A Chemical Substance with Unique Color - Violet Tungsten Oxide

Violet tungsten oxide is powder with unique color between dark purple and pure purple. It is generally prepared by calcining ammonium paratungstate in a rotary furnace. The color of violet tungsten oxide differs from different preparation methods.

Generally, violet tungsten oxide is obtained in a rotary furnace, using ammonium paratungstate (APT) as raw material. During the preparation process, a proper amount of NH₃ is introduced to slightly reduce tungsten oxide to WO_2.72. And furnace temperature, furnace tube speed and feeding speed are three important factors affecting the performance of violet tungsten oxide product. Some studies have shown that high furnace temperature, small feeding amount or long residence time in the furnace may cause more WO₂ phase produced in violet tungsten oxide product. This means that APT does not completely decompose intoW₁₈O₄₉. In a word, color of violet tungsten oxide is greatly affected by the product composition and the degree of APT decomposition.

According to specific preparation methods, color of violet tungsten oxide varies between dark purple and pure purple. Apart from violet tungsten oxide, are there any purple chemical substances? Here are some examples as following as:

1. Potassium Permanganate (KMnO₄)

The molecular formula of potassium permanganate is KMnO₄, and its molecular weight is 158.03400. Potassium permanganate is black purple crystal or particle with metallic luster. It is odorless. When contacted with some organic substances or oxides, it is prone to explosion. Potassium permanganate is widely used as oxidant, preservative, treatment agent, etc. Its aqueous solution may be purplish red.

2. Iodine (I₂)

Iodine is a purple black crystal, which was first discovered by a French pharmacist in 1811. It is easy to sublimate and coagulate after sublimation. It is toxic and corrosive. When meeting starch, iodine will turn bluish violet. This kind of substance is widely used in the preparation of medicine, dye, iodine wine, test paper and iodine compound. Iodine is purple in nonpolar solvent, and iodine vapor is purple as well.

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