Cambridge Philosophical Society, 227 



the above formula, unless the exceediugly improbable assumption be 

 adopted, that it contains two volumes of zincmetbyle vapour, united 

 with one volume of ether vapour, without condensation. On the 

 other hand, it accords closely with the speciiic gravity of the vapour 

 of a mixture of zincinethyle and ether in the above proportions. 



Without at present offering any decided opinion as to the nature 

 of this body, the author states that in repeated operations with large 

 quantities of materials he has entirely failed in obtaining ^wre zinc- 

 methyle by this method of proceeding. 



Similar repeated attempts to produce pure zincethyle frcm zinc 

 and iodide of methyle, without the intervention of ether, were also 

 unsuccessful, although this method generally succeeds in small glass 

 tubes. This anomaly in the results obtained from the same mate- 

 rials heated in a copper digester and in glass tubes, is doubtless due 

 to the difference of the conditions in the two cases. In a glass tube 

 half immersed in a heated oil bath, a constant distillation of the 

 internal liquid is going on, the liquid condensed in the upper por- 

 tion of the tube flowing over an extensive surface of zinc in its 

 descent ; whilst, in a digester of thick copper, the different parts 

 of the vessel, owing to the high conductivity of the metal, are main- 

 tained at so uniform a temperature as to prevent any such circulation 

 of the liquid from taking place. 



The body just described being regarded as a mere mixture of zinc- 

 metbyle and ether, incapable of being separated on account of the 

 close proximity of their boiling-points, a more successful result was 

 anticipated by mixing the iodide of methyle with methylic ether 

 instead of vinic ether. As methylic ether boils at — 21°C., it was 

 thought that no such difficulty of separation could arise ; the bodies 

 employed would then, in fact, be exactly homologous with those so 

 successfully used in the preparation of pure zincethyle on the large 

 scale. It vvas found, however, that although a large quantity of 

 zincmethyle was produced, ^et it was impossible to obtain it free from 

 methylic ether. A large portion of the product boiled at 43°, a 

 small residuum only distilling between this temperature and 48°; 

 both portions yielded, on analysis, results approaching the formula 



Kc:!J:}-0-c:h:}o.. 



This result is, therefore, homologous with that obtained by the de- 

 composition of iodide of methyle mixed with vinic ether. 



In conclusion, the author states, that after an expenditure of many 

 pounds of iodide of methyle, he has been unable to obtain even the 

 smallest quantity of pure zincmethyle by the use of a copper digester, 

 although a mucli larger product of the ethereal solution is obtained 

 than in the corresponding preparation of zincethyle. 



CAMBRIDGE PHILOSOPHICAL SOCIETY. 

 [Continued from vol. xvi. p. 318.] 

 April 26, 18.5S. — Professor Challis made a communication *' On 

 the Annular Eclipse of the Sun, March 1.5, 1858." 



The Ma^ter of Trinity read a i)aper " On Barrow, and his Acade- 

 mical Times." 



Q2 



