4. Goods turned, reboiled as before, and washed.
5. Chemicked at 1/2 Tw., for 4 hours.
6. Soured at 2 Tw., for 2 hours, and washed.
7. Bucked with soda-ash for about 10 hours, and washed.
8. Chemicked as in No. 5.
9. Soured, as at No. 6, for 3 hours; washed, and dried.[222]
[Footnote 222: The strengths of the solutions, when not otherwise stated, are about the same as those given under COTTON (_ante_).]
_Obs._ The chief difficulty in bleaching linen arises from the fact that its colouring matter is insoluble in acid or alkaline solutions until it has been long acted upon by light, air, and moisture, as in the common process of grass-bleaching. Chlorine hastens the operation; but, unfortunately, it can only be employed towards the end of the process; as when earlier used, the colour of the raw cloth becomes set, and irremovable. To obviate this difficulty Mr F. M. Jennings, of Cork, has lately[223] introduced the joint use of an alkali and an alkaline hypochlorite (chloride) in the place of the ordinary chloride of lime. He prepares a bath of solution of soda at 5 Twaddle, which he raises by the addition of chloride of soda (or of potash) to 6 or 7, and in this he steeps the cloth (after the first bucking and souring) for some hours, heat, or constant squeezing between rollers, being had recourse to, to facilitate the action. Souring and washing follow, when the goods are again put into the alkaline and chloride bath, as before; after which they are soured, and bucked again with soda. These last three operations are repeated until the cloth is almost white, when crofting for one half to one fourth the time required by the usual method renders it fit for the final bucking, and finishing. Indeed, it is said that if the process be very carefully managed it renders crofting unnecessary.
[Footnote 223: Patent dated 1859.]
Raw linen loses about 1-3rd of its weight in bleaching.
III. =Silk=:--Silk is usually bleached by first steeping it, and then boiling it in solutions of white soap in water, after which it is subjected to repeated rinsings, a little indigo-blue, or archil, being added to the last water to give it a pearly appearance. When required to be very white (as for gloves, stockings, &c.), the goods are cautiously submitted, for 2 or 3 hours, to the action of the fumes of burning sulphur, and then finished by rinsing, as before.
_Obs._ Boiling or sulphuring is not required for the white silk of China.
Raw silk loses from 4 to 5 _oz._ per _lb._ by bleaching.
IV. =Wool=:--In bleaching raw wool it is first deprived of the yolk or peculiar natural varnish with which it is covered. For this purpose it is steeped and stirred for about 20 minutes in rather warm water (135--140 Fahr.), either with or without the addition of 1-4th part of stale urine; after which it is placed in baskets to drain, and soon afterwards thoroughly rinsed in a stream of water, when it is again allowed to drain, and it is hung up to dry. The further operations depend on circumstances, wool being sometimes whitened in the fleece, or in the yarn, but still more frequently and extensively not till woven. When it is intended to send it in the first two forms white to market, it is hung up or spread out, whilst still wet, and sulphured (see _below_); after which it is either at once rinsed for some time in cold water, or is previously treated with a very weak bath of soft soap.
In the case of woollen fabrics the operations of purifying or whitening the wool, beyond the removal of the yolk, are, for the most part, mixed up with the weaving and working of it. The pieces leave the hands of the weaver of a dingy grey colour, loaded with oil, dirt, and dressing. They then pass to the fulling-mill, where they are treated with fuller's earth and soap, often preceded with ammonia or stale urine, after each of which they are well washed out or scoured with cold water, and are then ready for the dyer. When it is intended to obtain them very white, or to dye them of a very delicate shade, they are commonly sulphured; after which they are washed or milled in cold water for some hours, a little finely ground indigo being added towards the end, to increase their whiteness; an addition also made when the cloth is sufficiently white without the sulphuring process.
The usual mode of SULPHURING woollen goods is to hang them up on pegs or rails, or, in the case of fleece-wool, to spread it about, at the upper part of a close, lofty room or chamber, called a sulphur-stove. In each corner of this room is set a cast-iron pot containing sulphur, which, after the introduction of the goods, is set on fire, when the door at the lower part of the chamber is shut tight and clayed. This is commonly done over-night; and by the morning, the bleaching being finished, the goods are removed, washed, and azured.
