Abstract: Tubular films having superior mechanical properties and extremely small deviation in thickness can be produced according to a method and an apparatus in which a means of downwardly tapered hollow inverted-truncated-conical shape is placed on the top of an annular die and used as a means for stabilizing bubbles of olefinic polymer synthetic resins which are extruded from the annular die in an air-cooling inflation process with a take-up speed of about 5 m to 50 m per minute.

Abstract: An immersion oil for microscopy is produced by blending 10 to 90 parts by weight of chain hydrocarbon having 200 to 5,000 of molecular weight and 10 to 90 parts by weight of specific diphenylmethane derivatives or bis(.alpha.-alkylbenzyl) alkylbenzene derivatives or 2,4-diphenyl-4-dimethylphenylbutane derivatives.The product obtained has excellent values in the various properties such as light dispersion, refractive index, viscosity and the like. Furthermore, it has an excellent advantage that the properties such as Abbe's number and the like are easily adjustable.