set to a range of suitable values - chosen from 25, 30, 35, 40, 45, 50, 55, 60 °C
(in addition to room temperature 15 - 20 °C ?)
thermometers
Beakers:
1 large (1000 ml ?) for mixing - preferably marked on sideMaterials (sufficient for 10-12 treatments):
(10 x) 100 ml beakers
(10 or 20 x) 10 ml measuring cylinders
rubber bungs to fit above
forceps
800 ml (red?) grape juice (UHT is OK)
100 ml yeast suspension (ready prepared)
[5g sucrose, 15g dried yeast, 125 ml water - mixed in 500ml beaker & incubated at 30 °C for 30-120 minutes before use]
plastic rod for mixing
After say 5 minutes, pour the mixture into a measuring cylinder, so as to completely fill it, not just to the top of the measurement lines. Holding the measuring cylinder over a tray or beaker, lightly insert the rubber bung. Some overflow must be expected!
Invert the measuring cylinder in the beaker and replace it in the water bath.
Using forceps, remove the bung, ensuring that mouth of the measuring cylinder is still under the liquid. Note the time.
It is possible to get more than one measuring cylinder in a beaker at one time, and to remove and re-use the same rubber bung.
Record the results (level of gas - read with measuring cylinder held vertical) at regular intervals - say every 5 or 10 minutes. Remember that the scale is upside down and there will be a point at which the gas level is below the scale markings. You may need to estimate the value or reset by re-filling the measuring cylinder and keeping a running total.
Time /min | Volume of gas at the following temperatures: /ml | |||||||||
. | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 / °C |
0 | ||||||||||
5 | ||||||||||
10 | ||||||||||
15 | ||||||||||
20 | ||||||||||
25 | ||||||||||
30 | ||||||||||
35 | ||||||||||
40 | ||||||||||
45 | ||||||||||
50 |