158 THE URINE. 



346. To 5 cubic centimeters NaOH add a drop of 

 bromin, and after this has dissolved a few crystals of urea. 

 Explain the result. 



347. PREPARATION OF SODIUM HYPOBROMITE. In a 

 thin glass flask or beaker containing 20 cubic centimeters 

 of water dissolve 8 grammes of sodium hydrate. Cool, 

 and from a dropping pipette or funnel add slowly 2 cubic 

 centimeters of bromin, stirring or shaking meanwhile. 

 Handle the bromin under a hood or in a draft of air to 

 avoid the vapors, which are especially irritating to the 

 eyes and lungs. As the bromin-gas is heavy, it should be 

 held below the level of the face while pouring, rather than 

 above. 



348. Determine the percentage of urea in urine by 

 the use of Doremus's ureometer. First fill the tube with 

 the hypobromite solution and invert it, having no more 

 of the liquid in the bulb than is necessary to keep the tube 

 full. Fill the pipette exactly to the mark with urine, in- 

 sert the lower end into the ureometer, and slowly and 

 steadily force the urine out by compressing the rubber 

 bulb. The urine, being the lighter liquid, rises in the ureo- 

 meter and the urea is immediately decomposed. The car- 

 bon dioxid is dissolved in the solution and only the nitro- 

 gen is collected. No gas-bubbles should be allowed to 

 escape into the ureometer-bulb or back into the pipette, 

 thereby causing a loss. When the foam has disappeared, 

 read off the quantity of gas and calculate the percentage 

 of urea. Duplicate tests should not differ more than 0.1 

 per cent. If the volume of urine in twenty-four hours is 

 known, calculate the weight of urea excreted in that time. 



349. Determine the amount of urea in urine by ap- 

 paratus, page 154. Fill B nearly full of water. Into C 

 by a pipette put exactly 2 cubic centimeters of urine. Out- 



