About OutStream to generate xml tags....

To generate xml tags using OutStream i am writing code as follows in Codeunit.

OutStream.WRITETEXT(’<soap**:**Envelope>’);

When i run the codeUnit to generate the xmldocument i am Not getting any thing. But when i write the code like

OutStream.WRITETEXT(’’); (without ’ : ’ ) i can generate xml document.

So Plz anybody help me to get tag like <soap**:**Envelope> , and also is there any particular rules (like special Charaecters are not a allowed to generate xml tags) are there to use OutStream to Generate xml tags.

I am using NAV 2009R2