Labnetwest

Technical Tips

The Technical Tips on this page are offerred in good faith and the expectation that the user complies with all safety requirements and uses Risk and Assessment measures wherever appropriate.


Disclaimer:

The Technical Tips on this page are offered in good faith and the expectation that the user complies with all safety requirements and uses Risk and Assessment measures wherever appropriate.

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Alcohol content of wine:

MEASURING THE ALCOHOL CONTENT AFTER FERMENTATION
Use a Vinometer.
If you havent taken before & after specific gravity (SG) readings, or want to check your calculations, you can use a vinometer.
A vinometer is most accurate in solutions containing little or no residual sugar.
The vinometer works on the principle of capillary action, so it actually measures viscosity, which is dependent on the alcohol/water ratio.
It has a scale of alcohol content marked on it.
The procedure is as follows:
* Fill the vinometer with some wine.
* Wait until some drops have fallen through. If the wine doesn't start to flow on its own, put your mouth on the bell-side of the vinometer and blow gently.
* Then put a finger on the part where the drops form and turn it upside down.
* Place the vinometer on a flat surface.
* Release the finger.
The level in the capillary will drop to a certain level, which indicates the alcohol content of the sample
* Make at least two more measurements and take the average value of the measurements:
WHEN YOU PURCHASE THE HYDROMETER, YOU'LL NEED TO KNOW:
* The range of readings, to make sure it will suit the purpose.
A standard range for home brewers is 0.990 to 1.120.
For example, in order to achieve 12% alcohol, you'll want to start at a SG of 1.090.
* What the hydrometer measures.
Some hydrometers only measure specific gravity, but most of the home brew ones measure three things: SG, potential alcohol (P.A.), and sugar content.
* The calibration temperature of the hydrometer. The most common calibration temperature is 60 degrees F.
ALCOHOL CONTENT USING BEFORE & AFTER FERMENTATION SG:
When fermentation has stopped, the final alcohol content can be calculated using the starting and final SG readings.
The following formula can be used:
Alcohol content = (Starting SG - Final SG) / 7.36
Example
The wine started with an SG of 1080, and ended with a SG of 992.
The alcohol content of the wine should be: (1080 - 992) / 7.36 = 12.0 %vol

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Amylase substitute:

Junket tablets, found at supermarkets, are a terrific replacement for amylase.
Start with sample solution of starch or food product, add iodine to show black colour then add a bit of crushed junket tablet and after awhile the solution will go from black to clear.
You can then test the sample for sugar.

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Barium hydroxide

Question:

Why are we getting a precipitate when we mix barium chloride and sodium hydroxide solutions? Barium hydroxide is supposed to be soluble.

Answer:

Pure barium hydroxide is soluble (1.7 to 101.4 g / 100 mL at 0 to 80 degrees C)
Mixing fresh solutions, you will not get a precipitate BUT sodium hydroxide slowly reacts with the carbon dioxide in the atmosphere so that an older solution contains some carbonate ions.
Barium chloride has calcium as an impurity.
Both barium carbonate and calcium carbonate are insoluble.

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Bench protectors/mats:

Here is some feedback on bench protectors:

Masonite (hard board). The boards are not scorch resistant, but won't scratch the benches, are light and easy to store.
Masonite is available at Bunnings.

Hardiflex, or fibro-cement purchased from Bunnings. It is available in 1800 x 1200 sheets and I cut it into 9 boards of 600 x 400. It is hard to cut.
Bunnings may be able to cut it to the required size, but they do charge.

Villaboard, similar to Hardiflex, but it is slightly thicker and more water resistant.
I have found these to be really good because they don’t burn, and spilled materials can be wiped or washed off easily. They are possibly heavier than other materials.
Villaboard can be sawn, or scored and snapped. Edges can be smoothed with sand paper. Fibro-cement cutters are available, either in the form of a guillotine-style, costing about $50, or a cheaper laminate and fibro cutter with tungsten carbide tip.
Available from Bunnings Warehouses.

MDF (medium density fibreboard). We've had these boards for ages and they have lasted well but I don't know how they'd stand up to the rigours of a school.

Bench protection in the form of Benchcote: 515mm x 50m, plastic lined or plain is available from Perth Scientific Equipment, 'phone 9209 3955 (they are agents for Livingstone International Pty Ltd).

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Bitter taste test:

Try tonic water, Angostura Bitters and instant coffee, either in a fairly concentrated solution or straight onto the tongue in powder form.
Diluted Angostura Bitters has the best success.

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Blindfolds:

To prevent cross-infection when using blindfolds, the following types are suggested:
Cut up black plastic garbage bags into wide strips, long enough to go round a head and then tie up. Fold the strips in half. Ask students to place in the bin once used.
Cover the safety glasses with alfoil.
Use the cheap disposable face masks available from Livingstone in boxes of 100. They have elastic ear loops.

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Blood typing activity:

Recipe for fake blood and antisera
Use only enough food dye, carmine or congo red to obtain desired colour for fake blood.
Keep all samples in sealed airtight containers after preparation and before use.

