Topic 19b Chemicals in the home, home chemistry
Updated 2008-08-19 R
Please send comments to: J.Elfick@uq.edu.au
Table of contents
19.4.1 Checklist of chemicals in the home, household chemicals
19.5.0 Fabrics in the home
19.6.0 Hardware, laundry, painting, cleaning, preserving
19.7.0 Beauty and skin care products
19.8.0 Common measures
19.4.1 Checklist of chemicals in the home, household chemicals
19.4.2 Kitchen hints
19.4.2.1 Stain removal
19.5.0 Fabrics in the home
19.5.1 Natural and synthetic fabrics
19.5.1.1 Permanent crease solution, hair straightening, permanent wave
19.5.2 Dyes
19.5.3 Dyes with a mordant
19.5.4 Natural dyes
19.5.5 Washing clothes, washing soda
19.6.0 Hardware, laundry, painting, cleaning, preserving
19.6.1 Paints, fire-retardant, anti-fouling, fluorescent, phosphorescent
19.6.2 Bases in the kitchen and laundry, washing powders, di-sodium tetraborate (III)-10-water (borax)
19.6.3 Metals in the kitchen, aluminium, iron, zinc, chromium
19.6.4 Bath cleaning, borax
19.6.5 Prepare preserving agents for cut flowers
19.6.6 Prepare household soap
19.6.7 Prepare camphor oil
19.7.0 Beauty and skin care products
19.7.1 Perfumes and smells
19.7.2 Lipstick
19.7.3 Hair products
19.7.4 Sunscreens and sun-protective clothing
9.226 Teeth and toothpaste
19.8.0 Common measures
3.5.1 Spoon volume
3.5.2 British liquid measures, imperial measures (fl. oz. = imperial fluid ounce)
3.5.3 American liquid measures, US measures
3.5.4 Miscellaneous measures
3.14.0 Oven temperatures
19.4.1 Checklist of chemicals in the home, household chemicals
Abrasives Silicon carbide
Acetic acid, vinegar, dissolves grease, mild disinfectant, cleaning toilets
Albumen, Albumin, egg white
Alcohol, ethanol, ethyl alcohol
Acetone, nail polish remover (not in recent formulations)
Adhesives
Algaecides, in swimming pools
Alum
Aluminium foil
Ammonia, cloudy ammonia
Ammonium carbonate, smelling salts
Ammonium chloride, soldering flux
Ammonium nitrate, garden fertilizer
Ammonium sulfate, garden fertilizer
Anti-freeze
Aspirin
Baking powder
Baking soda
Bakelite
Bean curd
Bitumen, asphalt (pitch, "tar" on roads)
Bleach, domestic bleach, sodium hypochlorite
Borax
Boric acid, boracic acid eye medicine
Calcium carbonate, egg shell, marble, geological chalk
Calcium hydroxide, whitewash
Calcium hypochlorite, bleaching powder
Calcium oxide, garden lime, soil conditioner and fertilizer
Calcium sulfate, school chalk, blackboard chalk
Candle paraffin wax, polish
Carbon charcoal, graphite is the "lead" in a lead pencil
Carbon dioxide, soda water, aerated waters, cleans carpet stains
Carbon tetrachloride, dry cleaning fluid
Cement, calcium + aluminium silicates, Portland cement
Chlorine bleach
Chlorine gas, swimming pool chlorine
Chromium
Citric acid, lemon juice
Clay
Copper
Copper (II) sulfate, Bordeaux mixture garden fungicide is copper (II) sulfate and calcium hydroxide
Corrosion
Cream of tartar
Creosote
Cyanoacrylate glue, "Supaglue", " Astrabond"
Detergent
Dry cell torch battery
Dye
Effervescent fruit salts
Emulsion, face cream
Fat
Food additives
Fire extinguisher chemicals
Flour
Formic acid, ant poison
Gas-Pak
Gelatine
Glass
Graphite, soft lead pencil
Glucose
Gluten, wheat starch
Hydrogen peroxide
Hydrochloric acid, muriatic acid, cleans bricks and masonry
Ice
Ink
Iodine, tincture of iodine antiseptic for cuts in the skin and mouth gargles
Iron, nails, tie wire, steel wool
Kerosine, kerosene, paraffin oil
Lead, fishing sinker, roofing material
Lemon juice, citric acid, deodorizes, mild bleach, cleaner
Lime, garden lime
Linseed oil
Magnesium hydroxide, milk of magnesia medicine
Magnesium sulfate, Epsom salts medicine and garden fertilizer
Methylated spirit
Milk
Olive oil
Petrol, gasoline, motor oil, grease
Petroleum jelly, petrolatum, "Vaseline"
Paraffin
Polymers
Potassium permanganate, Condy's crystals, disinfectant
Putty
Polyvinyl acetate, "white glue", e.g. "Aquadhere"
Rust
Red lead paint
Silicon carbide
Silicone sealant, "Bathtub Caulk" "Silicone Sealer" for fish tanks
