I know that by 'spice' you probably mean it as in a condiment, but if we stretch our definitions a bit to a more... Dune-like conception of 'spice', here are some of my older answers on the opium trade that might be enlightening on the nature of Western trade with China in the 19th century:

• Qing legalisation of opium
• The extent of opium use in 1838

And a recent Tuesday Trivia piece I wrote (see the last two paragraphs): here