safford: lignum nephriticum 509 



yellow and glowed with a decided fluorescence. With distilled 

 water neither the sapwood nor the heartwood produced fluores- 

 cence, as seen by ordinary sunlight; but this phenomenon was 

 distinctly visible when, at the suggestion of Dr. Arno Viehoever, 

 U. S. Department of Agriculture, these infusions were held in 

 the ultraviolet rays of a fluorescence lamp, and it was also dis- 

 played in ordinary daylight when a small amount of sodium car- 

 bonate or other alkali was added to the infusions of the wood in 

 distilled water. On boihng chips of the wood in tap-water for 

 several hours a deep amber-colored extract was obtained not un- 

 like Madeira wine in color. When placed on the table the surface 

 of this extract appeared to be outlined by a deep blue marginal 

 ring, and when held away from the light the fluorescence of the 

 liquid gave it the appearance of certain mineral oils. A drop of 

 the extract in a glass of water caused the whole glass to glow with 

 fluorescence when held in the rays of the sun admitted through a 

 hole in a screen. 



At a conversazione at the house of Dr. Alexander Graham 

 Bell, on the evening of January 6, 1915, at which the wood and 

 accompanying herbarium material were shown by the writer, 

 specimens of the infusion when exhibited by ordinary electric 

 light failed to show fluorescence; but afterwards, when held in 

 the rays of an arc hght the liquid glowed with an intense blue 

 which illuminated the faces of those standing near by. 



Experiments were made by Dr. Lyman J. Briggs, Biophysicist 

 of the Bureau of Plant Industry, with a view to determine the 

 possible value of lignum nephriticum as an indicator in titri- 

 metric determinations. The result of Dr. Briggs' observations 

 have not been published, but he recognized at once the advantage 

 which this, like other fluorescent substances, must have over 

 those indicators which show color changes only by transmitted 

 light, especially in testing dark liquids, in which the color of the 

 liquid masks the color changes of the indicator. Eysenhardtia 

 wood has one great advantage over fluorescein itself, from the 

 fact that its extract is readily soluble in cold water. With most 

 acids it does not fluoresce, but in the presence of acetic acid its 

 fluorescence is not destroyed. It cannot, therefore, be used as 



