B L E 



B L E 



Hence it appsar?, that after raw cotton or linen lias been 

 afted upon by alkalies for two or three times, they have no 

 further efTsft upon it, till the cloth comes in contaft with 

 oxygen or pure air, cither by imnierfion in the oxygenated 

 muriatic acid, or by expofure to the atmofphere ; and it is 

 on account of the fpeedy aftion of the acid, in comparifou 

 with tiiat of the atniofphere, that the new mode of bleach- 

 ing is now generally adopted. 



M. BerthoUet, and the modem chemifts fuppofc, that the 

 colouring matter of linen, is compofed princip;dly of carbon 

 and hydrogen ; and they conclude, that linen, bleached by 

 the oxymuriatic acid, becomes yellow, on tliis principle, that 

 when the oxymuriatic acid renders linen white, a quantity of 

 oxygen has combined with the colo\iring particles ; but that 

 this oxygen gradually enters into a combination with the 

 hydrogen, and forms water which paffes oft' ; that then the 

 carbon becomes predominant, and the linen, in confequence, 

 aflumes a yellow colour. 



The old chemifts, en the principles of Stahl, wo\:IJ f;iy, 

 that a part of the <lephlogillieated marine acid, (oxymu- 

 riatic acid,) after the cloth had been acled upon by the 

 alkali, abforbed fucb phlogiftic colouring matter from the 

 cloth, as the alkali had no affinity for ; and thus became 

 diluted common marine acid, which has a great attracftion 

 to cotton or hncn, and, if expofed to a moderate heat, will 

 a(2; upon the texture of the cloth, and render it of a yelljw 

 colour. 



We notice this circnmftance In two different points of 

 view, that the bleacher may be aware of the neceiTitv of ap- 

 plying, in either cafe, a weak ley of pearl-afli, ultimately 

 after the ufe of the muriatic acid, to prevent this yellownefs 

 from occurring ; and alfo that the reader may comprehend 

 the reafonirg of Home, and other perfons who have written 

 upon thefubjed of bleaching, previous to Mr. Scheele's dif- 

 «overy. 



To recover the pure alkali from the black coloured leys 

 which have been ufed in bleaching, and to render them 

 equally proper for the fame purpofe, has been for a coniider- 

 able time a material objeft in the neighbourhood of Man- 

 cherter, and prattiled with great fueceis. 



To effect this, the black or brown ftrongleys, which have 

 been left after bucking linen, orcottonyarn, orgoods, orfavtd 

 after wringingthem,is putintoan oblong flat lliallow iron pan, 

 made of plate-iron, rivctted together. (See Plat^ IV. Jig. 4,5.) 

 Under this pan a fire is made, and the old leys gradually 

 evaporated, till they become of a coufilleuce nearly refem- 

 bling tar ; the matter is then put into calks, and carried to 

 the reverberatory furnace, Plale IV .Jig.(>, 7. where it is laded 

 or poured into the cavity orbed withm the furnace ; the tire 

 being then made, acts powerfully on the alkaline mafs ; 

 gradually dries the water left amongft it ; then acts on the 

 colouring matter the ley has abihacled from the cloth, which 

 is partly diffipated in a black, ofTenfive fmoke, and partly 

 dellroyed by combuflion ; the calcination of the afhes is 

 affilled from time to time, by raknig them up with a long 

 iron rod, in order to expofe frelh furfaces to the flame ; the 

 heat is continued and increafed till the inflammable matter 

 amongft the alkali is diffipated, and the aflits brought to a 

 perfect fluid Hate; they are t!itn let out by an aperture in the 

 fide of the furnace, into an old iron pot put into the ground, 

 and when cold, broken into fmall pieces for ufe, being fre- 

 quently in a purer (late then when firlt imported. 



Fig. 4. Plate IV. is a feftion of the evaporating pan for 

 the walle leys, where A reprefents a flat iron pan, of an 

 oblong fqnareform, ab ;ut fix inches deep, and of a fize pro- 

 portionate to the quantity of leys to be evaporated ; B, the 

 Jire -place ; C, the aih-hole ; D, the flue in which the fire 



«cli under the pan ; E, the chimney for the fmoke ; F, the 

 brick work. 