Sodium silicate, waterglass egg preserver
Silica, quartz, quartz sand
Soap
Sodium bicarbonate, bicarbonate of soda, water softener, cleaner, mild disinfectant, absorbs odours
Sodium carbonate, washing soda, dissolves grease, disinfectant, softens water, cleans stains, absorbs odours
Sodium chloride, common salt
Sodium metabisulfite, home brewing sterilizer
Sodium hydroxide, caustic soda, dissolves grease in drains
Solder
Starch
Sucrose, sugar
Sulfur
Talc, talcum powder, geological talc, tailor's chalk, magnesium silicate
Tin
Tungsten carbide electric lamp filaments
Turpentine, turps, used for thinning oil-based paint
Urea
Water
Yeast
Zinc
19.4.2 Kitchen hints
Wash foods containing flour or eggs and milk glasses in cold water, Hot water cooks the food onto the utensil
Remove scuff marks on the floor with an ink rubber. remove stubborn marks with turpentine and steel wool.
Prepare floor polish with vinegar and kerosene
Clean chrome plated taps, with kerosene
Sink blocked with congealed grease to use hot water to melt the grease then caustic soda to dissolve the grease or use plumbers suction cup
Prevent used steel wool rusting by keeping in jar of soapy water
Shine laminated surfaces with methylated spirit
Clean garbage tines with bleach solution
Neutralize bad smell with dish containing vinegar and Condy's crystals
Wipe cut lemon over ant trail. Deter ants wit mixture of borax and sugar.
Run hot water over stuck screw top lid
Cool candle sin refrigerator to stop excessive drips
Rinse wooden chopping boards in bleach solution to get rid of garlic smell
Oil to stop chopping boards, wooden bowls, cricket bat from splitting
Cleaning toaster with brush to not damage element
Lemon rind, zest
Ammonia solution to clean tops of stoves.
Tea solution from teapot to remove fishy smells
Refrigerator
Frost layer absorbs smells
Clean with bicarbonate of soda solution, not detergent. Rinse with lemon juice.
Hot foods in refrigerator produce steam which forms frost
Stop ice cubes trays sticking to freezer shelf by smearing with glycerine
Ice cubes in frost-free refrigerator will gradually evaporate, similarly uncovered food and drink becomes dehydrated
Glasses stuck together, use ice water inside and hot water outside
Tempering glasses with heating in water to boil.
Clean oily pans with oil and salt crystals.
Pressure cooker rubber seal can perish unless use cold water after cooking
Remove "fur" from kettle with by soaking in lemon juice or vinegar.
Clean silver ware tarnished by eggs by putting in aluminium pan and washing soda or dip silver ware in water eggs boiled in.
Clean silver plate with borax and soap solution
Clean copper with salt and lemon
Stainless steel with steel wool and lemon juice Burnt food in aluminium pan with salt and vinegar or ammonia solution
Coffer stains on pottery with bleach or salt and water or washing soda solution
Remove milky ring on able with mayonnaise
Heat stains on abel rub with kerosene then eau de cologne to remove excess kerosene
Stains on marble with lemon juice or vinegar
Clean vacuum flasks with bicarbonate of soda
double boiler
Jelly form gelatine calves feet animal and fish bones, agar agar from red algae, isinglass from fish bladders, aspic = jelly + fat free meat or vegetable stock
radish shapes (turgor effects) to make petals, curled celery curl outwards in water
safety
saucepan handles, wet cloth used to transfer hot pan, frying wet foods, water spatters when meets hot fat, first aid for burns, chill or put affected part in ice cold water, do not put fat on burns,
raw shellfish
vitamins
19.4.2.1 Stain removal
1. Stain removal depends on solubility and chemical reactions. Clean stains immediately to prevent further chemical bonding to the material. Scrape off excess solid and soak up excess liquid. Try the treatment first on an inconspicuous part of the material. Work inward from the edge to prevent outward diffusion and spreading of the stain. Do not rub. Allow material to dry before consecutive treatments.
