PostgreSQL selecting empty fields of integer type

I have a table and I need to select all the rows with an empty value for the fk_fc_id field (as a prelude to deleting them),

Column     |            Type             |                         Modifiers
---------------+-----------------------------+------------------------------------------------------------
 di_timestamp  | timestamp without time zone |
 di_item_value | character varying(10)       |
 fk_fc_id      | integer                     |
 di_id         | integer                     | not null default nextval('data_item_di_id_seq1'::regclass)

However this doesn't work,

# select fk_fc_id,di_timestamp,di_item_value from data_item where fk_fc_id="";
ERROR:  zero-length delimited identifier at or near """"
LINE 1: ...di_timestamp,di_item_value from data_item where fk_fc_id="";
                                                                    ^

Trying Null doesn't work either.

If anyone has any suggestions on how to sort this, I would be very grateful.

This is not really database administration related, nor is it really about PostgreSQL, but as @foibs answered, you should have a look at IS NULL:

SELECT fk_fc_id,
        di_timestamp,
        di_item_value  
 FROM data_item  
 WHERE fk_fc_id IS NULL

StackExchange Database Administrators Q#54343, answer score: 29