and it is only necessary to apply a single confirmatory test.  Allow some of the urine to flow carefully, according to Heller’s method, over a couple of drachms of yellow nitric acid (i.e., acid containing traces of the lower oxides of nitrogen).  A number of rapidly changing colors soon appear, passing through green, blue, violet, and red to yellow.  The first of these tints, green, is the only one that undoubtedly points to the presence of biliary coloring matter, all the others being yielded by another constituent of urine, indican, when similarly treated.  Should the color of the urine suggest the presence of only traces of bile, the best plan is not to treat the urine directly, but extract a quantity of it by shaking with chloroform.  On separating the latter, and covering with yellowish nitric acid, the color changes will be observed penetrating into the chloroform.  A little, also, evaporated on a slide yields reddish crystals, which exhibit a pretty play of colors under the microscope when touched with nitric acid.

It is not unfrequently considered important to test urine for the sodium salts of the conjugate biliary acids, taurocholic and glycocholic.  Dr. Oliver, of Harrogate, has proposed the use of an acidulated peptone solution for this purpose, and the reaction is undoubtedly a good one.  The reagent is prepared by dissolving 30 grains of flesh peptone, 4 grains of salicylic acid, and 30 minims of strong acetic acid, in sufficient water to produce 8 fluid oz. of solution.  Thus prepared, the peptone shows no signs of decomposition on keeping.  To use the test, mix 1 fluid drachm of the reagent with 20 minims of urine, previously diluted to a standard specific gravity of 1.003.  A haze is produced, which will be found to be more or less distinct, according to the proportion of bile salts present.

CHLORIDES.

A normal and variable constituent of urine, chlorine, is not usually required to be determined.  Should the estimation be considered necessary, however, Volhard’s silver process, which has been noticed in treating of uric acid, possesses several advantages over other methods:  10 c.c. of urine are diluted with 60 c.c. of distilled water.  To this is added 2 c.c. of pure 70 percent. nitric acid and 15 c.c. of a standard solution of silver nitrate (1 c.c. = 0.01 gramme NaCl).  Shake well and make up to 100 c.c. with water.  All the chlorine present will now be precipitated in the liquid as a silver salt.  Filter an aliquot part (about 70 or 80 c.c.), and determine in the clear solution the excess of silver with standard ammonic thiocyanate, using the ferric alum indicator.  The difference between this and the amount of silver originally present in the aliquot part has been precipitated as silver chloride (AgCl).  The whole estimation should be conducted as rapidly as possible.  A simple calculation will then give the proportion of chlorine in the dilute urine, and this multiplied by ten shows the percentage.  It is usual to report in terms of NaCl.