School Science Lessons
Topic 12d Bases, soaps, detergents, surfactants, water hardness
2009-09-13
Please send comments to: J.Elfick@uq.edu.au
See: Interesting websites
Table of contents
12.7.0 Bases, properties of bases, strong bases
12.12.0 Soaps and synthetic detergents, "syndets"
12.12.03 Surfactants
12.13.0 Hardness in water, water hardness
12.7.0 Bases, properties of bases, strong bases
12.7.1 Feel of alkalis
12.7.2 Solubility of alkalis
12.7.3 Alkalis with metals, sodium hydroxide
12.7.3.1 Recycle an aluminium drink-can as potassium aluminium sulfate, alum
12.7.4 Alkalis with salts, sodium hydroxide with copper salts
12.7.4.1 Alkalis with different salts, solubility of hydroxides
12.7.5 Alkalis with basic oxides, copper oxide
12.7.6 Alkalis with acidic oxides, carbon dioxide
12.7.7 Alkalis with amphoteric oxides and hydroxides
12.7.7.1 Alkalis with zinc chloride solution, sodium hydroxide
12.7.8 Alkalis with sodium carbonate
12.12 Soaps and synthetic detergents (syndets)
3.79 Prepare soap from fats
12.12.01 Prepare soap by neutralization
12.12.02 Prepare soap by saponification
12.12.03 Surfactants
12.12.04 Detergents
12.12.07 Laundry detergents
12.12.08 Machine dishwashing detergents
12.12.09 Scouring powders
12.12.10 Drain cleaners
12.12.11 Bleaches, disinfectants, deodorizers
12.12.1 Prepare soap with animal fats
12.12.2 Prepare soap with vegetable oils
12.12.3 Tests for glycerol
12.13.9 Prepare detergent, alcohol-based detergent
12.12.03 Surfactants
12.12.03.1a Ionic surfactants
12.12.03.2a Inorganic builders
12.12.03.2b Organic builders
12.12.03.3a Fluorescent whitening agents, optical bleaches, optical whites, fluorescers, "washing blue"
12.12.03.3b Foaming agents
12.12.03.4 Bleaches, sodium perborate bleach, catalase
12.12.03.5 Fillers
12.12.03.6 Enzymes
12.13 Hardness in water, water hardness
12.13.0.1 Temporary hardness and permanent hardness
12.13.0.2 Remove water hardness
12.13.0.3 Water hardness test
18.2.5 Salinity
12.13.1 Tests for water to form lather
12.13.2 Prepare hard water
12.13.3 Wash with hard water
12.13.4 Tests for hardness with different water samples
12.13.5 Tests for hard water to form a lather
12.13.6 Soften hard water by boiling
12.13.7 Soften hard water with chemicals
12.13.8 Use detergents instead of soap solution
12.13.10 Tests for hardness in water with standard soap solution
16.4.4 EDTA, ethylenediaminetetraacetic acid, C10H16N2O8
16.4.4.1 Ion exchange resins, deionized water
12.13.11 Tests for metal ions in water with EDTA, chelates
12.13.12 Water hardness using EDTA titration
12.13.13 Water softening using ion exchange resin
12.13.14 Make soap suds with hard water and soft water
12.7.0 Bases, properties of bases, strong bases
The strong bases are lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), rubidium hydroxide (RbOH), caesium hydroxide (CsOH).
Most bases dissolve in water releasing hydroxide ions (OH-) and react with acids to form salts. In the reaction with dilute sulfuric acid, the base copper (II) oxide the oxide accepts hydrogen ions. So you can say that a base is a proton acceptor.
CuO (s) + H2SO4 (aq) --> CuSO4 (aq) + H2O (l)
O2+ (g) + 2H+ (aq) --> H2O (l)
NaOH (s) --> Na+ (aq) + OH- (aq)
Weak alkalis do not completely ionize in water, e.g. pass ammonia gas through water to form dilute ammonia solution.
NH4OH (aq) <-- NH4+ (aq) + OH- (aq)
or, using the more modern way of representing this reaction:
NH4OH (aq) <-- NH3 (aq) + H2O (l)
A basic oxide is a metal oxide, e.g. CuO. A basic hydroxide is a metal hydroxide that is insoluble in water, e.g. Mg(OH)2. A base can dissolve in water to form hydroxyl ions and react with acids to form salts. The term "base" includes the alkalis basic oxides and basic hydroxides. Alkalis are bases that are easily soluble in water. The most commonly used alkalis are sodium hydroxide (caustic soda) calcium hydroxide and dilute ammonia solution. An alkali is a hydroxide that dissolves in water to form a solution with pH > 7 and contains hydroxyl ions (OH-), e.g. NaOH. Alkalis are good electrolytes, turn red litmus blue, and feel slippery. When strong alkalis dissolve in water, they completely ionize.
Be careful! Strong alkalis may burn the skin and cause blindness if splashed in the eyes! Use safety glasses and nitrile chemical-resistant gloves.
NaOH (s) --> Na+ (aq) + OH- (aq)
Weak alkalis do not completely ionize in water, e.g. pass ammonia gas through water to form dilute ammonia solution. This solution is shown as NH3 (aq) + H2O (l) because while "NH4+" ions and" OH-" ions can be detected, "NH4OH" cannot be detected.
1. Add a little solid sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide separately to a little water in separate test-tubes. Shake the test-tubes. Which of the substances are soluble? Place your fingers around each test-tube to see if heat is being produced. You will have noticed that the alkalis are not equally soluble; the order of decreasing solubility is sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide.
2. Prepare sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution and barium hydroxide solution. Test each solution as follows:
2.1 Pour a small amount into a test-tube and place in it a piece of red and a piece of blue litmus paper.
2.2 Add a few drops of methyl orange solution.
2.3 Add a few drops of phenolphthalein solution. Record what happens in each case. The alkalis turn red litmus paper to blue, colourless phenolphthalein solution to red and methyl orange solution to yellow.
2.4 Add a little solid sodium carbonate.
Observe any changes in the solutions. No gas forms when sodium carbonate is added to solutions of the alkalis so they do not behave like acids. The white solids formed in the calcium hydroxide and barium hydroxide solutions are calcium carbonate and barium carbonate. A solid formed because of a chemical reaction in solution is called a precipitate.
12.7.1 Feel of alkalis
1. Feel some soap. It feels slippery because it contains alkalis. Prepare very dilute solutions of each sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide. Moisten your finger tips with each solution and rub your fingers together. What do you feel?
2. Wet your finger with the sodium hydroxide solution, feel it between your fingers, then wash them afterwards. Describe the feel. The solution has a soapy feel.
12.7.2 Solubility of alkalis
Add to the same amount of water in test-tubes solutions of: sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide. The relative solubility is in that order. Feel the heat of reaction.
12.7.3 Alkalis with metals, sodium hydroxide
Most metals do not react with alkalis. However, zinc or aluminium reacts with alkalis to form soluble zincate and hydrogen or soluble aluminate and hydrogen. Strong alkalis should not be stored in aluminium or zinc containers.
1. Add 5 mL of concentrated sodium hydroxide solution to test-tubes containing: copper, iron, aluminium, zinc. Heat gently if no reaction is observed. Test any gas from the reaction.
2. Add a small piece of aluminium foil to quarter of a test-tube of sodium hydroxide solution. Heat until bubbles of a gas appear but do not boil the solution. Test the gas by first trapping it in the test-tube and holding the mouth of the test-tube to the flame. Describe what you see. The gas at the mouth of the test-tube explodes with a squeaky pop sound. The gas formed is hydrogen gas. Aluminium reacts with sodium hydroxide to form sodium aluminate and hydrogen gas.
