=FLUID MAGNE'SIA.= _Syn._ LIQUOR MAGNESIae CARBONATIS, L. M. BICARBONATIS, L. The preparations sold under this name are mere solutions of freshly precipitated carbonate of magnesia in water, formed by means of carbonic acid gas, under powerful pressure, and long agitation. Those best known are Sir J. Murray's and Mr Dinneford's, each fl. oz. of which is said to contain about 17-1/2 gr. of the carbonate, but their actual richness in the latter seldom exceeds 10 or 12 gr., and by the time they reach the consumer is often as low as 5 or 6 gr. Recently precipitated carbonate of magnesia placed in a bottle or other suitable vessel, which is then filled by means of a soda-water apparatus with water fully charged with carbonic acid gas, readily dissolves on slight and cautious agitation, and the aerated water becomes saturated with magnesia. A scruple of carbonate of magnesia put into a soda-water bottle, and thus treated, is all taken up in from 20 minutes to half an hour, and the beverage continues beautifully clear.
=FLUID-OZON= (J. Krohn, Munich, with a certificate from Justus von Liebig). A mouth wash and toilet water. An aqueous solution of permanganate of soda, 1 in 9, contaminated with traces of sodium sulphate and chloride. (Wittstein.)
=FLUM'MERY.= A species of thick hasty-pudding made with oatmeal or rice, flavoured with milk, cream, almonds, orange flowers, lemons, &c., according to fancy.
_Prep._ 1. (DUTCH FLUMMERY.) From blancmange and eggs, flavoured with lemon peel and sweetened with sugar.
2. (FRENCH FLUMMERY.) From equal parts of blancmange and cream, sweetened, and flavoured. The above are poured into forms, and served cold, to eat with wine, spirit, cider, &c.
3. (A. T. Thomson.) Take oatmeal or groats, 1 quart; rub it for a considerable time with hot water, 2 quarts; and let the mixture stand until it becomes sour; then add another quart of hot water, and strain through a hair sieve. Let stand till a white sediment is deposited, decant the fluid portion, and wash the sediment with cold water. This is now to be boiled with fresh water, until it forms a mucilage, stirring the whole time. A light and nutritious food, during early convalescence.
=FLUOBORIC ACID.= _Syn._ BOROFLUORIC ACID. This may be easily prepared by saturating hydrofluoric acid with boracic acid, keeping the mixture cool, and then concentrating it in platinum vessels till dense fumes arise.
=FLUOHYDRIC ACID.= See FLUORIDE OF HYDROGEN.
=FLU'ORIDE OF HYDROGEN.= HF. _Syn._ FLUOHYDRIC ACID; HYDROFLUORIC ACID; A.
HYDROFLUORICUM, L. An acid composed of hydrogen and fluorine. It was discovered by Scheele, but was first obtained in a pure state by Gay-Lussac and Thenard, in 1810.
_Prep._ Pour concentrated sulphuric acid on half its weight of fluor spar, carefully separated from siliceous earth, and reduced to fine powder. The mixture must be made in a capacious leaden retort, and a gentle heat only applied, and the evolved gas must be collected in a leaden receiver, surrounded by ice.
_Prop., &c._ A colourless fluid below 59 Fahr., which speedily evaporates in dense white fumes when exposed to the air. Its affinity for water exceeds that of sulphuric acid, and its combination with that fluid is accompanied with a hissing noise, and a considerable increase of its sp.
gr. up to a certain point. It attacks glass and silica, for which reason it cannot be preserved in glass vessels. Bottles of lead, silver, platinum, or pure gutta percha, are used to keep it in. It is highly corrosive, instantaneously destroying the skin on contact, and producing deep and serious ulcerations; its vapour is pungent, irritating, irrespirable, and poisonous. With the bases it unites to form FLUORIDES.
In the arts, hydrofluoric acid is used for etching on glass.
=FLU'ORIDES.= Compounds of fluorine with metals and other basic radicals.
The fluorides of the metals are, with the exception of those of the alkaline metals, insoluble in water, while the fluorides of hydrogen, boron, and silicon, are gaseous, condensing at a low temperature to volatile liquids.
=FLU'ORINE.= F. _Syn._ FLUORINIUM, L. An element that has not yet been isolated, owing to its attacking and combining with every element or compound that at present has been exposed to it, except oxygen. It is presumably gaseous, and of a pale greenish-yellow colour.
