Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 291

It is often of the utmost importance to brewers, wine merchants, sugar refiners, druggists, &c., to be able to lessen the activity of the vinous fermentation, or to stop it altogether, or to prevent its accession to syrups and other saccharine and vegetable solutions. Whatever will still the motion of the molecules of the nitrogenous matter forming the ferment will render them inoperative as exciters of fermentation. Among the simplest means of effecting this object, and such as admit of easy practical application, may be mentioned exposure to either cold or heat.

At a temperature below about 50 Fahr., the acetous fermentation is suspended, and the alcoholic fermentation proceeds with diminished activity as the temperature falls, until at about 38 Fahr. it ceases altogether. In like manner, the rapid increase of the temperature of a fermenting liquid arrests its fermentation, and is preferable to the action of cold, as it is of easier application, and perfectly precipitates the ferment in an inert state. For this purpose a heat of about 180 Fahr.

is sufficient: but even that of boiling water may be employed with advantage. In practice fluids are commonly raised to their boiling point for this purpose, or they are submitted to the heat of a water bath (207-1/2 Fahr.). In this way the fermentation of syrups and vegetable solutions and juices is commonly arrested in the pharmaceutical laboratory.

Among substances that may be added to liquids to arrest fermentation the most active are--the volatile oil of mustard, coa.r.s.ely powdered mustard seed, or pure flour of mustard, sulphurous acid or the fumes of burning sulphur, sulphuric acid, sulphite of lime, tincture of catechu, strong spirit, strong acetic acid, chlorate of pota.s.sa, sugar of milk, bruised horseradish, garlic, and cloves, and their essential oils, and all the other volatile oils that contain sulphur, and most of the salts that readily part with their oxygen. These substances arrest fermentation by rendering the yeast inoperative, and they possess this power nearly in the order in which they stand above. In practice, mustard, the fumes of burning sulphur, sulphite of lime, and chlorate of pota.s.sa, are those most adapted for beer, cider, wines, syrups, &c.; but some of the others are occasionally used, though less active. For arresting or preventing the fermentation of the vegetable juices and solutions, and the medicated syrups employed in pharmacy, mustard seed, either alone or combined with a little bruised cloves, may be safely used, as the addition of acids or salts would lead to the decomposition of their active principles. For this reason such liquids should be kept in a sufficiently low temperature to prevent fermentation; and should they pa.s.s into that state it should be preferably arrested by the application of heat or cold, as above explained. Sugar of milk is also very effective for certain syrups, if not all of them.

To prevent, or rather to lessen, the production of fusel oil, it has been proposed to add a certain quant.i.ty of tartaric acid or bitartrate of pota.s.sa to the wort, or to arrest the fermentative process somewhat before the liquid has reached its utmost degree of attenuation. The best means of depriving the spirit of this and other substances of a similar nature is to largely dilute it with water, and to redistil it at a gentle heat.

Agitation with olive oil, decantation, dilution with a large quant.i.ty of water, and redistillation, have also been recommended. An excellent method is filtration through newly burnt and coa.r.s.ely powdered charcoal. This plan succeeds perfectly with moderately diluted spirit. On the Continent, the addition of about 10% of common vinegar, and a very little sulphuric acid, followed by agitation, repose for a few days, and redistillation is a favourite method. A solution of chloride of lime is also employed for the same purpose, and in the same way. In both these cases a species of ether is formed, which possesses a very agreeable odour. In the first, acetate of oxide of amyl (essence of jargonelle) is produced; and in the other, chloride of amyl, which also possesses a pleasant ethereal smell and taste. The affinity of the hydrated oxide of amyl (fusel oil) for acetic acid is so great, that they readily unite without the intervention of a mineral acid. (Doebereiner). Thus, the oil of vitriol mentioned above, though always used in practice, might be omitted without any disadvantage.

According to Messrs Bowerbank, the distillers quoted by Dr Pereira, 500 galls. of corn-spirit yield about one gall. of corn-spirit oil. See ACETIFICATION, ALCOHOL, BREWING, DISTILLATION, FERMENTATION, FUSEL OIL, SPIRIT, VINEGAR, VISCOUS FERMENTATION, YEAST, &c.

=VI'OLET.= _Syn._ PURPLE VIOLET, SWEET V.; VIOLA (Ph. L. & E.), L. "The recent petals of _Viola odorata_, Linn." (Ph. L.) It is chiefly used on account of its colour. See SYRUP.

