Surely many have heard more than once about such a concept as pH (neutral, acidic or alkaline). This is an indicator of hydrogen, and can be found both on a tube of cream and at an appointment with a dermatologist. Knowing your skin's pH is very important. What kind of indicator is this? Let's try to figure it out.
A little about the structure of the skin
As is known, the stratum corneum, located in the epidermis of the skin, performs a protective function. It contains a water-lipid matrix containing fatty compounds and the Marcionini acid mantle. Many people believe that its pH is neutral - about 7, but this is a misconception. Covers with this will be dry and tight. The skin contains milk and lemon in its composition, which means that its balance should not go beyond sour. If any disturbances or changes occur in the dermis, the pH of the epidermis begins to change dramatically. This can be either a consequence of a serious illness or the result of improper skin care.
pH scale
First of all, you need to remember that the concept of “pH neutral” applies specifically to the environment in question. Regarding the skin, its value is 5.2-5.7, tears - 7.4, and in chemical solutions the neutral pH is 7 units (for example, water).
From chemistry lessons we know that the acid-base balance scale ranges from 0 to 14. Neutral pH is about half, anything lower is acidic, anything higher is alkaline. As for concepts in cosmetology, “pH neutral” means that this acid-base indicator is the most optimal for any skin.
In addition, oily skin is also determined by this indicator. Dry skin has a pH value from 5.7 to 7, normal skin - from 5.2 to 5.7, oily skin - from 4 to 5.2.
Skin problems: a vicious circle
We have already figured out what pH is, and now let's talk about the problems associated with this indicator. Oily skin is a problem for many people. Especially in adolescence. Almost every child inevitably develops pimples and acne. Of course, this is a consequence of a temporary hormonal imbalance. However, it is at this time that proper facial skin care is very important.
What do parents advise in this case? Wash your face more often? The teenager does this, but the acne only gets bigger. What is the reason? Soap is an alkaline product, and its pH varies from 6 to 11 units. Its frequent use leads to the fact that it washes away the top layer of the face with an acidic environment. The protective function of the stratum corneum works in such a way that the less beneficial acidic bacteria present in the normal flora of the face on the skin, the more subcutaneous fat it produces. This is a vicious circle: the more we wash ourselves, the more oily our skin becomes. A natural question arises: “What to do?”
How to keep pH normal?
In order to maintain its natural acid-base balance when washing your face, you need to pay special attention to the cosmetics that are used in this process. First of all, you need to find out which neutral pH soap can be used for frequent washing. If this is truly a necessary measure, then the hydrogen base must be acidic (up to 5.5 units). These include special foams, gels, and scrubs for oily skin (pH = 4).
If there are no problems as such, then for care you can use products with a slightly acidic reaction, 5.5 units, for dry skin - closer to neutral - 6.5. In any case, it is necessary to remember that in order to choose the right skin care product, it is necessary to approximately equalize the acid-base balance. The same goes for other skin products. A gel with a neutral pH is usually suitable for dry skin, while for problem skin you should choose products with a slightly acidic environment.
Shampoo and pH level
Like any substance, shampoo also has its own pH, and it is different for each brand. Here, according to the laws of chemistry, exactly the same rule applies: low values up to 7 units are acidic, higher values are alkaline. Shampoos with a neutral pH level - exactly 7 units. Regarding the scalp, almost everything remains unchanged. Normally, it has a more slightly acidic environment - 4.5-5.5. This means that the choice of shampoo should depend entirely on how oily your scalp is.
For dry types, it is recommended to use more alkaline shampoos, and for oily types, slightly acidic ones. If the scalp is not picky, such as a child’s, then you need to choose shampoos with a neutral pH (7 units). Unfortunately, only a small number of manufacturers indicate what acid-base indicator is present in their cosmetic product. They are limited only to inscriptions (for dry, oily, normal skin). This is not entirely correct, since, according to research, it turns out that, as a rule, shampoos for normal skin are alkaline, but should be slightly acidic.
