Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 17

=LEAD, GRANULATED.= _Prep._ By melting new lead, and pouring it in a small stream from an iron ladle with a hole drilled in its bottom, into a pail of water. Used to make solutions and alloys.

=LEAD, RED.= See RED PIGMENTS.

=LEAD, WHITE.= See WHITE PIGMENT.

=LEAD PYROPH'ORUS.= See PYROPHORUS.

=LEATH'ER.= _Syn._ CORIUM, CORIUS, L. Leather is the skin of animals which has been prepared by one or other of several processes adopted for the purpose, having the common object of preventing its spontaneous destruction by putrefaction, besides other objects, which are more or less peculiar to each variety of this useful substance.

Leather is only prepared on the large scale, and primarily either by the process of 'TANNING' or 'TAWING,' in the manner briefly described under these heads.

CURRIED LEATHER is leather which has been tanned, and sold to the currier, who, after soaking it in water, and rubbing it to soften it, pares it even with a broad, sharp knife, rubs it with a piece of polished stone or wood, and, whilst still wet, besmears it with oil or grease (DUBBING), which gradually penetrates the leather as the moisture evaporates. It next undergoes the operation of 'waxing,' which consists of first rubbing it on the flesh side with a mixture of oil and lamp black; it is then 'black-sized' with a brush or sponge, and, when dry, is lastly 'tallowed'

with a proper cloth, and 'slicked' upon the flesh side with a broad and polished lump of gla.s.s. Leather curried on the hair or grain side, termed 'black on the grain,' is blackened by wetting it with iron liquor, and rubbing it with an iron 'slicker' before applying the oil or grease. The grain is finally raised by the 'pommel' or 'graining board' pa.s.sed over it in various directions.

Leather is dyed or stained by the application, with an ordinary brush, of any of the strong liquid dyes, in the cold or only gently heated, to the surface of the skin previously stretched on a board. The surface, when dry, is commonly finished off with white of egg and the pommel or smoothing stick. Bookbinders generally employ copperas water as a black stain or sprinkle; a solution of indigo as a blue one; and a solution of salt of tartar or common soda, as a brown one.

Leather, before being j.a.panned or varnished, as in the preparation of what is called 'ENAMELLED' and 'PATENT LEATHER,' is carefully freed from grease by the application of absorbent substances or hard pressure between rollers, and the surface is nicely shaved, smoothed, and polished by appropriate tools, the varnish is then applied to the grain side for the former, and the flesh side of the skin for the latter, which is previously stretched out tight on a board to receive it. The whole is, lastly, submitted to a gentle stove-heat to harden the varnish; and the process is repeated, if necessary.

_Uses, &c._ These are well known, and are all but universal. The leather manufacture of Great Britain is equal in importance and utility to any other department of our industry, and inferior in point of value and extent only to those of cotton, wool, and iron. "If we look abroad on the instruments of husbandry, on the implements used in most of the mechanic trades, on the structure of a mult.i.tude of engines and machines; or if we contemplate at home the necessary parts of our clothing--breeches, shoes, boots, gloves--or the furniture of our houses, the books on our shelves, the harness of our horses, or even the substance of our carriages; what do we see but instances of human industry exerted upon leather? What an apt.i.tude has this single material in a variety of circ.u.mstances for the relief of our necessities, and supplying conveniences in every state and stage of life! Without it, or even without it in the plenty we have it, to what difficulties should we be exposed?" (Dr Campbell.) Leather is a kind of natural felt, but of much closer and firmer texture than that of artificial origin. "The thinner and softer kinds of leather are sometimes used as body-clothing; but its special and proper purpose is the manufacture of coverings for the feet, to protect them from cold and water." (Eras. Wilson.) See j.a.pANNING, VARNISH, &c.

=Leather, destruction of, by Gas.= It is well-known that the binding of books suffer considerable damage, when the books are kept in apartments lighted by coal gas. That the cause of this deterioration is due, as was believed, to the combustion of the bisulphide of carbon contained in the gas, and its consequent oxidation into sulphuric acid, is exemplified by the following interesting communication from Professor Church, published in the 'Chemical News' for October 19th, 1877. He says:--"Vellum seems unaffected; morocco suffers least; calf is much injured, and russia still more so. The disintegration is most rapid with books on the upper shelves of a library, whither the heated products of combustion ascend, and where they are absorbed and condensed.

By comparing specimens of old leather, with specimens of new, it is quite clear that the destructive influence of gas is due mainly to its sulphur.

