Chemistry Experiments, L¶

The "anti-knock" additive to petroleum, the lead alkyl lead (IV) tetraethyl, Pb(C₂H₅)₄, lessens pre-ignition, "knocking" by inhibiting combustion reactions. source

It improves the octane rating of the petrol.

This "leaded petrol" is no longer made or used in Australias, because the compound causes lead poisoning and environmental pollution.

It is replaced by "unleaded petrol" that contains additional hydrocarbons to improve its octane rating, e.g. methanol and methyl tertiary butyl ether (MTBE).

However, some pollution is still produced by unleaded petrol.

3.61.9 Lead paint¶

Lead (II/IV) oxide, red lead, rust-proof primer paints

Lead paint formerly contained the white pigment "white lead", basic lead carbonate, Pb(OH)₂PBCO₃, nowadays replaced by titanium dioxide, (TiO₂). source

Ingestion and skin absorption of lead caused "lead poisoning", especially in young children sucking lead paint peeling off old walls.

Lead-based paints deteriorate leaving lead in the dust that can be inhaled.

Children can be exposed by eating lead-based paint chips, chewing on objects painted with lead-based paint, or swallowing house dust that contains lead.

"Lead in Paint" from the World Health Organization:

"No level of exposure to lead is considered safe.

The poisonous properties: of lead have been recognized since ancient times.

Today, lead is recognized as one of the twenty leading risk factors contributing to the global burden of disease.

Eliminating lead exposure from petrol has been one of the most significant environment health improvements in recent times.

Products containing lead are still widely made and sold across much of the developing world.

It is very likely that most of the world's people live in countries where exposure to high lead levels in paint is frequent.

Lead in paint is the second largest source of exposure to lead following exposure from petrol.

Paint containing lead is used in infrastructure like bridges, industry (car parts) and for marine uses, and also domestically.

The evidence of neurological damage, especially to children (whose intelligence can be impaired) and to workers in the lead industry is beyond doubt.

Adults can suffer renal and cardiovascular damage.

Some studies suggest a link to behavioural problems as well.

Lead damage is irreversible, and its effects appear to persist into adolescence and adulthood.

House dust is the commonest way in which children are harmed by lead in paint.

The lead remains a risk for many years after the paint has been used.".

12.7.11 Tests for lactic acid solution¶

1. Add lactic acid solution to the solution to sodium hydrogen carbonate (baking soda) in a test-tube.

Note the effervescence, because of the formation of carbon dioxide gas.

Test for carbon dioxide with limewater.

2. Heat lactic acid solution with iron filings.

Note the effervescence, because of the formation of hydrogen gas.

Increase the reaction by adding drops of copper sulfate solution.

However, it is difficult to obtain sufficient hydrogen to test by explosion with a glowing splint.

3. Boil 5 ml of lactic acid solution with two drops of dilute sulfuric acid.

Leave the solution to cool, then add it to a copper hydroxide precipitate from the reaction of copper sulfate with sodium hydroxide.

Heat the solution and observe a yellow precipitate, which turns red as copper (I) oxide (cuprous oxide) forms.

12.9.2 Reactions of lithium with water¶

Lithium reacts violently with water to form corrosive lithium hydroxide and hydrogen gas that, if mixed with air, may explode if ignited.

Lithium reacts vigorously with water and acids and so is usually stored under oil.

Lithium floats on paraffin oil so when returning a piece of lithium to the storage container shake the container to recoat the surface with the oil.

Handle lithium in the same way as you would handle sodium metal.

However, lithium is harder to cut than sodium so used a single piece strong scalpel, but do NOT use a scalpel with a disposable blade!

Lithium is toxic if ingested and corrosive to the skin.

2Li (s) + 2H₂O (l) → 2LiOH (aq) + H₂ (g) source

LPG, Liquefied Petroleum Gas

Liquefied petroleum gas, LPG

Bottled gas

Ethyl mercaptan: 16.9.2, (odorant in LPG)

LPG, LP-gas (bottled gas), hazards: 3.8.8

Petroleum gas: 16.8.8

Propane: 16.6.2.0

Thiophene: 16.10.14, (odorant in LPG)

Liquefied petroleum gas, LPG

LPG, Liquefied Petroleum Gas, LP gas, LPG gas, LP-gas, compressed gas, bottled gas, is a clean burning fuel and is stored in gas cylinders as bottled gas.

LPG is a simple asphyxiant.

LPG consists of propane (about 95%), together with varying proportions of butane, propylene and butylene.

A rank smelling compound, odorant, e.g. ethyl mercaptan, is added so that the presence of the gas can be easily detected.

Incomplete combustion forms carbon monoxide.

Do not search for a gas leak with a lighted match or lighted taper. but use a soap solution.

LP Gas is highly flammable, violently explosive mixture with air, toxic if inhaled, purchased as cylinders containing the liquefied gas.

Fill cylinders by weight only.

Hazchem Code 2YE

UN number 1075. Keep container upright in a well-ventilated place away from sources of ignition.

Bottled gas

Bottled gas, compressed gas, is gas in metal cylinders under pressure e.g. O₂ and N₂, and gas liquefied under pressure, e.g. C₄H₁₀ source

UK standard colours on cylinder shoulders (EN 1089-3):

See the internet for colours in your country e.g. EU Compressed Gas Cylinder colour codes.

Laboratory¶

Laboratory equipment

Laboratory items

Laboratory safety

Laboratory gas Piped gas, "lab gas", Household gas

Laboratory gas¶

In a laboratory, the pilot light should burn with a 90% blue flame.

If the flame is yellow, the gas may be contaminated with condensates.

Do not use such a gas, but immediately inform the local gas authority.

