754 FLU 
at the same time shows red spots, indicating 
copper. 
Zinc exposed to the blowpipe melts, takes 
fire, sending forth a beautiful blueish-green 
flame, which however is soon extinguished 
by a lanuginous calx; but if the reguline 
nucleus included in this lanuginous matter 
(commonly called flowers of zinc) is urged 
by the flame, it will be now and then inflam- 
ed, and, as it were, explode and fly about. 
With borax it froths, and at first tinges the 
flame. It continually diminishes, and the 
flux spreads upon the charcoal; but in fused 
microcosmic salt, it not only froths, but sends 
forth flashes with a crackling noise. Too 
great heat makes it explode with the emission 
of ignited particles. The white calx, or 
flowers, exposed to me flame on charcoal, 
becomes yellowish, and has a kind of splen- 
dour which vanishes when the flame ceases. 
It remains fixed, and cannot be melted. The 
fluxes are scarcely tinged, but when saturated 
by fusion, they grow opaque and white on cool- 
ing. Clouds are formed round the globules, 
of a nature similarto those of the metallic calx. 
Dissolved zinc is not precipitated by any 
other metal. When mineralized by carbonic 
acid gas, it has the same properties as calcin- 
ed zinc. In the pseudo-galena sulphur and 
iron are present. These generally, on the 
charcoal, smell of sulphur, melt, and tinge 
the flame more or less, depositing a cloud all 
around. Those which have no matrix are 
tinged by those which contain iron, apd ac- 
quire by saturation a white opaque colour. 
Verging to brown or black, according to the 
variety of composition. 
Regulus of antimony, fused and ignited on 
the charcoal, affords a beautiful object; for 
if the blast of air be suddenly stopped, a 
thick white smoke rises perpendicularly, 
while the lower part round the globule is con- 
densed into crystalline spiculx, similar to 
those called argentine flowers. The calx 
tinges fluxes of an hyacinth in e colour ; but on 
fusion smokes, and is easily dissipated, espe- 
cially on the charcoal, though it also depo- 
sits a cloud on it. The dissolved metal may 
be precipitated by iron and copper, but not 
by gold. Crude antimony liquefies on the 
charcoal, spreads, smokes, penetrates it, and 
at last disappears entirely, except a ring 
which it leaves behind. 
Regulus of manganese scarcely yields to 
the flame. The black calx tinges the fluxes 
of a blueish colour ; borax, unless saturated, 
communicates more of a yellow colour. The 
colour may be gradually dissolved altogether 
by the interior flame, and again reproduced 
by a small particle of nitre, or the exterior 
flame alone. Combined with carbonic acid, it 
is ©f a white colour, which changes by igni- 
tion to black. In other respects it shows the 
same experiments as the black calx. 
Fixed alkalis, nitre, borax, tartar, and 
common salt, are the saline matters of which 
fluxes are generally composed. But the 
word flux is more particularly applied to 
mixtures of different proportions of only 
nitre and tartar ; and these fluxes are called 
by particular names, according to the pro- 
portions of these ingredients, as in the fol- 
lowing instances. 
Flux, while, is made with equal parts of 
nitre and of tartar detonated together, by 
which they are alkalised. The residuum of 
FLU 
this detonation is an alkali composed of the j 
alkalis of the nitre and of the tartar, both 
which are absolutely of the same nature. As 
the proportion of nitre in this mixture is more 
than is sufficient to consume entirely all the 
inflammable matter of the tartar, the alkali 
remaining after the detonation is perfectly 
white, and is therefore called white flux ; and 
as this alkali is made very quickly, it is also 
called extemporaneous alkali. When a small 
quantity only of white flux is made, as a few 
ounces for instance, some nitre always re- 
mains undecomposed, and a little ot the 
acid of the tartar, which gives a red, 
or even a black colour, to some part of 
the flux ; but this does not happen when a 
large quantity of white flux is made, because 
then the heat is much greater. This small 
quantity of undecomposed nitre and tartar 
which remains in white flux is not hurtful in 
most of the metallic fusions in which this flux 
is employed; but if the flux is required per- 
fectly pure, it might easily be disengaged 
from those extraneous matters by a long and 
strong calcination, without fusion. 
Flux, crude . By crude flux is meant the 
mixture of nitre and tartar in any propor- 
tions, without detonation. Thus the mixture 
of equal parts of the two salts used in the pre- 
paration of the white flux, or the mixture of 
one part of nitre and two parts of tartar for 
the preparation of the black flux, are each of 
them a crude flux before detonation. It has 
also been called white flux, from its colour; 
but this might occasion it to be confound- 
ed with the white flux above described. The 
name, therefore, of crude flux is more con- 
venient. Crude flux is detonated and alka- 
lised during the reductions and fusions in 
which it is employed; and is then changed 
into white or black flux, according to the 
proportions of which it is composed. This 
detonation produces good eflects in these fu- 
sions and reductions, if the swelling and ex- 
travasation of the detonating matters are 
guarded against. Accordingly, crude flux 
may be employed successfully in many ope- 
rations; as, for instance, in the ordinary 
operation for procuring the regulus of anti- 
mony. 
