Assertion: rubber | /r/HasProperty | mixed with litharge
Facets:
Source sentences:
text: These undesirable properties of natural rubber were not overcome until 1839, when American inventor Charles Goodyear (1800–1860), at the end of five years of constant experimentation, accidentally placed a sample of rubber mixed with sulfur and litharge (lead oxide, PbO) on a hot stove in Woburn, Massachusetts.