Jouni Valkonen <[email protected]> wrote:
> Horace wrote: «I would note that steam sparging can have large errors due > to steam escaping, due to variability in measuring the temperature decline > curve, due to variations in the calorimetry constant with temperature, and > due to imperfect stirring techniques.» > As noted these objections are invalid: There is no problem measuring the temperature as long as you stir the water before and after you sparge the steam. There is actually no need to measure the decline curve, although it does improve accuracy somewhat. you do not need to measure it because you do this quickly so that there is no significant heat loss during the process. It is hard to imagine what an "imperfect stirring technique" would be. Just stir it a lot make sure the temperature is the same in different locations. Use several thermometers. > There was not significant steam escaping. Temperature decline was > irrelevant, because experiment lasted only 32 seconds. Exactly. You should not do this for more than 5 min., and you should not let the temperature rise more than 10° above ambient. > And stirring is irrelevant, because sub-boiling water needs to be stirred > only before final temperature is measured. Stir before, too. As I said, use multiple thermometers or move the one you have to different locations. > Steam sparging is very accurate, fast > and simple to do method for calorimetry . . . Yes, it is but it has limitations. It can only be used for brief samples. It is a lot of work and can only be done five times an hour. You should use a tall container for this, with a lot of water in it. Choose a well insulated one if there is one available, such as large Dewar. That eliminates heat loss. - Jed
