180 Memoir upon the Mordants 



of carbonate of lime be employed, and the same holjs 

 good with the carbonates of barytes and strontian, we shall 

 only obtain alumina and the sulphates of potass, lime, 

 barytes, or strontian. There remains no doubt, therefore, 

 of the nature of the changes produced in the alum baths 

 by the common wools, and of tlie prejudicial effects of al- 

 kalies in the baths intended for cottons ; for the addition 

 of these substances diminishes the quantity of alum, and 

 even increases the acidity of the bath. 



CHAP, II. 



On the Impregnation of Vegetable and Jn'unal Matters ivith 

 Acetate of Alumina. 

 Wool, silk, cotton, and thread, in the different states in 

 which these substances are employed for dyeing, were treated 

 with acetate of alumina, which combined entirely with 

 them. But as in exposing them to the air, or to a tem- 

 perature a little elevated, the mordant always loses a 

 small quantity of acic!, it follows that the combination 

 formed upon the stuff is an acetate with excess of base; 

 thus, by treating it with boiling water, it is converted into 

 acidulated acetate of alumina, which is dissolved, and into 

 alumina whicli cannot be carried off by the water. 



CHAP. III. 

 Art. 1. — Of the Action of acidulated Tar trite of Potass o?t 

 IFool. 

 Purified wool was treated as in the former experiments 

 with very pure crean) of tartar, free from tartrite of lime, 

 and formed directly by the tartaric acid and potass. This 

 wool was washed a great number of times, vmtil the last 

 washing did not contain any of the principles which had 

 been combined with it. The balh afforded by evaporation 

 -J- of the cream of tartar employed, or rather neutral tartrite 

 of potass. The washings were very acid, and we obtained 

 from them a small quantity of cream of tartar, and a very 

 acid composition formed of tartarous acid and wool. These 

 facts may be thought sufficiently to explain the phaeuomena 

 which take place in impregnating wool with alum and 

 tartar, since we already know from the experiments of 

 M. BerthoUet, that these two salts are not decomposed ; 

 and as we have shown that the wool comljines completely 

 with the alum, and that it acts upon the cream of tartar by 

 separating the tartarous acid with which it unites in the 

 most intimate manner. But in order lo have these facts 



rijrorouslv 



