EFFECT OF GLIDANT ADDITION ON FLOWABILITY OF SOLIDS 487 size decreases. It has been shown that these variables can be related in an empirical equation (12). 71p. m 253p. m Do • 0.60.3 cm 851p. m 71p. m 253pm Do = 0.740 cm 851p. m 71p. m 600• -6ø0 Flow rates, g min-I 7oo-8o• / / ,,,•oo-•oo/••oo 2531J, m I)o=0,898 r.m 851p, m 711•m 71p. m / ,•',oø-:.•:C,• '•øø .%- ½ • --,- Figure 2 The effect of orifice diameter (Do) on the flow rate of multicomponent mixtures of magnesia. Flow rates in g min-t A similar improvement in flowability occurs when fine material is added to binary mixtures of coarse components. Again the particle size of the fine component is an important variable in determining the optimum

488 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS flow conditions. Fig. 2 illustrates the effect of orifice diameter on flow rate in ternary mixtures and it can be seen that as the orifice size increases, the percentage fines required to produce optimum flow decreases. In compression processes, gravity discharge through orifices studies are of limited value since it is the die filling capacity of the formulation which is the important parameter. It has been shown that these particle Table III Glidants reported to have been added to bulk solids. Bulk solid Approx. Method of assessmenl Material arithmetic Source of flowability mean size (gm) Lactose 950 - -149 (7) Flow through orifice Lactose 805 (8) Flow through orifice S.D. -177 (5) Angle of repose and Lactose- flow through orifice Aspirin 541 Calcium sulphate 541 (1) (39) Sulpha- thiazole 213 (35) Angle of repose Lactose 950 -- -149 (7) Flow through orifice S.D. Lactose -177 (5) Angle of repose and Aspirin 541 flow through orifice Calcium sulphate 541 Various tablet (40) Vibrating funnel diluents Lactose 950 -- -149 (7) Flow through orifice S.D. Lactose -177 (5) Angle of repose and Aspirin 541 flow through orifice Calcium sulphate 541 Sulpha- 335 thiazole 163 (35) Angle of repose (1) Various tablet (40) Vibrating funnel diluents Glidant Concentration for optimum Material flowability % w/w 0.5 up to 3 Talc 1 No improvement No improvement up to 4 0.5 up to 1 No improvement No improvement Starch No improvement 5 delayed flow No improvement 0.5 0.25 0.25 Magnesium 0.25-1 stearate No improvement No improvement Delayed flow Polyethylene glycol 4000 Delayed flow Improved flow tablet ' (40) Vibrating funnel diluents (1)