18}$.] discharged in Diabetes Mellitus. SI 



_ ^ ^ J- t r In the course of a few minutes,. 



Extract from 2 measures diabetic) ^ . precipitation of 

 to 1 natural urme. i scales. 



^ ^ , 1. 1 . CNo immediate precipitation; 



Do. from 4 measures diabetic to \ ^^^^enced in half an 



1 natural urme. ^ 1^^,^,^ j gradually increased. 



Do. from 6 diabetic to 1 natural V^p^'^J^'P^","! ^buTCf till 



(_ after 24 hours. 

 Do. from 8 diabetic to 1 natural C 

 urme. ^ 



From these experiments, it may be inferred, that urea can no 

 longer be made apparent by nitric acid in the extract, from any 

 mixture of diabetic and natural urine, when the former exceeds 

 the latter in a greater proportion than that of six to one ; or, as 

 nearly as I can estimate from other experiments, when the solid 

 urea is less than -JL_th of the weight of th.e mixed extract. There 

 is one property, however, of tiiis substance, originally pointed out 

 by Fourcroy and Vauquelin, which enables us to detect urea;> 

 even when present in such minute quantities, as to escape dis- 

 covery by the nitric acid. Amidst the great variety of animal 

 products, this appears to be the only one which is decomposed, 

 when in a state of solution, by the temperature of boiling water. 

 At this low degree of heat, its elements, held together by a balance 

 of affinities which is easily disturbed, arrange themselves in a new 

 order; ammonia and carbonic acid are generated; and carbonate 

 of ammonia is composed, equivalent in weight to about two^ 

 thirds that of the urea.* It is in the fluid, therefore, condensed 

 during the evaporation of diabetic urine, that we are to look for 

 traces of the existence of urea; and in this fluid I have invariably 

 found a sufficient quantity of carbonate of ammonia to restore 

 the colour of a reddened litmus paper, and to precipitate muriate 

 of lime. When the distillation is carried so far, as to reduce the 

 residuum to charcoal, the last products are strongly acid, in con- 

 sequence of the production of the pyromucous acid from the de- 



* Healthy urine, it is well known, is acid when first voided, and redden* 

 vegetable blue colours, owing, as Thenard asserts, (Ann. de Chim. lix, 270) 

 to its containing acetic acid. After being heated, however, for a short time, 

 the liquor becomes alkaline, in consequence of the production of ammonia. 

 When fresh made urine is distilled, carbonate of ammonia comes over, though 

 in small proportions, till almost the whole of the fluid is evaporated. It ii 

 then prodiaced in a great quantity, and lines the neck pf the retort and the re- 

 ceiver with a solid incrustation. The quantity of carbonate of ammonia, 

 which I have thus obtained from a wine galtcn of fresh and concocted urin?, 

 has varied from two to three ounces. Ifs production may chiefly be referred 

 to the urea, which is equally decohiposed by heat and by putrefaction. I have 

 been informed indeed by persons who distil urine for manufacturing pnrposes,, 

 tliat little if any increase of volatile alkali is gained by previously allowing 

 tke urine to become pittrid , 1, . .. . ^. 



