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696 . URINE.
inine interferes with Trommer’s test for sugar, partly because it has a
reducing action, and partly by retaining the copper suboxide in solution.
The compound with copper suboxide is not soluble in a saturated soda
solution, and if a little creatinine is dissolved in a cold saturated soda
solution and then a few drops of Fehling’s reagent added, a white flocculent
compound separates after heating to 50-60° C. and then cooling (v.
Maschke’s 1
reaction). An alkaline bismuth solution (see Sugar Tests)
is not reduced by creatinine.
An aqueous solution of creatinine is precipitated by picric acid.
The precipitate consists on recrystallization from hot water, of thin,
silky, pale yellow needles (Jaffe). If the urine is treated with picric
acid (20 cc. of a 5 per cent solution in alcohol for each 100 cc. urine),
then a double picrate of creatinine and potassium is precipitated (Jaffe).
If a solution of creatinine in water (or urine) is treated with a watery
solution of picric acid and a few drops of a dilute caustic-soda solution,
a red coloration, lasting several hours, immediately occurs at the ordinary
temperature, which turns yellow on the addition of acid (Jaffa’s 2
reac-
tion). Acetone gives a more reddish-yellow color. Glucose gives
with this reagent a red coloration only after heating. If we add a few
drops of a freshly prepared very dilute sodium-nitrcprusside solution
(sp.gr. 1.003) to a dilute creatinine solution (or to the urine) and then a
few drops of caustic soda, a ruby-red liquid is obtained which quickly
turns yellow again (Weyl’s 3 reaction). If the cold yellow solution is
neutralized and treated with an excess of acetic acid, a crystalline pre-
cipitate of a nitroso-compound (C4H6N4O2) of creatinine separates on
stirring (Kramm) or creatininoxim (Schmidt 4
). If, on the contrary,
the yellow solution is treated with an excess of acetic acid and heated,
the solution becomes first green and then blue (Salkowski 5
) ; finally
a precipitate of Prussian blue is obtained.
A reaction which in description is similar and which, although not solely
(Arnold) but at least partially (Holobut), appears after partaking of protein
food or meat soup is Arnold’s reaction. 6
This reaction is due to an unknown
endogenous metabolism product. If 10-20 cc. urine are treated with a few drops
of a 4 per cent sodium nitroprusside solution and then with 5-10 cc. of a 5 per
cent sodium or potassium hydroxide solution, at first a strong and pure violet
color is obtained with an absorption band between D and E, then it becomes
purple-red and then brown-red and finally yellow. On the addition of acetic
1
Zeitschr. f. analyt. Chem., 17.
2
Zeitschr. f. physiol. Chem., 10.
3
Ber. d. deutsch. chem. Gesellsch., 11.
’Kramm, Centralbl. f. d. med. Wissensch., 1897; Schmidt, cited from Chem.
Centralbl., 1012, 2.
5
Zeitschr. f. physiol. Chem., 4.
8
Arnold, Zeitschr. f. physiol. Chem., 49 and 83; Holobut, ibid., 56.
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