240 Intelligence and Miscellaneous Articles. 



2nd. That the rock is essentially composed of carbonate of lime, 

 with a small quantity of carbonate of magnesia and of manganese. 



3rd. That the rock contains a small propoition of argillaceous 

 earth in a state of mixture, which separates when the rock is dis- 

 solved by a weak acid at common temperatures. 



4th. That additional researches are required to ascertain from 

 what substances marine plants obtain the iodine which they contain, 

 if we admit, with the chemists above-quoted, that it is not found in 

 sea-water, even in very minute quantity. — Journ, de Chim. Med., 

 Juin 1846. 



PREPARATION OF PROTIODIDE OF IRON. BY M. C. CALLOUD. 



To determine the nature of this preparation, as usually obtained, 

 the author examined several specimens of it, and he found not only 

 that the iodide had suffered great change, but even entire decompo- 

 sition ; in the latter case the substance appeared to be soluble in 

 water, but this solubility was owing to the accidental presence of a 

 saline iodide, entirely different from iodide of iron ; he found that 

 some which had been recently prepared was half-decomposed ; some 

 which had deliquesced, was decomposed to the extent of three-fifths, 

 while a portion which had been dried after deliquescence was totally 

 decomposed. 



One hundred parts of the dry iodide of iron of druggists were 

 treated with distilled water ; the solution, after being filtered to se- 

 parate the insoluble portion, was treated with solution of potash, 

 which precipitated the portion of iron remaining combined ; calcula- 

 ting from the portion remaining insoluble in water, and from that 

 precipitated by potash, the composition of the iodide appeared to be, 

 Iodide of iron, presumed to be in the state of protiodide 54*20 



Iodine uncombined 34*80 



Sesquioxide of iron 1 1*00 



10000 



The second specimen appeared to consist of — 



Protiodide of iron 38*80 



Iodine uncombined .... 41*70 



Sesquioxide of iron .... 14*50 



Hygrometric moisture . . 5*00 



100*00 



Both these preparations yielded turbid solutions of a deep colour, 

 and possessed the odour of iodine ; they did not exhibit the proper- 

 ties of persalts of iron when submitted to the action of tests ; they 

 gave a bright blue precipitate with the ferrocyanide of potassium, 

 and a green one with the alkalies. 



The iodide which had been dried after deliquescence, was, as al- 

 ready stated, entirely decomposed, and all the iron had become oxy- 

 iodide, forming with the reduced iodine a mixture totally insoluble 

 in water ; no trace of iron could be detected in the solution by the 



