Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/675

 567 B L E A C H I N G. The rule, in general, is good. I obferve, that be a fuilicient anfwer to the objeftion. But it appears incolour. thofe buckings which continue from the Saturday night not to be true, from an obfervation of Mr John Chriftie, That doth laid down in the beginning of June, and fi- to the Monday morning, the cloth has always the deeped When that cloth has been expofed fome hours nifhed in September, takes generally lefs work, and un- tocolour. dergoes fewer operations, than what is laid down in March, the influence of the air, thefe colouring particles, which are but loofely attached to it, are evaporated, and and finilhed in June. “ The other objection is, That cloth dries much fader the linen appears of a brighter colour. This operation in windy weather than in calm funlhine; but it does not does no more than complete what the former had almod bleach fo fad. This would feem to Ihow, that the fun finilhed. If its own merit were thoroughly known, there has fome particular influence independent on evaporation. would be no occafion to attribute that of another operaIn anfwer to this obje&ion, let it be confidered, that it tion to it. Thread, and open cloths, fuch as diaper, is not the evaporation from the furfaee, but from the may be reduced to a great degree of whitenefs, after one more internal parts that is of benefit to the cloth. Now, bucking, by it alone. No cloth, as would appear, can this latter evaporation mud: be much dronger in funfliine attain to a bright whitenefs without it. than in windy weather, on account of the heat of the “ Since the only advantage of watering is the remofun, which will make the cloth more open; while the val of the falts, and what they hive diflblved, might we coldnels of windy weather mud fhut it up, fo that the not effectuate this by fome cheaper, and more certain evaporation will all be from the furface. Clear funlhine, method ? For it occupies many hands ; and mull depend with a very little wind, is obferved to be the bed wea- altogether on the uncertainty of the weather ; fo that, in ther for bleaching; a convincing proof that this reafon- the beginning of the feafon, the bleacher is often obliged to repeat his buckings without bleaching. We might ing is jud. “ It would feem to follow as a corollary from this rea- take out the alkaline falts by acids; but then the other foning, that the number of waterings ftiould in general fubdance would be left alone in the cloth, nor would any be in proportion to the drength of the lye; for the walking be able to remove it. Mill-wafhing appears a dronger the lye is, the more, there is to be evaporated; more probable method of taking out both falts and oils ; and the greater the danger, in cafe the cloth ihould be and it would feem that this might, in a great meafure, allowed to dry. But there is an exception to this gene- fupply the place of watering; but upon trial it does not ral rule, arifing from the confideration of another cir- fucceed. Two parcels of linen were managed equally in cumdance. It is obferved, that cloth, when brown, dries every other refped, except in this, that one was waterfooner than when it becomes whiter, arifing from the ed, and expofed to the influence of the air, and the oclofenefs and oilinefs which it then has, not allowing the ther was only mill-walhed. This method was followed water a free pafiage. Perhaps that colour may retain a until they were fit for fouring. The cloth which had greater degree of heat, and in that way affid a very little. been mill-walhed, had a remarkable green colour, and Cloth therefore, after the fird buckings, mud be more did not recover the bright colour of the pieces managed carefully watered than after the lad. in the common way, until it had been treated like them “ It follows likewife from this reafoning, that the foil for a fortnight. The green colour was certainly owing of the bleachfield flrould be gravelly or fandy, that the to a precipitation of the fulphureous particles, with which water may pafs quickly through it, and that the heat may the lye is impregnated, upon the furface of the cloth ; be increased by tire reflection of the foil: for the fuccels owing to the falts being walhed off more fpeedily thau of this operation depends on the mutual aCtion of heac the fulphur, to which they are united in the lye. The and evaporation. It is likewife neceffary that the water attachment betwixt thefe two bodies we know is very fliould be light, foft,. and free from mud or dirt, which, loofe, and the feparation eafily made. Evaporation theu not being able to rife alongwith the water, mud remain alone is fufficient to carry off thefe fulphureous parbehind. When there is much of this, it becomes neceffary to rinfe the cloth in water, and then give it a mill- ticles.” ing, to take out the dirt; elfe it would be fixed in the SOURING. cjoth by the following bucking, as it is not foluble by the lye. It is well known to all chymifts, that alkaline faks “ This operation has more attributed to it by bleach- are convertible, by different methods, into abforbent ers than it can Judly claim. The cloth appears, even to earths. Frequent folution in water, and evaporation o£ the eye, to whiten under thefe alternate waterings and it again, is one of thefe. This tranfmutation then of dryings ; and thefe naturally get the honour of it, when thefe falts, which are not volatilifed or walhed away,, n more properly belongs to the former operation. Here mult be continually going on in the cloth under thefe allies the fallacy. Alkaline falts give a very high colour ternate waterings and dryings of the former procefs ; not: to the decoCtions, or infufion of vegetables. This is indeed after the firfl two or three buckings < beprobably owing to the folution of the oleaginous colour- tamuch ufe the falts, not having entered deep into the cloth, ing particles of the plant; which particles,, being opened; are eafily walhed off, or evaporated. But when they and feparated by the faks, occupy a greater fpace, and penetrate into the very compofition of the laff and migive a deep colour (o the liquor. The cloth participates nuteft fibres, of which the lirft veffels are made, they of the liquor and colour. Hence bleachers always judge find greater difficulty of efcaping again, and mull be more ef the goodnefa of the bucking by the deepneis of its fubjeff to this tranfmmation. But if we confider the bleaching