Experiments on Urine. 247 
exalic acid, and from which, may in a great meafure be 
_ ‘determined by the appearance of the precipitate: if this 
has the refemblance of flocks, and fubfides flowly, the phof- 
phoric acid is the precipitant ; but if it has a powdery form, 
and fubfides quickly, it muft be produced by oxalic acid 
To this mode we know it may be objected, that all animal 
fubftances yield more or lefs oxalic acid: but this is by no 
mieans true to the extent generally fuppofed; for there are 
feyeral animal fubftances, and the extractive matter of 
healthy urine is one, from which we have never been able 
to procure any fenfible quantity of this acid. Of the differ- 
ent parts of the blood, the coagulating lymph is the only 
one which yields it in any remarkable proportion ; and we 
“‘ Two drachms of very fweet extraét from diabetic urine were taken, 
and treated at, the fame time with an equal quantity of nitrous acid, and 
under exaétly fimilar circumftances. The liquor in this cafe, when pro- 
perly evaporated, depofited a quantity of very tranfparent cryftals, but no 
white powder: thefe, when properly dried on blotting-paper, weighed 40 
r. and, on the addition of 6dr. of hot diftilled water, were entirely dif- 
Prairie fame experiment was repeated with the fweet extractive 
matter from the urine of two other patients; the oxalic acid was procured, 
but not the leaft trace of faccholaétic acid. 
« Half an ounce of honey wastreated with 3 oz. of nitrous acid in the 
ufual manner, and it yielded about 2 dr. of pure oxalic acid, but no fac- 
cholaétic. Honey therefore differs effentially from the fugar of milk ; 
and, indeed, from moft of its obvious properties, would appear to be merely 
a modification of common fugar. 
« In the courfe of thefe experiments I found that 2 dr. of pretty dry and 
“ fweet diabetic extraét yielded, with 12 dr. of the nitrous acid, from 4o 
to 50 grains of cryftallifed oxalic acid, being nearly the proportion which 
may be procured from an equal quantity of common fugar, if we make’ 
allowance for the water and faline fubftances. Upon the whole, there- 
fore, it would appear that this extraétive matter does not contain the 
bafis of the facclolaétic acid--a circumftance which fufficiently diftin- 
guifhes it from the faccharine part of the milk of animals; and feems 
to fhew that it is nothing more than vegetable fugar,if we may be al- 
lowed the expreffion, mixed with a greater or lefs proportion of animal 
mucilage,” C, 
R4 believe 
