I'm sure you can still use it for cleaning some equipment. It has become hard due to it being hygroscopic, then solidified. Just break a chunk off and dissolve in hot water.
Instead of Sodium Silicate, the modern day version of B-Brite now uses Sodium Percarbonate, often sold as Oxiclean or one of the cheaper generics. The Percarbonate contains a loosely bound oxygen atom that releases when dissolved and helps kill biofilms, dirt and such. Oxygen has (non-chlorine) bleaching capabilities.
The Sodium Silicate component gives it a lot more cleaning power, especially in hot water.
This old B-Brite product you've got is actually much closer to Five Stars' "PBW" (Powdered Brewery Wash), than the modern day version of it.
One tablespoon per gallon makes a fairly strong detergent for cleaning equipment, fermenters, kegs, etc. If not too dirty it could be salvaged (recaptured) and stored for subsequent use. For long soaks use 1 tablespoon per 5 gallons.
You can make your own (homemade) PBW using 70% Sodium Percarbonate (Oxiclean or some generic brand) plus 30% Sodium MetaSilicate, aka TSP/90, available in hardware stores.