Abstract: Non-fused hollow glass microspheres that consist primarily of silicate are rendered more water-resistant by treatment with multivalent metals. The hollow microspheres are slurried with water and then a solution of a multivalent metal salt such as Al.sub.2 (SO.sub.4).sub.3 is added to the slurry. The rate of the addition is controlled so that the pH can be regulated. Separating, washing and drying complete the preparation.

Abstract: Coal dust laden air is treated with an aqueous foam of controlled durability and controlled penetrability so that a very high proportion of the particles in the air, including very small particles, are captured by the foam and drained into the liquid resulting from the collapse of the foam. The foam has a propensity to collapse during a brief period, thus forming drainage liquid. The volume of drainage liquid five minutes after foam generation provides a measure of the controlled durability of the foam. The usefulness of the foam is also affected by the rate at which the liquid resulting from foam collapse is absorbed into absorbtive materials, which rate should desirably be slower than the absorption rate of water. The precursor for the foam is a very dilute aqueous solution containing a surfactant plus a synthetic gum in a concentration from about 15 percent to about 45 percent of the weight of the surfactant.

Abstract: Non-fused hollow glass microspheres that consist primarily of silicate are rendered more water-resistant by treatment with multivalent metals. The hollow microspheres are slurried with water and then a solution of a multivalent metal salt such as Al.sub.2 (SO.sub.4).sub.3 is added to the slurry. The rate of the addition is controlled so that the pH can be regulated. Separating, washing and drying complete the preparation.

Abstract: Products of a generally spherical nature with particulate matter embedded in the walls are prepared by forming a suspension of said particulate matter in a solution of a film-forming substance in a volatile solvent, spray drying said suspension-solution thereby forming the product which may be further dried if necessary to remove solvent and to "set" the walls. Such products can be used to provide pigmenting, reactive and/or fire retardant properties to organic systems to which they are added as fillers. The density of the product can also be controlled by this method for use as fillers in applications in which segregation of such fillers from the plastic matrix is normally a problem.