Philosopher’s Wool | Zinc Oxide | ZnO


  • Zinc oxide
  • Oxozinc
  • Calamine
  • Zinc White
  • Chinese white
  • Flowers of zinc

Philosopher’s wool is chemically zinc oxide (ZnO) which is commonly known as Philosopher’s wool. It is an inorganic chemical compound. It is naturally found as a mineral zincite. It is mainly produced synthetically. It has applications as mild astringent and antiseptic action which works as a topical protectant.

Zinc is a naturally-occurring metallic element. Like other minerals, zinc also exists as a component of the building blocks of our body and is necessary for maintaining our normal health and metabolism.

It also helps in maintaining our immune, enzymatic systems and normal cell functioning. It is required for protein synthesis, collagen formation and skin healing.

Zinc and one of its various compounds, zinc oxide, have been used in medicinal and industrial applications for time immemorial.

Physical properties

Zinc white crystallizes mainly in two forms which are cubic zinc blende and hexagonal wurtzite as the unit cell. It is powdery in texture. The most common and stable structure under ambient conditions is wurtzite.

Zincblende (ZnS) can be stabilized by growing zinc oxide (ZnO) on substrates which has a cubic lattice structure. The oxide and zinc centers are tetrahedral.

Molecular Weight81.406 g/mol
Density5.606 g/cm3
Melting Point1,974 °C
Boiling Point2,360 °C
Refractive indexn1=2.013, n2=2.029
Magnetic susceptibility (Xm)−27.2·10−6 cm3/mol
Band gap3.3 eV
Physical properties of Philosopher’s wool or Zinc Oxide or ZnO

Chemical properties

The chemical formula of Philosopher’s wool or zinc oxide is ZnO.

  • It is white solid
  • Crude zinc oxide is yellow-grey in color
  • Exists as a granular Solid form
  • Insoluble in water
  • It has no characteristic smell
  • It is an amphoteric oxide
  • Dissolves in acids and alkalis

It can be dissolved in most acids, such as hydrochloric acid:

ZnO + 2 HCl → ZnCl2 + H2O

Solid zinc oxide will also dissolve in alkalis to produce soluble zincates:

ZnO + 2 NaOH + H2O → Na2[Zn(OH)4]


It is mainly synthesized in 4 ways:

  1. Wet chemical process
  2. Direct process
  3. Indirect process
  4. Laboratory synthesis

The ordinary white powder of zinc oxide can be prepared in the laboratory by electrolyzing a solution of sodium bicarbonate (NaHCO3) using zinc as an anode. In this process zinc hydroxide [Zn(OH)2] and hydrogen gas (H2) is produced. The zinc hydroxide on heating decomposes into zinc oxide (ZnO):

Zn + 2 H2O → Zn(OH)2 + H2
Zn(OH)2 → ZnO + H2O


It was used by early humans, in processed and unprocessed forms, as paint or medicinal ointment, but their composition. The use of Pushpanjan, probably zinc oxide, as a healing salve for eyes and open wounds, is described in the Indian Ayurveda (a natural system of medicine) medical text in the Charaka Samhita.

As a part of rituals, Alchemists would burn zinc in the air and collect the residue, which formed into white woolly tufts. They called it Lana philosophical in Latin, meaning Philosopher’s wool.

Uses of Philosopher’s wool

Philosopher’s wool has various applications in our daily life, nearly all of us had used it in some form. They have many health as well as industrial uses. It is also used as a food preservative to protect it from bacterial and fungal attacks.

Health uses

It has wide applications in health and health-related product manufacturing.

Zinc oxide Philosopher's wool products in market
Zinc oxide products available in the market
  • Treat skin diseases
  • Treat and prevent diaper rash
  • Treat dandruff
  • Baby lotions
  • Bath soaps
  • Foot powders
  • First aid tapes
  • Acne treatment
  • Used in dental cement
  • In pastes
  • In bandages
  • In sunscreens and sun lotions to protect the skin from harmful sun rays
  • In treating sunburn (suntan)
  • Antifungal additives in food (as nanoparticles NPs)
  • Zinc oxide nanoparticles are antibacterial (as nanoparticles NPs)

Those people allergic to ZnO should not use products made of zinc oxide. It may lead to skin irritation, redness of the skin, or worsening rashes.

Industrial uses

  • Used as a white pigment in paints
  • Manufacturing of rubber
  • Products of photocopying
  • Used in coating (as anticorrosive for metals)
  • Ceramic industry
  • Li-ion battery and supercapacitors
  • Piezoelectricity
  • Spintronics
  • Zinc oxide nanorod sensor
  • Electronics
  • Methane reforming
  • Glass
  • Cement
  • Lubricants
  • Batteries
  • Ferrites
  • Fire retardants
  • Corrosion prevention in nuclear reactors

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