364 ; C H E M I S T R Y. 
matter, and digefting it over white lead, to feparate the Solution of fulphat of iron charged ‘with nitrous gas. _If 
hepatic gas it may contain; mix it with acetic acid; ex- one gallon of nitrous gas be put into a folution, contain- 
poie it to the fun to precipitate the iron ; and then add ing an ounce and a half of fulphat of iron, more than fix 
two parts of alcohol. The Prufliat of potafli will be pre- pints of the gas will be abforbed. For this operation, 
cipitated in lameilated Aiming flocks; walh it with frefli take a doubly-tubulated bottle, as fliewn in the pre¬ 
alcohol, dry it, and dilfoive it in diftilled water. If ful- ceding engravings, and therein put the iron-filings ; to 
phuric acid" be mixed with a folution of Prufliat of ordi- one of the necks adapt a recurved tube, which is to go 
dinary potafli, a blue precipitate is obtained, by expofing into another bottle containing a folution of potafli; from 
it to the folar rays, or to a brifle heat; which proves that this lecond bottle goes another tube, which is plunged 
it is a triple lalt, containg oxyd of iron. into a third, containing a folution of fulphat of iron. 
Berthoiiet found no lenfible difference between the When the apparatus is well luted, pour in at the neck of 
Pruffiats of potafli and of foda, except that the lad; cryf- the firft bottle, iome nitric'acid at 30 0 . An effervelcence 
tallizes differently. Mineral acids difengage the Pruilic takes place, and nitrous gas is difengaged; this gas pafl'es 
acid, which is partly fixed in the Prulfian blue which pre- through the folution of potafli before it reaches the ful- 
cipitates. The Pruffiats of ammoniac, lime, barytes, See. phat of iron, a ready way to be afl'ured of the purity of 
are prepared in the fame manner. The folution of iron the nitrous gas. The nitrous gas loles entirely its elaftic 
by the Pruflic acid, forms Prufliat of iron. According to form, and there remains but a very fmall proportion of 
Prouft, there are two kinds of Prufliat of iron. One kind is it in the mixture. Azotic gas alfo is difengaged; and 
produced by mixing a folution of green fulphat or mu- the green colour of the folution of fulphat of iron changes 
riat of iron, with a faturated folution of prufliat of pot- to dark brown, without lofing its tranlparency, or giving 
afli. When the mixture is made, ftop the bottle, and a any depofit. Its fweet ferruginous tafte becomes ftyp- 
white depofit is obtained, which foon takes a flight tint tic, and very aftringent. Mixed with a ley of caultlc 
of green, occaficned either by the fmall quantity of air potafli, it precipitates a dark green oxyd-of iron, and ex- 
contained in the vefl'el, or by the red oxyd which is al- hales a very evident vapour of ammoniac. Mixed with 
ways prefent, more or lei's, in alkaline Pruffiats. Prouft concentrated fulphuric acid, it throws off white vapours, 
regards the whiteriefs as the natural colour of this pruf- . well known to be nitric acid. It tinges tiinfture of turn- 
fiat of iron : it is therefore ‘white Prufiat of iron. foie with a deep red. Hence it appears, that, in this ex- 
The author recommends to pour an excels of alkaline periment, ammoniac and nitric acid are produced. See 
Prufliat over the metallic fulphat, in order to decompofe further the fedtion upon nitrous gas, page 215. 
it entirely. After ftanding fome hours, this white Prufliat Sulphureous acid attacks iron; the colour of the fo- 
will be covered with a yellow liquid, which is a mixture lution is green, the tafte aftringent. By evaporation'and 
of Prufliat and fulphat with an alkaline bafe, holding in epoling, a fait is obtained, cryitallized in rhomboids. If 
folution a little of the white oxyd of iron. On opening-^a ftronger acid than the fuiphureons be added to the fo- 
the bottle, this laft abforbs oxygen from the atmofphere, lution, a brifk effervefcence takes place, and the fulphur 
takes a blue colour, becomes inlbluble, and fpreads on is precipitated. When iron is diffoived in the fulphu- 
the white Prufliat, which, feeling likewife the influence reous acid, there is neither a difengagement of gas, nor 
of the atmofpherical air, becomes blue, by degrees, from any precipitation. It appears that part of the fulphu- 
the furface to the. very bottom of the velfel; at laft the reous acid is decompoied, and the lulphur thence pro¬ 
whole is converted into blue Prufiat. The fame eft'eft ceeding remains in lolution in the fait thereby formed, 
w ill arife by putting the white precipitate on a filter, which is called fulphurattd fulphit of iron. 
