in dyeing Cotton red. 275 



guide and without principles. Such a proceeding conduces 

 rarely and with flow fteps to any happy remits. I am ac- 

 quainted but with one method of making pi-ogrefs in the 

 arts, which is, to bring back and reduce all operations to 

 fimple principles : by thefe means we obtain fixed points of 

 departure, to which all refults and all out labours may be 

 referred. Chemiftry is now fufficiently advanced to fupply 

 us with thefe bafes, and nothing therefore is neceffary but to 

 cflablifh them. In the hands of the artift they will become 

 what formula? are in the head of the mathematician. I 

 fhall therefore attempt to give an example by fubjecling to 

 chemical principles the three chief mordants in dyeing cot- 

 ton red; viz. oil, gall nuts, and alum. 



It is known that cotton does not receive the red of mad- 

 der in a fixed manner until it has been properly impregnated 

 with oil. The red applied by printing is far from poffeffing 

 the fame degree of fixity, fince it will not ftand when wafhed 

 with foda. This preliminary preparation is given to cotton 

 by forming a cold foapy liquor from the combination of oil 

 and a weak folution of foda. The ufe of this alkaline ley is 

 attended with no other advantage than that of diluting and 

 dividing the oil, and enabling the operator to convey it to 

 all the parts of the cocton in an equal and eafy manner. I 

 have found by experience that potafh produces the fame ef- 

 fect as foda ; and, in my opinion, this fact merits fome con- 

 sideration, as foda, which is fcarce and dear in the north, 

 may be fupplicd by potafh, which is there common. 



From this principle it follows, that all kinds of foda or oil 

 cannot be employed indiscriminately. In order that the foda 

 may have the proper qualities, it mutt be cauftic, and con- 

 tain little muriate. It muff not be rendered cauftic by lime, 

 as it then make- the colour brown. Its caufticity muft be 

 the effect of its calcination. 



The carbonate of foda, and foda mixed with much mu- 

 riate, combine with oil but very imperfectly. Therefore 

 T 2 foda 



