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when filtered, gave a manifeft black tinge to the folu- 
tion of vitriol. 
Exreriment XXII. 
The officinal decodion, when cold, gives an evident 
black colour to the folution of vitriol. 
Ob. Dr. Lewis obferves, that the decodions of the 
bark affied the folution of vitriol in a much (lighter 
manner than the cold infufion ; from whence he infers, 
that the latter is more fully impregnated with the 
vegetable gummy matter than the former. I cannot 
fay that I have obferved any difference in the colour 
they ftrike with the folution of vitriol, and am inclined 
to think, the refinous as well as the gummy part 
po(fe(fes this power. 
Experiment XXIII. 
The matter, which had fubfided from an officinal 
decodion, and which appeared to be purely refinous, 
diifolved in redified fpirit of wine, changed the folution 
of vitriol to a black colour. 
Ob. The fpirit of wine alone produced no change 
in the folution of vitriol. 
Experiment XXIV. 
Three parcels of bark, of half an ounce each, were 
infufed in equal quantities of the proof fpirit of the 
(hops ; after 24 hours one portion was filtered j another 
after 48 hours ; and the third after 72 hours, or three 
days. The fame quantity of each filtered liquor was 
united with equal quantities of the folution of vitriol ; 
and after the decompofed matter had per fedly fubfided, 
the united liquors were each paffed through three 
filtres of the fame weight, which, when dried, were 
weighed 
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