REACTIONS OF LIGNIN. 79 



we place in a watery solution of aniline sulphate, when they at 

 once become bright yellow ; this colour is still more heightened 

 by the addition of dilute sulphuric acid. In place of phloroglucin 

 we can use an extract, prepared with water or spirits of wine, 

 from the wood of the Cherry, with almost the same result. If 

 sections of the fresh stem of the Pine, passing from cortex to pith, 

 are treated with strong hydrochloric acid, a yellow coloration of 

 the wood is at once produced, which, however, gradually gives 

 place from the exterior inwards, and from the interior outwards, 

 respectively, to a violet colour. This also is the phloroglucin 

 reaction, and indeed proceeds from phloroglucin which is derived 

 from the contents of the cortical cells and pith cells respectively. 

 Even the medullary rays of the young wood contain a little 

 phloroglucin, so that the violet colour also spreads from each of 

 these. If the sections pass through the cambium we can readily 

 see the gradual extinction of the lignin reaction in the neighbour- 

 hood of the cambium. 



If cross-sections of pine-wood are laid in Eau-de-Javelle, and 

 the action permitted for a suitable length of time, the lignin is 

 removed from the lignified membranes, and the cellulose left 

 behind will take the characteristic blue colour with chlorzinc 

 iodine. Similarly the lignin can be removed by Schultze's 

 maceration fluid. 



