318 Intelligence and Miscellaneous Articles. 



DECOMPOSITION OF METALLIC ACIDS BY IODIDE OF POTASSIUM. 

 BY M. SCHONBEIN, 



The author states that the antimonic, chromic, molybdic, tungstic, 

 stannic, titanic, arsenic and even phosphoric acids, are decomposed 

 either with or without heat by iodide of potassium. The iodine is 

 disengaged, and a salt of potash is formed. Perchloride of iron, 

 peroxide of iron, the persalts of iron and the salts of copper, act 

 similarly on iodide of potassium. 



Bromide of potassium acts like the iodide ; but neither the chlo- 

 ride of potassium or sodium is decomposed under the same circum- 

 stances : the chlorides of barium, strontium, calcium and magnesium, 

 and probably those of many other metals, lose chlorine when heated 

 with bichromate of potash. 



M. Schonbein states also several experiments performed to show 

 the deoxidizing power of powdered charcoal in different solutions. 



A solution of sesquichloride of iron is reduced to that of proto- 

 chloride when agitated with powdered charcoal. Calcined lamp- 

 black is more powerful than common wood- charcoal : even coke pro- 

 duces the effect. 



The solutions of persulphate, pernitrate and peracetate of iron are 

 reduced, like the perchloride, by charcoal. The red prussiate of 

 potash dissolved in water is reduced to the state of yellow prussiate 

 when treated with the powder of common charcoal. 



Under the same circumstances the bichloride and pernitrate of 

 mercury are reduced to protosalts of mercury. These reactions are 

 certainly very curious ; but the interest is doubled by experiments 

 undertaken to explain them. What is the effect of the charcoal on 

 these reductions ? This question is not solved by M. Schonbein. 

 It is difficult to believe that carbonic acid is formed ; and yet if cal- 

 cined lamp-black is proper for these experiments, as stated by M. 

 Schonbein, it is impossible to attribute these reductions to the hy- 

 drogen which charcoal may contain. — Journ. de Pharm., Avril, 1850. 



NOTE BY M. DU BOIS-REYMOND ON M. MATTE UCCIS PAPER 

 ON ELECTRO-PHYSIOLOGY. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



The Philosophical Magazine for June 1850 (vol. xxxvi. p. 489) 

 contains an extract from a paper on Electro-Physiology by Signor 

 C. Matteucci, read at the Royal Society, in which I find the follow- 

 ing sentence: — "M. Du Bois-Reymond {Comptes Rendus) has related 

 an experiment seeming to lead to the inference that section of the spinal 

 marrow increases the excitability of the lumbar nerves, at least during 

 a certain period of time." 



I beg to state that I never have, either in the Comptes Rendus or 

 anywhere else, described such an experiment, or any similar obser- 



