Differential thermal analysis of fats. II. Melting behavior of some pure glycerides

TI~OROUGI-t STUDY o f s o m e mono-oleyl d isa turated glycerides has been under taken here as pa r t of a p rogram of research into the s t ructure of fats. Before investigating the behavior of mixtures of disa tura ted triglycerides, it was necessary to characterize the individual pure glycerides. The present paper records the melt ing characterist ics and polymorphism of seven mono-oleyl d isa turated glycerides (designated as SOS; P O P ; OSS; O P P ; POS; OPS; and OSP) as determined by differential thermal analysis and X-ray powder photography. Lut ton (1, 2, 3) has studied the polymorphism of all these compounds while Malkin and Wilson (4) have studied the first two: SOS and POP. Dauber t and Clarke (5, 6) have reported on the first four: SOS, POP, OSS, and OPP. The dis turbing features of their publications are concerned with a) their apparen t lack of agreement as to the number of polymorphic forms; and b) in part icular , the wide divers i ty of reported melt ing points, Xr ay data, and nomenclature. In the present paper the nomenclature of Lnt ton has been followed where the Xray data agrees with his. Where there is no agreement, the nomenciature used is made clear in the text. Fur ther , the melt ing points are approximate values only and have been obtained in a manner similar to that described in Pa r t I of this series.