ic6 An Ejfcj' on Bleaching. 



eiples, abforbed by the roots, with the juices aflimilated in 

 their vafcu'iar vefTels, produces new compounds. 



The defthi&ion of plants exhibits phaenomena which have 

 very little refemblance to thofe exhibited by the dhToliition 

 of animal bodies ; but the lail remit is always the natural 

 dellruction of the combination of their constituent principles, 

 the union of hydrogen and oxygen forms water, and the com- 

 bination of oxygen and carbon forms carbonic acid. It is 

 on thefe principles and modifications, applied to the treat- 

 ment of vegetable matters, that the art or destroying colour 

 is founded; it is a decomposition begun and checked in 

 proper time, or the deftructioh of foine principles in order to 

 preferve others. 



To bleach vegetable fubftances requires the concurrence of 

 feveral menflrua or deteriive fubftances ; fuch as foda, oxy- 

 genated muriates, calcareous fulphuret, and foap. There 

 are feveral precedes for depriving hemp, flax, and cotton, of 

 their colour, which may be clailcd in the following order : 



i(x, Bleaching in the open air, with the ainftance of alkali 

 and foap. 



3d, Bleaching by water alone. 



3d, Bleaching by the oxygenated muriatic acid, fubftituted 

 for the a&ion of the atmofpheric air; and this method is 

 divided into four diftincl procefTes : the firit confitts in em- 

 ploying the oxygenated muriatic acid alone; in the fecond, 

 potafh is mixed with this acid to condenfe the gafeows vapour 

 and deflroy its fuffbeating odour; for the third, oxygenated 

 muriates diflblved in water are employed ; and in the fourth, 

 fulphuret of lime is united with this acid. 



4th, Bleaching by the fleam of alkalino-cauflic water, 

 where the air and folutions of oxygenated muriates coincide 

 alternately with the action of the fleam. 



Of Hemp and Flax. 



If hemp and flax be examined immediately after they are 

 pulled, we obfervc an union of fibres cemented together, which 

 form li laments ; thefe fibres are moiftencd by the fap, and 

 the flalks, formed of bundles of filaments, are enveloped in a 

 femi- ligneous iubftance, and covered with a very thin bark. 

 The fap of textile plants differs from thofe of ligneous plants; 

 it approaches near to extractive matter; it is neither fapona- 

 ceous, nor refinous, nor aqueous, but it pbflefles fomething 

 of all thefe properties: it is foluble in water like the fap of. 

 wood, it precipitates itfelf in flakes by the action of oxygen- 

 ated muriatic acid, but thefe two kinds oi lap are diflinouiilied 



by 



