URINE. 195 



of grape-sugar may be detected in a fluid by the addition of a 

 solution of sulphate of copper and of caustic potash. 1 On heating 

 the mixture we do not obtain a black precipitate of oxide of 

 copper, but the fluid becomes turbid, and a more or less consi- 

 derable yellow, or yellowish-brown precipitate of reduced sub- 

 oxide of copper is thrown down. According to the statements 

 of Trommer, this method is particularly applicable to the de- 

 tection of very minute quantities of diabetic sugar in urine; but 

 since the ammonia-salts, the urea, and nitrogenous extractive 

 matters, when heated with caustic potash, develope free ammonia, 

 which impedes the action of the test, it is better to proceed in 

 the following manner. The urine must be evaporated and the 

 syrupy residue treated with anhydrous alcohol. Dry carbonate 

 of potash must be added to this solution, and the mixture well 

 shaken. The carbonate of potash dissolves and forms a layer 

 beneath the alcohol. Upon the addition of some dissolved sul- 

 phate of copper, and the application of heat, there is produced 

 in the lower portion of the fluid, a yellow or yellowish-brown 

 turbidity, if sugar is present. Trommer states that this method 

 is equally applicable for the detection of sugar in the blood. 



The quantitative determination of sugar in urine is not very 

 easy: I proceed in the following manner. A weighed quantity 

 of urine is evaporated on the water-bath to the consistence of 

 a thin syrup, and the residue treated with alcohol of O85, 

 which precipitates the mucus, the salts insoluble in spirit, the 

 water-extract, uric acid, &c. The spirituous solution is then 

 evaporated to the consistence of a thick syrup, and anhydrous 

 alcohol added, which precipitates the greater part of the sugar 

 in the form of a yellowish-white magma. On pouring off the 

 supernatant yellow alcohol, and repeatedly treating the magma 

 with anhydrous alcohol, it gradually assumes a tough pasty 

 form : it must then be warmed for some time on the water-bath, 

 until all the alcohol is expelled, and be subsequently placed 

 under a receiver over sulphuric acid, to dry. Ether is then 

 added to the alcohol, in about the proportion of one volume of 

 the former to two of the latter, by which an additional quantity 

 of sugar is precipitated, whose weight must be determined 



1 See Vol. I, p. 68. Additional observations on the application of this test will be 

 found in the remarks on the urine in diabetes. 



