glass wool

The dark mass was extracted with hot concentrated HCl, the acid extracts filtered through glass wool using a hot water funnel.

A kind of glass wool is produced by drawing out to a capillary thread two glass rods of different degrees of hardness.

Inside the glass wool was a layer of material serving exactly the function of the coating of a bulletproof gasoline tank.

The flask was then allowed to cool, the entering air being filtered through a plug of glass wool or asbestos.

Glass wool serves to hold the calcium chloride and iodine in place.