288 NON-NITROGENOUS NEUTRAL BODIES. 



measures may prepare Fehling's test solution as follows : Dissolve 

 69 grains of crystallised sulphate of copper in five times their weight 

 of distilled water, and add to it, first, a concentrated solution of 

 268 grains of tartrate of potash, and then a solution of 80 grains of 

 hydrate of soda in one ounce of distilled water. Put the solution 

 into an alkalimeter tube, and add distilled water so as to make 

 1000 grain-measures of the liquor. This solution will be nearly 

 double the strength of that made according to the above directions, 

 and every 100 grain-measures of it will be equivalent to 1 grain 

 of grape sugar. [G. E. D.] 



By SoleiFs polarising apparatus the quantity of sugar may be 

 determined with more rapidity than by the preceding method, 

 and with equal accuracy. Many precautions are, however, requi- 

 site in its application, as has been especially shown by Dubrunfaut,* 

 Clerget,t and Lespiau.J We refer, therefore, to their communi- 

 cations on this subject ; especially as SoleiPs apparatus, in so far 

 as its application to saccharine urine is concerned, is still deficient 

 in many respects. 



Fermentation was formerly employed to determine the quan- 

 tity of sugar in fluids, the carbonic acid being determined, and the 

 quantity of sugar calculated from it. This mode of determination 

 is deficient in accuracy, in the first place, because all animal 

 fluids, and especially the urine, contain free carbonic acid, and, 

 secondly, because other constituents of the urine are simultaneously 

 decomposed during the process of fermentation, and also yield 

 carbonic acid. This method serves, however, very well for approxi- 

 mate and comparative determinations, if we allow a weighed 

 quantity of diabetic urine to ferment at 37 in Fresenius'sf alka- 

 limetrical apparatus, and, as in alkalimetrical processes, determine 

 the carbonic acid by the loss of weight. 



This is the best means of determining the amount of sugar for 

 ordinary medical purposes, Fehling's method being applicable 

 rather to technology than to clinical medicine. If the apparatus 

 be allowed to stand for about 48 hours at the above-mentioned 

 temperature, all the sugar will have been converted into spirit ; if 

 we even omit to remove the carbonic acid by drawing a little air 

 through the apparatus, previously to weighing, we shall still obtain 

 results at all events sufficiently accurate for purposes of 

 comparison. 



* Ann. d. Chim. et de Phys. 3 Ser. T. 18, p. 101. 



t Compt. rend. T. 22, p. 200, and pp. 256-260. 



t Ibid. T. 26, p. 306. 



Neue Verfahrungsweisen zur Prufung der Soda, &c. Heidelb. 1843. 