Is it possible to determine the pH level of skin and products?
Many people would like to know the water-acid balance in a particular substance. Doing the test at home is not difficult. This requires a solution and an acid-base indicator, usually litmus strips. They are dipped into the solution and placed on white paper. Almost instantly the color appears on the indicator. According to the proposed color scale, it is possible to determine whether it is alkaline. For example, if litmus is dipped into an alkali, it will give a blue color, in an acidic environment it will give a red color.
Another way to find out what the pH is is with a pH meter. This is a very popular device with high detection accuracy. It is used in industries where environmental control is necessary (fuel production, chemical and paint industries, etc.). Such a device can also be found at an appointment with a dermatologist. In this article, we studied what pH is and found out how to correctly select skin care cosmetics according to their acid-base balance.
Remember:
A neutralization reaction is a reaction between an acid and a base that produces salt and water;
By pure water, chemists understand chemically pure water that does not contain any impurities or dissolved salts, i.e. distilled water.
Acidity of the environment
For various chemical, industrial and biological processes, a very important characteristic is the acidity of solutions, which characterizes the content of acids or alkalis in solutions. Since acids and alkalis are electrolytes, the content of H+ or OH - ions is used to characterize the acidity of the medium.
In pure water and in any solution, along with particles of dissolved substances, H+ and OH - ions are also present. This occurs due to the dissociation of the water itself. And although we consider water to be a non-electrolyte, it can nevertheless dissociate: H 2 O ^ H+ + OH - . But this process occurs to a very small extent: in 1 liter of water only 1 ion breaks down into ions. 10 -7 mol molecules.
In acid solutions, as a result of their dissociation, additional H+ ions appear. In such solutions there are significantly more H+ ions than OH - ions formed during slight dissociation of water, therefore these solutions are called acidic (Fig. 11.1, left). It is commonly said that such solutions have an acidic environment. The more H+ ions contained in the solution, the more acidic the medium.
In alkali solutions, as a result of dissociation, on the contrary, OH - ions predominate, and H + cations are almost absent due to the insignificant dissociation of water. The environment of such solutions is alkaline (Fig. 11.1, right). The higher the concentration of OH - ions, the more alkaline the solution environment is.
In a solution of table salt, the number of H+ and OH ions is the same and equal to 1. 10 -7 mol in 1 liter of solution. Such a medium is called neutral (Fig. 11.1, center). In fact, this means that the solution contains neither acid nor alkali. A neutral environment is characteristic of solutions of some salts (formed by alkali and strong acid) and many organic substances. Pure water also has a neutral environment.
pH value
If we compare the taste of kefir and lemon juice, we can safely say that lemon juice is much more acidic, i.e. the acidity of these solutions is different. You already know that pure water also contains H+ ions, but the sour taste of the water is not felt. This is due to the too low concentration of H+ ions. Often it is not enough to say that a medium is acidic or alkaline, but it is necessary to characterize it quantitatively.
The acidity of the environment is quantitatively characterized by the hydrogen indicator pH (pronounced “p-ash”), associated with the concentration
Hydrogen ions. The pH value corresponds to a certain content of Hydrogen cations in 1 liter of solution. Pure water and neutral solutions contain 1 liter in 1 liter. 10 7 mol of H+ ions, and the pH value is 7. In acid solutions, the concentration of H+ cations is greater than in pure water, and in alkaline solutions it is less. In accordance with this, the value of the pH value changes: in an acidic environment it ranges from 0 to 7, and in an alkaline environment it ranges from 7 to 14. The Danish chemist Peder Sørensen first proposed using the pH value.
You may have noticed that the pH value is related to the concentration of H+ ions. Determining pH is directly related to calculating the logarithm of a number, which you will study in 11th grade math classes. But the relationship between the content of ions in the solution and the pH value can be traced according to the following scheme:
The pH value of aqueous solutions of most substances and natural solutions is in the range from 1 to 13 (Fig. 11.2).
