A L K 
Jiffervefcence with acids is not, as was formerly hip¬ 
po fed, a diftin'guifhing: property ot alkalies; for this ef- 
fe£t is merely owing to the fixed air, to which they are 
united, during the procefs by which they are originally 
lornjed. The quantity of this air, however, is never fo 
great as to faturate them entirely ; on the contrary, their 
alkaline properties are always very perceptible, and they 
are commonly laid to be in a mild (late. But the truth 
is/ they are then in a kind of intermediate (late, between 
what may be called perfectly mild and perfeflly cauftic-. 
In their perfectly mild (late,' they are united with fu'ch a 
large quantity of fixed air as entirely overpowers their al¬ 
kaline properties ; and therefore they are no more intitled 
to the name of alkalies in this (late, than when combined 
■with the marine, nitrous, or any other, acid; in which cafe 
the compounds are called neutral falls. But it is a much 
more laborious and tedious procefs to faturate an alkali 
completely with fixed air than with any other acid; nor 
dbes it very eafily retain the ad rial acid after it has once been 
combined with it. Hence the cauftic tafte and properties 
of the alkali almoft always.predominate, and the fait con¬ 
tains a portion of pure and cauftic alkali, to which alone 
its virtues are to be aferibed. 
Vegetable alkali, when pure, and.containing about one- 
halt its weight of fixed air, is of a white colour when dry, 
and very cauftic to the tafte. It runs per deliquium when ex- 
pofed to the air ; and is ufually incapable of being cryftal- 
lize'd, though it acquires this property after being em¬ 
ployed in the rectification of ardent fpirit. After this al- 
kali has been once united with marine acid, it appears to 
have undergone fonte change; for the fait then produced, 
by combining it with the vitriolic acid, refembles Glau¬ 
bers fait almoft as much as it does vitriolated tartar. 
The foflil- alkali differs from the vegetable in having a 
fraaller attraction for acids, in being more eafily fufible 
,by itfelf, and forming a more foluble compound with the 
Vitriolic acid. It is alfo eafily cryftallizable, even with¬ 
out the addition of more fixed air than it naturally con¬ 
tains : and experience has determined it to be more proper 
for glafs-or foap manufactures than the vegetable alkali; 
for which reafon the demand for it is very confiderable. 
■ The'foil’ll alkali was anciently called natron or nitre, and 
Is fpoken of by Pliny and Tacitus as an ingredient in 
glafs, &c. The knowledge of this fait was loft in the ge- 
n’eral obfeuration of feienee which took place'on the de¬ 
cline of the Roman empire; nor do we find it mentioned 
till the time of the Hon. Robert Boyle; and even finee 
that time, though M. du Hamel gave an accurate ac¬ 
count of it in a memoir for the year 1736, little farther 
notice was taken of it till very lately, when the College 
of Phyficians of London reftored it to the Pharmacopoeia, 
calling the vegetable alkali, kali ; the folfil or mineral, 
natron ; and the volatile, ammonia. • • 
We are now certainly informed that the foffil alkali is 
found native in many parts of the world, which never is 
the cafe with the vegetable-alkali. The places -where it 
abounds mod are, Egypt, the country of Tripoli in- Bar- 
bary, the peak of Tenerifte, in one of the Canary iflands, 
Hungary, feveral of the provinces of Ruftia', fome parts 
■of Afia, particularly the neighbourhood of Smyrna, &c. 
though it has not hitherto been found in any of the weft- 
ern countries of Europe, excepting ini the neighbourhood 
ofvolcanoes; or in mineral waters ; -and in thefe lalt only 
in a very fmall quantity. 
The demand in this country for foffil alkali 1 , which is 
the natural bafts of fea-falt, is fitpplied from the allies of 
kali, and other fea-plants, from which it is feparated in 
•the fame manner as the vegetable alkali from the allies of 
■other plants. The pureft kind of allies containing this fait 
is rraWe&fcda or barilla, and is imported chiefly 1 from fo¬ 
reign countries; that which is obtained from the fea-weed 
growing on our own coalls,- is known by the name of help, 
but is exeeffively impure; a method/ however, has been 
lately difeovered, by Mr. Georg’e Hodfon, of Chefter, by 
which the foffil alkali-is feparated from the Jpuriatic-'acid 
Von. I. No. 23 . 
