the only way you would be able to do it is bleach the black clothes and then dye brown and hope for the best..i wouldnt even try to do it as you will just ruin your clothes..
You could use 'dyegone', its available in most haberdashery stores and even iron mongers, amongst the dylon range. it runs on a similar washing cycle to the washing machine dyes, then you die the item after. So simple.
Good luck!