Blood Group A = HCl + red dye
Blood Group B = H2SO4 + red dye
Blood Group AB = HCl + H2SO4 + red dye
Blood Group O = Water + red dye

Antisera A = AgNO3 solution
Antisera B = BaCl2 solution
Concentrations of solutions are not critical (all <1M)

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Bones, drying:

1.To dry, for example, a whole rat skeleton, boil it down with some bleach in the water to get rid of all the remaining flesh, gristle, etc then dry it in the sun.
2.First scrape out the marrow then boil the bones for about 15 minutes in a solution of sodium bicarb. (a few tablespoons in 2L of water.) If the bones are very large, you may need to boil one end first then turn the bone around to boil the other half. Soak overnight in a lab tray containing a solution of household bleach (about 5 – 10%). Thoroughly rinse then dry in the oven on a very low heat.

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Calcium carbonate removal from aquaria:

1. Use elbow grease and rub with a nylon scourer. Rinse with water.
2. Soak in white vinegar, maybe over a few days. Rinse well. You can probably use vinegar for the cover glass, but NOT for anything inside the tank.
3. Elbow grease again, using a one-sided razor blade. Rinse well.

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Charles' Law Apparatus

Question:

Is there anybody who knows about an alternative to the apparatus that is being used in Exp.12 STAWA Lab Manual: Charles Law? We have one, but it didn't work the last time we used it.

Answer:

The apparatus should work fine, but it is necessary to tap the mercury bead before taking a reading as it can become stuck.
An alternative way of using the same apparatus is to begin with boiling water and then reduce the temperature by adding cold water.
It is also essential to have the FULL length of the region below the mercury bead IMMERSED in water.
One practical uses methylated spirits instead of water! This is not allowed since a Bunsen is used to heat it. Only hot plates should be used for heating meths. There is no need to use meths anyway.
Serrata Pty Ltd sells apparatus for this experiment, which apparently works well. Product no.010029. E mail: serratalesley@ozemail.com.au

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Cheek cell alternative:

Good epithelial cells result from scraping the smooth side of a lamb’s tongue with a moist toothpick, using the broad end of the toothpick. The cells are larger with more nuclei.
Beef tongue can be used too but the results aren’t quite as good.
You can show epithelial cells with nuclei from commercially prepared slides (squamous epithelium).

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Chlorophyll chromatography

Question:

What is the best solvent to use in the extraction of pigments from chlorophyll? We have tried ethanol, acetone and a 50/50 solution of the two, but the bands aren't great.

Answer:

You can use 1:1 ethanol: petroleum ether to extract the pigments then 2 percent ethanol : 98 percent petroleum ether to separate them.

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Chloroplasts

Question:

Does anyone know of a suitable water-plant for year 8s to be able to observe chloroplasts under the microscope?

Answer:

Use Valis (Vallisneria).
Just pop it on a microscope slide, give it a little squash with your thumb and view. You don't even need a cover slip and no stain. Just make sure you use the thin bit from the tip.

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Crucibles- what to do after burning Magnesium ribbon:

1. Reuse for the same prac only.
2. Soak in 3M or conc. HCl
3. Try dishwashing powder (has enzymes in it)
4. Throw away

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Crude Oil Recipes:

Mix in roughly equal parts, the following:
Petrol, diesel and used motor oil (ask a petrol station or service garage for their waste oil), or
Turpentine, kerosene and clean motor oil (supermarket or hardware stock is fine)
This should give a mix of boiling points from about 40 to about 300 degrees C.
Crude oil mixture suitable for fractional distillation:
1 part kerosene
1 part petroleum spirit 40-60 C
1 part sewing machine oil or sump oil for a more natural appearance

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Desiccators, glass verses polycarbonate:

For long periods of time, or when a vacuum is needed, use glass only.
If it is only for overnight or not under vacuum, polycarbonate is suitable. They don’t have a good seal on them like glass desiccators so the silica gel needs checking regularly. They are unbreakable, can be easily washed and are very light-weight. To protect from hot objects like crucibles, cover the rack inside with aluminum foil and puncture it where the holes are. Never put acetone near them.

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Dialysis/cellulose tubing substitute:

Try using plain label small freezer bags instead of cellulose tubing. It's a lot quicker and a fraction of the price. Possibly most suitable for lower school.

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Digital camera-uses:

Digital cameras can be used take pictures of:
Experiments - especially physics experiments, which you usually set up once a year. These, along with the experiment instructions, can be kept in a file.
Field Trips - the terrain, clouds, orientation, experiments, finds, Science Technician snoring. Make these available to students who have missed the trip.
Equipment - for insurance purposes.
Students who hand in their assignments to you instead of the teacher!
Gloves and offal, and place picture next to the appropriate bag or bin. Also very helpful for students with language problems.
Get your butcher to cut a pig's head in half (nose to neck) and photo brain, pituitary gland etc.

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Dishwashers:

The following are recommendations for dishwashers in school science departments:
1. Probably most schools would have a domestic dishwasher. They work very well. We have a Whirlpool 6ADP 962, which features a half-load option and on the lower rack the plate holders can be laid flat to accommodate larger items. Test tube baskets are available from scientific suppliers.
2. We have a Westinghouse 950, our second one. The first lasted 6 years.
3. I have a Miele commercial.
4. The Simpson Silencio 850. It has plenty of space and you can take one of the lower racks out to put cutlery baskets in for test tubes etc. Baskets are expensive though, and it might be worth while bargaining to get one or two extra at a better price at the time of purchase.
It is recommended that all glass-ware be rinsed before washing to remove any acid or alkali which can make holes in the base of the machine.

