[ 222 ] 
in a room many weeks; yet although It was fre- 
quently fliaken, and had an ochrous fediment, it gave 
no colour with tindure of galls, 
Experiment V. 
A fingle grain of iron in folutlon^, diluted with a 
pint of dihilled water, changed to a deep blue purple, 
with the tindure of galls. Half a pint of the like 
mixture, expofed many days in a wide- mouthed 
glafs covered loofely with paper, let fall a flight pre- 
cipitation ; but its property of tinging with galls was 
not fenfibly diminifhed. The fame quantity being 
boiled four or five minutes, in a Florence flafk, be- 
came turbid, and depofited a fmall portion of an 
ochrous fediment. The tindure of galls, never- 
thelefs, gave as deep a colour to the clear liquor, as 
it would have done before boiling. 
The foregoing experiments feem to prove, that 
iron remains quite unaffeded by pure water, but may 
eafily be diffolved in it on the addition of fixed air ; 
and that in whatfoever manner this air is generated, 
the event will appear the fame. The laft experiment 
fhews, that where iron is fufpended in water, by an 
acid, neither expofure nor boiling will deflroy its pro- 
perty of tinging with galls ; which is the reverie of 
what we find to be the cafe with many ferruginous 
waters. Experiment the Second more particularly 
* Iron-filings were diffolved in diluted oil of vitriol to fatu- 
ration ; and, by experiment, one grain of the metal, with about 
two grains and a quarter of the acid, were found to be con- 
tained in fixty-eight grains of the folution* 
teaches, 
