On Manganese Tetrachloride. 469 



the passage of the disturbance into A B, which momentum is 



in the direction of I. 



In the passage of the disturbance across A the mean force 



I r 



acting upwards is T . — And the time for which it acts is ~. 

 x V 



Thus the momentum generated is 



T— — 



x'y' 



Again, we have for the momentum generated the expression 



m.YL 

 Thus we get 



T 



V 2 = — • 

 m 



LIX. On Manganese Tetrachloride. 

 By H. M. Vernon, Scholar of Merton College, Oxford*. 



w 



HEN manganese dioxide is treated with hydrochloric 

 acid it dissolves with formation of a dark-brown 

 coloured liquid. This liquid evolves chlorine slowly at 

 ordinary temperatures, and at higher temperatures evolution 

 takes place much more rapidly, the solution soon becoming 

 colourless and containing only manganous chloride and hydro- 

 chloric acid. Forchammer showed, in 1821, that when this 

 brown liquid is diluted with a large quantity of water, the 

 solution remains clear for a few seconds and then becomes 

 turbid, a mixture of oxides of manganese being precipitated. 

 He also showed that a similar precipitation of oxides takes 

 place when solutions of manganese sesqui oxide and manganoso- 

 manganic oxide, Mn 3 4 , in hydrochloric acid, were diluted 

 with water. He did not, however, attempt to arrive at the 

 constitution of the higher chloride of manganese which he 

 supposed to exist in these dark-brown solutions. 



W. W. Fisher (Chem. Soc. Journ. 1878, p. 409) endea- 

 voured to show that the dark-brown liquid contains man- 

 ganese tetrachloride. He did this by delivering from a 

 burette known volumes of the liquid (1) into a solution of 

 potassium iodide, (2) into a large volume of water or, pre- 

 ferably, dilute potassium-acetate solution. If the action of 

 hydrochloric acid upon manganese dioxide is considered to be 

 represented by the equation 



Mn0 2 + 4HC1 = MnCl 4 + 2H 2 O r 

 * Communicated by the Author. 