The blue Prufliat may be again converted to white, by Iron ‘with •weak nitric 'acid. —If weak nitric acid be 
keeping it in a bottle with plates of iron and tin. In poured over iron in thin plates or chips, there is a flight 
this caie the addition of the metal difbxydates the iron, effervefcence; the folution is greenilh, fometimes brown, 
and converts it into a green oxyd. A folution of ful- By evaporation, a red oxyd of iron is precipitated, but 
phurated hydrogen gas, kept with blue Prufliat in a clofe it furnifhes no cryftals; the liquor takes the form of a 
bottle, decompol'es it, and turns it white. This Prufliat reddifn jelly, which is only in part foiuble in water, the 
has the fame properties as that formed immediately from other part precipitating. The concentrated nitric acid 
the green fulphat. The white Prufliat, treated in the fame attacks iron with violence; the oxyd of iron hereby 
manner, undergoes no change. The fulphuric and mu- formed is precipitated red by little and little, and but a 
riatic acids have no effeft upon the' white Prufliat. The fmall part of it remains in folution in the nitric acid, 
nitric acids, and the oxygenated muriatic acid, turn it Ammoniac is formed by the feparaticn of the hydrogen 
blue: this lajl lofes its fmell at the fame time. from the water, which is decompofed over the azot of 
Sulphat of iron decompofes nitre very readily: Take the nitric acid. This folution gives a magma fimilar to 
equal parts of nitrat of potafli, and fulphat of iron, (lightly that obtained by the weak acid. 
calcined red; put the mixture in a (tone retort, which If the nitrat of iron be kept heated, red vapours, in 
place in a reverberating furnace; adapt to the neck of large quantities, are difengaged, the magma becomes 
the retort a long-necked balloon, and to the lower ex- dry, and affords an oxyd of a brick-duit reel colour; 
tremity of that fix a tube, which is to be plunged into a this magma, by diftillation in a retort, affords a ftnall 
jar half filled with water. A quantity of nitric acid, very quantity of fuming nitrous acid, much nitrous gas, and 
red and fuming, is obtained ; the relidue, by lixiviation, azotic gas. Vital air cannot be obtained, becaufe the 
affords fulphat of potafli, fixed alkali, and a red oxyd of iron retains all the oxygen of the acid ; the oxyd which 
iron remains on the filter; but, if ftrongly calcined ful- remains after the diftillation of nitrat.of iron, is of a 
phat be made ufe of, together with nitre which has fuf- lively red, and may afford a good colour for painters, 
lered fufion, the produft obtained is very inconfiderable. The nitric folution of iron, however concentrated, does 
This produdf confifts of two liquors ; the one, of a dark not appear to afford a precipitate by the addition of dif- 
and almoft black colour, floats on the furface of the other, tilled water. Alkalis decompofe it with different pheno- 
which is red and ponderous ; for which reafon Baume toena, according to their nature. Cauftic potafli preci- 
confidered this liquor as a kind "of oil. There afterwards pitates it of a light brown colour; the mixture pafl'es 
paffes into the neck of the retort a white faline mafs, very quickly to a blackifli brown, and much deeper than 
which attradfs the humidity of the air, and is foiuble the colour of the firft folution. This phenomenon arifes 
with heat and great rapidity in water, emitting a ltrbng from the portion of the precipitate diffoived by the alkali, 
fmell of fpirit of nitre, and very red thick vapours: this though the quantity be very fmall. Carbonat of potafli 
folution, faturated with potafli, affords fulphat of pot- feparates a yellowifh oxyd, which quickly becomes of a 
afli; the white mafs therefore is merely fulphuric acid, beautiful orange red; if the mixture be agitated, an ef- 
rendered concrete by a portion of nitrous gas. fervefcence takes place, the precipitate is re-diffolved in 
a much 