Rice. 11.2. pH value of various natural and artificial solutions
Søren Peder Laurits Sørensen
Danish physical chemist and biochemist, President of the Royal Danish Society. Graduated from the University of Copenhagen. At the age of 31 he became a professor at the Danish Polytechnic Institute. He headed the prestigious physicochemical laboratory at the Carlsberg brewery in Copenhagen, where he made his main scientific discoveries. His main scientific activity was devoted to the theory of solutions: he introduced the concept of pH value and studied the dependence of enzyme activity on the acidity of solutions. For his scientific achievements, Sørensen was included in the list of “100 outstanding chemists of the 20th century,” but in the history of science he remained primarily as the scientist who introduced the concepts of “pH” and “pH-metry.”
Determination of medium acidity
To determine the acidity of a solution in laboratories, a universal indicator is most often used (Fig. 11.3). By its color, you can determine not only the presence of acid or alkali, but also the pH value of the solution with an accuracy of 0.5. To more accurately measure pH, there are special devices - pH meters (Fig. 11.4). They allow you to determine the pH of a solution with an accuracy of 0.001-0.01.
Using indicators or pH meters, you can monitor how chemical reactions are progressing. For example, if chloride acid is added to a solution of sodium hydroxide, a neutralization reaction will occur:
Rice. 11.3. A universal indicator determines the approximate pH value
Rice. 11.4. To measure the pH of solutions, special devices are used - pH meters: a - laboratory (stationary); b - portable
In this case, solutions of reagents and reaction products are colorless. If a pH meter electrode is placed in the initial alkali solution, then the complete neutralization of the alkali by the acid can be judged by the pH value of the resulting solution.
Application of pH indicator
Determining the acidity of solutions is of great practical importance in many areas of science, industry and other areas of human life.
Ecologists regularly measure the pH of rainwater, rivers and lakes. A sharp increase in the acidity of natural waters may be a consequence of atmospheric pollution or the entry of industrial waste into water bodies (Fig. 11.5). Such changes entail the death of plants, fish and other inhabitants of water bodies.
The hydrogen index is very important for studying and observing processes occurring in living organisms, since numerous chemical reactions take place in cells. In clinical diagnostics, the pH of blood plasma, urine, gastric juice, etc. is determined (Fig. 11.6). Normal blood pH is between 7.35 and 7.45. Even a small change in the pH of human blood causes serious illness, and at pH = 7.1 and below, irreversible changes begin that can lead to death.
For most plants, soil acidity is important, so agronomists conduct soil analyzes in advance, determining their pH (Fig. 11.7). If the acidity is too high for a particular crop, the soil is limed by adding chalk or lime.
In the food industry, acid-base indicators are used to control the quality of food products (Fig. 11.8). For example, the normal pH for milk is 6.8. Deviation from this value indicates either the presence of foreign impurities or its souring.
Rice. 11.5. The influence of the pH level of water in reservoirs on the vital activity of plants in them
The pH value for cosmetics that we use in everyday life is important. The average pH for human skin is 5.5. If the skin comes into contact with products whose acidity differs significantly from this value, this will lead to premature skin aging, damage or inflammation. It was noticed that laundresses who used ordinary laundry soap (pH = 8-10) or washing soda (Na 2 CO 3, pH = 12-13) for a long time for washing, the skin of their hands became very dry and covered with cracks. Therefore, it is very important to use various cosmetics (gels, creams, shampoos, etc.) with a pH close to the natural pH of the skin.
LABORATORY EXPERIMENTS No. 1-3
Equipment: rack with test tubes, pipette.
Reagents: water, chloride acid, NaCl, NaOH solutions, table vinegar, universal indicator (solution or indicator paper), food and cosmetic products (for example, lemon, shampoo, toothpaste, washing powder, carbonated drinks, juices, etc. .).
