Phosphoric Acid

["The Honjos" <fm7m-hnjy@asahi-net.or.jp>]

I got hold of a 75% solution of phosphoric acid bottle complete with 
MSDS (friend works for chemical company, plenty of samples from 
their plant).  Now I have to figure out how to use this as a 
deruster.  Do I dilute it further for use as a deruster?  If so to a 
how many % solution?  Also, any information on precautions during the 
dilution process (like which do you pour in first, water into acid or 
vice versa etc.)

Thanks for the help.

   
Makoto Honjo
Phone/Fax +81-3-3473-1848