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Because aqueous ammonia is a gas dissolved in water, as the water evaporates from a surface, the gas evaporates also, leaving the surface streak-free. Its most common uses are to clean glass [10], porcelain, and stainless steel. It is good at removing grease and is found in products for cleaning ovens and for soaking items to loosen baked-on grime.
Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic, and may be described as aqueous ammonia or ammonium hydroxide. [30] The maximum concentration of ammonia in water (a saturated solution) has a specific gravity of 0.880 and is often known as '.880 ammonia'. [31]
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
A pipe fitted with cloth filters on either side serves as a tunnel for air to diffuse through. The cloth is coated in phosphoric acid which attracts ammonia gas (a base). Air flows through the tube and ammonia sticks to the filters which can then be tested for NH 3 concentrations using Nessler's reagent and a spectrophotometer. [30]
The table above gives properties of the vapor–liquid equilibrium of anhydrous ammonia at various temperatures. The second column is vapor pressure in kPa. The third column is the density of the liquid phase. The fourth column is the density of the vapor. The fifth column is the heat of vaporization needed to convert one gram of liquid to vapor.
For example, the limiting acid in liquid ammonia is the ammonium ion, NH 4 + which has a pK a value in water of 9.25. The limiting base is the amide ion, NH 2-. NH 2 − is a stronger base than the hydroxide ion and so cannot exist in aqueous solution. The pK a value of ammonia is estimated to be approximately 34 (c.f. water, 14 [3] [4]).
The solubility of gas obeys Henry's law, that is, the amount of a dissolved gas in a liquid is proportional to its partial pressure. Therefore, placing a solution under reduced pressure makes the dissolved gas less soluble. Sonication and stirring under reduced pressure can usually enhance the efficiency.
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca, [3] Sr, Ba, Eu, and Yb (also Mg using an electrolytic process [4]), giving characteristic blue solutions. For alkali metals in liquid ammonia, the solution is blue when dilute and copper-colored when more concentrated (> 3 molar). [5]