40 
This Bromide heated with potassic Hydrate yielded Ali- 
zarate of Potassium : 
C,,H,Br,0, + 4 KOH = C,.H,K,0, + 2 KBr + 2 H,0. 
This Alizarate may be decomposed by Acids by which a 
flocculent yellow precipitate is formed, which is Alizarine, 
C,,H,O,. The following graphic formula may represent its 
constitution for the present. 
HOC—CH=C—CH=C—CH=co 
I | | = 
HOC—CHo—6—GH—¢=CH—6o 
Alizarine. 
Science had thus presented to the world for the first time 
an artificial method of preparing a natural dye-stuff ; but in order 
to make the process practically applicable some cheaper sub- 
stitute for the too expensive Bromine had to be found. This was 
discovered in Sulphuric Acid which gives with Anthraquinone 
Disulphoanthraquinonic Acid C,,H,(SO,),0,. With caustic 
Potash this yields Sulphite and Alizarate of Potassium, by a 
reaction similar to that by which the Bibromide of Anthra- 
quinone is converted into the Potassium Salt of Alizarine. 
After this theoretical disquisition the speaker dwelt on the 
question of the identity of artificial and natural Alizarine and 
gave a brief summary of the opinions arrived at by prominent 
European chemists. The attention of the Lyceum was called 
to the fact, that a Potassic solution of the artificial Alizarine 
exhibited had a very sheht purplish tinge compared with a 
similar solution of the product obtained from madder, which 
was also shown. ‘The colors obtained from artificial Alizarme 
are as fast and far brighter than these obtained from madder. 
The speaker concluded by pointing out the consequences 
which the introduction of artificial Alizarine as a substitute 
for madder would be likely to produce in the art of dyeing 
and printing cloth and the difficulty which at present seemed to 
render unprofitable its manufacture on a large scale, namely 
a limited supply of Anthracene, saying that it would be well 
for American chemists to examine our natural bituminous and 
