Experiment 1: One way to separate solid and liquid insoluble in liquid is filtration, so operation A is filtration; According to the composition of the self-made deoxidizer, sulfuric acid reacts with iron to produce ferrous sulfate. Therefore, the solutes in solution C are ferrous sulfate, sulfuric acid remaining in the original mixture and sodium chloride.

Experiment 2:

(1) According to the transformation relationship between substances, the main component of solid B is carbon, which reacts with carbon at high temperature to generate iron; The solution that can react with sodium hydroxide to generate blue precipitate should be copper sulfate solution, so the colored solution C is copper sulfate, and iron can react with copper sulfate to generate copper and ferrous sulfate.

(2) Add Ba(NO3)2 solution into solution C, the reactants are copper sulfate and barium nitrate, and the products are barium sulfate and copper nitrate, and observe the balance. The barium sulfate is marked with the symbol of precipitation, so the reaction equation is: CuSO4+Ba (NO3) 2 ═ Baso4 ↓+Cu (NO3) 2;

(3) According to the above analysis, solutions C and D are copper sulfate and ferrous sulfate respectively. Because of the different colors, the way to distinguish the substances in solution C and solution D is to observe the color of the solution. FeSO4 _ 4 solution is light green and CuSO4 _ 4 solution is blue.

So, the answer is: experiment I: filtration; Ferrous sulfate, sodium chloride and sulfuric acid; Experiment Ⅱ: (1) replaces (2) CuSO4+Ba (NO3) 2 ═ Baso4 ↓+Cu (NO3) 2; (3) Observe the color of the solution. The blue color is CuSO4 solution and the light green color is FeSO4 solution.