The strain gate method of measuring the fluidization quality, proposed by Shuster and Kisliak, has been applied for the fluidization of the Korean anthracite in parallel with the investigation of the ordinary pressure drop vs. Reynolds number plot. The material under test were of several narrow cuts and of their mixtures ranging in size from 0.051-in to 0.0032-in. In each run, about 900 grams of coals were fluidized with air in a 3（1/8）-in glass tube, and the pressure drop readings across the fluidized bed were taken while the fluctuation of pressure drop was recorded by means of a pen os cillograph. It has been found from the plot of pressure drop vs. Reynolds number, that the coal of the wide range mixture gave distinctly an abnormal curve, particularly, as the large size fraction was increased, while the narrow cut samples gave the similar patterns as those of Leva and his colleagues. The pen oscillograph analysis of the pressure drop fluctuation showed that a certain content of fines below 200-mesh size in the mixtures of larger particles was essential for a good fluidization quality of the Korean anthracite. The fluidization qualities in terms of the fluidization index defined by the aforementioned workers, turned out to be immeasurably low in this case, while the values of index were high enough to be safely estimated in all other cases containing no fines below 200-mesh size.
It has been also attempted to establish a chart index for the pressure drop fluctuation patterns by which a direct diagnoses of the fluidization quality inside the non-transparent refractory tube walls could be made possible. However, such diagnoses were found to be not simple although it is not thoroughly an impossible matter. It may be concluded that the diagnoses of the fluidization quality inside the non-transparent wall through the oscillograph recording require an experienced skill.