554 THE SECRETIONS. 



a cupric salt, in order to reduce the whole of the copper to 

 the condition of red cuprous oxide. 



In order to determine the quantity of sugar by the last 

 method, which is known as that of Fehling, we require to 

 prepare a standard solution in the following manner : 34.65 

 grammes of pure and well crystallized copper sulphate are 

 dissolved in about 160 cubic centimetres of water, and 173 

 grammes of Rochelle salts (tartrate of potash and soda) are 

 dissolved in about 600 cubic centimetres of solution of caustic 

 soda, having a specific gravity of 1120. Tl?e solution of sul- 

 phate of copper is added gradually to the alkaline solution of 

 Rodielle salts, the fluid being continually stirred. A deep 

 blue solution is thus obtained, which is diluted with distilled 

 .water to the volume of one litre. Ten cubic centimetres of 

 this solution are reduced by 0.05 gramme of diabetic sugar. 



The following is the process which has to be followed in 

 determining the quantity of sugar in urine: 



The urine to be examined is diluted to a known extent; 

 thus in the case of a diabetic urine, having a specific gravity 

 of 1040, 100 cubic centimetres are diluted with distilled water 

 to the volume of 1000 cubic centimetres. 



Ten cubic centimetres of the standard copper solution are 

 then accurately measured out and poured into a porcelain 

 capsule. Forty cubic centimetres of distilled water are added, 

 and the solution in the capsule boiled. 



The previously diluted urine is then allowed to flow in from 

 a burette ; after a few cubic centimetres have been added, the 

 fluid in the capsule is briskly boiled, and then the application 

 of heat discontinued for a few seconds. 



The solution, which, after the saccharine fluid has been 

 boHed with it, assumes a red color, deposits a red sediment of 

 cuprous oxide, whilst the supernatant fluid retains a more or 

 less blue color, in consequence of a portion of the copper 

 remaining in solution. 



Successive portions of the diluted urine are then added, and 

 the fluid boiled after each addition. As the operation proceeds, 

 the addition of the diluted urine is performed with great care, 

 only a few drops being poured in at a time. A point is at last 



i died when the bottom of the capsule is coated with a de- 

 posit of red cuprous oxide^Ssnd when, on tilting the capsule 

 so as to bring the fluid, which it contains, over the clean white 

 sides, no tint of blue is perceived. 



The number of cubic centimetres of sugar solution added is 

 then rend off and marked. It is advisable, however, to pur- 

 ;he operation one step further. A few more drops of 

 diluted urine are added to the contents of the basin, which 

 ;nv a<rain boiled, and if necessary, the addition is repeated 

 until the boiled fluid becomes faintly opaque and of a yellowish 