=VIOLET DYE.= Violet, like purple, is produced by a mixture of red and blue colouring matter, applied either together or in succession. The 'aniline colours' are now almost exclusively used for obtaining violet on silk and wool (see ANILINE, PURPLE, and TAR COLOURS). With the old dye stuffs, violet may thus be obtained:--A good violet may be given to silk or wool by pa.s.sing it first through a solution of verdigris, then through a decoction of logwood, and, lastly, through alum water. A fast violet may be given by first dyeing the goods a crimson with cochineal, without alum or tartar, and, after rinsing, pa.s.sing them through the indigo vat.--Linens and cottons are first galled with about 18% of gall-nuts, next pa.s.sed through a mixed mordant of alum, iron liquor, and sulphate of copper, working them well, then through a madder bath made with an equal weight of root, and, lastly, brightened with soap or soda. Another good method is to pa.s.s cloth, previously dyed Turkey red, through the blue vat.

Wool, silk, cotton, or linen, mordanted with alum and dyed in a logwood bath, or a mixed bath of archil and Brazil, takes a pretty, but false, violet.

=VIS'COUS FERMENTATION.= _Syn._ MUCILAGINOUS FERMENTATION, MUCOUS F. The peculiar change by which sugar, in solution, is converted into gummy matters, and other products, instead of into alcohol.

When the expressed juice of the beet is exposed to a temperature of 90 to 100 Fahr., for a considerable time, the sugar it contains suffers this peculiar kind of fermentation. Gases are evolved which are rich in hydrogen, instead of being exclusively carbonic acid, and when the sugar has, for the most part, disappeared, mere traces of alcohol are found in the liquid, but, in place of that substance, a quant.i.ty of lactic acid, mannite, and a mucilaginous substance, resembling gum Arabic, and said to be identical with gum in composition. By boiling yeast or the gluten of wheat in water, dissolving sugar in the filtered solution, and exposing it to a tolerably high temperature, the viscous fermentation is set up, and a large quant.i.ty of the gummy principle generated, along with a ferment of a globular texture, like that of yeast, but which is capable of producing only the viscous fermentation, in saccharine solutions.

The peculiar cloudy, stringy, oily appearance of wine and beer, called by the French 'graisse,' and the English 'ropiness,' depends on the accession of the viscous fermentation. The mineral acids and astringent substances, especially the sulphuric and sulphurous acids, and tannin, precipitate the viscous ferment, and are, hence, the best cures for this malady of fermented liquors. It is the large amount of tannic acid in the red wines and well-hopped beer which is the cause of their never being attacked with 'graisse,' or 'ropiness.' See VINOUS FERMENTATION, WINES, &c.

=VI"SION.= The following means of preserving and restoring the sight may be appropriately inserted here:--

For NEAR-SIGHTEDNESS.--Close the eyes and press the fingers very gently, from the nose outward, across the eyes. This flattens the pupil, and thus lengthens or extends the angle of vision. This should be done several times a day, or at least always after was.h.i.+ng the face, until shortsightedness is overcome.

For LOSS OF SIGHT BY AGE, such as require magnifying gla.s.ses, pa.s.s the fingers or towel from the outer corners of the eyes inwardly, above and below the eyeb.a.l.l.s, pressing very gently against them. This rounds them up, and preserves or restores the sight.

It is said that many persons, by this last means, have preserved their sight so as to read fine print at 80 years of age; others, whose sight has been impaired by age, by carefully manipulating the eyes with their fingers, from their external angles inwardly, have restored their sight, and been able to dispense with gla.s.ses, and have since preserved it by a continuance of the practice. To be successful, or safe, these practices must be applied with great gentleness and caution. Many persons seriously damage their eyes by forcibly rubbing them when drowsy, especially on awaking in the morning.

The 'Lancet' remarks, that "there is good reason to believe that chicory (the coffee of the Londoners), from its narcotic character, exerts an injurious effect on the nervous system. So convinced of this is Professor Beer, of Vienna, a most celebrated German oculist, that he has enumerated chicoried coffee among the causes of amaurotic blindness."

To strengthen the eyes, to relieve them when swollen or congested, and to remove chronic ophthalmia, purulent discharges, &c., nothing is equal to frequently bathing them with water, at first tepid, but afterwards lowered in temperature to absolute coldness.

=VIT'RIOL.= A common name for sulphuric acid and for several of its salts.

(See _below_.)

=Vitriol, Blue.= _Syn._ ROMAN VITRIOL. Commercial sulphate of copper.

=Vitriol, Green.= Commercial sulphate of iron.

=Vitriol, White.= Commercial sulphate of zinc.

