AlexBr 07-02-2010 09:30
There are two blades from our blacksmiths, shx 15 (bearing), I want to etch them with hydrochloric acid, I heard about the interesting results of this process.
They brought me acid, they said it was concentrated.
Now the question is how can I bring it up to 5-10% as needed for etching. Those. should I pour water there or into water and how much if the acid is 100 ml?
I understand the question is a loser, but I finished school and college a long time ago, and I don’t want to learn from my mistakes.
serber 07-02-2010 10:09
Only acid in water! In 1 liter of water 100 ml of HCl, we get a 10% solution
chief 07-02-2010 10:19
quote: Originally posted by serber:
Only acid in water! In 1 liter of water 100 ml of HCl, we get a 10% solution
We won’t get 10%!
Concentrated hydrochloric acid is not sulfuric acid; by definition it cannot be 100 percent, because hydrogen chloride is a gas.
Concentrated HCl - about 35-38 percent. Therefore, it is necessary to dilute approximately three times, and not ten times. If you need to be precise - by density:
http://ru.wikipedia.org/wiki/Hydrochloric acid
hunter1957 07-02-2010 10:29
The maximum achievable concentration of hydrochloric acid is 38-39%; then do the math yourself to get 5% acid. Regarding the etching of steel, there is such a thing that concentrated acids passivate the surface of the steel and the oxide film does not allow further etching.
pereira71 07-02-2010 11:41
Hello!
Now I’ll try to post a table with which you can calculate the percentage dilution of acids. Thanks to our Estonian colleagues.
Damn, it doesn't work...
If possible, then let me send it to someone for soap, and you can attach it. Excel file.
Nestor74 07-02-2010 12:55
pereira71
so put it somewhere on any file hosting service, and here it is, using cntrl-C cntrl-V, and that’s fine.
Kerogen 07-02-2010 13:32
quote: Originally posted by AleksBr:
Now the question is how can I bring it up to 5-10% as needed for etching. Those. should I pour water there or into water and how much if the acid is 100 ml?
Dilution calculator
pereira71 07-02-2010 13:54
While I was calving it was already done)))
Thanks Kerogen!
07-02-2010 16:28
Dilute 3-4 times, you will get what you need. What about
quote: Only acid in water!
I beg to differ, SALT can be stirred in any way you like. And SULFURIC acid is really only added to the water in a thin stream while stirring, and certainly in a container that will not crack due to strong heating of the mixture.
And to prepare solutions of other concentrations, I advise you to use the rule of the cross, look here for example
Approximate solutions. In most cases, the laboratory has to use hydrochloric, sulfuric and nitric acids. Acids are commercially available in the form of concentrated solutions, the percentage of which is determined by their density.
Acids used in the laboratory are technical and pure. Technical acids contain impurities and therefore are not used in analytical work.
Concentrated hydrochloric acid smokes in air, so you need to work with it in a fume hood. The most concentrated hydrochloric acid has a density of 1.2 g/cm3 and contains 39.11% hydrogen chloride.
The dilution of the acid is carried out according to the calculation described above.
Example. You need to prepare 1 liter of a 5% solution of hydrochloric acid, using a solution with a density of 1.19 g/cm3. From the reference book we find out that a 5% solution has a density of 1.024 g/cm3; therefore, 1 liter of it will weigh 1.024 * 1000 = 1024 g. This amount should contain pure hydrogen chloride:
An acid with a density of 1.19 g/cm3 contains 37.23% HCl (we also find it from the reference book). To find out how much of this acid should be taken, make up the proportion:
or 137.5/1.19 = 115.5 acid with a density of 1.19 g/cm3. Having measured out 116 ml of acid solution, bring its volume to 1 liter.
Sulfuric acid is also diluted. When diluting it, remember that you need to add acid to water, and not vice versa. When diluting, strong heating occurs, and if you add water to the acid, it may splash, which is dangerous, since sulfuric acid causes severe burns. If acid gets on clothes or shoes, you should quickly wash the doused area with plenty of water, and then neutralize the acid with sodium carbonate or ammonia solution. In case of contact with the skin of your hands or face, immediately wash the area with plenty of water.
Particular care is required when handling oleum, which is a sulfuric acid monohydrate saturated with sulfuric anhydride SO3. According to the content of the latter, oleum comes in several concentrations.