Lactic acid, C3H6O3, CH3CHOHCOOH¶

Lactic acid, C₃H₆O₃, CH₃CHOHCOOH source

Lactic acid

L-(+)-Lactic acid, 2-Hydroxypropionic acid, Sarcolactic acid, in sour milk, an α-hydroxy acid, skin irritant

16.1.2 Clot on boiling test (C.O.B test) (milk)

16.1.3 Alcohol test (milk)

16.1.5 Acidity test (milk)

16.1.10 Inhibitor test (milk)

16.2.4 Cheese making

19.2.1 Anatomy and physiology of meat:

Baking powder

E270 Lactic acid, Food acids, food additives)

E472b Lactic acid esters of monoglycerides

E326 Potassium lactate (Humectant, bulking agent, acidity regulator)

E328 Ammonium lactate (Humectant, bulking agent)

E329 Magnesium lactate (Humectant, bulking agent)

4.5.2 Lactase

Lactobacillus

Lactones

19.1.6 Leavening agents

12.7.10 Prepare lactic acid with milk

4.4.3 Prepare lactic acid with sourdough

4.4.4 Prepare lactose from milk or whey using immobilized lactase

4.3.17 Prepare yoghurt, test milk quality

12.7.11 Tests for lactic acid solution

8.5.28 Yoghurt and lactic acid bacteria, "Yakult"

Lactucin¶

Lactucin, C₁₅H₁₆O₅, lactucine, a secondary alcohol, a cyclic terpene ketone, a sesquiterpene lactone, a sedative, an antimalarial It occurs in chicory Cichoriumin, least lettuce (Lactuca saligna), and in wild lettuce (Lactuca virosa). source

Laminarin¶

Laminarin, C₁₉H₃₆O₁₆, β-1,3- and β-1,6-glucan, linear glucose polysaccharide produced by photosynthesis and used as food reserve by phytoplankton, e.g. diatoms. source

It occurs in oarweed, (Laminaria digitata), kombu, kelp horsetail, Family Laminariaceae, Class Phaeophyceae, Morocco.

(Laminaria japonica) was formerly the source of MSG, monosodium glutamate.

Lanthanum¶

Lanthanum, Table of the Elements

Lanthanum, RSC

Lanthanum, La, (Greek lanthanein 'lie hidden'), phosphorescent in energy-saving light bulbs

Lanthanum with Cerium, Ce, in mischmetal: negative electrode NiH battery, cigarette lighter ignition element

Lanthanum chloride | Lanthanum nitrate | Lanthanum oxide | Lanthanum perchlorate

2.11.0 Rare earth elements, Lanthanides

Latex¶

5.3.5 Condom

23.6.1 Natural rubber, rubber

3.6.11, Vulcanization

23.6.1 Natural rubber, rubber¶

Natural rubber,from latex, C₅H₈)n, [n = 4, 0005, 000], polyterpenes in milky latex sap from Brazilian rubber tree (Hevea brasiliensis), Euphorbiaceae, and India rubber tree (Ficus elastica) , Moraceae. source

Polyisoprene, elastomer, diene polymer, natural rubber is mainly cis-1,4-polyisprene, from Hevea brasiliensis, main monomer isoprene, -CH₂=C(CH3)CH=CH₂^-, 2-methyl-1,3-butadiene, also made synthetically, cis polyisoprene, isoprene rubber source

Gutta-percha is mainly trans-1,4-polyisprene

1. Natural polymers occur as brittle glassy gums and resins in plants, e.g. conifers, and as polysaccharides, e.g. starch.

Natural rubber, para rubber, hevea rubber obtained from the milky latex sap of Hevea braziliensis, Euphorbiaceae, contains polyterpenes with linked isoprene units CH₂=C(CH3)CH=CH₂, [cis-1,4-polyisoprene], in which all the -CH=CH-= groups are cis. source

2. The polymer chains in natural rubber are elastic in the sense that the chains can be unravelled without coming apart, i.e. the rubber can stretch.

Elasticity was improved by cross-linking with sulfur, using the Goodyear process to produce vulcanized rubber.

Stretching aligns the random chains, and temporarily crystallizes and toughens rubber, so that rubber tyres do not form cracks.

Natural rubber is not very elastic in the Hooke's law sense of stress being proportional to strain.

The transisoprene polymer, trans-1,4-polyisoprene, occurs in the latex of Palaquium oblongifolium, Sapotaceae family, the same chemical as natural rubber, polyisoprene, but with trans, not cis, bonding.

3. Test for strength of cross-linkages, add toluene then measure the increase in volume

Rubber bands are made mostly of natural rubber cured by heat.

Petrol can dissolve the cross-linkages between the polyisoprene molecules to allow water molecules to move in between them and swell the rubber band.

4. Hard rubber was made by Charles Goodyear and shown at the 1851 exhibition at Crystal Palace, London.

During the vulcanization process, 30-40% sulfur is added to the natural rubber to form a compound with high dielectric power, high resistance to chemical products, hardness and rigidity up to 50C, and a bright shiny appearance.

It is processed with extruders then worked on machines or compression moulds to make battery separators, telephone receivers, tyres.

23.6.2 Negative thermal expansion (NTE) of rubber, entropy¶

Negative thermal expansion (NTE) materials contract on heating within certain temperature ranges.

They are not called "thermal contraction" materials.

A rubber band contracts on heating, because when long polymer chains in rubber absorb energy, adopt a more contorted configuration, reducing the volume.

A cooled rubber band, becomes stretchier and expands slightly, because the molecules become more organized into a more efficient stretching shape.

A common explanation of this phenomenon is that the arrangement of long polymer chains in rubber is like a ball of mixed up threads of string.