=VITTIE VAYR.= _Syn._ VETIVER. The Tamool name of the odorous and fibrous roots of the _Andropogon muricatus_ sold by the perfumers.

=VOLTA'IC ELECTRICITY.= _Syn._ GALVANIC E., GALVANISM, VOLTAISM. That branch of electrical science which has reference to the phenomena attendant on the development of electricity by chemical action.

Electricity thus developed may be made to show itself in the 'static'

condition, so as to produce the effects of frictional electricity, but it is much more easily obtained in the 'dynamic' condition--in other words, as a 'voltaic current'--when it is especially remarkable for its chemical and magnetic effects. If a plate of zinc and a plate of platinum be immersed in dilute sulphuric acid, and connected outside the liquid by a wire, a current of electricity will immediately be set up, and will continue as long as the conducting circuit is complete and the action of the acid on the zinc goes on. The current of 'positive' electricity pa.s.ses from the zinc, through the liquid, to the platinum, and thence through the wire to the zinc. The arrangement of two dissimilar metals immersed in a liquid which acts upon one of them is called a voltaic couple. By uniting a number of couples together in regular order, a voltaic pile or battery is formed.

The older forms of the voltaic battery, viz., VOLTA'S PILE, CRUIKSHANK'S TROUGH, and WOLLASTON'S BATTERY, are now but little used. They all consist of a series of couples of zinc and copper, excited by an acid liquid, generally a mixture of water with 1/40th of its bulk of sulphuric acid, and 1/60th of nitric acid.

[Ill.u.s.tration:

_A._ A copper cylinder, filled with a saturated solution of sulphate of copper.

_B._ A smaller porous cylinder (earthenware or membrane), containing a mixture of 1 measure of strong sulphuric acid, and about 8 measures of water.

_C._ A rod of amalgamated zinc, supported in the smaller cylinder by the cross-piece (_i_).

_D._ A shelf full of small holes, for supporting crystals of sulphate of copper, to keep up the strength of the solution.

_e_ and _f._ Screws and caps to connect the wires _g_ and _h_ with the battery.

_g._ The negative wire, connected with the zinc.

_h._ The positive wire, connected with the copper.]

One of the most useful forms of the voltaic battery is that proposed by the late Prof. Daniell, and commonly known by his name. Its peculiar advantages arise from its action continuing without interruption for a long time; hence the name of 'constant battery' that has been applied to it. The foregoing figure will explain the construction of each couple.

One of these couples is sufficient for electro-typing; six of them form a circle of considerable power, and about 20 produce one sufficiently strong for most experiments of demonstration and research.

In arranging these, as well as other batteries, when intensity, or travelling power, is desired, the metallic communication is made between the opposite metals (the zinc of one couple being united with the copper of another); but when simple quant.i.ty without intensity is required, the zinc of one battery is united with the zinc of the other, and the copper of the one with the copper of the other--an effect which is equally attainable with a single battery of enlarged dimensions.

Another useful apparatus is GROVE'S BATTERY, in which the positive metal consists of amalgamated zinc immersed in sulphuric acid, diluted with 10 times its bulk of water; and the negative metal of platinum immersed in strong nitric acid. The two liquids are kept separate by the use of porous vessels, as in 'Daniell's battery.' This is an extremely powerful arrangement, but not so constant as Daniell's, owing to the reduction of the nitric acid to lower oxides of nitrogen. After this battery has been in action for about an hour, copious red nitrous fumes are given off, which cause great annoyance.

In place of platinum, compact charcoal or c.o.ke, prepared by a rather troublesome process, may be used, and the arrangement then const.i.tutes a BUNSEN'S BATTERY. Other subst.i.tutes for the costly platinum have been proposed, as lead coated with gold or platinum, and iron rendered 'pa.s.sive' by immersion in strong nitric acid. Callan has obtained very good results with amalgamated zinc and cast iron immersed in diluted sulphuric acid, without the use of nitric acid (MAYNOOTH BATTERY).

In SMEE'S BATTERY, which is much used in the arts, pairs of amalgamated zinc and platinised silver (or platinised platinum) are immersed in dilute sulphuric acid (1 part acid to 7 parts water). The plates of zinc are usually bent double, and the platinised plates interposed between the two surfaces formed by the bend. See PLATINISING (p. 1337).

