sulfur black

Y: Right, but the thing is, when the bismuth combines with the trace amounts of sulfur in your saliva and in your gastrointestinal tract, it reacts to form a black substance called bismuth sulfide.

Y:嗯。但是，铋与唾液和胃肠道中微量的硫作用会生成一种黑色的物质——硫化铋。

互联网摘选

Hydrogen, oxygen and sulfur on the surface of carbon black form surface functional groups and control chemical properties in carbon black.

炭黑含有氢、氧及硫等元素，它们基本上位于炭黑表面，形成具有化学活性的表面官能团，决定了炭黑的化学性质。

互联网摘选