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.
Posts Tagged with Q&A
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…
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…
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…
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 –…
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…
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…
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…
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.
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.