To make 1 gal. of nickel solution, dissolve 1 lb. of double sulphate of nickel and ammonia in as much hot rain-water as will completely dissolve the crystals. Let this get cold, then filter it through calico into the vat in which it is to be worked, and make up to lgal. with clean rain water. If best nickel salt is used, it will not be necessary to add either ammonia or table salt, these being employed to correct some fault in old and poor solutions. In working nickel solutions, they become too acid when insufficient anode surface has been provided. To correct this excess acidity, add liquor ammonia in small quantities until the solution ceases to redden blue litmus paper. When a solution ceases to deposit white nickel, a very small quantity of common salt is added, say 1/6 oz. to the gallon of solution.