Chapter II: REDUCTION OF SOLUTIONS:--The reduction of the solution to the proper (6)

One of the easiest means of employing pressure in filtration is to increase the height of the column of the filtering liquid. From the peculiar properties of fluids, by which they transmit pressure in an equal degree in all directions, this column need not be of equal diameter throughout, but may be conveniently contracted to the size of a small pipe, as in the accompanying engraving, which represents a small filter on this construction at work. (_a_) Is the funnel or reservoir of foul liquid; (_b_) a small pipe conveying the liquid to the filter; (_c c_) a chamber, of which the upper portion (_d_) is filled with the descending liquid, and the lower portion (_e_) with the filtering media; (_i i_) are screws by which the bottom plate is fastened on, which plate is removed to clean out or renew the filter. For use, the cocks (_k_) and (_l_) are closed, and the liquid poured into the funnel (_a_); the cock (_k_) is next opened, and, in a few minutes after, the cock (_l_), when an uninterrupted flow of filtered liquor will be obtained as long as any fluid remains in the funnel (_a_) and the tube (_b_). The length of the tube determines the degree of pressure. Care must be taken first to pass the foul liquid through a hair sieve, or some other strainer, to remove any substance that might choke up the pipe (_b_).

Another method of employing pressure in filtration is the withdrawal of the air from the receiving vessel, as in the vacuum filter, by which a pressure of about 14-1/2 lbs. to the square inch becomes exerted on the surface of the liquid by the atmosphere. The vacuum in the receiving vessel may be produced by the air-pump, by steam, or by the Bunsen or Sprengel pump.

A commoner method of applying pressure than either of those already mentioned is to condense the air over the surface of the liquid by means of a forcing-pump, or by steam.

On the small scale, pressure may be applied to filtration by means of a syphon, whose shorter leg has its mouth blown into the shape of a bell or funnel, over which filtering paper or fine calico may be stretched.

The application of pressure to filtration is not always advantageous, and beyond a certain limit is generally attended with inconvenience, if not with absolute disadvantage. It is found in practice that fluids under pressure take a longer period to run clear than without pressure, and that ruptures of the media more frequently take place in the former case, or with pressure, than in the latter. Great pressure is in no case advantageous.

The filters already noticed are those that act by the fluid descending through the media; but in some cases the reverse method is employed, and the liquid filters upwards, instead of downwards. These are called ascending filters, and are often preferable to those on the descending principle, because the suspended matters that require removal by filtration usually sink, and thus a portion escapes being forced into the pores of the filter. They are also more convenient when pressure is employed. The construction depends upon the same principles as the common filter, and merely requires that the feeding vessel should be higher than the upper surface of the filtering media. OILS are conveniently filtered in this way, because of their little specific gravity. By fixing a small filter on this principle into the head of a cask, and pouring in water through a funnel, whose neck reaches nearly to the bottom of the cask, the oil will float up and pass the filter, leaving the sediment behind. In cold weather hot water may be employed.

_a._ Cask of oil.
_b._ Stand.
_c._ Funnel for water.
_d._ Filter.]

In some cases the upward and downward systems of filtration are united in the same apparatus, and this plan is advantageous where the space for operating is limited. For this purpose it is merely necessary to connect the bottom of an ascending filter with the top of a descending one, or the reverse; the proper pressure being in either case applied.

=Filtration, the Laws of.= The 'Revue Universelle des Mines,' 1874, pp. 469, 551 contains a paper by M. Paul Havre recording his investigations on the rapidity of the filtration of water through sand, wool, &c., which resulted in ascertaining and measuring the influences which may modify the flow of water. In all cases of filtration, the influences which are exerted are:--the pressure and temperature of the water, the thickness of the filtering medium, compression in the case of fibrous filters, the size of the grains and their mixture in the case of a filtering medium analogous to sand. The influence of obstruction, due to the dirtiness of the filter, depends on circumstances too variable to be taken into account. The delivery of a filter per square mètre per 24 hours is equal to two cubic mètres multiplied by the pressure of water in mètres, divided by the thickness of the filtering medium in mètres. An application of this formula is made to existing filter beds, including those at Southwark and at the Chelsea waterworks.

The first experiments for ascertaining the influence of a head of water on the delivery led to the following results:--The delivery increases in a higher ratio than the square root of the pressure, due to the height (TORRECELLI'S LAW); the delivery increases in direct ratio to the height of the column of water above the filter, admitting a previous initial delivery, due solely to the pressure of water above the filter; the co-efficient of the increase of delivery is constant, and in this case of a filtering substance 8·662 inches (22 centimètres) thick, is equal to 0·106 pint (6 centilitres) for sand to 0·528 pint (30 centilitres) for compressed wool, and to 0·792 pints (45 centilitres) for wool only slightly compressed.

The subsequent experiments were made with graduated transparent cylinders, 3·28 feet (1 mètre) high, with the ends perfectly level, the filtering substances being kept in place by a thick double cloth tied tightly under the bottom of the tube. This apparatus presented no other obstacle to the running of the water than the layer of filtering substance; it permitted experiments to be made at all temperatures, and the thickness of the filtering medium to be measured exactly.

In these experiments sand is 'taken as the type of pulverulent substances,' but an unexpected difficulty was encountered in the settling or partial agglomeration of the large and small grains of the unsifted sand, thus diminishing the delivery of water to one half, one third, and ultimately to one fifth of its previous volume. This led to the adoption of sand--the grains of which were uniform in size, and to the discovery of the fact that, other tissues being equal, the resistance of filtration is constant when the sand is coarse, when the grains of fine sand are of nearly equal size, and when there is but little fine sand mixed with the coarse. From experiments in filtering through a layer of coarse sand approximately 4 inches (10 centimètres) thick, it was found that the higher the temperature the more rapid was the delivery, and by filtering through a layer of coarser sand 11·8 inches (30 centimètres) thick, the conclusion was arrived at that the temperature exerts an influence in proportion to the thickness of the layer.

