Yellow Fever Vaccine: Slightly dull, light-orange colored, flaky or crustlike, desiccated mass.

Yohimbine Hydrochloride: White to yellow powder. Melts at about 295, with decomposition. Slightly soluble in water and in alcohol; soluble in boiling water.

Yttrium Chloride: Colorless, deliquescent crystals. Soluble in water and in alcohol.