248 



The above facts are in further harmony with the foregoing 

 conclusions regarding cause of colouration effects and relative 

 differences. 



Dilute aqueous extracts of two samples of red logwood and of 

 one medium grade " bastard" wood all showed a similar yellow 

 colour, by transmitted light. The shades of colour did not differ 

 noticeably except in degree. In stronger extracts of equal con- 

 centration the first two appeared more reddish. 



Treatment with alkalies, volatile and non-volatile, turned the 

 colour of the red logwood extracts to a blood-red, passing into 

 purple whereas in the bastard extract the shade of yellow was 

 merely deepened, passing into the dull brown colour of faded oak 

 leaves. Dilute and concentrated mineral acids turned the yellow 

 of the dilute aqueous extracts of the red wood into a colour ranging 

 from orange to bright red. In the "bastard" extract no such 

 change was perceptible. 



These differences in the behaviour of the two sets of aqueous 

 extracts toward acids and alkalies correspond to the differences 

 between the reactions exhibited toward the same reagents by a 

 freshly prepared solution of the commercial "extract of logwood," 

 and a solution four weeks old that had faded to a straw-yellow. 



The chemical alterations undergone by the aqueous solution of 

 the commercial extract are accompanied by such a decided change 

 in colour and in chemical properties that from a comparative study 

 of such extracts we expected to learn something definite regarding 

 the actual differences between the pigments in the heart-wood of 

 " red" logwood and in that of the bastard variety. We were 

 unable, however, to do so. 



Experiments were started to determine, if possible, the relations 

 of light and of air to the discolouration of solutions of logwood 

 extracts. In a few weeks all the preparations had been attacked 

 by growths of PoiiciUium, Rhizopus and other fungi. After filtra- 

 tion the solutions showed no appreciable differences in shade or 

 colour. But on diluting these filtered solutions with two parts of 

 water and eventually with eight parts, differences were readily 

 observed. 



The solutions which had been in the light showed no change in 

 colour, whereas those kept in the dark had become distinctly yellow. 

 The extracts to which the air had free access manifested the 

 greatest changes. 



Solid matter in logwood extracts. — We desired to ascer- 

 tain, in comparative determinations, the quantities of solid matter 

 in aqueous extracts of the various logwoods under investigation. 

 The absolute amount of solid substance in 100 c.c. of the extract 

 was always small — less than 0*02 gram. In the drying process 

 slight decomposition seemed to result and perfectly constant 

 weights could be obtained only after a long time. Although the 

 absolute changes in weight were only very small, the proportion- 

 ate variations in quantities so slight were quite large. For these 