By grabbing hold of each end of the tangle and pulling it in opposite directions, the threads of string become more horizontal as the ball of string is elongated.

So the arrangement of threads becomes more ordered and the entropy of the system becomes lower.

Reduced entropy, more orderly alignment of molecules, causes the rubber band to lose heat.

A stretched rubber band feels hotter as it expands with heat lost in an exothermic process.

A contracting rubber band feels cooler with heat gained in an endothermic process.

The particles making up rubber in its natural state are more disordered than when the rubber is stretched and is under tension.

When tension is removed the rubber contracts back with the particles returning to their initial disordered state.

Entropy is a measure of the amount of disorder in a system, so the entropy of a rubber band increases when it changes from a stretched state to a natural state.

The change of entropy of a system in a reversible process = the amount of heat absorbed or emitted / absolute temperature of the system.

23.6.3 Heat and cool rubber bands, rubber band heat engine¶

See diagram 23.6.4: Test heated rubber bands

1. To demonstrate the effect of heating rubber bands, stretch a rubber band around a wooden box.

Cut out an arrow shape from a piece of cardboard.

Mount the arrow on a pin and then push the pin under the middle of the elastic band.

If the elastic band is heated at the left of the pin, it contracts, pulling the pin towards it and the point of the arrow moves to the right.

2. Rubber band heat engine is a bicycle wheel with rubber bands instead of spokes.

Set up the bicycle wheel vertically.

Rubber contracts on heating so a lamp or a hair dryer placed on one side of the wheel shift the centre of gravity, resulting in rotation.

Cooler rubber spokes move into the irradiated region to repeat the process.

To achieve a smoother rotation the wheel is balanced using small pieces of Plasticine placed around the rim.

3. To make more space in a freezer, you might collect scattered items, e.g. ice lollies, and put an elastic band around them.

However, after some time the originally stretched elastic band become loose and slacker, than when first applied to the ice lollies at room temperature.

4. To observe the thermal properties of rubber, hang a 1 kg mass from four rubber bands, so it touches the table.

Heat with a radiant heater for 20 seconds and the mass will lift.

Enclose a rubber tube in a copper cylinder and heat with a Bunsen burner.

The rubber tubing contracts as it is heated.

Stretch and unstretch rubber bands on the lips to feel the changes in temperature.

23.6.4 Stretch rubber bands¶

Hooke's law does not apply to polymers or rubber.

1. Stretch a thick rubber bandit (> 0.5 cm wide) quickly against the forehead, lips, or wrist and note the increase in temperature.

Hold it stretched, allow it to cool back to room temperature.

Then let it suddenly contract against the lips to its original length and note the temperature drop.

2. Use a hair dryer to heat a stretched rubber band, e.g. 1 cm wide, with a weight on the end, e.g. 2 kg.

3. Stretch a wide rubber band between the index finger of your two hands.

Let the rubber band touch the lips.

Stretch the rubber band (not so far that it breaks!) then slowly release the tension.

Feel heat in your lips when the rubber band stretches, because of friction between the rubber molecules.

The stretched rubber band feels cooler when the tension is released.

4. Hold each end of the rubber band with the fingers of your hands, press your lips firmly to the middle of the rubber band, and maintain contact as you quickly stretch the rubber band in opposite directions outward.

Your lips you will feel a sudden heat from the rubber band.

5. Suspend a 100 g weight from a rubber band attached to a clamp stand.

Adjust the height of the 100 g weight until it just touches the table.

Use a vertical ruler to measure the length of the suspended rubber band.

Bring a heat source, e.g. a lighted match or hair dryer close to the middle of the stretched rubber band.

Note that the heated rubber band contracts.

Laudanum¶

Laudanum, opium, diluted in wine with cloves and other spices, former common medicine, e.g."poppy-head tea" given to noisy babies

Laudanum is an opium tincture made from poppy seeds and contains almost all the 20 opium alkaloids, including morphine and codeine. It slows transmission of signals within the central nervous system, and slows respiratory rate and heart function. Laudanum may be used to treat severe diarrhoea, neonatal abstinence syndrome (NAS), i.e. ddiction to opiates babys whose mothers used opiates during pregnancy.

Lauric acid¶

Lauric acid, C₁₂H₂₄O₂, CH₃(CH₂)₁₀COOH, dodecanoic acid, medium chain, saturated fatty acid source

It occurs in milk (human, cow, goat), laurel oil, palm oil, coconut oil.

It has high MP 43.2 oC, increases high density lipoprotein (HDL), the "good" cholesterol

Fatty acids in oils of natural products: 5.1.3 (Table)

Fats in food: 3.90

Lavandulol¶

Lavandulol, C₁₀H₁₈O, is a monoterpenoid primary alcohol. source

It occurs in lavender oil, in the essential oil of Poljakov, (Tanacetum gracile), and in Achillea.

It is used as a fragrance in pheromone perfumes, which are perfumes infused with lab-created ingredients meant to mimic the chemical signals our bodies naturally emit to make a person smell enticing to other persons.

Lawrencium¶

Lawrencium, Lr, atomic number 103, radioactive actinide atom, d-block element atom. discovered in 1961, twelve isotopes with mass numbers 252 to 266.

Lead, Pb¶

Lead, Pb

Lead Table of Elements

Lead, RSC

Lead, element, Lead foil, Lead shot, Lead Plate Electrodes 100 x 50 x 1.5 mm, 100 x 50 x 3 mm, 75 x 25 x 1.5 mm, Lead cube, 10 mm, 20 mm

Lead, Pb (plumbum) (Old English leād), metal foil 0.3 mm, powder, filings, strip, sheet, grain, lead AAS std, lead cell test kit, (0.5-5 mg / L),

lead shot, fishing sinkers, roof guttering, Harmful, chronic poison if long-term exposure from pipe work, pottery glazes, containers, dusts.

