MERCURIC SALTS CHANGE INTO EACH OTHER. \gj 



some relatively minute and unknown quantity of mercurous chloride 

 becomes oxidised when it is boiled with water and hydrochloric acid 

 till all has dissolved. 



Closely connected with Guibourt's statement, there come in here 

 interesting observations of Mialhé (1840-3), an account of which I 

 take, with condensation, from Gmelin's Handbook. Agitated for an 

 hour at 100° in a well closed bottle with a, tenth of its weight of mer- 

 curous chloride, water takes up a thousandth part of the mercury as 

 mercuric chloride, but if air has access to the liquid, more mercuric 

 chloride is formed. In 2-1 hours, at 40-50°, in presence of hydro- 

 chloric acid, water takes up 7 / 1000 of the mercury as mercuric chloride, 

 when in a closed bottle ; but in the open air it takes up 23 /i oo' In & 

 closed vessel containing mercurous chloride with twice its weight of 

 ammonium chloride and twice its weight of sodium chloride, and 33 

 times its weight of water, one hundredth of mercurous chloride dis- 

 solves ii s mercuric chloride in the course of 24 hours at 50° ; while in 

 an open vessel 3.6 hundredths are dissolved. " Hence it appears that 

 " more than two-thirds of the mercuric chloride is prodused by the 

 " oxidising action of the air, and one-third by the decomposition of 

 " calomel." No such assertion as this, as to oxidation being the cause 

 of the observed phenomena, occurs in the Kraut- Jörgen sen edition. 

 The result of my experiments on this salt in this particular connection, 

 which are given in the next paragraph, were feeble, but my other 

 experiments upon it and those upon mercurous nitrate, already de- 

 scribed, make it clear enough that Mialhé in his experiments got more 

 mercuric chloride in an open vessel because then dissociation could 

 proceed, whereas the retention of the mercury in the closed vessel 

 stopped it. Confirmation of this statement will be found in the results 

 of my experiments at 150° to be presently described. It is true that 

 Mialhé ascertained that metallic mercury, unoxidisable as it is alone by 



