The Determination of Ammonia Nitrogen in Steer’s Urine

In connection with certain metabolism experiments now in progress in this Institute, the determination of the nitrogen present in the urine of a steer as ammonium compounds and ammonia has become of considerable importance. Recurring peculiarities in the results obtained in some earlier work involving ammonia determinations led to the belief that the chloroform used in the urine as a preservative was inefficient, since in every case urine so treated showed an increase in the ammonia from day to day. Therefore it was planned to test out several preservatives especially as to their ability to prevent the breaking up of nitrogenous substances. Numerous attempts have been made in this laboratory to differentiate between the nitrogen present in steer’s urine as ammonium compounds and that present as ammonia. Braman,’ however, has shown that practically all the ammonia nitrogen present is in the form of ammonium carbonate with possibly small quantities of ammonia. Simple aeration causes decomposition of ammonium carbonate, and while the addition of sodium chloride prevents a complete breaking up of the carbonate it has been found impossible to obtain a satisfactory separation. The total quantity of urine excreted by a steer at one voiding was collected, immediately divided into four approximately equal parts, and preserved at about 10°C. during the period covered by analysis. The four samples were treated as follows: