VALONIA, is a kind of acorn, imported from the Levant and the Morea for
the use of tanners, as the husk or cup contains abundance of tannin. The
quantity imported for home consumption in 1836, was 80,511 cwts.; of
which Turkey furnished 58,724, Italy and the Italian islands, 7209.
VANADIUM, is a metal discovered by Sefström, in 1830, in a Swedish iron,
remarkable for its ductility, extracted from the iron mine of Jaberg,
not far from Jönköping. Its name is derived from Vanadis, a Scandinavian
idol. This metal has been found in the state of vanadic acid, in a lead
ore from Zimapan, in Mexico. The finery cinders of the Jaberg iron
contain more vanadium than the metal itself. It exists in it as vanadic
acid. For the reduction of this acid to vanadium, see Berzelius’s
_Traité de Chimie_, vol. iv. p. 644. Vanadium is white, and when its
surface is polished, it resembles silver or molybdenum more than any
other metal. It combines with oxygen into two oxides and an acid.
The vanadate of ammonia, mixed with infusion of nutgalls, forms a black
liquid, which is the best writing-ink hitherto known. The quantity of
the salt requisite is so small as to be of no importance when the
vanadium comes to be more extensively extracted. The writing is
perfectly black. The acids colour it blue, but do not remove it, as they
do tannate of iron: the alkalis, diluted so far as not to injure the
paper, do not dissolve it; and chlorine, which destroys the black
colour, does not, however, make the traces illegible, even when they are
subsequently washed with a stream of water. It is perfectly fluent, and,
being a chemical solution, stands in want of no viscid gum to suspend
the colour, like common ink. The influence of time upon it remains to be
tried.
VANILLA, is the oblong narrow pod of the _Epidendron vanilla_, Linn., of
the natural family _Orchideæ_, which grows in Mexico, Colombia, Peru,
and on the banks of the Oronoco.
The best comes from the forests round the village of Zentila, in the
intendancy of Oaxaca.
The vanilla plant is cultivated in Brazil, in the West Indies, and some
other tropical countries, but does not produce fruit of such a delicious
aroma as in Mexico. It clings like a parasite to the trunks of old
trees, and sucks the moisture which their bark derives from the lichens,
and other cryptogamia, but without drawing nourishment from the tree
itself, like the ivy and misletoe. The fruit is subcylindric, about 8
inches long, one-celled, siliquose, and pulpy within. It should be
gathered before it is fully ripe.
When about 12000 of these pods are collected, they are strung like a
garland by their lower end, as near as possible to the foot-stalk; the
whole are plunged for an instant in boiling water to blanch them; they
are then hung up in the open air, and exposed to the sun for a few
hours. Next day they are lightly smeared with oil, by means of a
feather, or the fingers; and are surrounded with oiled cotton, to
prevent the valves from opening. As they become dry, on inverting their
upper end, they discharge a viscid liquid from it, and they are pressed
at several times with oiled fingers to promote its flow. The dried pods
lose their appearance, grow brown, wrinkled, soft, and shrink into
one-fourth of their original size. In this state they are touched a
second time with oil, but very sparingly; because, with too much oil,
they would lose much of their delicious perfume. They are then packed
for the market, in small bundles of 50 or 100 in each, enclosed in lead
foil, or tight metallic cases. As it comes to us, vanilla is a capsular
fruit, of the thickness of a swan’s quill, straight, cylindrical, but
somewhat flattened, truncated at the top, thinned off at the ends,
glistening, wrinkled, furrowed lengthwise, flexible, from 5 to 10 inches
long, and of a reddish-brown colour. It contains a pulpy parenchyma,
soft, unctuous, very brown, in which are imbedded black, brilliant, very
small seeds. Its smell is ambrosiacal and aromatic; its taste hot, and
rather sweetish. These properties seem to depend upon an essential oil,
and also upon benzoic acid, which forms efflorescences upon the surface
of the fruit. The pulpy part possesses alone the aromatic quality; the
pericarpium has hardly any smell.
The kind most esteemed in France, is called _leq_ vanilla; it is about 6
inches long, from 1/4 to 1/3 of an inch broad, narrowed at the two ends,
and curved at the base; somewhat soft and viscid, of a dark-reddish
colour, and of a most delicious flavour, like that of balsam of Peru. It
is called vanilla _givrées_, when it is covered with efflorescences of
benzoic acid, after having been kept in a dry place, and in vessels not
hermetically closed.
The second sort, called _vanilla simarona_, or bastard, is a little
smaller than the preceding, of a less deep brown hue, drier, less
aromatic, destitute of efflorescence. It is said to be the produce of
the wild plant, and is brought from St. Domingo.
