For qualitative testing, put a cubic centimeter of Fehling's solution into a test-tube (or if the copper and the alkaline sodio-potassium tartrate solutions are kept separate, a cubic centimeter of each), and dilute with distilled water to 5 c.c. Boil, and if, after the lapse of a couple of minutes, the solution remain unchanged, it is fit for testing. If it becomes turbid or a red sediment falls, it is spoiled, and a new solution should be obtained.[38] A cubic centimeter of the suspected urine is then measured out and added drop by drop to the solution kept hot. If there is much sugar, the first drop will throw down a yellow precipitate of suboxide of copper, which becomes rapidly red. If no reaction takes place after adding the entire cubic centimeter of urine, the addition should be continued until 4 c.c. are added, when, if, after the mixture has cooled, there be no response, it may be concluded that the urine is free from sugar. By operating with a cubic centimeter of the test-fluid and the same quantity of urine or multiples thereof, we may roughly estimate the proportion of sugar. Thus, if the cubic centimeter of undiluted urine just decolorizes the cubic centimeter of Fehling's solution, sugar is present in the proportion of one-half of 1 per cent.; or if a half cubic centimeter of the urine removes all the color, the quantity is 1 per cent. If the urine is highly charged with sugar, it may be diluted, and the degree of dilution being remembered, a rough quantitative estimation may be similarly made. [Footnote 38: Should this not be possible, a little more soda may be added and the fluid filtered, when it is again ready for use.]