12.7.3.1 Recycle an aluminium drink-can as potassium aluminium sulfate, alum
Waste material can be converted to new substances but full recovery is seldom attained because of incomplete reactions and loss of partially soluble materials. In this experiment, conversion of aluminium scrap metal to alum crystals requires large quantities of sulfuric acid and potassium hydroxide.
Be careful! Use safety glasses and nitrile chemical-resistant gloves. Use 4 g of pieces of an aluminium drink-can cut into thin shavings. Put 150 mL deionized water in a 400 mL beaker. Slowly add 50 ML of 6 M potassium hydroxide solution. Add the shavings, put the beaker on a tripod stand and mat inside a fume cupboard, fume hood. Heat the mixture gently over a small flame for 30 minutes to dissolve most of the aluminium metal. Adjust the flame to keep a controlled bubbling rate in the beaker. Use a glass stirring rod to prevent the metal shavings floating on top of the froth.
BE CAREFUL! KEEP YOUR FACE AWAY FROM THE CAUSTIC SPRAY!
When most of the aluminium has dissolved, turn off the Bunsen burner and filter the hot mixture through a funnel and glass wool plug to remove suspended paint, varnish and unreacted aluminium pieces. Collect the filtrate in a 400 mL, beaker. Cool the filtered solution to room temperature. Transfer the liquid to a 250 mL graduated cylinder to record the total volume of solution. Pour one quarter of this total volume into separate 150 mL beakers. With continuous stirring, acidify each portion of the solution by slowly pouring 20 mL, of 9 M sulfuric acid into the beaker. Be careful! Considerable heat is produced! If any lumps of aluminium hydroxide precipitate are present after adding the sulfuric acid, heat the mixture gently with stirring. Remove the heat when the mixture becomes clear. Cool the solution m an ice bath for about 20 minutes with frequent stirring. Crystals of alum, KAl(SO4)2.12H2O, form in the beaker. Set up a Buchner funnel with all the holes are covered. Clamp the flask to a ring stand, and connect the flask to a water aspirator. After the alum crystals have fully formed in the ice bath, turn on the aspirator and transfer the alum crystals from the beaker to the Buchner funnel. Wash the beaker with 20 mL of 60% ethyl alcohol / water solution to transfer any crystals remaining in the beaker. Add these washings to the Buchner funnel. Run the aspirator for several minutes, allowing the crystals to become moderately dry. Remove the filter paper and alum crystals from the Buchner funnel and put on a watch glass. Divide the mass of alum crystals recovered by the original mass of aluminium present in the solution to show the mass of alum crystals obtained per gram of aluminium metal. Theoretically, 17.5 g alum crystals can be obtained from 1.00 g of aluminium metal.
Calculate the percentage yield: = Actual mass alum recovered per g Aluminium / Theoretical mass alum recovered per g Aluminium
1. Dissolving the aluminium
2Al (s) + 2KOH (aq) + 6H2O (l) --> 2KAl(OH)4 (aq) + 3H2 (g)
2. Acidifying with sulfuric acid
2KAl(OH)4 (aq) + H2SO4 (aq) --> 2Al(OH)3 (s) + K2SO4 (aq) + 2H2O (l)
2Al(OH)3 (s) + 3H2SO4 (aq) --> Al2(SO4)3 (aq) + 6H2O (l)
3. Forming alum crystals
K+ (aq) + Al3+ (aq) + 2SO42- (aq) + 12H2O (l) --> KAl(SO4)2.12H2O (s)
12.7.4 Alkalis with salts, sodium hydroxide with copper salts
Add drops of 2 M sodium hydroxide solution to 2 M solutions: copper (II) sulfate, copper (II) chloride, copper (II) nitrate. In each case, a blue precipitate results. These solutions contain only the copper (II) ion in common so this ion is the cause of the blue precipitate. Add drops of barium chloride solution to: sulfuric acid, sodium sulfate. In each case the white precipitate is caused by the sulfate ion.
Ba2+ + SO42- --> BaSO4 (s)
12.7.4.1 Alkalis with different salts, solubility of hydroxides
Prepare solutions of collection of salts in separate test-tubes, e.g. magnesium sulfate, copper (II) sulfate, iron sulfate, potassium nitrate, calcium chloride. To each solution slowly add a small quantity of sodium hydroxide solution. Note the colour of any precipitate formed and any other change you may observe.
copper (II) sulfate (aq) + sodium hydroxide (aq) --> sodium sulfate (aq) + copper hydroxide (s)
copper ions (aq) + hydroxide ions (aq) --> copper hydroxide (s)
Hydroxide ions (hydroxyl ions) form precipitates with most metal ions. All metallic hydroxides are insoluble in water except sodium hydroxide, potassium hydroxide and ammonia solution. [Not "ammonium hydroxide, NH4OH". Ammonia solution is shown as NH3 (aq) because "NH4+" ions and "OH-" ions can be detected,
but "NH4OH" cannot be detected.] Calcium hydroxide and barium hydroxides are only slightly soluble. However, all substances dissolve in water to some extent so there is no sharp distinction between soluble and insoluble substances.
12.7.5 Alkalis with basic oxides, copper oxide
Basic oxides do not react with alkalis.
Add a small quantity, about the size of a split pea of sodium hydroxide solutions to: copper (I) oxide, calcium oxide, magnesium oxide, iron oxide. In each case there is no reaction.
12.7.6 Alkalis with acidic oxides, carbon dioxide
Acidic oxides react with alkalis to form salt and water.
1. Pass carbon dioxide bubbles through sodium hydroxide solution in a test-tube. Note the size of the bubbles. If the bubbles decrease in size as they rise through the solution, carbon dioxide is being used in a chemical reaction. Carbon dioxide combines with water to form carbonic acid, so a reaction of this acidic oxide with the alkali occurs.
NaOH (aq) + CO2 (g) --> Na2CO3 (aq) + H2O (l)
Add dilute hydrochloric acid. Test gases that form from the reaction with: moist litmus paper, a lighted splint, limewater. The production of carbon dioxide confirms that the reaction forms a carbonate.
HCl (aq) + Na2CO3 (aq) --> CO2 (g) + 2NaCl (aq) + H2O (l)
2. Pass a slow stream of carbon dioxide bubbles into the bottom of a measuring cylinder containing sodium hydroxide solution. Note any alteration in the size of the bubbles as they rise through the solution. After five minutes stop the flow of carbon dioxide and add 5 mL dilute hydrochloric acid. Test any gas liberated with a lighted splint, pieces of damp red and blue litmus paper, and limewater. The gradual decrease in the size of the ascending carbon dioxide bubbles shows that a reaction involving carbon dioxide occurs. Carbon dioxide and sulfur dioxide combine with water to form acids so you expect a reaction of these acidic oxides with dilute solutions of alkalis to occur. The production of carbon dioxide after adding hydrochloric acid to the solution in the measuring cylinder confirms this view because no gas is produced when hydrochloric acid reacts with sodium hydroxide, the only substance other than water originally present in the cylinder.
sodium hydroxide (aq) + carbon dioxide (g) --> water (l) + sodium carbonate (aq)
3. Pass carbon dioxide through barium hydroxide solution in a test-tube. Filter off the precipitate. Add dilute hydrochloric acid to the precipitate. Identify the gas liberated. The reaction forms barium carbonate.