See AIR-PUMP, BUNSEN'S WATER-AIR PUMP; CLARIFICATION; DEFECATION; FININGS, &c.

=FI'NINGS.= Substances used by publicans, brewers, wine merchants, &c., to clarify their liquors.

_Prep._ 1. (BREWER'S FININGS; COOPER'S F.) Isinglass (finely shredded), 1 lb., and sour beer or cider or vinegar, 3 or 4 pints, are macerated together, and more of the sour liquor added as the isinglass swells, until about a gallon has been used, agitation with a whisk or a small bundle of twigs being occasionally had recourse to, for the purpose of promoting the solution. As soon as the whole of the isinglass is dissolved, the mixture is reduced to the consistence of thin syrup, with weak mild beer, or cider, or any other liquid that the finings are intended for. The whole is next strained through a tammy cloth or a hair sieve, and at once reduced to a proper state of dilution, by the addition of more liquor. _Product_, 6-1/2 to 7 galls. "A pound of good isinglass will make about 12 galls. of finings." (Ure.) Used to clarify fermented liquors, especially beer. 1 to 1-1/2 pint is the usual dose for a barrel of ale or porter; and a quart for a hogshead of cider or wine.

2. (SPIRIT FININGS.)--_a._ Alum (ord. cryst.), 1 lb.; powder, and divide it into 12 equal portions, which are to be separately wrapped in blue paper, and marked No. 1. Next take of carbonate of soda (sesquicarbonate of the shops), 6 oz.; divide this as the last, wrap it in white paper, and mark each parcel No. 2. Keeps dry anywhere.

_b._ From alum, 1 lb.; salt of tartar (dry), 1/4 lb.; proceed as before. The white papers containing the salt of tartar must be kept in a dry, well-corked, wide-mouthed bottle or jar. Both of the last two are used to clarify gin and cordials. The contents of one of the blue papers are dissolved in about a pint of hot water, and the resulting solution is well 'rummaged up' with the liquor. A solution of the contents of one of the white papers, in about 1/2 pint of hot water, is then added, and the agitation continued for some minutes longer; after which the cask is 'bunged' close and the whole allowed to repose until the next day. This is sufficient for a barrel (say 30 to 36 galls.), but many persons use double the quantity. The effect is not only to clarify, but also to 'blanch' the liquor.

_Obs._ Good liquors, either fermented or spirituous, need no artificial 'fining,' as they always clarify themselves by repose. With those, however, which are out of 'condition,' or of inferior quality, it is often necessary, as, without such a proceeding, they remain unsaleable. This is particularly the case with malt liquor. "Attempts to clarify it in the cask seldom fail to do harm. The only thing that can be used with advantage for fining foul or muddy beer is isinglass." (Ure.) The disadvantages resulting from the artificial clarification of fermented liquors are--that they do not afterwards 'stand well on draught,' that much of the conservative astringent matter which they contain is precipitated with the 'finings,' that their piquancy and flavour is more or less diminished, and that they are more than usually liable to become flat and vapid, whether in cask or bottle. The larger the proportion of 'finings' used, the more marked are their injurious effects, and the shorter the interval which elapses before the accession of the several symptoms referred to. We have seen the most disastrous consequences follow the injudicious use of 'finings,' more especially in respect to those liquors in which a certain amount of piquancy, astringency, and briskness, is an essential condition. In one instance which came under our notice upwards of 30 barrels of 'underground' (a very strong old ale) was thus reduced in value to less than 1-3rd its original cost; and in another, a large bottled stock of the 'finest old Burton' was found to be utterly unsaleable. In both cases the 'spoiled liquor' was got rid of by mixing it in and selling it with 3d. and 4d. beer.

Liquors which 'refuse to fine' or become clear, when treated with 'finings' in the usual manner, are called 'stubborn' by coopers and cellarmen. See BREWING, GIN, MALT, LIQUORS, WINES, &c.

=FIRE.= The calamities resulting from this destructive agent are of such frequent occurrence, as to justly claim a notice of the subject here. The causes of fires are numerous, and of a varied character, and, in most instances, difficult to determine, because it is the interest of those concerned to suppress all evidence connected with the matter. Accident, that convenient word given to the imaginary hack to which so many fires are referred, if truthfully interpreted, will, in general, be found to be equivalent to carelessness, recklessness, or guilt. We believe that there are few fires which have happened that might not have been prevented by the exercise of common prudence, and that a vast number have been caused by direct negligence, arising from sheer laziness and indifference, to use no harsher terms. As familiar instances, may be mentioned--allowing sparks to fall on the ground and remain there without extinguishing them; carrying a naked candle into rooms containing inflammable substances; smoking carelessly and in dangerous places, as workshops, warehouses, on shipboard, &c.; keeping instantaneous light matches in improper places, and neglecting to pick up those that may happen to fall on the ground, &c. &c. The list might easily be extended, but we believe every reflecting reader can do so for himself. The great increase in the number of fires since the introduction of lucifer matches, and the almost general use of tobacco, cannot fail to have attracted the attention of every one. The danger of matches falling about might be avoided by the use of those which can only be ignited by rubbing them on the prepared surface of the box. These 'safety matches' are coming into general use, and must eventually supersede all the more dangerous kinds.

The late Mr Braidwood classes the causes of fires under the following heads:--1. Inattention in the use of fires and lights. 2. Improper construction of buildings, &c. 3. Furnaces or close fires, for heating buildings, or for mechanical purposes. 4. Spontaneous ignition. 5. Incendiarism.

Amongst many other causes of fire, too numerous to specify, may be noticed--incautiously approaching window- and bed-curtains with a candle or lamp, airing linen before the fire, allowing children to play with fire, women's dresses taking fire, and taking off the burning coals from a fire and laying them on the hearth. Another very common cause of fire is covering up a fire-place when not in use with wood, or paper and canvas, &c. The soot falls either from the flue itself or an adjoining one into the grate; a neighbouring chimney takes fire, a spark from this falls down the blocked-up flue, ignites the soot in the grate, which smoulders until the covering is burnt through, and thus sets the building on fire.