In every voltaic combination the pa.s.sage of the electricity (_i. e._ the positive modification of the force) in the liquid is from the active element to the inactive element; in the case of a simple zinc-and-copper couple, for instance, it is from the zinc to the copper. If this simple fact be borne in mind, it will decide in every case the question which confuses so many, namely, which is the positive, and which the negative end of a battery? The positive is the end where the electricity leaves the battery; the negative where it re-enters it. For further information connected with the subject of voltaic electricity, see articles on ELECTRICITY, ELECTROLYSIS, ELECTROTYPE, ETCHING, &c.

=VOLUME'TRIC a.n.a.lYSIS.= Quant.i.tative chemical a.n.a.lysis by measure. This method of a.n.a.lysis "consists in submitting the substance to be estimated to certain characteristic reactions, employing for such reactions liquids of known strength, and from the quant.i.ty of the liquid employed determining the weight of the substance to be estimated by means of the known laws of equivalence." As an example of this method we give the following from the Introduction in Mr Sutton's excellent 'Handbook of Volumetric a.n.a.lysis,'--"Suppose that it is desirable to know the quant.i.ty of pure silver contained in a s.h.i.+lling. The coin is first dissolved in nitric acid, by which means a bluish solution, containing silver, copper, and probably other metals, is obtained. It is a known fact that chlorine combines with silver in the presence of other metals to form chloride of silver, which is insoluble in nitric acid. The proportions in which the combination takes place are 3546, of chlorine to every 108 of silver; consequently, if a standard solution of pure chloride of sodium is prepared by dissolving 5846 grains of the salt (_i. e._ 1 equiv. sodium = 23, 1 eq. chlorine = 3546 = 1 eq. chloride of sodium 5846) in so much distilled water as will make up exactly 1000 grains by measure; every single grain of this solution will combine with 108 grain of pure silver to form chloride of silver, which precipitates to the bottom of the vessel in which the mixture is made. In the process of adding the salt solution to the silver, drop by drop, a point is at last reached when the precipitate ceases to form. Here the process must stop. On looking carefully at the graduated vessel from which the standard solution has been used, the operator sees at once the number of grains which have been necessary to produce the complete decomposition. For example, suppose the quant.i.ty used was 520 grains; all that is necessary to be done is to multiply 108 grain by 520, which shows the amount of pure silver present to be 5616 grains." The volumetric method is much less troublesome than the ordinary method of a.n.a.lysis (by separating the const.i.tuents of a mixture and weighing them), and is admirably adapted for the examination of substances used in arts and manufactures. Most of the processes described under ACIDIMETRY and ALKALIMETRY are examples of this method.

See those articles, also EQUIVALENTS, TEST SOLUTIONS, &c.

=WADE'S DROPS.= Compound tincture of benzoin.

=WA'FER PAPER.= See WAFERS, in Cookery (_below_).

=WA'FERS.= Thin adhesive discs, used for securing letters or sticking papers together.

_Prep._ 1. (WAFERS, FLOUR W.) The finest; wheaten flour is mixed with water, either pure or coloured, to a smooth pap or batter, which, after being pa.s.sed through a sieve, to remove clots or lumps, is poured into the 'wafer-irons' (previously warmed and greased with b.u.t.ter or olive oil), and in this state exposed to the heat of a clear charcoal fire; the whole is then allowed to cool, when the irons are opened, and the thin cake, which has become hard and brittle, is cut into wafers by mean of sharp annular steel punches made exclusively for the purpose.

2. (GELATINE WAFERS, TRANSPARENT W.) Good gelatine or glue is dissolved, by the heat of a water bath, in just sufficient water to form a consistent ma.s.s on cooling; it is then poured, whilst hot, upon the surface of a warm plate or mirror gla.s.s, slightly oiled, and surrounded with a border of card paper (laid flat); a similar plate, also warmed and oiled, is next laid upon the gelatine, and the two plates pressed into as close contact as is permitted by the card paper; when quite cold the thin sheet of gelatine is removed, and cut into wafers with punches, as before. 1 to 2 oz. of sugar is commonly added to each lb. of gelatine.

3. (MEDALLION WAFERS.) A sheet of metal or gla.s.s, having designs sunk in it corresponding to the raised part of seals, being provided, the hollows are filled up with a mixture formed of any appropriate coloured powder, made into a paste with gum water or size, leaving the flat part clear; melted coloured glue is then poured on the plate, and the process is otherwise conducted as before. For use, the paper is wetted where the wafer is to be applied.

_Obs._ Care must be taken that no poisonous colours be employed. For gelatine wafers, transparent colours only can be used. Those noticed under LIQUEURS and STAINS (Confectioner's) are appropriate. To these may be added plumbago, sesquioxide of iron (crocus martis), smalts, levigated vegetable charcoal, and vermilion.