Lead poisoning kills many people every year from long-term effects such as kidney failure, high blood pressure, heart disease, stroke and brain damage.

Lead type (lead, tin, antimony alloy), invented by Johannes Gutenberg (1395-1468, Germany), first printed Bible using moveable lead type, lead shot,

fishing sinkers, roof guttering, foil, powder, filings, strip, is a soft, dense, and unreactive metal, available as lead foil, powder and lead shot

It is extracted from the ore galena (PbS), used in fishing sinkers, solder, lead glazes and X-ray protective shields

It holds the pieces of glass together in stained glass windows, used in bullets, lead shot, building construction, lead cell accumulators, pewter, bearings and alloys.

Formerly, ladies used lead carbonate to whiten their laces and some may have died from such use.

Lead reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide. source

SO₂ or nitrogen dioxide, NO₂. source

Lead has no reaction with dilute HCl or H2SO4or with water.

Heated lead powder forms lead oxide.

Inorganic Pb2+is an accumulated poison and can replace calcium in bone.

A "lead pencil" contains graphite, not lead.

Lead is a metal with a silvery appearance that is resistant to attack by acids, because of the formation of a protective oxidized layer on its surface.

The metal melts at low temperature and is a good conductor of electricity, so it is used in solders.

The vapours of molten lead are extremely toxic and the effect of inhaling them is cumulative.

Lead salts are toxic by inhalation and can be absorbed through the skin, so should be handled with great care.

Wash laboratory areas where lead salts have been used with a dilute detergent solution to prevent exposure to any residual dust containing lead.

Do not heat lead oxide on a charcoal block.

Lead is used in the production of batteries, ammunition, metal products (solder and pipes), and devices to shield X-rays.

Lead was present in petroleum, paints and ceramic products, caulking and pipe solder.

Hhowever, because of health concerns, it is now prohibited to include lead in these products.

Water pipes in some older buildings may contain lead solder.

Atomic number: 82, Relative atomic mass: 207.2, RD 11.3 g cm-3 MP = 327 oC, BP = 1744 oC.

Specific heat capacity: 130 J kg-1 K-1.

Leadbr> Lead, Pb: 35.2.42, (Geology)

"Lead pencils": 35.3.5, (Geology)

Aquadag: 35.3.6, (Geology)

Graphite: 35.3.4 (See: 4.), (Geology)

3.61.9 Lead paint

3.61.8 Lead tetra-ethyl, tetraethyl lead

Lead ore, galena: 35.2.33, (Geology)

Lead residues: 3.3.3 (Disposal)

Prepare lead-acid battery electrolyte: 32.5.3.6

Prepare lead-tin alloys in a casting mould: 3.61.1

Prepare lead dioxide and lead (II) nitrate: 3.61.2

Reactions of lead (II) salts, Pb2+: 3.61.3

Reactions of lead (IV) salts, Pb4+: 3.61.4

Separate sand and lead powder by panning: 10.8.1

Lead tests

Tests for hardness of lead, tin, and lead-tin alloys: 3.61.5

Tests for lead: 12.11.3.21

Tests for lead ions: 3.61.6

Tests for melting point of lead, tin, and lead-tin alloys: 3.61.7

Lead compounds Lead compounds are cumulative poisons¶

All lead salts are highly toxic if ingested or particles inhaled.

Wash hands after handling.

Use < 10 mL or g of lead compounds per activity.

Bright orange pottery glazes usually contain lead salts.

The pigments white 1, white 2, white 16, mixed white, chrome yellow, chrome green, and chrome orange are highly toxic cumulative poisons.

Chrome red, PbO.PbCrO₄, basic lead chromate source

Chrome yellow, PbCrO₄, lead chromate pigment source

Crocoite, PbCrO₄, Red lead ore source

Lead paint detection kit to detect lead in paint

Lead (II) acetate, Lead (II) ethanoate, lead acetate

Lead (II) bromide, PbBr₂, lead bromide, highly toxic by all routes source

Lead antimonate

Lead azide, Pb(N₃)₂, is a contact explosive, in detonators source

Lead (II) iodide, PbI₂, lead iodide, lead diiodide, highly toxic, is a cumulative poison source

Lead (II) iodide, Solution < 1%, Not hazardous

Lead (IV) acetate, lead (IV) ethanoate, Pb(CH₃COO)₄, lead tetraacetate source

Lead (IV) oxide

Lead (IV) tetraethyl, Pb(C₂H₅)₄: 3.61.8 Lead tetraethyl source

Lead antimonate, Naples yellow for craft, antimonate of lead

Lead manganese oxide, coronadite, Pb₂Mn₈O₁₆: 35.2.26, (Geology) source

Lead residues: 3.3.3 (Laboratory disposal)

Pyromorphite: 35.2.56, Pb₅(PO₄)₃Cl (lead phosphate), (Geology) source

Lead acetate¶

Lead (II) acetate, Pb(CH₃COO)₂, lead (II) ethanoate source

Lead (II) acetate, Toxic by all routes, cumulative poison

Lead (II) ethanoate, Solution < 0.5%, Not hazardous

Lead (II) acetate, m.p. 75 oC, white to colourless, monoclinic crystals or granules, slowly efflorescent, absorbs CO₂ from air and becomes insoluble source

Lead (II) acetate dissociation: Pb(CH₃COO)₂ (aq) < → Pb2+ + 3CH₃COO^- source

Lead (II) acetate, "sugar of lead" (HARM 1616)