Fig. 5. Plale IV. is a bird's eye view of the fame evapora- 

 ting pan, which is made of plates of beaten iron rivetted 

 together, as (hewn in the plan ; the fire-place underneath 

 it is marked by dotted hues at B, and the chimney flue 

 at K. 



Fig. 6. Plite IV. reprefents a longitudinal feftion of the 

 reverberatory furnace ufed in the preparation of afhes, or 

 lolid alkaline falls from the old leys alter evaporation, to a 

 proper conlillence ; a, the brick work ; b, the afh-hole ; c, 

 a char.i'.el, or paflage under the furnace, to admit a free 

 current of air ; (/, the fire-grate ; e, the fire-place ; f, the 

 inner part of the furnace ; g, the bed of fire-proof brick, 

 on which the matter is calcined ; A, the alkaline ley to be 

 calcined ; i, a door through which the ley is introduced by 

 an iron ladle into the furnace, and through which door the 

 matter, during calcination, is iHrred from time to time ; k, 

 the paffage for the fmoke, or chimney, which cliimney 

 fliould be from 20 to 30 feet high ; /, the upper part of the 

 furnace, arched like an oven ; />, the feparation wail bttweea 

 the fire and matter to be fluxed or calcined. 



Fig. 7. Plate IV. reprefents the upper plan of the furnace, 

 of whieli /?;■. 6, is a feftion ; a, the outer walla; b, the 

 afli-hole and draught-hole ; e, the iron grate of the fire- 

 place ; g, the bafon in which the leys are calcined ; m, the 

 door tlnough which foffil coal is thrown into the fire place ; 

 n, an iron tube through which the adies in fufion flow out 

 of the furnace when lufficiently calcined ; 0, an iron pot 

 into which the melted allies flow, and where they are fuftered 

 to cool ; p, a wall of fire-brick between the fire-place and 

 bafon, over which wall the fire paffes ; r, the fteps leading 

 down to the afh-hole. 



It is neceffary to remark, that all the interior part of the 

 reverberatoiy furnace Ihould be made of Welfli brick, or 

 fuch as will withftand the aftion of a ftrong fire ; the whole 

 building fliould be well bound ti?gether by iron bars, or 

 cramps. If fo conflrufted, it will lall for feveral years; and 

 when it then wants repair, the afhes, which will be found 

 accumulated in the interllices of thd brick-work, will 

 defray the expence of fuch repairs. 



Having ftiewn the methods generally- ufed in bleaching 

 linen and cotton, we fliall notice a procefs lately difeovered by 

 Mr.W. Higgins of Dublin, forufing the fulpliuret of lime, as 

 a fubllitute for pot-aflt in bleacliing. The lulphuret is pre- 

 pared in the manner following, viz. fulphur or brimftone in 

 fine powder, four pounds ; lime well flaked and fifted, 

 twenty pounds ; water fixteen gallons ; thefe are all to be 

 well mixed, and boiled for about half an hour in an iron 

 veffel, flirring them brifldy from time to time. Soon after 

 the agitation of boiling is over, the folution of fulphuret of 

 lime clears, and may be drawn oft free from the precipitate, 

 which is confiderable, and which reds upon the bottom of 

 the boiler. Tlie liquor, in this ftate, is nearly of the colour 

 of finall beer, but not quite fo tranfpareut. 



Sixteen gallons of watg- are afterwards to be poured upon 

 the remaining precipitate in the boiler, in order to feparate 

 the whole of the fulphuret from it ; the matter is then well 

 ag'tated, and muft, when fettled, be drawn off, and mixed 

 with the firlt liquor ; to thefe again thiriy-three gallons more 

 ot water may be added, which reduce the liquor to a proper 

 llandard for llceping the cloth. 



Though either hme or fulphur, feparately, are very little 

 foluble in water, yet this lulphuret of bine is highly 

 folubie. 



This preparation has been applied, in the following 

 jnanntr,to the bleaching of liueu iii Ireland. 



The 



