Depending on your environment, to post special characters to the Title or Description fields when using AddItem / ReviseItem either use XML entities or wrap the field in a CDATA container.
Detailed Description
Assume you have the following text to insert into a Title field with an AddItem call :
Rohde & Schwarz® Spectrum Analyzer
Depending on the programming environment you're working in, you can get the special characters to show up in the final View Item page by one of two methods :
1. Use XML entity encoding for the special characters
<Title>Rohde & Schwarz® Spectrum Analyzer"</Title>
2. Wrap the characters as-is in a CDATA container :