This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
A Twenty-Five-Minute Developer. If you take the regular developing solution (eight ounces), and add enough water to make the total bulk thirty-two ounces, or just four times the bulk of the original solution, you will have five-eighths of a grain of pyro to each ounce of solution, and we have found that the factor for this developer is forty-eight. You will, therefore, see that by doubling the bulk of solution of the normal developer you will have just one-half as many grains of pyro per ounce of water, and the factor is doubled; while if you take four times the bulk of solution the grain strength of each ounce is reduced one-fourth, while the factor is four times as great. The average negative will develop in the above pyro developer when the factor is forty-eight in approximately twenty-four minutes, but if you are developing plates having varying exposures, and you are working with a developing tank, uniform development will be secured by leaving the plate in the developer for twenty-five minutes.