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to twenty-four horn's. They are then taken out, and made topass through a slight washing with soap to remove the roughnessthey have acquired by the action of the acid, and to give them thenecessary softness. This process is imperfect. At first, the acidof the sulphur acts only on the surfaces, and does not penetrate.This aerial immersion is not sufficient ; the gas cannot introduceitself to a sufficient depth into the studs, and the supertic.es onlyarc whitened. A superior method has been lately invented,which is by making use of the sulphureous acid. The sulphureousacid, or that acid generated bv the imperfect combustion of sul-phur, differs from the sulphuric acid (oil of vitriol), by its con-taining less of the acidifying principle, and by being the meanterm between the sulphuric acid. Sulphureous acid gas unitesvery easily with water, and in this combination it may he em-ployed for bleaching wool and silk. The sulphureous acid inthis state of liquidity, may be prepared by making it traversewater in an apparatus nearly similar to that used for preparingoxygenated muriatic acid. The most (Economical method of ob-taining it, is to decompose sulphuric acid (oil of vitriol), bythe mixture of any combustible matter capable of taking from ita part of its oxygen. In exact experiments of the laboratory,when the chemist is desirous of having great purity, it is ob-tained by means of metallic substances, and particularly by mer-cury ; but for the purpose of which we are treating, where great(economy is required, we should recommend the most commonsubstances. \\ e shall therefore give the following process. Takechopped straw, or saw-dust, and introduce it into a mattress ;pour over it sulphuric acid, applying at the same time heat, andthere will be disengaged sulphureous acid gas (vapour of sulphur),which may be combined with water in the apparatus. The piecesare rolled upon the reels, and are drawn through the sulphureousacid by turning them, until it is observed that the whiteness issufficiently bright. They are then taken out, and are left to drainon a bench covered with cloth, lest they should be stained in con-sequence of the decomposition of the wood by the sulphureousacid ; they are next washed in river-water, and Spanish white isemployed, if it should be judged necessary. This operation isperformed by passing the pieces through a tub of clear water, inwhich about eight pounds of Spanish white have been dissolved.To obtain a fine whiteness, the stuffs, in general, are'twice sul-phured. According to this process, one immersion and reelingtwo or three hours are sufficient. Azuring or bluing is per-formed by throwing into the Spanish -white liquor, a solution ofone part of Prussian blue to 400 parts of water ; shaking the clothin the liquid, and reeling it rapidly. The operation is terminatedby a slight washing with soap, to give softness and pliability to thestuffs. The final operations of drying, stretching, pressing, &e.are foreign to our present subject.

Bleaching of Silk . Sjk is a semitransparent matter, spunby the silk-worm, and formed of a substance contained in itsbody, which becomes hard in the air. The silk when wound offthe cocoons is covered with a yellow varnish, which destroys itsbrilliancy and renders it rough. To remove this varnish, the silkis generally scoured by means of soap, by which it loses one-fourth of its weight. The matter disengaged from it is very fetid,and if the silk is not rinsed in water, putrid fermentation willtake place. Even when the best soap is used, it is generally sus-pected that it injures the whiteness of the silk. The Chinese silk, is brighter than that of the European, and the Chinese em-ploy ne soap in their operations. A slightly alkaline ley willdissolve the varnish of the silk without using soap, and this hasalso been effected by the action of boiling water at a very hightemperature. T he bleaching of silk may be effected in the fol-lowing manner. A smooth stone-ware vessel of a conical figure,is to be procured ; the common pottery-ware would lie improperfor this purpose on account of its yielding to the acrion of themuriatic acid to be employed in the process; the upper or wideraperfure is to have a cover of the same materials fitted to it bygrinding, the lower aperture is to be stopped by a cork, throughwhich a small glass-tube of about one-fourth of an inch diameter,is to be inserted. This tube is to be stopped with a cork exceptwhen the contents of the jar are to lie drawn off. To preventtliis tube from being obstructed a small perforated false bottom isplaced within the vessel. Upon six pounds of raw silk placed inthe vessel, is to be poured a mixture, previously made, of 48pounds of spirit of wine, of the specific gravity ,867 with twelve

