ANALYSIS OF URINE. fCH. XIII. 



reaction with litmus. If not alkaline add more of the calcium 

 hydroxide. Dilute to the mark and allow it to stand for at least 

 .30 minutes. Filter through a dry folded paper into a dry flask. 

 This will remove up to 8 per cent, of glucose. If more than this is 

 present, the urine must be diluted to bring it down to 8 per cent. 

 If glucose is present in the nitrate a yellow (not white) precipitate 

 will appear if a little of it is boiled in a test-tube. 



(ii.) Connect up a 500 cc. Erlenmeyer flask with a straight 

 reflux condenser, as shewn on p. 72. Into the flask measure 25 cc. 

 of the urine filtrate, 100 cc. of water, 10 cc. of the 17 N. sulphuric 

 acid and 35 cc. of the mercuric sulphate solution. Connect up to the 

 condenser and heat to boiling over a free flame (not over a sand 

 bath) . When boiling has begun add 5 cc. of the dichromate solution, 

 running this down the condenser tube. Allow the mixture to boil 

 gently for ij hours. 



(iii.) Cool the solution and filter off the precipitate, using a 

 weighed Gooch crucible (see notes to Ex. 410). Wash out the flask 

 with cold water, of which about 200 cc. in all should be used. Dry 

 the crucible in an hot-air oven at 110 C. for an hour. Allow the 

 crucible to cool down to air temperature and weigh again. 



Calculation. If 25 cc. of the filtrate (representing 2-5 cc. of the urine) are 

 used, i gram, of precipitate corresponds to 2-48 grams, of total acetone bodies 

 per 100 cc. in terms of acetone. This is on the assumption that the molecular 

 proportion of the acetone bodies in the form of j8-oxy-butyric acid is 75 per 

 cent., the usual figure. 



409. /3-oxy-butyric acid. The acetone and aceto-acetic acid 

 are first boiled off and then the estimation conducted as before. 

 Measure 25 cc. of the filtrate into the open flask, add 100 cc. of 

 water and 2 cc. of the sulphuric acid. Boil gently for 10 minutes 

 with a free flame. Cool and transfer to a measuring cylinder and 

 note the volume. Return it to the flask and add water to the cylinder 

 to make a total volume of 127 cc. Add 8 cc. of the sulphuric acid 

 and 35 cc. of the mercuric sulphate. Connect up to the condenser 

 and boil. When boiling add 5 cc. of the dichromate and allow the 

 mixture to boil gently for I J hours. Then proceed as in Ex. 408 (iii) . 



Calculation, i gram, of precipitate corresponds to 2-64 grams, of -oxy- 

 butyric acid per 100 cc., reckoned as acetone : to convert to /3-oxy-butyric 



104 

 acid multiply by - = 1-793. 



