52 On Madder, and 



without a trace of red, to cotton impregnated with the tin 

 mordant. 



Properties of Madder- Orange. — When heated in a glass 

 tube, madder-orange exhibits the same characters as madder- 

 purple, but, with this difference, that the vapours disen- 

 gaged are yellow, and condense into a yellow-brown mass. 

 If this is heated again, the same character is exhibited as 

 with madder-purple ; some charcoal is left. So that, also, 

 in this case, the matter sublimed once, cannot be again 

 sublimed without decomposition ; in other respects it dyes 

 cotton impregnated in the alum and copper mordants, as 

 madder-orange itself. It forms also a yellow solution with 

 sulphuric acid. 



Thus, three colouring matters in madder may be sublimed 

 without undergoing any essential change, like indigo, when 

 it is subjected to an equal temperature. By sublimation, 

 alone, therefore, it is impossible to separate the three 

 colouring matters. Alizarine must, therefore, be a mixture 

 consisting of more than one substance. 



With pure water, madder orange, by the addition of heat, 

 forms a yellow-coloured solution. On cooling, some depo- 

 sition takes place. In cold water the colouring matter is 

 little soluble. In well-water, or water containing lime, 

 madder-orange, by the addition of heat, forms a reddish 

 solution ; and its dyeing power will, in consequence, be 

 diminished, or altogether destroyed, as the quantity of 

 water is increased. 



Ether dissolves madder-orange readily. By evaporation 

 it remains in the form of a bright-yellow crystalline powder. 

 Cold spirit dissolves it sparingly ; boiling spirit forms a 

 bright-yellow solution, from which, on cooling, the greater 

 part of the madder-orange separates. If water is added to 

 a hot solution in spirit, small crystals separate, as with 

 madder-red and madder-purple, under similar circumstances. 



Dilute acids form, with madder-orange, a yellowish- 

 coloured solution ; on cooling, the greater part separates. 



Liquid ammonia forms a red-brown solution, from which, 

 on evaporating the ammonia, orange-yellow flocks separate. 

 When printed on the alum-mordanted cotton a dull orange- 

 colour remains, after washing in hot water. 

 Potash ley forms, with madder-orange, a dark red-coloured 