Another cause of fire, and one which cannot be too strongly condemned, is the dangerous practice of reading in bed by candle-light. A very serious annual loss of property is also caused by want of proper care in hanging up or removing the goods in linendrapers' shop windows when the gas is burning. Another frequent cause of fire is the employment of young children in lighting fires, from their propensity to play with flame.

The employment of close fires with brick flues is also a frequent source of danger. Frequently, from various causes, the furnace almost always cracks, thus giving egress to smoke and flame. When this occurs no time should be lost in thoroughly repairing the defect, or building a new furnace; merely plastering over the surface will be found an ineffective and dangerous remedy.

To guard against the dangers arising from the ignition of wearing apparel many methods have been suggested for rendering fabrics flame proof, all of them consisting in soaking the dress in a weak solution of a non-inflammable substance, such as chloride of zinc, alum, tungstate of sodium, sulphate of ammonia, &c. Of these alum has the advantage of greatly improving the appearance of the fabrics, especially if they be coloured.

Fire-guards, particularly where there are children, ought to be adopted much more generally than they appear to be.

_Prev._ This consists of the exercise of those ordinary precautions which the good sense of every careful and trustworthy man, be he taskmaster or servant, cannot fail to suggest. It would be useless to enumerate them.

Immediately on the fire being discovered, secure an alarm being given to the nearest of the fire escape stations, not delaying an instant; do not wait "to see if it is wanted." Life is more valuable than property, and events have often proved how fatal even a moment's hesitation is in sending for the fire-escape.[307]

[Footnote 307: 'Handbook for Emergencies,' Cassell.]

The late Mr Braidwood's advice was, "that if the fire appears at all serious, and there are fire-engines within a reasonable distance, that it is best to wait until they arrive; many buildings have been destroyed from opening doors, and trying to extinguish fires with insufficient means. If no engines are within reach it is advisable to keep a hand-pump. If that is not to be had, the next best thing is to collect as many buckets outside the room on fire as can be obtained, keeping the door shut; then to creep into the room on hands and knees (if the heat and smoke are considerable), and throw the water as nearly in the direction of the fire as possible, keeping the door shut while more water is being collected.

"The police of the metropolis understand shutting up fires so well, that they have in many instances kept fires two or three miles distant from the engine-stations, shut up till the fireman arrived in time to extinguish them."

Fires might often be readily extinguished when first discovered by the timely application of a few buckets of water. When an apartment is found to be on fire, the door, chimney, and windows should be immediately closed, if possible, and only opened for the purpose of projecting water on the flames. By this means the supply of air will be cut off, and rapid combustion prevented. The same applies to the lower doors and windows of a house (especially the shop window), which are often injudiciously kept open or removed, under the pretence of rendering assistance. The neglect of this precaution has often caused a mere smouldering fire, that might have been easily put out, to burst into an unextinguishable mass of flame.

It has been proposed at various times to make certain additions to the water used for the purpose of extinguishing fires, in order to render its action more certain and effective. It is found that sal ammoniac (5 oz. to the gall.) exerts this property in a remarkable degree. Several other articles, as common salt, pearlash, and kitchen soda, act in the same way, though less effectively. A few buckets of such water will speedily arrest the progress of a fire before it has much extended itself. Such a plan is easily applied, by adding the saline matter to the buckets of water, which are either used by hand, or to feed the engine for the first few minutes of its working. When, however, a fire has made much progress, the action of such substances becomes scarcely perceptible.

Chimneys on fire are readily extinguished in several ways, without having recourse to throwing water down them from the top, by which much damage is frequently done to the furniture in the rooms. One of the simplest methods is, to cautiously scatter a handful of flowers of sulphur over the dullest part of the burning coals; the sulphurous vapours, being incapable of supporting combustion, rapidly extinguish the flames. Another method is, to shut the doors and windows, and to stop up the bottom of the chimney with a piece of wet carpet or blanket, throwing a little water or flowers of sulphur, or even common salt, on the fire immediately before doing so. By this means the draught is stopped, and the burning soot extinguished for want of air. In many of the first-class houses recently erected, 'fire-place shutters' are provided, which, when partly drawn down, act as powerful bellows or 'blowers' and which, when wholly drawn down, so as to touch the hearth-stone, entirely close up the fireplace, and instantly extinguish the combustion of the fuel in the grate, or that of the soot in the chimney. This simple arrangement, the advantages of which were pointed out in an early edition of this work, renders fires in chimneys of little moment, as it is only necessary to draw down the shutter to put them out. If a chimney is stopped at top, instead of at the bottom, the whole of the smoke must, of necessity, be driven into the apartment.

In France, M. Marateuh has successfully applied the principle of Davy's safety lamp for the prevention of fires in chimneys. He places fire-frames of iron work near the base of the chimney, one above the other, about one foot apart; no flame passes through them, whilst the draught in the chimney is not interfered with, the result being that no fire can happen in the chimney.

Escape from apartments on fire may be best effected by creeping on the hands and knees. In this way the window or door may be reached. It is found that the atmosphere of a room so full of smoke as to produce suffocation to a person standing upright, may generally be safely breathed on nearly a level with the floor. A damp cloth, or handkerchief, tied over the mouth and nostrils, or, still better, over the whole face and head, will enable a person to effect a passage through the densest smoke, and, in many cases, to escape from buildings on fire, when otherwise it would be impracticable. Should descent by the staircase be found impossible, then the window should be immediately sought, and a ladder or fire-escape waited for. In the absence of either, if the danger is imminent, a rope should be made by tying the sheets and blankets of the bed together, one end of which should be firmly secured to a chair or table, or preferably to one of the bed-posts, and with this apparatus descent should be cautiously attempted. Jumping out of the window should be avoided, as persons who have not been brought up as clowns, or harlequins, run just as much danger in performing such an exploit as they do by remaining in the burning building. When it is impossible to escape from a burning building by the stairs or windows, retreat may be sometimes secured by a trap door opening on to the roof, or by a skylight, when, unless it be an isolated house, the roof of one of the adjoining buildings may probably be gained with safety.

