311 



Another experiment was more successful, and gave the number 

 9 '97 for the vapour-density. 



The equivalent weight of mercuric ethyl is 129, which, being 



129 

 divided by the former figures, gives ^ 1 2 9 4 . If the constituents 



of this radical be condensed into two volumes of vapour, the more 

 accurate number 14 '86 should have been obtained. 



The theoretical density of mercuric ethyl, thus calculated, is equal 



129 

 101^=8-68*. 



This portion of the subject would be incomplete unless a few 

 words were added on the behaviour of zinc-ethyl towards mercurous 

 chloride. 



It has been mentioned, that all attempts to reduce iodide of mer- 

 curous methyl to the form of a radical containing one equivalent of 

 methyl and two equivalents of mercury have hitherto failed. 



Reasoning a priori, we should not expect to find a departure in 

 the present case, neither does such appear. Mercurous chloride 

 reacts with vigour on zinc-ethyl, but metallic mercury is formed 

 simultaneously with chloride of zinc and mercuric ethyl. 



The decompositions of mercurous and mercuric chlorides or 

 iodides, are thus shown : 



C 4 H 5 Zn + Hg 2 Cl=C 4 H 5 Hg+Zn 



and 



C 4 H 5 Zn+HgCl=C 4 H 5 Hg + ZnCL 



Having succeeded, by these simple means, in effecting a replacement 

 in zinc- ethyl through the ordinary metallic chlorides, there remained 

 yet one point untouched, viz. the behaviour of various organo- 

 metallic salts, under similar treatment. 

 First in order was tried 



* Here it is fitting to mention an error that has crept into the calculation of the 

 vapour-density of mercuric methyl as it appears printed in the ' Proceedings of the 

 Royal Society.' A false figure in the denominator of one of the fractions, causes 

 the experimental density to appear as 14 '8 6, whereas the true experimental density 

 observed was 8'29. The theoretical density of mercuric methyl calculated for two 



volumes, equals j^: 4 - 6 = 7'95. 



