An Ejffay on Bleaching, 309 



t much livelier and morecauftic a&ion, when it is combined 

 with caloric, than in ordinary leys, where the temperature 

 never rifes above 163" F. : for a ley of one degree of (treugth, 

 at molt, by the areometer, is fufficient for the fleam appa- 

 ratus, and, in general, half a degree will be enmigffr. By 

 making the cloth or thread pafs through one lev of oxygen- 

 ated muriatic acid or oxygenated muriate of lime, ;in union 

 is effected between the folution and the • arbon anting from 

 the burning of the ex traclo- mucous matter of the tlax ; car- 

 bonic acid 16 formed 5 the water, even, in which this new 

 compound is diluted concurs to promote this combination : 

 if the cloth be then expofed on the grafs, the carbonic acid 

 is diffipated, and the cloth is bleached. 



It was believed that the fteam of a pure alkaline ley would 

 not be cauftic, and would not produce the fame effects as 

 the faline foiution ; and the reafon affigned for this opinion 

 was, the concentration of all the falts by the evaporation of 

 the aqueous fluid : but what takes place in the open air, 

 where the atmofphere every moment abforbs the moitture 

 which is evaporated, cannot be applied to a clofc apparatus, 

 where the temperature is elevated in an extreme degree : be- 

 fides, the caloric always carries with it a little alkali even in 

 low temperatures, as is obferved when water is poured over 

 potafh ; the fteam which iffues from it changes blue vege- 

 table colours green. 



It is afterted that in India cloth is bleached by the fteam of 

 lime water, and that the Indians brought to France by ad- 

 miral de Suffrein employed this method. To us, however, it 

 would appear very ftrange, if it really fucceeded, that it ihould 

 nave been fo loner neglected. In theory, we iind nothing 

 that can warrant fuch an operation, except that the vapour, 

 which iffues from quicklime when llakcd, changes the colour 

 of vegetables expoled to its action : on this account alone the 

 fact deferves to be put to the teft of experiment. 



[t follows, from theie chemical principles, that the L&ion 

 alone of fieam does not bieach, and that the concurrence of 

 oxvgen is neceffary to aid the compofition of the carbonic a^ ;d : 

 this acid requires for its formation 28 parts of carbon, futu- 

 rnted with 72 of oxvgen ; but ail the ox\gen contained in the 

 apparatus would not be fufficient to fat urate the ei-nfulerable 

 quantity of colouring matter burnt by the alkaline eombui- 

 tion and convened into carbon : this deficit mull be fu polled 

 by immerfion in any oxyrcn-teu liquor whatever, a ui the 

 di'perlion of the elaltic fluid thus firmed mutt be then faci- 

 litated by expofure on the grafs. 



I (hall now proceed to the various manipulations to which 

 U 3 ' raw 