Fire-escapes of various kinds have been employed of late years in the metropolis, and have proved of the greatest value in rescuing persons from burning buildings.

It is said that there is no instance on record of a person being burnt to death in a dwelling-house in Edinburgh, where the houses are usually high; yet in London, where fire-engines and fire-escapes are provided in greater numbers, deaths are very frequent from this cause. The reason of this difference is, that in the former city the stairs are all made of stone, by which means a road of escape is secured.

The clothes of females and children, when on fire, may be most readily extinguished by rolling the sufferer in the carpet, hearth-rug, table-cover, a great-coat, cloak, or any other woollen article at hand. If this be expertly done, the flames may be rapidly put out, unless the skirts of the dress be distended by hoops or crinoline, when there is great difficulty in staying the progress of the flames. Should assistance not be at hand, the person whose clothes are on fire should throw herself on the ground, and roll the carpet round her, as before described; or if such a thing is not in the room, she should endeavour to extinguish the flames with her hands, and by rapidly rolling over and over on the floor. In this way the fire will be stifled, or at least the combustion will proceed so slowly that less personal injury will be experienced before assistance arrives. The advantage of assuming the horizontal position is manifest from the fact that nine times out of ten it is the lower parts of the dresses of females that first catch fire.[308]

[Footnote 308: For the mode of rendering muslin and other inflammable articles of ladies' apparel fire-proof, see INCOMBUSTIBLE FABRICS.]

The extinction of fires on board ships by means of carbonic-acid gas was some years since suggested to the Admiralty by Mr J. R. Hancorn. He proposes that a simple and economical apparatus should be attached to every decked vessel capable of supplying this gas, which is a well-known non-supporter of combustion, and will extinguish fire at the very instant of coming in contact with the burning matter. Chalk with sulphuric acid diluted with water (vinegar with any other acid will do) yields 44% of the gas; hence, a ton of chalk, and a fourth part of that quantity of sulphuric acid, will be found sufficient to extinguish any fire on board a ship. Mr Hancorn also proposed this as a method of destroying vermin in ships, such as rats and cockroaches, for which purpose it is more easily applied and more effectual than that usually adopted. This plan was rejected by the Admiralty, from a fear that the destructive action of the gas might extend to the crew as well as the fire. But "it surely is possible by mechanical means to expel the gas before again entering the ship's hold. At any rate, the grand point would be obtained of extinguishing the fire, though the crew might have only the deck to stand on."

_Precautions to be taken against a Fire amongst Farming Stock._--The following are the suggestions of Mr Beaumont, the secretary of the County Fire Office:--

"Forbid your men to use lucifer matches, to smoke or light pipes or cigars, destroy wasp nests, or fire off guns in or near the rickyard, or to throw hot cinders into or against any wooden out-building on the farm, on pain of instant dismissal.

"Place your ricks in a single line, and as far distant from each other as you conveniently can. Place hayricks and cornstacks alternately; the hayrick will check the progress of the fire. Keep the rickyard, and especially the spaces between the stacks and ricks, clear of all loose straw, and in all respects in a neat and clean state. The loose straw is more frequently the means of firing than the stack itself. Have a pond close to the rickyard, although there may be a bad supply of water. When a steam thrashing machine is to be used, place it on the lee-side of the stack or barn, so that the wind may blow the sparks away from the stacks. Let the engine be placed as far from the machine as the length of the strap will allow. Have the loose straw continually cleared away from the engine; see that two or three pails of water are kept close to the ashpan, and that the pan itself is kept constantly full of water."

It is often difficult to get horses out of buildings on fire, but it is said that they will readily come out if, after being blindfolded, the saddle and bridle, or the harness, &c., to which they are accustomed, are thrown over them as usual.

We learn from the last report issued by Captain Shaw that the actual number of fires in the year 1877 in London was 1533. Of these fires 1374, or 90 per cent., were slight, no persons being endangered, and no considerable destruction of property taking place. The number of really serious conflagrations was 150; in 88 of these life was endangered, and in 24 cases there was loss of life. The actual number of persons whose lives were in danger was 165; but of these 136 were saved, and the lives eventually lost amounted only to 29. The smallness of the loss is due in great degree to the courage of the members of the Brigade, seven of whom have been commended for special efforts for saving life during the year. Even of the twenty-nine persons who perished fourteen were taken alive out of the burning buildings, and died in hospital of their wounds. It is very satisfactory in view of the vast height of buildings used in business, and the flimsy character of so many London houses, that the risk of death from fire should be so small. It is one of the very slightest risks to which we are exposed in modern London. The fire-escapes must of course be credited with much of this security. There are now 108 stations of these useful machines; and instances of their utility in rescuing the inmates of burning houses are constantly occurring.

The various tables which Captain Shaw appends to his report give some very curious details as to the character of London fires. The hours at which they most commonly break out are by no means those which are popularly supposed to be the most dangerous. No considerable proportion occur after people have gone to bed. From seven o'clock in the evening till eleven o'clock there are more alarms of fire than in an equal portion of the twenty-four hours. Not a third of the number which occur in these evening hours take place in the small hours of the morning, which are in fact less destructive than the same period in the afternoon. There are, moreover, in the detailed list of fires some curious statistics, illustrating the comparative security of private houses over places of business. A very large part of the half million houses in London must come under the description of private dwellings, yet the alarms of fire in this class of buildings were only 316 in the year, and only in five of those were there serious conflagrations. In the lists of business premises nearly every trade in the metropolis is mentioned; and next to houses let out in lodgings, public-houses seem to suffer most. The causes of fires tell the old story of carelessness. They were instances of the almost inconceivable folly of seeking for an escape of gas with a lighted candle. The throwing down of lights is responsible for a considerable number of fires. Ordinary cases of chimneys on fire are not included in Captain Shaw's summary; but they give the brigade a good deal of work. The number of calls of this kind was 3744, of which 1256 proved to be false alarms. The number of these false alarms will probably be reduced when the stations at which men with hose are situated are more numerous.

