26 REPORT—1846. 
from which they separate on cooling in yellow transparent plates and needles 
having a strong lustre. Alizarin prepared in this way .has the following 
properties :—It has a pure yellow colour without any admixture of red. It 
may be volatilized without leaving any residue. The vapour crystallizes on 
cooling in beautiful yellow plates and needles. Itsuffers hardly any change 
if exposed to the action of the most powerful reagents. It dissolves without 
change in cold concentrated sulphuric acid. Concentrated nitric acid hardly 
affeets it even on boiling. It is not changed by chlorine. It is insoluble in 
water, but soluble in alcohol with a yellow colour. It dissolves in alkalies 
with a beautiful purple colour. Its compounds with the alkaline earths are 
red and slightly soluble in water. Its compounds with the earths and metallic 
oxides are insoluble in water and exhibit different shades of red. It imparts 
no colour to cloth mordanted with acetate of alumina or oxide of iron, on 
account of its insolubility in water. Very little alizarin is obtained in this 
way; perhaps one 1 gr. from 1]b. of madder, though there is more of it con- 
tained in the root. 
I shall now shortly describe two other colouring matters which I have 
obtained from madder. If an extract of madder be made with hot or cold 
water, and a strong acid, such as muriatic or sulphuric acid, be added to the 
fluid, a dark reddish-brown flocculent precipitate is produced. This preci- 
pitate was separated by filtration and washed until the acid was removed. 
On being treated with boiling water, a part of it dissolves with a brown colour. 
On adding a few drops of acid to the filtered solution a dark brown pre- 
cipitate is produced, which seems to me to be a peculiar colouring matter 
similar in its properties to orcein, hematin and other soluble colouring 
matters. It dissolves in alkalies with a red colour, and is capable of imparting 
very lively colours to mordanted cloth. As far as 1 am aware it has not 
been described in the former investigations of this subject, though it seems 
to be the principal substance concerned in the production of the colours for 
which madder is used in the arts. I have however only examined it very 
slightly as yet. The residue left behind by the boiling water was treated 
with dilute boiling nitric acid, by which every trace of the preceding substance 
is destroyed, and the residue itself acquires a bright yellow colour and 
a more powdery consistence. This yellow powder contains alizarin, as is 
shown by its giving crystals of that substance on being gently heated; in 
fact it contains all the alizarin of the root, but mixed with another substance 
of an amorphous nature but very similar properties, from which it is difficult 
to separate it. By crystallising from alcohol no separation can be effected, 
as they are both about equally soluble in that menstruum. They also behave 
in a similar manner towards the alkalies, the earths and most of the metallic 
oxides. I have hitherto only succeeded in discovering one method of se- 
parating them, which is as follows :—The mixture of the two is dissolved ina 
little caustic potash. To the solution is added perchloride of iron, which 
produces a dark reddish-brown precipitate consisting of peroxide of iron in 
combination with the two substances. Now on boiling this precipitate with ~ 
an excess of perchloride of iron, the aljzarate of iron dissolves, forming a dark 
brown solution, while the iron ‘compound of the other substance remains 
behind. On adding muriatic acid to the filtered solution, the alizarin separates 
in yellow flocks and may be purified by crystallization from alcohol. The 
other substance, to which I have not yet given a name, is obtained by de- 
composing its iron compound, which remains behind on treating with per- 
chloride of iron, with muriatie acid, and washing till all the oxide of iron is 
removed. It seems also to be a colouring matter, as it dissolves with a red 
colour in alkalies and gives red compounds with the earths and metallic 
