The reactivity of wet powder slurries depends on the amount of water contained. Powders mixed into more than 30 weight % of water, well slurried,
are safe to handle as they are sufficiently wet to prevent ignition. However, compared to this partly wet material with about 2 - 10 weight % of
water is most dangerous! Such material is easily ignited and will burn explosively, decomposing water and dispersing burning particles over the
surrounding area. Partly wet material will result during drying operations or after a long storage time when wet powders have settled and dried out
in the container to form a hard cake. In sedimented material the water concentration can drop below 10 % thus making the powder very sensitive. In
this case do not attempt to dig up the material by an instrument or spatula as friction could ignite it! Best method for removing wet powders
form a container is to reslurry them by mechanical rolling an a suitable ball-mill-type roller or by shaking the container in a tumbler. Persons
should stay away during such operations. Residues can be washed out by a stream of water. |