Lead (II) acetate trihydrate crystals, (Pb(CH₃COO)₂.3H₂O source

Lead (II) acetate trihydrate, C₄H₆O₄Pb.3H₂O source

Lead (II) acetate, For 0.1 M solution, 38 g in 1 L water + dilute ethanoic acid to clear

Lead (II) acetate test paper for H₂S (for testing anions) source

Lead (II) acetate basic, anhydrous, Pb(CH₃COO)₂, 72% for sugar analysis source

Lead antimonate¶

Lead antimonate, Pb₃Sb₄O₃, Pb(SbO3).Pb₃(SbO₄)₂, "Naples yellow", antimony yellow, ancient mineral pigment, for craft, antimonate of lead, toxic source

Lead (II) bromide¶

Lead (II) bromide, PbBr₂, Solution < 1% Not hazardous source

Electrolysis of lead (II) bromide melt: 5.6.1

Lead (II) carbonate¶

Lead (II) carbonate, PbCO₃ source

Lead (II) carbonate, PbCO₃, cerussite, basic lead carbonate, (PbCO₃ + Pb(OH)₂, white lead source

Lead (II) carbonate, PbCO₃, lead carbonate, lead carbonate basic, white lead flux, paint pigment, Toxic source

Lead (II) carbonate, cerussite, ceruse: 35.2.20, (Geology)

Lead (II) carbonate Solution / mixture < 1%, Not hazardous

Lead (II) carbonate hydroxide, PbCO₃.Pb(OH)₂, white lead, basic lead carbonate, flux, paint pigment, Low cost: pottery supplies source

Lead (II) chloride¶

Lead (II) chloride, PbCl₂, lead chloride, highly toxic by all routes source

Lead (II) chloride, Solution < 1%, Not hazardous

Lead (II) chromate¶

Lead (II) chromate, PbCrO₄, lead chromate, very insoluble in water, highly toxic by all routes, highly corrosive, strong oxidizing agent source

Lead chromate, orange-yellow powder, crystalline, SG 6.3, insoluble in water, acetic acid, and ammonia, but soluble in acid and alkalis.

It is possibly the most insoluble salt in water.

If heated to decomposition emits toxic chromium fumes which affect the lungs, possibly lung cancer.

Lead chromate pigment, (Naples yellow), is a highly toxic cumulative poison.

Lead (II) chromate, Solution < 1%, Not hazardous

Chrome red, PbO.PbCrO₄, basic lead chromate pigment source

Chrome yellow, PbCrO₄, lead chromate pigment source

Use in printing inks, paints, to colour vinyl and rubber.

Lead (II) nitrate¶

Lead (II) nitrate, Pb(NO₃)₂, white to colourless large crystals, reactivity series, lead (II) nitrate, Toxic, cumulative poison source

Lead (II) nitrate, Solution < 1%, Not hazardous

Lead (II) nitrate, Pb(NO₃)₂, lead dinitrate, lead nitrate, white to colourless, translucent cubic or monoclinic crystals, decomposes at 470 oC. source

It is the only common soluble lead compound, forms explosive mixture with combustible materials, e.g. S, P, metal powders

The heated solid forms highly toxic nitrogen dioxide, test for anions: forms bright yellow precipitate of lead iodide, with sodium or potassium iodide

Lead (II) nitrate, For 0.1 M solution, 33 g in 1 L water

Coloured precipitates: 12.2.4.02, (See: 1. and 3.)

Tests for hydrogen sulfide solution: 13.3.26 (See: 2. Lead (II) nitrate test

Zinc displaces lead from lead (II) nitrate solution: 12.14.16

Lead (II) sulfate¶

Lead (II) sulfate, PbSO₄, lead sulfate, green vitriol, blue lead, white lead, Toxic, cumulative poison source

Lead (II) sulfate was previously in white lead paint.

Lead (II) sulfate, Solution < 1%, Not hazardous

Prepare lead acid battery electrolyte: 32.5.3.6

Anglesite: 35.2.6, (Geology)

Lead (II) sulfide¶

Lead (II) sulfide, PbS, lead sulfide, lead glance, blue lead, Toxic, cumulative poison

Galena: 35.2.33, (Geology)

Lead (II) sulfide, Solid mixture < 1%, Not hazardous

Lead (II) oxide¶

Lead (II) oxide, PbO, lead oxide, lead monoxide, plumbous oxide, amphoteric, litharge, massicot, Toxic

Lead (II) oxide mono, yellow lead oxide, litharge, massicot, flux, lead monoxide, lead protoxide, yellow amorphous powder, fused and crystalline form called litharge, used as pigment in glass and enamels

Lead monoxide pigment (yellow 46), is a highly toxic cumulative poison

Solution < 1%, Not hazardous

Lithage, PbO, lead (II) oxide, lead monoxide, lead oxide, massicot (amphoteric)

Battery capacity: 32.5.3.7

Lead (II/IV) oxide¶

Lead (II/IV) oxide, Pb₃O₄, triplumbic tetroxide, red oxide of lead, lead tetroxide, red lead, minium, Toxic by all routes, cumulative poison source

Lead (II/IV) oxide, red lead oxide, Pb₃O₄, 2PbO.PbO₂, dilead (II) lead (IV) oxide (red lead, anticorrosive paint pigment) source

Lead (II/IV) oxide, Solid mixture < 1%, Not hazardous, trilead tetroxide, red, lead, triplumbic tetroxide, lead tetroxide

Toxic by all routes, cumulative poison

Two valence states: Pb2+ and Pb4+ (Pb4+)(Pb2+)2O4)

It reacts violently with Al and Mg powders and some organic materials.

Do NOT heat lead (II, IV) oxide on a charcoal block.

Old paints may contain > 30% lead, but nowadays may contain only < 1% lead, bright red or orange, pigment.

