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.
Technical Tips
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…
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…
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…
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.
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…
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…
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.
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…
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…