Allen wrote: Fifty years ago, I could have calculated the volume of gas given off by > one gram of oxalic acid dihydrate in a jiffy, and probably found the heat > of fusion and the heat of vapourisation of the dihydrate, too. These days, > I'm a bit rusty. > > I'm betting we have some chemistry whizzes reading who could offer > assistance. > I am not a whiz, but can offer this: The volume depends on the pressure and temperature as well as the molecular weight of oxalic acid dihydrate. The gas law formula is PV=nRT so V (volume) = n (avogadro's number, 6.02 x 10 to the 23) x R (molecular weight, or weight of one mole of oxalic acid) x T (temperature, in degrees kelvin) / pressure (in this case atmospheric pressure, in units suitable to give you the volume in units you want). I think you can assume that blocking big cracks in the hive still does not appreciably raise atmospheric pressure, and you are not so high there in Alberta (although higher than PEI). But the temperature to use for the calculation is problematic. I would suggest that you use the melting point of oxalic acid, although it would be higher initially and lower subsequently. Add 273, I believe, to celsius to get kelvin. To show you how rusty *I* am Allen, before I posted the above I said to myself is R the number of moles or the molecular weight. Turns out it is neither and I had the n and R reversed and the constant was not right anyway for the units. Here is the correct ideal gas law (and if you use the constant from the first version, you can use 1 for the pressure in atmospheres, and calculate the moles from the grams and molecular weight of oxalic acid): With the addition of Avogadro's law<http://en.wikipedia.org/wiki/Avogadro%27s_law>, the combined gas law <http://en.wikipedia.org/wiki/Combined_gas_law>develops into the ideal gas law <http://en.wikipedia.org/wiki/Ideal_gas_law>: [image: PV = nRT \,] where *P* is pressure*V* is volume*n* is the number of moles*R* is the universal gas constant*T* is temperature (K) where the constant, now named R, is the gas constant<http://en.wikipedia.org/wiki/Gas_constant>with a value of .08206 (atm*L)/(mol*K). An equivalent formulation of this law is: [image: PV = kNT \,] where *P* is the absolute pressure*V* is the volume*N* is the number of gas molecules*k* is the Boltzmann constant (1.381×10-23 J·K-1 in SI units)*T*is the temperature (K) These equations are exact only for an ideal gas<http://en.wikipedia.org/wiki/Ideal_gas>, which neglects various intermolecular effects (see real gas<http://en.wikipedia.org/wiki/Real_gas>). However, the ideal gas law is a good approximation for most gases under moderate pressure and temperature. This law has the following important consequences: 1. If temperature and pressure are kept constant, then the volume of the gas is directly proportional to the number of molecules of gas. 2. If the temperature and volume remain constant, then the pressure of the gas changes is directly proportional to the number of molecules of gas present. 3. If the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume. 4. If the temperature changes and the number of gas molecules are kept constant, then either pressure or volume (or both) will change in direct proportion to the temperature. Happy Earth Day Stan *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html Guidelines for posting to BEE-L can be found at: http://honeybeeworld.com/bee-l/guidelines.htm