It should be remembered that with slight cooling, oleum crystallizes and is in a liquid state only at room temperature. In air, it smokes, releasing SO3, which forms sulfuric acid vapor when interacting with air moisture.
It is very difficult to transfer oleum from large to small containers. This operation should be carried out either under draft or in air, but where the resulting sulfuric acid and SO3 cannot have any effect harmful action on people and surrounding objects.
If the oleum has hardened, it should first be heated by placing the container with it in a warm room. When the oleum melts and turns into an oily liquid, it must be taken out into the air and then poured into a smaller container, using the method of squeezing with air (dry) or an inert gas (nitrogen).
When nitric acid is mixed with water, heating also occurs (though not as strong as in the case of sulfuric acid), and therefore precautions must be taken when working with it.
Solid organic acids are used in laboratory practice. Handling them is much simpler and more convenient than liquid ones. In this case, care should only be taken to ensure that the acids are not contaminated with anything foreign. If necessary, solid organic acids are purified by recrystallization (see Chapter 15 “Crystallization”),
Precise solutions. Precise acid solutions They are prepared in the same way as approximate ones, with the only difference that at first they strive to obtain a solution of a slightly higher concentration, so that later it can be diluted precisely, according to calculations. For precise solutions, use only chemically pure preparations.
Required quantity concentrated acids usually taken by volume calculated from density.
Example. You need to prepare 0.1 and. H2SO4 solution. This means that 1 liter of solution should contain:
An acid with a density of 1.84 g/cmg contains 95.6% H2SO4 n to prepare 1 liter of 0.1 n. of the solution you need to take the following amount (x) of it (in g):
The corresponding volume of acid will be:
Having measured exactly 2.8 ml of acid from the burette, dilute it to 1 liter in a volumetric flask and then titrate with an alkali solution to establish the normality of the resulting solution. If the solution turns out to be more concentrated), the calculated amount of water is added to it from a burette. For example, during titration it was found that 1 ml of 6.1 N. H2SO4 solution contains not 0.0049 g of H2SO4, but 0.0051 g. To calculate the amount of water needed to prepare exactly 0.1 N. solution, make up the proportion:
Calculation shows that this volume is 1041 ml; the solution needs to be added 1041 - 1000 = 41 ml of water. You should also take into account the amount of solution taken for titration. Let 20 ml be taken, which is 20/1000 = 0.02 of the available volume. Therefore, you need to add not 41 ml of water, but less: 41 - (41*0.02) = = 41 -0.8 = 40.2 ml.
* To measure the acid, use a thoroughly dried burette with a ground stopcock. .
The corrected solution should be checked again for the content of the substance taken for dissolution. Accurate solutions of hydrochloric acid are also prepared using the ion exchange method, based on an accurately calculated sample sodium chloride. The sample calculated and weighed on an analytical balance is dissolved in distilled or demineralized water, and the resulting solution is passed through a chromatographic column filled with a cation exchanger in the H-form. The solution flowing from the column will contain an equivalent amount of HCl.
As a rule, accurate (or titrated) solutions should be stored in tightly closed flasks. A calcium chloride tube must be inserted into the stopper of the vessel, filled with soda lime or ascarite in the case of an alkali solution, and with calcium chloride or simply cotton wool in the case of an acid.
To check the normality of acids, calcined sodium carbonate Na2COs is often used. However, it is hygroscopic and therefore does not fully satisfy the requirements of analysts. It is much more convenient to use acidic potassium carbonate KHCO3 for these purposes, dried in a desiccator over CaCl2.
When titrating, it is useful to use a “witness”, for the preparation of which one drop of acid (if an alkali is being titrated) or alkali (if an acid is being titrated) and as many drops of an indicator solution as added to the titrated solution are added to distilled or demineralized water.
The preparation of empirical, according to the substance being determined, and standard solutions of acids is carried out by calculation using the formulas given for these and the cases described above.
Instructions
Take a test tube that supposedly contains hydrochloric acid (HCl). Add a little to this container solution silver nitrate (AgNO3). Proceed with caution and avoid contact with skin. Silver nitrate can leave black marks on the skin, which can only be removed after a few days, and salt exposure on the skin acids may cause severe burns.
