An T,ffay on Bleaching. 313 



Tn manufactories °f printed cottons, when it is intended 

 to print various figures by me ns <f mordant, they are made 

 to pais through madder, and a epm&nfttion is formed be- 

 tween the mordant or bafe and the colouring matter*. The 

 alum ufcd by calico printtfs is applied to the cloth by means 

 of blocks : at'ter it lias been diifolved, by a procefs foreign tq 

 this memoir, in vinegar (acetous acid), if fuffers to be depo r 

 (ited on the {tuff the earthy bafe, and thus renders it proper 

 for combining with the colouring matter: the ftrong affinity 

 which exilts between that matter and the bafe (mordant) 

 caufes the cloth, when it pafies through the madder, to af- 

 futne different (hades : however, as fome of the colour ad- 

 heres, though weakly, in the places deftitute of the bafe, it 

 muft be removed by repeated boilings with bran or cow's 

 dung, and expofure on the grafs. 



As one of the properties of the oxygenated muriatic acid 

 is to brig-men colours, its agency has been employed in va- 

 rious < ales. The procels of bleaching by fleam makes no 

 change in the old dilpoiitions, but only ihortens the labour, 

 especially when its action is combined with oxygenated 

 }iqnors. 



Afier being made to pafs through madder, and lying for a 

 fliorl time 011 the grafs, the cloth is expofed to the vapour 

 bath ; then immeifed in very dilute oxygenated liquor; and,, 

 in the lali place, expofed on the grafs again. Great care is 

 taken to rinfe it well, in running water, met each operation, 

 and to wafh it well by means of the ufual machinery. 



If this method fhould be adopted in paper manufactories, the 

 following is the manipulation I would recommend : The brown 

 or crude rags ought firtt to be picked and lorted ; they fhould 

 then be (lightly triturated with a cylinder, or with a peftle if 

 the former is not employed ; this coarfe pulp {hould then be 

 immerled in a cauftic alkaline ley of three degrees, and car- 

 ried thence to the (beam apparatus : it ought to be placed on 

 frames covered with canvas in ffrata of about an inch in 

 thicknefs, and the frames for this purpofe may be placed at 



* The word monlrit ought to'be entirely baniihed from the language 

 of the arts, ft nee it is as r.onlcnfical as the cxpreiiion oil of vitriol \s abfirrtl 

 when employed as the fynonyme of iulphuric ,ic ; d. The dyers formerly 

 employed I'., line foiutioivs, in which they immtHed their lhiriSs, thinking 

 that the action of this fait ferved to bite, as it were, the fubftance of them, 

 and to enlarge their pores, and, according to this idea, they gave them the 

 name of mtfkaMs (or biters). At prefent, when thefe etVc'rits can be better 

 explained, it is much to be wifhed that the word baft were fuiftitured for 

 in>j<<Li>it y adding tome epithet to denote the fublfance which forms it. 

 We know that thefe bails in general ate the earth, oi aium (argil or alu» 

 mine) and whiuvoxidt Jf tn 1 . 



a pro- 



