Question: 1 is to 2 dilution?
Answer: Thus, 1 ml solution A (the solute) to 1ml solution B (the solvent) is a 1:2 dilution. Similarly, 1 ml solution A to 3 ml solution B is a 1:4 dilution, and results in 4 ml of a solution comprising one part of solution A for every three parts of solution B. Think of it as "parts per total volume".