262 An Anahfts of two Mineral Springs 



iron, by mixing fome yellow oxyde of iron (the ruhigo ferri 

 of the fhops) with water, and expofing it, by a. proper appa- 

 ratus, to the oxygenated muriatic acid gas. The gas readily 

 diffolves a part of the oxyde, a few bubbles (perhaps of 

 carbonic acid) efcaping during the folution. 1'. The fait 

 which is formed is deliquefcent ; colourlefs ; of a pure bit- 

 ter tafle, without any of the fweet aftringency of the com- 

 mon falts of iron*. Alcalies precipitate a white oxyde. 

 The mineral acids, alfo, decompofe the fait •, and at the fame 

 time a white matter, of a cryftalline form, precipitates, but 

 an excefs of acid re-diffolves the precipitate f. 2. If fome 

 metallic iron be digefted in a folution of this fait, an ochre 

 precipitates copioufly, which is very foluble in acids. Cop- 

 per alfo decompofes the fait; but the matter precipitated is in 

 fmall quantity, and hardly foluble in acids. 3. Prufliatof 

 pot-afh is totally unaffected by this fait ; fo likewife is tinc- 

 ture of galls when the fait is quite perfect} ; but, after iron 

 has been digefted with it, galls communicate a yellow tinge, 

 or even precipitate a brownifh matter *, dill the pruffiat of 

 potafh has no effect.' Thefe properties of the fait bear fo 

 ftrong a refcmblance to appearances which I have remarked 

 in the water, particularly in the effects of the metals (iv. 

 2 & 3) and the failure of the re-agents (iv. 4 & 5.), that 

 it ftrongly confirmed me in the hypothefis I had adopted. 

 On purfuing the experiment, however, the analogy failed* 

 I added to the fait of iron very minute quantities of muriat 



* By far the bed method of making this f.ilt is to put the ruft in a fau- 

 cer, and to put the mixture of manganefe and muriatic acid, diluted to 

 avoid a ftrong effervefcence, in a cup on the fame faucer ; then to cover the 

 cup with an inverted glafs : thus the oxygenated vapour v/ill be confined 

 as it is flowly extricated. If diftillation is uled, the filt can be, 

 made free from an aftringent tafte. 



+ The fulphuric acid docs not re-difio'vethe precipitate ; the others do. 

 Some further remarks on this fubjecVwill be found v ':xiv. <,.). 



J I once faw t*ie galls form a white precipitate ; but I fufpeft the oxy- 

 genated was contaminated with fome common muriatic acid, formed by its 

 decompofition during the digeftfon. 



