10 METHODS OF ANALYSIS. 



200 cc of water and 5 grams or more of magnesium oxid free of carbon dioxid. 

 Then connect the flask with a condenser and distil 100 cc of the liquid into stand- 

 ard acid. Titrate the residual acid as in the Kjeldahl method, page 6. 



(g) ULSCH METHOD, MODIFIED BY STREET. OFFICIAL. 

 (Applicable to all nitric and ammoniacal nitrogen determinations.) 



Place 1 gram of the sample in a half-liter flask. Add about 30 cc of water 

 and 2 to 3 grams of reduced iron, and after standing sufficiently long to insure 

 solution of the soluble nitrates and ammonia salts add 10 cc of a mixture of 

 strong sulphuric acid with an equal volume of water; shake thoroughly and 

 allow to stand for a short time until the violence of the reaction has moder- 

 ated. Place a long-stemmed funnel in the neck of the flask to prevent mechan- 

 ical loss. Heat the solution slowly, boiling it for five minutes, and cool. Add 

 about 100 cc of water, a little paraffin, and from 7 to 10 grams of magnesium 

 oxid, free or nearly free from carbonates. Connect with a condenser, such as 

 is used in the Kjeldahl method, and boil the mixture for forty minutes, nearly 

 to dryness; collect the ammonia in a known amount of standard acid, and 

 titrate in the usual manner. The nitrogen obtained represents the nitrates, 

 plus the ammonia salts, contained in the sample. 



In the analysis of nitrate salts proceed as above, except that 25 cc of the 

 nitrate solution, equivalent to 0.25 gram of sample, are employed with 5 grams 

 of reduced iron. After boiling add 75 cc of water and an excess of sodium 

 hydrate and complete the determination as above. 



(h) ZINC-IRON METHOD. OFFICIAL. 

 (Applicable to the determination of nitric and ammoniacal nitrogen.) 



Dissolve 10 grams of the sample in 500 cc of water. Of this solution place 

 25 cc, corresponding to one-half gram, in a distillation flask of about 400 cc 

 capacity, add 120 cc of water, also about 5 grams of well-washed and dried zinc 

 dust, and an equal weight of reduced iron. To the solution add 80 cc of sodium 

 hydrate of 32 B. Then connect the flask with the condensing apparatus and 

 conduct the distillation synchronously with the reduction, collecting the ammonia 

 in carefully standardized acid. Continue the distillation for one or two hours, 

 or until 100 cc have been distilled and titrate the resulting distillate as in the 

 Kjeldahl method, page 6. 



(i) NEUTRAL-PERMANGANATE METHOD. PROVISIONAL. 

 (For the-determination of available organic nitrogen.) 



Into a 300 cc low-form Griffin beaker weigh 2 grams of the sample if from a 

 mixed fertilizer; if from concentrated material, use a quantity containing 

 approximately 0.075 gram of nitrogen (sample containing material that has been 

 treated with acid should be washed on a 9 cm S. S. No. 595 filter to 200 cc and 

 transferred, filter and all, to a beaker). Digest this with 125 cc of perman- 

 ganate of potash solution (16 grams of pure potassium permanganate to 1,000 

 cc water) in a steam or hot-water bath for thirty minutes. Have the beaker let 

 down well into the steam or hot water and keep closed with cover glass, stir- 

 ring twice at intervals of ten minutes with a glass rod. At the expiration of 

 the time remove from bath, add 100 cc of cold water, and filter through a 

 heavy 15 cm folded filter. Wash with cold water, small quantities at a time, 

 till total filtrate amounts to 400 cc. Dry and determine nitrogen in residue by 

 Kjeldahl method. 



