Critical PH at which enamel start to demineralization is.. 5

Critical PH at which enamel start to demineralization is:

1. 5 ***
2. 6.9
3. 4 
4. 2

What is the pH value?

The pH value is used as a standard measure for measuring the properties of water. In English it reads "Bh", and in German "Beh Ha". In scientific terms, the pH value expresses the concentration of hydrogen ions (H+) in a liquid. If the concentration of hydrogen ions (H+) in a liquid is high, it is acidic. If the concentration is low, it is alkaline. This means that when measuring the concentration of hydrogen ions, the amount of acidity, neutrality, and alkalinity can be known, as well as the degree of each. The pH value has a scale from 0 to 14, where the value of 7 is the neutral level and any value less than 7 increases the acidity level with the decrease in the value, and any value above 7 is alkaline and the alkalinity increases with the increase in the value. Bitter-tasting liquids such as vinegar, juice, and washing soda (alkaline lye or ash dissolved in water) are alkaline. Neutral (pH 7) means that the concentration of hydrogen ions is 10 to the power minus 7 (0.0000001) mol per liter. For example, in food production, pH-modifying food additives (citric acid, trisodium citrate, etc.) are widely used and play an important role in maintaining the quality of foods. Microorganisms have an ideal pH value for reproduction, and the pH limit for acidity and alkalinity for reproduction is different for each type of microorganism. The ideal pH level for most microorganisms is 7 to 8 (neutral or slightly alkaline) and if the pH level is outside this range the proliferation and multiplication of microorganisms will be suppressed.

For soil, the appropriate pH level for growing crops is usually 6.5 (slightly acidic), but there are some crops that prefer a neutral, more alkaline environment and others that prefer acid. In the manufacturing sector, the pH value is the standard measure for preventing oil spoilage, and it is essential to measure the pH value to prevent rusting of work materials. The pH level of liquid refrigerant is usually above 9 when the oil is fresh (new). Once spoilage begins, the pH level will drop, but the ideal pH value for the oil should remain above 8.5. When the pH value drops below 8, bacteria spread, multiply and cause damage.

The use of the pH value is becoming important in a wide variety of fields - from industry and food industries to soils and rivers.