BLE
BLE
afterwards in a large quantity of water, in order to free it com-pletely from the weaver’s dressing, and the saliva of the spinners.In this country, machinery is employed for rinsing and beating:the apparatus must be arranged according to the objects to bebleached ; the skeins of thread must be suspended in the tub des-tined for them, and the cloth must be rolled upon reels in the ap-paratus. When every thing is thus disposed, the tubs are liltedwith oxygenated muriatic acid, by introducing a funnel, which de-scends to the bottom of the tub, in order to prevent the dispersionof the gas. r lhe cloth is wound, or the frame-work on which theskeins are suspended is turned several times, until it is judged, bytaking out a small quantity ot the liquor from time to time, andtrying it by the test of the solution of indigo, that it is sufficientlycxluusted. The weakened liquor is then drawn off, and may beagain employed for a new saturation. Great difficulties for a timeimpeded the progress of this method of bleaching, arising chieflyfrom prejudice, and the ignorance of bleachers in chemical pro-cesses. I hese obstacles were, however, soon removed by Mr.Watt, of Glasgow , and Mr, Henry and Mr. Cooper at Manches-ter. Another difficulty presented itself, which had nearly provedfatal to the success of the operation. This was the want ot a properapparatus, net for making the acid and combining it with water,for this had bee* supplied in a very ingenious mauner by Mr.Watt and M. liertholiet; but for the purpose of immersing andbleaching goods in the liquor. The volatility of this' acid, and its
suffocating vapours, prevented its application in the way com-monly used in dye-houses. Large easterns were therefore con-structed, in which pieces of stuff were stratified; and the liquorbeing poured on them, the cisterns were closed with lids. Butthis method was soon found to be defective, as the liquor couldnot be equally diffused; the pieces were thereto' e only yarimUvbleached, being white in some parts, mu*o or less coloured inothers. Mr. Hupp of Manchester, invented an apparatus forbleaching clotU, e.-.ioeedingly simple in its construction, of smallovpence, and which contains the liquor in such a manner as toprevent the escape of the oxygenated muriatic acid gas. A con-sideration of-no less importance in the arrangement of this appa-ratus, is the impossibility of the vapour injuring the health of theworkmen. It was found,' however, that the use of the oxygenatedmuriatic acid alone weakened the cloth, and various methods ofpreventing its noxious effects upon the health of the workmen weretried without success; till it was discovered that an addition ofalkali io the liquor deprived it of its suffocating effects, withoutdestroying its bleaching powers. The process began then to becarriet! on in open vessels, atnl has been continued in this mannerto the present period. The bleacher is now able to work hispieces in the liquor, and to expose every part of them to its ac-tion, without inconvenience. Potash was at first used for thispurpose ; and although this advantage was unquestionably great,it was diminished by the heavy expence of the potash, which wasentirely lost. Also, the potash which was added (o the liquor,though it did not destroy its power of bleaching, diminished it;because a solution of the oxygenated muriate of potash, whichdiffers from this bleaching liquor in nothing but in the proportionof alkali, will not bleach at all. This is a well known fact, fromwhich we might infer, tliat the oxygenated muriatic acid will ioseits power of destroying the colouring matter of vegetable sub-stauces, in proportion as it becomes neutralized by potash. It wasafterwards discovered that the oxymuriatie acid might be com-bined with the alkaline earths, as lime and barytes, and also withmagnesia ; by this means forming oxynuiriates, which were solu-ble in water, and had the property of bleaching. The oxy muriateof lime is at present used in almost all the bleaching-grounds. Forthe manner of preparing it, Mr. Tennant took out a patent; butthis lias been lately contested, and ft is now prepared and used byall the bleachers through the country. If the oxygenated muri-atic acid is passed through lime-water, it will combine with thelime, and form oxymuriate of lime ; but as the water can only re-tain a small portion of lime, tiffs was not found of much use. Tocause a larger quantity of lime to combine with the oxymuriatieacid gas, the lime is mechanically suspended -in the water, intovvhicli the gas is made to pass, and agitated, so as to present freshmatter to the gas. By this means, the oxymuriate of lime is form-ed in a very convenient manner; it is dissolved in water, and usedas a bleaching liquor. This liquor is found to be preferable tothe oxygenated muriatic acid and potashVOL i.-— no.
