The use of essential acids. Acids: classification and chemical properties

Plan:

Introduction

• 1 Acid definition
• 2 Acid classification
• 3 Chemical properties of acids
• 4 Some common acids
  • 4.1 Inorganic (mineral) acids
  • 4.2 organic acids
• 5 Interesting Facts
Notes

Introduction

acids- complex substances that consist of hydrogen atoms that can be replaced by metal atoms, and acid residues. They get their name from the sour taste of most acids. V aqueous solutions they dissociate into a hydrogen cation (proton) and an acid residue anion.

According to Lewis, an acid is an electrolyte (a substance involved in reactions involving the transfer of an electron) that accepts an electron pair in a reaction with a base, that is, a substance that donates an electron pair (see Lewis acid). In the Bronsted-Lowry theory, an acid is a substance that donates a proton (a base is a substance that accepts a proton).

In the framework of the theory of electrolytic dissociation, an acid is an electrolyte, during the electrolytic dissociation of which only hydrogen cations are formed from cations.

Hydrochloric acid (in a glass)

1. Determination of acid

In 1778, the French chemist Antoine Lavoisier suggested that the acidic properties are due to the presence of oxygen atoms in the molecule. This hypothesis quickly proved to be untenable, since many acids do not have oxygen in their composition, while many oxygen-containing compounds do not exhibit acidic properties. Nevertheless, it was this hypothesis that gave the name to oxygen as a chemical element.

In 1839, the German chemist Justus Liebig defined acids as follows: an acid is a hydrogen-containing compound whose hydrogen can be replaced by a metal to form a salt.

The first attempt to create a general theory of acids and bases was made by the Swedish physicochemist Svante Arrhenius. According to his theory, formulated in 1887, an acid is a compound that dissociates in an aqueous solution to form protons (H+ hydrogen ions). The Arrhenius theory quickly showed its limitations; it could not explain many experimental facts. In our time, it has mainly historical and pedagogical significance.

Currently, the three theories of acid and base are most common. They do not contradict each other, but complement.

• By solvosystem theory, which was initiated by the work of American chemists Cady and Franklin, published in 1896-1905, an acid is a compound that gives in solution those positive ions that are formed during the solvent's own dissociation (H 3 O +, NH 4 +). This definition is good because it is not tied to aqueous solutions.
• By proton theory of acids and bases, put forward in 1923 independently by the Danish scientist Johannes Brönsted and the English scientist Thomas Lowry, acids - hydrogen-containing substances that give off positive hydrogen ions - protons during reactions. The weakness of this theory is that it does not include hydrogen-free substances that exhibit acidic properties, the so-called aprotic acids.
• By electronic theory, proposed in 1923 by the American physical chemist Gilbert Lewis, acid - a substance that accepts electron pairs, that is, an electron pair acceptor. Thus, in the Lewis theory, both a molecule and a cation having a low-energy free molecular orbital can be an acid.
• Pearson modified the Lewis theory taking into account the characteristics of the acceptor orbitals, introducing the concept of hard and soft acids and bases (Pearson's principle or the principle of HICA). Hard acids are characterized by high electronegativity and low polarizability of an atom carrying a free orbital, soft acids, respectively, are characterized by low electronegativity and high polarizability of an atom carrying a free orbital.

It should also be noted that many substances exhibit amphoteric properties, that is, they behave like acids in reactions with bases and as bases in reactions with a stronger acid.

2. Classification of acids

• By oxygen content
  • anoxic (HCl, H 2 S);
  • oxygen-containing (HNO 3).
• By basicity - the number of acidic hydrogen atoms
  • Monobasic (HNO 3);
  • Dibasic (H 2 SeO 4 , Azelaic acid);
  • Tribasic (H 3 PO 4, H 3 BO 3).
  • Quadruple (H 4 CO 4).
  • six basic
• By strength
  • Strong - dissociate almost completely, dissociation constants are greater than 1 × 10 −3 (HNO 3);
  • Weak - dissociation constant less than 1 × 10 −3 ( acetic acid K d \u003d 1.7 × 10 −5).
• By sustainability
  • Resistant (H 2 SO 4);
  • Unstable (H 2 CO 3).
• According to class chemical compounds
  • Inorganic (HBr);
  • Organic (HCOOH);
• By volatility
  • Volatile (H 2 S, HCl);
  • Non-volatile (H 2 SO 4);
• By solubility in water
  • Soluble (H 2 SO 4);
  • Insoluble (H 2 SiO 3);