=FLU'OSILICIC ACID.= _Syn._ FLUORIDE OF SILICON AND HYDROGEN; HYDROFLUOSILIC ACID. _Prep._ From powdered fluor spar, and siliceous sand or powdered glass, of each 1 part; concentrated sulphuric acid, 2 parts: mix in a glass retort, apply a gentle heat, and pass the evolved gas into water through a layer of mercury. Decomposition ensues, silica being deposited in a gelatinous state, and hydrofluosilicic acid or fluosilic acid remains in solution. The acid liquor is used as a test for potassium and barium, with whose salts it yields nearly insoluble precipitates.
=FLUX.= _Syn._ FLUXUS, FLUOR, L. In _medicine_, a term formerly applied to several diseases attended with a copious discharge, as diarrha (FLUX), dysentery (BLOODY FLUX), English cholera (BILIOUS FLUX), fluor albus (WHITE FLUX), &c. These terms are still current among the vulgar.
=Flux.= In metallurgy, &c., a term applied to various substances of easy fusibility, which are added to others which are more refractory, to promote their fusion.
_Prep._ 1. (BLACK FLUX.) Nitre, 1 part; crude tartar or cream of tartar, 2 parts; mix, and deflagrate, by small quantities at a time, in a crucible, heated to dull redness. The product consists of carbonate of potassa, mixed with charcoal in a finely divided state. Used for smelting metallic ores. It exercises a reducing action, as well as promotes the fusion. It must be kept in a dry corked bottle.
2. (CHRISTISON'S FLUX.) Carbonate of soda (cryst.), 8 parts; charcoal (in fine powder), 1 part; heat the mixture gradually to redness. For reducing arsenic.
3. (CORNISH REDUCING FLUX.) Crude tartar, 10 parts; nitre, 4 parts; borax, 3 parts; triturate together.
4. (CORNISH REFINING FLUX, WHITE FLUX.) Crude tartar and nitre, equal parts, deflagrated together. See BLACK FLUX.
5. (CRUDE FLUX.) Same as BLACK FLUX, omitting the deflagration. Reducing.
6. (FRESENIUS'S FLUX.) Carbonate of potassa (dry), 3 parts; cyanide of potassium, 1 part. For the arsenical compounds.
7. (LIEBIG'S FLUX.) Carbonate of soda (dry) and cyanide of potassium, equal parts. As the last. See ARSENIOUS ACID.
8. (MORVEAU'S REDUCING FLUX.) Powdered glass (free from lead), 8 parts; calcined borax and charcoal, of each, 1 part; all in fine powder, and triturated well together. Used as BLACK FLUX.
9. (WHITE FLUX.) See _above_.
10. (FLUXES FOR ENAMELS.) See ENAMELS.
11. (Various.) Borax, tartar, nitre, sal-ammoniac, common salt, limestone, glass, fluor spar, and several other substances, are used as fluxes in _metallurgy_.
_Obs._ On the large scale, crude tartar is employed in the preparation of fluxes; on the small scale, commercial cream of tartar or bitartrate of potassa.
=FLY.= The common house-fly (_Musca domestica_) causes considerable annoyance to the person in hot weather, as well as damage to handsome furniture, especially to picture frames, gilding, and the like. The best way to exterminate them is to expose on a plate one or other of the mixtures given under FLY POISON (_below_). The blow-fly (_Musca vomitoria_), and other insects, may be kept from attacking meat by dusting it over with black pepper, powdered ginger, or any other spice, or by skewering a piece of paper to it on which a drop or two of creasote has been poured. The spices may be readily washed off with water before dressing the meat.
It is a fact not generally known, that flies will not pass through a netting made of fine silk, thread, or wire, even though the meshes may be an inch apart, unless there is a window or light behind it. This affords us a ready means of excluding these insects from all our apartments which have windows only on one side of them, without keeping the latter closed.
It is merely necessary to have an ornamental netting stretched across the opening, when, although flies may abound on the outside, none will venture into the room so protected. If, however, there is a window on the other side of the room, they will fly through the netting immediately. See _below_.
=Fly-blow in Sheep.= Oil of turpentine, 3 oz.; oil of amber, 1 oz.; corrosive sublimate, 1 dr. The sublimate must be first dissolved in a pint of whey, and then mixed with the oils.
