Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 14

[Ill.u.s.tration: FIG. 2.--IMPROVED BUNSEN BURNER.]

It is so contrived as to give a flame that is a very much better subst.i.tute for the flame of the blowpipe, than the ordinary Bunsen's burner, and may hence be employed for reducing, oxidising, fusing, and volatilising, as well as for the observation of coloured flames. Fig. 1 is a sheath which, by turning round, regulates the admission of air. When it is used the conical chimney, _d d d d_, is placed in _e e_; it is of a size sufficient to allow of the flame burning tranquilly. In fig. 1 the flame is represented of half its natural size. This flame it will be seen consists of three divisions, viz.--1, _a a a a_ the dark zone, which is composed of cold gas mixed with about 62 per cent. of air. 2, _a c a b_ the mantle formed by the burning mixture of gas and air. 3, _a b a_, the luminous tip of the dark cone, which only appears when the orifices for the air are partially closed. Reductions may be performed in this part of the flame.

Bunsen, however, divides the flame into six parts, to which he attributes as many functions. These six divisions of the flame he names as follows:--

1. _The base_ at a has a relatively low temperature, because the burning gas is here cooled by the constant current of fresh air, and also because the lamp itself conducts the heat away. This part of the flame serves for discovering the colours produced by readily volatile bodies, when less volatile matters which colour the flame are also present. At the relatively low temperature of this part of the flame, the former vaporises alone instantaneously, and the resulting colour imparted to the flame is for a moment visible unmixed with other colours.

2. _The Fusing Zone._ This lies at , at a distance from the bottom of somewhat more than one third of the height of the flame, equidistant from the outside and the inside of the mantle, which is broadest at this part.

This is the hottest part of the flame, viz., about 2300, and it therefore serves for testing substances, as to their fusibility, volatility, emission of light, and for all processes of fusion at a high temperature.

3. _The lower Oxidising Zone_ lies in the outer border of the fusing zone at ?, and is especially suitable for the oxidation of oxides dissolved in vitreous fluxes.

4. _The upper Oxidising Flame_ at e consists of the non-luminous tip of the flame. Its action is strongest when the air holes of the lamp are fully open. It is used for the roasting away of volatile products of oxidation, and generally for all processes of oxidation, when the highest temperature is not required.

5. _The lower Reducing Zone_ lies at d, in the inner border of the fusing zone next to the dark cone. The reducing gases are here mixed with oxygen, and, therefore, do not possess their full power, hence they are without action on many substances which are deoxidised in the upper reducing flame. This part of the flame is especially suited for reduction on charcoal or in vitreous fluxes.

6. _The upper Reducing Flame_ lies at ?, in the luminous tip of the dark inner cone, which, as already explained, may be produced by diminishing the supply of air. This part of the flame must not be allowed to get large enough to blacken a test tube filled with water and held in it. It contains no free oxygen, is rich in separated incandescent carbon, and therefore has a much stronger action than the lower reducing zone. It is used more particularly for the reduction of metals collected in the form of incrustations.

The subjoined is a drawing of the gauze burner, which is an open cylinder with wire gauze at the top.

[Ill.u.s.tration: Argand's lamp, with wire-gauze cap.]

When this is placed over the gas burner, a supply of air is drawn in at the bottom by the ascending current of gas, and the mixture burns above the gauze, with a very hot flame, quite free from smoke, the metallic meshes preventing the flame from pa.s.sing down to the gas below. See ILLUMINATION, FUEL, FURNACE, GAS, LABORATORY, &c.

=Lamp, Flame'less.= _Syn._ GLOW LAMP. A coil of fine platinum wire is slipped over the wick of a spirit lamp, the greater part being raised above the cotton; the lamp is supplied with ether or alcohol, lighted for a moment and then blown out. The coil continues to glow in the mixed atmosphere of air and combustible vapour, until the liquid in the lamp is exhausted.

=Lamp, Monochromat'ic.= A lamp fed with a mixture of a solution of common salt and spirit of wine. It gives a yellow light, and makes every object illuminated by it appear either yellow or black. The human features are changed in a remarkable degree; the countenance appearing truly ghastly and unearthly.

=Lamp, Safety.= _Syn._ MINER'S LAMP, DAVY, GEORDY. The safety lamp of Sir H. Davy and George Stephenson are similar in principle, and were independently invented about the same time. That of Sir H. Davy consists of a common oil lamp, surmounted with a cylinder of wire gauze, the apertures of which are not greater than the 1/20th of an inch square, and the wire of which it is made to the 1/40th to the 1/60th of an inch in diameter. (See _engr._) The fire-damp (carbonetted hydrogen) along with air pa.s.ses through the meshes into the interior of the gauze cylinder.

