260 An It/fey o? i Bleaching, 



with a coating of japan, as it i3 called, or with oil paint, 

 to prevent the oozings of the liquor from rafting them. The 

 height of this cylinder mud be feven or eight feet, and even 

 more, if poifiblc, in order to increafe the preflure ; and ought 

 to have placed over it a large two necked bottle deprived of 

 its bottom, or a glafs bell with two necks cemented to the 

 upper edge of the cylinder. In one of thefe necks the large 

 tube of the refervoir is introduced, and made to defcend \o 

 the bottom of the cylinder. The air bubbles, as they are 

 difengaged, being forced to traverfc the fluid under a prefTure 

 equal to the height of the column of water, will combine 

 with it until it be faturated ; the fecond neck is alfo furnifhed 

 with a bent leaden tube, the orifice of which is below the 

 iiirface of the water ; the fuperabundant gas pafTes through 

 this tube, and, defcending into the fecond cylinder of wood, 

 (imilar in all refpe&s to the preceding, faturates the 

 water in it: — a third cylinder may be added, if judged ne- 

 ceilliry. By this arrangement the fmalleft portion of the gas 

 cannot efcape : care muft be taken to apply a leaden cock at 

 the bottom of each cylinder, in order to draw off the bleach- 

 ing liquor as it is formed. 



The refiduums, after the diftiilation of the oxygenated mu- 

 riatic acid, may be fold to earthen-ware manufacturers to be 

 employed as a glazing for their coarfe articles. The manga- 

 nefe contained in it gives it a blackifh appearance, like that of 

 bronze, which is far from being difagreeable to the eye. I 

 have employed this glazing feveral times by way of trial; 

 flrft fufmg it with fand in a potter's furnace, throwing it into 

 cold water to facilitate its divifion, and grinding it in a mill 

 in order that it might be difTufed in water. This glazing isr 

 attended with the advantage of being free from thofe dano-er- 

 ous qualities fo common in all preparations made from the 

 oxides of lead ; but the moft important object is the extrac* 

 tion of. the foda from the fulphate of foda, which is formed 

 m great quantity by the procefs,and remains in the refiduum 

 of the diftiliation. 



The firft point is, to convert the fulphate of foda into an 

 alkaline fulphuret. Malhcrbc and Athenas have fucceeded 

 m this by employing iron as the intermediate fubftance : they 

 mixed one part of charcoal duft with nine parts of the ful- 

 phate of foda, and expofed the mixture to the heat of a re- 

 verberating furnace : when the fulphuret entered into enm- 

 buftion, they added from three to live parts of old iron ren- 

 dered as fmall as poflible ; and the whole being fufed toge- 

 ther, they obtained a black pafte, eompofed of iron, foda, 

 fulphate of iron, &c. This mixture was lixiviated, and fil- 

 4 tered 



