354 Analysis of the Hot Springs at Bath. 



ment was made with the intention of trying whether this 



effect of slow oxidizement might be imitated : 



(r) Infusion of galls is, as has been seen, capable of acting 

 upon T-fj-!,n^dth of a strain of protoxide of iron in one ounce 

 of solution of carbonate of lime (/). A portion of sulphate 

 of iron containing ^-rg-dth of a grain of protoxide was dis- 

 solved in one ounce of dilute solution of carbonate of lime, 

 and was kept in contact, with about one-fourth of its volume 

 of atmosphei-ic air, during twenty-four hours. At the end 

 of that time the solution remained perfectly transparent, and 

 without having precipitated ; but the addition of infusion of 

 galls did not occasion the slightest appearance of having 

 acted upon the oxide of iron. In this experiment the loss 

 of power of infusion of galls is much more speedily eflfected 

 than in the Balh water. This is evidently owing to the at- 

 mospheric air contained in the distilled water employed, 

 while no oxygen gas is present in the Bath water. 



When carbonate of lime is added to sulphate of iron it is 

 \vell known ttiat double decomposition takes place, the iron 

 being thus combined with the carbonic acid instead of the 

 sulphuric. Having found that infusion of galls, in several 

 instances, acts much more readily upon carbonates than 

 iulphates, I imagined that the carbonate of lime produced 

 its effect in this wav. To ascertain whether this supposition 

 w as correct I made the following experiment : 



(s) A quantity of the solution of green sulph.ate of iron, 

 similar to that employed in the above-related experiments, 

 was decomposed by carbonate of potash ; carbonic acid gas 

 was passed through water in which the washed carbonate of 

 iron was diffused, and to some of the filtered solution in- 

 fusion of galls was added j but, instead pf the red purple co- 

 lour effected by the action of carbonate of lime upon sul- 

 phate of iron and infusion of galls {k) and (/}, the usual 

 deep blue colour was obtained. 



{t) One-tenth of the quantity of carbonate of iron em- 

 ployed in the last .experiment was dissolved in a solution of 

 carbonate of lime equal in measure to the last solution. 

 To this infusion, of galls was added. The red purple 



colour 



