FUSION

• “The process in which the solid or semisolid is converted into liquid by heating is called
as fusion.”
• Fusion is the process by which the solids gets converted into liquids without adding any
solvent. It may also be defined as the process of heating the solids until they melt.
• The fusion process is very important and is used for the preparation of following
substances;
• Fusion is done to purify certain solid and semisolid substances e.g. bees wax, hard paraffin,
soft paraffin and wool fat are heated to melt and filtered while hot, to remove the dissolved
impurities. On cooling, a product free from dissolved impurities is obtained.
• This method is also applied for the preparation of ointments when they also contain solids
and semisolids in the formulation.
• All the substances are melted and then cooled slowly with continuous stirring until a
uniform product is obtained. To avoid overheating substances with higher melting points
are melted first to' which substances with lower melting points are added.
• Fusion process is used in the manufacturing of ointments. (Semi solid, only for external
use) The compounds containing high melting point are fused or melted to form semisolid
ointments, which are used for the other body cavities than the oral cavity.
• The point at which the liquid starts converting into semisolid or solid is called as congealing
point.
• Process of fusion is used for the preparation of suppositories e.g. Theobroma oil solidifies
at 35°C.
• Salts are also prepared by fusion process, e.g. AgCl2 is prepared by the fusion of AgNO3
with HCl. Fused form of AgNO3 is used for the removal of warts on face and other parts
of the body.
• Binaural fusion, the cognitive process of combining the auditory information received by
both ears
• Binocular fusion, the cognitive process in binocular vision of combining the visual
information received by both eyes
• Cell fusion, a process in which several uninuclear cells combine to form a multinuclear cell
• Gene fusion, a genetic event and molecular biology technique

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 • Spinal fusion, a surgical technique used to combine two or more vertebrae
• Tooth fusion, a dental abnormality in which two teeth are joined
• Uses of Fusion Proteins
• Three of the most important uses of fusion proteins are: as aids in the purification of cloned
genes, as reporters of expression level, and as histochemical tags to enable visualization of
the location of proteins in a cell, tissue, or organism.
The proteins used most often as fusion partners for reporter constructs are β-galactosidase,
luciferase, and green fluorescent protein (GFP).
CALCINATION/ROASTING
• Calcination is the process in which the inorganic substances are strongly heated so as to
remove their volatile contents and a fixed residue is obtained.
• Calcination is also used to mean a thermal treatment process in the absence or limited
supply of air or oxygen applied to ores and other solid materials to bring about a thermal
decomposition.
• On laboratory scale calcination is done in silica or platinum crucibles where as in industries
metallic vessels are used.
• In process of calcinations the product are obtained by heating the substances especially
ores of minerals. The principle ores which can be calcinated are oxides, carbonates,
silicates, sulphites and halides of metals.
• The gases formed during roasting of ores especially sulphides, arsenic fumes etc.
• The ore is added into one end which is then shifted towards the fire and removed after 3
hours.
• , e.g.MgCO3 is roasted or calcinations give MgO.
• MgCO3 > MgO + CO2 Heat
• Fe2SO4 > Fe2O3+ SO2
• CuSO > CuO + SO2
• This process is used for manufacturing of inorganic compounds from natural sources e.g.
formation of MgO which are used as antacid.
• In calcination processes, solid intermediates and products are regularly handled in the fine
powder form (ex: kaolin or metakaulin).
• Calcination is an important step in the manufacture of cadmium pigments to achieve
particular pigmentary characteristics.

