73 | CORNUS FLORIDA. 
periment, was found to possess an intensely bitter 
taste with astringency, of a clear red colour, and 
turning to a deep, black on the addition of iron. 
On evaporation, it yielded.a drachm and an half of 
residuum.—Dr. Walker attempted to ascertain the 
quantity of resin by macerating the alcoholic ex- 
. tract, in repeated portions, of sulphuric ether. 
The ether acquired a dark colour and a bitter 
taste, and was found to have dissolved three quar- 
ters of the extract. When tested with iron, it was 
found that the remaining quarter only was chang- 
ed to a black colour. | 7 
_ The Cornus florida is one of the many vege- 
tables which, by the union of their gallic acid with 
the salts of iron, form a black compound, applica- 
ble to the purposes of ink. The constancy of 
the black colour thus produced varies greatly, ac- 
cording to the substance from which the gallic. 
acid is derived. It is often extremely fugacious, 
sometimes fading in a few days, and at others be- 
coming indistinct after some weeks or months. 
Considering the very great importance of the pur- 
poses for which ink is employed, and the immense 
evils which may result from its obliteration in writ- 
ings intended for permanency ; it is with extreme 
caution that we should recommend the introduction 
of any change in the mode of its formation, The 
