What are acids and alkalis?
There is a group of chemicals called acids. These are all molecules containing hydrogen atoms. On the right is a list of certain acids you may come across. Click on each acid in turn to find out something about it.Acids are generally dangerous. Never drink them or put them near your eyes. Never pour water into a concentrated acid as it heats up and can spit hot acid at you. If you must dilute a concentrated acid with water, pour the acid slowly and gently into the water.
| Acids behave the way they do because they contain hydrogen ions (H+). In fact, acid molecules only contain these ions when they are dissolved in water. When they are pure, they consist of molecules, not ions. This is because hydrogen ions (which are lone protons) are unstable and can only exist if they can "hide" inside water molecules. When an acid turns from a molecule into ions, it is called DISSOCIATION. |
Strong and weak acids
Acids like sulphuric acid, nitric acid and hydrochloric acid are called strong acids. This means that they dissociate almost completely when dissolved in water, i.e. almost all of the acid is in the form of hydrogen ions and the negative ions associated with the acid (sulphate, chloride or whatever). However, weak acids such as ethanoic acid only dissociate partially. The covalent molecules break up into hydrogen ions and ethanoate ions, but these ions start to recombine to form covalent ethanoic acid. In this way, an equilibrium is set up in which the rate at which covalent ethanoic acid is breaking up to form ions is the same as the rate at which the ions are recombining to form the covalent molecules. We can write this equilibrium as a reversible equation with a double arrow to show that it proceeds in both directions at once:
CH3COO- (aq) + H+ (aq) A reaction similar to this occurs when any acid is dissolved in water, of course, but for strong acids the result is almost entirely dissociated ions (the right side of the equation).
pH SCALE
As the pH of a liquid goes down, it becomes more acidic (less alkaline).
As the pH of a liquid goes up, it becomes more alkaline (less acidic).
The pH scale goes from 0 (strongly acidic) to 14 (strongly alkaline) with pure water (neutral - neither acidic nor alkaline) at 7 in the middle.
The concentration of any solution is represented as moles per litre, i.e. how many moles of the chemical are present in 1 litre (1000 cm3) of water. (For a fuller explanation of moles, see the section on Moles and the Avagadro Constant). This concentration is then written as a power of 10.
For instance, pure water consists almost entirely of covalent molecules, although a tiny proportion of its molecules do split up to form hydrogen ions and hydroxyl ions. This means that the concentration of hydrogen ions is low, at 0.0000001 moles of hydrogen ions per litre, or 10-7 moles per litre.
A concentrated acid would have a much higher concentration of hydrogen ions, for instance, 0.01 moles of hydrogen ions per litre, which could be written as 10-2, and a strong alkali would have a lower concentration of hydrogen ions than even pure water, for instance, 0.0000000001 moles of hydrogen ions per litre, which could be written as 10-10.
Having written the concentration as a power of 10, we simply remove the base number 10 (we call this "taking the logarithm") together with the minus sign, to give the pH value, so a concentration of 10-7 moles per litre of hydrogen ions becomes a pH of 7 (not -7), which is the pH of water (or a neutral solution), and a concentration of 10-2 moles per litre becomes a pH of 2, and a concentration of 10-10 becomes a pH value of 10.Indicators
There is a device called a pH meter which you can dip into a liquid and which will measure its pH. However, it is easier to use an indicator.An indicator is a chemical that changes colour. Indicators are liquids, but they can be soaked into a type of paper similar to blotting-paper to form strips of indicator paper.
Just dip the indicator paper into the unknown liquid and it will change colour to show the pH.
The simplest indicator is Litmus (from the Litmus plant). It goes red in acids, blue in alkalis.
Universal indicator is a better indicator than litmus because it can show a greater range of colours. The chart below shows the approximate colour that universal indicator goes when put into liquids of different pH values.
Universal indicator is available as a liquid or soaked into absorbing paper. It is often used to work out the pH of soil samples to see which plants can be grown in a certain patch of ground.
There are other indicators, for example, methyl orange (which changes colour from colourless to orange at pH of about 3). They all have different pH values where they change colour, and each has its own uses.
