90 
alkali at the temperature of fusion alizarine is regenerated. 
Methyl-alizarine does not dye mordanted cloth when tried in 
the usual manner. It imparts hardly any colour to the 
mordants, and differs, therefore, in this respect fi’om the 
parent substance more than in any other. 
Though methyl-alizarine differs in most points very 
widely from anthraflavic acid, still the two substances are 
found to resemble one another as regards some of their pro- 
perties, Both yield crystallised potassium and sodium 
compounds. Both are converted into alizarine by the action 
of fusing potassic hydrate, though both remain unchanged 
when treated with strong alkaline lyes. The action of both 
on the spectrum is very similar. Neither of them is preci- 
pitated from its alcoholic solution by acetate of lead. Both 
are incapable of dyeing mordants. 
The analysis of methyl-alizarine gave numbers corre- 
sponding with the formula Ci 5 H 10 O 4 . It is therefore aliza- 
rine in which one atom of hydrogen is replaced by methyl. 
It still remained to determine how this substitution takes 
place, whether it is one of the two hydroxyl atoms con- 
tained in alizarine the hydrogen of which is replaced by 
methyl, or whether the substitution is effected in a different 
manner. In the former case methyl-alizarine would con- 
tain only one atom of hydrogen replaceable by metals. The 
formula of methyl-alizarine being Ci4H 6 (H0)(CH 3 0)0 2 , 
that of the potassium compound, for instance, would be 
C 14 H 6 (K0)(CH 3 0)0 2 and it would contain by calculation 
13*3 per cent of potassium. Now the potassium compound 
prepared in the manner just described and dried first over 
sulphuric acid and then at 130° C., was found to contain 
126 per cent of potassium. It is certain therefore that 
methyl-alizarine belongs to the class of compound ethers, 
being formed by the replacement of one of the hydrogen 
atoms of a bibasic acid by methyl. It has a similar com- 
position to Mr. Perkin’s diacetyl-alizarine. In the latter 
