566 PHILOSOPHICAL TRANSACTIONS. [aNNO 1779- 



that of distilled water. Accordingly he found that Seine water, after it had been 

 boiled for a long time, absorbed in 40 days about -j-V of its own bulk of dephlo- 

 gisticated air, when in the same length of time it does not absorb more than -^\ 

 of common air. This seems to be an experiment ot very great consequence, as 

 it discovers a new characteristic by which dephlogisticated air may be distin- 

 guished from common air; and shows that water absorbs a greater quantity of 

 those kinds of air, which contain a less quantity of phlogiston. 



However it is impossible to determine exactly the quantity of air that is ex- 

 tracted from vessels filled with water, by means of fire; because a portion of the 

 air is absorbed by the water of the tub in the act of its coming forth. It will 

 certainly be more exact to receive the air in vessels immersed in quicksilver; but 

 then there are many other inconveniencies to encounter. 



The above experiments are very useful in explaining the reason why some 

 kinds of water have a peculiar sharp taste more than others; and especially why 

 some of them precipitate the lime in lime water, rendering it a calcareous earth, 

 and change the tincture of turnsole into a red colour, as he had generally 

 experienced with the well waters at Paris. Hence may also be explained why 

 some kind of waters can dissolve iron, and keep it in solution without deposi- 

 tion; whereas other kinds of water are incapable of doing it, at least do it much 

 less than the purest distilled water. This is soon discovered by boiling the 

 water, which will then deposit the iron which before was dissolved. 



Mr. F. had not only extracted from waters the different kinds of air they 

 contained naturally, but had also made various experiments on waters deprived of 

 air, which, being exposed, had again imbibed the atmospherical air, as above 

 hinted. He had determined the quantity and quality of those airs. In general, 

 he might say, that distilled water, deprived of air, imbibes again an equal quan- 

 tity of air of the same kind as that it had lost, and that in less than 50 days. 

 Other kinds of water do the same, but with this difference, that the air they 

 absorb, after being boiled, is better than that they had lost; and in this par- 

 ticular they come very near to the nature of distilled water itself. 



By means of pure water, especially distilled water, common air may be 

 changed into dephlogisticated air, that is, into air much more salubrious than 

 the best common air which we breathe; and this, for what he knows, is the 

 only means of meliorating common air: for all the artificial methods (great 

 numbers of which he had tried) had proved either useless or noxious, but never 

 such as promised to be of any great utility to mankind. 



Though he had long thought of applying those experiments to some use for 

 the purposes of life, the want of time and a proper apparatus had hitherto 

 hindered him doing any thing; he now began to hope to be able to do some- 

 thing. In the mean time he thought it of some importance to be known, that 



