218 Mr. Denham Smith on the 



memory the publication in which it was noticed, I am in- 

 debted to the Editors of the Philosophical Magazine for re- 

 ferring me to the Journal de Pharmacie, torn, xxvii. p. 97, 

 where I found a communication from M. C. le Fremy, upon 

 " The Action of the Alkaline Peroxides on Metallic Oxides." 

 Since the appearance of this memoir, which has been followed 

 by researches by the same author on the combination of pot- 

 ash with the oxides of zinc, tin, &c, various notices have 

 been published by MM. TrommsdorfF, Wackenroder and 

 Poggendorff, on the subject of this combination of oxygen, 

 potassium and iron, confirming the existence of this purple- 

 red compound, and pointing out various modes of obtaining it. 



I had expected that M. Fremy would have extended his 

 inquiries and ascertained the composition of this new oxide 

 of iron; but as a considerable period has elapsed since his ori- 

 ginal notice of its existence, and his subsequent researches 

 in connexion with this subject having taken other directions, 

 other chemists also having investigated the compound, and as 

 my own experiments were commenced before J was referred 

 to M. Fremy's paper, I may be excused for having thus di- 

 rected my attention to the composition of a substance, to the 

 priority of the discovery of which I have no claim, although I 

 had ascertained its existence independently of the observations 

 of the French chemist. I have entered on this explanation, as 

 I would in nowise wish to deprive M. Fremy of his just claim 

 to the original notice of this compound; but as my previous 

 observations and pursuit of the subject were entirely indepen- 

 dent of M. Fremy's notice of its existence, I feel myself jus- 

 tified in communicating the results of my investigations, espe- 

 cially as its first discoverer appears to have abandoned the 

 pursuit. 



In the memoir in the Journ. de Pharm. already alluded to, 

 various modes are pointed out for preparing this combination 

 of potash and oxide of iron, which is obtained by igniting a 

 mixture of sesquioxide of iron, potash and nitre, or peroxide 

 of potassium and sesquioxide of iron, or by calcining at a full 

 red heat potash and sesquioxide of iron ; by these means a 

 brown substance was procured which afforded a deep violet- 

 red coloured solution, very soluble in water, but which solu- 

 tion is easily decomposed; concentrated solutions of the alkalies 

 precipitate it of a brown colour, which precipitate redissolves 

 on the addition of water; it decomposes rapidly by an eleva- 

 tion of temperature, and instantaneously by the contact of or- 

 ganic substances. The same coloured solution may be formed 

 by passing a current of chlorine through a concentrated so- 

 lution of potash, holding precipitated sesquioxide of iron in 



