BY

The use of the microdiffusion unit for the deter-mination of blood urea has been described by Conway and O'Malley (1942). Recovery of urea added to blood when estin;ated by this method is precisely quantitative as compared with a 98 to 99 % recovery given by the aeration method (Kay and Sheehan, 1934). The method has been found very useful for routine laboratory determinations, especially when dealing with large numbers of samples. Conway (1939a) has also described a method for determining total nitrogen, using the diffusion cell to estimate the ammonia after digestion by the usual Kjeldahl technique. A modification of the method so that the same reagents as those use