Drugs of Mineral Origin

 Chapter-23 

Drugs of Mineral Origin

INTRODUCTION

• The substances of mineral origin have been used for various pharmaceutical purposes ranging from therapeutic agents to nutritional supplements to pharmaceutical excipient.

• These inorganic substances are found as mineral deposits of different types such as terrestrial deposits or fossil deposition of geological origin in ocean and seabeds. The natural ores or minerals are collected by mining in open quarries, and the product is further purified for various pharmaceutical uses. Some important natural drugs of mineral origin are given

KAOLIN

• Synonyms

Source

• Kaolin is a purified native hydrated aluminium silicate free from gritty particles. It is obtained by powdering the native kaolin, elutriating and collecting the fraction, which complies with the requirements of particle size. The native clay is derived from decomposition of the feldspar (potassium aluminosilicate) or granite rock and contains silica (47%), alumina (40%), and water (13%).

History

• The word kaolin was derived from the Chinese word ‘Kau-ling’, meaning high ridge. Kaolin was first mined in colonial days in Georgia and then shipped to England. Georgia was the source of clay for famous Wedgwood Pottery, and this resulted in the end of mining in Georgia for over a century. By 1876, mining here was resumed and today it continues as the major mineral production of the state by producing 72% of the total kaolin.

Collection and Preparation

• Kaolin is mined from the surface layer of stones, clay and sand which are in depth up to 100 feet. The average thickness of clay varies from 12 to 15 feet. Kaolin is removed by firing a high-pressure water jet at the quarry face. The clay is then sifted and refined to remove impurities before finally being dried to reduce its moisture content. The impurities like sand are removed by washing where the impurities settle down and the slurry is then pumped into a long channel of drags. The coarse particles in the slurry settle down, whereas the lighter ones move slowly along with water and flow into a settling pits, where the clay is deposited.

Description

• Kaolin is white soft plastic clay composed of well-ordered kaolinite with low iron content. In many parts of the world, it is coloured pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow or light orange colours also. It is made up of a loose aggregation of randomly oriented stacks of kaolinite flakes, smaller packets and sheaves and individual flakes.

• The median particle size of kaolin is 0.78 μ, l.02 μ, 1.1 μ, 1.2 μ and 3.8 μ. It has loose bulk density of approximately 25 lbs./cubic feet and packed bulk density of 46 lbs./cu ft, the hardness factor is 6.0, specific gravity: 2.6 g/cc, pH: 6.0, surface area: 10–29. Odorless when dry but has clay like Oduor when wet. Kaolin when treated with concentrated HCl, decomposes partially but on heating it with conc. sulphonic acid, it is converted into insoluble silica and aluminum sulphates.

• There are two types of kaolin: coarse (heavy) and colloidal (light). The coarser kaolin when treated with water forms a plastic and slightly sticky mass while colloidal kaolin with water forms sticky, stiff mass and if suspended in water forms a turbid solution or slurry. The standard grades of kaolin available are: calcined, Sanitary ware grade, tableware grade, and porcelain grade.

Chemical Constituents

• Chemically kaolin is anhydrous aluminium silicate with a chemical formula: Al2 O3 2SiO2 2H2 O or H4 Al2 Si2 O9 . The percentage composition are as follows: silicon dioxide (wt %): 56.91, iron oxide: 0.93, titanium dioxide: 0.54, aluminium oxide: 39.68, calcium oxide: 0.16, magnesium oxide: 0.16, sodium oxide: 0.60, potassium oxide: 0.60, and water: 12.6. Natural kaolinite usually contains small amounts of uranium and thorium, octahedral sheet of alumina octahedral.

Identification

• Heat kaolin on charcoal black with cobalt nitrate, it forms blue mass due to alumina.

Uses

• It is used as an adsorbent by oral administration, in the treatment of enteritis, dysentery and in alkaloidal and food poisoning. It is also applied externally as a dusting powder and also as clarifying agent during the filtration. Mostly, light kaolin with a particle size less than 10 μ is used in pharmaceutical preparations. Heavy kaolin with particle sizes up to 60 μ is only used in the preparation of kaolin poultice.

• It is used as filler in paper, rubber, ceramics, cement, and fertilizer industries. It is used in anticaking preparations, cosmetics, insecticides, paints, and as source of alumina.

ASBESTOS

Source

• Asbestos is a naturally occurring mineral which differs from other minerals in its crystal development. The crystal formation of asbestos is in the form of long thin fibers.

Geographical Source

• Asbestos deposits can be found throughout Ough out the world and are still mined in Australia, Canada, South Africa, and the former Soviet Union.

