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 (PtCl4.2KCl) 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 (CoCl2.6H2O) 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 ammonium chloride. | Solution of platinum. | Solution of cobalt. |
| 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 |
The amounts in Table 5 are approximate, and the actual amount necessary will differ with the character of the Nessler solution, the color sensitiveness of the analyst’s eye, and other conditions. The final test of the standard is best obtained by comparing it with Nesslerized standards and modifying the tint accordingly. Such comparison should be made for each new batch of Nessler solution and should be checked by each analyst.
Procedure.—In comparison with permanent standards, Nesslerize the distillates in the manner above described and compare the resulting colors at the end of about 10 minutes with the permanent standards. The method of calculating results is precisely the same as with the ammonia standards.