2. Salt heated in the oven and rubbed into serge or gabardine will remove stains and grease spots.
3. Table of stains and treatments (a) to (l)

beer (a)
chocolate (a) (b)
fruit juice (I) (b)
ink, fountain pen (I) (a) (f)
paint, oil-base (c) (b) (a)

beetroot (a)
cocoa (b) (j) (a)
furniture polish (b)
lipstick (b) (a)
rust (b) (a) (k)

bleach (a)
coffee / tea (b) (j) (a)
grass (d)
mildew (fungus) (a) (e)
shoe polish (b) (a)

blood (j) (f)
cooking oils (b) (a)
gravy / sauce (I) (a)
milk (I) (b) (a)
soft drinks (I) (a) (e)

burn or scorch (e)
crayon/ marker (b)
grease (b) (a)
nail polish (h) (b)
tar (c) (b) (a)

candle wax (c)
egg (a)
ice cream (a)
salad oil / dressing (b) (a)
wine, red (l) (I) (f)

chewing gum g)
faeces/urine/vomit (a)
ink, ball point (d) (a)
paint, emulsion (b) (j) (a)
wine, white (a)
Treatments
(a) Mixture of wool detergent with one teaspoon of clear vinegar in one litre of warm water.
(b) Organic solvent, e.g. dry cleaning fluid, mineral turps, light petroleum. Be careful! Ensure good ventilation and keep away from flame! Remove stains caused by fatty substances, e.g. chocolate, butter, or grease with commercial dry cleaning solvents, e.g. tetrachloroethylene, CCl2=CCl2. Dry cleaning refers to cleaning textiles with organic solvents rather than water, e.g. chlorinated hydrocarbons such as chlorinated ethylene are used
(c) Mixture of mineral turps with dry cleaning fluid Be careful! Ensure good ventilation and keep away from flame!
(d) methylated spirit. Be careful! Ensure good ventilation and keep away from flame!
(e) Hydrogen peroxide, 20 vols. Dilute one part to 10 with cold water. Do not use on dark or patterned material. Much stain removal is carried out by oxidation using oxidizing bleaches, e.g. hydrogen peroxide, sodium perborate, sodium hypochlorite. Do not use bleach on wool because it attacks the chemical linkages that hold the wool together.
(f) Dye stripper diluted one part to 50 with cold water. Do not use on dark or patterned material.
(g) Use a freezing agent to solidify the gum, and then scrape it off.
(h) Acetone
(I) Clean, warm water. Do not use hot water.
(j) Cold water only.
(k) Weak acidic solution, e.g. vinegar or lemon juice diluted with cold water. Lemon juice is used to stop fish smells and refrigerator smells, remove kettle "fur", and clean copper and stainless steel kitchen ware. The juice is acidic, and the stain or smell may be acid-soluble. Lemon juice contains ascorbic acid, vitamin C, an active reducing agent, i.e. electron donor, that can reduce molecular oxygen. If the stain is reduced by ascorbic acid to a substance that is not coloured, the lemon juice bleaches the stain. The skin of lemons contains oils, e.g. lemon oil. The stain may be soluble in the oil. Most stains are because of organic chemicals that more soluble in the organic compounds in lemon juice then in water. Lemon juice may convert the stains into substances that are more soluble in water or the lemon juice.
(l) Absorbent powder, e.g. salt or talc. Sprinkle on spillage, leave overnight, then vacuum off. Use large amounts of salt on a fresh red wine stain on a table cloth before the red dye becomes attached to the cloth.
19.5.1 Natural and synthetic fabrics
List the natural and synthetic fabrics found in the home.
