135 
several of the rubiacine class of colouring matters, sub- 
stances which are contained in madder along with alizarine, 
that my curiosity was excited. Having communicated this 
fact to Mr. Perkin, who, as is well known, is engaged in the 
manufacture of alizarine on a large scale, he kindly sent me 
for examination a specimen of the residue obtained by him 
in evaporating the mother liquors of alizarine. This residue 
was a crystalline, reddish-brown mass soluble in alkalies, 
with a cherry-red colour. I found it to contain in addition 
to alizarine a quantity of a substance apparently identical 
with that I had previously obtained directly from anthra- 
cene. I afterwards found the same body in commercial 
alizarine, both in that manufactured by Mr. Perkin and in 
a sample from a continental firm. I therefore requested 
Mr. Perkin to supply me with a quantity of his alizarine 
sufficient to enable me to prepare a pure specimen of this 
body, a request to which he very kindly acceded. 
This alizarine, which was a yellow, almost amorphous 
powder, was in the first place treated with dilute caustic 
soda, in which it dissolved for the most part, yielding a dark 
purple solution. A small quantity of a pale yellow powder 
was left undissolved, which was filtered off, washed, dried, 
and heated, when it yielded crystals of anthraquinone. To 
the purple liquid there was added an excess of acid, which 
produced a bulky brownish-yellow precipitate. This was 
filtered oft and treated with boiling alcohol until the whole 
was dissolved. The alcohol on cooling deposited a quantity 
of almost pure alizarine in small mica-like scales. The 
mother liquor of course contained alizarine, and in order to 
separate it acetate of lead was added, which gave a bulky 
purple precipitate of the lead compound of alizarine. The fil- 
tered liquid, which had a dark yellow coloui', was evapo- 
rated, when it left a yellowish-brown residue, consisting for 
the most part of the yellow colouring matter or acid. In 
order to separate the latter from the impurities accompany- 
