Water for the body is the second most necessary component after air. All cells, organs and tissues of the body contain this important component. Therefore, all substances that change its composition affect the whole organism. One of the most important indicators of water quality is the hydrogen index — pH (in Russian it is pronounced «pe-ash»).
What is water pH, how did it appear (who discovered it) and why is it needed?
The hydrogen index is a measure of the activity of hydrogen ions, through which the acidity of a liquid is quantified. It is equal to the modulus (with opposite sign) of the decimal logarithm of the activity of hydrogen ions, the unit of measurement is mole per liter.
The concept of «hydrogen index of solution» and the pH scale were proposed in 1909 by the Danish chemist S.P.L. Sørensen, the head of the chemical-physiological laboratory at Karlsberg in Copenhagen. The scientist published his research simultaneously in two articles printed in Germany and France.
The pH level of water reflects its acid-alkaline balance, which has a great influence on the biochemical reactions taking place in the aquatic environment. Accordingly, the quality of many processes in the human body depends on the water one consumes. For example, concentration of hydrogen ions in the solution often influences biological activity of nucleic acids and proteins, their physicochemical properties.
Reference: For most animals and plants living in water, a specific level of acidity is suitable for life. Even a slight change in it leads to their death. When the pH is below 4 or above 10, almost all fish die, and many animals cannot survive in an environment where the pH is less than 3 or more than 11.
How is the pH of water measured and what are some examples of the indicator?
Several techniques are widely used to measure the acid-alkaline equilibrium of solutions. A rough estimate can be made with indicators, measured accurately with a pH meter, or determined analytically by acid-base titration.
For a rough estimation of the hydrogen ion concentration, dyes of organic origin are most commonly used, the color of which depends on the acidity of the medium. The most common indicators are: litmus, methylorange, phenolphthalein, etc. They are capable of being in two different color forms: basic or acidic. On contact with water, the color of each of the dyes changes in its own range of acidity, which is usually 1 — 2 units. There are indicator strips both on the basis of one of the coloring substances and «universal» — with a mixture of several indicators. The advantage of this method is cheapness, speed and clarity of the study. In order to find out the pH value of the liquid, you only need to immerse the indicator strip in it and compare the resulting color with the scale on the package. But this method has a fairly large margin of error.
Using a special device, a pH meter, you can measure the «hydrogen index» with greater accuracy (up to 0.01 pH units) and in a wider range. A water sample of 20 — 30 ml is taken into a beaker or flask. Then the sensor of the device, previously washed with distilled water, is immersed into the solution. The pH value of the liquid is evaluated on the instrument scale. The accuracy of measurements depends on regular calibration of the device with standard solutions with a given pH value. This method is accurate, fast, simple enough, but more costly materially and requires some skills in working with laboratory equipment and chemical solutions.
Accurate results are obtained by acid-base titration. But it can be implemented only under laboratory conditions. A solution of a given concentration (titrant) is added one drop at a time to the tested liquid. A chemical reaction begins to take place. Using an indicator, the moment when the titrant is enough to complete the reaction is highlighted. According to the amount of titrant added and its concentration the acidity of the tested solution is determined.
Depending on the pH value, water is divided into the following types:
- Water type pH value
- Strongly acidic waters less than 3
- Acidic waters 3 to 5
- Mildly acidic waters 5 to 6.5
- Neutral waters 6.5 to 7.5
- Low-alkaline waters 7.5 to 8.5
- Alkaline waters 8.5 to 9.5
- Highly alkaline waters above 9.5
What is the normal pH of drinking water and why?
Experts say that the acid-alkaline balance of drinking water and human blood (in a healthy body — 7.5) should be about the same. On this basis, the best water is considered to have an acidity between 7 and 7.5. Consumption of such a liquid has a positive effect on metabolism and oxygen metabolism, increases the duration and quality of life.
A disorder of acid-alkaline balance in the internal environment of the human body has a detrimental effect on his health. For example, a shift of pH level to the lower side can lead to a number of serious pathologies. Such a change indicates that the body develops an acidic environment, in which gastrointestinal diseases, metabolic disorders, etc. are possible. An excessive increase in the index leads to the formation of an alkaline environment, which can also cause a number of ailments — digestive problems, reduced immunity and others.
Interesting: the acid-base balance of the blood can be assessed by the color of the conjunctiva in the corners of the eyes. If it is normal, the conjunctiva is bright pink. A pale pink color indicates that the pH is shifted towards acidity. Dark pink conjunctiva «speaks» of alkalizing blood. Changes in the color of the mucous membrane of the eyes can be assessed 80 seconds after ingestion of certain substances.
According to SanPiN drinking water should have pH in the range of 6 — 9 units.
Water with increased acidity is very aggressive to the inner walls of metal water pipes, increasing the rate of corrosion. As a result, metals and rust dissolve in water, hence lead, copper and iron in it becomes more. Regular consumption of such water leads to accumulation of toxic metals in the body, resulting in health risks.
IMPORTANT: When the pH value is higher than 11, water can harm human health — cause irritation of the skin and mucous membranes.
Fluctuations in the pH level of drinking water can contribute to the formation of a biofilm on the pipe walls, which is a community of microorganisms (bacteria). The interaction of the biofilm with the pipe material and corrosion products results in microenvironments that change microbiological and chemical parameters of water. Laboratory analysis of tap water with reduced acidity can show the presence of pathogenic bacterial cysts.
REFERENCE: The hydrogen index of fresh river water is usually between 6.5 and 8.5; atmospheric precipitation, 4.6 to 6.1; swamp water, 5.5 to 6.0; sea water, 7.9 to 8.3. Thus, under natural conditions, the acid-alkaline balance of water fluctuates within the permissible range and has no significant influence on its consumer properties.
Is there any way to influence the pH of the water we drink?
At home, the acidity of drinking water can be adjusted using water filters, which include special cartridges.
Mineralizer cartridges are used to lower the acidity. They contain slowly soluble minerals, passing through which the water is enriched with useful alkaline elements.
Reverse osmosis membranes, which reduce the mineral content of the water, shift the pH level toward higher acidity. Ion exchange materials of natural (e.g., dolomite) or synthetic (hydrogen ion exchange resins) origin also acidify the water.
Acid-base balance is one of the main indicators of drinking water quality, its optimal level is 7 — 7,5. It is important for each person to monitor the pH value of the water he/she consumes. Existing diagnostic methods allow to estimate its acidity even at home and special filters help to correct it to the normal level.