True there are traces of sulphates in the dye and size of new leather bindings, but the quant.i.ty is insignificant and there is practically no free sulphuric acid. That leather may be destroyed by the oil of vitriol produced by the burning of gas in a library is proved by the following observations and a.n.a.lyses.

The librarian of one of our public libraries forwarded to me the backs of several volumes, which had been 'shed' by the books on the upper shelves in an apartment lighted by gas. The leather of one of these backs (a volume of the 'Archaeologia') was carefully sc.r.a.ped off so as to avoid any paper or size from underneath. This task of sc.r.a.ping was easy enough, for the leather was reduced to the consistency of Scotch snuff. On a.n.a.lysis of the watery extract of this leather, the following figures were obtained:--

Free sulphuric acid in decayed leather 621 per cent.

Combined 221 "

---- 842

=LEAV'EN.= Dough which has become sour or run into a state of incipient putrefaction. When a small quant.i.ty of it is added to recent dough, it excites fermentation, but is apt to produce a disagreeable taste and odour in the bread. It is now superseded by yeast. Both these substances are used in the same way.

=LEAVES (Medicated).= _Syn._ FOLIA MEDICATA, L. On the Continent several preparations of this kind are in use. In many cases the leaves of tobacco deprived of nicotine, by soaking them in water, are dried, and then moistened or steeped in a tincture or infusion of the medicinal substance.

In this way belladonna, camphor, and henbane, are often administered.

Cruveilhier recommends opiated belladonna leaves for smoking in troublesome coughs, phthisis, spasmodic asthmas, &c., to be prepared as follows:--Belladonna leaves, 1 oz., are steeped in an infusion of opium, 10 gr., in water, 1 fl. oz. (or less), and are then carefully dried in the shade. "MUSTARD LEAVES (Riggollot's) consist of mustard moistened with water, spread on paper, and dried." (Squire.) See CIGARS (in _pharmacy_), and VEGETABLES.

=Leaves, How to Dissect.= "For the dissection of leaves," says Mrs Cussons, "I find the process of maceration too long and tedious, to say nothing of the uncertainty as to the results. I have therefore adopted the use of alkali in saturated solution, the specimens to be introduced while the liquid is heated to the boiling point; the time of immersion to be regulated by the character of the various leaves and the nature of the epidermis to be removed. When the specimen is freed from epidermis and cellular tissue, it must be subjected to the action of chlorine to destroy the colouring matter. The introduction of peroxide of hydrogen not only serves to render the lace-like specimen purer in colour, but also preserves it. In destroying the colouring matter in ferns this also is invaluable; added to the chlorine it gives a solidity to the bleached fronds, and appears to equalise the action of the chlorine. For skeletonising capsules the slow process of maceration by steeping in rain-water is alone available; a moderate heat may be applied to hasten the process, but alkali is useless. The only known flower which can be dissected is the _Hydrangea j.a.ponica_. The fibrous nature of the petals renders it easy to skeletonise in the perfect truss in which it grows.

Skeletonised leaves and capsules appear to gain in the process a toughness and durability not possessed by them in their natural state."

=LECANOR'IC ACID.= See ORSELLINIC ACID.

=LEECH.= _Syn._ HIRUDO (B. P., Ph. L. & D.), L. The officinal leech of the Pharmacopias is the _Sanguisuga medicinalis_ (_Hirudo medicinalis_--Cuv.), familiarly known as the 'old English' or 'speckled leech.' It is also occasionally called the 'Hamburg grey' or 'Russian leech,' from being imported from those parts. Its characteristics are--Back, greenish or olive green, sometimes almost black or intense brown, with 6 rusty-red or yellowish longitudinal stripes, which are mostly spotted with black.--Belly, dirty yellow or light olive green, spotted more or less with black. The spots are very variable in size and number; in some cases few, in others so numerous as to form the prevailing tint of the belly. This variety, which is the most valuable of the commercial leeches, is chiefly imported from Hamburg.

Another variety of leech, the _Sanguisuga officinalis_, familiarly known as the 'Hamburg' or 'French green leech,' is imported from Bordeaux, Lisbon, and Hamburg. Its characteristics are--Back, brownish olive-green, with 6 reddish or rusty yellow longitudinal bands.--Belly, light dirty pea-green, or yellowish green, free from spots, but exhibiting two lateral stripes. This leech is vastly inferior to the preceding variety, and some of those imported from France and Portugal are absolutely useless, from their indisposition to bite, arising from the fraud practised by the collectors and dealers of gorging them with blood to improve their appearance before sending them to market. The above are the species of leech commonly employed in medicine in this country, but many others are noticed by writers on the subject.

