A Note Concerning Safety in Bomb Calorimetry As the result of a recent laboratory explosion during a bomb calorimetry experiment, we would like to call ettention to safety precautions to he followed when using a bomb calorimeter. Our incident occurred while igniting a packed benzoic acid sample pellet in a Parr Model 1108 Oxygen Combustion Bomb. Upon ignition, combustion gases vented through a failed outlet valve on the bomb's lid causing the insulatingeover and attached thermometer to be hurled against the ceiling. Considerable noise, smoke, and fragmented glass and mercury accompanied the event, but fortunately, no one was injured. Examination of the failed valve revealed extensive cratering and partial melting of the stainless steel-as if by an ~ contacted A. N. oxygen torch. To explain the explosion we consulted the operating manual,' laboratory t e ~ t b o o k s ? -and Johnson of the Parr Instrument Company. Safety precautions are not always listed, as such, in the literature so we recommend the following safety measures: 1) Although an explosion is rare (we are aware of two other similar bomb failures) the operator(8) should stand back from the apparatus when igniting the sample (for a t Least 20 s). 2) Sample sizes should be restricted to a maximum of 1g to avoid the release of excess heat and pressure. 3) Alwavs check for Leaks before each imition since a Leak could lead to venting of the hot exhaust Eases. 4) ~ a k sure d the oxygen pressure does not exceed 30 atm. The total pressure upon combustion could become too great. 5) Make sure the bomb is entirely covered with water to assist in dissipation of the heat. 6) Occasionally a valve can fail after prolonged use. 7) Powdered samples should always be pressed into pellets because powdered samples can react more rapidly producing a larger pressure pulse.
' "Instructions and M e t W tor Parr Oxygen Bombs." Manual No. 148. Pan l n s h u m t Company. Molina, IL, 1973, p. 8. Aikens, D. A,. Bailey. R.A..Giachano.G.G., Moore, J. A,, Tompkins. R. P.T.. ''Integrated ExperimemalChemistry." Allynand Bacon, lnc.. Boston. 1978, Vol. 2,p. 822. Bettelheim. F. A., "Experimental Physical Chemistry." W. B. Saunders Co.. Philadelphia. 1971, pp. 87-90. 4Daniel%F.. Williams, J. W.. Bender, P.. Aiberty. R. A,, Cornwell. C. D.. and Hsrriman. J. E., "Experimental Physical Chemistry." 7th Ed.. McGraw-Hill Book Co.. New York, 1970, p. 22. SSalrbwg. H. W.. Morrow. J. I.. Cohen. S. R., and Gem, M. E.. "Physical Chemistry Laboratory, Principles and Experiments." The Macmillan Co.. New York. 1978, pp. 73-74. Shoemaker. D. P., Oarland. C. W. Steinteid, J. I..dNibler. J. W.. "Experiments i n Physical Chemistry." 4thed.. McGraw-HiilBook'&.. New York. 1981, pp. 133-137.
Leland Y. Wllson and Roger Tatum Loma Linda University Riverside. CA 92515
902
Journal of Chemical Education
