Ammonia solution

Ammonia solution is a liquid formed by dissolving ammonia gas in water. It is known by many technical names, including aqueous ammonia, ammonium hydroxide, and ammoniacal liquor. Scientists often use the symbol NH3(aq) to denote it. While the name ammonium hydroxide suggests a specific chemical salt, it is actually impossible to isolate pure NH4OH. In most cases, the ammonia and hydroxide ions only make up a small part of the total solution. Most commercial products are highly concentrated. A typical high-concentration product contains about 30% ammonia by weight. This concentration is often measured using the Baumé scale, specifically at 26 degrees Baumé.

The chemical behavior of this solution is defined by its basicity. When ammonia is added to water, a process called deprotonation occurs. In this process, a small fraction of the water molecules lose a proton to the ammonia. This reaction creates ammonium and hydroxide ions. The chemical equilibrium is written as NH3 + H2O ⇌ NH4+ + OH−. In a 1 M ammonia solution, only about 0.42% of the ammonia converts into these ions. This results in a high pH level of approximately 11.62. The base ionization constant, or Kb, for this reaction is 1.77.

The physical properties of the solution change depending on temperature and concentration. Ammonia gas becomes less soluble in water as the temperature of the liquid increases. This means that if you warm up a saturated solution, the ammonia gas will be released. At a temperature of 0°C, a saturated solution has a density of 0.88 g/ml. Such a solution contains 35.6% ammonia by mass, which equals 308 grams of ammonia per liter. This specific concentration has a molarity of about 18 mol/L. As temperatures rise, the molarity decreases while the density increases.

In the home, ammonia solution is most commonly used as a cleaning agent. Household versions usually range from 5% to 10% ammonia by weight. Because the ammonia is a gas dissolved in water, it evaporates quickly. As the water evaporates from a surface, the gas evaporates too. This leaves surfaces like glass, porcelain, and stainless steel looking streak-free. It is also very effective at removing grease from ovens. However, experts warn against using these cleaners on car touchscreens. The chemicals can damage anti-glare or anti-fingerprint coatings. Professional cleaners use much stronger solutions with concentrations higher than 10%.

History shows several unique industrial uses for ammonia solution. In the early twentieth century, the vapor absorption cycle was a popular way to refrigerate food. These systems used a water-ammonia mixture to create cooling. Famous examples of this technology include the Electrolux refrigerator and the Einstein refrigerator. Eventually, these were largely replaced by the vapor compression cycle. This newer method is much more efficient, as the absorption cycle had only about one-fifth of its performance. Today, aqueous ammonia is also used as a precursor to create alkyl amines. For instance, formaldehyde and aqueous ammonia can react to form hexamethylenetetramine.

Ammonia also plays a vital role in food production and water safety. In the European Union, it is listed as food additive E527. It can act as an acidity regulator to lower acid levels in food. In the United States, the FDA classifies food-grade ammonia as generally recognized as safe (GRAS). Historically, bakers used "baking ammonia" made from deer antlers to help dough rise. This substance, ammonium carbonate, is heat activated. It allows treats like ammonia cookies to stay crisp without the long waiting times required by yeast. In water treatment, ammonia is used to produce chloramine. This disinfectant is often preferred in drinking water because it stays active in stagnant pipes longer than chlorine.

Despite its many uses, ammonia solution requires careful handling due to safety risks. The liquid can irritate the eyes, skin, and the respiratory or digestive tracts. It is extremely important never to mix ammonia with bleach or other strong oxidants. Doing so creates a dangerous, toxic gas called chloramine. In the laboratory, scientists use it as a complexant and a base. It can turn copper(II) solutions a deep blue color. It is also used to clean precious metals like gold and silver. However, users must be careful with porous gemstones like pearls or opals, as the solution may cause damage.