12.7.7 Alkalis with amphoteric oxides and hydroxides
Oxides and hydroxides of Al, Pb, Sb, Sn, and Zn are amphoteric. An amphoteric oxide or hydroxide will neutralize an acid to form a salt and water, and will neutralize a base to form a salt and water. When amphoteric substances react with alkalis, they behave as acidic oxides. When amphoteric substances react with acids, they behave as basic oxides.
1. Add dilute sodium hydroxide solution to: aluminium oxide, zinc oxide, aluminium hydroxide, zinc hydroxide. Heat gently. Note any reactions.
ZnO (s) + 2NaOH (aq) --> Na2ZnO2 (aq) + H2O (l)
zinc oxide + sodium hydroxide --> sodium zincate + water
Al2O3 (s)  +  2NaOH (aq) --> 2NaAlO2 (aq) + H2O (l)
aluminium oxide + sodium hydroxide --> sodium aluminate + water
2. Repeat the procedure but using dilute sulfuric acid acid instead of dilute sodium hydroxide solution.
Al2O3 (s)  +  3H2SO4 (aq) --> Al2(SO4)3 (aq) + 3H2O (l)
aluminium oxide + sulfuric acid --> aluminium sulfate + water
12.7.7.1 Alkalis with zinc chloride solution, sodium hydroxide solution
The addition of aqueous sodium hydroxide to a test-tube containing zinc chloride solution will result in the formation of zinc hydroxide, a white precipitate. On addition of excess aqueous sodium hydroxide, the precipitate reacts with the sodium hydroxide to form a complex salt, sodium zincate
Zn(OH)2 + 2NaOH --> Na2Zn(OH)4
insoluble -->. soluble
The resulting zincate is soluble and so dissolves to give the colourless solution. However, many secondary school chemistry teachers, chemistry textbooks, and handbooks on qualitative analysis, would describe the above reaction of zinc hydroxide with excess sodium hydroxide as "a white precipitate forms that dissolves in excess sodium hydroxide to give a colourless solution". Students are taught that dissolving is a physical change as the solute can be recovered easily and that no new sub stances form. Thus the use of the word "dissolve" in the above situation may give students the notion that the disappearance of the precipitate is a physical change, when, in fact, it is a chemical reaction that occurred. The word "dissolve" has also been erroneously used to describe the following phenomena: 1. Reactions of excess aqueous sodium hydroxide with aluminium hydroxide, resulting in the formation of soluble sodium aluminate. 2. Reactions of aqueous ammonia with silver chloride, zinc hydroxide or copper (II) hydroxide resulting in the formation of soluble complex amines. 3. Reactions of acids with metals, insoluble bases, carbonates and sulfate (IV).
Chemists use the term "dissolve" loosely to mean the disappearance of a solid in a liquid, but they are aware of what is happening, that is, whether a reaction occurred or whether it is just solvation. However, secondary new substances form. The use of the word "dissolve" above may give students the notion that the disappearance of the precipitate is a physical change, when, in fact, it is a chemical reaction that occurred.
12.7.8 Alkalis with sodium carbonate
Add solid sodium carbonate to alkaline solutions. No gas forms. White precipitates of carbonates form only in the barium hydroxide solution and calcium hydroxide solution.
Na2CO3 (s) + Ca(OH)2 (aq) --> CaCO3 (s) + NaOH (aq)
12.12.0 Soaps and synthetic detergents (syndets)
Saponification is the process where fats are broken up by sodium hydroxide to form soaps and glycerol (glycerine, propane-1,2,3-triol). Soaps are the alkaline salts of fatty acids. Most soaps are a mixture of sodium stearate and sodium palmitate. Palmitic acid (C15H31.COOH) is found in vegetable oils. Octadecanoic acid, stearic acid [CH3(CH2)16.COOH] is found in mutton fat. Cis octadec-9-enoic acid (oleic acid, red oil, C17H33.COOH, cis-9-octadecanoic acid) occurs as glycerine ester of fats and oils and oxidizes on exposure to air and turns rancid yellow colour. Soft soaps are made from potassium salts and hard soaps are made from sodium salts. Metallic soaps are compounds of fatty acids with metal bases and used for waterproofing. Resin soaps are alkali salts of resins. Soap is not soluble in salt water. Soap dissolves in water to form sodium ions and stearate ions containing along chain of carbon atoms with a negatively charged group at one end that attracts water molecules. The other ends of the long carbon chains do not attract water molecules but can mix with non-polar compounds, e.g. oils and grease, and surround small oil droplets to be carried away in the wash. Dirt particles suspended in the grease and oil are also washed away. The small oil droplets become negatively charges, repel each other and so remain suspended in the washing water.
Sodium stearate is a salt of a weak acid so it produces slightly alkaline solutions, harmful to certain fabrics, when dissolved in water.
R(C=O)O- Na+ + H-OH <--> R(C=O)-OH + Na+OH-
In acid solutions, sodium stearate forms insoluble stearic acid and forms insoluble salts with Ca2+, Mg2+ and Fe3+ that precipitate as a curd-like "bath scum" and dark ring around shirt collars.
C17H35(C=O)O-Na+ + H+Cl-  --> C17H35(C=O)OH + Na+Cl-
sodium stearate [soluble] + HCl --> stearic acid [insoluble] + NaCl
C17H35(C=O)O-Na+ + Ca2+ --> (C17H35COO-)2Ca2+ + 2Na+
sodium stearate [soluble] + Ca2+ --> calcium stearate [insoluble] + 2Na+
or
Ca2+ +2CH3(CH2)16(C=O)O --> [CH3(CH2)16CO-]2Ca2+
Anionic detergents
The first anionic detergents were sodium salts of alkyl hydrogen sulfates
1. 3[CH3(CH2)10(C=O)OCH2] + 6H2 --> 3CH2(CH2)10CH2OH + HOCH2-HOCH-HOCH2
Glycerol trilaurate reduced to 1-dodecanol (lauryl alcohol) + glycerol
2. CH2(CH2)10CH2OH + HOSO2OH --> CH2(CH2)10CH2O(SO2)OH + H2O
1-dodecanol + sulfuric acid --> alkyl hydrogen sulfate + water
3. CH2(CH2)10CH2OSO2OH + NaOH --> CH3(CH2)10(S=O2)O-Na+ + H2O
Alkyl hydrogen sulfate neutralized with NaOH --> sodium lauryl sulfate [lipophilic chain: CH3(CH2)10, hydrophilic chain: (S=O2)O-Na+] + water
Modern detergents are straight chain alkyl benzene sulfonates that are biodegradable and do not accumulate in the environment.
