I have broken the end of tap in a phosphor bronze casting, and I have heard a rumour that a couple of drop of sulphuric acid will dissolve the tap. Is this correct? And if so where can I buy / get a small quantity. I have been offered 25 litres, but cannot get anything smaller. MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.