$48 An Bffay on Bleachingz 



hemp and flax. The firft operation confifts in fcouring it in 

 a (lightly alkaline folution, or, what is better, bv expomre to 

 fleam in an apparatus we {hall defcribe hereafter*. It is 

 afterwards put into a bafket, and rinfed in running water. 

 The immcrfing of cotton in an alkaline ley, however well 

 it be rinfed, always leaves with it an earthy depofit It is 

 well known that cotton bears the -action of acids better 

 than hemp or flax ; that time is even neceffary before the 

 action of them can be prejudicial to it; and, by taking ad- 

 vantage of this valuable property m regard to bleaching, 

 means have been found to fn/e it from me earthy depofn by 

 preflmg down the cotton in a very weak folution of fulphrric 

 acid, and afterwards removing the acid by wafhing, left too 

 long remaining in it mould defiroy the cotton. 



Of the Oxygenated Muriatic Acid. 



This acid is one of the mod valuable difcoveries of 

 modern chemiftry, for which we are indebted to Scheele. 

 Berthollet is the firft who applied it to bleaching, after having 

 carefully examined its properties. 



The muriatic acid is greedy of oxygen, and takes it from 

 almoft all its combinations: to its union with oxygen it is 

 indebted for its deterfive property. Manganefe, a metal com- 

 paratively of little value, prefents an immenfe refervoir of 

 oxygen, which the muriatic acid fpeedily difengages from it 

 \n the gafeous form. This gas, combined with water, forms 

 the oxygenated muriatic acid oi the bleachers. Water thus 

 faturated afifuines a greenifh- yellow colour, its odour has a 

 fuffocating acridity, arifing from the emanation of the gas, 

 which adheres little to the fluid in which it has been con- 

 centrated, and whieh every moment endeavours to efcape. 



This acid, then, is nothing but a combination of the mu- 

 riatic acid and oxygen; but the latter principle adheres but 

 weakly to the muriatic acid, as is feen by the decoloration 

 effected by the oxygenated muriatic acid, whieh reftores it 

 to its primitive Mate of fimple muriatic acid. 



All vegetable colours are attacked by this acid, and 

 whitened with more or lefs celerity : this depends on their 

 greater or lefs facility of combining with oxvgen. The co- 

 louring matter undergoes a real flow combuftion, which ter- 

 minates by the formation of carbonic arid, which, efcaping 

 under the form of elaftie fluid, produces what we call 

 bleaching. 



* The apparatus alluded ro has been already defcribed in the Philofo- 

 phical Magazine, Vol. V. p. j4»> under the title, "Account of a new 

 Method of picuckirg Cotton. "—Edit. 