History

• Over the years, asbestos had many uses. Its primary use is as an insulator or fire retardant, but can also be used as a binder. Due to this versatility, asbestos can be found in many types of building materials. Even though the federal government placed a moratorium on the production of most asbestos products in the early 1970s, installation of these products continued through the late 1970s and even into the early 1980s.

Description

• On the basis of the crystalline structure, asbestos are divided into two mineral groups, as serpentine and amphibole. The amphiboles, in their fibrous form are friable and so are the most carcinogenic, Serpentines have a sheet or layered structure, whereas amphiboles have a chain-like structure. Chrysotile (A, B) is the most common type of asbestos among serpentine group. There are five types of asbestos in amphibole group and they are: Amosite, Crocidolite, Anthophyllite, Tremolite, and Actinolite.

• Chrysotile or white asbestos is obtained from Canadian serpentine rocks. It is commonly used in industries. As it is less friable it is less likely to be inhaled. One of the formula given for Chrysotile is Na2 Fe2+ 3 Fe3+ 2 Si8 O22 (OH)2 .

• Amosite is also known as brown asbestos or Grunerite is an amphibole from Africa and the formula given for Amosite is Fe7 Si8 O22(OH)2 .

• Crocidolite or blue asbestos is amphibole from Africa and Australia. It is considered to be most dangerous type of asbestos and the formula given for Crocidolite is Na2 Fe2+ 3 Fe3+ 2 Si8 O22(OH)2 .

• Anthophyllite, Tremolite, and Actinolite have their formula (Mg, Fe)7 Si8 O22(OH)2 , Ca2 Mg5 Si8 O22(OH)2 , Ca2 (Mg, Fe)5 Si8 O22(OH)2 , respectively. They are less used industrially but are found in a variety of construction materials and insulations and also in some consumer products, such as talcum powders.

Chemical Constituents

• It is a double silicate of calcium-magnesium with little amount of iron which gives colour to asbestos.

Uses

• It is used as filtering medium for caustic Alkalies, for bacterial filters, heat resistant insulators, proof gloves, break lining, and fire-proof clothing.

TALC

Synonym

• French chalk, Talcum.

Source

• Talc is a mineral with perfect cleavage and soapy feel, which occurs as foliated to fibrous masses and sometimes 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 Oduor.

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 H2 Mg3 (SiO3 )4 or Mg3 Si4 O10(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 mix 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.

• 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.

BENTONITE

Synonyms

• Wilkeite.

Source

• Bentonites are clays composed of very fine particles derived usually from volcanic ash. It is chiefly composed of the hydrous magnesium-calcium-aluminum silicate called montmorillonite.

History

• Bentonite, whose name derives from its type locality (San Benito County, California), is a blue plicate mineral, found in hydro thermally altered serpentinite. Bentonite fluoresces under ultraviolet light, appearing light blue in colour.

Geographical Source

• It is found in Brazil, France, Britain, Germany, India, Australia, Japan, China and in the United States (California, Georgia, Florida etc.). Bentonite is the official state gem of California.

Description

• Bentonite occurs slightly greenish grey or blue in colour. When observed under ultraviolet light it shows light blue colour. It is insoluble in water, HCl and H2 SO4 , it occurs as Tubular dipyramidal crystals and the hardness ranges from 6 to 6.5. Bentonite has a specific gravity of 3.6 and refractive index of 1.757–1.759; 1.802–1.804.

Microscopy

• Small quantity of bentonite when mounted in glycerin and observed under microscope shows minute Hexagonal crystals with 1 μ to 2.5 μ in size.

Chemical Constituents

• The chemical formula of bentonite is BaTiSi3 O9 (barium titanium silicate). Generally Bentonite occurs along with some unique set of minerals and the frequently associated minerals are natrolite (Na2 Al2 Si3 O10 2H2 O), albite (NaAlSi3 O8 ), neptunite [KNa2 Li (Fe, Mn)2 Ti2 Si8 O24], serpentine [(Mg, Fe)3 Si2 O5 (OH)4 ] and joaquinite [NaBa2 FeCe2 (Ti, Nb)2 (SiO3 )8 (OH, F) 1H2 O].

Identification Test

• Bentonite is mounted in cresol and observed on dark field polarized light, it shines brightly. 

• Bentonite acquires permanent red stain when treated with 1% solution of safranin in 70% alcohol. 

• When bentonite treated with 0.1% solution of methylene blue in absolute alcohol it takes deep blue colour. 

• Bentonite is first mounted in alcohol and then water is applied through its sides, the fragment of bentonite swells, disintegrates into small particles and forms a jelly like matrix.

Uses

• The hardness of bentonite makes it suitable for its use as a gemstone. It is also used as gel in ointment, in creams as a base, in lipsticks, depilatories and rouges. Highly absorbent bentonite is used for facing the moulds and preparing the moulding sands for casting metals. The less absorbent bentonite is used chiefly in the oil industry. Bentonite is also used as suspending and emulsifying agent and base for plasters.

