Medicinal gases includes oxygen, carbon dioxide and nitrous oxide. Each example includes its formula, mol. wt., chemical properties, uses, storage and precaution.

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Presented By: Priyanka N.Deshmukh
M.Pharm(Q.A)

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 Definition
• Inhalants are the gaseous substances which are, or may be, taken into
the body by way of the nose and trachea (through the respiratory
system).
Examples:
• Oxygen
• Carbon dioxide
• Nitrous oxide
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Oxygen
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• Contains not less than 99.0% v/v of O2.
• Colourless gas without an odour and
taste.
 Solubility:
• Soluble in water and alcohol at normal
temp. and pressure.
• Oxygen gas can be liquefied at low
temperatures and under high
pressure.
• On further cooling to -219ºC, it
forms a blue solid.
• Slightly heavier than air.
• Oxygen is chemically an extremely
active element.
• It combines directly with almost all
elements (except inert gases,
halogens and gold) to form their
oxides.
Formula : O2 Mol. Wt. 32.0
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Reactions:
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1. With non metals
C + O2 CO2 (carbon dioxide)
S + O2 SO2 (Sulphur dioxide)
4P + 5O2 2P2O5 (Phosphorus pentaoxide)
2. With metals
2Mg + O2 2MgO (Magnesium oxide)
3Fe + 2 O2 Fe3O4 ( Ferroso - ferric oxide)

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• Other metals like zinc ,potassium, sodium, lead etc. also burn in oxygen forming
oxides.
• Oxygen supports combustion. This property of oxygen is used to identify it
namely a glowing splinter introduced into a vessel filled with oxygen ignites and
burns with a bright flame.
Uses:
1. Required for respiration of human beings.
2. As a therapeutic and medicinal gas in patients suffering from respiratory
diseases and gas poisoning.
3. It is valuable in the treatment of carbon monoxide poisoning.
4. It is used as a diluent of volatile and gaseous anaesthetics.
5. It is used in circulatory failure associated with conditions such as myocardial
infarction or after cardiac arrest.

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Storage:
 Store under compression in metal cylinders.
 The cylinders of oxygen are painted black with a white
shoulder
( International colour code).
 The name and symbol of oxygen should be stencilled in paint
on the shoulder of the cylinder and clearly and especially
stamped on the cylinder valve.
Precaution:
Any fire or spark is highly dangerous in the presence of
increased oxygen conc. especially when oxygen is used under
pressure.

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Carbon dioxide
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Formula:CO2. Mol.Wt.:44.01
 Contains not less than 99.0% v/v of CO2.
 Colourless ,odourless gas.
 1.5 times as heavy as air.
 Soluble in water at normal temp. And
pressure.
 Its solution in water is weak acid.
 It liquefied by pressure at 31◦c or lower.
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1. It does not support combustion.
2. Magnesium ribbon burns in an atmosphere of carbon dioxide which gets
decomposed to carbon and magnesium oxide is formed.
2Mg + CO2 2MgO + C
3. A precipitate of barium carbonate is formed when carbon dioxide gas is
passed through a solution of barium hydroxide
Ba (OH )2+ CO2 BaCO3 + H2O
This is an identification test of carbon dioxide.
Chemical properties

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Uses
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1. Important for regulating the acid base balance of the
blood and tissues.
2. Used as a respiratory stimulant.
3. Now a days, it is seldom used as respiratory
stimulant.
4. Used in carbon monoxide poisoning.
5. Frozen form of carbon dioxide ,dry ice has been used
in the treatment of skin disorders like acne, angiomas,
corns ,eczema ,moles ,psoriasis and warts. Hence it is
used to destroy the tissue by freezing it.

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 Storage:
 Store under compression in metal cylinders.
 The gas is usually supplied in metal cylinders, painted grey.
 The name or the chemical symbol “CO2” should be stencilled in
paint on the shoulder of the cylinder and clearly.
Precaution:
1. Carbon dioxide should be used with caution in respiratory
obstruction and in pulmonary oedema ,because the carbon dioxide
tension in the blood is already high and the enhanced respiratory effort
may cause or increase pulmonary oedema.
2. Patients with respiratory depression do not respond to carbon
dioxide.
In the anesthetised or narcotised patients ,coma may follow inhalation
of carbon dioxide having concentration as low as 5 % in oxygen.

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Nitrous oxide
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 Formula: N2O
 Mol. Wt. 44.02
 Contain not less than 99.0% v/v of N2O.
 Colourless, odourless or almost odourless gas.
 Heavier than air.
 Characteristics sweetish taste.
 It liquefies at 88ºc.
Solubility:
 Soluble in alcohol ,fats and oils.
 Readily soluble in water.
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At high temp. it decomposes as
N2O N2 + (O)
With nitric oxide (NO), it does not produce brown fumes of NO2 as
produced by oxygen.
 Nitrous oxide is a non poisonous gas and when inhaled for
sometime , it produces nervous excitement and hysterical laughter,
hence it is known as laughing gas. But if inhaled for more time it
produces unconscious ness and insensitivity to pain.
Storage:
 Stored in metal cylinders at a temp. not exceeding 36ºC in a special
room free from inflammable materials.
 The cylinder should be painted blue. 12

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Uses:
1. Used as a general anaesthetic (Inhalant).
2. Weak anaesthetic but strong analgesic action.
3. Produces muscle relaxation.
4. Used as an anaesthetic in minor dental and surgical operations.
5. Used as propellant in aerosol pack.
6. Used for induction and as a vehicle for or as an adjuvant to other anaesthetics.
7. Nitrous oxide 50% with oxygen is widely used for analgesia especially in
obstetrics.
Precaution:
 Hypoxic anaesthesia is dangerous and nitrous oxide should always be
administered with oxygen.
 Nitrous oxide diffuses into gas filled body cavities and therefore it should be use
cautiously in patients with abdominal distension and pneumothorax.