We know they smear a liquid on the tube, but we don't know where they secrete it from or what its chemical composition is.

我们知道它们在管上涂抹了一种液体，但我们不知道它们从哪里分泌出这种液体，也不知道它的化学成分是什么。

The Saussurea involucrata chemical composition was: alkaloid, flavanone, sterol, volatile oil, 16 kind of amino acids, Saussurea involucrata lactone and so on.

雪莲化学成分为：生物碱、黄酮、甾醇、挥发油、16种氨基酸、雪莲内酯等。

This is a chemical composition.

这是化学合成物。

He's doing research into the chemical composition.

他正在研究植物的化学成分。

Long ago, people did not investigate the chemical composition of stones.

很久以前，人们对宝石的化学成分没有研究。