RCH=CHR' + benzene --> [AlCl3 catalyst] RCHCH2R'- benzene --> + H2SO4 --> RCHCH2R'- benzene-SO3H --> + Na+ OH- --> RCHCH2R'- benzene-SO3-Na+ [lipophilic: RCHCH2R', hydrophilic: -SO3-Na+]
Also, detergents may be cationic, e.g. C18(CH3)3N+Cl-, neutral, e.g. C8 - benzene ring - O(CH2CH2O)5H, amphoteric C18(CH3)2N+CH2CO2-
12.12.01 Prepare soap by neutralization
RCOOH + NaOH --> RCOO-Na+ + H20, R = CH3(CH2)10-16
fatty acid + base --> Salt (soap) + water
12.12.02 Prepare soap by saponification
ester + alkali --> salts of carboxylic acids + alcohols
RCOOR' + NaOH --> RCOO-Na+ + R'OH
RCOOR' + OH- --> RCOO- + R'OH
Substitute KOH for NaOH to produce semi-solid soft soap. Substitute heavy metals to produce heavy metal stearates for lubricating oil, detergents and plastic manufacture, e.g. PVC
ester (fat) + base --> salt of fatty acid (soap) + alcohol, e.g. glycerol (glycerine) CH2OHCH(OH)CH2OH
Salt of fatty acids from beef tallow, sodium stearate CH3(CH2)16COO-Na+
Salt of fatty acid from palm oil, sodium palmitate CH3(CH2)14COO-Na+
1. Alkalis react with fats and cooking oils. For this reason sodium hydroxide (caustic soda) is used to remove fats and greasy deposits. Add a very small piece of lard (pig fat) or olive oil to half a large test-tube of sodium hydroxide solution. Boil very for a few minutes, keeping the test-tube moving over the flame so that the liquid does not spurt out. Wear eye protection and protective clothing. Pour the hot liquid into a clean test-tube, and add a quarter of a test-tube of clear, saturated, sodium chloride solution. Leave to cool. Describe what you see. A white precipitate of soap settles out from the liquid. When this process is carried out on a large scale in a soap factory, the soap is separated from the liquid and pressed into blocks. When sodium hydroxide reacts with fats, soap and glycerol (glycerine) form.
2. Use double decomposition to make metallic soaps. Separately boil a strong soap solution and an equally strong solution of a metallic salt, e.g. chloride or sulfide of Al, Cu, Fe, Mn, Zn . Mix the solutions and gather the soap on a linen cloth. Metallic soaps are used for varnishes, and waterproofing.
3. Make laundry soap. Melt lard at low heat and add sodium hydroxide solution, 200 g per litre, while stirring at constant low heat. until saponification occurs. If the soap does not separate from the solution, add more sodium hydroxide solution. To purify the soap, after separation pour off the sodium hydroxide solution, add water to the soap mass and heat until it dissolves and separate again with concentrated sodium hydroxide solution or common salt, sodium chloride. Melt the soap again in a water bath. Heat gently to expel water then pour into moulds.
4. Make a hot-stirred soap with potassium hydroxide. Olive oil 100 parts, solid potassium hydroxide 20 parts, deionized water 100 parts, 90% ethanol 20 parts. Boil the mixture in a steam bath until oil is saponified. Dissolve the soap formed in 300 parts deionized water then "salt out" the soap by adding 25 parts solid sodium hydroxide and 5 parts solid sodium carbonate in 80 parts deionized water.
12.12.03 Surfactants
Surfactants, surface-active agents, lower the surface tension of water on an item and allow more entry into tiny clacks and holes. Then other chemicals in the solution can react with the item.
CH3-CH=CH2 propylene --> CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH(CH3)-CH=CH(CH3) propylene tetramer
--> CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH(CH3)-CH=CH(CH3)benzine-SO3-Na+, alkylbenzene sulfonate (ABS) i.e. RSO3-Na+, similar to soap, RCOO-Na+
Surfactant molecule = hydrophobic, water insoluble chain of fatty acids + hydrophilic, water-soluble, charged end
1. Anionic surfactants have negative charge at the water-soluble end. Used in most domestic detergents and especially for washing glass, e.g. sodium dodecyl benzene sulfonate CH3(CH2)11C6H4SO2O-Na+.
Anionic surfactant molecules concentrate on the surface layers of water to lower the surface tension and allow the water to wet hydrophobic surfaces. The long hydrocarbon tail is soluble in non-polar substances, e.g. oil and the sulfonate group at the other end is soluble in water. So the surfactant molecule can lie across the oil water interface. The molecules aggregate into micelles with the hydrocarbon tails towards the centre leading to emulsification of oily dirt and its removal from the fabric being washed
2. Cationic surfactants have positive charge at the water-soluble end. Used in mild antiseptic throat medicine, algaecides, fabric softeners and washing plastics, e.g. CH3(CH2)15N(CH3)3+Br-
3. Non-ionic detergents have polyethylene oxide group in he molecule. The non-ionic polar groups in the molecule, e.g. -C2H4-O-C2H4-OH, form hydrogen bonds with water.
4. Amphoteric surfactants have positive and negative charge depending on pH. Used in hair conditioners
Surfactant system
1. Ionic surfactants | Non-ionic surfactants
2. Inorganic builders | Organic builders
3. Fluorescent whitening agents | Foaming agents
4. Bleaches
5. Fillers
6. Enzymes
12.12.03.1a Ionic surfactants
alpha olefin + benzene --> alkylbenzene + sulfuric acid (sulfonation) --> sulfonic acid + water
12.12.03.1b Non-ionic surfactants
1. Coconut diethanolamide
RCOOH + H2NCH2CH2OH -->RCONHCH2CH2OH + H2O (condensation reaction)
coconut oil fatty acids + monoethanolamine --> coconut diethanolamide (alkylamide) + water
2. Synthetic fatty alcohol ethoxylate
RCH2OH + (n-1) CH2OCH2 --> RCH2(OCH2CH2)nOH (condensation polymerization)
fatty alcohol + ethylene oxide --> fatty alcohol ethoxylate
12.12.03.2a Inorganic builders
1. Sodium tripolyphosphate, STPP, buffers water to milder pH and sequesters hard water ions, deflocculating action to keep clay type dirt in suspension
surface active agent surfactant
2Na2HPO4 + NaH2PO4 --> Na5P3O10 + 2H2O
disodium monohydrogen phosphate + monosodium dihydrogen phosphate --> pentasodium triphosphate (sodium tripolyphosphate)
However, zeolite / sodium carbonate / polycarboxylate builders, e.g. "Zeolite NAA" may replace polyphosphates where there is concern that adding phosphate to polluted water will cause growth of algae that cuts off the light to waterweeds and lead to fish death. In some countries there is an agreement to limit to < 5% phosphorus in detergents.
2. Sodium silicate (water glass) removes magnesium and some calcium and inhibits corrosion in washing machines.
12.12.03.2b Organic builders
cellulose + sodium hydroxide + chloroacetic acid --> sodium carboxymethyl cellulose
It acts as an anti-deposition agent on cellulose based fabrics, e.g. cotton and rayon, by increasing the negative charge in the fabric which then repels the negatively charged dirt particles.
12.12.03.3a Fluorescent whitening agents, optical bleaches, optical whites, fluorescers, "washing blue"
Blueing refers to the practice of adding "washing blue" to the washing water of sheets to neutralize any yellow colour by adding more blue colour so that the dry sheets would appear whiter. Cotton naturally ages to a yellow colour which does not fully reflect blue light from incident sunlight. These chemicals convert invisible ultraviolet light to visible blue light to give fabrics greater uniformity of reflectance and appear "whiter". A white shirt on sale in a shop may already contain fluorescers but they get washed out.
12.12.03.3b Foaming agents
Foam may be important in some detergents to hold up particles of removed dirt, e.g. in carpet and hair shampoos, but the suds may cushion the impact of blades in front loading washing machines and may expand up to cause shot circuits. Some detergents contain a "low suds" foaming agent because people think that a non-foaming detergent is not doing anything! Some detergents include soap to act as a water softener and surface active agent and also to rapidly collapse foam during the rinse cycle after wash. Soap for these purpose my be replaced by silicones.
12.12.03.4 Bleaches, sodium perborate bleach
The enzyme catalase catalyses the oxidation of substrates by hydrogen peroxide and, if no substrate, it breaks down any hydrogen peroxide to water.