Safety regulations:
For experiments, use small amounts of reagents;
Be careful not to get reagents on your skin or eyes; If a caustic substance gets in, wash it off with plenty of water.
Determination of Hydrogen ions and hydroxide ions in solutions. Establishing the approximate pH value of water, alkaline and acidic solutions
1. Pour 1-2 ml into five test tubes: into test tube No. 1 - water, No. 2 - chloride acid, No. 3 - sodium chloride solution, No. 4 - sodium hydroxide solution and No. 5 - table vinegar.
2. Add 2-3 drops of a universal indicator solution to each test tube or lower the indicator paper. Determine the pH of solutions by comparing the color of the indicator on a standard scale. Draw conclusions about the presence of Hydrogen cations or hydroxide ions in each test tube. Write dissociation equations for these compounds.
Study of pH of food and cosmetic products
Test samples of food and cosmetic products with a universal indicator. To study dry substances, for example, washing powder, they must be dissolved in a small amount of water (1 spatula of dry substance per 0.5-1 ml of water). Determine the pH of solutions. Draw conclusions about the acidity of the environment in each of the studied products.
Key idea
Control questions
130. The presence of what ions in a solution determines its acidity?
131. What ions are found in excess in acid solutions? in alkaline?
132. What indicator quantitatively describes the acidity of solutions?
133. What is the pH value and the content of H+ ions in solutions: a) neutral; b) weakly acidic; c) slightly alkaline; d) strongly acidic; d) highly alkaline?
Assignments for mastering the material
134. An aqueous solution of a certain substance has an alkaline medium. Which ions are more present in this solution: H+ or OH -?
135. Two test tubes contain solutions of nitrate acid and potassium nitrate. What indicators can be used to determine which test tube contains a salt solution?
136. Three test tubes contain solutions of barium hydroxide, nitrate acid and calcium nitrate. How to recognize these solutions using one reagent?
137. From the list above, write down separately the formulas of substances whose solutions have a medium: a) acidic; b) alkaline; c) neutral. NaCl, HCl, NaOH, HNO 3, H 3 PO 4, H 2 SO 4, Ba(OH) 2, H 2 S, KNO 3.
138. Rain water has pH = 5.6. What does this mean? What substance contained in the air, when dissolved in water, determines the acidity of the environment?
139. What kind of environment (acidic or alkaline): a) in a shampoo solution (pH = 5.5);
b) in the blood of a healthy person (pH = 7.4); c) in human gastric juice (pH = 1.5); d) in saliva (pH = 7.0)?
140. Coal used in thermal power plants contains compounds of Nitrogen and Sulfur. The release of coal combustion products into the atmosphere leads to the formation of so-called acid rain containing small amounts of nitrate or sulfite acids. What pH values are typical for such rainwater: more than 7 or less than 7?
141. Does the pH of a solution of a strong acid depend on its concentration? Justify your answer.
142. A solution of phenolphthalein was added to a solution containing 1 mol of potassium hydroxide. Will the color of this solution change if chloride acid is added to it in the amount of substance: a) 0.5 mol; b) 1 mol;
c) 1.5 mol?
143. Three unlabeled test tubes contain colorless solutions of sodium sulfate, sodium hydroxide and sulfate acid. The pH value was measured for all solutions: in the first test tube - 2.3, in the second - 12.6, in the third - 6.9. Which test tube contains which substance?
144. The student bought distilled water at the pharmacy. The pH meter showed that the pH value of this water was 6.0. The student then boiled this water for a long time, filled the container to the top with hot water and closed the lid. When the water cooled to room temperature, the pH meter detected a value of 7.0. After this, the student passed air through the water with a straw, and the pH meter again showed 6.0. How can the results of these pH measurements be explained?
145. Why do you think two bottles of vinegar from the same manufacturer may contain solutions with slightly different pH values?
This is textbook material
pH (from the English power Hidrogen - “Activity/strength of hydrogen”) is an indicator that is used to determine the ratio of acid (base) in any solution. The term is inextricably linked with the concept of acid-base balance (ABC).