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Egg de-shelling:

Soak eggs in clear vinegar for around 1 to 3 days prior to use, making sure the eggs are completely covered. After soaking the first day, use gloves and remove any scum that has built up on the surface. Top up with vinegar or replace with fresh vinegar. Finally, gently buff the eggs with a soft sponge to remove any trace of shell. Most of it dissolves. The final egg has a clearer membrane than if hydrochloric acid is used.

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Egg protein substitutes:

1.Try using gluten flour. It seems to react with the modified biuret reagent.
Using 1M sodium carbonate with a couple of drops of 0.1M copper sulfate gives a violet precipitate for positive protein.
2.Try gelatine gels. They are about 90% protein (might be an idea to try some jelly cubes).
3.Try the egg replacement powder which is used in cooking. As it has similar properties in the cooking process, it may work
4.Marshmallows are almost pure protein.
Beef extract powder might work.
5.Use albumin flakes in lieu of real egg white. The supplier is Perth Scientific
6.Use soya beans
7.10% Gelatin solution instead of egg white suspension, for the year 8 experiment involving testing food for protein, fats & carbohydrates.
Need to keep it warm or it solidifies

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Electro-magnets

Question:

Has anyone a good design for electro-magnets that actually works? It seems the designs in the texts are rather weak and not very effective.

Answer:

In order to have sufficient current passing through the wire, the wire must be rated to carry at least 3 amps. Wire of this thickness can cause the electromagnet to be quite bulky, so it is suggested that you use a nut and bolt of about 10-12 cm long, or a very large nail.
The strength of the magnet depends on the number of turns of wire around the nail plus the size of the current passing through it, which is dictated by the voltage applied. So you have to use lots of wire - at least 5 metres, preferably 10, for each electromagnet.
Bumping up the voltage will increase the strength of the magnet, but if you dont have lots of turns around the nail, then you are effectively just shorting out the power supply, which causes the overload switch in the power supply to trip out. No problem, just not good practice and its inconvenient.
A way to overcome the power supply being shorted out is to put a globe in the circuit. Use a Hodson light box and the students can see the varying brightness of the globe according to the voltage and the related ability of the electromagnet to pick up, for example, paper clips.

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Energy content of food: peanut substitutes:

To determine the energy content of food products, substitute the following for peanuts: Cheezels, Doritos, potato chips, Vegie Chips, marshmallows, Tiny Teddies, Twisties, corn chips or Burger Rings.

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Enzymes- recipes:

Diastase:
Recommended working strength: 0.1 gram powder/100 ml 0.1% buffer
Reaction buffer: 0.9% Sodium chloride, 0.01% Calcium chloride, pH7
Optimum temperature: 20 -25 degrees C
Solution: always use fresh; will last for 12 hours at 4 degrees C
Pepsin:
Recommended strength: 0.1-0.5 gram/100 ml 0.1 -0.5% buffer
Reaction buffer: 0.9% Sodium chloride at pH2; acidify with glacial acetic acid added drop by drop
Optimum temperature: 35 -40 degrees C
Solution: fresh solution is best; will last for 18 hrs at 4 degrees C or 12 hrs at room temperature

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Eyes-preservation

Question:

Can you please tell me how to preserve eyes for dissection?

Answer:

Just keep them in isotonic saline (0.9% NaCl) in the fridge for up to one week. Change daily. If for longer, freeze them in the saline water.
For additional hints, see the Regional Technicians web site:
http://www.rtg.wa.edu.au/solution/probsoln.htm#eyes

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Frogs and tadpoles:

From Frogwatch (frogwatch@museum.wa.gov.au):
It is not okay to collect taddies from local streams and wetlands, even though it is for classroom use.
You can send out a letter to parents in the school asking if anyone has taddies in their garden pond. You can look after them in an aquarium and as they turn into frogs they must go back to where they originally came from.
As the taddies are turning into frogs, they will need a place to sit on. They do this even before their tails have completely disappeared.
Feed tadpoles a small amount of lightly steamed, finely sliced, lettuce and the fish flakes you get from the supermarket. They are quite voracious eaters.
The main ones you find in ponds are motorbike frog taddies which will start breeding in late November.

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Gas cylinder safety:

BOC have a booklet Guidelines for Gas Cylinder Safety which explains everything from handling to storing cylinders.