Sodium perborate in water releases the powerful oxidizing agent hydrogen peroxide that removes most stains without harming textile fibres or removing dyes. However, sodium perborate is effective only at high temperatures and the enzyme catalase in some stains may destroy sodium perborate at low temperatures. The boron in detergent runoff in sewers may be poisonous to citrus crops. Bleach activators can bleach at lower temperatures, e.g. penta acetyl glucose, tetra acetyl ethylene diamine (TAED), sodium percarbonate, nonoyloxy benzene sulfonate (NOBS).
TAED activates "active oxygen" bleaching agents, e.g. sodium perborate, sodium percarbonate, sodium perphosphate, sodium persulfate, urea peroxide, to release hydrogen peroxide in the wash cycle by reacting with hydrogen peroxide to release peracetic acid, a fast-acting bleaching agent.
[CH3C(O))2NCH2CH2N[C(O)CH3]2 + H2O2 → [CH3C(O))2NCH2CH2NH(C(O)CH3] + CH3CO3H
12.12.03.5 Fillers
Calcium carbonate and other components provide bulk to the product.
12.12.03.6 Enzymes
Include alkaline proteases coated with polyethylene glycol that melts in the wash, amylases to breakdown starch glue and lipases to hydrolyse dirty fat.
12.12.04 Detergents
1. Detergents have the same action as soap but do not form precipitates with calcium and magnesium salts and so can be used in hard water.
2. Surfactants, surface active agents, are organic molecules with a lipophilic end and a polar end that emulsify and disperse oil and grease. Surfactants also lower the surface tension to improve the wetting of clothes so that dirt may be more easily removed. Surfactants do not precipitate in hard water. Cationic surfactants may act as fabric softeners.
3. Wetting agents, e.g. sodium lauryl sulfate, allow soap suds to form easily.
4. Builders, e.g. sodium tripolyphosphate, remove calcium and magnesium ions as a complex through chelation or by exchange these ions for sodium ions. Other builders used to avoid phosphate pollution by wastewater are sodium carbonate, sodium citrate and sodium silicate. Also, sodium aluminium silicate, a zeolite, may be used for calcium ion exchange.
5. Bleaches may be hypochlorite bleaches that allow chlorine to act as an oxidizing agent, or, to avoid pollution by residual chlorine, sodium perborate. NaBO3, may be substituted to allow bleaching by hydrogen peroxide produced by hydrolysis of the sodium perborate.
6. Enzymes may remove stains, e.g. protease enzymes to hydrolyse protein stains and amylase enzymes to dissolve starch based stains.
12.12.07 Laundry detergents
Dose 25 g / 30 L TO 100 G / 64 L
Percentage formulation: Anionics 15 to 35%, Non-ionics zero to 15%, Surfactants 15 to 49%, Phosphate (% STPP, inorganic builder sodium tripolyphosphate) zero to 30% (being replaced by zeolites) typical 4.5 g P per wash, self-regulation maximum 7.8 g P per wash, Zeolite (%) 10 to 30%, Alkaline builder 15 to 30%, Calcium carbonate mostly zero, used as a filler, Sodium carbonate to break up fatty soils, Sulfate zero to 30%, Enzyme zero to 1.5%, Bleach activator zero or various including perborate, Water 3 to 15%
Observe the labels of soaps, detergents, shampoos and washing powders and list their contents.
12.12.08 Machine dishwashing detergents
Example 1.: Phosphates >30%, Oxygen based bleaching agents 5-15%, Polycarboxylates <5%, Non-ionic surfactants <5%, Phosphonates, enzymes protease [may produce allergic reaction] amylase <5%
Detergent may be classified as IRRITANT [irritating to eyes and skin] With extremely hard waters above 26oC.
Example 2.: Anhydrous sodium tripolyphosphate >30%, Anhydrous sodium metasilicate 30% [dangerous if swallowed!] Anhydrous sodium carbonate 37.5% [ may dissolve glass] Low foam non-ionic surfactants < 0.5%, Sodium dichloriisocyanurate (56-64% available chlorine) 2% [may dissolve plastic] Corrosion inhibitors 9.5% [Includes aluminium salts, otherwise aluminium may be dissolved in machine dishwashing detergents]
12.12.09 Scouring powders
Abrasive powder 80% (screened silica, feldspar, calcite, limestone) sodium carbonate, surfactant + (chlorine bleach)
12.12.10 Drain cleaners, e.g. Drano
Sodium hydroxide + aluminium filings. They react in water to produce heat and saponify fat to release hydrogen gas.
Drain cleaners may contain crystals of sodium hydroxide (lye), sodium nitrate, sodium chloride (salt), and aluminium pieces. The sodium salt dissolve in the drain water to generate heat of solution. The sodium hydroxide solution reacts with fats in the drain to form soap. The aluminium pieces cut hair and dislodge deposits then react with sodium hydroxide to generate more heat. Sodium hydroxide solution removes the alumina (Al2O3) surface layer on the aluminium that reacts with water to produce hydrogen gas.
2NaOH + 2Al + 2H2O --> + 2NaAlO2 + 3H2
Pressure from the hydrogen gas may also unclog drains.
The hydrogen reduces nitrate ion to ammonia.
2NO3-  + 9H2  --> 2NH3 + 6H2O
The water and sodium ions then regenerate sodium hydroxide and hydrogen.
12.12.11 Bleaches, disinfectants, deodorizers
Sodium, potassium, calcium, magnesium hypochlorites. Household bleach is usually 5% sodium hypochlorite NaOCl (made from chlorine gas + sodium hydroxide solution until pH = 7.).
12.12.1 Prepare soap with animal fats
Do not prepare soap in containers made of aluminium because aluminium reacts with sodium hydroxide. Use clean dripping from a butcher shop or boil hard animal fat (tallow) in water and remove the separated oil from the surface. Clean the separated fat by strain heated fat through layers of cloth. Weigh sodium hydroxide pellets equal to one third of the weight of fat. Weigh sodium chloride equal to twice the weight of fat. Melt the fat and slowly add sodium hydroxide solution with continuous stirring. Heat gently to avoid boiling over. Boil for 30 minutes then add the sodium chloride while stirring. This is called "salting out". When the mixture cools soap separates as a floating layer, skim off the soap, heat it again, and pour it into moulds, e.g. trays of match boxes. The reaction is much quicker if the fat is already dissolved in methylated spirit before adding the sodium hydroxide.
12.12.2 Prepare soap with vegetable oils
Pour 5 mL olive oil, 5 mL 30% sodium hydroxide solution and 3 mL ethanol into a small beaker. Put the small beaker into a lager beaker of water. Heat the larger beaker while stirring the smaller beaker for 20 minutes. Take out the small beaker and heat it directly to form a creamy paste. Add 5 mL hot saturated sodium chloride solution and stir. This is called salting out and it removes excess alkali. Leave to cool. Remove the solid that separates on the top of the mixture and wash the solid with water. Shake the solid with water and note whether it behaves in the same way as common soaps. Repeat the experiment with potassium hydroxide instead of sodium hydroxide to saponify the fat. Compare the behaviour of the two soaps when used for washing.
12.12.3 Tests for glycerol
Neutralize 10 mL of the sodium hydroxide solution with drops of dilute hydrochloric acid and filter. Evaporate most of the filtrate in a watch glass over boiling water then add 5 mL ethanol. Evaporate most of the solution. Heat the residue with solid potassium hydrogen sulfate. The sharp odour of acrolein, burning fat odour, confirms the presence of glycerol.