Although in scientific terminology the concept of pH environment is applied to literally any solution, in modern popular science this term is used mainly to designate the ratio of acid and alkali in the human body.
What pH indicator can indicate a normal normal environment? It is recognized that at a pH of 7.0, the medium can be called “neutral” - the activity of positively charged ions and negatively charged ions in such a medium is the same. However, an acid-base balance is almost never formed in the human body - three slices of lemon are enough to tip the indicator towards increased acidity.
The human body is constantly fighting for the balance of the acid-base environment, trying to restore this balance through internal mechanisms if it is disturbed, since the absence of ASR can lead to undermining the functioning of the immune system.
The role of acid-base balance in the body's functioning
There are three states of the acid-base environment in the body: a balanced state of the environment, increased acidity (acidosis) and increased alkali content in the body (alkalosis).
Increased acidity leads to poor absorption of minerals by the body: magnesium, potassium - all of them are simply excreted from the body without having time to be absorbed. Increased acidity has a bad effect on the functioning of many organs, especially the gastrointestinal tract, kidneys and cardiovascular system. The main complications that can be caused by acidosis are:
Bone fragility (as a result of inability to absorb calcium);
- weight gain;
- kidney dysfunction;
- allergic reactions;
- decreased immunity;
- general weakness.
Most often, a person feels increased acidity in the intestines and stomach - a slight burning sensation or even heartburn that occurs after drinking a large amount of alcohol or eating lemon indicates increased acidity.
The opposite of high acidity is called alkalosis - an increased level of alkali in the body. In fact, it is not entirely easy to cause truly elevated levels of alkali in the body - most often this condition occurs after long-term use of drugs containing alkali. In addition, this condition does not contribute to the development of such serious problems as acidosis. Possible complications as a result of alkalosis:
Skin problems;
- smell from the mouth;
- problems with the intestines;
- possible occurrence of allergic reactions to some products.
The key to a balanced acid-base environment is a harmonious diet and aversion to alcohol (among those who like to “drink on Fridays,” the acid-base balance is approximately 1.5%-2.0% higher than those who don’t drink). To restore ASR, enzymes, vitamin complexes and mineral complexes are most often used, especially calcium in large dosages.
Can you imagine that the development of many diseases depends on one cause? Many nutritionists and herbalists now describe this hidden danger in two words: acid and alkali.
High acidity destroys the most important systems in the body and it becomes defenseless against diseases. A balanced pH environment ensures normal metabolic processes in the body, helping it fight diseases. A healthy body has a reserve of alkaline substances, which it uses when necessary.
What is pH?
The ratio of acid and alkali in any solution is called acid-base balance (ABC), although physiologists believe that it is more correct to call this ratio the acid-base state. ASR is characterized by a special pH indicator (power Hidrogen - “hydrogen power”), which shows the number of hydrogen atoms in a given solution. At a pH of 7.0, we speak of a neutral environment. The lower the pH level, the more acidic the environment (from 6.9 to 0).An alkaline environment has a high pH level (from 7.1 to 14.0).
The human body is 70% water, so water is one of its most important components. The human body has a certain acid-base ratio, characterized by pH (hydrogen) value. The pH value depends on the ratio between positively charged ions (forming an acidic environment) and negatively charged ions (forming an alkaline environment). The human body constantly strives to balance this ratio, maintaining a strictly defined pH level. When the balance is disturbed, many serious diseases can occur.
Check your acid-base balance with pH test strips
It is very important to pay attention in time to changes in the pH level of the internal environment of the body and, if necessary, take urgent measures.
Using pH test strips, you can easily, quickly and accurately determine your pH level without leaving home. If your urine pH level fluctuates between 6.0-6.4 in the morning and 6.4-7.0 in the evening, then your body is functioning normally. If the pH level in your saliva remains between 6.4-6.8 throughout the day, this also indicates the health of your body. The most optimal pH level of saliva and urine is slightly acidic, in the range of 6.4-6.5.