ACID INDUSTRY
The term acid rain refers to what scientists call acid deposition. It is caused by airborne acidic pollutants and has highly destructive results.
Scientists first discovered acid rain in 1852, when the English chemist Robert Agnus invented the term. From then until now, acid rain has been an issue of intense debate among scientists and policy makers.
Acid rain, one of the most important environmental problems of all, cannot be seen. The invisible gases that cause acid rain usually come from automobiles or coal-burning power plants.
Acid rain moves easily, affecting locations far beyond those that let out the pollution. As a result, this global pollution issue causes great debates between countries that fight over polluting each other's environments.
For years, science studied the true causes of acid rain. Some scientists concluded that human production was primarily responsible, while others cited natural causes as well. Recently, more intensive research has been done so that countries have the information they need to prevent acid rain and its dangerous effects.
The levels of acid rain vary from region to region. In Third World nations without pollution restrictions, acid rain tends to be very high. In Eastern Europe, China, and the Soviet Union, acid rain levels have also risen greatly. However, because acid rain can move about so easily, the problem is definitely a global one.
BASES AND ALKALIEach molecule of water (H2O) is made of two hydrogen atoms and one oxygen atom.
Unless they are frozen into ice, water molecules don’t always stay stuck together. When in liquid form, they are always splitting apart then reforming again. This is called dissociation. H2O splits into two ions: OH– (or hydroxide) ions and H+ (hydrogen ions; sometimes also called protons).
Cascade
While employed by Procter & Gamble, Dennis Weatherby developed and received a patent for the automatic dishwasher detergent known by the tradename Cascade. He received his Masters degree in chemical engineering from the University of Dayton in 1984. Cascade is a registered trademark of the Procter & Gamble Company.
Ivory Soap
A soap maker at the Procter and Gamble company had no idea a new innovation was about to surface when he went to lunch one day in 1879. He forgot to turn off the soap mixer, and more than the usual amount of air was shipped into the batch of pure white soap that the company sold under the name The White Soap. Fearing he would get in trouble, the soap maker kept the mistake a secret and packaged and shipped the air-filled soap to customers around the country. Soon customers were asking for more "soap that floats." When company officials found out what happened, they turned it into one of the company’s most successful products, Ivory Soap.
Lifebuoy
The English company, Lever Brothers, an created Lifebuoy soap in 1895 and sold it as an antiseptic soap. They later changed its name to Lifebuoy Health Soap. Lever Brothers first coined the term "B.O." for bad odor as part of their marketing company for the soap.
Liquid Soap
William Shepphard first patented liquid soap on August 22, 1865. In 1980, the Minnetonka Corporation introduced the first modern liquid soap called SOFT SOAP brand liquid soap. Minnetonka cornered the liquid soap market by buying up the entire supply of the plastic pumps needed for the liquid soap dispensers. In 1987, the Colgate Company acquired the liquid soap business from Minnetonka.
Palmolive Soap
William Colgate started a candle and soap making company in New York City in 1806. By 1906, the company was making over 3,000 different soaps, perfumes and other products. For example, Colgate Dental Cream was introduced in 1877. In 1864, Caleb Johnson founded a soap company called B.J. Johnson Soap Co., in Milwaukee. In 1898, this company introduced a soap made of palm and olive oils, called Palmolive. It was so successful that that the B.J. Johnson Soap Co. changed their name to Palmolive in 1917. Another soap making company called the Peet Brothers Co. of Kansas City started in 1872. In 1927, Palmolive merged with them to became Palmolive Peet. In 1928, Palmolive Peet merged with Colgate to form Colgate-Palmolive-Peet. In 1953, the name was shortened to just Colgate-Palmolive. Ajax cleanser was one of their first major brand names introduced in the early 1940s.
Pine-Sol
Chemist, Harry A. Cole of Jackson, Mississippi invented and sold the pine-scented cleaning product called Pine-Sol in 1929. Pine-Sol is the biggest selling household cleaner in the world. Cole sold Pin-Sol shortly after its invention (now owned by Clorox Company) and went on to create more pine oil cleaners called FYNE PINE and PINE PLUS. Together with his sons, Cole started the H. A. Cole Products Co. to manufacture and sell his products. Pine forests surrounded the area where the Coles lived, providing an ample supply of pine oil.
