This chapter shall apply to every not for profit corporation to which Title 24 RCW applies, and which is a "private foundation" as defined in section 509 of the Internal Revenue Code of 1954, and which has been or shall be incorporated under the laws of the state of Washington after December 31, 1969. As to any such corporation so incorporated before January 1, 1970, this chapter shall apply only for its federal taxable years beginning after December 31, 1971.