The best time to determine your pH level is 1 hour before a meal or 2 hours after a meal. Check the pH level 2 times a week 2-3 times a day.
Ignorance of your pH level can lead to dire consequences.
A) Increased acidity in the body.
An imbalance in the pH of the body in most people manifests itself in the form of increased acidity (acidosis condition). In this condition, the body poorly absorbs minerals such as calcium, sodium, potassium and magnesium, which, due to excess acidity, are excreted from the body. Vital organs suffer from a lack of minerals. If acidosis is not detected in time, it can harm the body unnoticed, but constantly for several months and even years. Alcohol abuse often leads to acidosis. Acidosis can occur as a complication of diabetes.
Acidosis may cause the following problems:
- Diseases of the cardiovascular system, including persistent vasospasm and decreased oxygen concentration in the blood.
- Weight gain and diabetes.
- Kidney and bladder diseases, stone formation.
- Decreased immunity.
- Increased harmful effects of free radicals, which can contribute to tumorigenesis.
- Bone fragility up to a hip fracture, as well as other disorders of the musculoskeletal system, such as the formation of osteophytes (spurs).
- The appearance of joint pain and pain in the muscles associated with the accumulation of lactic acid.
- General weakness.
B) Increased alkali content in the body.
With an increased content of alkali in the body, and this condition is called Alkalosis, as well as with acidosis, the absorption of minerals is impaired. Food is digested much more slowly, which allows toxins to pass from the gastrointestinal tract into the blood. An increased level of alkali in the body is dangerous and difficult to correct. As a rule, it is the result of the use of drugs containing alkali.
Urine pH test results show how well the body absorbs minerals such as calcium, sodium, potassium and magnesium. These minerals are called "acid dampers" because they regulate the level of acidity in the body. If the acidity is too high, the body does not produce acid. It should neutralize the acid. To do this, the body begins to borrow minerals from various organs, bones, etc. in order to neutralize excess acid that begins to accumulate in tissues. Thus, the acidity level is regulated.
Minerals are used to neutralize acids
Over the course of 7 years, a study was conducted at the University of California (San Francisco), where 9 thousand women were examined. The results showed that with constant elevated levels of acidity, bones become brittle. The specialists who conducted this experiment are confident that most of the problems of middle-aged women are associated with excessive consumption of meat and lack of consumption of vegetable foods. Therefore, the body has no choice but to take calcium from its own bones and use it to regulate the pH level.
().
Saliva pH value
It is also rational to know the pH level of saliva. Test results show the activity of enzymes in the digestive tract, especially the liver and stomach. This indicator gives an idea of the work of both the entire organism as a whole and its individual systems. Some people may have increased acidity in both urine and saliva - in which case we are dealing with "double acidity".
Blood pH value
Blood pH is one of the most stringent physiological constants in the body. Normally, this indicator can vary between 7.3b - 7.42. A shift in this indicator by even 0.1 can lead to severe pathology.
When the blood pH shifts by 0.2, a coma develops, and by 0.3, the person dies.
Maintain the correct pH balance for good health
The body is able to properly absorb and store minerals and nutrients only with the proper level of acid-base balance. It is in your power to help your body receive, rather than lose, nutrients. For example, iron can be absorbed by the body at a pH of 6.0-7.0, and iodine at a pH of 6.3-6.6. Our body uses hydrochloric acid to break down food. In the process of vital activity of the body, both acidic and alkaline decomposition products are required, and 20 times more of the former are formed than the latter. Therefore, the body’s defense systems, which ensure the invariability of its ASR, are “tuned” primarily to neutralize and remove, first of all, acidic decomposition products.
The main mechanisms for maintaining this balance are: blood buffer systems (carbonate, phosphate, protein, hemoglobin), respiratory (pulmonary) regulatory system, renal (excretory system.