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 • Calcination is not just confined to inorganic pigments; organic pigments can also be
calcinated to improve their performance.
• This process is known to improve the chroma, tinctorial strength, pigmentary texture,
weather stability, light-fastness and thermal stability of pigment whereas it has adverse
effect on the dispersibility of pigments.
TRITURATION
• By triturating the grinding of a solid substances is done to fine powder by continuous strike
in or rubbing the particles in a mortar with a pestle.
• The term trituration is also emloyed to design the process by which two or more powders
are intimately mixed with each other.
• For this purpose a pestle and mortar made of, porcelain or glass is used.
• For hard materials steel mortar and pestle may be used.
• Trituration may be carried out with an ointment tile and spatula or using a mortar and
pestle.
TRITURATION (TILE & SPATULA)
• Small quantities of finely powdered solids may be mixed on a tile by means of a spatula.
• Tiles are usually made of glass and should be large enough for the quantity of powder to
be mixed or ointment to be prepared. Usually for small scale work 300mm square is a
useful size for a tile.
• Spatula is made of stainless steel except for the few medicaments those react with stainless
steel (iodine), should be flexible and long blade (25mm by200mm) to provide a large
rubbing surface.
• Powders for Trituration are placed on the tile and gently mixed until the mixture is smooth
and homogeneous, but in the case of ointment if base is very soft it may be helpful to warm
the tile but overheating should be avoided because the base will become too fluid and may
run off the edge of the tile.
• The dispersion is then diluted with increasing amount of base, doubling the quantity each
on the tile of each dilution. Finally any liquid ingredient is incorporated.
TRITURATION (PESTLE AND MORTAR)
• A mortar should be used when the quantities are too large.
• A mortar with a fairly flat base and a pestle with a flat head will give best results.
• It is impossible to ensure intimate dispersion of one powder in another by mixing the two
substances all at once.

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 • The purpose is to add a substance that is present in greater amount to the whole of the
substance present in lesser amount.
• Substance present in greater amount is introduced into the mixture in very small quantities
at first, but gradually increasing the quantities, until the whole of the substance has been
added.
• Used to purify crude chemical compounds containing soluble impurities.
• Medicinal substances often have to be processed before they can be potentized.
• This may be done by producing a solution or a mother tincture, or by triturating the
substance with lactose.
• Trituration results in a quantitative reduction in the drug substance by a qualitative increase
in its medicinal or therapeutic property.
• It is reasonable to hypothesize that trituration, which is the variable factor in the proposed
experiment, does, in some way, change the physical structure of the solvent even when the
order of dilution is beyond the Avogadro limit of molecular presence.
PULVERIZATION BY INTERVENTION
• This is the process of powdering a substance with the help of another substance, which can
be removed easily after the pulverization has been completed.
• Substances such as camphor, which are gummy and tend to re-agglomerate or which resist
grinding, can be powdered by this method.
• Camphor cannot be pulverized by trituration because the particles tend to cohere as quickly
as they are powdered. This difficulty is overcome by addition of a small amount of
alcohol/ether/chloroform during trituration.
• The solvent can be removed after pulverization process is complete, by spraying the
powdered camphor in a thin layer. Spermaceti wax may also be powdered in this manner.
Iodine crystals may be pulverized with the help of a small quantity of ether
• Used with hard crystalline powders that do not crush or triturate easily, or gummy-type
substances.
• The first step is to use an "intervening" solvent (such as alcohol or acetone) that will
dissolve the compound.
• The dissolved powder is then mixed in a mortar or spread on an ointment slab to enhance
the evaporation of the solvent.
• As the solvent evaporates, the powder will recrystallize out of solution as fine particles.
• Iodine crystals may be powdered with the help of small quantiy of ether.

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 DESSICATION
• Desiccation is the process of removing adhered moisture from liquid or solid substances.
• The term "desiccated" should be used for those substances from which water has been
completely removed.
• On laboratory scale desiccation can be carried out in a desiccator, which consists of a
tightly closed glass vessel containing a drying agent at its bottom, which absorbs moisture
from the substance being desiccated.
• The commonly used drying agents include concentrated sulphuric acid, phosphorous
pentoxide, exsiccated calcium chloride and silica gel.
• The drug to be dried is taken in a dish, which is placed inside the desiccator above the
surface of drying agent. For continuous operation the desiccator may sometimes be
connected to a vacuum pump.
• The substances which are very sensitive to moisture are formulated as tablets or capsules
which are further protected by enclosing them in sealed vials, on the bottom of which a
small cloth bag containing silica gel is placed which acts as a desiccant.
1. Desiccation helps in preserving the vegetable and animal drugs which get destroyed in
the presence of moisture.
2. Comminution of drugs is difficult if they are wet but if they are dry, can be easily
powdered.
3. Desiccation reduces the bulk and weight of the substances due to loss of adhering
moisture in them therefore they become easy to handle.
4. Stability of certain drugs is also increased.