Abstract: An apparatus and method for measuring bulk density of solid particles. The apparatus is capable of simultaneously rotating and axially advancing a container containing a sample of solid particles past a source emitting a beam of gamma rays. The gamma rays are absorbed by a detector in proportion to the material density of the solid particles. The absorbed radiation is then compared to a preselected reference value to yield a bulk density for the material. This bulk density can then be used to ascertain the quantity of a binder which needs to be added to a homogeneous mass of coke to form a carbon anode useful in an electrolysis of alumina. The method includes the steps of placing a sample quantity of the solid particles in a container, optionally vibrating the container to settle the particles if desired, and then placing the container on the apparatus so as to be measured. The bulk density measurement is compared to a preselected reference value and this value is then visually displayed.