37 



I need not here enlarge upon the additional value which these 

 structural and physiological considerations afford, to the character of 

 " perforation " or " non-perforation " in the shells of Brachiopoda. 

 The importance of this character in systematic arrangement will 

 plainly appear, I think, from the details which I have published 

 in the Introduction to Mr. Davidson's Monograph already refer- 

 red to. 



II. " On a new Series of Sulphuretted Acids." By Dr. AU- 

 GUST KEKULE. Communicated by Dr. SHARPEY, Sec. R.S. 

 Received April 5, 1854. 



Adopting the idea that the series of organic compounds of which 

 sulphuretted hydrogen is the type, corresponds in every respect with 

 the series of which water is the type, I concluded that not only 

 mercaptans and neutral sulphides which correspond to the alcohols 

 and ethers, but also compounds corresponding to the acids, anhy- 

 drous acids and ethers of acids might be produced ; I therefore 

 endeavoured to obtain reactions which would enable me to replace 

 oxygen in the compounds of the latter series by sulphur. 



Such reactions are produced by the compounds of sulphur with 

 phosphorus the tersulphide (P 2 S 3 ) and the pentasulphide (P 2 S 5 ) 

 which are easily obtained by fusing together amorphous phosphorus 

 and sulphur in an atmosphere of carbonic acid ; no explosion takes 

 place, although the combination is attended with a very violent 

 action. 



Experiment has proved that these combinations of sulphur and 

 phosphorus act on the members of the series of water in the same 

 manner (although less violently) as the corresponding compounds 

 of chlorine and phosphorus ; however, with this difference, that by 

 using the chlorine compounds the product is resolved into two groups 

 of atoms, while by using the sulphur compounds there is obtained 

 only one group ; a peculiarity, which, according to the bibasic nature 

 of sulphur, must have been expected. By acting on these com- 

 pounds of sulphur and phosphorus with water one atom of sulphu- 



VOL. VII. E 



