Nitrous oxide is produced commercially by heating ammonium nitrate to 240°C. The resulting gases are passed through a series of scrubbers to remove impurities like higher oxides of nitrogen, ammonia, and nitric acid, producing purified nitrous oxide. Nitrous oxide is then compressed and stored in blue cylinders at high pressure as both a liquid and gas. It is a sweet-smelling, colorless gas with anesthetic properties when inhaled above certain concentrations.

1. MODERATOR: DR.DOLLY SHARON
PRESENTER: DR.M.MADHU CHAITANYA
MANUFACTURING OF N2O
And REMOVAL OF ITS
IMPURITIES
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2. History
Prepared first by JOSEPH PRIESTLY in1772
Anesthetic properties first demonstratedby HUMPHERY DAVYin 1800
Used forpainless tooth extraction first by HORACE WELLS

3. Preparation of Nitrous Oxide
In the laboratory : Small amounts may be prepared by allowing iron to react with nitric acid.
{NO} is first produced ,but this is reduced to nitrous oxide by a excess of iron
2NO + Fe  FeO + N2O
Ammonium nitrate crystals heated to 240 degrees celsius
 Decomposition to nitrous oxide and water
Heat
NH 4 NO 3 =======> N 2 O + 2 H 2 O
240 deg. C
 N20 is chemically scrubbed 99.5% pure
 Stored in compressed form in metal cylinders
INTRODUCTION

4.  The decomposition of ammonium nitrate is also a common laboratory method for preparing
the gas. Equivalently, it can be obtained by heating a mixture of sodium nitrate &
ammonium sulfate
2 NaNO3 + (NH4)2SO4 → Na2SO4 + 2 N2O+ 4 H2O.
Another method involves the reaction of urea, nitric acid and sulfuric acid
2 (NH2)2CO + 2 HNO3+ H2SO4 → 2 N2O + 2 CO2 + (NH4)2SO4 + 2H2O.
 Direct oxidation of ammonia with a manganese dioxide-bismuth oxide catalyst has been
reported Ostwald process.
2 NH3 + 2 O2 → N2O + 3 H2O

5. • Hydroxyl ammonium chloride reacts with sodium nitrite to give nitrous oxide.
• If the nitrite is added to the hydroxylamine solution, the only remaining by-product is salt water.
• If the hydroxylamine solution is added to the nitrite solution (nitrite is in excess), however, then
toxic higher oxides of nitrogen also are formed
NH3OHCl + NaNO2 → N2O + NaCl + 2 H2O
Treating HNO3 with SnCl2 and HCl also has been demonstrated
2 HNO3 + 8 HCl + 4 SnCl2 → 5 H2O + 4 SnCl4 + N2O
• Hyponitrous acid decomposes to N2O and water with a half-life of 16 days at 25 °C at pH 1–3.
H2N2O2→ H2O + N2O

7.  The process involved in drying and purifying the gas may vary but that used by the british oxygen
company in the uk
 A strong solution of ammonium nitrate when heated produces nitrous oxide with ammonia ,
nitric acid, nitrogen and traces of nitric oxide and nitrogen dioxide.
 Cooling of the emerging gases results In reconstitution of the ammonia and nitric acid to
ammonium nitrate and this is turned to reactor
 The gases are now passed through water scrubber which remove any residual ammonia ad nitric
acid and the through caustic permanganate scrubbers which remove the higher oxides of nitrogen
to leave a residuum of 1vpm of nitric acid and nitrogen dioxide with the purified nitrous oxide and
some nitrogen
 Acid scrubbers now remove any final traces of ammonia and the gases are the compressed and
dried In a aluminum drier.

8. As the gases leave the drier continuous sampling takes place by passing a small stream of them through
a visual bubbler
This consist of a colour less solution in series, the first containing acid potassium permanganate which
converts any nitric oxide to nitrogen dioxide
The second consists of a colour less solution of a Saltzman reagent In which any nitrogen dioxide
present dissolves causing chemical reaction which produces a magenta colour
The compressed and dried gases are now expanded into a liquefier with resultant liquefaction of the
nitrous oxide and escape of the gaseous nitrogen
The pure nitrous oxide is now evaporated, compressed to a liquid, and passed through a second
aluminum drier to the cylinder filing line
At this stage visual and electronic checks are carried out on samples leaving the drier to ensure that the
nitrogen dioxide content does not exceed 1vpm

9.  About 9/10 of the contents of a full nitrous oxide cylinder are In liquid form
 Great care is take during manufacturing to prevent moisture being included In the cylinder contents,
since water vapor tends to freeze as it passes through a reducing valve and may lead to obstruction of
gas flow
When a nitrous oxide cylinder is turned on, the gas tension within is first reduced and the rapidly
increases again as some of the liquid vapourises.
Latent heat is required for the vaporization of liquid nitrous oxide and this is obtained from the casing
of the metal cylinder, which as a result, rapidly cools
 This In turns leads to freezing of the water vapour the air immediately surrounding the cylinder ,and to
the formation of layer of ice on the cylinder
 Nitrous oxide cylinders are marketed In various size and coloured blue.

