Abstract: The present invention relates to a process for separating 2,7-DMN, characterized in that a mixture containing at least 50% by weight of 2,7-DMN and the other DMN isomers obtained by preliminarily concentrating a fraction in the range of 250.degree.-270.degree. C. of catalytically cracked petroleum oil is preliminarily adjusted to a temperature of 60.degree.-90.degree. C. to form a slurry containing the crystal of 2,7-DMN, which is placed in a tightly sealed pressure vessel, adiabatically pressurized to the range of 500-2,500 kgf/cm.sup.2 and solidified to form a state of co-existing of solid and liquid phases, liquid is then discharged under pressure from the solid-liquid co-existing system, the solid remaining in the vessel is pressed to discharge the liquid remaining between the solid particles, which are integrated to give 2,7-DMN having a purity of 98% by weight or more.

Abstract: The present invention relates to an apparatus suitable for accomplishing a roll testing method. The object of the present invention is accomplished by hot rolling steel strip under the specified rolling condition using small size testing apparatus having about a tenth size of the actual rolling mill and good reciprocity like said rolling mill. The wear state (roughness), or new state, of the roll surface is estimated by a known type of surface roughness meter from the roll surface generated after hot-rolling the stell strip by the small size testing apparatus of the present invention. Said testing apparatus has the structure in which both the diameter of the rolls and the circumferential speed of the rolls are about a tenth of those of actual rolling mill and the number of the contact times (contact interval) between the rolls and the stell strip per the rolling time is the same to that of the actual rolling mill.