On the Determination of Ammonia. 135 



care had always been taken to isolate fractions of the thoroughly 

 shaken and even mixed daily samples. Consequently, we had 

 no reason to believe that any of the above mentioned anomalous 

 results of the ammonia determinations were due to transferral of 

 unequal amounts of the deposited ammonio-magnesium phosphate 

 in the duplicate fractions of the urine taken. We therefore pro- 

 ceeded to test very carefully, and in many trials, the validity of 

 the second supposition stated above. 



First Series. — Is the amount of sodium carbonate (1-2 grams) 

 that is usually taken with 25 c.c. of urine in the Folin process 

 sufficient to completely liberate the ammonia from small quantities 

 of crystalline ammonio-magnesium phosphate ? 



We endeavored to answer this question directly by the follow- 

 ing special adaptation of the Folin process : Portions of pure, 

 crystalline ammonio-magnesium phosphate, in different amounts 

 between 50 and 500 milligrams inclusive, were quickly and very 

 accurately weighed on a watch glass and transferred quantitatively 

 to aerometer cylinders of the usual size, through a small dry fun- 

 nel from which the tube had been removed. All fragments ad- 

 herent to the watch glass and funnel were brushed into the cyl- 

 inders. No losses of substance could have occurred in the process. 

 In all the tests the crystalline matter was a comparatively coarse 

 powder. About 25 to 50 c.c. of water were poured into the cyl- 

 inders onto the powder, which quickly formed a loose sediment in 

 the undisturbed water. A layer of kerosene was then poured 

 over the liquid in each cylinder merely to duplicate the conditions 

 of the Folin process although no special frothing could have oc- 

 curred to require its use. Solid sodium carbonate in definite quan- 

 tities ranging between 1 and 4 grams inclusive, was then added to 

 the phosphate-water-kerosene mixture in the cylinder. The appa- 

 ratus recommended by Folin was employed for aeration. More 

 powerful pumps than those recommended by Folin were kept in 

 operation for from five to fifteen hours, so that aeration was un- 

 usually effective. In all cases aeration was continued at least five 

 hours. In the groups designated B and C (Table I) aeration was 

 conducted during a second five-hour period, or ten hours in all. 

 The aerometer cylinders were not opened between the two periods, 

 but the acid of the first period of absorption was removed and a new 