ounces of pure marine acid, quite free from nitrous acid, and ofthe specific gravity ], 1 hi. The vessel being then covered, thewhole is lel'tTto digest until the following day, or until the liquorfrom a fine green begins to assume a dusky brown colour. Theacidulated spirit is then to be 'drawn off, clean spirit of winepoured on the silk and drawn off repeatedly till it passes colourless,The silk is'then suffered to drain without stirring, and is thenprepared for a second infusion. The same quantity oi acidulatedspirit as at the first is now to he poured upon it, and suffered toremain 24 hours or longer till the silk becomes perfectly white.This acidulated spirit may then be drawn off, and with the addi-tion of six ounces more of marine acid, may lie used for the firstintusion of other yellow silk. After this the silk is to he sprinkledwith clean spirit, and occasionally pressed down with the hand.As soon at the spirit comes off colourless, a third infusion is tpbe made with 48 pounds of spirit without acid, which is to liedrawn off the next day, and reserved for washing other silk afterthe first infusion. The silk will now be well bleached, but willretain about its own .weight of the spirit. This is recovered bysprinkling the silk with a small quantity at a time of clear riverwater.—This on subsiding carries the spirit before it, so that thpfirst portions coming from the tube are scarcely diminished instrength. The addition of water is to be continued till nothingbut mere water comes off. The silk will still retain a portion ofmarine acid, which must be washed off with water. The bestway is to pul the silk loosely in a coarse woollen bag, which isto be put loosely into a cloth, and placed in a basket; the wholeis then to be left in a running stream for five or six hours; orthe vessel containing the silk may be covered with a cloth, andwater pumped upon it for five or six hours, or until that whichilows through the lower aperture gives no red colour to the tinc-ture of turnsol. The lower aperture is then to be stopped andthe vessel filled with water, which must be changed once or twicein 24 hours. By this method pieces of gauze and entire garmentsof silk have been successfully bleached, and the finest naturalwhite silks are rendered much whiter by the same process.

Bleaching Prints, and printed Books. An applicationhas been made of the new mode of bleaching, to the whitening ofbooks and prints that have been soiled by smoke and time. Sim-ple immersion in oxygenated muriatic acid, letting the aiticle re-main in it a kmger or shorter space of time according to tliestrength of the liquid, will lie sufficient to whiten an engraving:if it be required to \vhitcn the paper of a bound book, as it is ne-cessary that all the leaves should be moistened by the acid, caremust be taken to open the book well, and to make the boards rc.-ton the edge of the vessel, in such a manner that the paper aloneshall be dipped in the liquid : the leaves must he separated fromeach other, in order that they may be equally moistened on betisides. The liquid assumes a yellow tint, and the paper beconu-si white in the same proportion ; at the end oi two or three hours,the book maybe taken from the acid liquor, and plunged into,pure water, with the same, care and precaution as recommendedin regard to the acid liquor, that the water may exactly touch thetwo surfaces of each leaf. The water must be rein wed everv ■hour, to extract the acid remaining in the pap t, and to dissipatethe disagreeable smell. By following tliis process, there is somedanger that the pages will not be all equally whitened ; either be-cause the leaves have not sufficiently separated, or because theliquid has had more action on the front margins than on tiiosenear the binding. On this account, the best way is to destroy thebinding entirely, that each leaf may receive an equal and perfectimmersion; and this is the second process recommended bvM.Chaptal. “ 1 begin,” says he, “ by unsewing the book, and se-parating it into sheets, these sheets I placed in divisions formed ina leaden tub, with very thin slips of wood or glass, so that theleaves, when laid fiat, are separated from each other by intervalsscarcely sensible. I then poured the acid into the vessel, makingit fall on the sides of Hie tub, in order that the leaves may not liederanged by its motion. When the operation is completed, theacid is drawn off" by a cock at the bottom of the tub, ami its place issupplied by clear fresh water, winch weakens and carries off the re-mains of-tlie acid, as well as the strong smell. The leaves-are ■..then to be dried, and after being pressed, may be again bound up.By tliis operation books are not only cleaned, but the paper ac-quires a degree of whiteness superior to what it possessed whenfirst made. The use of tliis acid \\ attended also with the valuable1 advantage