Lead (II/IV) oxide forms insoluble iron (II) plumbate and iron (III) plumbate with iron and iron oxides.

It is used in anti-corrosive lead paints, especially rustproof primer paints.

Lead tetroxide is soluble in dilute hydrochloric acid, so it can dissolve in the hydrochloric acid in the stomach and act as a lead poison.

Lead (II/IV) oxide is NOT soluble in water, so it can be used in lead glass.

It is used to make lead cell accumulators (car batteries, lead-acid batteries), and flux.

Minium stone is used for craft and smelting.

Lead (II/IV) oxide, Reduce red lead to lead and oxygen: 10.10.1

Lead (IV) oxide¶

Lead (IV) oxide, PbO₂, lead dioxide, lead peroxide, highly toxic by all routes, cumulative poison source

Lead (IV) oxide, Solid mixture < 1%, Not hazardous

Lead (IV) oxide, PbO₂, lead dioxide, car battery plates, lead-acid accumulator (+ve accumulator electrode) source

Lead (IV) oxide, lead tetroxide pigment (red 105), is a highly toxic cumulative poison

Lamotrigine¶

Lamotrigine, C₉H₇Cl₂N₅, a dichlorobenzene, a non-narcotic analgesic, an antidepressant and anticonvulsant drug. source

Its physiology effect is to decrease central nervous system disorganized electrical activity, and is available in Australia on prescription.

It is widely used in the treatment of both epilepsy and as a mood stabilizer in bipolar disorder, and it has relatively few side-effects, but may cause serious rashes in children.

Lemons¶

(Italian limone 'lemon')

Lemons, lemon juice, 5-8% citric acid

Lemon, (Citrus x limon), (lemon citrus fruit), Rutaceae

Acid-base indicators in the home: 19.1.1, (lemonade)

Citric acid, C₆H₈O₇ source

Lemon cell, (electricity from lemons)

Lemon juice: 3.2.6, invisible ink

Isolation of benzoic acid in lemonade: 9.1.9

Prepare citric acid crystals with lemon juice: 12.6.1

Prepare mayonnaise and salad dressing emulsions: 7.5.7

Soft drinks, carbonated beverages, fizzy drinks, sports drinks

Tests for lemon juice effect on apple browning: 19.2.3.4 (Cooking)

Tests for pH of water in the laboratory: 18.1.2 (lemonade)

Lemon juice

Lemon juice is rich in vitamin C (100g of lemon juice contains 38 mg of vitamin C), pH 2-3, because of citric acid content.

It can break down the amines in fish into non-volatile ammonium salts to neutralize the fishy odour.

It can hydrolyse the tough collagen fibres in meat to tenderize it.

Lemon juice does not dissolve fat.

Use lemon juice to treat dandruff, blackheads, facial blemishes, rough hands, sore feet, constipation, itches, minor wounds.

Use with honey and olive oil relieve coughing, unclog ketchup bottles, write with invisible ink, blonde hair, deodorize cooked fish, fish cooking utensils.

Use it on microwave ovens and refrigerators, remove fruit stains, rust, mineral discoloration, ink spots from clothing, whiten fingernails.

Use it with salt to clean brass and stainless steel sink.

Use lemon juice to prepare bathtub rust stains cleaner.

Lemon oil

Lemon oil is oil from lemon peel, D-limonene, a terpene, used for furniture polish, inhibits spiders and insects, stain remover.

Limonene¶

Limonene, C₁₀H₁₆, is an aliphatic hydrocarbon, cyclic monoterpene, colorless liquid, fragrance, flammable. source

It is a major flavour component in many species, including the essential oils of citrus fruit peels.

It occurs in pine trees, resins, and many other species, including, Eucalyptus, yarrow, celery, lipstick tree, caraway.

Also, limonene monoterpenoids, e.g. Perilla alcohol, C₁₀H₁₆O. source

Lepidine¶

Lepidine, C₂₀H₁₈N₄O₂, lepidine B is an aromatic ether, which can be isolated from seeds of the garden cress, (Lepidium sativum). The garden cress is used in the sandwich filling called 'mustard and cress': white mustard (Sinapis alba), (Brassica alba) + cress (Lepidium sativum). source

Leucine¶

Leucine, (Table of amino acids)

Leucine, DNA codons

Leucine, (See: a3)

Linoleic acid¶

Linoleic acid, C₁₈H₃₂O₂, CH₃(CH₂)₄CH=CHCH₂CH=CH(CH₂)₇COOH, polyunsaturated omega-6 fatty acid, has cis and trans forms. source

In the cis configuration, the four hydrogen atoms adjacent to the double bonds occur on the same side of the carbon axis.

In the trans configuration, the four hydrogen atoms adjacent to the double bonds occur on alternate sides of the main carbon axis, 2 on one side and 2 on the other.

The more stable trans configuration may be produced from the cis configuration during hydrogenation of polyunsaturated vegetable oils to improve their texture.

Trans fatty acids tend to raise the level of low density lipoproteins (bad LDLs) and lower the level of high density lipoproteins, (good HDLs)

These actions may result in changes in cholesterol levels that may increase the risk of the heart disease atherosclerosis.

Mono-unsaturated, unhydrogenated oils, e.g. olive oil, are preferable to the trans fatty acids in French fries, chips, and doughnuts.

The first double bond is on carbon #6, counting from left to right so this is an omega-6 fatty acid, typical of the unsaturated fatty acids in plant oils and seeds.

However, fish oils contain omega-3 fatty acids, i.e. the first double bond in on carbon #3.

