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Citric acid is an organic compound with the formula H O C(CO 2 H)(CH 2 CO 2 H) 2. [10] It is a colorless weak organic acid. [10] It occurs naturally in citrus fruits.In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.
When citric acid is added, it is always done after primary alcohol fermentation has been completed due to the tendency of yeast to convert citric into acetic acid. In the European Union, use of citric acid for acidification is prohibited, but limited use of citric acid is permitted for removing excess iron and copper from the wine if potassium ...
In the case of citric acid, the overlap is extensive and solutions of citric acid are buffered over the whole range of pH 2.5 to 7.5. Calculation of the pH with a polyprotic acid requires a speciation calculation to be performed. In the case of citric acid, this entails the solution of the two equations of mass balance:
The Henderson–Hasselbalch equation can be used to model these equilibria. It is important to maintain this pH of 7.4 to ensure enzymes are able to work optimally. [10] Life threatening Acidosis (a low blood pH resulting in nausea, headaches, and even coma, and convulsions) is due to a lack of functioning of enzymes at a low pH. [10]
Pure water has a pH of 7 at 25°C, meaning it is neutral. When an acid is dissolved in water, the pH will be less than 7, while a base, or alkali, will have a pH greater than 7. A strong acid, such as hydrochloric acid, at concentration 1 mol dm −3 has a pH of 0, while a strong alkali like sodium hydroxide, at the same concentration, has a pH ...
For determining the acid value of mineral oils and biodiesel, there are standard methods such as ASTM D 974 and DIN 51558, and especially for biodiesel the European Standard EN 14104 and ASTM D664 are both widely used worldwide. [2] Acid value of biodiesel should be lower than 0.50 mg KOH/g in both EN 14214 and ASTM D6751 standard fuels.
It also takes place in some species of fish (including goldfish and carp) where (along with lactic acid fermentation) it provides energy when oxygen is scarce. [ 1 ] Ethanol fermentation is the basis for alcoholic beverages , ethanol fuel and bread dough rising.
The pH can be calculated approximately by the Henderson–Hasselbalch equation: [1] = + where K a is the acid dissociation constant. 3. The pH at the equivalence point depends on how much the weak acid is consumed to be converted into its conjugate base. Note that when an acid neutralizes a base, the pH may or may not be neutral (pH = 7).