138 
ters and possessed of much lustre. The aluminium com- 
pound, when prepared in the same manner, appears as a 
yellow deposit consisting of microscopic crystals. The am- 
moniacal solution gives with acetate of lead a voluminous 
orange -coloured precipitate, with acetate of copper a light 
brown, and with nitrate of silver a reddish-brown precipi- 
tate. The other compounds are of no particular interest. 
All the compounds of the acid which are soluble in water 
yield yellow solutions; none are red. It is chiefly the 
presence of this acid in crude alizarine which affects the 
colour of the alkaline solution, changing the violet due to 
alizarine into purple, or when present in larger quantity, 
into red. For the same reason an alkaline solution of crude 
alizarine does not show the absorption bands in the spectrum 
so distinctly as one of pure alizarine. Alkaline, as well as 
alcoholic solutions of anthraflavic acid, absorb the blue end 
of the spectrum very powerfully, though no bands are 
visible, even with very dilute solutions. A solution of the 
acid in concentrated sulphuric acid, if not too dark, shows, 
however, a broad but well-defined absorption band at the 
extreme edge of the blue bordering on the green, accom- 
panied by a total absorption of the violet as seen with the 
other solutions. 
Anthraflavic acid dissolves very readily in fuming nitric 
acid even in the cold, yielding a deep yellow solution, which, 
on standing for 24 hours, becomes lighter in colour, without 
evolving any gas. On now adding water a quantity of 
light yellow shining crystals is deposited. These, when 
filtered off, washed, and dried, resemble anthraflavic acid. 
They are, however, totally different in their properties, and 
consist, there can be no doubt, of a so-called nitro-acid, in 
which one or more atoms of hydrogen are replaced by 
N 0.,. When heated they deflagrate, and they give a potassium 
salt crystallising in yellow needles, very little soluble in 
water, and resembling picrate of potassium. Want of mate- 