CH2OR1-CHOR2-CH2OR3+ 3NaOH -->CH2OH-CHOH-CH2OH + NaOR1-NaOR2-NaOR3
triglyceride fat + sodium hydroxide --> glycerol + soap
12.13.0 Hardness in water, water hardness
1. Hardness indicates the tendency of water to precipitate soap or form scale on heated surfaces and is expressed as the sum of Ca and Mg and
usually reported in equivalents of Ca carbonate. Fe, Al, Zn and Mn also can contribute to hardness and should be considered if present in unusual amounts. Hardness in water is a nuisance because it makes washing difficult and causes a precipitate of "fur" in kettles and "scale" in boilers. However, hard water is not dangerous to health. Some water authorities add salts to the town water supply to prepare it harder because it is believed that this may precipitate some harmful bacteria and other micro-organisms. Also, hard water may supply calcium in the diet. Natural spring water is often hard. The salts of fatty acids are insoluble in water except the sodium and potassium salts. When soap is added to water containing metal ions, other than sodium and potassium, ions, insoluble soaps form so removing the fatty acid ions from solution but forming a floating scum on the water.
2. The five units of measure commonly used in water analysis work are as follows:
2.1 milligrams per litre (mg / l)
2.2 parts per million (ppm, 1 ppm = 1 mg per litre)
2.3 grains per US gallon (gpg)
2.4 equivalents per million (epm)
2.5 grains per imperial gallon (gpg imp).
3. In the USA, hard water contains dissolved hardness minerals above 1 GPG (grains per gallon).
USA levels of hardness: soft water < 1 grain per gallon, slightly hard =1 to 3.5 grains per gallon, moderately hard = 3.5 to 7 grains per gallon, hard (very hard) = 7 to 10.5 grains per gallon, extremely hard > 10 grains per gallon. GPG (gpg) is a unit of weight, 1 / 7 000 of a pound, 1 gpg = 17.1 ppm or 1 grain per gallon is equivalent to 17.1 mg / L.
4. The hardness of water is a measure of the amount of minerals, primarily calcium and magnesium, it contains. Water softening, which removes these minerals from the water, may be desirable if large quantities of detergent are needed to produce a lather when doing laundry, or scale is present on the interior of piping or water tanks, laundry sinks or cooking utensils. Water that contains more than 200 mg / l (200 ppm) as calcium carbonate (12 grains per gallon) is considered to be hard and may cause plumbing and laundry staining problems. Three grains per gallon equals about 50 ppm. Methods used to soften hard water for home use are zeolite softening and reverse osmosis.
5. Hardness expressed in mg / l as CaCO3: 0 to 100 soft, 100 to 200 moderate, 200 to 300 hard, 300 to 500 very hard, 500 to 1 000 extremely hard.
6. Zeolite softening, ion exchange, exchanges calcium and magnesium ions in the water for sodium ions in the zeolite grains. When the exchange capacity of the zeolite is exhausted, it can be regenerated by passing a strong sodium chloride solution through it causing it to give up the calcium and magnesium ions and take up a new supply of sodium ions. However, only calcium, magnesium and small amounts of iron will be removed from the water so people on salt restricted diets or with high blood pressure may not be able to drink it. Reverse osmosis units remove water hardness through a straining action as hard water passes through a membrane that allows water molecules and only trace levels of contaminants to pass through it. Reverse osmosis units are slow and produce more waste water.
7. Hardness should not be confused with salinity. Water can be very soft with low levels of Ca and Mg, yet have a high salinity value from dissolved Na salts. Most ground waters have hardness values of less than 2000 mg / L. Hardness range in mg / L: 0-60 soft, 61-120 moderately hard, 121-180 hard, >180 very hard.
12.13.0.1 Temporary hardness and permanent hardness
Temporary hardness occurs when calcium hydrogen carbonate or magnesium hydrogen carbonate dissolves in water. When water with temporary hardness is boiled, the hydrogen carbonates decompose to form insoluble carbonates. They precipitate from the solution to leave "soft" water that forms a lather easily.
calcium hydrogen carbonate (aq) --> carbon dioxide + water (l) + calcium carbonate (s)
Permanent hardness in water occurs when calcium sulfate or magnesium sulfate dissolves in water. Boiling water with permanent harness does not affect the hardness.
12.13.0.2 Remove water hardness
Remove permanent or temporary hardness in water by adding sodium carbonate crystals (washing soda) to precipitate the calcium ions or magnesium ions as carbonates.
Other methods are used for removing metal ions:
1. Add calcium hydroxide.
2. Add sodium hexametaphosphate, e.g. Calgon, that reacts with the calcium and magnesium ions to produce soluble substances that do not react with soap.
3. Add chelating agents, e.g. Versene, the tetra sodium salt of ethylene-diamine tetra ethanoic acid, EDTA, that combines with unwanted metal ions.
4. Pass water through an ion exchange resin in an ion exchange column, e.g. zeolite (Permutit) that removes the calcium and magnesium ions from the water as insoluble solids. These chemicals "soften" water by removing all minerals to form demineralized water that is as free from ionic substances as deionized water.
The last two processes do not form a scum that can discolour laundry. The Permutit process is the best for producing drinking water.
The hardness of water depends on how much calcium and magnesium salts are present. In natural stretches of water, these salts are mainly hydrogen carbonates, besides sulfates, silicates, chlorides, nitrates and phosphates in much smaller amounts. On boiling the water, the hydrogen carbonates are almost entirely precipitated as insoluble carbonates, so the hardness caused by these salts decreases. The remaining hardness is non-carbonate hardness, permanent, hardness.
Ca(HCO3)2 --> CaCO3 + CO2 + H2O (in boiling water)
The sum of the carbonate (temporary) hardness and non-carbonated (permanent) hardness is the total hardness of water. It is expressed in degrees of hardness. One degree of hardness corresponds to a content of 10 mg of calcium oxygen per litre of water. In Germany this is symbolized by dH. Water with a hardness less than 4o dH is described as very soft. Water with a hardness of 8 to 12o dH is described as moderately hard, between 12 and 18o dH fairly hard, between 18 and 30o dH as hard, and above 30o dH very hard. Water hardness is important technically and from the point of view of health hygiene. It affects the taste of food and drink. Water with a hardness greater than 25o dH acts as a laxative. An increase in the hardness of water causes an increase in how much soap is used because of the formation of insoluble calcium and magnesium soaps that neither foam nor clean. Hardness also causes precipitation of chalk, boiler scale, in pipes and vessels. Very soft water tastes insipid and exerts a bad effect on tooth and bone formation.
12.13.0.3 Water hardness test
The test-tube of the water hardness test set is filled up to the 5 mL graduation mark with the water sample, a level spoonful of indicator powder is added, and the mixture is stirred. If calcium or magnesium salts are present, the water sample turns red-violet, in their absence it turns green. If a red-violet coloration is produced, i.e. if the water possesses a definite hardness, the tablets, each corresponding to 5o dH, added in succession until the colour of the water sample turns to green. Each individual tablet must be completely dissolved before the next one is added. To help this process, the tablets are crushed with the special tamping rod provided for this purpose. Since one table corresponds to 5 degrees of hardness, the exact end point from red-violet to green will usually be greatly exceeded. Repeat the test by first dissolving in the water sample one 5o dH tablet fewer than used in the preliminary test. As many 1o dH tablets are then added until the colour of the water sample just turns green. The degree of hardness of the water is obtained by adding up the hardness values of the tablets used, e.g. if three 5o dH tablets and two 1o dH tablets were used to produce the 0 colour change, the water has a total hardness of 17o dH. The hardness value of the tablets is shown on the package containing them. To find hardness exactly, i.e. to within 0.5o dH, fill the test-tube to the 10 mL mark, add two level spoonfuls of indicator powder, stir, and add tablets with half the hardness value, i.e. 2.5o or 0.5o dH, until the colour just turns green.
