Properties of Ammonia. — Ammonia is a colorless, gaseous compound of nitrogen and hydrogen. Its chemical formula is NH3, indicating that one atom of nitrogen unites with three atoms of hydrogen to form ammonia. Its boiling point at atmospheric pressure is -28° F. It has a melting point of -107.86° F. Color and Odor. — Ammonia is a colorless, transparent liquid or gas. It has an extremely pungent, peculiar, and offensive odor which is easily recognizable and irrespirable. Inflammability. — It does not support combustion. However, under high pressure it may form an explosive mixture when intermingled with oil vapor. It is decomposed into its elements by extreme heat and under such conditions, an explosive mixture may result. It is combustible when mixed with a sufficient proportion of air, being capable of exploding with considerable violence. Corrosion of Metals. — It will attack copper and all of its alloys when water is present, but it has no chemical or corrosive action on iron and steel. Ammonium hydroxide has a slight reaction on iron when in a very dilute concentration. With the higher concentrations used in ammonia absorption plants, no reaction occurs on iron.
<Callout type="warning" title="Safety Hazard">Ammonia is highly dangerous due to its explosive potential under high pressure and corrosive effects on copper alloys.</Callout> Locating Leaks. — Ammonia leaks may be readily located by the 'smoke' test which consists of placing a burning sulfur stick in the vicinity of the leak. A chemical reaction occurs and a dense white smoke apparently issues from the opening.
Stability Toward Heat. — It is a rather stable gas especially at temperatures under 300° F. However, the chemical bond is not as strong as with carbon dioxide and sulphur dioxide. A household compressor should always have a discharge gas temperature lower than 300° F. Solubility in Water. — It is very soluble in water, the union of the two producing considerable heat and forming ammonium hydroxide until a certain concentration has been reached. The vapor may then be driven off by heating the ammonium hydroxide, and it is on this principle that the absorption system operates.
Properties of Butane. — Butane is one of the isomeric, flammable gaseous hydrocarbons of the methane series. Its chemical formula is C4H10, indicating that four atoms of carbon unite with ten atoms of hydrogen to form butane. It has a boiling point of 31° F. at normal atmospheric pressure and a melting point of -211° F.
<Callout type="important" title="Critical Information">Butane is stable under refrigeration conditions, but leaks are difficult to detect without specialized equipment.</Callout> Color and Odor. — Butane is a colorless liquid or gas with a slight ethereal odor and is slightly asphyxiating. The vapor is non-poisonous. Inflammability. — It is flammable, the gas burning with a yellow flame. Corrosion of Metals. — It has no corrosive effect on copper, copper alloys or iron, even in the presence of moisture. Locating Leaks. — It is difficult to locate leaks as no easy sight test can be made.
Properties of Carbon Dioxide (Carbonic Acid Gas). — Carbon dioxide is a heavy, colorless gas; it is sometimes called carbonic acid gas. This is on account of the fact that the acid, carbonic acid, H2CO3 breaks down readily into water and carbon dioxide, CO2; the latter is commonly called carbon dioxide or carbonic acid gas.
<Callout type="beginner" title="Clarification for Newcomers">Carbon dioxide does not support combustion but can be dangerous in high concentrations as it displaces oxygen.</Callout> It has a chemical symbol, CO2, which indicates that one atom of carbon unites with two atoms of oxygen to form carbon dioxide. At normal atmospheric pressure, it has a boiling temperature of -108.4° F. Color and Odor. — Carbon dioxide is a colorless liquid or gas. It exists as a gas in very small quantities in the atmosphere and is non-odorous. Inflammability. — It is not flammable and does not support combustion. Corrosion of Metals. — It has no corrosive effect on copper, copper alloys or iron. Locating Leaks. — It is difficult to locate leaks as no easy sight test can be made.
Stability Toward Heat. — It is a stable gas which does not break up at temperatures encountered in normal operation. The critical temperature is 87.80° F. Solubility in Water. — It is slightly soluble in water, the percentage increasing at lower temperatures. Displacement Required. — It requires about one-fourth the displacement of an ammonia machine to do the same amount of refrigeration.
Key Takeaways
- Ammonia is highly flammable and corrosive, requiring careful handling and leak detection methods.
- Butane is stable under refrigeration conditions but difficult to detect for leaks without specialized equipment.
- Carbon dioxide does not support combustion but can be dangerous in high concentrations due to oxygen displacement.
Practical Tips
- Use a smoke test with sulfur sticks to locate ammonia leaks quickly and effectively.
- Ensure proper ventilation when handling flammable refrigerants like butane or ethyl chloride.
- Regularly check for non-condensable gases in household ammonia absorption machines to maintain efficiency.
Warnings & Risks
- Ammonia can form an explosive mixture under high pressure, especially with oil vapor present.
- Butane leaks are hard to detect visually and require specialized equipment or methods like flame tests.
- Carbon dioxide poses a suffocation risk in confined spaces due to its ability to displace oxygen.
Modern Application
While the refrigerants discussed here have largely been replaced by more environmentally friendly alternatives, understanding their properties is crucial for maintaining older systems. Knowledge of these materials can also be valuable in emergency situations where modern refrigeration solutions are unavailable.
Frequently Asked Questions
Q: What is the boiling point of ammonia at atmospheric pressure?
The boiling point of ammonia at atmospheric pressure is -28° F.
Q: How can one detect an ammonia leak in a refrigeration system?
An ammonia leak can be detected by using a 'smoke' test with a burning sulfur stick, which will produce dense white smoke when near the leak.
Q: What is the critical temperature of carbon dioxide?
The critical temperature of carbon dioxide is 87.80° F.