Posted on 12th Dec 2021 @ 12:22 PM

Formula: NH3
Boiling Point: -33 C
Melting point: -78 C
Vapour density: 0.597 (Dry air = 1)
Liquid density is 683 kg/tonne water
Decomposes at 500 C
Burns in oxygen
Lighter than air (average mass/cubic metre. = 0.77 kg, compared to air which averages 1.28 Kg
(at 0 degrees C). Relative density is about 60% the weight of air (depending on temperature). At NTP, Ammonia mass/cubic metre is 0.72 Kg.(see footnote)

{Air is given a vapour density of one. For this use, air has a molecular weight of 28.97 atomic mass units, and all other gas and vapour molecular weights are divided by this number to derive their vapour density.}

1 Kg NH3 (anhydrous) occupies 1.464 litres liquid volume. It follows that, per litre liquid, mixed in air, a concentration of 25 parts/million occupies a volume of 26,000 cubic Metres.

Colourless gas in the anhydrous state. Very Hygroscopic, adsorbing water from the atmosphere to form Ammonium Hydroxide (NH₄.OH), Ammonium Hydroxide is a caustic liquid of pH>12.5 in concentration. A weak alkali, it is reactive, causing rapid corrosion of Copper, Brass alloys and Zinc and it will cause corrosion of mild steel as rapidly as will water. These materials should thus be avoided in designing plant. A Prussian blue deposit indicates ferrous corrosion: Galvanic zinc corrosion on steel yields white Zinc Oxide and Hydroxide. Cuprous corrosion yields green/ blue insoluble salts, dependent on the purity of copper.

Ammonia is flammable in air at volumetric concentrations above 15% when it oxidises to form Water and Nitric oxide.
(In air) Lower Explosive Limit is 16%. Upper Explosive Limit is 25%
Typical Olfactory threshold is 3<>5 PPM
It is toxic and its current respiratory ingestion limits (Work Place Limits) are:
OEL = 25 PPM (17 mg/M3)
MEL = 35 PPM (24 mg/M3).
At concentrations over 1700 PPM, it can cause death after about 30 minutes. At 1% volume death will take less than 5 minutes.

Uses: Refrigeration plant, Production of explosives, fertilisers and Nitric acid.

Storage: Temperature < 60 C in compressed gas cylinders, properly marked and kept in isolated compounds away from buildings.

Critical Health Indications:
Skin & Mucosa burns/ irritation
Metabolic toxification (see link: 1))
Bronchospasm.
There are no chronic health indications usually associated with short term exposure but long term exposure from repeated inhalation exposure to ammonia may cause long-term health effects, including persistent airway obstruction, cough, exertional dyspnoea, bronchiolitis obliterans and bronchiectasis, which for some cases may persist for many years.

First Aid: Mucosa, skin, eyes: Irrigate copiously with cold water or saline. Afterwards, apply burns dressing or Zinc Oxide cream** to reddened but unbroken, unblistered skin. If burn has destroyed or broken/ blistered skin, irrigate with cold water and apply a burn dressing. Then seek medical assistance.

Lungs: Administer oxygen immediately following exposure. Especially if Bronchospasm is indicated. If oxygen is unavailable, place patient in fresh air & encourage calm breathing. Oxygen should normally be taken in a reclining, relaxed position unless cardiac insufficiency is indicated. Seek medical assistance.

Protective equipment
R.P.E.*, Gauntlets, Chemical protective clothing suitable for low temperatures.

• · Positive pressure breathing apparatus should be used where effective protection factors greater than 40 are required.        
• ·        ** Sudocrem is the usual commercial preparation

 NTP - Normal Temperature and Pressure - is defined as 20^oC (293.15 K, 68^oF) and 1 atm ( 101.325 kN/m², 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)

 STP - Standard Temperature and Pressure - is defined as  0^oC (273.15 K, 32^oF) and 1 atm (101.325 kN/m², 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)

One Mole of gas occupies 22.4 litres @STP - for example: air has a mass of 1000/22.4 x 0.02896 Kg = 1.292 Kg.

Ammonia has a Mole weight of 24.95 per litre, so, by similar calculation, at 25 parts per million volumetric concentration, it will weigh about 17 milligrammes per cubic Metre. 

1) Link Page to Public Health England: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/455704/Ammonia_TO_PHE_240815.pdf