Watch what happens to the resulting solution. If the color and consistency of the contents of the test tube remain unchanged, this will mean that the substances have not reacted. In this case, it will be possible to conclude with confidence that the substance being tested was not .
If a white precipitate appears in the test tube, the consistency of which resembles cottage cheese or curdled milk, this will indicate that the substances have reacted. The visible result of this reaction was the formation of silver chloride (AgCl). It is the presence of this white cheesy sediment that will be direct evidence that initially there was indeed hydrochloric acid in your test tube, and not any other acid.
Pour some of the test liquid into a separate container and drop in a little lapis solution. In this case, a “curdy” white precipitate of insoluble silver chloride will instantly form. That is, there is definitely a chloride ion in the molecule of the substance. But maybe it’s not, after all, but a solution of some kind of chlorine-containing salt? For example, sodium chloride?
Remember another property of acids. Strong acids (and hydrochloric acid, of course, is one of them) can displace weak acids from them. Place a little soda powder - Na2CO3 - in a flask or beaker and slowly add the liquid to be tested. If there is a hissing sound immediately and the powder literally “boils”, there will be no doubt left - it is hydrochloric acid.
Why? Because this reaction is: 2HCl + Na2CO3 = 2NaCl + H2CO3. Carbonic acid is formed, which is so weak that it instantly decomposes into water and carbon dioxide. It was his bubbles that caused this “boiling and hissing.”
What is a hydrochloric acid solution? It is a compound of water (H2O) and hydrogen chloride (HCl), which is a colorless thermal gas with a characteristic odor. Chlorides dissolve well and break down into ions. Hydrochloric acid is the most famous compound that forms HCl, so we can talk about it and its features in detail.
Description
A solution of hydrochloric acid belongs to the class of strong. It is colorless, transparent and caustic. Although technical hydrochloric acid has a yellowish color due to the presence of impurities and other elements. The air “smoke”.
It is worth noting that this substance is present in the body of every person. In the stomach, to be more precise, in a concentration of 0.5%. Interestingly, this amount is enough for complete destruction razor blade. The substance will corrode it in just a week.
Unlike sulfuric acid, by the way, the mass of hydrochloric acid in solution does not exceed 38%. We can say that this indicator is a “critical” point. If you start to increase the concentration, the substance will simply evaporate, as a result of which hydrogen chloride will simply evaporate along with the water. Plus, this concentration is maintained only at 20 °C. The higher the temperature, the faster evaporation occurs.
Interaction with metals
A solution of hydrochloric acid can undergo many reactions. First of all, with metals that come before hydrogen in the series of electrochemical potentials. This is the sequence in which the elements proceed as their inherent measure increases, such as electrochemical potential(φ 0). This indicator is extremely important in half-reactions of cation reduction. In addition, it is this series that demonstrates the activity of metals in redox reactions.
So, interaction with them occurs with the release of hydrogen in the form of gas and the formation of salt. Here is an example of a reaction with sodium, a soft alkali metal: 2Na + 2HCl → 2NaCl +H 2.
With other substances, interactions proceed according to similar formulas. This is what the reaction with aluminum looks like: light metal: 2Al + 6HCl → 2AlCl 3 + 3H 2.
Reactions with oxides
Hydrochloric acid solution also interacts well with these substances. Oxides are binary compounds of an element with oxygen that have an oxidation state of -2. All known examples are sand, water, rust, dyes, carbon dioxide.
Hydrochloric acid does not interact with all compounds, but only with metal oxides. The reaction also produces soluble salt and water. An example is the process that occurs between an acid and magnesium oxide, an alkaline earth metal: MgO + 2HCl → MgCl 2 + H 2 O.
Reactions with hydroxides
This is the name given to inorganic compounds that contain a hydroxyl group -OH, in which the hydrogen and oxygen atoms are connected by a covalent bond. And, since a solution of hydrochloric acid reacts only with metal hydroxides, it is worth mentioning that some of them are called alkalis.
So the resulting reaction is called neutralization. Its result is the formation of a weakly dissociating substance (i.e. water) and salt.
An example is the reaction of a small volume of solution of hydrochloric acid and barium hydroxide, a soft alkaline earth malleable metal: Ba(OH) 2 + 2HCl = BaCl 2 + 2H 2 O.
