Effect of Chloride: Nitrate Ratios on Total Nitrogen Determinations

1971 ◽  
Vol 54 (4) ◽  
pp. 990-990
Author(s):  
Paul R Rexroad
Keyword(s):  
Salicylic Acid ◽  
Total Nitrogen ◽  
Acid Method ◽  
Cent Nitrogen

Abstract A study is reported on the effect of various chloride: nitrate ratios on per cent nitrogen recovered. The comprehensive and Raney methods were not affected. The salicylic acid method gave decreasing recoveries with the higher ratios.

Total Nitrogen in Fertilizer: Collaborative Study

1978 ◽  
Vol 61 (2) ◽  
pp. 299-306
Author(s):  
Paul R Rexroad ◽  
Gary F Krause
Keyword(s):  
Total Nitrogen ◽  
Collaborative Study ◽  
Oxidation Catalyst ◽  
Official Method ◽  
Probability Level ◽  
Sulfate Sulfur ◽  
Powder Method ◽  
Modified Method ◽  
Accuracy And Precision ◽  
Cent Nitrogen

Abstract A modified comprehensive nitrogen method, using 0.4 g C11SO4 as catalyst, is presented. This method plus a modified Raney powder method (mercury-free) with no metallic oxidation catalyst are compared with the AOAC comprehensive nitrogen method. Results from 19 collaborating laboratories for 11 samples are evaluated. The modified Raney method gave significantly low results on 2 samples: 21-7-14 (nitric phosphates-non-sulfate sulfur) and tryptophan. The results for the average per cent nitrogen for 11 samples from the modified comprehensive nitrogen method were comparable to those from the official method at the 95 % probability level; the overall pooled standard deviations were also similar. In this collaborative study, the modified method (with copper) was equal in accuracy and precision to the official method (with mercury). The modified comprehensive nitrogen method has been adopted as official first action.

Revised Kjeldahl Total Nitrogen Method for Feeds and Premixes

1972 ◽  
Vol 55 (5) ◽  
pp. 984-985
Author(s):  
Robert Odland
Keyword(s):  
Boric Acid ◽  
Refractory Material ◽  
Total Nitrogen ◽  
Crude Protein ◽  
Analysis Time ◽  
Acid Method ◽  
Kjeldahl Method ◽  
Complete Digestion

Abstract A Kjeldahl method for equivalent crude protein in feeds was modified by using a smaller sample (0.25 g) and smaller amounts of reagents in order to reduce analysis time and cut costs. A 6% CuSO4 catalyst was used for the complete digestion of refractory material. Winkler’s boric acid method was modified by including a 90% pretitration to insure complete retention of ammonia so that only one standardized reagent is needed.

An Unforeseen Problem in the Use of Kel-Paks

1968 ◽  
Vol 51 (6) ◽  
pp. 1290-1295
Author(s):  
T C Woodis ◽  
J A Brabson ◽  
W G Burch
Keyword(s):  
Salicylic Acid ◽  
Nicotinic Acid ◽  
Organic Compounds ◽  
Total Nitrogen ◽  
Ammoniacal Nitrogen ◽  
Powder Method ◽  
Catalyst Powder ◽  
Possible Cause ◽  
Digestion Step

Abstract In Kjeldahl methods for the determination of nitrogen in fertilizers, the digestion temperature must be above 370°C to mineralize the nitrogen in refractory organic compounds such as nicotinic acid. In total nitrogen determinations by the Raney catalyst powder method, temperatures during the digestion step were investigated as a possible cause of occasional low results. Decomposition of the polyethylene envelopes of Kel-Paks in the presence of salts of metallic reductants caused rapid fluctuations and excessive rise in temperature with consequent loss of ammoniacal nitrogen. Complete Kel-Paks can be used without difficulty in methods such as 2.044 (for nitrate-free samples) or 2.045 (salicylic acid) that do not use metallic reductants, but only the contents of the Kel-Paks without the envelopes should be used when Raney catalyst or chromium powders have been used to reduce nitrates.

Analysis of Nitrogen in Fertilizers

1964 ◽  
Vol 47 (3) ◽  
pp. 433-435
Author(s):  
H A Davis
Keyword(s):  
Salicylic Acid ◽  
Nitrogen Activity ◽  
Acid Method ◽  
Methods Of Analysis ◽  
Official Methods Of Analysis

Abstract A survey of fertilizer commercial laboratories and regulatory laboratories showed that the salicylic acid method, 2.037, is still being widely used on liquid fertilizers; that many users of the reduced iron method are modifying it; and that very little use is being made of nitrogen activity methods 2.048— 2.051. It is recommended that the nitrogen activity methods be deleted from the 10th edition of Official Methods of Analysis and cited by reference only, and that attempts be made to develop one generally applicable method for nitrogen in fertilizers.

Total Nitrogen Methods—Applicable to All Fertilizer Samples

1970 ◽  
Vol 53 (3) ◽  
pp. 450-456
Author(s):  
Paul R Rexroad ◽  
Gary F Krause
Keyword(s):  
Salicylic Acid ◽  
Total Nitrogen ◽  
Collaborative Study ◽  
Official Method ◽  
Chromium Powder ◽  
Powder Method ◽  
New Methods

Abstract An extensive collaborative study was conducted to evaluate a comprehensive nitrogen method and a Raney powder method for acceptance as official methods. Twenty-nine laboratories participated; 10 samples were used and the new methods were compared to the official method, 2.045 (sulfuric-salicylic acid). Evaluation of the data and overall consideration lead to the recommendation that both new methods be adopted as official. It is recommended that 2.047 (reduced iron) and 2.049 (chromium powder) be deleted as official methods.

How Rugged Are Our Nitrogen Methods?

1965 ◽  
Vol 48 (3) ◽  
pp. 501-507
Author(s):  
W G Burgh ◽  
J A Brabson
Keyword(s):  
Salicylic Acid ◽  
Standard Deviation ◽  
Total Nitrogen ◽  
Reduction Method ◽  
Official Method ◽  
Powder Method ◽  
Catalyst Powder ◽  
Time Of Reaction

Abstract Youden’s ruggedness test was made of two official methods and four more recent methods for the determination of total nitrogen in fertilizers containing nitrates. Among the variables tested were amounts of nitrogen and reductant, effect of chloride, and time of reaction of reductant. Official method 2.039 (reduced-iron) failed the test. In order of increasing standard deviation, the five methods that passed the test were the chromous reduction method, Raney-catalyst-powder method, official method 2.037 (salicylic acid), improved reduced-iron method, and the chromiumpowder method.

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