See diagram 19.2.1chd: cis and trans, linoleic acid

19.2.1.7.2 Trans fats, Omega-fatty acids

Linolenic acid¶

Linolenic acid, C₁₈H₃₀O₂, α-linolenic acid, Alpha linolenic acid, (ALA), polyunsaturated fatty acid (PUFA), essential fatty acid in diet because not synthesized by mammals. source

It occurs in omega-3 fatty acids group, in plant oils, e.g. canola, soybean, linseed, olive.

English walnut, may inhibit synthesis of prostaglandin, so reducing inflammation and some chronic health problems.

Linolenic acid, polyunsaturated omega-3 fatty acid

Two isomers in common vegetable oils:

1. Alpha-linolenic acid (ALA), C₁₈H₃₀O₂, is a polyunsaturated omega-3-fatty acid, essential fatty acid not produced in the human body. source

High concentration occurs in lants, nuts, vegetable oils, including:

| Chia, (Salvia hispanica) | Kiwi fruit, (Actinidia deliciosa)

| Perilla, (Perilla frutescens)

| Flaxseed, (Linum usitatissimum)

2. Gamma-linolenic acid (GLA), C₁₈H₃₀O₂, a polyunsaturated omega-6-fatty acid. source

High concentration in and seed oils of blackcurrent and borage and Evening primrose

Lignin¶

Lignin, (C₁₈H₁₃N₃Na₂O₈S₂), is an organic polymer in wood fibres and grass cell walls of vascular plants. source

It is composed of coniferyl, p-coumaryl, and sinapyl alcohols in varying ratios.

Lignin, cellulose, hemicellulose, are copolymers of phenyl propane units with side chains.

Copper is involved in the formation of lignin for strong shoots and stems.

Filter paper contains lignin, but cigarette paper does not contain lignin.

Lignans, polyphenols from degradation of lignin, e.g. Sesamin

Cellulose digestion: 9.1.10

Lignotuber, Banksia, Eucalyptus

Microbial decomposition of cigarette paper: 4.2.8

Tests for lignin: 9.3.12

Tests for lignin, Microscope staining techniques: 9.1.10 (See: 3.)

Tests for wood: 9.3.22

Xylem: 9.1.5

Lighted splint tests¶

Lighters, matches, tapers, (Commercial)

Burn wood splints in chlorine: 12.4.8.6

Dinitrogen oxide (nitrous oxide): 13.3.22

Prepare hydrogen gas bubbles: 13.3.15, (See: 8.)

Prepare sunbeam mists: 7.8.15, methylene chloride mist

Tests for acetylene: 16.4.2

Tests for carbon dioxide with lighted splints: 3.5.4

Tests for dinitrogen oxide, nitrous oxide, N₂O: 13.3.23 source

Tests for hydrogen chloride: 13.3.24

Tests for dinitrogen oxide, nitrous oxide: 13.3.23

Tests for oxygen: 3.49.1

Lime¶

Lime, CaO, Ca(OH)₂, CaCO₃, ambiguous name, usually CaO, lump, lime, quicklime, powder, Toxic if ingested or by skin contact source

"Lime" may be also Ca(OH)₂ or CaCO₃. source

Lime tree

Chalk: 35.4.0, (Geology)

Chalk (lime) content of the soil: 6.9.02, (Agriculture)

Heat calcium metal to form calcium oxide: 8.2.14

Lime sulfur, CaSx: 4.3.1 (Agriculture)

Limestone: 35.4.12. (Geology)

Marble: 35.3.9, (Geology)

Prepare quicklime, CaO: 34.2.7

Prepare slaked lime, Ca(OH)₂: 34.2.8 source

Prepare soda lime: 34.2.12

Tests for limestone: 35.6.14 (Geology)

Lime sulfur, CaSx, (Agriculture)

Lime tree

The term "lime" may refer to Citrus species or other species, e.g. Tilia genus are called linden tree or li me tree in

Europe and Asia and American basswood and American linden in North America, family Malvaceae.

Citrus limes have high concentration of citric acid and are the most acid of the citrus fruits, Rutaceae.

Australian finger lime (Citrus australasica), Rutaceae

Australian blood lime (Citrus australasica var. sanguinea x 'Ellendale Mandarin' hybrid)

Desert lime, (Citrus glauca)

Mango lime, (Citrus ichangensis)

Kaffir lime, (Citrus hystrix)

Kakadu lime, (Citrus gracilis), Humpty Doo Lime

Key lime, (Citrus x aurantifolia), (hybrid: C. hystrix × C. medica)

Limewater¶

Limewater, saturated calcium hydroxide solution

Calcium hydroxide, Ca(OH)₂, limewater, 10 g in 1 L water, shake, allow it to settle, decant clear liquid. source

Weaker bases, e.g. calcium hydroxide (limewater, slaked lime), can cause burns if they are left in contact with the skin.

If poison ingested = Ammonium oxalate, Buffer solution tablets pH 2, Oxalic acid, Potassium hydrogen oxalate, Sodium oxalate, give milk or water, weak limewater, chalk solution

Experiments

Calcium hydroxide with cobalt chloride 12.2.4.1, (See: Below 12.2.4.1, limewater experiments)

Candle flame forms carbon dioxide: 8.1.13

Carbon dioxide is a product of combustion: 8.2.1

Effervescent tablets, health salts, sodium bicarbonate, (baking soda): 11.1.5 See: 1.

Elements in food: 19.4.33.0, See: 2.

