568 EEPOBT— 1881. 



insoluble in all the ordinary solvents, hot methylene iodide heing the only liquii 

 capable of dissolving it. 



It melts somewhere about 230° C, with partial decomposition. Bj^ acting upon 

 it with iodine, we get, as the only products, mercuric iodide and methylene iodide :. 



I HgCHjHgl + 21^ = 2HgI, + CH J„. 



Analytical results are shown below : — 



The same compound can with equal ease be obtained from mono-mercury 

 compound (CH.^Hglj), by simply mixing it with some mercui-y, mercuric iodide, 

 and ether, and exposing the mixture to the action of hght, with frequent shaking, 

 as before. 



By heating di-mercury methylene iodide with a dilute solution of hydric chloride 

 we get mercuiic iodomethide : — 



I HgCH,HgI + HOI = I HgCHj + Hgl. 



The insoluble compound, which was in the previous paper supposed to be 

 CHjHg.jI.j, has been re-examined with care, and is found to yield iodoform by the 

 action of iodine, and not methylene iodide. The numerical result of analysis 

 remains, however, almost the same. It is, therefore, in all probability, a compound 

 of iodoform with mercury, having the formula Oil Hgslj, and containing a trivalent 

 radical. This compound is related to iodoform, in the same way as mercm-ic iodo- 

 methide is to methyl-iodide, or dimercury-methylene-iodide to methylene-iodide. 

 We may, therefore, be now supposed to possess tlie following series of organo- 

 mercury compoimds : — 



CHgCHgl), 



CHjCHgl),, and CH^Hgl^, 



CH(HgI)3. 



In conclusion, I wish to record my best thanks to Professor WUhamson for his 

 able counsel and kind assistance, and to Mi-. E. E. Berry for some of the prepara- 

 tions and analyses. 



The President delivered the following Address : — 



The Growth of the Atomic Theory. 



It has been thought desirable that, on the occasion of this half-centenary celebration 

 of the foundation of our great Association, some notice should be presented to 

 the members of what has been doing in the respective branches of science during 

 the period of our activity ; and I have, accordingly, traced out for your considera- 

 tion a very imperfect sketch of the theories which guided chemical inquiry at the 

 beginning of that period, and of the leading changes which have been wrought in 

 them by fifty years' work. 



There is, perhaps, hardly any branch of science which during the last fifty 

 years has made such great and steady progress as Chemistry. Let anyone com- 

 pare recent dictionaries of the science (including the bulky supplements, which con- 

 tain a record of the chief discoveries made while the body of the work was being 