=Fire Anni'hilator (Phillips's).= This is essentially a gaseous fire engine, which at any moment can be made to discharge a stream of mixed gases and vapours having the power of checking combustion. When first introduced it was generally regarded as a most important invention, but it has not proved an effective substitute for the common water engine. For extinguishing fires on board ship and in close apartments it is undoubtedly well adapted, but as a street engine it is comparatively useless, owing to the unmanageable nature of its fire-annihilating vapours.

The composition with which the 'Fire Annihilator' is charged is a mixture of dried ferrocyanide of potassium, sugar, and chlorate of potassa. It is set in action by a blow on a glass vessel containing oil of vitriol, which, being fractured, permits the acid to flow over the 'charge,' when the anti-combustion gas is liberated, and rushes forth with great impetuosity.

=Fire-damp.= See HYDROGEN (Light Carburetted).

=Fire-engine.= The common fire-engine is a compound forcing-pump, consisting of two 'forcing-pumps' placed on opposite sides of an 'air-vessel,' with which both communicate. The 'fulcrum' of the 'lever' by which both pumps are worked is placed midway between them; consequently they act alternately in charging the air-vessel. In order to obtain a very forcible jet it is necessary to prevent the escape of any portion of the contents of the air-vessel until the confined air is considerably compressed. The lever is connected with handrails on each side of the engine, and these are alternately raised and depressed by the workers. Engines worked by steam power are now common in London and most of our large towns.

=Fire-Extinguishing Powder (Feuerloschpulver)=, Bucher Leipzig. Nitre, 59 parts; sulphur, 36 parts; coal, 4 parts; iron oxide, 1 part. (Wittstein.)

=Fire, how to light a.= In a close stove the first thing is to empty the fireplace. Take out the larger cinders and half-burnt coal with your fingers, and lay them on one side for lighting the fire; then rake out all the ashes (this can be done with the lids on, then it will not make so much dust). Next take off all the lids, and sweep all the soot carefully out; once or twice a week the flue pipe must be taken off and cleared out, also the flues under the oven. The soot should be carried away at once, as it blows about. Then blacklead the stove; put in a few cinders, lay on them a piece of paper and a few sticks crossing each other; on these lay very lightly some pieces of half-burnt coal and a few cinders, leaving space for the draught.

Do not fill the grate full; put the lids on, draw out the damper, light the fire, and shut the front door. An open fire is lighted in much the same way. There are no flues to clean out; but the chimney, as high as one can reach and behind the register door, should be cleared from soot daily.[309]

[Footnote 309: 'Household Management, &c.,' by W. T. Tegetmeier.]

=Fire-proofing.= See INCOMBUSTIBILITY, &c.

=Fireworks.= See PYROTECHNY, and _below_.

=FIRES.= (In pyrotechny.) Coloured fires may be termed, not inaptly, the _chefs-d'[oe]uvre_ of the pyrotechnist's art, since on their excellence the attractions of most other varieties of fireworks depend. The following forms, under judicious management, yield fires of remarkable beauty.

=Blue Fire.= _Prep._ 1. From metallic antimony, 1 part; sulphur, 2 parts; nitre, 5 parts.

2. From realgar, 2 parts; charcoal, 3 parts; chlorate of potassa, 5 parts; sulphur, 13 parts; nitrate of baryta, 77 parts.

3. (Mr A. Bird.) Charcoal and orpiment, of each 1 part; black sulphuret of antimony, 16 parts; nitre, 48 parts; sulphur, 64 parts.

4. (Fownes.) Tersulphuret of antimony, a part; sulphur, 2 parts; dry nitre, 6 parts. This is the composition used for the Bengal or blue signal light employed at sea.

5. (Prof. Marchand.) Sulphur, sulphate of potassa, and ammonio-sulphate of copper, of each 15 parts; nitre, 27 parts; chlorate of potassa, 28 parts. For theatrical illuminations. This may be rendered either lighter or darker coloured by lessening or increasing the quantities of the sulphate of potassa and ammonio-sulphate of copper.

6. (LIGHT BLUE--Marchand.) Sulphur, 16 parts; calcined alum, 23 parts; chlorate of potassa, 61 parts.

7. (DARK BLUE--Marchand.) Calcined alum and carbonate of copper, of each 12 parts; sulphur, 16 parts; chlorate of potassa, 60 parts.

8. (Marsh.) Sulphate of copper, 7 parts; sulphur, 24 parts; chlorate of potassa, 69 parts.

9. (Ruggieri.) Nitre, 2 parts; sulphur and zinc, of each 3 parts; gunpowder, 4 parts.

10. From sulphur, 1 part; dried verdigris, 2 parts; chlorate of potassa, 9 parts.

=Fire, Crimson.= _Prep._ 1. (Marsh.) Chlorate of potassa, 4-1/4 parts; charcoal (alder or willow), 5-3/4 parts; sulphur, 22-1/2 parts; nitrate of strontia, 67-1/2 parts. For pots.

2. (Marsh.) Charcoal, 4-1/4 parts; sulphuret of antimony, 5-1/2 parts; chlorate of potassa, 17-1/4 parts; sulphur, 18 parts; nitrate of strontia, 55 parts. For boxes and stars.

3. (Marchand.) Sulphur, 16 parts; chalk (dry), 23 parts; chlorate of potassa, 61 parts. Turns on the purple. See RED FIRE (_below_).

=Fire, Green.= _Prep._ 1. Nitrate of baryta, 77 parts; chlorate of potassa, 8 parts; fine charcoal, 3 parts; sulphur, 13 parts.

2. From metallic arsenic, 2 parts; charcoal, 3 parts; chlorate of potassa, 5 parts; sulphur, 13 parts; nitrate of baryta, 77 parts. Very beautiful, particularly when burnt before a reflector.