It is in your best interest to maintain the correct pH balance.
Even the “most correct” program for selecting medicinal herbs will not work effectively if your pH balance is imbalanced.
How the body manages acidity levels
|
 |
What to do if the pH balance is normal?
The answer is simple - to help maintain this balance in a healthy zone. We offer a program that improves pH balance (with pH in urine and saliva equal to 6.4).
- Enzymes.
Without enzymes, the body is unable to regulate pH levels. They heal and improve digestion, the absorption of minerals increases (especially calcium).
For example Protease Plus, if taken on an empty stomach (between meals), improves the functioning of red blood cells, removes dead cells, destroys fat deposits, fragments of dead parasites, fungi, viruses and bacteria, as well as their toxins, which accumulate maximally in adipose tissue. This is the basis for the anti-inflammatory effect of enzymes.
Calcium is the most important mineral for regulating pH balance.
The drugs are especially useful
pH value (pH factor) is a measure of the activity of hydrogen ions in a solution, quantitatively expressing its acidity. When pH is not at optimal levels, plants begin to lose the ability to absorb some of the elements they need for healthy growth. All plants have a specific pH level that allows them to achieve maximum results when growing. Most plants prefer a slightly acidic growing environment (between 5.5-6.5).
Hydrogen index in formulas
In very dilute solutions, the pH value is equivalent to the concentration of hydrogen ions. Equal in magnitude and opposite in sign to the decimal logarithm of the activity of hydrogen ions, expressed in moles per liter:
pH = -lg
Under standard conditions, the pH value ranges from 0 to 14. In pure water, at a neutral pH, the concentration of H + is equal to the concentration of OH - and is 1·10 -7 mol per liter. The maximum possible pH value is defined as the sum of pH and pOH and is equal to 14.
Contrary to popular belief, pH can vary not only in the range from 0 to 14, but can also go beyond these limits. For example, at a hydrogen ion concentration = 10 −15 mol/l, pH = 15, at a hydroxide ion concentration of 10 mol/l pOH = −1.
It is important to understand! The pH scale is logarithmic, meaning that each unit of change equals a tenfold change in the concentration of hydrogen ions. In other words, a solution with pH 6 is ten times more acidic than a solution with pH 7, and a solution with pH 5 will be ten times more acidic than a solution with pH 6 and a hundred times more acidic than a solution with pH 7. This is means that when you are adjusting the pH of your nutrient solution and you need to change the pH by two points (for example from 7.5 to 5.5) you must use ten times more pH adjuster than if you only changed the pH by one point (from 7.5 to 6.5 ).
Methods for determining pH value
Several methods are widely used to determine the pH value of solutions. The pH value can be approximately estimated using indicators, measured accurately with a pH meter, or determined analytically by performing acid-base titration.
Acid-base indicators
To roughly estimate the concentration of hydrogen ions, acid-base indicators are widely used - organic dye substances, the color of which depends on the pH of the medium. The most well-known indicators include litmus, phenolphthalein, methyl orange (methyl orange) and others. Indicators can exist in two differently colored forms - either acidic or basic. The color change of each indicator occurs in its own acidity range, usually 1-2 units.
Universal indicator
To expand the working range of pH measurements, a so-called universal indicator is used, which is a mixture of several indicators. The universal indicator sequentially changes color from red through yellow, green, blue to violet when moving from the acidic region to the basic one.
Solutions of such mixtures - “universal indicators” - are usually impregnated with strips of “indicator paper”, with the help of which you can quickly (with an accuracy of pH units, or even tenths of pH) determine the acidity of the aqueous solutions under study. For a more accurate determination, the color of the indicator paper obtained when applying a drop of solution is immediately compared with the reference color scale, the appearance of which is presented in the images.
Determining pH by the indicator method is difficult for cloudy or colored solutions.