3. Chemical properties of acids

• Interaction basic oxides with the formation of salt and water:

• Interaction with amphoteric oxides to form salt and water:

• Interaction with alkalis to form salt and water (neutralization reaction):

• Interaction with insoluble bases to form salt and water, if the resulting salt is soluble:

• Interaction with salts if precipitation occurs or gas is released:

• Strong acids displace weaker ones from their salts:

(v this case unstable carbonic acid is formed, which immediately decomposes into water and carbon dioxide)

• With nitric acid and concentrated sulfuric acid, the reaction proceeds differently:

• Organic acids are characterized by an esterification reaction (interaction with alcohols to form an ester and water):

For instance,

4. Some Common Acids

4.1. Inorganic (mineral) acids

• Nitrous acid
• Nitric acid
• Boric acid
• Hydrobromic acid
• Hydroiodic acid
• Iodic acid
• Iodic acid
• Sulphuric acid
• Hydrochloric acid
• Orthophosphoric acid
• Orthocarboxylic acid
• sulfurous acid
• Hydrosulphuric acid
• Hydrofluoric acid
• Hypochlorous acid
• Chloric acid
• Chlorous acid
• Perchloric acid
• Silicic acid
• Permanganic acid
• Carbonic acid
• Hydrocyanic acid
• Hydrofluoric acid
• Rhodanic acid
• Tio sulphuric acid
• Arsenic acid
• Molybdic acid
• Technetic acid (pertechnetic acid)
• Polonic acid
• plutonic acid (H 2 PuO 4)
• Metaphosphoric acid
• Chromic acid

4.2. organic acids

• Adipic acid
• Azelaic acid
• Acrylic acid
• Aconitic acid
• Ascorbic acid (vitamin C)
• Valeric acid
• Wine acid
• Hyaluronic acid
• Deoxyribonucleic acid (DNA)
• Caproic acid
• Lauric acid
• Lysergic acid
• Lemon acid
• Butyric acid
• Malonic acid
• Lactic acid
• Uric acid
• Formic acid
• Oleic acid
• Palmitic acid
• pyruvic acid
• propionic acid
• Salicylic acid
• Stearic acid
• Acetic acid
• Oxalic acid
• Apple acid
• succinic acid

5. Interesting facts

• The underground animal, the naked mole rat, has acid-insensitive skin cells even at pH less than 3.5.
• In a crocodile in the stomach, the pH is less than 0.5.

Acids are such chemical compounds that are capable of donating an electrically charged hydrogen ion (cation), as well as accepting two interacting electrons, as a result of which a covalent bond is formed.

In this article, we will consider the main acids that are studied in the middle classes of secondary schools, and we will also learn many interesting facts on various acids. Let's get started.

Acids: types

In chemistry, there are many different acids that have the most different properties. Chemists distinguish acids by their oxygen content, volatility, solubility in water, strength, stability, belonging to an organic or inorganic class of chemical compounds. In this article, we will look at a table that presents the most famous acids. The table will help you remember the name of the acid and its chemical formula.

So, everything is clearly visible. This table shows the most famous chemical industry acids. The table will help you remember the names and formulas much faster.

Hydrosulphuric acid

H 2 S is hydrosulfide acid. Its peculiarity lies in the fact that it is also a gas. Hydrogen sulfide is very poorly soluble in water, and also interacts with many metals. Hydrosulphuric acid belongs to the group of "weak acids", examples of which we will consider in this article.

H 2 S has a slightly sweet taste and a very strong smell of rotten eggs. In nature, it can be found in natural or volcanic gases, and it is also released when protein rots.

The properties of acids are very diverse, even if the acid is indispensable in industry, it can be very unhealthy for human health. This acid is highly toxic to humans. When a small amount of hydrogen sulfide is inhaled, a person wakes up with a headache, severe nausea and dizziness begin. If a person breathes a large number of H 2 S, this can lead to convulsions, coma or even instant death.

Sulphuric acid

H 2 SO 4 is a strong sulfuric acid that children get acquainted with in chemistry lessons as early as the 8th grade. Chemical acids such as sulfuric are very strong oxidizers. H 2 SO 4 acts as an oxidizing agent on many metals, as well as basic oxides.