=Fly Papers.= Those papers which, a few years ago, were sold about the streets of London by harsh-voiced cries of "Catch 'em alive-oh!" and which might be seen in many shop-windows covered with dead and dying flies, were prepared by rubbing factitious birdlime over sheets of paper. It would be difficult to conceive a more cruel or more offensive mode of catching flies than that of glueing their living bodies to an adhesive surface. A preferable kind of fly-paper is that called 'PAPIER MOURE,' which contains a large quantity of arsenic in its substance.[317] This paper is kept wet when in use, and the flies, by sipping the moisture, are poisoned.
[Footnote 317: Mr Plowman, in a letter to the 'Pharm. Journ.,' June 22nd, 1878, says that in a specimen of "Papier Moure" examined by him he failed to detect the least trace of arsenic.]
=Fly Poison.= _Prep._ 1. A strong solution of white arsenic (say 1 dr. to the pint), sweetened with moist sugar, treacle, or honey. Sold under the name of 'FLY WATER,'
2. Treacle, honey, or moist sugar, mixed with about 1/12th their weight of King's yellow or orpiment.
_Obs._ Both the above are dangerous preparations, and should never be employed where there are children.
3. (Redwood.) Quassia chips (small), 1/4 oz.; water, 1 pint; boil 10 minutes, strain, and add of treacle, 4 oz. "Flies will drink this with avidity, and are soon destroyed by it."
4. Black pepper, 1 teaspoonful; brown sugar, 2 teaspoonfuls; cream, 4 teaspoonfuls. See _below_.
=Fly Powder.= The dark grey-coloured powder (so-called 'sub-oxide') obtained by the free exposure of metallic arsenic to the air. Mixed with sweets, it is used to kill flies.
=Fly Water.= See FLY POISON (_above_).
=FOG.= The influence of very intense foggy weather upon the death-rate is well illustrated by a reference to the Registrar-General's returns for 1873. From the 8th to the 12th of December of that year an unprecedently thick fog prevailed in London. The mortality in the metropolis for the week ending December 6th was twenty-three persons per thousand; in the week following, during which the fog occurred, the death-rate rose to twenty-seven; and in the week after that, when the full effects of the fog could be estimated, the deaths were found to be thirty-eight in the thousand. In the same periods the deaths from phthisis and diseases of the respiratory organs were respectively 520, 764, and 1112. That this increased death-rate was not the result of the inclement weather by which the fog was accompanied is evidenced by the circumstance that in large provincial towns, where the weather was equally severe, but in which no fog occurred, the increase in the mortality, when compared to London, was slight.
The mean of the deaths registered in London, in the two weeks ending December 20th, showed an increase of 41 per cent. upon the number returned in the first week of the month; whilst during the same date the deaths in seventeen large English towns were only 8 per cent. This fatal fog occurred during the London cattle-show week, and killed a great number of the animals sent for exhibition.
In a specimen of the air of Manchester, obtained during the visitation of that city by a very dense fog, Dr Angus Smith discovered it contained a diminished amount of oxygen when compared with a favorable sample of air.
=FOILS.= These are thin leaves of polished metal, placed under precious stones and pastes, to heighten their brilliancy, or to vary the effect.
Foils were formerly made of copper, tinned copper, tin, and silvered copper, but the last is the one wholly used for superior work at the present day.
Foils are of two descriptions:--white, for diamonds and mock diamonds, and--coloured, for the coloured gems. The latter are prepared by varnishing or lacquering the former. By their judicious use the colour of a stone may often be modified and improved. Thus, by placing a yellow foil under a green stone that turns too much on the blue, or a red one under a stone turning too much on the crimson, the hues will be brightened and enriched in proportion.
_Prep._ 1. (CRYSTAL, DIAMOND, or WHITE FOIL.)--_a._ This is made by coating a plate of copper with a layer of silver, and then rolling it into sheets in the flatting mill. The foil is then highly polished, or covered with crystal varnish.
_b._ The inside of the socket in which the stone or paste is to be set is covered with tin foil, by means of a little stiff gum or size; when dry, the surface is polished and the socket heated, and whilst it is warm, filled with quicksilver; after repose for two or three minutes the fluid metal is poured out, and the stone gently fitted in its place; lastly, the work is well fitted round the stone, to prevent the alloy being shaken out.