19.5.1.1 Permanent crease solution, hair straightening, permanent wave
Hair waving to hair straightening depends on chemical treatment of the disulfide bond in the protein cysteine. The disulfide bonds that give proteins their macroscopic structure can be split at room temperature and slightly alkaline pH by the action of sulfides or mercaptans A reducing agent converts the -S-S- bonds to -SH groups. The hair is combed to straighten and to wave it. An oxidizing agent restores the -S-S- bonds to create straight hair or a "permanent wave". Hairdressing salons use thioglycollic acid in a pH buffer and a cuticle softener to make the internal structure of the hair floppy. This reaction produces the smell of rotten eggs from hairdressing salons! After combing and setting the wet hair, the hairdresser neutralizes the thioglycollic acid with hydrogen peroxide so that new disulfide bonds form to keep the hair in the new shape.
See 16.3.6.0.1: Fibrous proteins and globular proteins | See appendix: Sodium metabisulfite
Prepare a 3% sodium bisulfite solution of sodium metabisulfite solution and add a few drops of detergent. Make a crease with two samples of woollen material. Sponge the solution along the crease in one sample, then press the crease with a steam iron for 30 seconds. On the other sample, press the crease with a steam iron for 30 seconds. Immerse both samples in warm water. Compare the creases. The protein polymer in the treated wool has a "permanent " crease.
Repeat the experiment with human hair to achieve a "permanent wave".
19.5.2 Dyes
Boil the fabric for five minutes in 10% hydrochloric acid. Mix 1 g congo red or methylene blue powder, 4 g sodium hydrogen carbonate, 1 g sodium sulfate, 100 mL deionized water. Slowly add the mixture to water while stirring. Boil the fabric for 4 to 5 minutes and then rinse it in cold water and leave to dry.
19.5.3 Dyes with a mordant
If you cannot dye a fabric directly, use a mordant that combines with the dye and forms an insoluble "lake" in the fibres. A lake is a pigment formed by interaction of a dye and a "base" to metallic salts, oxides and hydroxides. Mordants are hydroxides of aluminium, chromium and iron.
Heat white cotton fabric for 10 minutes in a dilute solution of ammonium sulfate. Then put it in dilute ammonia solution for 5 minutes. Rinse the fabric in clean water and hang it up to dry. Study the effect of the mordant by boiling the mordanted and unmordanted pieces of cotton in methylene blue solution for 5 minutes. Rinse and dry. Compare the colour of the fabrics.
19.5.4 Natural dyes
See appendix: Alum | See appendix: Cream of tartar
Colour: Plant material
Brown: Used ground coffee
Green: Azalea leaf
Purple: Red cabbage leaf
Yellow: Onion skin, marigold (Calendula officinalis) flowers
Heat plant material in water without boiling until dye appears. To make a mordant, dissolve 3 g potash alum [Al2(SO4)3.K2(SO4).24H2O] [also shown as KAl(SO4)2.12H2O] in 100 mL hot water, dissolve 1 g cream of tartar in 100 mL hot water and then put these solutions into an old pot or saucepan. Soak a woollen garment in the warmed mordant solution overnight. Replace the mordant with the dye. Put the woollen garment in the dye and observe the colour change in the wool. Rinse the dyed garment with water and dry slowly.
19.5.5 Washing clothes, washing soda
When washing clothes you need to disperse clay particles and keep them in solution to be thrown away when the washing water is discarded and clothes are rinsed. So washing soda, Na2CO3.10H2O, is added so the highly exchangeable sodium ions displace calcium ions. Detergents use polyphosphates or zeolite to make calcium inactive in the system.
19.6.1 Paints, fire-retardant, anti-fouling, fluorescent, phosphorescent
1. Fire retardant paints contain substances that decompose on heating to give gases that do not support combustion, e.g. phosphates, tungstates, borates and carbonates. Some of these substances fuse on heating to give a glass-like layer on the surface. Other substances are not flammable, e.g. silicones, chlorinated resins, mineral powders. Although water based plants may be non-flammable before use, they may become flammable when painted on a surface and dried.
2. Anti-fouling paints used in marine construction may contain inorganic poisons, e.g. Cu and Hg salts, or organic molecules, e.g. entachlorophenol or organo-tin groups in the polymer. The later decompose to non-toxic inorganic tin on release into the sea water.
3. Fluorescent paints absorb ultraviolet radiation and re-emit it as visible light when irradiated. They contain zinc and cadmium sulfides, and organic dyes.