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Glassware cleaning:

The list of cleaning solutions and methods for specific contaminants presented here should cover most of the glassware cleaning a technician may have to perform. If an automatic dishwasher is used a final rinse with distilled water may be required before drying.
CLEANING SOLUTIONS:
A. Basic permanganate solution.
Dissolve 20g of potassium permanganate and 50g of sodium hydroxide in a litre of water
B. Hot detergent mixture. Use sparingly to avoid excess foaming
C. Propanone
CLEANING METHODS:
A. Stopcock grease (petroleum base)
Dissolve grease in propanone, wash with detergent, rinse with tap water, rinse with distilled water.
B. Stopcock grease (silicone base)
Soak for 1 hour in fuming sulfuric acid in fume-hood, rinse with propanone, rinse with tap water, rinse with distilled water.
C. Fat and oil contamination
Soak in basic permanganate solution, rinse in tap water, rinse in distilled water.
D. Iron stains
Rinse with 10M hydrochloric acid solution, rinse in tap water, rinse in distilled water.
E. Permanganate stains
Swirl a small amount of acidified iron (11) sulfate solution in stained glassware, wash with detergent, rinse with tap water, rinse with distilled water.
Oxalic acid solution also works.
F. Enzyme contamination
Rinse with dilute nitric acid, wash with detergent, rinse with tap water, rinse with distilled water.
Any remaining stains can be treated as follows:
White deposit- soak in sodium metasilicate (5% aqueous).
Carbon deposit- soak in 6g trisodium phosphate and 3g sodium oleate in 100ml water.
Indelible pencil- wash with propanone.
Iodine- soak in sodium thiosulfate solution 25g/L.
Sulfur deposits-soak in dilute solution of ammonium sulfide.
All solutions listed as dilute are approximately 2M.
The rinsing operation must be carried out thoroughly.
When a piece of glassware must be dried quickly after it has been cleaned, a rinse with high grade propanone may be carried out.
The cleaning operation may be simplified by placing stained or contaminated glassware into detergent solution after use.
Spectrophotometer cuvets and other delicate glassware must be handled with extreme care and not subjected to the harsher cleaning agents.

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Globes-memory aid:

Small globes come in 2V, 6V and 12V sizes. The filament colours of the ones we use are different and the 6V globes are bigger than the others, so I find it easy to tell the difference.
I now have the following poem pinned up near the globes.
GLOBES!
Blue are 2
6 are fat
12 are white
Remember that!

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Hydra culture:

Hydra is available from Southern Biological Services Pty Ltd, Victoria.
Place Hydra in an 11cm petri dish or other glass or hard plastic container.
Add about 2.5cm of Evian spring water. This seems to give the best results. It has been found that Hydra do not thrive in other types of spring water.
Change the spring water once a week, and feed with brine shrimp (and/or Daphnia) every 1 or 2 days.
To culture brine shrimp:
Follow the directions that come with your brine shrimp (aka sea monkeys) eggs, or:
1% salt (NaCl) solution.
500ml beaker.
Air pump with tubing, no air-stone.
Piece of white cloth for straining and rinsing.
Spring water.
Add about ¼ teaspoon eggs to about 400ml 1% solution.
Aerate.
Shrimps will hatch in about 24 hours.
To feed the Hydra:
Pour brine shrimp into a flat container, and shine a light at one edge. The shrimp will swim towards the light in 15 to 30 minutes. You can also just shine the light at the top of the beaker, after turning off the air stone.
Place the piece of cloth over a beaker. Collect the shrimp with a pipette, and squirt it onto the cloth.
Rinse the shrimp with distilled water. Using a clean pipette, draw up the shrimp. Move the brine shrimp water in and out of the pipette.
Squirt rinsed brine shrimp over the Hydra, attempting to hit most of the tentacles.
Hydra can also be fed on thawed frozen brine shrimp. They will feed if the food is pushed onto the tentacles with a pipette.

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Hydrogen peroxide decomposition

Question:

Re experiment 36 in the STAWA Chemistry Laboratory Manual, Factors affecting the rate of decomposition of hydrogen peroxide, what it is in liver that is a catalyst for the decomposition?

Answer:

The enzyme which decomposes hydrogen peroxide in liver is catalase.
The experiment works well.

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Hydrogen Pop Test -Dangers:

Although most people have not had a problem with the hydrogen "pop" test, some schools have, with several cases of test tubes exploding and injuring students.
It seems to be either inferior glassware, or students doing the pop test too close to the Hydrogen gas source, or a combination of both.
It is recommended that Pyrex brand test tubes be provided for this experiment.
They are available from Crown Scientific.

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Incubator alternatives:

Here are tips for growing cultures without an incubator or a warm place such as a hot water system.
Use a 40w incandescent globe, still available from Kmart and Big W but not Bunnings. Place petri dishes side by side and cover them with black plastic (bin liner). To keep a check on the temperature, place a thermometer under the black plastic.
The lamp needs to be 20cm-30cm away from the petri dishes to keep the temperature near to 30 degrees. Optimally, the temperature should be 28 degrees to keep it safe otherwise pathogens may grow.
A heat pad such as those used for keeping reptiles might also work as well as a heat lamp

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Indigo Carmine recipes:

1. 0.25g indigo carmine in 100mL of 50% ethanol.
pH range 11.6 to 13.0 , colour change blue to yellow.
2. 1.0g per litre of 50% ethanol pH 11.6-14, blue to yellow.

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Iodine Water Production

Question:

Have looked at the website and can't find how to make iodine water.
Can anyone help me please?