S.O.S Soap Pads
In 1917, Ed Cox of San Francisco, an aluminum pot salesman, invented a pre-soaped pad with which to clean pots. As a way of introducing himself to potential new customers, Cox made the soap incrusted steel-wool pads as a calling card. His wife named the soap pads S.O.S. or "Save Our Saucepans." Cox soon found out that the S.O.S pads were a hotter product than his pots and pans.
Tide
In the 1920s, Americans used soap flakes to clean their laundry. The flakes performed poorly in hard water, leaving a ring in the washing machine, dulling colors, and turning whites gray. Procter & Gamble began an ambitious mission to change the way Americans washed their clothes. Researchers discovered two-part molecules which they called synthetic surfactants. Each part of the "miracle molecules" executed a specific function--one pulled grease and dirt from the clothes, while the other suspended dirt until it could be rinsed away. In 1933, this discovery was introduced in a detergent called "Dreft," but it could only handle lightly soiled jobs. The next goal was to create a detergent that could clean heavily soiled clothes. That detergent was Tide®.
Created in 1943, Tide detergent was the combination of synthetic surfactants and "builders." The builders helped the synthetic surfactants penetrate the clothes more deeply to attack greasy, difficult stains. Tide was introduced to test markets in October 1946 as the world’s first heavy-duty detergent. Consumer response was immediate and intense. Tide detergent outsold every other brand within weeks. It became so popular that store owners were forced to limit the quantity purchased per customer.
Tide detergent was improved 22 times during its first 21 years on the market, and Procter & Garketstill strives for perfection. Each year, researchers duplicate the mineral content of water from all parts of the United States and wash 50,000 loads of laundry to test Tide detergent’s consistency and performance.
Formula 409
Formula 409 all-purpose cleaner was invented in 1957.
How Does Soap Clean?
You may use it every day, but do you know how it works? Learn about emulsions, micelles, and soap scum! Then check out links to sites about bubbles, soapmaking, and the regulation of soap chemistry.
The History of Soap
A soap-like material found in clay cylinders during the excavation of ancient Babylon is evidence that soap making was known as early as 2800 B.C.
The History of Soapmaking
B. J. Johnson Company was making soap entirely of vegetable oils, palm and olive. The soap they produced became so popular, they renamed their company after the soap Palmolive.
Although the start of the synthetic detergent industry is not shrouded in the veils of history as were the beginnings of the soap industry, it is nevertheless not easy to pinpoint exactly when the first were invented.
OILS SLICKS
Oil slicks float on oceans and seas, covering them in a thick film of crude or refined petroleum oil. When freight ships carrying tens of thousands of tons of fuel crash, malfunction, or encounter harsh weather, they spill enormous amounts of oil into the water. Since oil and water don't mix, the oil spreads out into a layer that hovers, as one mass, on top of the ocean.
Thousands of oil slicks result from massive oil spills every year. Oil slicks are difficult to control or contain and even more challenging to clean up. Once formed, an oil slick becomes an unpredictable phenomenon. It might end up spreading, migrating, thinning or thickening, moving towards land or further out to sea. An international community of activists, organizers, and technical developers has formed to identify, manage, and eliminate the devastating oil slicks.
The fate of an oil slick is determined by many factors, including local and regional weather, ocean currents, tides when near a land mass, the relationship between air and water temperature, the chemical composition of the crude or refined oil, wind direction, and the presence of icebergs. Humans must intervene with tracking devices, booms, absorbent materials, and chemical treatments.
Oil slicks can be diverted or captured using floating booms. These are mechanical blockers that loop around the edges of the slick and possibly squeeze it away from land or relegate it to a controllable area. Sometimes slicks are lit on fire to burn them off. Other times, the physical barriers bring them to an area where they can be removed with sorbent booms. Using absorption or adsorption, the booms catch some of the oil manually. Most of it will be disposed, but some may be re-refined to use as fuel.
