of Chromium-compounds. 



315 



been thus satisfactorily disposed of, the next question relates to 

 the function of the 2 in the chlorochromic acid. Has this 2 



a two or a four 



saturating 



power ? The well-known oxidizing 



energy of those compounds, such as Brodie's organic peroxides, 

 which are admitted to contain (0 2 )", leads us to see in the extra- 

 ordinary energy of chlorochromic acid an argument that the 

 oxygen is (0 2 )''. 



Thus chlorochromic acid becomes 



which is the analogue of 



€r 



Gr 



CI 

 CI 



CI 

 CI 

 CI 

 CI. 



Carrying out the theory systematically, we should write the 

 chromates on the same type : thus 



(O 2 )" 



Cr KO' 



KG' 



is neutral chroma te of potash. 



The establishment of the rational formulas of chromium-com- 

 pounds is of course an important step towards the establish- 

 ment of the rational formulas of analogous compounds. It must 

 have weight in fixing the constitution of the aluminium- com- 

 pounds, the formulas of which have been recently (as it appears 

 to me with little probability) deduced from vapour-density deter- 

 minations of aluminium-ethyle and alumimum-methyle taken 

 at temperatures at which these bodies have undergone decom- 

 position. 



In place of the hypothesis of Messrs. Buckton and Odling, 

 that aluminium-methyle is not a true gas at 130° C. but becomes 

 a true gas at above 200° C, an hypothesis which appears to me 

 to be very unphilosophical, I would suggest that aluminium- 

 methyle, if it should not experience an ordinary decomposition 

 at about 200° C, may perhaps react upon the mercury of the 

 bath, or, more interesting still, resolve itself into 



2Al 2 Me 6 =3AlMe 4 + Al. 



Either of these suppositions would be compatible with all the 

 data which are as yet published. 



London Institution,, 

 March 17,1865. 



Y2 



