Royal Society. $1 
Jin E^priment on the EffeBs of the Air on a tranfpamit 
Liquor, applied to esplain Changes of Colour in the plocd 
of refpiring Animals-^ hy Dr. Slare. Phil. Tranf. N° 204. 
p. 898. 
PU T a c^uantity of frefh filings of copper in a phial, whofe 
bottom IS broad and even, and then pour on them an urinous 
fpirit, either of fal-armoniac, or of urine itfelf, not made with 
quick-lime, the glafs is not to be filled much above half, and 
then it muft prefeVitly be foclofely Hopped, that no air be admit- 
ted; for an error in one circumference, will marr the whole 
experiment: In making the experiment, you will obferve, for 
four, five, or fix days the tin61ure becoming deeper and deeper, 
and then it will be at a ftand for two or three days, miOre or lefs» 
and afterwards it will gradually decline, until it become quite 
pale, and void of all colour 5 when it is in this ftate, the eafieil 
way of performing the experim.ent, is to decant this clear fpirit 
into a glafs, fo asm leave all the filings behind, which will fliew 
that the filings did not give this tin6^ure a-ncw, but thatjt is Giv- 
ing to the influence of tlie air 5 but in cale you are furniihed with 
an air-pump, and can pour off this pale liquor in Vacuo, and 
there ftop it up clofe, you may then preferve it as long as you 
pleale, and exhibit it to advantage ; you may alio obferve, that 
as fbon as you admit the air, the upper furface becomes imme- 
diately firft tinged, and fo the tin^ure defcends deeper and 
deeper, until it"^has penetrated the whole; and this it does the 
fooner if the glafs be wide, and the liquor by conlequence have 
a larger lurface^or if you pour it out of one glals into another, the 
air makes a more fudden change of the whole: That liquors 
fhould lole their tindures is not to be wondered at; for even ink 
itfelf, by ilanding {till, will lofe much of its tindure, and lo do 
the tin6tures of many minerals; tincture of iulphur, and ofialtof 
tartar will lofe their colours, and many vegetables are not long to 
be preferved, but grow turbid; fome becoming pale andcolourlels, 
leave their Menfirua, and precipitate to the bottom, and are not 
cafily, if ever recovered : In this experiment we have lome things 
very uncommon ; viz, that a deeply tinged liquor fliould grow pale 
and colourlefs in a few days, without any admillion of air, or any 
other ingredients to difturb it,ortocaule any dilcernible precipita- 
tion or feparation, and that upon the re-admiffion of th- air, the 
liquor fiiould recover its former blue tmaure. This influence of 
the air in this experiment, made Dr. Slare apply it 10 the great 
change, that is made upon blood 5 for it is obvious to every body, that 
VcL. III. L there 
