126 MR. E. SCHUNCK ON A COLOURING MATTER 
product of decomposition formed by the action of the 
atmospheric oxygen on the colouring matter. 
The watery solution produces, with different reagents, 
the following reactions. With acetate of alumina it gives 
a bright yellow flocculent precipitate ; the filtered liquid is 
still very yellow, but on the addition of ammonia it 
deposits some more yellow precipitate, and then appears 
colourless. With protosulphate of iron it turns of a 
greenish colour, but on standing exposed to the air the 
colour changes to a dark green, whilst a dark green powder 
is deposited; the addition of ammonia now produces a 
dark brown precipitate, the liquid becoming colourless, On 
the addition of perchloride of iron it turns of a brownish- 
olive colour. Both the watery and the alcoholic solution 
give, with acetate of lead, a precipitate of a bright yellow 
colour, inclining to orange, which very much resembles that 
of chromate of lead; the filtered liquid in either case still 
retains some of its yellow colour. With basic acetate of lead 
the watery solution gives a precipitate of a rather darker 
yellow colour than that with neutral acetate, the filtered 
liquid being colourless. The watery solution when cold 
becomes, on the addition of acetate of copper, greenish- 
yellow, and remains clear, but on being boiled it deposits 
an abundant greenish-yellow precipitate, which dissolves 
again almost entirely when the liquid cools. The watery 
solution gives no precipitate with nitrate of silver, but on 
standing it becomes muddy and black, and deposits a fine 
black powder. On the addition of chloride of gold it also 
soon becomes muddy, and deposits bright spangles of 
metallic gold; when caustic soda is added at the same 
time, the reduction takes place instantaneously, the gold 
being deposited partly as a black powder, partly as a 
metallic mirror covering the sides of the glass. Proto- 
chloride of tin produces in the watery solution a bright 
