Dissolution of nickel in non-oxidizing aqueous acid solutions

A process for making a final aqueous acidic liquid that contains dissolved nickel cations, said process comprising the following operations:

• (I) providing a first mass of a nickeliferous solid reagent;
• (II) providing, separately from said first mass, a second mass of a precursor aqueous acidic liquid reagent that comprises the following components:
• (A) water;
• (B) molecules of at least one non-oxidizing acid;
• and, optionally, one or both of the following components:
• (C) an oxidizing agent component that contains molecules of at least one oxidizing agent that is distinct from said non-oxidizing acid;
• and
• (D) dissolved nickel cations;
• and
• (III) effecting contact between said first mass and said second mass under such conditions of temperature and relative motion between said two masses as will result in spontaneous chemical reaction between them, said spontaneous chemical reaction converting at least 80 percent of the elemental nickel present in said first mass to dissolved nickel cations in a final aqueous acidic liquid that includes some of the molecules of non-oxidizing acid originally present in said second mass within a time interval, beginning with the first contact between said first and second masses, that is not more than 24 hours.