This poisonous oil is colourless, although impure samples may appear yellow.

Typical impure samples are yellowish or even red-brown due to the presence of iron-containing impurities.

It is a white solid, but impure samples can appear yellowish.

Triphosgene crystals decompose at around 130 C, although, the decomposition temperature of impure samples can be much lower.

It is a colorless liquid, although impure samples can appear yellow.

They are colourless waxy solids, although impure samples may appear yellow.

But later William Crookes confirmed that the new element was only an impure sample of yttrium.

They show up in impure samples, making it hard even to determine their composition.

The compound itself is a colorless solid, but impure samples are often yellowish liquids.

The impure sample has lower specific activity because some of the mass is not actually enzyme.