Answer:

1. The recipe I have is from the Regional Technicians' manual; it is as follows:
Dissolve 12.7g of iodine crystals in 25mL ethanol and dilute to 200mL with distilled water. It is difficult to dissolve and several crystals are often left at the bottom of the solution.
2.10g in 50mL ethanol and make up to 1 litre. Store in an amber bottle with screw top.
3. 2g of iodine and a few flakes of KI and make up to 1 litre

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Laboratory Design Tips:

Have as much input as possible on design (both Science Technician and HOD)
Keep checking floor plans as they are updated.
Chemical resistant bench tops (very limited choice in colours).
Chemical resistant, slip proof, strong durable vinyl floors.
Stainless steel sinks with an outer lip are recommended.
Island bench stations, with storage cupboards below.
Lots of storage space.
Large Teacher’s workbench with storage and narrow cupboards behind.
‘Gratnell’ trolleys and storage system.
Lots of power points.
As for the legislations, and safety specifications, the architects should have all this information. If they do not, don’t use them!

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Lens cleaning:

Here is a tip for cleaning objective lenses on microscopes: Cotton buds are too big to reach inside the protective recess but toothpicks (the strong double-ended round ones) are ideal.
Dip in alcohol or white spirit to dissolve the build-up and then the fine tip can be used gently like a brush. Finally, wrap one in a piece of lens tissue and use to polish the lens. The wood doesn’t seem to scratch and the lenses come out very clean.
It is not necessarily a recommended method for expensive lenses.

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Limewater filtering:

Filter limewater through a coffee filter paper instead of decanting. It filters very well and is very quick.
Use Harris brand unbleached natural paper size 102 but it probably doesn't matter which brand.
Normal lab filter paper clogs up and is very slow.

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Luminol and (fake) blood detection:

The following web site has information on the use of luminol for blood detection, plus suggestions for replacing blood with potassium ferricyanide or other chemicals:
http://chemistry.about.com/od/glowinthedarkprojects/a/luminolblood.htm
Apparently it works well but fades much faster than with real blood.

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Manganese dioxide:

Question:

How do you make the manganese dioxide pellets used for oxygen preparation please? The use of dilute hydrogen peroxide with the manganese dioxide powder produces a reaction thats often too vigorous and rapid.

Answer:

One part manganese dioxide to three parts plaster of Paris.
Make a paste and leave it to dry over 2 days then break it into small pieces which fit the test tubes.
Or, you can role the paste into pellets of a size suitable for test tubes and let them dry.
Can be re-used.

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Mealworm husbandry

Question:

Help! My mealworms have all died! Does anyone have any tips on keeping mealworms (alive) please?

Answer:

Purchase from the Bird & Fish Place in Welshpool Road Wattle Grove. Put them in unprocessed bran in a black bucket and feed them potato.
The Perth Aquarium, 1234 Albany Hwy, Cannington ph 9351-8362 is also a supplier and has the biggest and best mealworms. They also sell crickets.

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Methylene Blue stain removal from microscope slides:

Soak the slides in a household bleach and detergent solution. Put a warning label on the beaker indicating that it contains bleach.
Rinse thoroughly after a day or two, wearing gloves, lab coat and safety spectacles.

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Nut substitutes :

Substitutes fot the nut-burning experiment include Cheezels, Dorrito’s, potato chips, Vegie Chips, marshmallows, Tiny Teddies, Twisties, corn chips, Burger Rings or Pringles. The higher the fat content the better, so check the label.

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Nutrient agar:

For 18 to 20 plates:
5g commercial Nutrient Broth (a powder) from Southern Biological
(Or 1g Beef Stock Powder & 2g Peptone)
10g agar powder
500 ml distilled water.
Weigh agar. Add water, stir until dissolved.
Add nutrient broth.
Heat carefully until boiling. Don't boil over.
Pour into Schott bottles-with the blue cap. Put cap on loosely.
(Or pour into conical flasks and stopper loosely with cotton wool)
Sterilise 20mins at 151 lb/sq in. in an Autoclave or pressure cooker.
Cool a little and pour into sterile petri dishes. using the ‘Aseptic Technique’.
Seal in clear plastic bags, in the fridge. Store upside down; this stops the media from getting wet.
Once inoculated, the plates must be sealed around the edges with Parafilm or wide sticky tape or completely wrapped in cling wrap.
Inoculated plates must not be reopened.
Do not dispose of contaminated plates straight into the bin.
The Health Department insists that THE PLATES MUST BE RE-STRERILISED IN AN AUTOCLAVE OR PRESSURE COOKER BEFORE DISPOSAL.
If this can't be done then the experiment has to be cancelled.
Place into an oven bag, and re-sterilise as above. They are then safe to throw into the bin.

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pH solutions:

RECIPE 1:
pH 2: 25ml 0.2M potassium chloride plus 13ml 0.1M hydrochloric acid made up to 250ml with distilled water.

pH 6: 50ml 0.1M KH2PO4 potassium dihydrogen phosphate (potassium dihydrogen orthophosphate) plus 5.6ml 0.1M Sodium hydroxide made up to 250ml with distilled water.

pH 10: 25ml 0.2M potassium chloride plus 50ml 0.1M boric acid (H3BO3) plus 43.7ml 0.1M sodium hydroxide made up to 250ml with distilled water.