Heat different carbonates, carbonates of Cu, Mg, Na, Pb and Zn: 12.16.3

Hydrogen peroxide with potassium sodium tartrate, cobalt (II) chloride catalyst: 17.7.6.3

Precipitation: 10.11.01

Prepare ethyl acetate, (ethyl ethanoate): 16.4.2

Prepare hard water: 12.2.4

Prepare limewater: 5.4.5

Reactions of metals with water, Cu, Zn, Fe, Mg, Al: 12.15.1

Respiration, limewater tests for carbon dioxide: 9.155

Respiration is a form of combustion: 8.2.4

Tea with limewater: 12.2.11

Tests for acetates: 12.11.5.1

Tests for carbon dioxide in the breath with limewater : 9.6.10

Tests for carbon dioxide through calcium hydroxide solution, limewater: 12.16.1.1

Tests for gases from burning hydrocarbons: 16.4.6.0

Tests for lactic acid solution: 12.7.11

Tests for respiration of soaked peas with limewater, respiration apparatus: 9.155

Tests for soap: 12.5.12

Linalool¶

Linalool, C₁₀H₁₈O, (CH3)2C=CH(CH2)2C(CH3)(OH)CH=CH₂, is a monoterpenoid, a tertiary alcohol. source

It is used as a volatile oil component, an antimicrobial agent, and a fragrance.

It occurs in basil (Ocimum basilicum), coriander (Coriandrum sativum), Indian hemp (Cannabis sativa), linaloe tree (Bursera linaloe), mugwort (Artemisia vulgaris), yarrow, (Achillea millefolium).

Linseed oil¶

Linseed oil, from seeds of flax Linum usitatissimum, contains glycerides of oleic acid and other unsaturated acids.

Linseed oil, conditions and seals bare wood in putty, paints, varnishes for cricket bats, linoleum, outdoor furniture.

Use linseed oil to stop splitting in chopping boards, wooden bowls, and cricket bats.

Use linseed oil, boiled with ground resin, to make sticky flypaper paste.

Linustatin

Linustatin, C₁₆H₂₇NO₁₁, cyanogenic glycoside, diglucoside of acetone cyanohydrin, methylpropanenitrile, toxic. source

It occurs in flaxseed meal, and in Passiflora

Lipoproteins

A lipoprotein is a combination of a triglyceride around a cholesterol, surrounded by a phospholipid.

Lipoproteins are divided onto these classes: | HDL, high-density lipoprotein (the good cholesterol) | LDL, low-density lipoprotein (bad cholesterol) | IDL, intermediate-density lipoprotein | VLDL, very low density lipoprotein, and | Chylomicrons |. Chylomicrons are very small particles of proteins and fats, which transport the insoluble fats away from the small intestine, then into the bloodstream.

Lithium, Li¶

Lithium, Li

Lithium Li, Table of the Elements

Lithium, RSC

Lithium, Li, (Greek lithos stone), lithium metal, lithium ribbon, lithium in paraffin liquid

Lithium is a least dense, soft and shiny surface metal.

When cut by knife it tarnishes, and it is a very reactive alkali metal with acids.

It is stored under oil, because it reacts with air and water, but least reactive element in group I, red flame test colour.

It is a rare element, found in some granite pegmatite, and used in Al and Mg alloys, batteries and anti-depressant medicines.

Lithium reacts with oxygen gas and water, and, on heating, it reacts with nitrogen and hydrogen gas.

Lithium carbonate is used for a craft flux.

Atomic number: 3, Relative atomic mass: 6.941, RD 0.53 g cm-3 MP = 180 oC, BP = 1330 oC.

Specific heat capacity: 3.39 × 103 J kg-1 K-1.

Lithium compounds

Prepare lithium oxide: 12.9.1

Lithium-ion battery: 33.1.8.4, Li-ion battery

Reactions of lithium with water: 12.9.2

Lithium compounds: (very toxic)

Lithium aluminium hydride, LiAlH, lithium tetrahydroaluminate, Toxic by all routes, Not permitted in schools

Lithium aluminium silicate, LiAlSi₂O₆, spodumene, forms 6 m crystals, grey-white ash when ignited source

Lithium carbonate, Li₂CO₃ for craft, flux, glaze, tranquillizer for mental disorders, white solid, Toxic, Irritant source

Lithium carbonate, Low cost: from pottery supplies stores

Lithium hydride, Toxic by all routes, fine particles mixed with air is explosive, reacts violently with water to form dangerous hydrogen

12.9.1Prepare lithium oxide¶

12.9.1Prepare lithium oxide

Heat pieces of lithium metal shot on a metal spoon (deflagrating spoon).

Note the violet glow when it starts to burn, then put the burning lithium in oxygen gas.

4Li + O₂ → 2LiO₂ source

Lithium oxide is used in some ceramic glazes as a flux and colorant.

Lotoaustralin¶

Lotaustralin, C₁₁H₁₉NO₆, is a cyanogenic glycoside. source

It occurs in passionfruit (Passiflora edulis) and white clover, (Trifolium repens), cassava, (Rhodiola sachalinensis), and (Phaseolus lunatus).

Epilotaustralin, C₁₁H₁₉NO₆, is found in Rhodiola, and Einkorn (Triticum monococcum), an ancient diploid wheat, and in other cereals. source

Low-cost, chemicals, equipment

Low-cost chemicals, and common substances

Low-cost equipment, simple equipment: 1.12.0

Consumables low cost equipment

Luminescence

Luminescence is the property of substances that can emit light without any heat being applied and they include fluorescent and phosphorescent substances

Luminescence means emitting light from an object without its being heated and may refer to the glow from that object.

Luminescence is emission of light for any reason other than a rise in temperature, e.g. excited photons returning to a ground state.

However, thermoluminescence and candoluminescence refers to a substance emitting light when heated.

28.101 Candoluminescence

Chemiluminescence Chemiluminescence

Fluorescence

Fluorophores

28.104 Luminance and illuminance

Phosphorescence

Triboluminescence

Thermoluminescence

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