This is a book that documents all correspondence on the Chinese legation. It seems to cover correspondence between the US and China as well as the UK and China.

files.me.com/pidgeproductions/ylaljn

There is also a second publication of Correspondence between Great Britain and China (not sure if it’s all duplicates of the above).

files.me.com/pidgeproductions/bst3xw

And a document from the Library of Congress on the Chinese Embassy

files.me.com/pidgeproductions/h102xt