What color would Nickel ions burn (say in a compound of NiSO4)? Green? If you searched this on the web please post the link for a reference I can use.
I don't have a reference. In fact, it is not listed in any text book I own and it is not listed on
any of the sites I found on the web. What I wrote to you earlier is the result of personal experience; I performed many flame tests during my career as a chemist. The part about not being reliable is also from personal experience. I have a book at home that lists ALL the lines from ALL the elements. Nickel has no strong lines above about 350 nm and the eye is not sensitive to that wavelength, anyway. The most comprehensive flame test site I found on the web is below but that doesn't list Ni either. In fact, almost all flame tests are carried out with nichrome wire (an alloy of Ni and Cr) or Pt. Given the cost of Pt, you can guess which wire is used the most often. The chloride gave me better results than other salts. I don't have specific recollections of using NiSO4.
For some reason I can't post the site on this round. I will send this, then another containing the site. I'm sorry I can't be of more help.
http://chemistry.about.com/library/weekly/aa110401a.htm
why does a clean new nichrome wire produce an orange light when heated in a flame, even though there is no test compound on the wire