Sulphuring, unless very skilfully managed, imparts a harsh feel to woollen goods, which is best removed by a very weak bath of soap-and-water (lukewarm); but the action of soap in part reproduces the previous yellowish-white tinge. Milling with cold, or lukewarm water, tinged with indigo, is the best substitute.
_Obs._ Raw wool loses from 35 to 45% of its weight by scouring, and 1 to 2% more in the subsequent operations of the bleacher; the loss being in direct proportion to the fineness of the staple.
?The above are the four principal applications of the art of bleaching; but, in technical language, the words bleaching, bleacher, bleachery, bleach-works, &c., when employed alone, are understood to have reference only to cotton and linen. This has arisen from the enormous extent of these manufactures, and from the process of bleaching them forming a business entirely distinct from that of weaving, dyeing, or printing them.
The following, with the exception of the first, are of comparatively minor importance and interest:--
V. =Materials for Paper=:--Old rags for the manufacture of paper, and paper-pulp, are now almost universally bleached with chlorine or chloride of lime; the former being generally used in France, and the latter in England. The process usually consists in (1) boiling in an alkaline lye to remove grease and dirt, (2) washing, (3) pressing, (4) deviling or tearing up the pressed cake into fine shreds or pulp, (5) chemicking, with agitation, for about an hour, in a clear solution of chloride of lime,[224] followed by (6) washing, (7) souring with dilute hydrochloric acid at 1 or 2 Tw., or treatment with a solution of some antichlor, or both, and (8) a final washing and pressing. For the common kinds of paper, the operations included in No. 7 are omitted; but unless the whole of the lime-salt be removed from the pulp, the paper made of it is liable to turn brown and become rotten by age. In some cases rags are bleached before being divided and pulped. Cotton-waste is bleached in a similar way to rags.
[Footnote 224: The 'strength' varies with the colour and quality of the rags. From 2 to 4 _lbs._ per _cwt._ of rags is a common proportion; but for dyed and printed rags as much as 7 or even 8 _lbs._ per _cwt._ are often employed. It is better, however, to prolong the process with a weaker solution, than to hasten it by using the chloride in excess. Large rectangular cisterns of wood, or of slate, are commonly employed as the bleach-vessels. Cisterns of wood, or brick-work lined with gutta percha or with asphalto-bitumen, are employed in some paper-mills, and answer admirably.]
In France, the chlorine, in a gaseous form, is passed from the generators into the bleach-cisterns containing the pulp, which in this case must be fitted with close covers.
=VI. Printed Paper=, as Books, Engravings, Maps, &c.--These when stained or discoloured may be whitened by (1) wetting them with pure clean water, (2) plunging them into a dilute solution of chloride of lime, (3) passing them through water soured with hydrochloric acid, and then (4) through pure water until every trace of acid be removed. This process may be further improved by further dipping them into a weak solution of some antichlor, and again washing them, before finally drying them. It is only rare and valuable original works or specimens of art that are worth this treatment, which, owing to the very nature of paper, requires considerable address to manage. In many cases a sufficient degree of renovation may be effected by simply exposing the articles, previously slightly moistened, to the fumes of burning sulphur, followed by passing them through a vessel of pure water.
=VII. Straw, Straw-plait=, and articles made of them, are, on the large scale, usually bleached by (1) a hot steep or boil in a weak solution of caustic soda, or a stronger one of soda-ash, followed (2) by washing and (3) by exposure to the fumes of burning sulphur. To effect the last, the goods are suspended in a close chamber connected with a small stove, in which brimstone is kept burning. On the small scale, a large chest or box is commonly employed. A piece of brick, or an old box-iron heater, heated to dull redness, is placed at the bottom of an iron crock or earthen pan, a few fragments of roll sulphur thrown on, the lid instantly closed, and the whole left for some hours. Care should be taken to avoid inhaling the fumes, which are very deleterious as well as disagreeable and annoying.
