VOL. X.] PHILOSOPHICAL TBANSACTIONS. 247 



by the solution of some of the copper, and lost that colour again, growing clear 

 like common water, and then taking out the stopper, without shaking the 

 liquor, thereby giving access to the outward air, the upper surface of the liquor 

 in a few minutes resumed a darkish brown colour, which penetrating deeper and 

 deeper, at the end of about a quarter of an hour the whole body of the liquor 

 appeared to be likewise tinged. The conical glass being again well stopped, the 

 menstruum again, in very few days, lost its tincture ; which, the stopper being 

 taken out, it regained as before. Afterwards, keeping the glass in the same 

 place with the same filings and menstruum in it, for a month or two together, 

 the liquor would not any more grow clear. 



Exper. II. Having taken another such glass, wherein the liquor was grown 

 clearer than is usual. We took out the stopple, and left it open for about half 

 an hour, but did not perceive the liquor to have acquired any colour, not even 

 at the top. But putting in the stopple, and leaving the vessel closed for two 

 or three hours, it acquired a faint colour, tending to a green; wherefore, taking 

 out the stopple again, and leaving the glass unstopped for 20 or 24 hours, in 

 all that time it had not regained its wonted dark colour, but was only arrived at 

 a green, deep enough, but neither true nor very transparent. 



Exper, III. Some strong spirit of salt having been kept upon filings of copper 

 till the solution was become of a dark brown colour, about three spoonfuls of it 

 was put into a receiver that might hold eight or ten times as much: being kept 

 in vacuo about half a year, it retained its colour. But the vessel being opened, 

 and the external air admitted, the solution in about an hour was turned into a 

 fine transparent green, though no precipitation of any muddy substance ap- 

 peared by any sediment to be made. 



Exper. IV. On putting into another conical glass some filings of copper, with 

 a convenient quantity of spirit of salt ; after a few weeks it lost its muddy tinc- 

 ture, and appeared like common water. On unstopping the glass, to give free 

 access to the outward air, we observed, that in some hours its operation on the 

 liquor was scarcely sensible, but within about 24 hours the menstruum had ac- 

 quired, not just its former colour, but a somewhat faint and moderately trans- 

 parent green: so that this tinged menstruum, as it had been very slow in losing 

 its colour, so it did but slowly and imperfectly regain it. 



Exper. V. We put some filings of copper, with a mercurial gauge, in a coni- 

 cal glass, fitted with a ground stopple, and poured on the filings rectified spirit 

 of fermented urine made per se, to the height of an inch or better above them ; 

 then carefully stopping the glass several hours after, the mercury in the sealed 

 leg was considerably depressed; and gently drawing out the stopple, to let in 

 the air, we perceived it to have a manifest effect on the mercury. 