A third sort, which comes from Brazil, is the _vanillon_, or large
vanilla of the French market; the _vanilla pamprona_ or _bova_ of the
Spaniards. Its length is from 5 to 6 inches; its breadth from one-half
to three-quarters of an inch. It is brown, soft, viscid, almost always
open, of a strong smell, but less agreeable than the _leq_. It is
sometimes a little spoiled by an incipient fermentation. It is cured
with sugar, and enclosed in tin-plate boxes, which contain from 20 to 60
pods.
Vanilla, as an aromatic, is much sought after by makers of chocolate,
ices, and creams; by confectioners, perfumers, and liquorists, or
distillers. It is difficultly reduced to fine particles; but it may be
sufficiently attenuated by cutting it into small bits, and grinding
these along with sugar. The odorous principle can, for some purposes, be
extracted by alcohol. Their analysis by Bucholz is unsatisfactory, and
refers obviously to the coarsest sort. Berzelius says that the
efflorescences are not acid.
VAPOUR (_Vapeur_, Fr.; _Dampf_, Germ.); is the state of elastic or
aeriform fluidity into which any substance, naturally solid or liquid at
ordinary temperatures, may be converted by the agency of heat. See
EVAPORATION.
VARNISH. (_Vernis_, Fr.; _Firniss_, Germ.); is a solution of resinous
matter, which is spread over the surface of any body, in order to give
it a shining, transparent, and hard coat, capable of resisting, in a
greater or less degree, the influences of air and moisture. Such a coat
consists of the resinous parts of the solution, which remain in a thin
layer upon the surface, after the liquid solvent has either evaporated
away, or has dried up. When large quantities of spirit varnish are to be
made, a common still, mounted with its capital and worm, is the vessel
employed for containing the materials, and it is placed in a steam or
water bath. The capital should be provided with a stuffing-box, through
which a stirring-rod may pass down to the bottom of the still, with a
cross-piece at its lower end, and a handle or winch at its top. After
heating the bath till the alcohol boils and begins to distil, the heat
ought to be lowered, that the solution may continue to proceed in an
equable manner, with as little evaporation of spirit as possible. The
operation may be supposed to be complete when the rod can be easily
turned round. The varnish must be passed through a silk sieve of proper
fineness; then filtered through porous paper, or allowed to clear
leisurely in stone jars. The alcohol which has come over should be added
to the varnish, if the just proportions of the resins have been
introduced at first. The following are reckoned good French recipes for
varnishes:--
_White spirit varnish._--Sandarach, 250 parts; mastic in tears, 64;
elemi resin, 32; turpentine (Venice), 64; alcohol, of 85 per cent., 1000
parts by measure.
The turpentine is to be added after the resins are dissolved. This is a
brilliant varnish, but not so hard as to bear polishing.
_Varnish for the wood toys of Spa._--Tender copal, 75 parts; mastic,
12·5; Venice turpentine, 6·5; alcohol, of 95 per cent., 100 parts by
measure; water ounces, for example, if the other parts be taken in
ounces.
The alcohol must be first made to act upon the copal, with the aid of a
little oil of lavender or camphor, if thought fit; and the solution
being passed through a linen cloth, the mastic must be introduced. After
it is dissolved, the Venice turpentine, previously melted in a
water-bath, should be added; the lower the temperature at which these
operations are carried on, the more beautiful will the varnish be. This
varnish ought to be very white, very drying, and capable of being
smoothed with pumice-stone and polished.
_Varnish for certain parts of carriages._--Sandarach, 190 parts; pale
shellac, 95; rosin, 125; turpentine, 190; alcohol, at 85 per cent., 1000
parts by measure.
_Varnish for cabinet-makers._--Pale shellac, 750 parts; mastic, 64;
alcohol, of 90 per cent., 1000 parts by measure. The solution is made in
the cold, with the aid of frequent stirring. It is always muddy, and is
employed without being filtered.
With the same resins and proof spirit a varnish is made for the
bookbinders to do over their morocco leather.
_The varnish of Watin, for gilded articles._--Gum lac, in grain, 125
parts; gamboge, 125; dragon’s blood, 125; annotto, 125; saffron, 32.
Each resin must be dissolved in 1000 parts by measure, of alcohol of 90
per cent.; two separate tinctures must be made with the dragon’s blood
and annotto, in 1000 parts of such alcohol; and a proper proportion of
each should be added to the varnish, according to the shade of golden
colour wanted.