Straw goods are now also frequently bleached by the use of a weak solution of chloride of lime, or of water strongly soured with oxalic acid or even oil of vitriol, followed by very careful rinsing in clean water; but here, as in the former case, the natural varnish, dirt, grease, &c., must be first removed by alkalies or soap, to enable the chlorine or acid to act on the fibres.
=VIII. Wax.= Wax is bleached by first melting it at a low temperature in a cauldron, from whence it is allowed to run out by a pipe at the bottom into a capacious vessel filled with cold water.
This vessel is fitted with a large wooden cylinder, which turns upon its axis; and the melted wax falls upon this cylinder. The surface of the cylinder being always wet, the wax does not adhere to it, but becomes solid, assuming the form of ribbons as it does so, and in this shape becoming distributed through water in the tub. The wax is then removed and placed upon large frames stretched upon linen cloth, which are supported about 18 inches above the ground, and erected in a situation exposed to the air, dew, and sun. The several ribbons thus placed on the frame should not exceed an inch and a half, and they ought to be so moved about from time to time as that each part may be equally exposed. If the weather be favorable the wax will become white in a few days. It is again remelted, formed into ribbons, and exposed as before. These operations are continued in until the wax is completely bleached, after which it is melted and run into moulds.
_Concluding Remarks._ The theory of bleaching, notwithstanding the giant strides of chemistry during the last 20 years, remains still unsettled; and hence the processes employed are still, for the most part, empirical.
It appears probable that chlorine acts by uniting with the hydrogen of the water, or of other compounds present, or probably with that of both, and that it is the oxygen thus liberated, and whilst in the nascent state, that is the true operative agent. Hence bleaching by chlorine, or by the hypochlorites, may be regarded as an oxidation of the colouring matter; but whether the chlorine or the oxygen effects this oxidation is of little practical importance--the result being the same--the destruction of the compound, and the removal of the colour that depends on its existence. It is doubtful whether the bleaching power of sulphurous acid is due to it as an oxidising or a deoxidising agent; but the last is probably the case, with a like destruction of the compound constituting the colouring matter.
It may, however, be supposed that sulphurous acid acts as an oxidiser, as it appears to do when it decomposes sulphuretted hydrogen; or it may act by simply altering the compound by inserting itself, a view receiving some support from the fact that wool whitened by sulphuring may be restored to nearly its previous colour by merely treating it with soap or alkalies.
The bleaching power of light depends on its actinic or chemical rays, which, like chlorine, appear to act as an oxidising agent.
Chlorates, chromates, chromic acid, manganates, &c., have been proposed as bleaching agents for textile filaments and fabrics, but without success or practical advantage. Immersion in water more or less strongly impregnated with sulphurous acid has, however, been successfully substituted for the common sulphuring process, particularly for silk.
To avoid the injury of the goods by sparks, and by drops of water highly saturated with sulphurous acid falling from the roof, Mr Thom has invented a method of passing them rapidly through, or keeping them in constant motion in the sulphuring chamber. His apparatus is constructed on the principle of the washing-machine, the fumes of burning sulphur being used instead of water.
M. Tessie du Motay has proposed a new method for bleaching. He takes about equal parts of permanganate of soda and sulphate of magnesia, and dissolves them in lukewarm water. The tissues, previously freed from grease, are to be plunged into this bath until they are covered with a brown coating. They are then to be placed in a bath of sulphuric acid at 4 per cent., and rinsed after the brown matter is removed. They may be finally passed through sulphurous acid. Mr Ramsay's method consists in sprinkling with water equal parts of chloride of lime and sulphate of magnesia, when hydrochlorate of magnesia is formed. It may be remarked that none of the more modern methods of bleaching have been found, when reduced to practice, to be cheaper, better, or more advantageous to work than those sanctioned by long experience and use.
[Further information in connection with bleaching will be found under the heads ACTINISM, BLANCHING, CALICO-PRINTING, CHARCOAL, CHLORIDES (Bleaching), CHROMATES, CHROMIC ACID, HYPOCHLORITES, HYPOCHLOROUS ACID, LIGHT, RINSING, SPOTS and STAINS, SULPHURATION, WASHING, &c.; also under BONES, ENGRAVINGS, FAT, FEATHERS, HORN, IVORY, OIL, PAPER, PRINTED BOOKS, RAGS, SPONGE, STRAW-PLAIT, TALLOW, WAX, &c.[225]]
[Footnote 225: An accurate description of the apparatus and machinery employed in bleach-works, with numerous engravings, will be found in Ure's 'Dict. of Arts, Manuf. & Mines,' 5th ed., i, 318-351, &c.]