H 2 SO 4 in contact with skin or clothing causes chemical burns, however, it is not as toxic as hydrogen sulfide.

Nitric acid

Strong acids are very important in our world. Examples of such acids: HCl, H 2 SO 4 , HBr, HNO 3 . HNO 3 is the well-known nitric acid. She found wide application in industry, as well as agriculture. It is used for the manufacture of various fertilizers, in jewelry, in printing photographs, in the production of medicines and dyes, as well as in the military industry.

Chemical acids such as nitric acid are very harmful to the body. Vapors of HNO 3 leave ulcers, cause acute inflammation and irritation of the respiratory tract.

Nitrous acid

Nitrous acid is often confused with nitric acid, but there is a difference between them. The fact is that it is much weaker than nitrogen, it has completely different properties and effects on the human body.

HNO 2 has found wide application in the chemical industry.

Hydrofluoric acid

Hydrofluoric acid (or hydrogen fluoride) is a solution of H 2 O with HF. The formula of the acid is HF. Hydrofluoric acid is very actively used in the aluminum industry. It dissolves silicates, etchs silicon, silicate glass.

Hydrogen fluoride is very harmful to the human body, depending on its concentration it can be a light drug. When it comes into contact with the skin, at first there are no changes, but after a few minutes, a sharp pain and a chemical burn may appear. Hydrofluoric acid is very harmful to the environment.

Hydrochloric acid

HCl is hydrogen chloride and is a strong acid. Hydrogen chloride retains the properties of acids belonging to the group of strong acids. In appearance, the acid is transparent and colorless, but smokes in air. Hydrogen chloride is widely used in the metallurgical and food industries.

This acid causes chemical burns, but it is especially dangerous if it gets into the eyes.

Phosphoric acid

Phosphoric acid (H 3 PO 4) is a weak acid in its properties. But even weak acids can have the properties of strong ones. For example, H 3 PO 4 is used in industry to recover iron from rust. In addition, phosphoric (or phosphoric) acid is widely used in agriculture - a wide variety of fertilizers are made from it.

The properties of acids are very similar - almost each of them is very harmful to the human body, H 3 PO 4 is no exception. For example, this acid also causes severe chemical burns, nosebleeds, and tooth decay.

Carbonic acid

H 2 CO 3 is a weak acid. It is obtained by dissolving CO 2 (carbon dioxide) in H 2 O (water). Carbonic acid is used in biology and biochemistry.

Density of various acids

The density of acids occupies an important place in the theoretical and practical parts of chemistry. Thanks to the knowledge of density, it is possible to determine the concentration of an acid, solve chemical problems, and add the correct amount of acid to complete the reaction. The density of any acid varies with concentration. For example, the greater the percentage of concentration, the greater the density.

General properties of acids

Absolutely all acids are (that is, they consist of several elements of the periodic table), while they necessarily include H (hydrogen) in their composition. Next, we will look at which are common:

1. All oxygen-containing acids (in the formula of which O is present) form water during decomposition, and also anoxic acids decompose into simple substances (for example, 2HF decomposes into F 2 and H 2).
2. Oxidizing acids interact with all metals in the metal activity series (only with those located to the left of H).
3. They interact with various salts, but only with those that were formed by an even weaker acid.

According to their physical properties, acids differ sharply from each other. After all, they can have a smell and not have it, as well as be in a variety of aggregate states: liquid, gaseous and even solid. Solid acids are very interesting for studying. Examples of such acids: C 2 H 2 0 4 and H 3 BO 3.

Concentration

The concentration is the quantity that determines quantitative composition any solution. For example, chemists often need to determine how much pure sulfuric acid is in dilute H 2 SO 4 acid. To do this, they pour a small amount of dilute acid into a beaker, weigh it, and determine the concentration from a density table. The concentration of acids is closely related to the density, often there are calculation tasks to determine the concentration, where you need to determine the percentage of pure acid in the solution.