Leeches are best preserved in water obtained from a pond, and occasionally changed; when kept in spring water they soon die. The introduction of a hand to which an ill-flavoured medicine or odour adheres into the water in which they are kept is often sufficient to poison them. The application of saline matter to the skin of leeches, even in very small quant.i.ties, immediately occasions the expulsion of the contents of the stomach; hence a few grains of common salt are frequently sprinkled over them, to make them disgorge the blood which they have swallowed. The frequent changing of the water in which leeches are kept is injudicious. Once a month in winter, and once a week in summer, is deemed sufficiently often by the large dealers, unless the water becomes discoloured or b.l.o.o.d.y, when it should be changed every day, or every other day. When clean pond water cannot be obtained, clean rain water that has been well exposed to the air should alone be employed. Mr J. R. Kenworthy recommends placing in the water a few b.a.l.l.s of irregular lumps of pure clay, about 2-1/2 inches in diameter; a method which we can recommend as both simple and successful.

The plan adopted by M. Fee is as follows:--Place 7 inches of a mixture of moss, turf, and charcoal, in a marble or stone trough, over which sprinkle some small pebbles. At one end of the trough, and about half way up, place a thin shelf of stone or marble, pierced with small holes, on which put first some moss, or portions of marsh horse-tail (_Equisetum pal.u.s.tre_), and on this a layer of pebbles to keep it down; then pour in water sufficiently high just to moisten the moss and pebbles, put in the leeches, and tie over the mouth of the trough with a cloth. Another plan consists in keeping the leeches in a gla.s.s tank, or aquarium, provided with a pebbly bottom and a few healthy aquatic plants.

_Propag._ According to Dr Wagner, an annual feast on living blood is necessary to render leeches able to grow and propagate. These conditions can only be fulfilled by restoring to the breeding cisterns those which have been already employed. All artificial methods of feeding them by bladders or sponges of blood have been found to fail. He recommends the employment of two tanks, with the bottom formed of loam, clay, or turf, surrounded by an inner border of a similar substance, and an outer one of sand--the one for leeches fit for medical use--and the other for breeding, or for such leeches as have been applied. No leeches are to be taken from the breeding tank until a year has elapsed after their having been applied and fed with human blood; and their removal to the first tank should take place in September, or October, as by this time the breeding season is over. By this plan all leeches that have been applied are to be carefully restored to the breeding tank, without making them disgorge the blood they have swallowed.

=LEECH'ING.= This consists in the application of leeches to any vascular part of the body, for the purpose of withdrawing blood from it, and thus allaying local inflammation, distension of vessels, &c. Leeches are most conveniently applied by means of a common pill-box or a wine gla.s.s. The part should be previously washed perfectly clean, and if covered with hair should be closely shaved. Sometimes leeches are indisposed to bite; in such cases, allowing them to crawl over a piece of dry linen or calico, rolling them in porter, moistening the part with a little milk or sweetened milk, or drawing a little blood by a slight puncture or scratch, will usually make them bite freely. To stop the bleeding from leech-bites various plans are adopted, among which the application of nitrate of silver or creasote, or gentle pressure for some hours with the finger, are the most successful. Of late years a piece of matico leaf or soldier's herb, applied in the same manner as a piece of lint, has been commonly adopted to stop the bleeding of leech-bites.

=LEEK.= _Syn._ PORRUM, L. The _Allium porrum_ (Linn.). Its general properties are intermediate between those of the onion and garlic. The juice is said to be powerfully diuretic, and capable of dissolving phosphate calculi.

=LEGU'MIN.= Vegetable casein. It is found most abundantly in the seeds of leguminous (podded) plants, _e.g._ beans, peas, &c., as well as in the sweet and bitter almond.

In properties it closely resembles the casein of milk.

Legumin may be obtained from peas or from almonds as follows:--After digesting the crushed seeds for 2 or 3 hours in warm water, the undissolved portion is removed by straining through linen, and the strained liquid, after depositing the starch suspended in it, is next filtered and mixed with diluted acetic acid. The white flocculent precipitate which is thus produced, is then collected on a filter and washed. It is afterwards dried, powdered, and digested, first in alcohol, and afterwards in ether.

Rochleder considered that, as thus obtained by Dumas and Cahours, it was not absolutely pure, since as it was not entirely soluble in a cold concentrated solution of potash, he recommended the alkaline solution being decanted from the undissolved portion, and again precipitated by the addition of acetic acid.