12.13.1 Tests for water to form lather
1. Prepare soap solution by dissolving 1 g of shavings of plain laundry soap in 100 mL of methylated spirit. Put 5 mL of deionized water or demineralized water in a test-tube. Test the solution by adding one drop of soap solution to the water. Put a stopper on the tube and shake the tube vigorously. If no lather occurs, add another drop of soap solution and shake again. Continue until a lather appears. Record the number of drops of soap solution needed to prepare a good lather.
2. Add soap flakes one by one to 25 mL of the water in a test-tube with a stopper.
The flakes are usually uniform in size. Count how many flakes must be added to the sample to form a good lather by shaking.
12.13.2 Prepare hard water
See 8.4.2: Heat limewater (calcium carbonate)
1. Temporary hardness
Pass carbon dioxide through limewater or blow through limewater until it turns milky, then turns clear again because of the excess carbon dioxide.
2. Permanent hardness
Dissolve 1 g per of magnesium sulfate-7-water crystals, Epsom Salts, in water. Dissolve 1 gram per of calcium sulfate-2-water crystals in water.
12.13.3 Wash with hard water
Only the sodium and potassium salts of fatty acids are soluble in water, but most are insoluble. If soap is added to water containing metal salts, insoluble soaps form as a greasy scum of calcium or magnesium stearate on the water and the soap cannot be used to remove grease and oil. The scum requires the use of extra soap to remove it and the dirt. This water is called "hard water" because it is hard to prepare a lather in it.
Try to wash the hands with hard water and soap. Use three samples of dirty cloth. Wash each simultaneously and with the same amount of soap in: tap water, hard water, groundwater or stream water. Dry the cloths and compare the results.
12.13.4 Tests for hardness with different water samples
Test different liquids for formation of a lather: Dilute solution of magnesium sulfate-7-water crystals, Dilute solution of calcium hydrogen carbonate, Suspension of calcium carbonate, tap water, rainwater or tank water, mineral water.
12.13.5 Tests for hard water to form a lather
1. Boil for 5 minutes, 5 mL of: 1. temporary hard water, containing calcium or magnesium hydrogen carbonate 2. permanent hard water, containing other soluble calcium or magnesium salts Test the liquids for formation of a lather.
2. Add sodium carbonate crystals (washing soda) to 5 mL of: 1. temporary hard water 2. permanent hard water. Test the liquids for formation of a lather.
3. Add a commercial water softener, e.g. Calgon, to: 1. temporary hard water 2. permanent hard water. Test the liquids for formation of a lather.
12.13.6 Soften hard water by boiling
Boiling temporarily hard water softens it by decomposing the calcium or magnesium hydrogen carbonates.
1. Test tap water for hardness. Boil the water sample for 5 minutes. A precipitate of calcium carbonate may form.
2. After cooling the water, test for hardness again. Note if a lather forms with less soap than before boiling.
3. Prepare temporary hard water and repeat the experiment.
4. Prepare permanently hard water and repeat the experiment.
Ca(HCO3)2 (aq) <--> CaCO3 (s) + H2O (l) + CO2 (g)
12.13.7 Soften hard water with chemicals
Adding sodium carbonate crystals (washing soda) removes both temporary hardness and permanent hardness in water.
1. Temporarily hard water: Test the harness. Add sodium carbonate crystals (washing soda) and shake. Note whether a precipitate forms. Test the hardness again.
Ca(HCO3)2 (aq) + Na2CO3 (aq) -->CaCO3 (s) + 2NaHCO3 (aq)
2. Permanently hard water: Prepare permanently hard water. Test the hardness. Add sodium carbonate crystals (washing soda) and shake. Note whether a precipitate forms. Test the hardness again.
CaSO4 (aq) + Na2CO3 (aq) --> CaCO3 (s) + Na2CO3 (aq)
MgSO4 (aq) + Na2CO3 (aq) --> MgCO3 (s) + Na2SO4 (aq)
3. Repeat the above experiments with Calgon or other commercially available chemical that softens water. Enter the results of the experiments on water softening in the table below. What can be concluded about the hardness of the different types of water used every day? What is the best way to treat the water used every day?
Type of water used and number of drops of soap solution to form lather
1. Untreated deionized water
2. Untreated tap water
3. Untreated temporary hard water
4. Untreated permanent hard water
5. Boiled temporary hard water
6. Boiled permanent hard water
7. Add sodium carbonate crystals (washing soda) to temporary hard water
8. Add sodium carbonate crystals (washing soda) to permanent hard water
9. Add Calgon to temporary hard water
10. Add Calgon to permanent hard water
12.13.8 Use detergents instead of soap solution
1. Wash clothes with 1. soap solution 2. household detergents. Compare the results. Some household detergents do not form lathers, so test the detergent before using it in this experiment.
2. Use two strips of cotton fabric weighted at one end. Put one strip in pure water and put the other strip in 0.1% surfactant solution. The pure water does not wet the cotton fabric so the strip remains upright. The surfactants wets the cotton fabric so it sinks.
3. Pour an equal thickness layer of olive oil into jars of pure water and a 0.1% surfactant solution. Close the jars, shake them and leave to stand. The oil rises to the surface of the pure water but remains emulsified and dispersed in the detergent solution.
12.13.9 Prepare detergent, alcohol-based detergent
1. Mix 3 drops of dodecan-1-ol (lauryl alcohol) with 2 drops of concentrated sulfuric acid in a test-tube. BE CAREFUL! Dodecanyl sulfate gel forms. Add 2 mL water and 1 drop of phenolphthalein solution.
Add drops of 10% sodium hydroxide solution and stir until the solution is just alkaline. Evaporate to dryness on a watch glass to prepare solid detergent. Shake the solid with water and note whether it behaves in the same way as common soaps.
2. Prepare dodecanyl sulfate and add phenolphthalein as before. Neutralize with 10% solution of triethanolamine. Shake this liquid detergent with water and note whether it behaves in the same way as common soaps.
H2SO4CH3(CH2)10CH2OH --> CH3(CH2)10CH2OSO2OH
dodecan-1-ol --> dodecanyl sulfate
NaOHCH3(CH2)10CH2OSO2OH --> CH3(CH2)10CH2OSO2ONa
dodecanyl sulfate --> sodium dodecanyl sulfate
12.13.10 Tests for hardness in water with standard soap solution
Standard soap solution is of such strength that 1 cc contains sufficient soap to exactly neutralize one milligram (o.001 g) of dissolved calcium carbonate. Soft water contains no mineral impurities. Rain water is the purest kind of natural soft water. Waters for domestic uses may be divided into two general classes; hard waters and soft waters. Hard waters can be either permanently hard, temporarily hard, or both permanently and temporarily hard. By hardness of water is meant its soap destroying or neutralizing power, which is due to the presence of carbonates or sulfates of or magnesia. A large degree of permanent hardness indicates a bad water. Permanently hard waters contain sulfates of lime or magnesia in solution. Temporarily hard waters contain carbonates of lime or magnesia in solution, and both permanently and temporarily hard waters contain sulfates and carbonates of lime or magnesia in solution.
