484 On Manganese Tetrachloride. 



solve in the water. The reason why the dioxide solution 

 becomes much more stable with lowering of temperature is 

 probably that the atoms of chlorine come the less often into 

 the positions necessary for them in order that they may unite 

 together to form molecules, although nearly as large a number 

 of them may exist in the solution unattached to MnCl 2 mole- 

 cules at the lower as at the higher temperature. 



Even if slightly less than fifty per cent, of the dioxide were 

 recovered on precipitation, this argument would still hold 

 good, and so even in this case no proof would be afforded of 

 the existence of the sesquichloride. 



It has thus been shown that neither of Pickering's argu- 

 ments can be held to prove that when manganese dioxide 

 dissolves in hydrochloric acid, manganese sesquichloride, and 

 not manganese tetrachloride, is formed ; and as it has been 

 shown in the former part of this paper that there is every 

 probability that in the solution of the dioxide it is only the 

 tetrachloride that is formed, we must consider that such is the 

 case until stronger arguments than these have been brought 

 forward to refute it. 



Summary. 



The chief conclusions arrived at in this paper are : — 



(1) That when any of the oxides of manganese Mn0 2 , 

 Mn 2 3 , and Mn 3 4 , are dissolved in hydrochloric acid, the only 

 higher chloride formed is manganese tetrachloride, the equa- 

 tions for these reactions being : — 



Mn0 2 +4HC1 = MnCl 4 +2H 2 0; 



Mn 2 3 + 6HC1 = MnC] 4 +MnCl 2 + 3H 2 0; 



Mn 3 4 +8HC1 = MnCl 4 + 2MnCJ 2 + 4H 2 0. 



(2) That this manganese tetrachloride solution is very 

 much more stable at —26° C. than at ordinary temperatures, 

 it being probable that at a still lower temperature it would 

 undergo no decomposition whatever. 



(3) That no evidence has yet been brought forward to 

 show that any other higher chloride of manganese than the 

 tetrachloride is capable of existence. 



The University Laboratory, Oxford. 



