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e. In chemistry, pH (/ piːˈeɪtʃ / pee-AYCH), also referred to as acidity or basicity, historically denotes " potential of hydrogen " (or "power of hydrogen"). [ 1 ] It is a logarithmic scale used to specify the acidity or basicity of aqueous solutions. Acidic solutions (solutions with higher concentrations of hydrogen (H+) ions) are ...
Pourbaix diagram of iron. [1] The Y axis corresponds to voltage potential. In electrochemistry, and more generally in solution chemistry, a Pourbaix diagram, also known as a potential/pH diagram, E H –pH diagram or a pE/pH diagram, is a plot of possible thermodynamically stable phases (i.e., at chemical equilibrium) of an aqueous electrochemical system.
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. [ 1 ][ 2 ] It is most frequently used by reference to a set of standards against which compliance, generally achieved through treatment of the water, can be assessed.
A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. [1] Hence, a pH indicator is a chemical detector for hydronium ions (H 3 O +) or hydrogen ions (H +) in the ...
For example, if honey (a w ≈ 0.6) is exposed to humid air (a w ≈ 0.7), the honey absorbs water from the air. If salami (a w ≈ 0.87) is exposed to dry air (a w ≈ 0.5), the salami dries out, which could preserve it or spoil it. Lower a w substances tend to support fewer microorganisms since these get desiccated by the water migration.
Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average. [1][2] The more acidic the acid rain ...
Beckman model 72 pH meter, 1960. 781 pH/Ion Meter pH meter by Metrohm. A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH. [2] The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode ...
The pD of heavy water is generally measured using pH electrodes giving a pH (apparent) value, or pHa, and at various temperatures a true acidic pD can be estimated from the directly pH meter measured pHa, such that pD+ = pHa (apparent reading from pH meter) + 0.41. The electrode correction for alkaline conditions is 0.456 for heavy water.