=Bleaching Liq'uid.= Solution of chloride of lime.
=Bleaching Pow'der.= Chloride of lime.
=Bleaching Salts.= The commercial hypochlorites.
=BLEAR'-EYE= (blere'-i). _Syn._ LIPPITU'DO, L.; CHASSIE, LIPPITUDE, Fr. An exudation of a puriform matter from the margins of the eyelids, which are red, tumid, and painful; and frequently, during the night, glued together by the discharge.
_Treatm._ Mild astringent collyria, as those of sulphate of zinc or alum (6 or 8 gr. to 1 oz. of water). An ointment formed of 1 part of the ointment of nitrate of mercury (Ph. L.), diluted with 11 parts of sweet washed lard, may be advantageously applied nightly, by means of a camel-hair pencil, the smallest quantity possible only being used. Excess in eating and drinking should be avoided, and some aperient medicine taken.
=BLEAK= (bleke). _Syn._ BLAY, BLEY, (bla). The _cypri'nus albur'nus_ (Linn.), a small river-fish, the scales of which are used in making artificial pearls (which _see_).
=BLEB.= A vesicle or blister. In some states of general derangement of health this arises spontaneously. It should be treated in the same way as scalds.
=BLEED'ING= (blede'-). In the sense of a flow or loss of blood, see HaeMORRHAGE; in that of bloodletting, see CUPPING, LEECHING, VENESECTION, &c.
=Bleeding Piles.= Take every morning aperient doses of milk of sulphur, then a small teaspoonful of confection of black pepper every day. Wash externally with a sponge and cold water. Apply compound gall. ointment to the piles if external.
=Bleeding from the Air Passages and Lungs.= Let the patient at once go to bed, and keep perfectly quiet, avoiding movement of any kind as much as possible. Administer dilute acids in frequently repeated doses, with five drops of tincture of digitalis. The bowels should be kept open by means of Epsom salts in infusion of roses. Give iced drinks and let solid ice be sucked. Mustard plasters may be applied to the chest. A morphia lozenge may now and then be sucked gradually away, as well as a small piece of sal prunella. The cough must be allayed by the administration of small doses of morphia in gum water or barley water. All food should be taken cold.
The treatment that we have indicated in the last two forms of haemorrhage is intended for the exclusive guidance of emigrants or of others so placed as to be unable to summon prompt medical aid. Wherever this can be obtained no time should be lost in at once seeking it.
=Bleeding from the Nose.= Apply cold water containing ice, if obtainable.
It should be so applied to the nose as to cause a shock. A cold piece of metal, such as a key, placed on the naked back sometimes stops the haemorrhage. If neither of the above means succeed inject with a syringe a solution of alum or sulphate of zinc (ten grains to the ounce), or snuff up the nostrils some gallic acid, powder of pomegranate, kino, or catechu, mixed with starch. A plug of lint may also be dipped in either of the above solutions, or rolled in the powders, and pushed up the nostrils, or some tincture of perchloride of iron, properly diluted and applied on a piece of lint, may be tried.
=Bleeding from the Stomach.= _Syn._ HEMATEMESIS. In this case the blood is vomited usually in clots of a dark colour. It should be noticed whether it comes from the back of the nose or throat. The treatment consists in perfect repose in bed, and in the administration of dilute sulphuric acid in infusion of roses, with saline aperients. If these fail to give relief, tannin and krameria may be tried, and small doses of laudanum or five grains of alum may be given every four hours. If in pain, add to it 1/4 grain of acetate of morphia. All food and drinks should be taken cold, the latter iced. Pernitrate of iron in from 10 to 30 minim doses is a valuable remedy.
=BLENDE= (blend). A name applied to several minerals; appr., zinc-blend, or native sulphuret of zinc--the black jack of miners.
=BLIGHT= (blite). See MILDEW, and PLANTS (Diseases of).