25a Olfervat'ions en ^laddering, 



with even as little madder by means of the hmc fokitlon 

 concentrated. 



The beft method of obtaining fliades lively as well as 

 bright, is to expofe the dark reds for a confidcrable time, 

 when they have been eleared, to the aftion of a ley of oxy- 

 genated mu'iate of polafh, or of foda with ex'cefs of alkaline 

 carbonate, in order to have fuch a degree of fliade as may be 

 required : but it may readily be conceived that this method 

 would be expenfive. 



To have the oily alkaline folution of alum nearly in the 

 fame ftaie of concentration, it will be nccelfary to employ an 

 areometer to determine the degree of ftrength of the cauftic 

 ley before it is en)pioycd for the folution of the alumine. 

 This cauftic ley muft be made with the beft common potaih 

 that can be procured, and the degree it gives by the areo- 

 meter mud be noted, in order that, if potafli of an inferior 

 quality be aftcrv, ards employed, the ley obtained may be 

 carried to the fixed degree by evaporation. 



Cauftic ley made v/ith four parts of good common potafli* 

 cannot contain a large quantity of foreign falls. By making 

 it on a large fcale, when the limpid part has been decanted, 

 it will be neoeflary to fliake the depofit, for fome time, twice 

 every day, that the reft of the alkaline liquor may be de- 

 canted; and that none of what ftill remains in the depofit 

 may be li^ft, jt cugb.t to be diluted with more water, which 

 may be afie'vvara- etn[)loyed to lixiviate the cotton, which 

 muft be well pui ificd and cleared before ii is dyed ; which 

 may be done by lixi^'iating and ffjaping, or merely boiling it 

 in water and then rinlingand drying U, As wringing with 

 the hands may derai.ge the filaments of the Ikains of cotton 

 and linen, and confequently weaken the thread, it will be 

 proper, in operating on a large Icale, to fqueeze them by 

 means of a prefs. 



In regard to thread or linen to be dyed of a beautiful dark 

 and .^xed red, it muft he well bleached, and impregnated at 

 leaft fovir times fueceffively with the oily alkaline'folution ; 

 becaufe, not only alumine and metallic oxides adhere with 

 more d;(FiCn!ty to linen than to cotton, but becaufe thefe 

 mineral iubiiances, when coloured, abandon linen much 

 cafier than cotton when clearing. It Uill remains to exa- 

 mine whether, between each imprppnation with the oily 

 alkaline folution of alumine, coitr^n or linen thread requires 

 to be left at reft for a greater or fijorler time before it is rinfed 

 and dried. 



* I have no doubt that, where pct.fli cannot be procured, foda might be 

 fiDjiloytd. — The AuTiioa. 



