Which is correct, sulphate or sulfate?

Both spellings are correct; "sulfate" is American English, while "sulphate" is British English.

This is purely a regional spelling difference with no chemical distinction. American scientific literature uses "sulfate," while British, Australian, and Indian English prefer "sulphate." International chemistry organizations like IUPAC accept both spellings. The compound CuSO4 remains identical regardless of which spelling you choose.

Important Notes:

• Sulfate = American English spelling
• Sulphate = British English spelling
• Both refer to the same SO4²⁻ ion
• Choose based on your audience or regional standards
• No difference in chemical meaning