Hydrogen peroxide should whiten the skin

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Hydrogen peroxide

H2O2

CAS 7722-84-1

Hydrogen peroxide

Hydrogen peroxide

Hazard classes + category
Oxidizing liquids 1 *
Corrosive to metals 1
Acute toxicity oral 4 *
Acute toxicity inhalation 4 *
Skin corrosion / irritation 1A *
Specific target organ toxicity 3 *
(* Gradations for dilutions)

HP rates (See note)

H 271, 290, 302, 314, 332, 335, 412
P 220, 235, 280.1-4, 301 + 330 + 331, 303 + 361 + 353, 305 + 351 + 338 + 310
These recommendations apply to concentrations above 70%

disposal
special instructions

Pictograms

GHS 03 *
GHS 05 *
GHS 07 *
Danger *

Remarks

properties

Manufacturing

use

print a label

Special notes for schools

Unstabilized hydrogen peroxide tends to explode spontaneously. Only the stabilized, 30% hydrogen peroxide solution should be stored in the school laboratory. It is stored in a brown bottle with a vent valve in a cool place protected from light. For student experiments in secondary level I, it is recommended to only use freshly prepared solutions up to a concentration of 10%. Pure hydrogen peroxide or a concentrated solution is not considered an explosive, but can be used to manufacture such substances (note). The private possession of hydrogen peroxide is only allowed up to a concentration of 12%, up to 35% the possession is subject to approval, in concentrations above that the private possession is prohibited.

Risk assessment Germany (also EU)
GBU Experimenting with hydrogen peroxide (up to 30%)
GBU Elephant toothpaste

Security assessment of Switzerland
GBU Experimenting with hydrogen peroxide (up to 30%)
GBU Elephant toothpaste

properties
Effect on the human body

Hydrogen peroxide irritates and corrodes eyes, skin and mucous membranes, even in diluted form. The light spots on the skin that appear on contact are a result of the oxygen that is created when the tissue is broken down and has a whitening effect. If the vapors are inhaled, inflammation of the mucous membranes and even pulmonary edema can occur. Ingestion causes burns to the esophagus. The release of oxygen in the stomach can lead to overstretching. In the event of foam formation, there is then a risk of suffocation. When absorbed into the blood through skin absorption or through the stomach, symptoms such as headache, dizziness, vomiting, diarrhea, cramps or general circulatory disorders occur.



Corrosive and bleaching effects of a diluted hydrogen peroxide solution on the skin.

Chemical-physical properties

Pure, anhydrous hydrogen peroxide is a clear liquid that appears slightly bluish in thick layers. Compared to water, the viscosity is higher. The liquid solidifies at −0.43 ° C to form needle-shaped, colorless crystals. It can be mixed with water in any ratio. Hydrogen peroxide can be distilled under reduced pressure without decomposition. Highly concentrated solutions can, however, explode spontaneously when heated and especially in the presence of heavy metal impurities. Because of this property, diluted and stabilized solutions are available commercially.


Concentration,
Mass percentage
Concentration,
Amount of substance
description
density
at 20 ° C
100 %42.63 mol / l"purely"1.45 g / cm3
35 %11.63 mol / l"concentrated"1.13 g / cm3
30 %9.79 mol / l
"concentrated"1.11 g / cm3
10 %2.97 mol / l"Diluted"1.01 g / cm3
3 %0.88 mol / l"Diluted"1.00 g / cm3


Dilute solutions below 30% must always be freshly prepared, as they decompose and the concentration is constantly decreasing. The diluted solutions also have a whitening effect and burn the skin. Due to its strong oxidizing effect, hydrogen peroxide is suitable for bleaching hair. It has a reducing effect on potassium permanganate, chlorinated lime or silver (I) oxide, most other substances are oxidized by hydrogen peroxide, for example sulphurous acid to sulfuric acid or alcohols to aldehydes.



If you put a hydrogen peroxide solution on a sliced ​​potato,
then a catalytic reaction is triggered and the hydrogen peroxide breaks down.

The commercially available 30% solution decomposes under the action of light and heat in the presence of catalysts such as dust, finely divided gold, silver or platinum, alkalis and biocatalysts to form water and oxygen. For this reason, stabilizers such as sodium phosphate or phosphoric acid are added to the commercially available liquid to prevent this decomposition.

2 H2O2 2 H2O + O2    ΔH = −98.3 kJ / mol

Hydrogen peroxide reacts with water to form fewer hydronium ions H3O+. The equilibrium is strong in the starting materials, so hydrogen peroxide is only a very weak acid:

H2O2 + H2O HO2 + H3O+

Hydrogen peroxide salts decompose almost completely with water to form hydrogen peroxide and the corresponding metal hydroxides. Bleaching agents such as sodium peroxide Na are of technical importance2O2and barium peroxide BaO2. Sodium peroxide is made by burning sodium in the air. Barium peroxide is suitable as an oxygen carrier when igniting thermite with an ignition agent. If manganese (IV) oxide is added to hydrogen peroxide, it decomposes, releasing oxygen. Manganese (IV) oxide acts as a catalyst. Oxygen can also be represented by immersing a platinized nickel sheet or by adding iron (III) salts to the hydrogen peroxide.



proof

The hydrogen peroxide can be detected by reacting with a titanium salt solution that has been digested by hot, concentrated sulfuric acid. This creates a yellow-orange complex. Conversely, the reaction with hydrogen peroxide also serves to detect titanium. A hydroxoperoxotitanium (IV) ion is formed, which causes the yellow-orange color:

