# pH

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## pH,

range of numbers expressing the relative acidity or alkalinity of a solution. In general, pH values range from 0 to 14. The pH of a neutral solution, i.e., one which is neither acidic nor alkaline, is 7. Acidic solutions have pH values below 7; alkaline, or basic, solutions have pH values above 7. A pH value provides a measure of the hydrogen ion concentration of a solution. In pure water the concentration of hydrogen ions is equal to 0.0000001, or 10−7, moles per liter. (A mole is the amount of a substance, expressed in grams, that is equal to the molecular weight, or formula weight, of the substance.) When an acid is added to pure water, the hydrogen ion concentration increases above this level. When an alkaline substance, or base, is added to pure water, the hydrogen ion concentration decreases below this level. Once the concentration is determined, the pH value is found by taking the exponent used in expressing this concentration and reversing its sign. This is expressed as pH=−log10 [H+]. For example, if the hydrogen ion concentration of a solution is 10−4, or 0.0001, moles per liter, the pH is 4. See indicators, acid-baseindicators, acid-base,
organic compounds that, in aqueous solution, exhibit color changes indicative of the acidity or basicity of the solution. Common indicators include p-nitrophenol, which is colorless from pH 1 to 5 and yellow from p
.

## pH

[pē′āch]
(chemistry)
A term used to describe the hydrogen-ion activity of a system; it is equal to -log aH+; here aH+is the activity of the hydrogen ion; in dilute solution, activity is essentially equal to concentration and pH is defined as -log10[H+], where H+is hydrogen-ion concentration in moles per liter; a solution of pH 0 to 7 is acid, pH of 7 is neutral, pH over 7 to 14 is alkaline.

## pH(S)

(analytical chemistry)

## pH

A measure of the acidity or alkalinity of a solution; numerically equal to 7.0 for a neutral solution; the pH value increases with increasing alkalinity and decreases with increasing acidity. Also See pH value.

## PH

1. On drawings, abbr. for phase.

## phot

A unit of illumination equal to 1 lumen per square centimeter. Abbr. ph.

## pH

potential of hydrogen; a measure of the acidity or alkalinity of a solution equal to the common logarithm of the reciprocal of the concentration of hydrogen ions in moles per cubic decimetre of solution. Pure water has a pH of 7, acid solutions have a pH less than 7, and alkaline solutions a pH greater than 7

## PH

(tool)
The tool for looking up people in Eudora on the Macintosh. Equivalent to Unix's finger service.

(2)

## ph

(networking)
The country code for the Philippines.
References in periodicals archive ?
The acidic quality of the water has also improved, after previous tests showed it measured 2 on the pH scale.
Neutral is 7 on the pH scale. Pure water is measured on the scale as having a pH of 7.0.
Because pure distilled water has the same number of hydrogen ions as hydroxyl ions, it rates a neutral 7 on a 0-14 pH scale. Despite the large amounts of water in the human body, normal pH is always slightly alkaline.
Acidity is expressed quantitatively using the pH scale. Recall that pH is calculated as:
In fact, Drano is at the opposite end of the pH scale in that the active ingredient is sodium hydroxide (NaOH), more commonly known as lye.
In this sense, beverages are a good application for natural colors because beverages tend to be on the lower pH scale. Yogurt and ice cream tend to be higher, so therefore the stability of the colors isn't going to be as long, but again, natural colors work in these applications because these products don't have a long shelf life to start."
For comparison, on the logarithmic pH scale, pure water is neutral at pH 7.0, lemon juice is pH 2.4, and a 30% sulfuric acid solution, such as battery acid, is pH -2.0.
Given that the concentrations of these ions are extremely small, scientists use the pH scale, which ranges in value from 0 to 14.
Reaction is measured by the pH scale, as shown in figure 11-1, which gives sample pH values for common substances.
THE pH scale is used to measure acidity or alkalinity of soil.
The sensors are designed for process industry applications that span the entire pH scale; have strong chemical concentrations and h igh solids; run at high temperatures and cycle from high to low temperature.

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