Talc

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Chapter: Pharmacognosy and Phytochemistry : Drugs of Mineral Origin

Talc is a mineral with perfect cleavage and soapy feel, which occurs as foliated to fibrous masses and some times in coarsely granular, finely granular, or cryptocrystalline masses.


TALC

 

 

Synonym

 

French chalk, Talcum.

 

Source

 

Talc is a mineral with perfect cleavage and soapy feel, which occurs as foliated to fibrous masses and some times in coarsely granular, finely granular, or cryptocrystalline masses.

 

Geographical Source

 

It is found in Austria, Canada, United States (California, Montana, Texas, etc.), France and also in Italy.

 

History

 

The origin of the name Talc came from Persian through Arabic talc. India has also been successfully exporting talc to overseas. The Indian talc industry hopes to have joint venture partnerships with international business houses with technical proficiency in the beneficiation and sterilization of talc.

 

Description

 

It is folia which is slightly flexible and is not elastic. It has perfect basal cleavage. Talc is very soft and sectile in nature, with a hardness of 1. It is the softest known solid. Talc is translucent to opaque and has specific gravity of 2.5–2.9. The colour of talc ranges from white to grey to green. The lubricating property, high luster and low conductivity to electricity and to heat determine its industrial value. Talc is chemically inert, sparingly soluble in dilute mineral acid and insoluble in water. It has no taste and odour.

 

Microscopy

 

Talc powder when observed under microscope shows colourless, irregular, and sharply angular in nature.

 

Chemical Constituents

 

Talc composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2 and usually consist of small quantities of nickel, iron and aluminium as impurities. The variation of colour of talc to greenish or greyish tint indicates the presence of iron oxide.

 

Chemical Tests


Fuse about 0.5 g talc with 0.2 g each of anhydrous sodium carbonate and potassium carbonate in a platinum crucible. Dissolve the fused mixture into 50 ml of water and to it add hydrochloric acid and until it ceases to effervescence. Add little more acid and evaporate the contents to dryness on water bath. Cool it, dissolve in 20 ml of water, boil, and filter. To the filtrate, add about 2 g of ammonium chloride and 5 ml of diluted ammonia solutions. Remove the precipitate formed, if any by filtration. To the filtrate, add sodium phosphate, white crystalline precipitate of magnesium ammonium carbonate is formed.

 

2. Yields the reactions characteristic of silicate.


Uses

 

Talc is used as a cosmetic (talcum powder), as a lubricant, as a dusting powder for coating and dusting pills and as a filler in paper manufacture. It is used as astringent in baby powders for the prevention of rashes in area covered with dipper. Talc is used in making paper (as a filler), soap, lubricants, electrical insulation stoves, sinks. It is used as a filter aid for filtration and clarification of cloudy liquids.

 

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