VOL. LXIV.] I'HILOSOPHICAL TRANSACTIONS. 545 



acid of vitriol. And here, by the way, it may be proper to remark, that the 

 vitriolic aeid, when mixed with the acidulae and other chalybeate waters, does not 

 preserve those waters from decay, as Hales, and others, after him, have supposed; 

 but, on the contrary, destroys their texture, or decompounds them, by expelling 

 their elastic spirit, and entering into new combinations with their earthy prin- 

 ciples; thus forming a new compound, less perishable indeed than the former, 

 but also less efficacious in the cure of many diseases. When Rhenish wine is 

 added to the acidulae, the large quantity of air that flies off may, in part, pro- 

 ceed from the wine; but when Dr. B. mixed the vitriolic acid with Pouhon water, 

 a considerable quantity of air was indeed discharged; but not the whole which 

 that water holds in solution. He therefore conjectured, that some part of the 

 air, contained in that water;- might be imbibed by the superabundant acid, which 

 he used in the experiment, and that more mephitic air might perhaps have been 

 expelled from the water, had he only mixed with it the exact quantity of this 

 acid, that was required to dissolve the earthy substances contained in it. 

 • Thirdly. These saline concretes, contained in the Pouhon water, and other 

 acidulae, are subject to decomposition, not only from acids, as before related, 

 but also from alkalies, whether fixed or volatile: all which more powerfully 

 attract this subtile aerial principle than it is attracted by the martial and 

 absorbent earths, to which it is united in those waters. And here again appears 

 an exact agreement between these aereo- saline concretes, and various neutral 

 salts, in the mode of their decomposition. For the ammoniacal salts (which are 

 all composed of the volatile alkali, united to an acid spirit, either muriatic, 

 nitrous, or of some other kind) as soon as one of the fixed alkalies, or quicklime, 

 is added to any of them, the acid spirit which it contains, quitting its union 

 with the weaker volatile alkali, this last is let loose ; and the stronger alkali, or 

 quicklime, takes its place ; between which and the acid spirit a new combination 

 is formed. The same happens when any alkali, either fixed or volatile, is added 

 to the acidulae; their elastic spirit then quits the ferruginous and absorbent 

 earths, to which it was joined, and forms a new combination with the alkali, by 

 which it is more powerfully attracted than by these earthy substances. These 

 earths therefore, being no longer suspended in the water by the aerial solvent, 

 render it turbid and milky, until they have gradually subsided in it, in the form 

 of a white sediment : for such is the native appearance of the martial earth, as 

 well as of all the other earths contained in these waters, as will be shown here- 

 after. In these decompositions of acidulous waters, by means of alkalies, no 

 effervescence, or discharge of air bubbles, takes place; for here the air is all 

 absorbed by the alkali added, and not expelled from the water, as it is in the 

 decomposition of the same waters, by means of stronger acids. 



When the acidulae are mixed with common soap, a two fold decomposition 



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