field in Ireland , four leys of potash are applied alternately withfour weeks exposure on the grass, two immersions in the oxyge-nated muriate of lime, a ley of potash between the two, anti theexposure of a week on the grass between each ley and the immer-sions. During summer two leys and fifteen days exposure arcsufficient to prepare doth for the action of the oxygenated muri -ate; then three alternate leys, with” immersions in the liquor, willbe sufficient to complete the bleaching; nothing then will be ne-cessary, but to wind the cloth through the sulphuric acid. Theoxygenated muriatic acid gas may also be combined with lime ina dry state, or the water may be evaporated, when it is employedtor the formation of oxymunates, which may then lie very conve- 1niently transported to any distance without'injury to its detersivepower; an advantage not possessed by the acid Idone, which camnot be transported without the loss of almost half of its strength. Inall the processes for bleaching which have been hitherto described,we have seen that potash acts a distinguished part, either us anauxiliary, or as a principal agent. To find a detersive substancewhich might be a substitute for it, was an object of the utmost im-portance. Mr. Kirwan suspected that it would be found in thesulphuret of lime, and his opinion was eonfirmeJ’by Dr. Iliggins.Sulphur and lime are both cheap articles: they are very easilycombined, and this combination completely answers the purposesof potash, without any danger of injuring the .linen. The sulphu-ret of lime is prepared in the following mr^er for the purpose otbleaching: Sulphur or brimstone, in ii'-‘ e powder, four pounds\lime, well'slacked amt sifted, twenty pounds; water, sixteen gal-lons; these are to be wot mixer., 'and boiled for about half anhour ir. an iron .vessel, stirring them briskly from time to time.Soon- after the agitation of boiling is over, the solution of the sul-wh-iiret of lime clears, and may lie drawn oil' free from the insolu-ble matter, which is considerable, and which vests upon the bottomof the boiler. The liquor, in this slate, is pretty nearly of the.colour of small beer, but not quite so transparent. Sixteen gal-lons ot fresh water are afterwards to be poured upon the insolubledregs in the boiler, in order to separate the whole of the sulphuretfrom them. Vi lien this clears (being previously well agitated,) itis also to be drawn off, and mixed with the first liquor; to theseagain thirty-three gallons more of water may be addeti, which willreduce the liquor to a proper standard of steeping the cloth. Herewe have (an allowance being made for evaporation, and for thequantity retained in the dregs) sixty gallons of liquor from fourpounds of brimstone. Although sulphur, by itself, is not in anysensible degree soluble in water, and lime but sparingly so, waterdissolving only about one seven-hundredth part of its weight oflime ; yet the sulphuret of lime is highly soluble. When linen istreed irom the weaver’s dressing, in the manner already described,it is to be steeped in the solution of sulphuret of lime (prepared asabove) for about twelve or eighteen hours, then taken out and verywell washed. When dry, it isto be steeped in the oxvimiriate oflime tor twelve or fourteen hours, and then washed" atyd dried.This process is to be repeated six times, that is, six alternate im-mersions in each liquor, which has been found to whiten the linen.Steam has been lately employed With great success in France .The process was brought from the Levant Chaptal first made itknown to the public. The bleaching of vegetable substances de-pends on the destruction of their colouring principle by the com-bined action of the air, moisture, and light; or rattier, by theunited influence of these principles to alter their natural colour.Alkalies have, on the colouring matter of vegetables, an actionwhich produces the effect of a real combustion. .Were wb inti-mately acquainted with the nature of potash and soda, we mightbe able to explain the. cause of this burning; but it is sufficientfor us at present to know the effect. The exposure- of vegetablematters on the grass, subjects them to the action of the solar rays,and moistening them during their exposure, facilitates, with theevaporation ot the water, the emanation ot the carbonic acid form-ed by tire oxygen of the atmosphere, which combines with thecarbon resulting from the alkaline combustion. It even avreespretty well with theory, in terminating the process of bleacfiine,to immerse the cloth and thread in sour milk, acidulous liquor's, or,what is more convenient, very weak sulphuric acid. In propor-tion as the alkali, during the first immersion, destroys the colour-ing matter, the oxygen of the atmosphere, or that furnishethbv"the oxygenated muriatic acid, joins that carbonized matter, andAt the great bleach-1 forms carbonic acid, which afterwards resolves itself iilto gas.
* 5 Z This