RECIPE 2:
pH 2 use 0.01M hydrochloric acid

pH 6 37ml 0.1M citric acid plus 63ml 0.2M disodium hydrogen phosphate

pH 10 use 0.1M sodium hydroxide

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Potometers:

1. To make your own potometer, just bend a 40cm piece of glass tubing a third of the way down. Attach a 10cm piece of rubber tubing to the longer end. Use an appropriate size stopper with a hole in it at the other end of the rubber tube.
Or:you could just buy one from Southern Biological Services.
Then insert a stem with a few leaves into the hole in the stopper. Assemble all this under water so that it contains no air bubbles. Keep the short end of the glass tube in the water and use a needle syringe to insert an air bubble in the glass tube (under water).
Through the process of transpiration the air bubble moves up and along the glass tube. By using a ruler along the long end of the glass tube you can measure the distance travelled over a certain time. To redo the experiment, insert a needle syringe, full of water, into the rubber tubing and the water will push the air bubble back to the opening ready to start again.
2. Use 2M NaCl and a woody stem (approx 10cm diameter) with leaves, and attach multimeter probes at the base of the stem and 3/4 of the way up. The voltage increases until the NaCl reaches the second probe.

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Quadrats

Question:

The students have just used and demolished my flash quadrats.
They are made out of the white reticulation pipe and then filled with sand. However, I think this stuff perishes and goes brittle after a few years as the quadrats seem to have just fallen to bits.
This has got me to wondering - what are you are all using?

Answer:

1. Use some metal rod, 2 pieces per quadrat, at 1.8m each. Bend each piece at 90deg, 40 cm from each end. i.e. 40cm, bend, 1m, bend, 40cm. Join each with a 20 cm piece of plastic tubing on each side, to make a 1 metre square. This is useful as they can bend - ideal for field-trips.
2. We use a metre ruler that has a hole at each end with 3 metres of string connecting to either end. You lie the ruler on the ground and arrange the string as a one metre square. Nice and cheap to make and you wrap the string around the ruler when not in use.
3. PVC reticulation pipe breaks down quite quickly (amazingly enough it is used to reticulate the natural gas supply around Perth!). The polyethylene (black) pipe is much more durable, which is why farmers use it in their paddocks, but also more flexible. The large diameter pipe might also be suitable.
4. I think it would be worth investigating for Occupational Health and Safety reasons, as the PVC becomes powdery as it breaks down and therefore can be inhaled or ingested when handled.
5. We have some made out of aluminium. They are light to carry and don't weather. Also have some with just 4 tent pegs and nylon rope.
6. We have used 1/4 square metal (6mm mild steel rod) for at least 8 years. They were made from one piece, bent, then welded in a corner. This was then powder-coated, cherry-red colour so you cannot leave them in the field. Works great.
7. I made quadrats out of flat wood from Bunnings and used wing nut screws at each corner, this way when they are not in use I fold them flat and hang them up on hooks.

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Rock Storage:

Try tool trolleys from Bunnings; they are heavy duty. Most are lockable.
Use an old set of metal pigeon holes with wheels so it can be moved when needed.
Use Decor ones from Woolworths. Colour coded sedimentary -blue, igneous - red and metamorphic - yellow. Paint each rock a small patch with some white paint and number them using a marker to create a reference guide.
Use IKEA cubed systems. Have the option of purchasing pull out wooden drawers or boxes to suit your need.
Use metal cupboards on wheels from Bunnings that are lockable. Bunnings does have a reasonable range with drawers and cupboards.

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Safety spectacle cleaning:

Most Technicians put safety glasses through the dishwasher at the end of term, although there is evidence that dishwasher detergent damages the plastic so it’s probably best to put them through without it.
These are some of the products used to clean the glasses or provided in each lab for students to use: diluted Dettol, Pine-o-cleen (diluted 1:20), Uvex lens cleaner.
It is advisable to provide a non-flammable cleaner for labs.

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Saliva substitute:

Use 1-3% diatase, which is free from reducing sugars,or 1% bacterial amylase. These chemicals are available from Southern Biological.

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Sealing chemical labels:

These spray can products are recommended for water-proofing/sealing of dropper bottle and reagent bottle labels:
Micador Permanent Matt Finish, from SupplyWest Bookland
Wattyl’s Estapol
White Knight Satin Crystal Clear Acrylic, available from Bunnings
Please note that all spray cans need to be stored in a metal box so they don't become missiles in the event of a fire.

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Sensory Adaptation:

Students block one nostril and sniff a sterile swab dipped in clove oil until they can't smell it any more (adaptation). Then they immediately sniff another swab dipped in peppermint oil. Both smells are detected by the same receptor so they can't smell the second oil either, for
a short while anyway.

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Silver nitrate stain removal

Question:

Any suggestions about how to remove silver nitrate stains from benches?

Answer:

1. I've had good results with a 0.25M solution of sodium thiosulfate but it must be used before the silver nitrate dries.
2. Try Gumption cleaner.
3. Ammonia solution as soon as possible has some effect. Its best if you get students to use the silver nitrate over a tray, newspaper or other bench protection.
4. Bleach actually works really well if you let it sit on the stain for a while.

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Soap making

Question:

We have not had much luck with the Preparation and properties of soap, STAWA Chemistry Lab Manual Experiment 68.
Do you have any hints on how to make it work, or other recipes please?

