Mr. Smee on the Ferrosesquicyanuret of Potassium. 193 



" As to what relates to chemical types, which M. Dumas 

 says I do not admit, I dare hope that the Academy, and all 

 enlightened men will not participate in this opinion ; for it 

 will without doubt be allowed that he who first classed che- 

 mical types, must necessarily have admitted them, even before 

 M. Dumas had acquired any notion of them, as his memoir 

 appears to show, since he makes this notion only go back to 

 his experiments on chloracetic acid, the discovery of which is 

 posterior to my thesis." 



M. Dumas replies, that his memoir is conceived in such 

 terms, that it should have spared the Academy all the recla- 

 mations of which it has been the subject. In a historical note 

 which he intends soon communicating to the Academy, he 

 will show in what the views which are represented as identical 

 differ, and to whom belongs the discovery of each of the prin- 

 cipal points of the theory. 



XXVII. On the Ferrosesquicyanuret of Potassium. By 

 ALFRED SMEE, Esq., Surgeon.* 



THE action of chlorine upon the ferrocyanate of potassium 

 is a subject of much interest to the chemist, and has not 

 been examined to any extent in this country. It therefore 

 has been my endeavour to investigate this action carefully, and 

 to see under what circumstances the change from the ferro- 

 cyanate into the ferrosesquicyanuret takes place ; and the 

 methods which are here detailed to obtain this latter salt un- 

 contaminated with impurities, will be found free from the dif- 

 ficulties and uncertainties attending on the present mode of 

 preparing it. 



When a current of chlorine is passed through a solution 

 of ferrocyanate of potassa, or an aqueous solution of that gas 

 is added to it in certain quantities, the persalts of iron are 

 not precipitated. This solution has no smell of chlorine, and 

 is changed from a yellow colour to a dark red, and deposits on 

 evaporation red crystals. A similar change takes place when 

 bromine is added to the ferrocyanate, and in both cases the 

 weight of the entire red mass is equal to that of the yellow 

 ferrocyanate, plus the weight of the chlorine or bromine used, 

 but minus the quantity of water which the yellow crystals are 

 known to contain. This indicates, first, that the red crystals 

 are anhydrous ; and secondly, that the chlorine or bromine 

 is actually absorbed by the salt. The former fact is con- 



* Read before the Royal Society, June 18, 1840; and now communi- 

 cated by the Author. 



PhiL Mag. S, 3. Vol. 17. No. 109, Sept. 1840. O 



