Analysis of the Hot Springs at Bath. 347 



As no metallic oxide, discoverable by sulphuretted hydro- 

 gen, was suspected, the appearance it produced (V) was 

 supposed to be derived from its action upon carbonate of 

 Inne. This was ascertiiined to be the case by direct experi- 

 ment. 



The prussiate employed by Experiment (W) was the 

 triple compound containing oxide of iron. It was ima- 

 gined that the slight greenness which was assumed by the 

 water might be occasioned bv the action of the carbonic 

 acid, notwithstanding its holding carbonate of lime in solu- 

 tion, this effect being easily produced by the application of the 

 stronger acids. A small quantity of the triple priissiate was 

 therefore added to a solution of carbonate of lime in carbonic 

 acid : after a considerable time it acquired a green colour 

 exactly similar to that observed in Experiment (W). Dr. 

 Falconer has indeed stated that a blue colour is to be ob- 

 tained by the action of prussiate of potash upon the water ; 

 but, as it did not occur till after the addition of sulphuric 

 acid, it is evident that this effect was produced by the action 

 of the acid upon the oxide of iron of the prussiate. 



Although the presence of oxide of iron is not at all indi- 

 cated by prussiate of potash, (probably on account of the 

 sniallness of its quantity,) yet it is evident from the action 

 of infusion of galls (X) that a minute portion of it actually 

 exists in the water j the light colour of the recent precipi- 

 tate, apd its becoming darker by contact with atmospheric 

 air, showing that it is in the state of protoxide. In making 

 this experiment it is requisite to use a very small quantity 

 of the infusion of galls ; for, if much more than five drops of 

 it are added to one ounce of the water, no indication of oxide 

 of iron is produced, the water becoming of a light reddish 

 brown colour, and affording no precipitate. An excess of 

 this infusion rc-acts upon the compound of vegetable matter 

 and oxide of iron so completely as to prevent the appear- 

 ances readily presented by a small quantity. 



From the well known laws of chemical affinity it is evi- 

 dent that the oxide of iron is combined with carbonic acid ; 

 this compound undergoing some curious changes, which 

 have occasioned much discussion. 



It 



