Erdmann on Hematoxylin. 447 



certain quantity of water and allowed to stand for some days, 

 when the hsematoxylin crystallizes out, and may be pressed 

 between bibulous paper, &c. The residual extract itself con- 

 tains more of the substance ; from 2 pounds of extract treated 

 with 10 pounds of aether, Erdmann obtained between 3 and 4 

 ounces of hematoxylin. 



The colour of haematoxylin varies from a straw yellow to a 

 deep yellow ; when pulverized it is white or pale yellow. The 

 crystals can be obtained some lines in length ; their form has 

 been studied by Wolff and previously byTeschemacher (Phil. 

 Mag. S. 3. p. 28). It tastes like liquorice root without any 

 trace of bitterness or astringency. Chevreul describes it dif- 

 ferently, but he probably had an impure substance. 



Haematoxylin dissolves slowly in cold water, but very easily 

 in boiling water. It is necessary to employ water which has 

 been previously boiled, for the smallest possible trace of am- 

 monia causes the haematoxylin to become purple, and Erd- 

 mann proposes this substance as the most delicate test for 

 ammonia : pure oxygen or air freed from ammonia does not 

 alter the colour. The crystals must be dried by pressure in 

 bibulous paper. The filtering paper which is used for the 

 solutions of haematoxylin must be free from lime. Haema- 

 toxylin is soluble in alcohol and aether, but the solution in 

 anhydrous aether does not yield crystals. By exposure to 

 sunlight the substance acquires a reddish colour, but no change 

 in its constitution is effected. 



It does not sublime, leaves behind a great quantity of char- 

 coal when heated in a tube ; does not evolve ammonia when 

 heated with potassa, and consequently contains no nitrogen. 

 This haematoxylin loses water at ordinary temperatures, 

 and the desiccation is completed at 100-120° C. ; it contains 3 

 atoms of water, its formula is therefore C 40 H 34 15 +8 H 2 O. 

 Another hydrate containing only 3 atoms of water is ob- 

 tained by allowing a hot saturated solution of haematoxylin 

 to cool in a closed vessel, when it separates in small granular 

 crystals. It was impossible to determine the atomic weight of 

 the body. 



Caustic potassa colours a solution of haematoxylin violet, 

 but by absorption of oxygen the colour passes into purple, 

 brownish yellow, and at last dirty brown. These compounds 

 appear to contain haematoxylin in different degrees of oxida- 

 tion. 



Ammonia has the same effect, but the presence of air is 

 necessary to effect the change fully ; the ammoniacal solution 

 becomes deep red, almost black. If acetic acid be added to 

 this solution until a precipitate begins to be formed, and it be 