Given the fact that the optimal pH values for nutrient solutions in hydroponics have a very narrow range (usually from 5.5 to 6.5), I also use other combinations of indicators. For example, ours has a working range and scale from 4.0 to 8.0, which makes such a test more accurate in comparison with universal indicator paper.
pH meter
The use of a special device - a pH meter - allows you to measure pH in a wider range and more accurately (up to 0.01 pH units) than using universal indicators. The method is convenient and highly accurate, especially after calibrating the indicator electrode in the selected pH range. It allows you to measure the pH of opaque and colored solutions and is therefore widely used.
Analytical volumetric method
The analytical volumetric method - acid-base titration - also provides accurate results for determining the acidity of solutions. A solution of known concentration (titrant) is added dropwise to the test solution. When they are mixed, a chemical reaction occurs. The equivalence point - the moment when there is exactly enough titrant to completely complete the reaction - is recorded using an indicator. Next, knowing the concentration and volume of the added titrant solution, the acidity of the solution is calculated.
Effect of temperature on pH values
The pH value can change over a wide range with temperature changes. Thus, a 0.001 molar solution of NaOH at 20°C has pH=11.73, and at 30°C pH=10.83. The effect of temperature on pH values is explained by different dissociation of hydrogen ions (H +) and is not an experimental error. The temperature effect cannot be compensated for by the electronics of the pH meter.
Adjusting the pH of the Nutrient Solution
Acidification of the nutrient solution
The nutrient solution usually has to be acidified. The absorption of ions by plants causes a gradual alkalization of the solution. Any solution that has a pH of 7 or higher will most often need to be adjusted to its optimal pH. Various acids can be used to acidify the nutrient solution. The most commonly used are sulfuric or phosphoric acid. A better solution for hydroponic solutions are buffer additives such as and. These products not only bring pH values to optimal levels, but also stabilize values for a long period.
When adjusting pH with both acids and alkalis, rubber gloves should be worn to avoid causing skin burns. An experienced chemist skillfully handles concentrated sulfuric acid; he adds the acid drop by drop to water. But for beginner hydroponists, it is perhaps better to contact an experienced chemist and ask him to prepare a 25% solution of sulfuric acid. While adding acid, the solution is stirred and its pH is determined. Once you know the approximate amount of sulfuric acid, you can then add it from a graduated cylinder.
Sulfuric acid must be added in small portions so as not to acidify the solution too much, which will then have to be alkalized again. For an inexperienced worker, acidification and alkalization can continue indefinitely. In addition to wasting time and reagents, such regulation unbalances the nutrient solution due to the accumulation of ions unnecessary for plants.
Alkalizing the Nutrient Solution
Solutions that are too acidic are made alkaline with sodium hydroxide (sodium hydroxide). As its name suggests, it is a caustic substance, so rubber gloves must be used. It is recommended to purchase sodium hydroxide in pill form. In household chemical stores, sodium hydroxide can be purchased as a drain cleaner, such as "Mole". Dissolve one pill in 0.5 liters of water and gradually add the alkaline solution to the nutrient solution with constant stirring, often checking its pH. No amount of mathematical calculations can determine how much acid or alkali should be added in a given case.
If you want to grow several crops in one tray, you need to select them so that not only their optimal pH coincides, but also their needs for other growth factors. For example, yellow daffodils and chrysanthemums require a pH of 6.8 but different humidity levels, so they cannot be grown in the same tray. If you give daffodils the same amount of moisture as chrysanthemums, the daffodil bulbs will rot. In experiments, rhubarb reached maximum development at pH 6.5, but could grow even at pH 3.5. Oats, which prefer a pH of about 6, produce good yields at a pH of 4 if the dose of nitrogen in the nutrient solution is greatly increased. Potatoes grow over a fairly wide pH range, but they grow best at a pH of 5.5. Below this pH, high tuber yields are also obtained, but they take on a sour taste. To obtain maximum high-quality yields, the pH of nutrient solutions must be accurately adjusted.
Loading...