Interaction with other substances
In addition to the above, hydrochloric acid can react with other types of compounds. In particular with:
- Metal salts that are formed by other, weaker acids. Here is an example of one of these reactions: Na 2 Co 3 + 2HCl → 2NaCl + H 2 O + CO 2. Shown here is the interaction with a salt formed by carbonic acid (H 2 CO 3).
- Strong oxidizing agents. With manganese dioxide, for example. Or with potassium permanganate. Such reactions are accompanied by the release of chlorine. Here is one example: 2KMnO 4 +16HCl → 5Cl 2 + 2MnCl 2 + 2KCl + 8H 2 O.
- Ammonia. This is hydrogen nitride with the formula NH 3, which is a colorless but pungent-smelling gas. The consequence of its reaction with a solution of hydrochloric acid is a mass of thick white smoke consisting of small crystals of ammonium chloride. Which, by the way, is known to everyone as ammonia (NH 4 Cl). The interaction formula is as follows: NH 3 + HCl → NH 4 CL.
- Silver nitrate - inorganic compound(AgNO 3), which is a salt of nitric acid and silver metal. As a result of the contact of a hydrochloric acid solution with it, a qualitative reaction occurs - the formation of a cheesy precipitate of silver chloride. Which does not dissolve in nitrogen. It looks like this: HCL + AgNO 3 → AgCl↓ + HNO 3 .
Obtaining the substance
Now we can talk about what is done to form hydrochloric acid.
First, by burning hydrogen in chlorine, the main component, hydrogen chloride gas, is obtained. Which is then dissolved in water. The result of this simple reaction is the formation of a synthetic acid.
This substance can also be obtained from exhaust gases. These are chemical waste (by-product) gases. They are formed through a variety of processes. For example, during the chlorination of hydrocarbons. The hydrogen chloride contained in them is called off-gas. And the acid obtained in this way, respectively.
It should be noted that in last years the share of waste substances in the total volume of its production increases. And the acid formed due to the combustion of hydrogen in chlorine is displaced. However, to be fair, it should be noted that it contains fewer impurities.
Use in everyday life
Many cleaning products that householders use regularly contain a certain proportion of hydrochloric acid solution. 2-3 percent, and sometimes less, but it is there. That is why, when putting the plumbing in order (washing tiles, for example), you need to wear gloves. Highly acidic products can harm the skin.
The solution is also used as a stain remover. It helps remove ink or rust from clothes. But for the effect to be noticeable, you need to use a more concentrated substance. A 10% hydrochloric acid solution is suitable. By the way, it removes scale perfectly.
It is important to store the substance correctly. Keep the acid in glass containers and in places where animals and children cannot reach. Even a weak solution that gets on the skin or mucous membrane can cause a chemical burn. If this happens, it is necessary to immediately rinse the areas with water.
In the field of construction
The use of hydrochloric acid and its solutions is a popular way to improve many construction processes. For example, it is often added to a concrete mixture to increase frost resistance. In addition, this way it hardens faster, and the resistance of the masonry to moisture increases.
Hydrochloric acid is also used as a limestone remover. Its 10% solution is The best way fighting dirt and marks on red brick. It is not recommended to use it to clean others. The structure of other bricks is more sensitive to the effects of this substance.
In medicine
In this area under consideration, the substance is also actively used. Dilute hydrochloric acid has the following effects:
- Digests proteins in the stomach.
- Stops the development of malignant tumors.
- Helps in the treatment of cancer.
- Normalizes acid-base balance.
- Serves as an effective remedy for the prevention of hepatitis, diabetes mellitus, psoriasis, eczema, rheumatoid arthritis, cholelithiasis, rosacea, asthma, urticaria and many other ailments.
Did you come up with the idea of diluting the acid and using it internally in this form, and not as part of medications? This is practiced, but it is strictly forbidden to do this without medical advice and instructions. By incorrectly calculating the proportions, you can swallow an excess of hydrochloric acid solution and simply burn your stomach.
By the way, you can still take medications that stimulate the production of this substance. And not only chemical ones. The same calamus peppermint and wormwood contribute to this. You can make decoctions based on them yourself and drink them for prevention.
Burns and poisoning
No matter how effective this remedy is, it is dangerous. Hydrochloric acid, depending on the concentration, can provoke chemical burns four degrees:
- There is only redness and pain.
