166 HEALTHY URINE. 



B. Distillation. Into the Erlenmeyer receiving flask (C) 



N 

 measure from a burette 80 cc of - (decinormal) sulphuric 



acid. This is in excess of what will be required to combine 

 with all the ammonia yielded. Pour this in through the side 

 tube (D) to wet the glass beads as a precaution to catch any 

 ammonia that might escape the sulphuric acid. There is little 

 danger of this, however. Add a few drops of methyl orange, 

 which would indicate the neutralisation of all the acid when 



N 

 more H 2 SO 4 would have to be added. The delivery tube 



(E) must dip a little below the fluid in (C) during the first 

 part of the operation, when most of the ammonia comes over. 

 The great affinity of the sulphuric acid for ammonia renders 

 loss unlikely. Check violent bumping in (A) by reducing the 

 gas flame. The bulb (E) saves the contents of (C) from 

 regurgitating into (A). Should the fluid regurgitate into (E) 

 and ammonia be present, it will turn the methyl orange yellow 

 and serve as a useful indication that there is still ammonia 

 coming off. (C) must be kept cool by changing the water 

 from time to time. As soon as (A) begins to bump vigorously 

 the ammonia may be assumed to have been all expelled 

 (twenty minutes). 



The flask (A) should now be detached. 



(C) Titration. Cool (C), wash out (D) into (C) with 10 cc of 

 distilled water, and then titrate the uncombined acid in the 



N IS" 



latter with ~ NaOH. The - NaOH is run in from a 



burette until the methyl orange turns yellow, the last quantity 

 required being added drop by drop. 



Calculation : 



l cc jz- NaOH - 1 M - ^H 2 SO 4 - 



