A method for the determination of amino nitrogen and its applications

Abstract

It has long been known that aliphatic amines react with nitrous acid according to the equation RNH₂ + HNO₂=ROH + H₂O + N₂, and several methods have been devised for estimating amino groups by measuring the nitrogen gas evolved by this reaction. 1 None of them has been sufficiently simple or accurate to attain general use, however. The method proposed requires but little apparatus, but a few minutes for completion, and is as accurate as a Dumas or Kjeldahl determination. The reaction is carried out in a bottle with a capacity of about 35 cubic centimeters, fitted with a three hole No. 4 rubber stopper. Through the stopper pass: (1) the stem of a 10 c.c. burette; (2) the thick-walled capillary inlet from a cylindrical dropping funnel of 25 c.c. capacity; the capillary is of 2 mm. internal diameter and reaches nearly to the bottom of the bottle; (3) an outlet tube for gas. This is a capillary 25 to 30 cm. high, 1 mm. internal, 5 to 6 mm. external diameter. The lower end is flush with the bottom of the stopper, the upper end is bent in a semi-circle to meet the inlet of a gas burette. The tube has a stopcock near the middle. 2