10. IMPURITIES
 The main impurities is nitrogen dioxide, carbon monoxide
 This may be produced from burning particles of the sacks In which ammonium nitrate is
delivered
 The consequences of inhaling higher oxides of nitrogen , especially nitrogen dioxide, In
concentrations of over 50vpm are reflex inhibition of breathing with larnygospasm, and the rapid
onset of intense cyanosis
 The last is due to both the formation of methaemoglobin and to altered pulmonary gas
exchange
 Pulmonary odema may occur In the acute phase, but with concentrations lower than 50vpm it
may not appear for some hours

11.  If the patient doesnt die immediately chronic chemical pneumonitis may follow with resultant
pulmonary fibrosis , respiratory acidosis from associated ventilator failure and metabolic acidosis
from production of nitric and nitrous oxide formed from solution of the gases In the body fluids
 Hypotension may be marked and results from the effect of nitrate and nitrate ions on vascular smooth
muscles
 The detection of higher oxides of nitrogen has been reviewed by kain and associates
 In clinical practice the best method involves the use of strach iodide paper.
 The moistened paper is placed In a 20ml syringe ad 15ml of oxygen drawn up, followed by 5ml of the
sample gas
 Any nitric oxide will be oxidized by the oxygen to nitrogen dioxide, and the latter by oxidizing iodide
to iodine will turn the starch from a faint purple to a right blue, depending o the amount of iodine
present

12. The principles of treatment of poisoning by the higher oxides of nitrogen have been discussed
by Prys- Roberst
Oxygen either by spontaneously or assisted ventilation and methylene blue, 2mg/kg of body
weight IV, will be required initially to overcome the intense cyanosis resulting from
methheammoglobenemia
Further increments of methylene blue may be required , but excessive amounts can result In the
production of methaemoglobin and also haemolytic anemia.
The severe systemic hypotension from vasodilation can be improved by iv fluids and minimal
dose of vasopressor
The use of dimercaprol is suggested for severe cases since it has protective action against the
higher oxides of nitrogen

13. PRODUCTION AND STORAGE
 Nitrous oxide is produced commercially byheating ammonium nitrate to
240C.
 Water vapour and impurities, including higher oxides of nitrogen, ammonia and nitric acid
, are subsequently removed by passage through a series of washers and scrubbers.
 Nitrous oxide is stored in French-blue cylinders (pin-index3,5) pressurized to 4400kPa at
roomtemperature.
 Nitrous oxide is usually stored below itscritical temperature, and thus exists
simultaneously in liquid and vapour phases.

14. Click to add title
Physical Properties
N2O is a nonirritating, sweet-smelling, colorless gas
Only inorganic substance other than CO2 to have CNS depressant
properties Only inorganic gas used to produce anesthesia in humans
N2O liquid requires heat for vaporization into gaseous state
Relatively insoluble in the blood; Blood-gas solubility coefficient is
0.47 at 37 deg. C

15. 1. Molecular Weight - 44.01
2. Specific Gravity - 1.527
3. Boiling Point - - 89°C
4. Blood/Gas Solubility Coefficient - 0.47
5. Vapour Pressure At 20°C - 800psi
6. Maximum Safe Concentration - 80%
7. MAC - 105

16. Potency of Nitrous Oxide
 Least potent of anesthetic gases
 35 more times soluble than N2 in plasma 100 times more soluble than O2 in plasma
N2O + O2 can produce CNS depression
 N2O in subanesthetic doses can produce analgesia
 N2O +O2 at 20%/80% is equal-analgesic to 10 to 15 mg of morphine
 Optimal concentration is 35%

17. Pharmacology of Nitrous Oxide
 N2O is rapidly absorbed into the CV system, due to large concentration gradient of
N2O between alveolar sacs and blood
 N2O rapidly fills air-filled body cavities
 Due to rapid uptake, two phenomena are seen
Concentration effect - higher concentrations cause more rapid uptake of N2O
Second gas effect - a second anesthetic gas will also be taken up more rapidly th
an usual when added to N2O

18. Absorption
o CNS saturation occurs by displacement of N2 by N2O, usually in 3-5 minutes
o Tissues with greater blood flow (brain, heart, liver, kidney) receive greater amounts of
N2O
o Tissues with poor blood supply (fat, muscle, connective tissue) absorb small amounts
o Slow absorption occurs once primary saturation is completed
o Therefore no body reservoir present to slow recovery once N2O terminated

19. Effects of Nitrous Oxide on Organ
Systems
Central Nervous System
 Actual mechanism unknown
 Mild depression of CNS (cerebral cortex) in conjunction with
physiological levels of O2 (greater than 20%)
 Sensations depressed (sight, hearing, touch, pain)
 Cardiovascular System
 No changes in heart rate or cardiac output
 Blood pressure remains stable with only slight decrease
 Cutaneous vasodilation

20. Respiratory System
• N2O is non-irritating to pulmonary epithelium
• Changes (drop) in rate and depth more likely due to anxiolytic effects
• Slight elevation of resting respiratory minute volume at 50%/50%
Musculoskeletal System
• No direct relaxation of skeletal muscle
• Anxiolytic effects help relaxation

21. GI System
No clinically significant effects, unless there is a closed space (obstruction)
N/V rarely seen unless hypoxia present Can be used in hepatic dysfunction
Hematopoietic System
Long-term exposure (greater than 24 hours) can produce transient bone
marrow depression
Reproductive System
Uterine contractions not inhibited
Pregnancy is a relative contraindication (avoid in first trimester)