Answer:

1. The product made in this exercise bears little resemblance to a bar of Dove but, as long as reasonably fresh oil is used, students can observe the saponification reaction.

triglyceride + sodium hydroxide produces sodium salt of carboxylic acid + glycerol

The soap will probably be crumbly and not suitable for personal use!
Note: The STAWA method is simpler than the Heinemann Science 2 (2.8/Expt 5) and we use it for Year 9.
2. Our classes have had quite good results using the soap recipe from the TEE Physical Science Materials book. There are just a few slight differences to the one in the STAWA Lab Manual
3. We make soap the STAWA way in Year 9 as well as in Year 11 or 12. It works, in the sense that the reaction produces the desired product (following reactants and method exactly as in the manual). The product however, is not creamy Lux, rather a crumbly, harsh version, not recommended for the face!
4. We have varied results, some very good, some not even vaguely similar to soap. The only change we made was to use VERY FRESH castor oil bought the previous day. All other things seem to point to operator error.
5. You need to have Watsonia lard (from pigs), not fat.
Its very different to the STAWA method. It can be done in a 60 minute lesson.
Technician melts lard on hot plate in beaker. Then mixes together well equal amounts of lard and olive oil. Reduce temperature down to 50 to 60 degrees C and control on the hot plate.
Student: in 250 ml beaker;
To 100ml of distilled water, add 30 gm of sodium hydroxide stirring constantly, to prevent a lump. Reduce heat of sodium hydroxide solution in a cold-water bath until about 40 degrees C. In 600ml or litre beaker, mix 200ml of oil and lard mixture with 100ml sodium hydroxide solution.
Stir continuously until the mix starts to solidify. Pour into moulds- we use cake moulds.
6. Using Copha (solidified coconut oil), as an alternative to lard is reasonably successful. (Thank you to KH of Queensland for this idea).

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Starch-producing action of enzyme extracts:

This experiment is from Heinemann 'Biology Two" text and work book - Section 4.5 Genes in Action.
You can get good results in this activity using the following procedure.
Use distilled water to make up the solution with the powdered peas.
Use a fluid:solid ratio of 0.5mL of dist. water per seed.
Therefore, you require 15mL of water for the 30 seeds. This was fine for the smooth seeds but the wrinkly ones required an extra 0.5mL per centrifuge tube.
We were able to powder the seeds (using a mortar & pestle) and hold them overnight in an airtight container.
We then added the water and finished the preparation immediately before the lesson.

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Stomata- recommended plant species:

The following species are recommended as good sources for viewing leaf stomata: Agapanthus, German ivy (Senecio mikanioides), mother-in-laws-tongue, wandering “Jew” (Tradescantia) and Bougainvillea.

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Storage solution for preserved specimens:

Phenoxytol storage solution is an alternative to formalin based or 70% ethanol storage solutions.

10mL phenoxytol (2-phenoxyethanol)
50mL glycerol
940mL distilled water
It must be noted that this solution is a storage solution only, and fresh specimens must be properly preserved before storage eg. preserve animal specimens in 10% formalin for 3 weeks, wash well to remove the formalin, then transfer to the storage solution.
Already preserved specimens may be transferred to the storage solution after first washing in water. With phenoxytol solutions, specimens do not need to be completely immersed - although for presentation, it is preferred.

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Thermometer salvage

Question:

How do you fix spirit thermometers where the alcohol has separated?

Answer:

Place the thermometers in a beaker of vegetable oil and heat the oil using a Bunsen or preferably a hot plate which is safer. The oil will heat to over 100 degrees C which means all the spirit will then join up again at the very top section of the thermometer.
Keep a watch on them and remove them from the oil when the spirit rejoins.
You must keep a very close eye on the thermometers because of the pressure build up. Wear safety glasses etc because the spirit has been known to burst through, most likely around the bulb at the bottom, as the glass is thinner there. If done carefully, the job can be managed without breakage. Do not be overly-alarmed at potential breakage. It is not violent, just messy and with appropriate eye-protection and lab coat you should be perfectly safe.
This method does not fix them permanently so you may find that some separate out again after numerous uses.

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Thermometer-use for broken ones:

Here is a use for those dead spirit thermometers:
Using your tubing glass-cutter, remove the spirit end and you have a glass stirrer.
Remove both ends and you have graduated capillary tubing.

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Thin Layer Chromatography (TLC):

Materials:
Thin-layer chromatography plate and a pencil (not a biro or felt tip pen)
Four test tubes in a stand and labelling
Three capillary tubes for use as micropipettes
Chromatography chamber: either a screw top jar tall enough to take the TLC plate, a small beaker with a Petri dish for a lid, or a commercial tank.
Access to a fume cupboard and short wavelength UV lamp
Chemicals:
For this particular experiment, both crude and re-crystallised samples of aspirin are compared with a known sample of aspirin.
Ethanol and dichloromethane
A few iodine crystals (3-4 per experiment is sufficient)
Samples for testing
Ethyl ethanoate as chromatography solvent
Notes and suggestions:
Commercial Chromatography Chambers are 27cm x 26.5cm x 7cm deep- just like a fish tank with no grooves inside to support the plates are very expensive!

You can use beakers, with a Petri dish on top or jars with lids; tall enough to hold the TLC plates. Try Hellendahl staining troughs.

For the TLC plates buy MK-105554 Box/25, 20cm x 20cm which is basically silica gel painted onto aluminium sheets, from Perth Scientific. You can cut these to size with scissors to fit the staining chambers or what other vessel you use; be sure not to order the glass plates as you will have trouble cutting them to size without them crumbling. They seem to only come in the one size as noted above.