A L I, 
as it exifts in common fait, and as it exifts in kelp, for 
which lie obtained a patent in 1793. His method is ad 
follows.- Toextratl the alkali from common (alt, proceed 
thus : with a.ton of fait mix to the amount of fixteen buffi- 
els of charcoal, or rather fmall-coal; and, in this (late, 
throw it into a furnace for thepnrpofe of fufton. It muff 
be well ftirred, in order to effect; a proper union of the 
materials, and to expofe, by bringing.all the parts fuccei- 
(ively to the furfaee, the wliole mafs to the aCtion of the 
reverberating flame. After the fufion is completed, it is 
to remain one hour in the furnace, and then to be drawn 
out. The fubftance thus drawn is the afti, in its ini pure 
date; to refine it, nothing farther is requilite than to form 
a lixivium, and evaporate it to drynefs. 
Modern chemiftry has difeovered many acids, and has 
fucc.-eded in decompoling them into fimpler fubffances, 
ancl recotnpofing them. But the alkalies ffill remain in 
number only three ; and nothing has yet been effected to 
(hew an unequivocal decompofitionof the twofixed alkalies. 
To extraCt the alkali from the common fait as it reticles 
in kelp, a ton of kelp muff be broken into fmall lumps, 
and mixed with ten buftiels of charcoal, or fmall-coal, in- 
ffead of fixteen. In every other refpeCt the procefs cor- 
refponds \Vith the above defeription. The rationale is as 
as follows : The phlogiflon contained in tiie fmall-coal, or 
charcoal, being liberated by the fire, exerts its agency on 
the common fait, and effects a decompolition in it. The 
acid of .the fait, being feparated from its alkaline bafis, is- 
diffipated, and the alkali, left in conjunction with the reii- 
duumof the charcoal, or fmall-coal, forms the affies. 
A patent hath alfo been granted to Mr. Anthony Bour- 
boulon de Boneuil, of Liverpool, for an invention of an 
apparatus on a new conftruCtion, for the purpofe of .ma¬ 
king foffil alkali; by which.that very ufefui and important 
article is obtained of a quality equal to that extracted from 
the beft barilla,- We (hall give the particulars in the in T 
ventor’s own words. •“ Previous to fpecifying my appara¬ 
tus, I muff: obferve that, to extraCt foffil alkali from ma¬ 
rine fait, two thingsare .wanted: firff, the .materials con- 
taining the necelfary principles; feeoudly, a proper appa¬ 
ratus -for working them luccefltvely. As for materials, 1 
ufe charcoal and iron, mixed and melted , with Glauber’s 
fait, into which marine fait is at firff to be concerted, and 
of courfe I claim no grant on > that head. But I work 
thofe materials in a manner hithertounpraftifed, and ^ith 
an.apparatus entirely new. 
“ By this improved apparatus, inffead of keeping the 
mixture-of the materials in an open reverberatory furnace, 
expofed to the violencemf the fire, and the courfe of the 
air, I keep rhem in pots or crucibles made of iron, (land¬ 
ing upon a mere flat.furnace, 1’uch as are commonly ufed 
for diftillati.on, where their, necks are raffed a little above 
the furfaee of the furnace, ;and their mouths clofely (hut 
with lids. The empty places between each crucible are 
Unit on the furfaee of the filial ace with breaks, to prevent 
the fire from catching the materials, as the lids are intend¬ 
ed to prevent them from the cantaCL of sthe exterior air/ 
from thefe. two improvements it liappens, that the fulpluir 
formed at firff, by the mixture of the vitriolic acid lying 
in the Glaube-r’sfalt with the principle lying in the charcoal, 
meeting with iron on every fide, leaves the alkali and turns 
to iron ; by which itfis thus fo ftrongly kept, that a-mar,- 
ttal* pyrite is inftantly produced, and the foffil alkali re r 
■ mains free, and (lands by itfelf arnidft the pyrite. B,y 
former methods, the materials being worked in open re¬ 
verberatory furnaces, and being’-fo expofed both to the 
violence of the fire and the courfe of air, it happens, thqt 
the fire, acting immediately and on eyery fide upon tire 
materials, burns the fulpluir as foon as it is engendered, 
and confequently before it lias turned to iron; the vitrio¬ 
lic acid that becomes again free returns to the alkali, and 
re-produces Glauber’s fait. To extract the foflil alkali 
from the'martial pyrite, by my method, the matter js 
-poured from the iron crucibles into iron pans, and after¬ 
wards lpreadton -the ground, - where it is. left till the,mar r 
4 S tpl 