Here it ignites, but the flame which is produced by its combustion cannot explode a mixture of fire-damp and air by which the lamp may be surrounded. The flame is prevented from pa.s.sing to the exterior of the gauze by the cooling action of the metal of which it is constructed. When this lamp is taken into an explosive atmosphere, although the fire-damp may burn within the cage with such energy as sometimes to heat the metallic tissue to dull redness, the flame is not communicated to the mixture on the outside. These appearances are so remarkable, that the lamp becomes an admirable indicator of the state of the air in different parts of the mine, and if its admonitions are attended to, gives the miner time to withdraw before an explosion takes place.

[Ill.u.s.tration]

=Lamp, Telescope.= This ingenious contrivance, invented by Messrs Murray and Heath, is intended for microscopic illumination. It consists of three bra.s.s tubes, sliding one within the other, the oil vessel being contained in the inner tube. The height of the lamp is regulated to the greatest nicety by simply turning one tube in the other, interior spiral guides preventing all chance of slipping. The great advantage of this arrangement is absence of the stand and bar usually employed for raising and lowering the lamp, which enables it to be used on all sides, and to be brought much closer to the microscope than other lamps. See _engr._, below.

[Ill.u.s.tration]

=LAMP BLACK.= See BLACK PIGMENTS.

=LAMP'REY.= _Syn_. GREAT LAMPREY, SEAL. This fish is the _Petromizon marinus_ of Linnaeus. It generally quits the sea in the spring, for the purpose of sp.a.w.ning, and remains in our rivers for a few months. Its flesh is soft and glutinous, and though esteemed a delicacy, is extremely difficult of digestion, if not otherwise unwholesome. Potted lampreys are usually so highly seasoned as to become a dangerous article of food. Henry I is said to have lost his life from the effects of a surfeit of lampreys.

=LAUDANINE.= C_{20}H_{25}NO_{3}. An alkaloid obtained by Hesse from the aqueous extract of opium. It is h.o.m.ologous with morphine and codeine. It dissolves in strong sulphuric acid with a rose-red colour, in strong nitric acid with an orange red colour, and in ferric chloride with emerald green colour.

=LANTHA'NIUM.= La_{92}. A rare metal, discovered by Mosander, a.s.sociated with oxide of cerium. Oxide of lanthanium is a pale salmon-coloured powder, unaffected by ignition in open vessels. According to Zschiesche the atomic weight of lanthanium is 9018. See CERIUM.

=LANTHOPINE.= C_{23}H_{25}NO_{4}. A base obtained by Hesse in small quant.i.ty, a.s.sociated with other bases from the aqueous extract of opium.

It is h.o.m.ologous with papaverine. Strong nitric acid dissolves it, giving rise to an orange red colour. Strong sulphuric acid gives with it a faint violet colour.

=LA'PIS.= [L.] A stone. The term was much employed by the old chemists, and is still commonly applied to several preparations used in medicine.

=Lapis Causticus.= See POTa.s.sIUM.

=Lapis Divi'nus.= _Syn._ DIVINE STONE; LAPIS OPHTHALMICUS, L.; PIERRE DIVINE, Fr. _Prep._ 1. (Beer.) Verdigris, nitre, and alum, equal parts, melted together.

2. (P. Cod.) Alum, nitre, and blue vitriol, of each 3 oz.; camphor, 1 dr.; as last.

3. (Woolfuss.) Blue vitriol, nitre, alum, and camphor, equal parts, melted together, adding the camphor last. Astringent and detergent. 1 oz., dissolved in water, 1 pint, formed a once celebrated lotion. 1 dr. in water, 1 pint, is still used as a collyrium.

=Lapis Inferna'lis.= See NITRATE OF SILVER.

=Lapis Lazu'li.= See ULTRAMARINE.

=Lapis Lydius.= _Syn._ LYDIAN STONE. A siliceous slate, used as a touchstone by jewellers.

=Lapis Medicamento'sus.= _Syn._ MEDICINAL STONE; LAPIS MIRABILIS, L.

_Prep._ (Ph. L. 1746.) Alum, litharge, and Armenian bole, of each 6 oz.; colcothar of green vitriol, 3 oz.; vinegar, 4 fl. oz.; mix, and evaporate to dryness. Formerly used to make an astringent and detergent lotion:--1 oz. to water, 1 pint. Once a popular application to ulcers, and in other cases; now disused.

=Lapis Vulnerar'ius.= Very similar to LAPIS DIVINUS.

