288 .,^^,^^r,q^fid\\4nal^sii Q^vft.Nvv.> 



^ Of these constituents the nmriatjc acid is saturated, by tlie 

 alkalies. The other bases are therefore united to sulphuric aci4' 

 and after saturating tlie alumina, magnesia and lime, there rf-- 

 main 1^.209 of sulphuric acid, >yi)ic.h mu<st be united with oxi^^j 

 of iron. This quantity, it will be observed, is nearly equal to . 

 that of the oxide of iron itself The iron, it appears from the , 

 aqtion of reagents which I have detailed in a former part of the 

 memoir, must be partly in the state of peroxide, and partly in , 

 that of protoxide; the former, however, constituting considerably 

 the larger proportion, as is cvidept from th^ colour of the water 

 and from the effects of these reagents. I think it most probable, , 

 that, when the water is in a quite fresh state, the b^SQ is the. \ 

 black oxide of iron, or, ipaore correctly speaking,, the. co^stitW/^Pt A 

 atoms of that oxide, which are 2 atoms of peroxide + 1 atom 

 of protoxide ; and that the salt has arisen from the gradual 

 and partial peroxidation of a protosulphate of iron. Indeed, 

 many of the leading characters of the water are those given by 

 Gay Lussac* and Berzelius-|- as belonging to a solution of the 

 black oxide in sulphuric acid. Such are the dark precipitate 

 with ammonia, the fine blue with nutgalls and ferro-prussiate 

 of potash, and even the natural colour of the water. Supposing 

 this oxide to exist in the water, the ratio of the base to the acid, 

 it would appear, ought to be as 14.5 (2 at perox. -f 1 at pro- 

 tox) : 15 (3 at sulphuric acid).:J: - i 



;. .. • ;wr' 



• Annales de Chimie, Ixxx, 166. '' ' 



t LeVWh der Chemie, ii. 735. , ^i^,o ii'jM.r- 



X. Berzelius (Lehrbuch der Chemie, ii. 736) has described a red salt found 

 in the copper-mine of Fahlun, in Sweden, the constitution of which, both aa 

 regards the nature of the base, and the relative proportions of base and acid, 

 seems to have been analogous to that of the salt of iron contained in the 

 Vicar's Bridge water. It occurred in the form of large stalactites, composed 

 of small transparent crystals, and mechanically mixed with sulphate of mag- 

 nesia. Berzelius states, that he found the base of this salt to be the black 

 oxide of iron (eisen oxyd oxydul), and the acid to contain twice the oxygen 

 of the base. It would seem, however, that the combination could not have 

 been in atomic proportion, if the base was strictly the ferrosoferric oxide 

 and if the oxygen of the acid. was exctctly twice that of the base. The nearest 

 approach to that ratio in an atomic combination would be 9:4. This is the 

 ratio of the oxygen of 3 atoms sulphuric acid to the oxygen of 1 atom pro- 

 toxide, + 1 atom peroxide, which is Berzelius* vie^v of the constitution of 



