───────────────────────┴───────────────────────┴─────────────────────── 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. MODIFICATION FOR SEWAGE. Ammonia nitrogen and albuminoid nitrogen in sewages, soils, and other materials of high nitrogen content may be satisfactorily determined by diluting the sample with ammonia-free distilled water and proceeding as described in the preceding sections, but it is permissible to distill with steam.[40] _Procedure._—Use a 200 cc. long-necked Kjeldahl flask connected with a condenser so that the distillate may drop from the condenser tube directly into a Nessler tube or a flask. Connect the Kjeldahl flask with a steam generator by a tube reaching almost to the bottom of the flask. After the apparatus is freed from ammonia put the sample to be tested into the flask. Use 10 to 100 cc. of the sample according to its ammonia content. Pass ammonia-free steam through the liquid in the Kjeldahl flask and collect the distillate in the usual way. It is usually convenient to collect the distillate in a 200 cc. flask and to take an aliquot part of it for Nesslerization. Compare with standards and calculate the nitrogen content in the usual manner. This method has the advantage, when the sample is treated with an alkaline solution of potassium permanganate, of avoiding bumping, permitting the assay of solid matter, and yielding the ammonia more rapidly than by the ordinary process of distillation. DETERMINATION BY DIRECT NESSLERIZATION.[21][75] _Reagents._— 1. Ten per cent solution of copper sulfate (CuSO_{4}.5H_{2}O). 2. Ten per cent solution of lead acetate (Pb(C_{2}H_{3}O_{2})_{2}.3H_{2}O). 3. Fifty per cent solution of sodium hydroxide (NaOH) or potassium hydroxide (KOH).