Flux, black. Black flux is produced from 
the mixture of two parts of tartar and one 
part of nitre detonated together As the 
quantity of nitre which enters into the com- 
position of this flux is not sufficient to con- 
sume all the inflammable matter of the tar- 
tar, the alkali which remains after the deto- 
nation contains much black matter, of the 
nature of coal, and is therefore called black 
flux. This flux is designedly so prepared, 
that it shall contain a certain quantity of in- 
flammable matter; for it is thereby capable, 
not only of facilitating the fusion of metallic 
earths like the white flux, but also of reviv- 
ing these metals. From this property it is also 
called reducing flux ; the black flux, there- 
fore, or crude flux made with such propor- 
tions of the ingredients as to be convertible 
into black flux, ought always to be used when 
considered as metallic matters are at once to 
be fused and reduced. See Fusion. 
' FLUXION, in mathematics, denotes the 
velocity by which the fluents or flowing 
quantities, increase or decrease; and may be 
positive or negative, according as it relates to 
an increment or decrement. 
The doctrine of fluxions, first invented bv 
5 
FLU 
sir Isaac Newton, is of great use in the inves» 
tigation of curves, and in the discovery of the 
quadratures of curvilinear spaces, and their 
rectifications. In this method, magnitudes 
are conceived to be generated by motion, 
and the velocity of the generating motion is 
the fluxion of the magnitude. Thus, the 
velocity of the point that describes a line, is 
its fluxion, and measures its increase or de- 
crease. When the motion of this point is 
uniform, its fluxion or velocity is constant, 
and may be measured by the space described 
in a given time. But when the motion 
varies, the fluxion or velocity at any given 
point is measured by the space that would be 
described in a given time, if the motion was 
to be continued uniformly from that term. 
Thus let the point m be conceived to move 
A m m r 
from A, and generate the variable right line j 
Am, by a motion any how regulated; and let ; 
its velocity, when it arrives at any proposed 
position or point R, be such as would, was it j 
to continue uniform from that point, be suffi- 
cient to describe the line Rr, in the given , 
time allotted for the fluxion, then will R r be j 
the fluxion of the variable line Am, in the < 
term or point R. The fluxion of a plane ! 
surface is conceived in like manner, by sup- : 
posing a given right line mn (plate Miscel. j 
fig. 89) to move parallel to itself, in the plane 
ot the parallel and immoveable lines A F and ] 
B G ; for if, as above, Rr be taken to ex- j 
press the fluxion of the line A m, and the rec- 1 
tangle RrsS be completed; then that rec- 
tangle, being the space which would be uni- : 
formly described by the generating line m n, | 
in the time that Am would be uniformly in- 
creased by mr, is therefore the fluxion of the 
generated rectangle Bm, in that position. 
If the length of the generating line mn con- 1 
tinually varies, the fluxion of the area will 
still be expounded by a rectangle under that ] 
line, and the fluxion of he abciss or base ;l’or 
let the curvilinear space An m (fig. 90)be gen- 
erated by the continual and parallel motion of 
the variable line m n ; and let Rr be the : 
fluxion of the base or absciss Am, as before ; 
then the rectangle R r sS, will be the fluxion 
of the generated space A mn. Because, if the 
length and velocity of the generating line 
mn were to continue invariable from the po- 
sition R S, the rectangle R r s S would then be 
uniformly generated with the very velocity 
wherewith it begins to be generated, or with 
which the space Amn is increased in that 
position. 
Fluxions, Notation of. Invariable quantities, 
or those which neither increase nor decrease, 
are represented by the first letters of the alpha- 
bet, as a , b, c, d, &c. and the variable or flowing 
quantities by the last letters, as v, tv, x, y, z ; 
thus, the diameter of a given circle may be de- 
noted by a ; and the sine of any arch thereof,' 
considered as variable, by x. The fluxion of a 
quantity represented by a single letter, is ex- 
pressed by the same letter with a dot or full 
point over it : thus, the fluxion of x is repre- 
sented by x, and that of jy by y. And, because 
these fluxions are themselves often variable 
quantities, the velocities with which they either 
increase or decrease, are the fluxions of the 
former fluxions, which may be called second 
fluxions, and are denoted by the same letters 
with two dots over them, as x, j. In the same 
