I was heating water in lab and it took approximately 25 minutes to raise the temperature of my water by 65 degrees Celsius; perhaps the flame wasn't sufficient? I made certain that I could the the reducing and oxidizing flame, yet the liquid heated quite slowly. In addition, the flame was approximately 1/2-1 inch from the wire gauze supporting my beaker (ring stand apparatus). Perhaps there was not a sufficient supply of gas (i.e. gas flow valve not loosened properly)?