Legumin as thus prepared was believed by Rochleder to be pure, and was found on a.n.a.lysis to give results a.n.a.logous to those furnished by casein.

In the seed, legumin occurs a.s.sociated with considerable quant.i.ties of the phosphates of calcium, magnesium, and pota.s.sium. Rennet coagulates it like it does the casein of milk, its similarity to which is exemplified by the manufacture of a kind of cheese from peas and beans by the Chinese.

Dried peas contain about a fourth of their weight of legumin.

=LEM'ON.= _Syn._ LIMO, L. The fruit of the _Citrus limonum_ or lemon tree.

The juice, peel, and essential oil are officinal. See OIL, and _below_.

=LEM'ON AC'ID.= See CITRIC ACID.

=LEM'ON FLA'VOUR.= See ESSENCE OF LEMON.

=LEM'ON JUICE.= _Syn._ LIMONIS SUCCUS (B. P.), SUCCUS LIMONUM (Ph. L. & D.), L. The juice of the lemon, obtained by squeezing and straining. When freshly expressed, it is turbid, owing to the presence of mucilage and extractive matter. These substances render the juice liable to decomposition, and various methods have from time to time been proposed for preserving it. Amongst these may be mentioned the addition to the fresh juice of one per cent. of bisulphite of calcium, or ten per cent. of proof spirit.

"We have examined the juice expressed from two varieties of lemons, viz.

Palermo and Messina, with the following results:

Palermo. Messina.

"Ounces of juice yielded by 100 lemons 108 96 Specific gravity of juice 104485 103856 Percentage of citric acid 812 704 Percentage of ash 0289 0301

"100 parts of the ash of the juice of Palermo lemons gave:

"Sulphuric acid 1059 Carbonic acid 1633 Chlorine 081 Phosphoric acid 674 Ferric phosphate 132 Lime 889 Magnesia 302 Potash 4784 Soda 332 Silica 072 Loss 042 ------ 10000

"If lemons are kept a few months before squeezing, the yield of juice is slightly increased, but its specific gravity and percentage of citric acid remains unaltered. It is erroneous to suppose that the acid of the lemon is, by keeping, changed into sugar. We have kept lemons for 12 months, and found that the percentage of acid was not diminished. A certain proportion of sugar was formed, but at the expense of the soluble starch contained in the cell-walls of the lemon. Lemon juice on being kept is found to decrease in density, but the amount of acid remains the same." (Harkness.)

Lemon juice may be preserved by heating it to 150 Fahr., filtering, and setting it aside in bottles completely filled. If this process be performed in the winter, the juice, it is said, may be kept perfectly good for 12 months. Fresh lemon juice is prevented from decomposition and rendered fit for exportation by mixing it with 1/10th of alcohol.

(Schweitzer.)

The Merchant s.h.i.+pping Act of 1867 requires that after a s.h.i.+p has been at sea ten days 1 oz. of lime or lemon juice, mixed with 1 oz. of sugar and 1/2 pint of water, shall be served out to each of the crew between the hours of 12 and 1 in the day.

_Adult._ Lemon juice is frequently adulterated, the adulterants being water, sugar, or gum, and sulphuric or acetic acid. The _modus operandi_ is, to dilute the genuine juice with water, and then bring up the density with the sugar or gum, and the percentage of acid with one or other of the above acids. The examination of lemon and lime juice supplied to the navy is now conducted in the Inland Revenue Laboratory, Somerset House, and it speaks well for that department when we say that cases of scurvy on board s.h.i.+ps are now of very rare occurrence. No juice is pa.s.sed unless it comes up to a certain standard in specific gravity, and percentage of citric acid, and any sample containing any other acid is at once rejected.

_Prop._ Lemon juice is refrigerant and antis...o...b..tic, and has long been extensively employed in the preparation of cooling drinks and effervescing draughts, which are justly esteemed as wholesome summer beverages, as well as palliatives in fevers, nausea, &c. In scurvy, there is no remedy equal to freshly expressed lemon juice; and in acute rheumatism and gout, according to the united testimony of Dr Owen Rees, Dr Babington, and numerous Continental pract.i.tioners, it has been exhibited with considerable success. In agues, dysentery, English cholera, nausea, and vomiting, heartburn, putrid sore-throat, hospital gangrene, syphilis, and numerous skin diseases, it has proved most serviceable. See CITRIC ACID, GOUT, &c.