Pharmaceutical Chemistry-1

1. GASES AND VAPOURS
TARIQUE FAHEEM
(ASSISTANT PROFESSOR)
RAJEEV COLLEGE OF PHARMACY

2. Overview
INHALANTS
ANAESTHETICS
RESPIRATORY STIMULANTS

3. INHALANTS
Official Gases: oxygen, carbon dioxide, helium, nitrogen
and nitrous oxide
Volatile vapours: ammonium compounds
Inhalants are the drugs or chemicals which in vapour
form are inhaled in the body.
E.g. official gases, Volatile vapours

4. (1) OXYGEN
 Physical properties: Colourless, odourless, tasteless gas
and Sparingly soluble in water
 Chemical properties: Highly reactive oxidizing agent
C + O2 CO2
S + O2 SO2
4 P + 5 O2 2 P2O5
2 mg + O2 2 MgO
3 Fe + 2 O2 Fe3O4

5. Preparation:
 a. Electrolysis of water
❑ Direct current is passed through a cell between electrodes
immersed in aq. solution of sod. or pot. hydroxide.
❑ Oxygen is liberated at the anode.
2 H20 O2 + 2 H2

6. b. Purified from atmospheric air
air is purified by removing dust
particles
Compressed into liquid air
Oxygen is separated by fractional
distillation

7. Assay
 Principle: Gasometric method
 Apparatus: Nitrometer
 Absorbing agent: NH CI and NH OH solution
 Sample of O2 is passed to this absorbing soln.
 NMT 1% of gas is left to be unabsorbed in the
tube.

8. Uses:
Treatment of hypoxia or anoxia
(lower level of oxygen in body)
Treatment of carbon monoxide
poisoning

9. Storage
 Stored in metallic cylinders, cool place
 Valves and tapes of cylinders should not
be lubricated with grees or oil.
 The shoulder of the cylinder is painted
white [as an international colour code]
and remaining part is painted black.
 Label and symbol of oxygen at shoulder.

10. ANAESTHETICS
An anaesthetic is a drug that causes
anaesthesia, which is a reversible loss
of sensation.
E.g- Nitrous oxide

11. (1) NIROUS OXIDE
❖Assay:
 Principle: Gasometric method
 Absorbing agent: liquid oxygen
 Sample (50ml) is allow to condense in
liquid oxygen at cool atm.
 Not more than 1.0% uncondensed gases
present in sample.

12. ❖Uses:
 As anesthetics, analgesic (relieving pain)
 Calming to exited mental patients
❖Storage:
➢ Stored in metallic cylinders
➢ The cylinder is painted blue
➢ Label and symbol of nitrous oxide at shoulder
➢ At cool place (below 37 °C)

13. RESPIRATORY STIMULANTS
Respiratory stimulants are the agent
which increases the activity of
respiration by CNS stimulation.
E.g. CO2, ammonia, Ammonium
carbonate, aromatic ammonia spirit

14. 1. CARBON DIOXIDE
 Physical properties: Colourless, odourless, faintly
acidic taste
 Soluble in water
 Solid CO, (dry ice) is white
 Chemical properties:
Forms carbonic acid in water (gives acidic taste)
C02 + H2O H2CO3

16. Preparation
From calcium carbonate

17. Assay:
 Principle: Gasometric method
 Apparatus: Nitrometer
 Absorbing agent: 50% KOH soutionn
 Sample of CO2 is passed to this KOH solution containing
nitrometer
 Not more than 1ml of gas is left in the tube if 100ml of
sample is taken.
CO2 + 2 KOH K2CO3 + H2O

18. Use:-
 At lower conc., used as respiratory stimulants and CVS stimulants
 High conc., cause respiratory depression Treatment of carbon
monoxide poisoning
Storage:
 Stored in metallic cylinders
 The shoulder of the cylinder is painted gray Label and symbol of CO2 at
shoulder
 At cool place

19. (2) AMMONIA
Physical properties:
 Colourless gas with strong pungent odour
 Very soluble in water
Chemical properties:
 Act as base in chemical reactions, accept proton or donate lone
pair of electron
Uses:
 Respiratory stimulant
 Preparation of strong (27% to 30% w/w) and dilute (10%w/w)aq.
 aq. ammonia solutions also used as antacid

20. Assay
 Principle: back titration
 Ammonia as an solution + NaOH
 Mixture is distilled
 Distillate is passed in to known volume of std acid.
 The excess volume of std acid is back titrated with
std alkali.
 Indicator: Methyl red

21. (3) AROMATIC SPIRIT OF AMMONIA
Synonym: Spirit of sal. Volatile
Content:
About
2% w/v of free ammonia
3% w/v ammonium carbonate
64-70% w/v of alcohol
lemon oil and nutmeg oil (added to improve flavour and taste)
Uses
Respiratory stimulant
Flavoring agent
Storage:Well closed container, in cool place.
Rubber stoppers are not used as they absorbed ammonia

22. THANK YOU