=LARCH BARK.= The inner bark of the _Larix Europa_, the common larch, has been lately introduced, under the form of a tincture, into the British Pharmacopia.

Dr Stenhouse obtained from the bark a peculiar volatile const.i.tuent, possessed of acid properties for which the name of lariximic acid has been proposed. The other trees of the pine family are deficient in this acid.

The young bark abounds most in it. Gum, starch, resin, and that variety of tannic acid, which forms olive green precipitates with the salts of iron, have also been found, in addition to other substances, in larch bark.

The inner bark, employed internally, has a special action on the mucous membranes, and acts as an astringent and mild stimulant. It is said to have been given with excellent results in haemoptysis, as well as in bronchitis attended with copious expectoration, and in diseases of the urinary pa.s.sages. Externally has been found serviceable in psoriasis, chronic eczema, and some other skin diseases. It is best to combine its extract or tincture with glycerin when it is to be used outwardly. See TINCTURE OF LARCH BARK.

=LARD.= _Syn._ HOG'S LARD, AXUNGE; ADEPS (Ph. L.), AXUNGIA (Ph. E.), A.

SUILLUS (Ph. D.), A. PORCI, A. PRaePARATUS (B. P.), L. The fat of the pig (_Sus scrofa_--Linn.) melted by a gentle heat, and strained through flannel or a hair sieve. The fat about the loins yields the whitest and hardest lard. "That which has been cured with chloride of sodium is not to be employed." (Ph. L.) "It is not to be used without being first carefully washed with water." (Ph. L. 1866.) Used chiefly to make ointments, and in cookery. See ADEPS.

=LARD'ING.= By many this is regarded as belonging to the higher style of cookery only, and too troublesome and extravagant to be adapted to the kitchens of the middle cla.s.ses and the poor. This, we are a.s.sured, is not the case. On the contrary, "it is an economical process, and will make lean meat go much farther than without it." The process of larding is as follows:--"Get what is called a larding needle, that is, a piece of steel from 6 to 9 inches long, pointed at one end, and having four slits at the other to hold a small strip of bacon when put between them. It will, perhaps, cost tenpence. Cut the bacon into pieces 2 or 3 inches long, and 1/4 to 1/2 an inch square; put each one after the other in the pin, insert it in the meat, and leave only about half an inch out; using 8 pieces to each pound." (Soyer.)

=LARK.= The _Alauda arvensis_ (SKYLARK) and the _Alauda cristata_ (FIELD-LARK), with several other species of the same genus, form a light and nutritious article of food, by many esteemed a delicacy. The last, according to Galen and Dioscorides, eaten either roasted or boiled, 'helps the colic.' The heart, applied to the thigh, was also regarded to possess the same virtue.

=LARYNGITIS.= Inflammation of the larynx, or upper part of the windpipe.

The symptoms that indicate this most dangerous malady are sore throat, accompanied with considerable pain in front of the throat, difficulty in breathing and swallowing, considerable hoa.r.s.eness, change or loss of voice, a sense of suffocation, fever, restlessness, flushing of the face, and an eager desire for fresh air. We have described the accompaniments of this dread disease, in order that any one seized with an attack may know its nature, and at once send for his medical attendant. Should circ.u.mstances prevent his doing so immediately, as many leeches as possible should be applied to the centre of the throat.

=LAUD'ANUM.= This name is now understood to denote, exclusively, the common tincture of opium of the Pharmacopia; but formerly the term was applied to several preparations of opium differing greatly from each other, both in their strength and mode of preparation. (See _below_.)

=Laudanum, Dutchman's.= From the flowers of bull's hoof or Dutchman's laudanum (_Pa.s.siflora merucuja_--Linn.) infused in rum. Narcotic. Used as a subst.i.tute for tincture of opium in the West Indies.

=Laudanum, Ford's.= This is merely the common tincture of opium aromatised with a little cloves and cinnamon.

=Laudanum, Houlton's.= _Prep_. From opium 2-1/2 oz.; distilled vinegar, 1-1/2 pint; digested together for a week, the filtered tincture gently evaporated nearly to dryness, and then redissolved in weak spirit (1 of rectified spirit to 7 of water), 1 quart.--_Dose_, 10 to 60 drops.

=Laudanum, Neumann's.= A fermented infusion of opium evaporated to the consistence of honey.

=Laudanum, Quince.= _Syn_. EXTRACTUM OPII CYDONIATUM, LAUDANUM CYDONIATUM, L. _Prep_. 1. Extract of opium made with quince juice; a few drops of the oils of cinnamon, cloves, and mace being added before the ma.s.s cools. Now seldom used.