Analysis) adopts this statement and gives an equation 

 expressing aerial oxidation. As a fact, there is no evidence whatever, 

 yet discovered, that any oxidation at that temperature takes place, 

 while it is certain that dissociation is fully competent to account for 

 all the facts observed. Positively must it be denied that more than 



