156 BACON. 



nitrogen. Ammonia^ as stated above, has no effect on this reagent, 

 whereas with the hypobromite solution the ammonia is also oxidized to 

 nitrogen. Consequently, by oxidizing a solution containing ammonia 

 and urea in two separate pieces of apparatus and noting the amount 

 of gas obtained after the action of each reagent, it becomes a simple 

 matter of calculation to ascertain the respective quantities of urea and 

 ammonia in the original solution. I have devised the following simple 

 form of apparatus for carrying out these determinations. (See fig. 1.) 



Two pieces of apparatus are used. A is a tube holding 10 cubic centimeters, 

 graduated in 0.1. B is a glass bulb having a capacity of 20 cubic centimeters. 

 The tube G of about 1-millimeter bore leads from the top of the latter to the 

 graduated eudiometer below. To avoid making the apparatus inconveniently 

 long I have inserted a gas chamber just below the zero mark F of the eudiom- 

 eter; this in the apparatus used with the hypobromite solution has a capacity 

 of 30 cubic centimeters and in the one used with the mercuric nitrate solution one 

 of 60 cubic centimeters. The remainder of the eudiometer E is gi-aduated in 

 0.1 up to 100 cubic centimeters. To measure the gases under the same conditions 

 of pressure, a jacket tube, O, of the form shown in the illustration is provided. 

 For the determination in alkaline solution this is filled with water, but for that 

 in acid solution glycerine, mercury, or some other liquid which does not absorb 

 carbon dioxide must be used. Details of the manipulation are as follows: 



The mercuric nitrate reagent is prepared by dissolving 10 cubic centimeters 

 of mercury in 130 cubic centimeters of strong nitric acid (specific gravity, 1.4). 

 When solution is complete, 140 cubic centimeters of water are added and, if 

 necessary, the whole is filtered. The reagent keeps well. 10 cubic centimeters of 

 this solution (preferably hot) are run into the bulb B of the proper apparatus, 

 the level of tlie liquid is broxight to the zero of the ureometer by raising or 

 lowering the apparatus, and the stop-cock H is closed. Then 5 cubic centimeters 

 of the urine (or a sufficient amount of urine to evolve a quantity of gas which 

 will fall on the graduated part of the ureometer) is placed in A, and the ureometer 

 is raised until its lower level is just below the surface of the liquid in the jacket 

 G. The urine is then run in slowly by opening the stop-cock H until only a few 

 drops remain in A. Two or three cubic centimeters of water are added to A to 

 wash in these last few drops of urine and this is also run into the bulb B, care 

 being taken, of course, not to admit any air into B. The gas evolution soon 

 begins and may be assisted by shaking the apparatus gently, ^^^len the evolution 

 of gas has ceased and the latter has attained the room temperature, the ureometer 

 is lowered until the liquid level is the same inside and outside the eudiometer tube 

 and the gas volume is read. The manipulation with the hypobromite is just the 

 same as with the mercuric nitrate solution, and the urine is added to each solution 

 within a few minutes, so that the gas volumes in both pieces of apparatus may be 

 read off at the same time, both then being under the same conditions of tempera- 

 ture and pressure, no correction is necessary for these factors, as the ammonia 

 index is a percentage coefllcient. The hypobromite reagent is conveniently pre- 

 pared by adding 1 cubic centimeter of bromine to 10 cxibic centimeters of a 20 

 per cent solution of sodium hydroxide. 