4. Phosphorescent paints are irradiated with ultraviolet light and continue to glow in the dark after the irradiation has stopped. Phosphors may include ZnS (green, yellow, orange), CuS and SrS (bluish) to other salts to change colour.
19.6.2 Bases in the kitchen and laundry, washing powders, di-sodium tetraborate (III)-10-water (borax)
See 12.10.3: Hydrolysis of sodium carbonate | See appendix: Sodium carbonate decahydrate, washing soda | See appendix: Sodium tetraborate, borax
Alkaline solutions are used for cleaning greasy dishes and for laundry, e.g. washing soda. Washing powders usually contain di-sodium tetraborate (III)-10-water (borax) and sodium carbonate and are alkaline in solution. Baking soda has a basic reaction and can neutralize the acids in fruit or in bee stings.
19.6.3 Metals in the kitchen, aluminium, iron, zinc, chromium
Aluminium and iron are affected by acids in the kitchen. Reactions of steam with zinc on galvanized iron. Cleaning of zinc and aluminium with alkalis. Possibility of aluminium in place of iron in foods by displacement.
19.6.4 Bath cleaning, borax
Mix equal parts of common salt, borax and kerosene into a paste. Rub on a dirty bath to remove dirt and grease. Finish rubbing with a soapy cloth and a dry cloth.
19.6.5 Prepare preserving agents for cut flowers
The bacteria in water will rot the cuts on stems of cut flowers, causing the block of capillaries, a decline in water absorbability and the deficiency in biogenic nutrition, and finally withering up the flowers. Water with a certain amount of a preservative agent added can prolong the life of cut flowers. Preservative agents usually contain the following: (a) Nutritious substances: Sucrose and oxime are usually used. Both serve as source of energy and bring stomas to shut up to weaken transpiration. (b) Bactericide: Silver nitrate, copper (II) sulfate or sodium hypochlorite can be used. (c) Ethylene inhibitor: Silver nitrate or silver thiosulfate is commonly used. (d) Acidified water: The pH value is kept to 3-4.
1. Use a small quantity of alcohol and water to dissolve 0.1 g of oxime in a large beaker and then pour more water in to dilute the solution to 500 mL (the mass percentage of oxime is about 0.02%). Add a few drops of dilute sulfuric acid to adjust the pH value of the solution to pH 5 to pH 6. While stirring, dissolve 0.025 g of silver nitrate (the mass percentage is about 0.005%), and 10 g of sucrose. After mixing this prepared preservative solution, use it for cut flowers.
2. Test quality of the preserving agent for cut flowers. Pour 500 mL of tap water into another large beaker. Put the same number of cut flowers as those in the above experiment in the water. Under the same conditions make a comparison, every three days, about the number of flowers and the water absorbing quantity. Pour 500 mL of tap water into another large beaker. Put the same number of cut flowers in the water. Under the same conditions make a comparison, every three days, between the two cases about the number of flowers and the water absorbing quantity.
3. Some people claim that the best preservative for cut flowers is a solution of 11/2 teaspoons of sucrose in 200 mL of water. Other people recommend a very dilute solution of household bleach.
4. Dissolve small amounts of ammonium chloride, potassium nitrate, and sodium carbonate or camphor in water. These substances are supposed to keep flowers from losing their turgidity by stimulating cells and preventing growth of bacteria. Wilted flowers may revive if the cut stems are placed in a dilute solution of camphor.
19.6.6 Prepare household soap
See also 12.12.0: Soaps and synthetic detergents (syndets)
Add to a tin can half full with water, 2.27 kg dripping (animal fat) free from salt, 0.45 kg resin. Boil for 30 minutes then add 1 tablespoon borax or kerosene and 0.45 kg caustic soda. When bubbling stops (from adding the caustic soda) boil for two hours. Leave in tin for two days then cut into slabs with a tight wire. BE CAREFUL Add caustic soda gradually to avoid boiling over!
19.6.7 Prepare camphor oil
Crush camphor cake. Add salad oil, 5 mL eucalyptus oil, and a few drops of turps. Put ingredients in small bottle. Put bottle in saucepan containing water. Slowly bring water to boil. Use camphor oil when cool.