[Ti (OH)3]+ + H2O2  [Ti (O2)OH]+ + 2 H.2O      


Hydrogen peroxide in nature

Hydrogen peroxide is an intermediate product in the metabolism. It arises in certain cell organelles called peroxisomes or microbodies. Through the participation of oxidizing enzymes, the oxidases, hydrogen peroxide is formed from hydrogen and oxygen. This is used as an oxidizing agent in the metabolism. Catalytically active enzymes, the catalases, break down the hydrogen peroxide in the peroxisomes again. The function of these cell organelles is to break down hydrogen peroxide, which is formed outside the organelles and can destroy cell membranes there as a cell poison. Hydrogen peroxide has a germicidal effect and can be used as a disinfectant. During fertilization, the female egg produces hydrogen peroxide shortly after the penetration of the first sperm and thus kills the subsequent sperm. The bombardier beetle uses hydrogen peroxide together with hydroquinone to make an effective weapon of defense.
Manufacturing
The first synthesis succeeded the French chemist Louis Jacques Thénard (1777-1857) in 1818 when he found barium peroxide BaO2with sulfuric acid added:

BaO2 + H2SO4  BaSO4 + H2O2

Until 1945, hydrogen peroxide was produced by the electrolysis of sulfuric acid. At the anode, the sulfuric acid oxidizes to peroxodisulfuric acid with formation of hydrogen (reaction 1). By hydrolyzing this product, sulfuric acid and hydrogen peroxide are recovered (reaction 2). This procedure was important for the construction of the V2 rocket during the Second World War.

Reaction 1: 2 H2SO4  H2S.2O8 + H2  
Reaction 2: H.2S.2O8 + 2 H.2O H2O2 + 2 H.2SO4

Today the industrial production takes place according to the anthraquinone process. In this process, atmospheric oxygen is hydrogenated at temperatures around 30 to 80 ° C. and five bar pressure using the hydrogenation agent anthrahydroquinone. The obtained anthraquinone is reduced to anthrahydroquinone with the help of a platinum catalyst and hydrogen:


use
Hydrogen peroxide is used to make bleach in laundry detergents. It is also used to bleach paper, cellulose, wood and textiles. The chemical industry uses it as a raw material for the production of glycerine, plasticizers, peroxides and epoxides. In the manufacture of silicon wafers, a mixture of hydrogen peroxide and sulfuric acid is used to clean the surface and to apply a very thin layer of oxide. Hydrogen peroxide is a popular oxidizing agent in the laboratory.

In the past, hydrogen peroxide was used occasionally as an oxidizing component in rocket fuels, for example in the British space rocket “Black Arrow”, which brought the first British satellite into orbit. In the German V2 rocket, hydrogen peroxide was decomposed with potassium permanganate to produce a propellant for the fuel pumps. The actual rocket fuel in the V2 was ethanol, which was mixed with liquid oxygen and ignited. Hydrogen peroxide is still used today as a fuel for submarines and torpedoes. Hydrogen peroxide can also be used to make the explosive triacetone triperoxide (TATP). This explosive was used, for example, in the terrorist attacks in Brussels in March 2016.

A 3% solution is suitable for disinfecting in the household area, medical solutions for gargling contain 0.3% hydrogen peroxide. When filling PET bottles in the beverage industry, a 35% solution is used to keep the product sterile. However, numerous other types of packaging, for example for milk or milk products, are also pretreated in this way. Mold growth in the interior can also be combated with hydrogen peroxide. Medicine uses it to sterilize devices.



Diluted hydrogen peroxide solutions are suitable for bleaching.

Even in ancient times, women tried to lighten their hair with alkaline solutions made from wood ash, lime or soda. In the past, the nobles used gold, silver or copper powders to make their hair appear bright or shiny. The English pharmacist E. H. Thiellay first demonstrated the bleaching of hair with hydrogen peroxide in 3% concentration in 1867 at an exhibition in Paris. When bleaching, the hydrogen peroxide destroys the color pigment melanin, which is responsible for the hair color, through oxidation. The bleaching may only be carried out by qualified personnel, as improper use can destroy the hair roots. The commercially available bleaching powders also contain ammonia and persulfates, which make the hair swell and thus make it receptive to the bleaching agent. It is washed out with an acidic shampoo so that the natural pH value of the hair is restored.



In the upright cylinder there is a concentrated potassium iodide solution to which dishwashing detergent has been added.
If a 30% hydrogen peroxide solution is added, a reaction takes place with a sharp increase in volume.

Movie

From chemistry lessons, the reaction of hydrogen peroxide with a concentrated potassium iodide solution is known to produce "elephant toothpaste". A 30% hydrogen peroxide solution reacts with a concentrated potassium iodide solution. A tall, narrow cylinder, to which dishwashing detergent has been added, serves as the reaction container. The potassium iodide acts as a catalyst. All of the hydrogen peroxide is split into oxygen and water in a rapid reaction. The reaction is highly exothermic with the development of heat, so that the resulting gaseous products are mixed with the dishwashing detergent to form a yellow foam, the volume of which increases enormously. The yellow color in the foam indicates the formation of iodine.


Further information and media
Student experiments with hydrogen peroxide
Description and safe implementation of the demonstration elephant toothpaste


Create your own book: Basic text hydrogen peroxide

  

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