206 Mr. J. Aitken on Dew. 



detached from the molecule, and also the residue of the acid, 

 but whilst with the sulphur compounds these two simply com- 

 bine (forming a compound ether), and leave a hydrocarbon 

 sulphide, in the case of the phosphonium salt the acid residue 

 is reduced by the tertiary phosphine, and the group thus left 

 combines with the hydrocarbon radical, forming a ketone. 

 Thus :— 



|Bt 

 jOOCR 



Et 2 S <Jrw, -o = Et 2 S + Et OOC R. 



Et3P <8oC R = Et 3 P0 + Et 0C *L 



A result of this kind is in perfect harmony with the views 

 already expressed by one of the authors* regarding the analo- 

 gies and differences existing between phosphorus and sulphur 

 and their compounds. 



As regards the action of heat on the hydracid salts of tetr- 

 ethylphosphonium, the chloride and cyanide alone afforded in- 

 teresting results. In the case of the cyanide these, however, 

 were complicated by the presence of water, which attacked the 

 compound and converted it into hydrocyanic acid, phosphine 

 oxide, and ethane. A small quantity of it, however, appeared 

 to behave like a sulphur compound, as it was apparently con- 

 verted into cyanide of ethyl and triethylphosphine. The 

 action of heat on the chloride seems to be anomalous, and 

 as it is the only method by which the tertiary phosphine can 

 be obtained in any quantity from a phosphonium salt, the 

 decomposition of phosphonium chlorides containing various 

 hydrocarbon radicals has been the subject of a separate re- 

 search, the results of which one of the authors hopes soon to 

 be able to publish. 



XXIII. On Dew. By John Aitken. 

 To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



HAVE read the " Remarks on a new Theory of Dew," 

 by Mr. Charles Tomlinson, F.R.S., in your Journal for 

 June ; I have also read the paper there referred to, and written 

 by the same author in the 'Edinburgh New Philosophical 

 Journal,' " On the Claim of Dr. Wells to be regarded as the 

 Author of the ' Theory of Dew.' " In certain respects and up to 

 a certain point, these two papers bear a strong resemblance to 



* E. A. Letts, Trans. Roy. Soc. Edin. vol. xxx. part 1, p. 285. 