19.7.1 Perfumes and smells
Perfumes (fragrances) are essential oils usually concentrated in the petals of flowers that may be extracted by liquid fat, ethanol steam distillation and vacuum distillation for more sensitive oils and supercritical solvents, e.g. carbon dioxide. The underarm smell is a mixture of many "notes" (types of smells) mainly isovaleric acid, 5-andost-16-en-3-one and 5-andost-16-en-3-ol also 4-ethyloctanoic acid, the goat smell. The banana scent is isoamyl acetate. Oil of cloves is eugenol. Synthetic musk galaxolide. Mercaptan is a smelly sulfur compound put in odourless natural gas to give it a warning smell. The human male scent is androstenone. The smell of acetone in the breath is a symptom of diabetes. Eau de Cologne 4711 contains lemon, orange, bergamot, and rosemary essences. Garlic odour is formed by enzymes when garlic cells are cut or crushed. Anti-perspirants are based on aluminium salts that form aluminium hydroxide gel in sweat pores blocking the pore.
19.7.2 Lipsticks
Lipstick contains an oil-based wax, antioxidant, preservative, perfume, and colour. The body is made of castor oil and carnuba wax or beeswax. Lipstick must be thixotropic, i.e. stiff in the tube and stays in the tube when the lipstick is put down on a table but liquid under pressure. The original red colour of lipstick, carmine, came the crushed bodies of the cochineal insect, Coccus cacti.
19.7.3 Hair products
In hair, the hydrogen bonds within individual helices of keratin, and disulfide bridges between adjacent helices, give strength and elasticity. Water can disrupt the hydrogen bonds, making the hair limp. When the hair dries, new hydrogen bonding gives hair the shape of the curler. Permanent wave solutions give new disulfide bridges between the helices. Hair contains keratin protein chains in a protein matrix. A single hair may support 80 g. Hairstyles depend on the frictional forces between hairs which can be altered with setting and styling lotions. Wet hair carries 1/3 its weight in water. This increases the friction between straight hairs that combined with the surface tension that drags hairs together makes combing wet straight hair a difficult task. However, with very curly hair, as seen in Papua New Guinea and Africa, water relaxes the hair structure and reduced friction between hairs, so the hair can be straightened. Sulfides at slightly alkaline pH can split disulfide bonds between keratin molecules. The solution is buffered with thioglycollic acid then neutralizes with hydrogen peroxide so that the sets again with hydrogen sulfide given off. The latter accounts for the strange smell coming from women's hairdressing salons where "permanent waves" are produced. Women's hair has a growing phase 6 years and reaches 70 -80 cm. Men's hair has a growing phase 4 years and reaches. 40-50 cm. The black colour of hair is caused by melanin pigment but redheaded people also have an iron based pigment. Hydrogen peroxide bleaches melanin in hair and softens the hair cortex thus weakening it. Old men sometime produce baby hair, called lanugo. A change in humidity twists hair that can be used in novelty "weather houses" to predict changes in the weather.
permanent wave poly (vinyl) pyrrolidine polymers.
Nappy rash caused by bacteria, Bacillus ammoniagenes, from the colon and ammonia from the urinary area.
CO(NH2)2 + 2H2O --> CO3(NH4)2 --> 2NH3 + H2O + CO2
19.7.4 Sunscreens and sun-protective clothing
1. Overexposure to ultraviolet A (UVA) and ultraviolet B (UVB) can cause immediate and long-term skin damage, e.g. sunburn, rashes, tissue damage to premature wrinkling and skin cancer. Many changes with ageing are the result of damage by too much sun. A skin tan occurs when the skin produces additional pigment to protect itself against sunburn from ultraviolet rays. Try to minimize your exposure to the sun between 10 a.m. and 3 p.m. to wear a hat and tightly-woven clothing that covers the body, and use maximum protection sunscreens.
2. Sun-protective clothing fabrics have a tight weave and a dark colour. The garment should have a label listing its Ultraviolet Protection Factor (UPF) value. The higher the UPF, the more the protection from UV rays, e.g. UPF rating of 20 only allows 1 / 20th of the sun's UV radiation to pass through it. For children apply sunscreens with a minimum SPF of 15 about 30 minutes before they go outdoors. Infants should not be in the sun. Sunscreens may irritate baby skin and the developing eyes of a baby are vulnerable to sunlight.
