Where can i buy Ferrofluid in Barcelona?

Answer 1

I don't have a good answer for you but:

1. There are places that sell ferrofluid on-line. Whether any of these are in Europe or whether the American vendors would ship to Europe, I can't say.
http://www.amazingmagnets.com/index.asp?PageAction=VIEWPROD&ProdID=108
http://www.ferrotec.com/company/

(Ferrotec has an office in Spain)

2. If you are looking for ferrofluids for amateur experiments, etc., then there are a number of sites that tell you how to make your own.

There are various techniques, from the simple mechanical to the use of caustic chemistry,

http://mrsec.wisc.edu/Edetc/nanolab/ffexp/index.html

and the results are not going to be quite as good, but they may be good enough for your purposes.