of Its different States 07i Dyeing. 45, 



fead long before observed ; namely, that whiteness, so tar 

 from being the same in substances belonging to diftcreut 

 classes, varies even in the produce of the same class : thus, 

 the white of cotton will never be the same as that of thread, 

 and a difierence w ill alwayis be perceived between the white- 

 ness of wool and that of silk, in the same manner as we 

 distinguish, though with greater difficulty, the numerous 

 products of individuals of the same f"an)i!y. For it cannot 

 be doubled that, if even the same disposition of the surfaces 

 could establish between all these bodies a certain identity for 

 reflecting the light ; yet, as the sn-.allest ditference of their 

 nature must aft'ect their affinity, this alone would be suffi- 

 cient to produce alterations in them. 



The intention of these researches was to ascertain the 

 influence which the state of the animal must exercise over 

 the grease, and the nature of the wool. 



The grease is a fatty, unctuous substance, with a verv 

 strong smell, which is supplis^d in the sheep by sweat, and 

 the transpirable miitter emitted by all animals. When dis- 

 solved in water, and filtered to disengage it from the earthy 

 and animal matters which adhere to it, it is of a beautiful 

 yellow fawn colour, more or less inclined to red, and com- 

 posed, according to M. Vauquelin, of a soap with a basis 

 of potash, anima) matter, lime, and potash, combined with 

 carbonic, acetic, and muriatic acids. Filtration likewise 

 separates a white matter floating on the surface of the 

 grease, and which in scouring does not combine with the 

 alkalies : it appears to be of the same nature as suet ; it 

 meltSy and becomes liquid, at a low temperature, and takes 

 fire very easilv. 



The animal matter dissolved by alkalies is precipitated of 

 a reddish yellow by all the acids. Oxys^enated muriatic 

 acid and oxygenated muriatic acid gas form in it .a white 

 flaky precipitate, which becomes coloured by exposure to 

 the air: it is a kind of paste, soil, somewhat viscous, of a 

 dirty yellow colour; it speedily becomes liquid, and burns 

 with a bright white flame. Tiiis matter, when kept for 

 some hours at eighty degrees, in several pounds of water, is 

 totally insoluble; l)ut by evaporating the liquid you obtain 

 a small quantity of a soft matter, of a dark brown colour, 

 which has an agreeable smell, resembling that of the ex- 

 tract of liquorice. He was the less surprised to find this 

 smell in the grease, as in his experiments made in the 

 year ]800, l)y which he first demonstrated the presence of 

 potash in it, he remarked that ammonia, kept in digestion 

 V'ith this substance, gave it a strong smell of orange flowers, 



and 