Classification of all acids according to the number of H atoms in their chemical formula

One of the most popular classifications is the division of all acids into monobasic, dibasic and, accordingly, tribasic acids. Examples of monobasic acids: HNO 3 (nitric), HCl (hydrochloric), HF (hydrofluoric) and others. These acids are called monobasic, since only one H atom is present in their composition. There are many such acids, it is impossible to remember absolutely every one. You just need to remember that acids are also classified by the number of H atoms in their composition. Dibasic acids are defined similarly. Examples: H 2 SO 4 (sulphuric), H 2 S (hydrogen sulfide), H 2 CO 3 (coal) and others. Tribasic: H 3 PO 4 (phosphoric).

Basic classification of acids

One of the most popular classifications of acids is their division into oxygen-containing and anoxic acids. How to remember, without knowing the chemical formula of a substance, that it is an oxygen-containing acid?

All anoxic acids do not contain important element O is oxygen, but there is H in the composition. Therefore, the word "hydrogen" is always attributed to their name. HCl is a H 2 S - hydrogen sulfide.

But even by the names of acid-containing acids, you can write a formula. For example, if the number of O atoms in a substance is 4 or 3, then the suffix -n- is always added to the name, as well as the ending -aya-:

• H 2 SO 4 - sulfuric (number of atoms - 4);
• H 2 SiO 3 - silicon (number of atoms - 3).

If the substance has less than three oxygen atoms or three, then the suffix -ist- is used in the name:

• HNO 2 - nitrogenous;
• H 2 SO 3 - sulfurous.

General properties

All acids taste sour and often slightly metallic. But there are others similar properties which we will now consider.

There are substances that are called indicators. Indicators change their color, or the color remains, but its hue changes. This happens when some other substances, such as acids, act on the indicators.

An example of a color change is such a product familiar to many as tea, and lemon acid. When lemon is thrown into tea, the tea gradually begins to noticeably lighten. This is due to the fact that lemon contains citric acid.

There are other examples as well. Litmus, which in a neutral medium has a lilac color, turns red when hydrochloric acid is added.

With tensions up to hydrogen in the series, gas bubbles are released - H. However, if a metal that is in the tension series after H is placed in a test tube with acid, then no reaction will occur, there will be no gas evolution. So, copper, silver, mercury, platinum and gold will not react with acids.

In this article, we examined the most famous chemical acids, as well as their main properties and differences.

acids complex substances are called, the composition of the molecules of which includes hydrogen atoms that can be replaced or exchanged for metal atoms and an acid residue.

According to the presence or absence of oxygen in the molecule, acids are divided into oxygen-containing(H 2 SO 4 sulfuric acid, H 2 SO 3 sulfurous acid, HNO 3 nitric acid, H 3 PO 4 phosphoric acid, H 2 CO 3 carbonic acid, H 2 SiO 3 silicic acid) and anoxic(HF hydrofluoric acid, HCl hydrochloric acid (hydrochloric acid), HBr hydrobromic acid, HI hydroiodic acid, H 2 S hydrosulfide acid).

Depending on the number of hydrogen atoms in an acid molecule, acids are monobasic (with 1 H atom), dibasic (with 2 H atoms) and tribasic (with 3 H atoms). For example, nitric acid HNO 3 is monobasic, since there is one hydrogen atom in its molecule, sulfuric acid H 2 SO 4 – dibasic, etc.

There are very few inorganic compounds containing four hydrogen atoms that can be replaced by a metal.

The part of an acid molecule without hydrogen is called an acid residue.

Acid Residue they can consist of one atom (-Cl, -Br, -I) - these are simple acid residues, or they can - from a group of atoms (-SO 3, -PO 4, -SiO 3) - these are complex residues.

In aqueous solutions, acid residues are not destroyed during exchange and substitution reactions:

H 2 SO 4 + CuCl 2 → CuSO 4 + 2 HCl

The word anhydride means anhydrous, that is, an acid without water. For instance,

H 2 SO 4 - H 2 O → SO 3. Anoxic acids do not have anhydrides.

Acids get their name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H 2 SO 4 - sulfuric; H 2 SO 3 - coal; H 2 SiO 3 - silicon, etc.

The element can form several oxygen acids. In this case, the indicated endings in the name of the acids will be when the element exhibits the highest valence (the acid molecule has a large content of oxygen atoms). If the element exhibits a lower valence, the ending in the name of the acid will be “pure”: HNO 3 - nitric, HNO 2 - nitrous.

