196 THE SECRETIONS: 



separately. The substances now remaining in solution in the 

 etherealized alcohol are urea and alcohol-extract. The fluid 

 must be evaporated or distilled, and the urea determined from 

 the residue by nitric acid. The sugar separated in this manner 

 is not perfectly pure; it still contains chloride of sodium, extrac- 

 tive matters, and, in most cases, a small quantity of urea. 



From the portion precipitated from the urine (after it has been 

 reduced to a thin syrup) by alcohol of 0*85, and which consists 

 of water-extract, earthy phosphates, uric acid, and mucus, the 

 water-extract may be taken up by water, and determined after 

 evaporation. The earthy phosphates may be taken up by water 

 slightly acidulated with hydrochloric acid, from which they may 

 be precipitated by ammonia: uric acid and a little mucus remain. 

 The uric acid should be determined from a separate quantity of 

 urine, according to the method described in page 137, for by this 

 process we frequently obtain mere traces of it, and sometimes 

 no indication whatever of its presence. The determination of 

 the fixed salts in diabetic urine is of importance. Hunefeld has 

 observed that diabetic urine frequently contains more chloride 

 of sodium than the healthy fluid, a circumstance probably arising 

 from the diet which is most commonly observed during the dis- 

 ease in question. In order to determine the fixed salts, a portion 

 of urine must be evaporated, and the residue incinerated. The 

 perfect incineration of the residue is a matter of some difficulty : 

 it may be facilitated by moistening the carbonaceous residue 

 with nitric acid, and then submitting it to a red heat ; or nitric 

 acid may be added to the syrup at once, in which case a very 

 large amount of carbon is burnt off immediately upon the resi- 

 due being submitted to a red heat. The salts must be determined 

 by the method described in page 139. 



The exact determination of the solid residue of diabetic urine 

 presents certain difficulties. A very small quantity of urine 

 (from about 150 to 230 grains) should be evaporated in the 

 water-bath, and the residue spread over the evaporating basin, 

 which should then be placed under a receiver over sulphuric 

 acid, for the perfect removal of the water. The quantities of 

 sugar, urea, uric acid, &c. must be brought into relation with 

 the amount of solid residue as well as with the whole quantity 

 of urine. 



Diabetic urine may also contain a tasteless species of sugar, 



