[Ethereum] Converting oraclize result from string to address

I am trying to set up a contract that gets an ethereum address from a json file using oraclize, and in turn i'd like to send ether to that address.

function __callback(bytes32 myid, address result) {
  if (msg.sender != oraclize_cbAddress()) throw;
  _address = result;
  if (!_address.send(_withdrawAmount)) throw;
  Withdraw(now, _withdrawAmount, this, _owner);
 }

function withdraw(uint value) {
  _withdrawAmount = value;
  oraclize_query("URL", url);
}

And here is the json

{
  "address" : "0xf519f8bf364fb6bf0185f0bacf19fb8e5c3f134a"
}

I havent been able to send ether in the __callback function and i am not sure how to resolve it.

I am guessing it is because it returns a string, so in the __callback function the type of 'result' would be a string. But how would i convert a string to an address i'd be able to send ether to?

EDIT: In addition to Xavier's answer, I found that I can't send transactions from within the callback function. So i added an executeWithdrawal function that the user would have to call to execute the transaction once the callback has been made from oraclize.