User: Cricketfool We have tried this practical twice recently without success. We cut small discs of Ivy (Hedera) leaf and put them into 5ml syringes containing various concentrations of Soium Hydrogen Carbonate with a lamp shone at them. We see which discs rise to the surface first as they produce oxygen. We had no succes despite having got good results last year and in June. We also tried using Potassium Hydrogen Carbonate but again had no success. Is it the weather, temperature...? Any ideas anyone?