400 Mr. Henry's Confiderations on different Materials, 



this argillaceous foap to be totally infoluble in 

 water and in fpirit of wine. It is probable alfo 

 that the blood which is employed with the mad- 

 der, may fupply both animal falts and a glutin- 

 ous matter to the cotton. This feems to be the 

 tife of the blood, and not, as M.'Borelle fup- 

 pofes, to communicate a pinky tinge to the 

 madder. 



Here then appear to be feveral different fub- 

 ftances employed, tending to form infoluble 

 compounds with the argillaceous earth of the 

 alum. But whether, when depofited on the cloth, 

 they remain fo many diftind compounds, or may 

 all unite into one infoluble body, I do not pre- 

 tend to determine, 



M. Macquer, whofe opinions always deferve ■ 

 the moft refpeftful attention, declares, that the' 

 excellence and permanency of the Turkey red 

 depends on the great quantity of alkali, ufed 

 in the procefs of aluming, rediflblving the earth 

 of alum after its feparation from the vitriolic 

 acid, and forming with it a faline compound, 

 eafily feparable into its conftituent parts, fo that 

 the aluminous earth may be conveniently de- 

 pofited on the cotton and united to the colouring 

 matter. The following is a tranflation of his 

 own words, from the laft edition of his Dic- 

 tionary. 



'f In examining," fays this excellent chemift, 

 «» the effects of all the complicated operations^ 



" attendant 



