Medicinal Gases: Carbon dioxide, Nitrous oxide, Oxygen | Pharmaceutical Chemistry

Medicinal gases are preparation that are used for patient diagnosis and treatment in emergency circumstances.

Therefore, the requirement for medical gas preparation is crucial for us in both medical and experimental settings.

The therapeutic gases include oxygen, nitrous oxide, nitrogen, and many others; these gases are typically administered to patients prior to, during, and following operation, as well as to patients in case of emergency.


Chemical formula- O2.

Molar mass: 32 g/mol

It contains not less than 99.0% of v/v of O2

Introduction –

  • Dioxygen, with the formula O2, is the form of oxygen that can be found in gases.
  • The majority of aerobic living creatures on earth depend heavily on oxygen.
  • In case of many diseases and intoxication, intereferin with normal oxygenation of blood or tissues, oxygen therapy is required.

Laboratory it is prepared by:

  • Hydrogen peroxide is easily broken down into water and dioxygen by catalysts like finely divided metals and manganese dioxide,

2H2O2(aq) heat → 2H2O(l)+O2(g)

2KClO3 →2KCl + 3O2

  • In the industrial setting, carbon dioxide and water vapour are first removed from the atmospheric air to yield dioxygen. The remaining gases are then liquefied and fractionally distilled to yield dinitrogen and dioxygen.


  • It is a tasteless, odourless, and colourless diatomic gas.
  • Solubility – It easily dissolves in water.


  • The majority of surgical and emergency situations use oxygen to meet the body’s oxygen requirements.
  • It is used for treating hypoxia.
  • It is used in anaesthesia.
  • It is used for treating carbon monoxide poisoning
  • In the COVID pandemic, hospitals and nursing homes use oxygen the most to treat patients.


• Under environmental conditions, oxygen is stored in an oxygen cylinder constructed of steel and aluminium alloys.

• Because oxygen is highly reactive with flammable materials, it should be stored away from them.

Carbon dioxide

Chemical formula- CO2

Molar mass- 41.01 g/mol


On commercial scale it is prepared by lime stone heating.

CaCO3(s) → CaO(s) + CO2(g)

Property of CO2

  • It is a heavy, colourless, odourless gas with a faintly acidic taste.
  • It can be obtained as a solid in the form of dry ice
  • It is available as dry ice, which is a solid.
  • It has a flavour that is slightly sour and is odourless.
  • It is less soluble in water.

Chemical Property

When carbon dioxide is dissolved in water, carbonic acid is produced. When combined with sodium hydroxide, this carbonic acid produces sodium bicarbonate.

Pharmaceutical Formulation

Medical gas

Market Preparation

Carbon dioxide

Storage Conditions

  • It is stored and supplied in metal cylinders in compressed form.
  • Storage temperature will not exceed 125°F (52°C)


  • It is inhaled to be used as a respiratory stimulant which stimulates the respiratory and cardio accelerator centres.
  • Mixture of carbon dioxide and oxygen are used for treating carbon monoxide poisoning.
  • It is used as replacement solvent in the pharmaceutical industry.
  • It is also used as pH controller in the water.
  • It is also used in the soft drinks preparation.


36) Which among these are used as respiratory stimulants? (Pharmacist Exam MPPEB, MP 2017)

1. Carbon dioxide with 5 to 7 percentage of oxygen

2. Nitrogen with 5 to 7 percentage of oxygen

3. Helium with 5 to 7 percentage of oxygen

4. Carbon monoxide with 5 to 7 percentage of oxygen

Ans:- 1 (Carbon dioxide with 5 to 7 percentage of oxygen)

Nitrous oxide

Chemical formula-N2O
Molar mass- 44.03 g/mol

  • Nitrous oxide contains not less than 99.0% v/v of N2O. It is also known as laughing gas because if inhaled an exhilarating/ exciting effect is produced.
  • It is used as anaesthesia during surgical process because it provide the pleasure or excitement sensation.

Physical Properties

  • It is a colourless, non-flammable gas, with a pleasant and slightly sweet odour and taste.
  • It is insoluble in water

Chemical Properties

  • At low temperature (about 600°C), it dissociates into nitrogen and oxygen.
  • Sulphur and phosphorus burn in its atmosphere.
  • It reduces to nitrogen when passed over red hot copper


Nitrous oxide is prepared by heating

  • A solutions of ammonium nitrate acidified with HCL
  • Lead nitrate
  • Ammonium nitrite

NH4NO3 → N2O + 2H2


  • It is used as anaesthesia during surgical process.
  • It is used as oxidant for organic compounds.
  • Mixture of oxygen and nitrous oxide in 65:35 ratio is used in myocardial infarction.
  • It is used as a good analgesic. In low concentration, it reduces the sensitivity of pain.
  • In high concentration, it has a stimulating effect on the nervous system as it is a laughing gas

Storage condition

  • It is stored and supplied in metal cylinders.

Medicinal Gases MCQ

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