BLEACHING. l67 



*'We have hitherto used the old term of oxynuiri- 

 atic acid, because it is best known by this name in 

 the bleaching processes ; but it will be remem- 

 bered that this substance is now considered as a 

 simple body, and is known by the name of chlorine. 

 What has just been called oxymuriate of lime 

 is known among modern cliemists by the term 

 cldorate of lime. 



The oxymuriatic acid gas, or chlorine, may be 

 procured by distilling muriatic acid in black oxide 

 of manganese ; but to save the expense of first 

 preparing the muriatic acid, the usual practice in 

 bleaching is to mix three parts of black oxide of 

 manganese with eight parts of muriate of soda or 

 common salt, and five parts sulphuric acid, diluted 

 with four parts water. 



To ascertain the strength of the liquid for 

 bleaching, a solution of indigo in the sulphuric acid 

 is employed. The colour of this is destroyed by 

 the oxygenated muriatic acid; and according to the 

 quantity of it that can be discoloured by a given 

 quantity of the liquor, its strength is known. 



The linen is usually not immersed in the solution 

 of oxymuriate of lime until after the fourth or fifth 

 bucking ; because a great portion of the resin is 

 removed cheaper by the alkaline leys, and washing 

 in water. 



Tlie last operation in bleaching is souring, or 

 steeping the linen in some sour liquid of a blood 

 heat. For this purpose, formerly sour milk was em- 

 ployed : but now sulphuric acid is used. Of this 

 as much is put into water as will give it the acidity 

 of vinegar. The linens are generally steeped about 

 twelve hours, and are tlien well washed. This 

 souring is essential to the procuring of a good white, 

 but the theory of its action is not well understood. 



TNI 4 



