Enjoy fun and easy, but does not always coincide with a picture of both the color of the squares, when you check the result. If the upper tee to a tee, the lower coincides with the fact that in the table the right and left or vice versa. Understanding acidity get, of course, possible, but the accuracy of such measurements is important for me because I had read on the Internet the following information: "When a person is born, he has the pH value (pH) of all fluids and exhaled air is - 7.41; When a man dies, he pH value of 5.41. That is, on the whole of human life is given to him only 2 pH units. "