240 PHILOSOPHICAL TRANSACTIONS. [anNO 1765, 



Dr. B. had several times occasion to repeat the above operation : and found 

 that all the elastic substance could scarcely be expelled from fresh Pouhon water, 

 by the above degrees of heat, in a much shorter time than that employed in the 

 foregoing experiment. For a common quart flask of this water, having been 

 kept 3 hours in a water bath, heated to as great a degree as he could well endure 

 with his hand, which might be about 130 degrees, according to Fahrenheit's 

 scale, and having afterwards stood 24 hours before the bladder was removed from 

 it ; when opened, was found turbid, but bad not deposited all its earthy particles, 

 and still retained a little of its brisk taste. Another flask of the same water, 

 fitted in like manner with a bladder, was kept 2 hours in a scalding heat, of 

 about ]6o or 170 degrees of the same thermometer, so that most of its elastic 

 substance seemed forced from it; yet when the flask was opened the next day, 

 the water struck a purple colour with galls, and had not quite lost its sharp sub- 

 astringent taste; and after about -^ part of this water was poured out, and the 

 rest shaken briskly in the close flask, and then suddenly opened, an elastic sub- 

 stance was still discharged from it, with a considerable explosion. 



From these experiments we learn, " that the Pouhon water contains a large 

 quantity of a very subtle, light, and permanently elastic fluid, or of a true mi- 

 neral air; and that this aerial fluid is closely united to the other principles of 

 which this water is composed." For, from exper. 1 , it appears, that when this 

 water is excluded from all communication with common air, and at the same 

 time liberty is given to the aerial fluid contained therein to expand, and to fly 

 from it, with the same facility as from the water in an open vessel; yet under 

 these circumstances, this elastic fluid does not exert its power of expansion, but 

 remains so firmly united to the other principles of this water, that it does not 

 separate from them when agitated, for several days, with a heat of 80 degrees of 

 Fahrenheit's thermometer. While therefore this water is in its natural state, 

 and is not acted on by any other body, the aerial principle remains quiet: and, 

 with the other principles, seems equally dissolved in the watery element. It is 

 not, therefore, then confined by any external force, like the air of beer, cyder, 

 champaign, and other huffy liquors, which, while they are closed in bottles or 

 other vessels, by their fermentatory motion, generate more air than they can im- 

 bibe and keep dissolved; so that much of the air so generated is pent up in a 

 confined state, and continually presses on every side, until a vent is given it, 

 and then it rushes out with violence. But it appears, that this subtle elastic 

 fluid, while it is associated with the other principles of the Pouhon water, and is 

 kept from contact of common air, and of such other bodies as are found to de- 

 compose this water, it remains in a quiet dissolved state, intimately mixed witli 

 the other principles of which this water is composed, and so closely joined to 

 them, that it is not readily separated from them by a less heat than that of 100 



