532 
confequence of being blinded by inconti- 
nence ; but being fober and vigilant, they 
acutely perceived that all thefe things 
were increafed through common friend- 
fhip, in conjunétion with virtue; but 
that, by eagerly purfuing and honoring 
them, thefe external goods themfelves 
were corrupted, and together with them 
virtue and common friendihip were de- 
ftroyed. From reafoning of this kind, 
and from the continuance of a divine 
nature, all the particulars which we 
have previoufly difcufled were increafed 
among them. But when that portion of 
divinity, Or divine deftiny which they 
enjoyed vanifhed from among them, in 
confequence of being frequently mingled 
with much of a mortal nature, and hu- 
man manners prevailed, then being no 
longer able to bear the events of the pre- 
fent/ life, they acted in a difgraceful 
manner. Hence to thofe who were capa- 
ble of feeing, they appeared to be bafe 
characters, men who feparated things 
moft beautiful from fuch as are moft ho- 
nourable: but by thofe who were unable 
to perceive the true lire, which condués 
to felicity, they were confidered as then 
im the higheft degree worthy and bleffed, 
in confequence of veing filled with an 
unjuft detire of poffefling and tranfcend- 
ing in'‘power. But’ Jupiter, the god of 
gods, who governs by law, and who is 
able to perceive every thing of this kind, 
when he faw that an equitable race was 
ina miferable condition, and was defir- 
ous of punifhing them, in order chat by 
acquiring temperance they might poffets 
more elegant manners, excited all the 
gods to aflembie in their moft honourable 
habitation, whence, being feated as in 
the middle of the wniverfe, he beholds 
all fuch things as participate of genera- 
tion: and having affembled the gods, he 
thus addreffed them :| Plato was prevented 
by death from finifhing this moft intereit- 
ing dialogue. 

EXPERIMENTS ON PRUSSIAN BLUE, 
BY M.. PROUST.——ANNALES DE 
CHIMIE, NO. 67. 
tt has been imagined that iron is ca- 
pable of uniting with oxygen in every 
proport on between .27 and .48 3 but a 
number of faéts {eem to fhow that this is 
not the cafe in every inftance: fcr not- 
withfianding the firong attraction waich 
the oxyds of this metal have for oxygen 
when expofed to. the air, we are only 
cquainted with two of its fulphates. 
2 
Experiments on Pruffian Blue. 
! FSup. 
The firft is the’ green cryftallizable 
fulphate, in which, as Lavoifier has 
fhown, the metal contains only .27 of 
oxygen. This falr, when pure, is infos 
luble in fpirit of wine: its folution in 
water has a very flight green tinge, it 
does not give a black-with the acid of galls, 
nor a blue with the alkaline pruffiates. 
‘The fecond {pecies of fulphate, no lefs 
invariable’ in its properties, is that red 
deliquefcent falt known by the name of 
mother-water of vitrol. It is foluble in 
alcoho!, not fufceptible of cryftallizationr, 
and not altered by oxygenated marine 
acid. It contains .48 of oxygen. This 
fulphare poffeffes exchafively the preperty 
of giving a black- precipitate with galls, 
and a blue with alkaline -pruffiates. 
‘Fhere is no intermediate falt between 
thefe two. The green fulphate, when 
expofed to the air, is partially converted 
into the other, which latter is feparable 
by alcohol. The precipitates from thefe 
falts, by cauftic alkalies, preferve proper- 
ties pecuhar to each. That from the 
green fulphate is green at ‘firft, but foon 
blackens if kept under water and not in 
eontaét with air, . Fhe red fulphate gives 
a yeHow precipitate which is not altered 
by air nor by oxygenated marine acid. 
In like manner we have two muriates, 
two arfeniates, and two pruffiates of iron, 
and every folution of this metal im any of 
the above acids contains two falts, the 
one, in which the metalic oxyd con- 
tains .27 of oxygen, and the other, .48. 
It is to the pruffiates of trom that Mr. 
Prouft has particularly attended. 
' To obtain the while pruffiate of iro, & 
very pure folution of the green fulphate 
of iron mut be employed; and for this 
purpofe, the falr mutt be kept in a wells“ 
cloféd bottle, and lying on a tin or iron 
plate. The fame end, however, ts an- 
{wered by converting the red oxyd that 
may be found in the folution, imto the ftate 
of black oxyd, by. adding fome water 
faturated with fulphurated hydrogenous 
gas.. The fulphate, thus purified, fhould 
not be altered by the gallic acid. To 
this folution muft be added a folution of 
pure pruiiate of pot-afh, when anabundant 
white precipitate will ‘be formed, which 
foon takes a flight green tinge. This 
precipitate hasa ftronger affinity for oxygen 
than any of the known falts of iron, and 
in faturating itfelf with this principle, it 
affumes a deep blue. Neither the fulphu- 
ric nor muriatic acids produce any change 
on. this precipitate, but the oxygenated 
muriatic acid inftantly turns it blue, and 
: lofes 
4 
