Escape characters in sed stream

I'm trying to use sed on the linux command line, and am running into an issue with special characters.

I'd like to replace "~" with "E;" in the target file (without quotations). So far, using this command:

sed {s/\~/\&#7E\;/g}

on this data:

blah~blah

produces:

blah~#7E;blah

Close, but no cigar.

Thanks in advance for any insight you can provide.