Not surprisingly, oil slicks cause untold damage to algae, seaweed, plant life, fish, birds, sea mammals, shellfish, and the soil and rocks on beaches. Oil sticks to everything, creating multiple mortal hazards. It can prevent dolphins or whales from breathing, drown birds that can't swim away, or intoxicate fish and animals that drink or eat it. Sand and rocks may need to be dug up and thrown away if oil seepage makes them impossible to clean. Even years after an area has been hit with an oil slick, the ecosystem shows evidence of the disaster with lower biomass and fewer species.
Various chemicals are available for industrial neutralization depending upon the application and whether you are neutralizing an acid or base liquid. In most cases, Sulfuric Acid (H2SO4) and Sodium Hydroxide (NaOH) will be used. The end-user must consider the concentration to be used, must carefully analyze all the chemistries involved, must review manufacturers’ warnings and instructions, and must consider common safety measures for hazardous liquids. Other chemicals may be preferred based upon the amount of waste, the pH extremes expected, operating costs, batch versus continuous considerations, secondary reactions that might occur with the waste chemicals, storage issues, and other process design concerns. Wastech Controls OMEGA acid or caustic neutralization systems and LabDELTA acid neutralization systems can be designed for use with all of the following chemicals.
The most common neutralizing chemicals are:
Acids:
Sulfuric Acid (H2SO4)
Carbon Dioxide (CO2) - which converts in water to Carbonic Acid (H2CO3)
Hydrochloric Acid (HCl)
Phosphoric Acid (H3PO4)
Nitric Acid (HNO3)Bases:
Caustic (NaOH) – also known as Caustic Soda
Calcium Hydroxide (CaOH2)
Calcium Carbonate (CaCO3) – also known as Lime or Limestone
Ammonium Hydroxide (NH4OH)
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The basic principle of neutralization of a base or acid requires either hydroxide ions (OH-)
in a base for neutralizing an acid or hydrogen ions (H+) in an acid for neutralizing a base.
Neutralization with Acid
Since most chemicals listed above will work to neutralize waste streams, cost considerations will often determine the selection. Sulfuric Acid (H2SO4) is by far the most common acid available and is generally less expensive. Concentration is also an issue. Sulfuric Acid is available in 98% concentrations and may be the most economical in this form but storage issues such as the types of tanks and secondary containment available, familiarity of operators in handling hazardous liquids, the dangers of refilling storage containers or procedures for transferring from bulk containers, may suggest 30% to 50% concentrations regardless of the increased costs.
Neutralization with Caustic
Liquid Caustic (NaOH) is most common in 50% concentrations. Because of safety issues, some customers, to avoid a hazardous liquid, may opt for passive neutralization via Lime or Limestone in its solid, mineral form, despite its bulk and weight. Sodium Hydroxide is often preferred because of its solubility. Unfortunately, the neutralization process also forms salts that are very soluble in water. This high solids content can affect pump selection and maintenance. Temperature can also be an issue since 50% NaOH will begin to freeze at temperatures below 60F. This will obviously interfere with the process. Often 25% NaOH is recommended since this lowers the freezing point to below that of water.
Neutralization with CO2
In cement pouring operations large amounts of alkaline wastewater are generated. Discharge authorities demand that such wastewater be treated on site. Carbon Dioxide (CO2), which converts to Carbonic Acid (H2CO3) in water, is an excellent choice for such applications since the site is temporary, the gas is non-hazardous, can be used in-line assuming retention and mixing is considered and is self-buffering so regardless of dosage it will not lower the pH below 7.5-7.0. There are numerous operating considerations for using CO2 which Wastech Controls has mastered and an OMEGA skid mounted solution can monitor and neutralize on demand saving chemical and operating costs.
Mixing chemicals is always potentially dangerous. Consider carefully if a hazardous gas may be formed during the neutralization process. The complexity of most proprietary processes and the possible changes to a waste stream during operations makes it impossible for Wastech Controls to recommend or specify a chemical for a particular process. Wastech engineers will offer solutions, but final suitability and safety concerns must be the responsibility of the end-user at the application site. Problems with neutralizing chemicals are uncommon but must be anticipated by the end-user or operator. Many safety features are built into Wastech's OMEGA neutralization systems.
SVANTE ARRHENIUS
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