3. (Mr A. Bird.) Charcoal and black sulphuret of antimony, of each 2 parts; chlorate of potassa, 5 parts; sulphur, 6 parts; nitrate of baryta, 80 parts.

4. (Fownes.) Lampblack, 1 part; chlorate of potassa, 4 parts; sulphur, 6 parts; dry nitrate of baryta, 18 parts.

5. (Marchand.) Boracic acid, 10 parts; sulphur, 17 parts; chlorate of potassa, 73 parts. Very beautiful.

6. (Marchand.) Chlorate of potassa, 18 parts; sulphur, 22 parts; nitrate of baryta, 60 parts. For theatrical illuminations.

7. (LIGHT GREEN--Marchand.) Sulphur, 16 parts; carbonate of baryta, 24 parts; chlorate of potassa, 60 parts. Extremely delicate.

8. (Marsh.) Charcoal and sulphuret of arsenic, of each 1-3/4 parts; sulphur, 10-1/2 parts; chlorate of potassa, 23-1/4 parts; nitrate of baryta, 62-1/2 parts. For pots or stars.

=Fire, Lilac.= _Prep._ 1. (Marsh.) Black oxide of copper, 6 parts; dry chalk, 20 parts; sulphur, 25 parts; chlorate of potassa, 49 parts. For pans.

2. (Marsh.) From black oxide of copper, 3 parts; dried chalk, 22 parts; sulphur, 25 parts; chlorate of potassa, 50 parts. For stars.

=Fire, Orange.= See RED FIRE, No. 8 (_below_).

=Fire, Pink.= _Prep._ (Marchand.) Charcoal, 1 part; chalk and sulphur, of each 20 parts; chlorate of potassa, 27 parts; nitre, 32 parts. For theatrical illuminations. See RED FIRE, No. 10 (_below_).

=Fire, Purple.= _Prep._ 1. From lampblack, realgar, and nitre, of each 1 part; sulphur, 2 parts; chlorate of potassa, 5 parts; fused nitrate of strontia, 16 parts.

2. (Marsh.) Sulphuret of antimony, 2-3/4 parts; black oxide of copper, 10 parts; sulphur and nitrate of potassa, of each 22-3/4 parts; chlorate of potassa, 42 parts. For pans.

3. (Marsh.) Sulphate of copper, 9-3/4 parts; sulphur, 13 parts; chlorate of potassa, 77-1/4 parts. For stars.

4. From sulphur, 12 parts; black oxide of copper, 12 parts; chlorate of potassa, 30 parts. See CRIMSON FIRE, No. 3 (_above_), and RED FIRE, No. 9 (_below_).

=Fire, Red.= _Prep._ 1. From sulphur, sulphuret of antimony, and nitre, of each 1 part; dried nitrate of strontia, 5 parts.

2. (Mr A. Bird.) Charcoal, 1 part; black sulphuret of antimony, 4 parts; chlorate of potassa, 5 parts; sulphur, 13 parts; dried nitrate of strontia, 40 parts.

3. (Fownes.) Lampblack, 2 parts; chlorate of potassa, 8 parts; sulphur, 9 parts; dried nitrate of strontia, 32 parts.

4. (Marchand.) Sulphur, 16 parts; carbonate of strontia, 23 parts; chlorate of potassa, 61 parts.

5. (Marchand.) Chlorate of potassa, 20 parts; sulphur, 24 parts; nitrate of strontia, 56 parts. For theatrical illuminations.

6. (Marsh.) Coaldust, 2 parts; gunpowder, 6 parts; sulphur, 20 parts; dried nitrate of strontia, 72 parts.

7. (Ruggieri.) Sulphuret of antimony, 4 parts; chlorate of potassa, 5 parts; sulphur, 13 parts; fused nitrate of strontia, 40 parts. A little charcoal or lampblack makes it burn quicker.

8. (ORANGE RED--Marchand.) Sulphur, 14 parts; chalk, 34 parts; chlorate of potassa, 52 parts.

9. (PURPLE RED--Marchand.) Sulphur, 16 parts; chalk, 23 parts; chloride of potassa, 61 parts.

10. (ROSE-RED--Marchand.) Sulphur, 16 parts; dried chloride of calcium, 23 parts; chlorate of potassa, 61 parts. See PINK FIRE.

11. From charcoal, 2 parts; chlorate of potassa, 6 parts; sulphur, 13 parts; dried nitrate of strontia, 40 parts.

=Fire, Violet.= _Prep._ 1. From charcoal, 8 parts; sulphur, 10 parts; metallic copper, 15 parts; chlorate of potassa, 30 parts.

2. (DARK VIOLET--Marchand.) Alum and carbonate of potassa, of each 12 parts; sulphur, 16 parts; chlorate of potassa, 60 parts.

3. (PALE VIOLET--Marchand.) Sulphur, 14 parts; alum and carbonate of potassa, 16 parts; chlorate of potassa, 54 parts.

=Fire, White.= _Prep._ 1. From nitre, 60 parts; sulphur, 20 parts; black antimony, 10 parts; meal powder, 6 parts; powdered camphor, 4 parts. For either pans or stars.

2. (Mr A. Bird.) White arsenic, 1 part; charcoal, 2 parts; black antimony, 16 parts; nitre, 48 parts; sulphur, 64 parts.

3. (Marchand.) Charcoal, 2 parts; sulphur, 22 parts; nitre, 76 parts. For theatrical illuminations.

4. (Marchand.) Gunpowder, 15 parts; sulphur, 21 parts; nitre, 64 parts. As the last.

5. (Marsh.) Gunpowder, 12-1/2 parts; zinc filings, 18 parts; sulphur, 23 parts; nitre, 46-1/2 parts. For pans.

6. (Marsh.) Zinc dust or filings, 15 parts; sulphur, 28 parts; nitre, 57 parts. For stars.

7. (Ruggieri.) Sulphur, 13-1/4 parts; sulphuret of antimony, 17-1/4 parts; nitre, 48 parts.

