LXXXIII.—Kjeldahl's method for the determination of nitrogen

Abstract

At the time these experiments were undertaken, the author was unaware of the work of Dafert (Landwirth-~ersuchs., 34), and of the later work of Arnold and Wedermeyer (Zeit. A n a l. Chem., 31, 525) in the same direction. On the whole, the experience of these authors is similar in most direct,ions to that now recorded, although the majority of' the representalive compounds selected for their experiments were different from those used by the present author.

Selenium as a catalyst in the Kjeldahl method as applied to soil and grass analysis

“…In 1889 Gunning (6) claimed that it was not a catalyst which was required, but some means of maintaining the strength of the acid, and he recommended for this purpose the use of potassium sulphate, which also raised the boiling point of the mixture. Although he considered that his modification made unnecessary the addition of a catalyst or potassium permanganate, the practice of adding catalysts soon arose, for in 1895 Dyer (7) published a paper in which he described a method employing both mercury and potassium sulphate to accelerate digestion. Nevertheless, the value of Gunning's modification was not immediately recognised, and for many years the original Kjeldahl method or the KjeldahlGunning method was used according to the prejudice of the analyst.…”

Total Protein Methods and Their Potential Utility to Reduce the Risk of Food Protein Adulteration

“…Background Kjeldahl reported his wet chemistry method in 1883 as a new means of indirectly quantifying total (crude) food protein by measuring the total organic nitrogen content (Kjeldahl 1883). The method rapidly gained acceptance because it overcame many of the limitations—notably accuracy, simplicity, and speed—of nitrogen determination by combustion analysis (Dyer 1895; Szabadváry 1966). Since its inception the Kjeldahl method has been the most widely accepted method for total protein determinations in feeds, foods, and food ingredients.…”

The Effects on the Cardiovascular System of Fluids Administered Intravenously in Man. I. Studies of the Amount and Duration of Changes in Blood Volume

“…Protein concentrations of sera were measured in duplicate by the macro-Kjeldahl method (25), nonprotein nitrogen being subtracted from the total nitrogen. The hematocrit readings of heparinized blood samples were made as described by Rourke and Ernstene (26) and in duplicate.…”