Pier,
          'Ascarite' is Sodium Hydroxide, NaOH, on an Asbestos matrix in a
granular form. The modern equivalent would be 'Carbosorb' which is
normally used in sequence following a separate water-vapour trap filled
with granular Magnesium Perchlorate.  Both are available from
BDH/Merck, or specialist companies such as Elemental Microanalysis ltd.

                                                       Darren.

ITE Merlewood,
 Cumbria, UK.