A new electrical insulating oil composition having improved low temperature characteristics which composition comprises a mixture of 40% by weight or more of benzyltoluene and the remainder of alkyl substituted diphenylmethane having 15 to 17 carbon atoms which is represented by the following general formula: ##STR1## wherein R.sub.1 and R.sub.2 are C.sub.1 to C.sub.4 alkyl groups and the total number of carbon atoms in R.sub.1 and R.sub.2 is 1 to 4, with the proviso that R.sub.1 and R.sub.2 may not simultaneously be methyl groups and the proportion of the total quantity of solid phase calculated according to the following general solid-liquid equilibrium equation is 45% by weight or less relative to the total quantity of said composition at -40.degree. C.: ##EQU1## where X.sub.i is the equilibrium mole fraction of a component i, in the liquid phase, .DELTA.H.sub.i.sup.f is the heat of fusion (cal.mol.sup.-1), T.sub.i.sup.f is the melting point (K), T is the temperature (K) system, and R is the gas constant (cal.mol.sup.-1.K.sup.-1).
一种新的电绝缘油组合物,具有改善的低温特性,该组合物包括40%或更多的苯基
甲苯和剩余的烷基取代二苯
甲烷,其具有15到17个碳原子,其由以下一般式表示:##STR1##其中R.sub.1和R.sub.2是C.sub.1到C.sub.4烷基,R.sub.1和R.sub.2的碳原子总数为1到4,但R.sub.1和R.sub.2不能同时为甲基基团,根据以下一般固液平衡方程计算的固相总量占该组合物总量的45%或更少,该方程为:##EQU1##其中X.sub.i为液相中组分i的平衡摩尔分数,.DELTA.H.sub.i.sup.f为熔化热(cal.mol.sup.-1),T.sub.i.sup.f为熔点(K),T为温度(K)系统,R为气体常数(cal.mol.sup.-1.K.sup.-1)。