8. (Ruggieri.) From realgar, 2 parts; sulphur, 7 parts; nitre, 24 parts.

9. (Ruggieri.) Charcoal, 1 part; sulphur, 24 parts; nitre, 75 parts.

10. (Ruggieri.) Iron or zinc borings, 25 parts; gunpowder, 100 parts.

=Fire, Yellow.= _Prep._ 1. From sulphur, 16 parts; dried carbonate of soda, 23 parts; chlorate of potassa, 61 parts.

2. (Marchand.) Gunpowder, 14 parts; sulphur, 16 parts; dried soda, 20 parts; nitre, 50 parts.

3. (Marchand.) Charcoal, 1-1/2 parts; sulphur, 17-1/2 parts; dried soda, 20 parts; nitre, 61 parts.

_Green-coloured Fires._[310]

------+----------------------+-----------------+--------------------
No. | Potassium Chlorate, | Barium Nitrate, | Sulphur, per cent.
| per cent. | per cent. |
------+----------------------+-----------------+--------------------
1 | 36 | 40 | 24
2 | 29 | 48 | 23
3 | 24 | 53 | 23
4 | 21 | 57 | 22
5 | 18 | 60 | 22
6 | 16 | 62 | 22
7 | 14 | 64 | 22
8 | 13 | 66 | 21
9 | 12 | 67 | 21
10 | 11 | 68 | 21
11 | 10 | 69 | 21
12 | 9·5 | 69·5 | 21
13 | 9 | 70 | 21
14 | 8·5 | 70·5 | 21
15 | 8 | 71 | 21
------+----------------------+-----------------+--------------------

[Footnote 310: Kern ('Chemical News,' September 29th, 1876).]

_Red-coloured Fires._

----+-------------------+------------------+---------+--------------
No.|Potassium Chlorate,|Strontium Nitrate,|Sulphur, |Carbon Powder,
| per cent. | per cent. |per cent.| per cent.
----+-------------------+------------------+---------+--------------
1 | 40 | 39 | 18 | 3
2 | 32 | 46 | 19 | 2
3 | 27 | 51 | 20 | 2
4 | 23 | 55 | 20 | 2
5 | 20 | 58 | 20·5 | 1·5
6 | 18 | 60 | 21 | 1
7 | 16 | 61·6 | 21·2 | 1·2
8 | 15 | 63 | 21 | 1
9 | 13 | 64 | 22 | 1
10 | 12 | 65 | 22 | 1
11 | 11 | 66 | 22 | 1
12 | 10 | 67 | 22 | 1
13 | 10 | 67·25 | 22 | 0·75
14 | 9·25 | 68 | 22 | 0·75
15 | 9 | 68·35 | 22 | 0·65
----+-------------------+------------------+---------+--------------

_Violet-coloured Fires._

----+-------------------+------------------+-------------------+---------
No.|Potassium Chlorate,|Calcium Carbonate,|Malachite powdered,|Sulphur,
| per cent. | per cent. | per cent. |per cent.
----+-------------------+------------------+-------------------+---------
1 | 52 | 29 | 4 | 15
2 | 52 | 28 | 5 | 15
3 | 52 | 26 | 7 | 15
4 | 52 | 24 | 9 | 15
5 | 52 | 23 | 10 | 15
6 | 52 | 21 | 13 | 15
7 | 51 | 20 | 14 | 15
8 | 51 | 18 | 16 | 15
9 | 51 | 16 | 18 | 15
10 | 51 | 15 | 19 | 15
11 | 51 | 13 | 21 | 15
12 | 51 | 11 | 23 | 15
13 | 51 | 10 | 24 | 15
14 | 51 | 8 | 26 | 15
15 | 51 | 6 | 28 | 15
----+-------------------+------------------+-------------------+---------

4. (Marsh.) Charcoal, 6 parts; sulphur, 19-1/2 parts. For pans. Very beautiful.

In preparing coloured fires for fireworks according to the usual formulæ given in manuals of pyrotechny, it is often important to know the speed at which they burn; as in some cases, such as decorations and lances, they should burn slowly; whereas in others, such as wheels, stars for rockets, and Roman candles, they ought to burn quicker. The foregoing tables are so arranged that every formula with a higher number yields a slower burning mixture than one with a lower number. Thus No. 5 burns quicker than No. 6, and slower than No. 4.

_Obs._ The ingredients in the above compounds are to be separately reduced to powder and sifted through lawn, after which they should be kept in well-corked wide-mouthed bottles until the time of mixing them for use. The chlorate of potassa, more especially, must be separately treated and cautiously handled, in order to prevent the possibility of explosion from friction whilst it is in contact with combustible matter. The requisite quantity of each of the ingredients being weighed out and placed on a clean sheet of white paper, the whole is to be thoroughly but carefully mixed together with a light hand, by means of a bone or wooden knife. The compound is next lightly packed into small cups or pans for illuminations, or into small pill-boxes for stars and trains, a little priming and quick-match being lastly attached to each. To ensure success the several ingredients must be dry and commercially pure; and though reduced to the state of a uniform powder, care must be taken that they are not absolutely 'dusty,' or too finely pulverised. The nitrate of strontia, alum, saltpetre, carbonate of soda, &c., before being weighed, require to be gently heated in an iron pot or pan until they fall to powder, and lose their hygrometric moisture, or water of crystallisation. To ensure the perfect admixture of the ingredients, the whole, after they have been stirred together on paper, as before directed, may be passed through a hair or perforated zinc or brass sieve. Further, as coloured fires rapidly deteriorate by keeping, and even sometimes inflame spontaneously, to prevent disappointment and accidents they should not be prepared long before they will be required for use, and should be stored in some situation in which their spontaneous combustion would be productive of no disastrous consequences.