If your school cannot afford to buy these plates, you can make your own using 50g Kieselguhr (silica gel powder) mixed with 60mL water. Make a paste and paint it on glass microscope slides (one side only) and allow to dry before use.

Can also use glass/plastic jars with screw-top lids (depending on the solvents in the mobile phase) or even beakers covered with cling-wrap. Do not use ice cream containers; the containers themselves work fine (if the plates are small enough to lean against the sides) but alcohols crack the lids.

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Water electrolysis:

NOTES FOR LAB STAFF:
Equipment:
0.5 M or 3% v/v sulphuric acid + spill tray
Hoffman voltameter + electrodes
2 x stopcocks to fit voltameter
power pack + leads
crocodile clips
retort or voltameter stand
petroleum jelly
dissecting tray (not board) + bench roll piece
2 small & 2 large test tubes + stoppers
test tube rack or 600mL beaker
wooden splints (short AND long)
gas lighter
ceramic tile for hot splints
Can use 0.2 M or 0.5M sodium sulfate instead of acid. It works well and is not corrosive. Add a few drops of bromocresol green indicator to it. When current is passed through, blue colour develops at cathode (hydrogen ) and yellow at the anode (oxygen). Need to use fresh solution for each electrolysis
Setup:
Check all parts (BE CAREFUL - VERY FRAGILE!), remove stopcocks and lubricate if necessary (do not re-insert yet). Carefully insert electrodes. slowly add 3%v/v sulfuric acid (or 0.5 M ) almost to top of graduations - AVOID TRAPPING AIR IN TUBING or acid will overflow. Replace stopcocks, matching colour coding if present. Close stopcocks and test operation. Use the 12V setting for best results. Include power pack, leads, lighter, splints and two or more test tubes with stoppers in a rack or beaker.
Reset between sessions:
SLOWLY open the oxygen stopcock (the one with the least gas), being careful not to let the liquid rise too quickly. Close it when the fluid has nearly reached the top, repeat for other stopcock, adjust until tubes are equal. Top up with acid if needed, close stopcocks. If stopcocks stick, remove and grease with a little petroleum jelly. If holes are blocked, clear with cotton bud.
Cleanup:
Open stopcocks, pour fluid down sink. Remove stopcocks and electrodes. Wash all pieces carefully in hot water, using detergent if required to remove petroleum jelly. Rinse well and drain.

NOTES FOR TEACHERS:
The voltameter will be set up ready to use. DO NOT add more water or acid as the fluid in the reservoir should be level with the top of the graduated tubes before switching on. The reservoir is there to hold the fluid displaced by the gas - if you add more liquid, the reservoir will overflow!
Check that the power pack is set to 12V, then switch on. Allow 10min or so for sufficient gases to be produced – check periodically as it may need longer. It is best to wait until one tube is nearly full of gas (the other one will be half-full). Small leaks may occur so the volume ratio might not be precisely 2:1, but it should be close. Turn off the power before collecting the gases.
To collect a gas, hold a test tube over the top end of one of the voltameter tubes, then slowly open the stopcock to release the gas. Be ready to close it again before the liquid spurts out the top! H2 is less dense than air, so keep the test tube open side down while capturing the gas and stopper it before turning upright. O2 is slightly denser than air - insert the flexible tubing attached to the top of the voltameter tube into an upright test tube, then the O2 will sink to the bottom. There might not be enough O2 to fill a large test tube so you may wish to use a smaller one (both sizes provided).
Use wooden splints for both gas tests. Leave hot splints on the ceramic tile until cool.
To test for H2 (from the voltameter tube that was full of gas): pop test
Light a splint and hold the flame just inside the mouth of the upended test tube (keep the stopper in until you upend it or the H2 will escape). The gas will combust with oxygen in the air beneath the tube, making a loud popping sound.
To test for oxygen (from the half-full voltameter tube): glowing splint test
Hold the test tube upright and remove the stopper. Light a long splint, then blow it out so the tip is glowing but not alight. Dip the splint deep into the tube and the O2 should reignite the flame.
To reset the voltameter:
Carefully open the stopcocks and let the fluid level in both tubes - dont let it spurt out the top! Then close the stopcocks.

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Yabbies:

If you get yabbies very small, only just visible, and keep them for the term, you will see quite a measurable growth rate. Once they are older juveniles or adults, they grow at a much slower rate which is not that measurable in a school situation.
For food, we use a 'sinking' pellet rather than a 'floating' pellet which we find to be more accessible for them, but some do prefer the floating type. Also you can get pellets from pet shops.
Keep them in a filtered tank with plenty of places to hide eg. PVC pipes or shade-cloth placed in the tank in a bunch so they can hide. They tend to eat each other.
Here is a website which covers setting up, feeding, handling, disease management and so on:
http://www.fish.wa.gov.au/docs/aq/index.php

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Yoghurt making

Question:

Do you know at what temperature you incubate yoghurt? My instructions say to add a small amount of natural yoghurt to milk and then incubate overnight, but no temperature!

Answer:

The recommended temperature is 44 to 45 degrees Celsius.
Bacteria are inactive below 21 degrees C and are killed above 49 degrees C.

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