(1) Esbach's Method.--The urine must be clear, of acid reaction, and not concentrated. Always filter before testing, and, if necessary, add acetic acid and dilute with water. Esbach's tube (Fig. 23) is essentially a test-tube with a mark _U_ near the middle, a mark _R_ near the top, and graduations ½, 1, 2, 3, etc., near the bottom. Fill the tube to the mark _U_ with urine and to the mark _R_ with the reagent. Close with a rubber stopper, invert slowly several times, and set aside in a cool place. At the end of twenty-four hours read off the height of the precipitate. This gives the amount of albumin in _grams per liter, and must be divided by 10 to obtain the percentage_. [Illustration: FIG. 23.--Esbach's albuminometer, improved form.] _Esbach's reagent_ consists of picric acid, 1 gm., citric acid, 2 gm., and distilled water, to make 100 c.c. (2) Purdy's Centrifugal Method.--This is detailed in the accompanying table. The percentage by weight is approximately one-fiftieth of the bulk percentage. {75} PURDY'S QUANTITATIVE METHOD FOR ALBUMIN IN URINE (CENTRIFUGAL) _Table showing the relation between the volumetric and gravimetric percentage of albumin obtained by means of the centrifuge with radius of six and three-quarter inches; rate of speed, 1500 revolutions per minute; time, three minutes._ VOLUMETRIC | PERCENTAGE BY | GRAINS PER PERCENTAGE BY | WEIGHT OF | FLUIDOUNCE CENTRIFUGE. | DRY ALBUMIN. | DRY ALBUMIN. --------------+---------------+------------- ¼ | 0.005 | 0.025 ½ | 0.01 | 0.05 ¾ | 0.016 | 0.075 1 | 0.021 | 0.1 1¼ | 0.026 | 0.125 1½ | 0.031 | 0.15 1¾ | 0.036 | 0.175 2 | 0.042 | 0.2 2¼ | 0.047 | 0.225 2½ | 0.052 | 0.25 2¾ | 0.057 | 0.275 3 | 0.063 | 0.3 3¼ | 0.068 | 0.325 3½ | 0.073 | 0.35 3¾ | 0.078 | 0.375 4 | 0.083 | 0.4 4¼ | 0.089 | 0.425 4½ | 0.094 | 0.45 4¾ | 0.099 | 0.475 5 | 0.104 | 0.5 5½ | 0.111 | 0.55 6 | 0.125 | 0.6 6½ | 0.135 | 0.65 7 | 0.146 | 0.7 7½ | 0.156 | 0.75 8 | 0.167 | 0.8 8½ | 0.177 | 0.85 9 | 0.187 | 0.9 9½ | 0.198 | 0.95 10 | 0.208 | 1.0 10½ | 0.219 | 1.05 11 | 0.229 | 1.1 11½ | 0.24 | 1.15 12 | 0.25 | 1.2