(1) The relative reactivities of various methylphenysiloxanes were studied by the method of equilibration of Kantor using (CH3)4NoH as catalyst．The results are given in Fig．1—5．The reactivities of the cyclic polyphenylsiloxanes and cyclic polymethy-siloxanes were compared by means of copolymerization in the presence of (CH3)4NOH or H2SO4．See Table 1． From these results，methyl and phenyl siloxanes can be arranged in the following order of decreasing reactivity： In basic medium，[(CH3)(C6H5)ao]3>[(CH3)2slo]3>[(CH3)(C6H5)2Si]2O>[CH3)(C6H5)SiO]4>[(CH3)2SiO]4In acid medium， [(CH3)2SiO]3>[(CH3)(C6H5)SiO]3

[(CH3)2SiO]4>[(CH3)(C6H5)SiO]4

[(CH3)2SiO]4>[(CH3)(C6H5)2Si]2O．Increasing phenyl groups increases the reactivity of siloxanes in basic medium with the exception that [(C6H5)3Si]2O being less reactive than [(CH3)(C6H5)2Si]2O．This is prob-ably due to the steric hindrance of the large number of bulky phenyl groups．On the other hand，phenyl group lowers the reactivity of siloxanes in acid medium．(2) Cyclic low polymers of polysiloxane containing small amount of trifunctional groups were prepared by cohydrolysis of (CH3)2SiCl2 and CH3SiCl3．When incor-porated with [(CH3)3SiOSi(CH3)2]2O and equilibrated in the presence of (CH3)4 NOH，the equilibrium was reached only after long time of heating，and there was a lowering of the viscosity below that of the equilibrium level (Fig．6，curve 1)．This phenomenon is traced to the presence of OH groups in the cyclic low polymers． Gel formation which is observed when [(CH3)3SiOSi(CH3)2]2O is used in small amount as chain terminating agent can be avoided when [(CH3)(C6H5)2Si]2O is used in its place(Fig．6，7)．