- Blisters with clear liquid and swelling appear.
- Necrosis of the upper layers of skin is formed. The blisters fill with blood or cloudy contents.
- The lesion reaches the tendons and muscles.
If the substance somehow gets into your eyes, rinse them with water and then soda solution. But in any case, the first thing you need to do is call an ambulance.
Getting acid inside can cause sharp pains in the chest and abdomen, swelling of the larynx, vomiting bloody masses. As a result - severe pathologies of the liver and kidneys.
And the first signs of vapor poisoning include a dry, frequent cough, choking, damage to teeth, burning in the mucous membranes and abdominal pain. First urgent Care- this is washing and rinsing the mouth with water, as well as access to fresh air. Only a toxicologist can provide real help.
Hydrochloric acid is a solution of hydrogen chloride in water. Hydrogen chloride (HCl) at normal conditions colorless gas with a specific pungent odor. However, we are dealing with it aqueous solutions, so we will focus only on them.
Hydrochloric acid is a colorless transparent solution with a pungent odor of hydrogen chloride. In the presence of impurities of iron, chlorine or other substances, the acid has a yellowish-green color. The density of a hydrochloric acid solution depends on the concentration of hydrogen chloride in it; some data is given in table 6.9.
Table 6.9. Density of hydrochloric acid solutions of various concentrations at 20°C.
From this table it can be seen that the dependence of the density of a hydrochloric acid solution on its concentration can be described with an accuracy satisfactory for technical calculations by the formula:
d = 1 + 0.5*(%) / 100
When dilute solutions boil, the HCl content in vapor is less than in solution, and when concentrated solutions boil, it is greater than in solution, which is reflected in the figure below. rice. 6.12 equilibrium diagram. Constantly boiling mixture (azeotrope) at atmospheric pressure has a composition of 20.22% wt. HCl, boiling point 108.6°C.
Finally, another important advantage of hydrochloric acid is the almost complete independence of the time of its acquisition from the time of year. As can be seen from rice. No. 6.13, acid of industrial concentration (32-36%) freezes at temperatures that are practically unattainable for the European part of Russia (from -35 to -45 ° C), unlike sulfuric acid, which freezes at positive temperatures, which requires the introduction of a tank heating operation.
Hydrochloric acid does not have the disadvantages of sulfuric acid.
Firstly, ferric chloride has increased solubility in hydrochloric acid solution (Fig. 6.14), which allows you to increase the concentration of ferric chloride in the solution to 140 g/l and even more; the danger of sediment formation on the surface disappears.
Working with hydrochloric acid can be carried out at any temperature inside the building (even at 10°C), and this does not cause noticeable changes in the composition of the solution.
Rice. 6.12. Liquid – vapor equilibrium diagram for the HCl – H 2 O system.
Rice. 6.13. State diagram (fusibility) of the HCl–H 2 O system.
Rice. 6.14. Equilibrium in the HCl – FeCl 2 system.
Finally, another very important advantage of hydrochloric acid is full compatibility with a flux that uses chlorides.
Some disadvantage of hydrochloric acid as a reagent is its high volatility. The standards allow a concentration of 5 mg/m 3 of air volume in the workshop. Dependence of vapor pressure in equilibrium over different acids percentage concentration given in table 6.10. In general, when the acid concentration in the bath is less than 15% by weight, this condition is satisfied. However, when temperatures in the workshop rise (that is, in the summer), this indicator may be exceeded. Certain information about what acid concentration is permissible at a specific workshop temperature can be determined from rice. 6.15.
The dependence of the etching rate on concentration and temperature is shown in rice. 6.16.
Etching defects are usually caused by the following:
- using an acid with a higher or lower concentration compared to the optimal one;
- short etching duration (the expected etching duration at different acid and iron concentrations can be estimated from rice. 6.17;
- reduced temperature compared to optimal;
- lack of mixing;
- laminar movement of the etching solution.
These problems are usually solved using specific technological techniques.
Table 6.10. Dependence of the equilibrium concentration of hydrogen chloride on the acid concentration in the bath.
|
Acid concentration, % |
Acid concentration, % |
HCl concentration in air, mg/m3 |
|
|
200 (20°C) |