Acids can be obtained by dissolving anhydrides in water. If the anhydrides are insoluble in water, the acid can be obtained by the action of another stronger acid on the salt of the required acid. This method is typical for both oxygen and anoxic acids. Anoxic acids are also obtained by direct synthesis from hydrogen and non-metal, followed by dissolution of the resulting compound in water:

H 2 + Cl 2 → 2 HCl;

H 2 + S → H 2 S.

Solutions obtained gaseous substances HCl and H 2 S and are acids.

At normal conditions Acids come in both liquid and solid states.

Chemical properties of acids

Acid solutions act on indicators. All acids (except silicic acid) dissolve well in water. Special substances - indicators allow you to determine the presence of acid.

Indicators are substances of complex structure. They change their color depending on the interaction with different chemicals. In neutral solutions, they have one color, in solutions of bases, another. When interacting with acid, they change their color: the methyl orange indicator turns red, the litmus indicator also turns red.

Interact with bases with the formation of water and salt, which contains an unchanged acid residue (neutralization reaction):

H 2 SO 4 + Ca (OH) 2 → CaSO 4 + 2 H 2 O.

Interact with based oxides with the formation of water and salt (neutralization reaction). The salt contains the acid residue of the acid that was used in the neutralization reaction:

H 3 PO 4 + Fe 2 O 3 → 2 FePO 4 + 3 H 2 O.

interact with metals. For the interaction of acids with metals, certain conditions must be met:

1. the metal must be sufficiently active with respect to acids (in the series of activity of metals, it must be located before hydrogen). The further to the left a metal is in the activity series, the more intensely it interacts with acids;

2. The acid must be strong enough (that is, capable of donating H + hydrogen ions).

During the course of chemical reactions of an acid with metals, a salt is formed and hydrogen is released (except for the interaction of metals with nitric and concentrated sulfuric acids):

Zn + 2HCl → ZnCl 2 + H 2;

Cu + 4HNO 3 → CuNO 3 + 2 NO 2 + 2 H 2 O.

Do you have any questions? Want to know more about acids?
To get the help of a tutor - register.
The first lesson is free!

site, with full or partial copying of the material, a link to the source is required.

acids

Acids are chemically complex substances whose molecules consist of an acid residue and hydrogen atoms (one or more). It is not for nothing that the words "sour" and "acid" are of the same root: according to their palatability all acids have a sour taste, which does not mean at all that acidic formulations can be tasted. Among them, more than half are caustic, and the rest are even toxic. There are, of course, exceptions - acetic, lemon, apple, ascorbic and oxalic, which are familiar to everyone since childhood, and they are successfully used in the food industry.

Whatever the origin of the acid (natural or synthetic), it will always have a certain number of hydrogen atoms in its structure, which can enter into reaction compounds. During chemical reaction each acid molecule will donate hydrogen atoms, and in return will accept atoms various metals. This is how substitution happens.

Acids are usually classified according to two criteria:

1. or there are oxygen atoms in the molecule,
2. by the number of hydrogen atoms that can be replaced by metal atoms.

The first group, in turn, has two subgroups:

- anoxic acids (hydrofluoric acid HF, hydrochloric HCl, hydrobromic HBr, hydroiodic HI, hydrosulfide H 2 S).
- oxygen-containing acids (sulfuric H 2 SO 4 , sulphurous H 2 SO 3 , phosphoric H 3 PO 4 , coal H 2 CO 3 , nitric HNO 3 , silicon H 2 SiO 3 ).

The second group also has several subgroups:

- monobasic acids (have 1 hydrogen atom),
- dibasic acids (have 2 hydrogen atoms),
- tribasic acids (have 3 hydrogen atoms).

The chemical properties of acids are described by the following rules:

1. Acids interact with bases, forming a salt, which will always contain an unchanged acid residue. This reaction is called neutralization. The second product formed during the course of the neutralization reaction is water.

For neutralization to take place, the following condition must be met: at least one of the components must be well soluble in water. And since acids perfectly match this parameter, they can interact with both insoluble and soluble bases. An exception is silicic acid, which is practically insoluble in water, therefore it can only react with soluble bases (KOH, NaOH).

2. Solutions of acids act on indicators (special substances), changing their color in water. Acids change the color of the indicator to one specific color, so you can always accurately determine that an acid is present in the composition of the substance.Thus, litmus and methyl orange will turn red.

