ALUMIXOUS CHAtrBEATE SPRING IN I. OF WIGHT; ^5 



rate the alumine, after which the residue, now supposed to 

 contain nothing but carbonate of lime and iron, was treated 

 with dilute muriatic acid, which dissolved it with efferves- dissolved in 

 acence. From this solution the lime was precipitated by murjatlc "c^* 

 oxalate of ammonia, and the remaining liquor now con- precipitated by 

 taining nothing but muriate of iron, was treated with car- nionia 

 bonate of ammonia, so as to precipitate the whole of the and the iron 

 iron, which, in subsiding, assumed a pale reddish colour, by™*^,^" 

 The clear fluid being decanted off, and the precipitate of ammonia, 

 carefully washed, dried, and ultimately heated to redness 

 with a little wax in aplatina crucible, weighed 7*2 grs. 



3. It will be observed, that between this and the former Difference of 

 result there was a difference of 0*4 grs in the quantity of resu ts * 

 oxide of iron contained in 50 grs of residue. But when it 



is considered, that in the first of these analyses a small 

 quantity of iron was positively detected in the acetic solu- 

 tion, which, from the best estimate I could make, would 

 huve brought the quantity of iron very near that obtained 

 in the second process, it will readily be admitted, that the 

 coincidence was such as to authorise me to consider the last 

 result as sufficiently accurate*. 



4. If therefore we consider 7*2 grs of peroxide of iron, as Proportion of 



the quantity of this metal contained in 50 grs of the resi- °* ide m , sul - 



. . phate of non» 



due, which corresponds to 11*59 grs of the oxide for 80*5 



grs of residue (that is for each pint of the water according 



to the average before established, sect. VII, 2), we shall 



be able so infer the quantity of sulphate of iron contained 



in the water. 



5. In order to do this, however, it was necessary to as- Proportion of 

 certain by a comparative experiment the proportion of ox- phate of iron. 

 ide, which a known quantity of sulphate of iron yields by 



a process similar to that which I have just described. For 



* In one experiment in which the iron was precipitated from a simi- 

 lar quantity of residue, by prussiate of potash, and the prussiate of iron 

 roasted with wax, the quantity of oxide obtained amounted to 11 grs, 

 from which I infer, either, that a portion of the oxide of iron, always 

 contained in prussiate of potash, must have been precipitated with the 

 Prussian blue, or, that the prussiate of iron was not completely de- 

 composed in the process in question, or that some earthy substance 

 Was precipitated along with the iron. 



Vqu XXXII— May, 1812. F this 