FULLER’S EARTH

Synonyms

• Floridin, Multani mitti.

History

• The word Fuller’s earth is derived from the ancient process of cleaning or pulling wool to remove oil and dust particles with a water slurry of earth.

Source

• Fueller’s earth is mined in open quarry. It is a nonplastic type of kaolin, containing aluminium magnesium silicate.

Geographical Source

• It is found in Hampshire, Surrey, Somerset, Dorset, and Glaucestershine.

Description

• It is white to yellowish grey in colour, odourless and tasteless powder. If put into water, it swells and acquires nonplastic texture.

Chemical Constituents

• Fueller’s earth has the following approximate composition SiO2 55%; A12 O3 6%; CaO 3.5%; MgO 2.0%, Fe2 O3 6%; Water 10% representing montmorillonite 50% and silica 18%.

Uses

• It is used as decolourizer for oils and other liquids, as clarifying and filtering agent and for cleansing of woollen fabrics. Due to absorbent property, it is used in the preparation of dusting powders.

PREPARED CHALK

Synonyms

• Chalk, Creta, Paris-white, Whiting, English white. 

Source

• Chalk is a native form of calcium carbonate, freed from most of the impurities by elutriations. It contains not less than 97.0% w/w of calcium carbonate (CaCO3 ), when dried at 100°C.

Collection and Preparation

• Chalk is mined in open quarry, pulverized and then purified by elutriation. The water is removed and the insoluble chalk is settled forming flat cakes, known as ‘whiting’. It is purified further for pharmaceutical use.

Description

• Chalk is colourless, odourless, white earthy and soft to the touch. It is amorphous and insoluble in water. When reacted with acids, it effervesces.

Chemical Constituents

• It contains calcium carbonate (96%), magnesium carbonate (0.5%), 0.5–1.0% of silica, traces of iron, manganese, and aluminium oxides.

Uses

• Prepared chalk is used as an antacid, a dietary supplement, a dusting powder, and an antidiarrhoeal. It is used in face powders, and as an abrasive in tooth powders and toothpastes. It is also used in the manufacture of antibiotics and pharmaceuticals.

KIESELGUHR

Synonyms 

• Diatomaceous earth, celite supercel, industrial Earth.

Source

• It is a natural diatomaceous earth consisting of siliceous skeletons of fossils, family Baciliariceae (subdivision of the algae), purified by treating with dilute hydrochloric acid, washings with water and drying.

Geographical Source

• Huge quantity of this earth is available in West Germany, Denmark, Algeria, Kenya, United States. (California and Virginia), Scotland, and Ireland.

Preparation

• Kieselguhr is normally mined in an open quarry wherein large blocks containing moisture to the extent of 30–40% are arranged and air-dried. The blocks containing 5–10% of moisture are then pulverized to produce fine powder and subsequently graded. The powder is then subjected to acid treatment, washed thoroughly with water and finally dried.

Description

• Kieselguhr is a brownish-grey to white coloured light powder. It is odourless and tasteless. Kieselguhr is very smooth, adheres to the skin after rubbing. It. is not slippery; it absorbs moisture, but does not swell when mounted in cresol. It is invisible in polarized light with crossed nicols. Diatoms vary in size from 5 to 100 to 500 μ and exhibit two shapes: elongated and circular or triangular known as discoid.

Chemical Constituents

• Diatomite contains 75 to 90% of silica, 1 to 5% of aluminium oxide; calcium oxide (1.5%), magnesium oxide (1.5%) and iron oxide (5%).

Uses

• It is used as a filter aid, and for clarification and decolourization of liquids. It is used for the manufacture of tooth powder, face power, and nail polishes.

CALAMINE

Synonyms

• Prepared Calamine.

Source

• Calamine is an ore and chemically it contains zinc oxide with a small amount of ferric oxide and contains after ignition not less than 98.0% of zinc oxide.

Description

• It is an odourless, colourless powder, pink in colour and very fine. Calamine is insoluble in water and soluble in mineral acids.

Chemical Constituents

•  It contains 99% zinc oxide and 0.5% of ferric oxide. The colour of calamine is due to ferric oxide only. It should not contain calcium for pharmaceutical purposes.

Chemical Tests

• Mix 1 g of calamine in 10 ml of dilute hydrochloric acid and filter; to this solution, add ammonium supplied a white precipitate soluble in hydrochloric acid but, insoluble in acetic acid is produced. 

• Dissolve 1 g of calamine in 10 ml of diluted hydrochloric acid, boil, and filter. To the filtrate, add solution of ammonium thiocyanate; red colour is produced.

Uses

It is used topically as astringent and skin protectant. It is an ingredient of lotions and cosmetics.