3. The best sunscreens block both UVB (UV radiation with wavelength between 315 and 280 nm), which can cause sunburn, and UVA (UV radiation with wavelength between 380 to 315 nm), which damages the skin without causing sunburn. The peak sensitivity of the skin is the 290 to 320 nm range that causes sunburn and skin cancer. Sunscreen inhibits the production of Vitamin D so 15 minutes per day of direct exposure to the sun is needed. Too much sunbathing is one of the major causes of skin cancer across the world. An immediate but short lasting sun tan occurs the hormone alpha-melanocyte stimulating hormone is made when the body is exposed to sunlight and is responsible for the development of the pigment melanin when pale unoxidized melanin granules near the skin surface are changed by ultraviolet light to the dark brown oxidized form. A lasting sun tan occurs when the amino acid tyrosine produces extra melanin.
4. The higher the sun protection factor, SPF, the more protection a sunscreen offers against UVB, the ultraviolet radiation that causes sunburn. A sunscreen with SPF 10 blocks 90.0% of UVB, SPF 20 blocks 95.0% of UVB, SPF 30 blocks 96.7% of UVB and SPF 60 blocks 98.3% of UVB. The SPF indicates how long you can stay in the sun without the skin reddening about 6 hours after exposure. The exposure needed to produce reddening is called the minimum erythemal dose, MED. SPF = exposed time for MED in protected skin / exposed time for MED for unprotected skin. So if you burn in 10 minutes without sunscreen and you apply an SPF 15 sunscreen, you should be protected from sunburn for 10 X 15 = 150 minutes. However, protection depends on the skin type of the user, amount applied, frequency of reapplication, activities, e.g. swimming, time of day, season, and the percentage of UV reflected to scattered by the environment, e.g. snow to sand. Swimming and perspiration may reduce the SPF value. No sunscreen product screens out all UVA rays. Sunscreens with the same SPF numbers may have different ingredients to different combinations of the same ingredients. Test a new sunscreen first to avoid any allergic reaction. Apply 30 minutes before you go outside and reapply after swimming to activity that causes perspiration. However, invisible damage and skin ageing can be caused by ultraviolet type A, which does not cause reddening pain. Normal sunscreen does not block UVA as effectively as UVB. UVA may cause DNA damage to cells deep within the skin and increasing the risk of malignant melanomas. Claims of "all day protection" should be ignored because an SPF over 30 does not provide significantly better protection.
5. Most sunscreens containing either an organic chemical compound that absorbs ultraviolet light, e.g. oxybenzone, or an opaque material that reflects light, e.g. zinc oxide. The principal ingredients are usually aromatic molecules conjugated with carbonyl groups that absorbs high energy ultraviolet rays. Most ingredients, but not undergo significant chemical change, so they retain the UV-absorbing potency without significant photodegradation. Allowable active ingredients in sunblocks include: p-Aminobenzoic acid (PABA), Avobenzone, Cinoxate, Dioxybenzone, Homosalate, Menthyl anthranilate, Octocrylene, Octyl methoxycinnamate, Octinoxate, Octyl salicylate, Oxybenzone, Padimate O, Phenylbenzimidazole sulfonic acid, Sulisobenzone, Titanium dioxide, Trolamine salicylate, Zinc oxide, Tinosorb (applied to clothing) Mexoryl (not USA).
19.8.0 Common measures
Land: 100 metres (m) x 100 metres (m) = 10,000 square metres (m2) = (104 m2) = 1 hectare (ha) = 2.471 acre = 107,639 ft2
Weight: 1000 grams (g) = 1 kilogram (kg), 1000 kg = 1 metric tonne (t)
Volume, solid: 1 centimetre (cm) x 1 centimetre (cm) x 1 centimetre (cm) = 1 cubic centimetre 1 cubic centimetre (cc, cm3) = 1 millilitre, 1 mL
Volume, liquid: 1000 millilitres = 1 litre (L)
Measure: approximate size
1 teaspoon (the smallest spoon): 4.5 mL
1 dessertspoon (spoon to eat with): 10 mL
1 tablespoon (tblspn) (spoon to serve with): 20 mL
1 teacup (cup to use with a saucer): 250 mL
1 matchbox volume: 25 mL
Area of the top of a matchbox: 20 cm2
1 gallon container holds: 5 L
1 fluid ounce container holds: 30 mL