1. Prepare soap solutions for estimating of hardness in water
Solution A: Dissolve 100 g of pure powdered soap in 1 litre of 80% methylated spirit. Leave it for a day.
Solution B: Dissolve 0.5 g of calcium carbonate in hydrochloric acid, density = 1.19. Add dilute ammonia solution so that litmus paper just turns blue. Dilute to 500 mL. (One mL is equivalent to 1 mg of calcium carbonate.) Titrate the solution A in the burette against solution B. Dilute solution A with 80% ethanol until 1 mL of the resulting solution is equivalent to 1 mL of solution B, after making allowance for the lather. This is the amount of standard soap solution needed to form a permanent lather in 50 mL of deionized water. One cubic centimetre of the adjusted solution is equivalent to 1 mg of calcium carbonate.
2. Mix 25 g of finely shredded castile soap (olive oil soap), with 1.0 litre methylated spirits and 0.5 litre of deionized water. Leave to cool for half a day with occasionally shaking, then filter. Test the solution with water of known hardness. Dilute with a methylated spits and water mixture  until the strength is correct.
3. To determine the degree of hardness in water, put 70 cc of water in a clean 2 litre glass bottle and slowly add standard soap solution while shaking the mixture. If a lather forms that disappears in soft water or remains as a curd in hard water will form, add more standard soap solution while shaking the bottle until the lather formed can stand for five minutes. The number of cc soap solution added, less one, indicates the hardness of the water in degrees. The 1 cc is deducted because even distilled water requires a small quantity of soap to make it lather.
4. Hardness of water is measured in degrees Clark, and each degree of hardness corresponds to one grain of carbonate of lime or magnesia to one English gallon of water.
Water character
 Hardness as
degrees
(Clark-Wanklyn) 		Hardness as
parts per 100,000 		Hardness as grains CaCO3 in UK gallon Hardness as grains
CaCO3 in USA gallon
Very soft 1 degree 1.4
 1 0.8
Moderately soft
 6 degrees
 8.6
 6
 5
Hard
 9 degrees
 13.0
 9
 7.6
Excessively hard
16 degrees
 23.0
 16
 13.4
5. Originally the hardness of water was defined as the capacity of water for destroying the lather of soap. The hardness was determined by a titration with a standard soap solution. Metal ions have the ability to cause hardness. Nowadays, water hardness means the total calcium and magnesium ion concentration expressed as calcium carbonate concentration. However, with an electrode, the total water hardness can be determined directly in the range of 1-1000 ppm as calcium carbonate.
12.13.11 Tests for metal ions in water with EDTA, chelates
The different forms of hardness are expressed as "calcium carbonate hardness". EDTA is [ethylene diamine tetra-acetic acid, HOOCCH2)2N(CH2)2N(CH2COOH)2]. The disodium salt of EDTA combines with metals to form chelates. Chelates are compounds where a multidentate ligand, e.g. as an enolate anion of a -diketone, is bound to a central atom of a co-ordination complex. EDTA is a complexone and is used in special soaps to remove metal contamination and as a chelating agent for analytical determination of metal contamination. It is available as "EDTA (0.5 M)" which is a concentrated volumetric solution for dilution to prepare 1 litre of 0.5 M standard solution.
1. Prepare a 0.01 M EDTA solution by dissolving 1.861 g in 500 mL water.
2. Prepare pH 11 buffer solutions by adding 7.0 g ammonium chloride solution to 57 mL of concentrated aqueous ammonia solution. Dilute to 100 mL. BE CAREFUL!
3. Prepare an approximate 0.01 M solution MgCl2.6H2O by dissolving 2 g in 1 litre.
4.. Eriochrome Black T or Erio T indicator is the indicator for determining Ca2+, Mg2+ and Zn2+ with EDT. Dissolve 0.2 g EDTA powder in aqueous ammonia solution. Pour 100 mL of the water to be tested in a conical flask on white paper. Add 1.0 mL of the Mg2+ solution, 3 drops of "Erio T" indicator solution and 1 mL of the buffer solution. Add drops of EDTA solution until a blue colour appears. 1 mL EDTA solution / 1.0 mg CaCO3.
Ca2+ + H2EDTA2 <--> CaEDTA2- + 2H+
12.13.12 Water hardness using EDTA titration
The usual form of EDTA used for measuring water hardness is Na2EDTA.2H2O, the ethylenediaminetetraacetic acid disodium dihydrate salt.
In this ion exchange reaction the EDTA is in the sodium form and only the cation Ca2+ is removed. Let RZ = the ion exchange resin.
2RZ-SO3- Na+ + Ca2+ <--> (RZ-SO3-)2Ca2+ + 2Na+
Make the following solution: 5.0 mL of water sample, 1.0 mL of 1.5 M NH3 / 0.3 M NH4Cl buffer, 0.1 mL of 2% ascorbic acid solution, 1.0 mL of 0.01 M Na2MgEDTA / 0.1 M NH3 solution, 3 drops of 0.1% Calmagite indicator. The buffer keeps the hydrogen ion concentration of the solution at the optimum value. The ascorbic acid solution prevents oxidation of the indicator. Titrate the solution with 0.01 M Na2EDTA (Na2EDTA.2H2O) until the colour of the solution changes from red to blue. Repeat with a blank titration 5.0 mL of deionized water instead of the water sample. Subtract the volume the blank titration from the volume of the water sample titration.
1. Calculate the water hardness in units of millimoles per litre, i.e. the sum of the calcium and magnesium ion concentrations.
2. Calculate the water hardness in units of parts per million of CaCO3 (ppm, 1 ppm = 1 mg per litre) i.e. milligrams of CaCO3 per litre, assuming that the ions titrated came from CaCO3. Magnesium usually also occurs in hard water but this second calculation is often used by water engineers for convenience.
(mg CaCO3 / L) = (mmol Ca2+ + Mg2+ / L) X (1 mol CaCO3 / mol Ca2+ + Mg2+) X (100 g CaCO3 / mol CaCO3)
12.13.13 Water softening using ion exchange resin
The charge on Ca2+ is greater than the charge on Na+ so the Ca2+ ions have a stronger attraction to -ve groups attached to the ion exchange resin.
Add 2 g of dry cation exchange resin to 50 mL of tap water sample. Rotate the mixture in a flask for 10 minutes to produce soft water. Titrate a 5.0 mL sample of the soft water with 0.0100 M Na2EDTA. Calculate the percentage of water hardness removed by ion exchange:
[(mmol / L (Ca + Mg) tap water - mmol / L (Ca + Mg) soft water) / mmol / L (Ca + Mg) tap water] X 100
The exchange capacity is usually found on the label of the bottle of resin, expressed in milli equivalents (meq) per gram of dry resin or in milliequivalents per milliliter of resin bed. For example for a resin of 1.7 meq / mL, 1 mL of resin can exchange about 1.7 mmol of charge (1.7 mmol of Nal ion or O.AS mmol of Call ion). The resin is expensive so keep it for regeneration by washing it in concentrated sodium chloride solution then washing it with water.
12.13.14 Make soap suds with hard water and soft water
Put 5 mL of the soft water in test-tube 1. Put 5 mL of tap water into test-tube 2. Put 5 mL of deionized water into test-tube 3. Add 5 mL of 0.1 % soap solution to each test-tube, insert a stopper and shake for 10 seconds. Compare the amount and stability of the foam. Note any insoluble calcium soap scum.