Hello Henry,
I am quoting directly from Atmel's AT24C512 datasheet. This is specifically only for this memory chip( and any other i2c memory devices ).
When using this chip , before this sequence is done , the chip is selected from the i2c bus using device addresses.Basically you can connect 4 such chips and the chip's address is hard coded by connecting two address pins to ground or Vcc in sequence.
And as I mentioned, I am unable to erase the chip using the sequence Atmel have advocated.
Why do you think no one should use this chip if this works ?
Would appreciate your views.

Erik thanks for your continuous views on all posts. They make excellent reading as do those of some of the other oldies. By oldies I mean those , who have worked longer in this field , no geriatric implications ;)

Thomas