Improved Procefs of Bkacbin^- ^ j&> 



tate his valuable labours to the public. The new method of bJeaching" was quickly aiid 

 fciccefsfully introduced into the manufaftures of Mancheftcr, Glafgovv, Rouen, Valen< 

 ciennes, and Courtray ; and it has fince been generally adopted in Great Britain, Ireland, 

 France, and Germany. The advantages which refult from this method, which accelerates 

 the procefs of whitening cottons, linens, paper, &c. to a really furprifing degree in every 

 feafon of the year, can be juftly appreciated by commercial people only, who experience its 

 beneficial efFefts in many ways, but particularly in the quick circulation of their capitals. 

 Great difficulties for a time impeded its progrefs, arifuig chiefly from prejudice and the 

 ignorance of bleachers in chemical prcfvifes. Thefe obflades were, however, foon removed 

 by Mr. Watt at Glafgow, and by Mr. Henry and Mr. Cooper at Manchefter. Another 

 difficulty prefented itfelf, which had nearly proved fatal to the fuccefs of the operation. This 

 was the want of a proper apparatus, not for making the acid and combining it with water 

 (for this had been fupplied in a very ingenious manner by Mr. "Watt and Mr. Berthollet *), 

 but for the purpofe of immerfing and bleaching goods in the liquor. Tfae volatility of this 

 acid, and its fuiFocating vapours, prevented its application in the way commonly ufed in dve- 

 boufcs. Large cifterns were therefore conftrudted, in which pieces of ituff were (Iratified ; 

 arid the liquor being poured on them, the cifterns were clofed with lids. But this method 

 was foon found to be defeclive, as the liquor could not be equally diffafed ; the pieces were 

 therefore only partially bleached, being white in fome parts and more or lefs coloured in 

 ethers. Various other contrivances were tried without fuccefs, till it wjs difcovcred that 

 an addition of alkali to the liquor deprived it of its fufFocating efFefts without deftroyinsi its 

 bleaching powers. The procefs began then to be carried on in open veflels, and has been 

 continued in this manner to the prefent period. The bleacher is now able to work his 

 pieces in the liquor, and to expofe every part of them to its aftion without inconvenience. 

 This advantage is unqueftionably great ; but it is dimihiftied by the heavy cxpence of the 

 alkali, which is entirely loft. It is moreover to be feared, that the alkali which is added to 

 the liquor, though it does not deftroy its power of bleaching', may diminifh it; becaufe a 

 folution of the oxygenated muriat of potafh, which differs from the' alkaline bleaching liquor 

 in nothing but in the proportion of alkali, will not bleach at all. This is a well-known h(\ ; 

 from which we might infer, that the oxygenated muriatic acid will lofe its power of deftroying 

 the colouring matter of vegetable fubftances in proportion as it becomes neutralized by an 



* M. BerthoUet's apparatus, hovvKver, is too complex for the ufe of a manufaftory ; Mr. Watt's is better; 

 but a range of four, five or fix hogftcads or rum puncheons connedteil \\ith one anottier ie the manner of 

 Woulfe's diftilling apparatus is preferable to either of them. Agitators on M. BerthoUet's principle may be 

 applied. The retort or matrafs fliould be of lead, ftanding in a water bath ; its neck fliould be of fufficient 

 length tocondenfe the common muriatic acid, which always comes over ; and it fliould form an inclination to- 

 wards the body of the retort, fo that the condenfed acid may return into it. I beg leave to ohfcrve here, that 

 I always found the liquor to be ftrongcft when the diftillation was carried on very (lowly, I have alfo found 

 that the ftrength of the liquor 'v, much increafed by diluting the vitriolic acid more than is ufually done. The 

 following proportions aftbrded the ftrongeft liquor : 



Three parts manganefe. 

 Eight parts common fait. 

 Six parts oil of vitriol. 

 Twelve parts water. 

 Th« proportion of manganefe is fubjeft to variation according to its quality. 



ftlkali. 



