34 On Bleaching. 



drab colour : it was then dyed in madder, which brought it 

 to a deep purple; and on bleaching it for a fortnight, I 

 found the colour as permanent as if a solution of iron 

 (iron-liquor), or sulphate of iron (copperas), had been used 

 as a mordant, but more muddy. 



I was then satisfied that a considerable quantity of iron 

 was present, not only in the raw material of cotton, but in 

 consequence of some weavers making or allowing their 

 dressing to remain in iron pots, which they generally call 

 sowings in Ireland, and sowlings in Lancashire. 



The dressing is nearly the same in both countries, as it 

 consists of the farina (flour) of wheat, oats, or potatoes, 

 and, when sour, is capable of dissolving iron. This is well 

 known from iron liquor used by calico printers bemg 

 made with ve;;clable acid, in which they put iron hoops. 

 This iron liquor is the mordant for black and purple, and is 

 dyed in logwood or madder; and when, in consequence ot 

 accident m printing, it is necessary' to discharge the black, 

 or purple colour before they are dved, if recourse is had to 

 oxygenated muriatic acid, an iron mould is produced, that 

 is, tlie colour becomes buff or gold ; but use sulphuric or 

 marine acid, and the colour is discharged. I have men- 

 tioned this circumstance for the purpose of showing why 

 some pieces assume a much deeper buff than others, v^-heu 

 put into ihc oxygenated muriatic acid, as the quantity of 

 u'on put on the warp by the weavers will depend on their 

 using or not using iron pots, the strength of the acid of 

 their dres^ing, the rust or cleanness of their pot, and con- 

 ftqucntly the quantity of iron it holds in solution. 



The experiment however, before mentioned, induced nic 

 to take 100 pieces which had been once boiled in potash 

 and washed, and imfflerse them in sulphuric acid (bleachers 

 sours), and after remaining about 1-2 hours they were 

 washed, and again boiled in potash. 



After being washed and without beinc; put on theblcach- 

 gvecn, they were put into the oxygenated muriatic ac.d for 

 the usual time (about 1 2 hours) , and came out perfectly 

 free from any buff appearance; which convinced me, as it 

 must every one who knows its use, that the sulphuric acid 

 had divested them of iron, and consequently had left none 

 to hv oxidated by the oxygenated muriatic acid, or the 

 oxygen of the atmosphere. They were again boiled and 

 immersed in the bleaching liquor alternately, until they had 

 fix boils, and five bleaching liquors; and on the seventh 

 tlay, without being put on the grass, they were the whitest 

 .and .-trongest pieces I had ever seen : and during the pro- 

 cts? appeared uncoinmonly clear ; for after the fourth boil 



they 



