Assertion: picric acid | /r/CreatedBy | natural resin
Facets:
Source sentences:
text: Initially, it was made by nitrating substances such as animal horn, silk, indigo, and natural resin, the synthesis from indigo first being performed by Peter Woulfe in 1771.
text: Initially, it was made by nitrating substances such as animal horn, silk, indigo, and natural resin.