gyQ OXIDATIONS OF IRON. 



exposure to the air for a month ; I have made several other 

 experiments tending to the same object: and they have all 

 convinced me, that the air has no superoxiding action on 

 solutions of iron, at least at the common temperatures. ; Of 

 these I shall recite only two, that are among the most con^ 

 elusive. 

 Farther proofs. J.. I dissolved two equal portions of iron under circum- 

 stances perfectly similar. One of the solutions I put into a 

 glass three inches in diameter, and immersed in it a curved 

 tube, the extremity of which was a ball pierced with several 

 holes. Through these 1 passed atmospheric air for seven hours 

 at different times. At the expiration of three days, I com- 

 pared these two solutions in various ways, and found, that the 

 . one into which I had forced air was perfectly similar to the 

 other, which was not perceptibly altered, though the tempe- 

 rature was 1 2° [59° F.]. 2. By means of the same apparatus 

 I passed about three quarts of oxigen gas through a solution 

 of ten grains of iron, and, though the temperature was 2$* 

 [88°£ F.], it had no action on the solution. 



On the'-colour of the green oxide. 



Particles of On adding a few drops of alkali to a solution of iron a 



precipitated ]j tt | e diluted, I observed, that every particle of the oxide 

 oxide of iron , ,. ... •, ; , ,. u • j i 



hollow spheres was formed of a very thin pellicle, including some fluid, and 



containing a j accounted for the green colour by the difference of density 

 between this pellicle and the fluid it enclosed. I likewise 

 This might ac- ascribed the alteration in green solutions exposed for some 

 count for their days to a temperature of 20° [77° F.] to the bursting of these 

 change of co- . d , th dilatation of the fluid contained in them-, 



lour in some «="«•■'*«> »j . . 



cases, To the pressure exerted upon these vesicles 1 attributed the 



unehangeableness of these solutions in bottles quite full and 

 but not in close stopped. But I could not reconcile with these modes 

 others. of viewing the subject the change, that is induced in green 



solutions of iron by oxigenized muriatic acid, and in red so- 

 lutions by sulphuretted hichogen. The nature of the con- 

 stituent principles of these two'reagents renders the manner 

 in which they are supposed to act in these two experiments 

 so plausible, that I should not have withheld my assent to 

 them, had I not been convinced by all the facts I have re- 

 lated, 



