402 Mr. Henry* s Cmjiderattons on different Materials ^ 



*^ as the mordants when formed of an acid com- 

 " bined with an earth or a metal, 3dly. I have 

 " proved, by feveral experiments that when 

 *' cotton or linen is impregnated with a ftrong 

 " folution of this alkaline mordant without any 

 *' other preparation than fcouring and galling, 

 ♦< thefe fubftances receive, in the madder bath, a 

 " red much more beautiful and deep, than can be 

 «' given them, when alum alone is ufed.*" 



Notwithftanding my deference for the opinion 

 of this great man, yet I mult on this occafion 

 differ from him, for reafons which, it is hoped, 

 will prove fatisfadory to this fociety. 



I . The portion of barilla ufed in the opera- 

 tion of aluming, is only fix pounds, fup- 

 pofing the whole quantity employed to be 

 diffolved in the firft liquor; but as there are two 

 other folutions made before the whole of the 

 fait is diffolved, it is probable that fix gallons of 

 the firlt liquor, will not contain near one half of 

 that weight; for the barilla being dry and hard, 

 and the mineral alkali lefs foluble than the 

 vegetable, the firft water will ad but flowly on 

 it; and it is obfervable that, through the whole 

 procefs, the fecond liquor is confidered as the 

 ftrongeft, and ufed for mixing with the oil. 

 Befides not much above one half of the barilla 

 confifts of aerated mineral alkali. We may there- 



♦ Macquer, Diftionaire de Chymie, feconde edition, tome 

 quatrieme, article Teinture. 



fore 