For fixing engravings or lithographs upon wood, a varnish called
_mordant_ is used in France, which differs from others chiefly in
containing more Venice turpentine, to make it sticky; it consists
of--sandarach, 250 parts; mastic in tears, 64; rosin, 125; Venice
turpentine, 250; alcohol, 1000 parts by measure.
_Copal varnish._--Hard copal, 300 parts; drying linseed or nut oil, from
125 to 250 parts; oil of turpentine, 500; these three substances are to
be put into three separate vessels; the copal is to be fused by a
somewhat sudden application of heat; the drying oil is to be heated to a
temperature a little under ebullition, and it is to be added by small
portions at a time to the melted copal. When this combination is made,
and the heat a little abated, the essence of turpentine, likewise
previously heated, is to be introduced by degrees: some of the volatile
oil will be dissipated at first; but more being added, the union will
take place. Great care must be taken to prevent the turpentine vapour
from catching fire, which might occasion serious accidents to the
operator. When the varnish is made, and has cooled down to about the
130th degree of Fahr., it may be strained through a filter, to separate
the impurities and undissolved copal.
Almost all varnish-makers think it indispensable to combine the drying
oil with the copal, before adding the oil of turpentine; but in this
they are mistaken. Boiling oil of turpentine combines very readily with
fused copal; and, in some cases, it would probably be preferable to
commence the operation with it, adding it in successive small
quantities. Indeed, the whitest copal varnish can be made only in this
way; for if the drying oil have been heated to nearly its boiling point,
it becomes coloured, and darkens the varnish.
This varnish improves in clearness by keeping. Its consistence may be
varied by varying the proportions of the ingredients, within moderate
limits. Good varnish, applied in summer, should become so dry in 24
hours that the dust will not stick to it, nor receive an impression from
the fingers. To render it sufficiently dry and hard for polishing, it
must be subjected for several days to the heat of a stove.
_Milk of wax_, is a valuable varnish, which may be prepared as
follows:--Melt in a porcelain capsule a certain quantity of white wax,
and add to it, while in fusion, an equal quantity of spirit of wine, of
sp. gr. 0·830; stir the mixture, and pour it upon a large porphyry slab.
The granular mass is to be converted into a paste by the muller, with
the addition, from time to time, of a little alcohol; and as soon as it
appears to be smooth and homogeneous, water is to be introduced in small
quantities successively, to the amount of four times the weight of the
wax. This emulsion is to be then passed through canvas, in order to
separate such particles as may be imperfectly incorporated.
The _milk of wax_, thus prepared, may be spread with a smooth brush upon
the surface of a painting, allowed to dry, and then fused by passing a
hot iron (salamander) over its surface. When cold, it is to be rubbed
with a linen cloth to bring out the lustre. It is to the unchangeable
quality of an encaustic of this nature, that the antient paintings upon
the walls of Herculaneum and Pompeii owe their freshness at the present
day.
The most recent practical account of the manufacture of varnishes, is
that communicated by Mr. J. Wilson Neil to the Society of Arts, and
published in the 49th volume of their “Transactions.”
The building or shed wherein varnish is made, ought to be quite detached
from any buildings whatever, to avoid accidents by fire. For general
purposes, a building about 18 feet by 16 is sufficiently large for
manufacturing 4000 gallons and upwards annually, provided there are
other convenient buildings for the purpose of holding the utensils, and
warehousing the necessary stock.
Procure a copper pan, made like a common washing-copper, which will
contain from fifty to eighty gallons, as occasion may require; when
wanted, set it upon the boiling furnace, and fill it up with linseed oil
within five inches of the brim. Kindle a fire in the furnace underneath,
and manage the fire so that the oil shall gradually, but slowly,
increase in heat for the first two hours; then increase the heat to a
gentle simmer; and if there is any scum on the surface, skim it off with
a copper ladle, and put the skimming away. Let the oil boil gently for
three hours longer; then introduce, by a little at a time, one quarter
of an ounce of the best calcined magnesia for every gallon of oil,
occasionally stirring the oil from the bottom. When the magnesia is all
in, let the oil boil rather smartly for one hour; it will then be
sufficient. Lay a cover over the oil, to keep out the dust while the
fire is withdrawn and extinguished by water; next uncover the oil, and
leave it till next morning; and then, while it is yet hot, ladle it into
the carrying-jack, or let it out through the pipe and cock; carry it
away, and deposit it in either a tin or leaden cistern, for wooden
vessels will not hold it; let it remain to settle for at least three
months. The magnesia will absorb all the acid and mucilage from the oil,
and fall to the bottom of the cistern, leaving the oil clear and
transparent, and fit for use. Recollect, when the oil is taken out, not
to disturb the bottoms, which are only fit for black paint.