Indicators are substances of a rather complex structure. In bases and neutral solutions, they will be a completely different color than in an acidic environment.

3. Acids react with metals when the following conditions are met:

- the metal on the scale of activity should be as reactive as possible. So silver, gold and copper will not react with acid, and zinc, calcium and sodium, on the contrary, will interact very actively. Moreover, a lot of hydrogen gases and a large amount of heat will be released.

Some metals will only react with dilute acids. If the acids are concentrated (anhydrous), then no substitution will occur.

acids- complex substances consisting of one or more hydrogen atoms that can be replaced by metal atoms, and acid residues.

Acid classification

1. According to the number of hydrogen atoms: number of hydrogen atoms ( n ) determines the basicity of acids:

n= 1 single base

n= 2 dibasic

n= 3 tribasic

2. By composition:

a) Table of oxygen containing acids, acid residues and corresponding acid oxides:

b) Table of anoxic acids

Physical properties of acids

Many acids, such as sulfuric, nitric, hydrochloric, are colorless liquids. solid acids are also known: orthophosphoric, metaphosphoric HPO 3 , boric H 3 BO 3 . Almost all acids are soluble in water. An example of an insoluble acid is silicic H2SiO3 . Acid solutions have a sour taste. So, for example, many fruits give a sour taste to the acids they contain. Hence the names of acids: citric, malic, etc.

Methods for obtaining acids

Chemical properties of acids

1. Change the color of the indicators

2. React with metals in the activity series up to H 2

(excl. HNO 3 -Nitric acid)

Video "Interaction of acids with metals"

Me + ACID \u003d SALT + H 2 (p. substitution)

Zn + 2 HCl \u003d ZnCl 2 + H 2

3. With basic (amphoteric) oxides – metal oxides

Video "Interaction of metal oxides with acids"

Me x O y + ACID \u003d SALT + H 2 O (p. exchange)

4. React with bases – neutralization reaction

ACID + BASE = SALT + H 2 O (p. exchange)

H 3 PO 4 + 3 NaOH = Na 3 PO 4 + 3 H 2 O

5. React with salts of weak, volatile acids - if an acid is formed that precipitates or a gas is released:

2 NaCl (tv.) + H 2 SO 4 (conc.) \u003d Na 2 SO 4 + 2HCl ( R . exchange )

Video "Interaction of acids with salts"

6. Decomposition of oxygen-containing acids when heated

(excl. H 2 SO 4 ; H 3 PO 4 )

ACID = ACID OXIDE + WATER (r. decomposition)

Remember!Unstable acids (carbonic and sulphurous) - decompose into gas and water:

H 2 CO 3 ↔ H 2 O + CO 2

H 2 SO 3 ↔ H 2 O + SO 2

Hydrosulphuric acid in products released as a gas:

CaS + 2HCl \u003d H 2 S+ CaCl2

TASKS FOR REINFORCEMENT

No. 1. Distribute chemical formulas acids in the table. Give them names:

LiOH , Mn 2 O 7 , CaO , Na 3 PO 4 , H 2 S , MnO , Fe (OH ) 3 , Cr 2 O 3 , HI , HClO 4 , HBr , CaCl 2 , Na 2 O , HCl , H 2 SO 4 , HNO 3 , HMnO 4 , Ca (OH ) 2 , SiO 2 , Acids

Bes-sour-

native

Oxygen-containing

soluble

insoluble

one-

main

two-core

tri-basic

No. 2. Write reaction equations:

Ca+HCl

Na + H 2 SO 4

Al + H 2 S

Ca + H 3 PO 4
Name the reaction products.

No. 3. Make the reaction equations, name the products:

Na 2 O + H 2 CO 3

ZnO + HCl

CaO + HNO3

Fe 2 O 3 + H 2 SO 4

No. 4. Make up the reaction equations for the interaction of acids with bases and salts:

KOH + HNO3

NaOH + H2SO3

Ca(OH) 2 + H 2 S

Al(OH)3 + HF

HCl + Na 2 SiO 3

H 2 SO 4 + K 2 CO 3

HNO 3 + CaCO 3

Name the reaction products.

SIMULATORS

Trainer number 1. "Formulas and names of acids"

Trainer number 2. "Correspondence: acid formula - oxide formula"

Safety Precautions - First Aid for Skin Contact with Acids

Safety -