Google has some good books that has been digitized.
You can also download them in pdf format.
The Metallurgy of Gold, By Sir Thomas Kirke Rose
http://books.google.com/books?vid=0X19knKCDiZJWGANoHe&id=4ikKAAAAIAAJ&dq=gold+dissolve&as_brr=1
The Art of Electro-metallurgy By George Gore
http://books.google.com/books?vid=0...KAAAAIAAJ&dq=Testing+Precious+Metals&as_brr=1
You can also download them in pdf format.
The Metallurgy of Gold, By Sir Thomas Kirke Rose
http://books.google.com/books?vid=0X19knKCDiZJWGANoHe&id=4ikKAAAAIAAJ&dq=gold+dissolve&as_brr=1
The Art of Electro-metallurgy By George Gore
http://books.google.com/books?vid=0...KAAAAIAAJ&dq=Testing+Precious+Metals&as_brr=1