Intelligence and Miscellaneous Articles. 24 1 



most sensible tests, but merely manganese, which existed in the 

 state of sesquioxide ; this was derived from the iron. It is therefore 

 evident that iodide of iron obtained by evaporation to dryness is a 

 very imperfect preparation, and that its employment is attended with 

 some inconveniences. 



During the evaporation of a solution of protiodide of iron, disen- 

 gagement of hydriodic acid gas takes place, and from this results 

 the first decomposition of the salt ; and a product is obtained con- 

 taining a corresponding quantity of oxyiodide, mixed with undecom- 

 posed iodide ; and this decomposition of the solution into hydriodic 

 acid and oxyiodide does not cease until the aqueous vapour is pro- 

 duced in sufficient quantity to prevent the contact of the air with 

 the salt in solution. 



M. Calloud observes, that by analogy with the chlorides of iron 

 the periodide of iron should be a more stable compound than the 

 protiodide ; experience however shows that this is not the case, for 

 the iodide of iron, being constantly subjected to the hygrome- 

 tric and oxygenating action of the air, becomes completely decom- 

 posed, even at tbe usual temperature of the air ; and when the iodide 

 of iron of the shops is examined, lamina? of crystallized iodine, adhe- 

 ring to a bluish friable insoluble mass, may be seen by the naked 

 eye ; this substance is merely a mixture of reduced iodine and ses- 

 quioxyiodide of iron. — Journ. de Chim. MM., Aout 1846. 



ON THE SOLUBILITY OF ALUMINA IN SOLUTION OF AMMONIA. 



MM. J. Malaguti and J. Durocher state that in analysing the 

 laumonite it was found an enormous loss of alumina was sustained ; 

 it is well known, they observe, that this mineral is a silicate of lime 

 and of hydrate of alumina ; on account of the presence of lime the 

 authors diluted the acid solution before precipitating it with am- 

 monia. They were surprised on obtaining in this manner only 8 out 

 of 100 of alumina, notwithstanding the presence of some sal-ammo- 

 niac in the solution ; and one of the authors states that several years 

 since, in making numerous analyses of kaolin by hydrofluoric acid 

 (a process in which it is requisite that the solution of the alumina of 

 the mineral should be very dilute), he was obliged to give up the use 

 of liquid ammonia as a precipitant and to employ sulphuret of am- 

 monium, on account of the large quantity of alumina which re- 

 mained in solution. 



It is, indeed, well known that alumina is never precipitated per- 

 fectly from its solutions by ammonia, without the presence of ammo- 

 niacal salts. The quantity which remains in the liquid, far from 

 being scarcely appreciable, may on the contrary exist in considerable 

 proportion, and which is increased, not only by the excess of ammo- 

 nia, but also according as the solution is more or less diluted with 

 water. 



Alumina is indeed precipitated entirely when ammoniacal salts 

 are present ; but the quantity of these salts ought to be greater as 

 the solution of alumina is more dilute. Alumina may be separated 