Of the above formulæ, those bearing the name of the late Mr Marsh, of Woolwich, more especially deserve the attention of the pyrotechnist. To guard against the danger sometimes arising from the spontaneous combustion of coloured fires containing sulphur and chlorate of potash, Mr Saunders recommends intimately mixing 120 grains of bicarbonate of potash with each pound of sulphur before using it in the manufacture of any composition into which chlorates enter. See FLAME, PYROTECHNY, &c.

=FISH.= _Syn._ PISCES, L. Fishes form the _fourth class_ of vertebrate animals (VERTEBRATA) in the Cuvierian arrangement of the animal kingdom, and in the variety of their genera and species are second only to the INSECTA, whilst in prolificness and number they probably exceed all other animated beings that reach a size equal to that of even the smallest member of their prodigious race. Besides their value to man as food, they furnish him with oil, isinglass, and various other articles of utility and luxury, and provide, either directly or indirectly, an inexhaustible supply of manure for the fertilisation of his fields. As food fish are undoubtedly wholesome and nutritious, although less so than the flesh of animals or the grains of the cereals. Of all the various substances used as aliments by man, fish are, however, the most liable to run into a state of putrefaction, and should therefore be only eaten when perfectly fresh or, if not recently taken, then only when their perfect preservation has been ensured by any of the ordinary methods employed for the purpose. Those that are the whitest and most flaky when cooked, as cod, flounders, haddock, hake, soles, turbot, whiting, &c., are the most easily digested; and those abounding in oily matter, as eels, herrings, mackerel, salmon, &c., are most nutritious, though the most likely to offend the stomach. Salt-water fish have been said to be more wholesome than river fish, but without sufficient reason. Salted fish are hard of digestion, unless when carefully cooked and well masticated. Skin diseases are said to be more common among those who live continually on fish than among those who abstain from it; but this probably arises from their use being unaccompanied by a proper quantity of fresh vegetables or fruit, both of which are scarcer on the sea-coast than further inland. As one of the components of a mixed diet, the value of fish is indisputable. Acid sauces and pickles are the proper additions to fish, from their power of retarding the progress of putrefaction, and of correcting the relaxing tendency of large quantities of oil and butter.

_Artificial Propagation._ The fecundity of fish is positively marvellous. According to the recent observations of Mr Frank T. Buckland, salmon yield about 1000 ova or eggs to every lb. of their weight; a trout weighing 1 lb. produced upwards of 1000; a mackerel (1 lb.), 86,120; a herring (1/2 lb.), 19,840; a sole (1 lb.), 134,466; a turbot (8 lbs.), 385,200; and a cod (20 lbs.), 4,872,000. The ova here spoken of form what is commonly called the 'hard roe' of the female fish; the 'soft roe' is 'the milt' of the male fish. To protect the spawn, and the fry, when hatched, is the object of the art of fish culture, which has made great progress during late years. When the spawn is not artificially protected, the greater portion is always wasted, being swept away by the stream, and devoured by fish, birds, and insects. The natural enemies of the newly hatched fish are, again, so numerous, that it is really surprising that any should escape destruction. According to given data and accurate calculations of the returns of fisheries made by Messrs Ashworth and Buist, only one salmon egg out of every thousand deposited ever becomes a fish fit for human food. Other fish, both fresh and salt water, suffer in proportion. The hatching of fish by artificial means has been carried out on a large scale in France, and has been commenced in Scotland and Ireland, and on a small scale in England. The spawning fish, having been caught by a net, is made to deposit her eggs by gently pressing on the abdomen; these are impregnated by 'milt' expressed from the male fish in a similar manner, and mixed with them in a shallow tub or other vessel prepared for the purpose. The impregnated eggs are placed in long shallow boxes, bottomed with gravel and pebbles, and so arranged that a small stream of water from a reservoir may flow from one to another. The time of hatching depends entirely upon the temperature of the water; from 40° to 45° Fahr. seems to be the healthiest temperature. After about 50 days (in the case of salmon), when all goes well, the young fish makes its appearance as a misshapen creature about an inch long, with a bag containing the yolk of the egg attached to its abdomen. At 3 days old the fry is about 2 gr. in weight; at 16 months it has increased to 2 oz. To preserve the young fish in health, the boxes must be covered with shades of slate or zinc. The French fish-breeders generally feed the young fry with boiled frogs powdered fine. The Scotch give boiled liver. Mr Buckland prescribes a diet of roe of sole, or plaice, or whiting. As to the age at which it is advisable to turn the young fish out of the nursery, there is much difference of opinion. Some breeders recommend turning them out as soon as the 'umbilical bag' is absorbed; others think they should be taken care of till they are older and stronger, and better able to defend themselves or escape from attack. For full details respecting the artificial propagation of fish, the reader is referred to Mr Buckland's recent work, entitled 'Fish-Hatching.'

_Nutritive Value of Fish._--The white varieties of fish, such as _whiting_, _cod_, _haddock_, _sole_, _plaice_, _flounder_, and _turbot_, according to Letheby, contain only about twenty-two per cent. of solid matter, of which eighteen is nitrogenous. To increase their nutritive value, therefore, these fish should be eaten with butter.

According to the same authority _mackerel_, _eels_, and _salmon_ are richer in fat than the above kinds; mackerel containing about seven per cent., and salmon about six, whilst the oily matter of eels amount to nearly fourteen per cent. The same is the case with the _sprat_, the _herring_, and the _pilchard_, as well as with most of our fresh-water fish.

As regards _shell-fish_, all the different varieties of them afford about the same amount of nutrition. They contain about thirteen per cent. of solid matter, which in composition is similar to that of white fish. Shell-fish vary in digestibility; _mussels_, _limpets_, and _whelks_ being rather difficult of digestion, whilst _scallops_, _cockles_, _periwinkles_, _lobsters_, and _crabs_ are a trifle more easy of digestion, and _oysters_ still more so. All shell-fish are unsuited for delicate stomachs; although they are largely eaten by the poorer dwellers on the coast.

On the Continent, _vineyard snails_, and in China, _slugs_, are eaten, and are said to possess a delicate flavour and nutritive properties.[311]

[Footnote 311: Letheby.]