78 transactions of the 



In 1827 Colin and Robiquet ubtained the true colouring principle 

 of madder tolerably pure. They called it alizarin, from the Levant 

 name for madder. 



In 1848 Schunck gave it the formula C^ Hjo O4. He found that 

 there was no trace of alizarin in the fresh root, but that in the cells 

 of the living plant there was a substance called rubian, which splits 

 up into sugar and alizarin by the action of a substance which exists 

 in the root. 



In 1850 Wolff and Strecker, by the formula they gave it, 

 imagined that it was closely related to naphthalene. AVe now know, 

 however, that their formula was wrong. 



In 1785 Hofmann obtained the calcium salt of quinic acid from 

 cinchona bark, and from this quinone can be obtained. Qui none, 

 Cg II4 0„, can be looked on as benzene, Cg Ho, in wiiich two atoms of 

 hydrogen are replaced by the dyad grouping, O",. 



In 1868 Carl Graebe saw that many other quinones could be 

 formed, and Graebe and Lieberman then looked on alizarin as a 

 derivative from a quinone, and to have the formula C^ Hg (O.) (HO),, 

 because they saw that it had many properties in common with other 

 quinones. They have been able to establish their view. Anthra- 

 quinoue was obtained from anthracene. It was then converted into 

 the bibromanthraquinone, C^ H^ Br, O'o. On boiling this with 

 potash at a high temperature, it became violet, and, on acidifying, 

 alizarin separated out in yellow flakes. Since bromine is expensive, 

 Perkin heats the alizarin with suipliuric acid thereby converting it 

 into sulpho-corapound, C^ He (HSO.,), o. From this the calcium 

 salt, Cu He Ca (803)2 O'o, is obtained ; then the solium salt, C14 H^ 

 (Na SOg), '2. This sulpho salt is then decomposed by caustic soda, 

 giving the sodium salt of alizarin C14 H^ (NaO), O",, and lastly from 

 this solution alizarin is precipitated by an acid, C^ H^ (HO). 3- 



Thus chemists have found a use for coal tar, saving hundreds of 

 acres of land, which can be devoted to the cultivation of other 

 products than madder. 



MEETING, February 12th, 1874. 

 The President in the Chair, 



The second meeting for the term was held in the Physical Lecture 

 Eoom. There were Thirty-one members and visitors present. 



The President acknowledged a donation of Abyssinian Drawings, 

 presented by H. E. Darley, (O.C.) 



G. H. Wollaston, Esq., Vice-President of the Society, then read a 

 paper upon " Nodules and Concretions." The President made some 

 remarks upon the subject of this paper. 



The meeting adjourned. 



A 



