COMPARISON OF DIFfc'ERENX KINDS OF ALUM. 



a%7 



7'hrcad. 

 Exp. 43. Weld. 



Cotton. * 



44-. Weld. 



4.5...'-... Madder, 

 4:6, Sumach, 



Calicoes. 

 4.7..... V.Weld. 



48.' Madder. 



49. ••••• 'Sumach. 



Exp. 50. 



51. < 



Silks, 

 ...Weld. 

 • >» 'Cochineal. 

 • . . Fustic. 



Silks. 



53.- Weld. 



54,. . . . ..Cochineal. 



55. Fustic. 



55. Weld. 



57. • ••• ..Cochineal. 



From these experiments it appears, that weld yellows are General ef. - 

 greened and deadened by sulphate of iron. That cochineal f^*^"* 

 is turned violet by it, without being altered so quickly as 

 kcrhies, or even as madder: and that^ without being made 

 dull its colour is sulllciently heightened for persons not much 

 used in comparing colours to prefer generally on wool those 

 produced by Roman alum with ^V ^^ sulphate of iron to those 

 of the pure Roman alum. 



In the colours 011 cotton, whether sumach or weld yellow, Oa cottoo. 

 or madder red, notwithstanding the slight differences from the 

 drying of the mordant, experiments 44, 45, and 46, with 

 purified Liege alum and xiu- ^^ sulphate of iron, never af- 

 forded us deeper or duller colours than the same experiments 

 with Roman alum and tIo of sulphate of iron. 



Sulphate of iron acts in a more striking manner on silfcs, On silk. 

 fcr tli£ wc\d yellows and cochineal cririsons on them were 

 more affected by -j-o u <^f sulphate of iron, than on woollens 



Knowing the great sensibility of silk in manifesting the The quantity 

 smallest quantities of iron, we employed it to satisfy ourselves by^sllk*^*^*^ 

 whether our alums did not contain abo^ve tttW part, as we 

 had found synthetically by pouring prussiate of potash into 

 solutions of pure alum, afterward altered by greater or 

 smaller quantities of sulphate of iron. 



We alunied silks with alum freed from iron, Roman alum, 

 the alums of liouvier, Liege, Javelle, and- Curaudau, ai)d 

 similar quantities of pure alum, to which we had addocj 

 irom T-yVij- to -^^ of sulphate oi iron. 



AftCF 



