After the readings have been recorded add the results obtained by Nesslerizing each portion of the entire distillate. If 500 cc. of the sample is distilled this sum, expressed in cubic centimeters and multiplied by 0.02, will give the number of parts per million of ammonia nitrogen in the sample. If x cc. of sample is used multiply the sum of the readings by 10/x. If the ammonia is known to be high the distillate may be collected in 200 cc. flasks and an aliquot part Nesslerized. COMPARISON WITH PERMANENT STANDARDS.[62][65] _Reagents._—Platinum solution. Dissolve 2.00 grams of potassium platinic chloride (PtCl_{4}.2KCl) in a small amount of distilled water, add 100 cc. of strong hydrochloric acid, and dilute to 1 liter. Cobalt solution. Dissolve 12 grams of cobaltous chloride (CoCl_{2}.6H_{2}O) in distilled water, add 100 cc. of strong hydrochloric acid, and dilute to 1 liter. Prepare standards by putting various amounts of these two solutions into Nessler tubes and diluting to the 50 cc. mark with distilled water as indicated in Table 5. These standards may be kept for several months if protected from dust. Table 5.—PREPARATION OF PERMANENT STANDARDS FOR THE DETERMINATION OF AMMONIA. ───────────────────────┬───────────────────────┬─────────────────────── Value in standard │ Solution of platinum. │ Solution of cobalt. ammonium chloride. │ │ ───────────────────────┼───────────────────────┼─────────────────────── _cc._│ _cc._│ _cc._ 0.0│ 1.2│ 0.0 .1│ 1.8│ .0 .2│ 2.8│ .0 .4│ 4.7│ .1 .7│ 5.9│ .2 │ │ 1.0│ 7.7│ .5 1.4│ 9.9│ 1.1 1.7│ 11.4│ 1.7 2.0│ 12.7│ 2.2 2.5│ 15.0│ 3.3 │ │ 3.0│ 17.3│ 4.5 3.5│ 19.0│ 5.7 4.0│ 19.7│ 7.1 4.5│ 19.9│ 8.7 5.0│ 20.0│ 10.4 │ │ 6.0│ 20.0│ 15.0 7.0│ 20.0│ 22.0