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PHOSPHATES. 761
was necessary to produce the final reaction, then for 100 cc. of the filtrate
(=10 cc. urine) 9.2 cc. of this solution arc necessary. 9.2 cc. of the
Bulphocyanide solution corresponds to 4.6 cc. of the silver solution,
and since 20—4.6 = 15.4 cc. of the Bilver solution was necessary to com-
pletely precipitate the chlorine in 10 cc. of the urine, then 10 cc. con-
tains 0.154 gram of NaCl. The quantity of sodium chloride in the urine
is therefore 1.54 per cent, or 15.4 p. m. If we always use 10 cc. for the
determination, and always 20 cc. of AgNCb solution, and dilute with
water to 100 cc, the quantity of Na( ’1
in 1000 parts of the urine is found
by subtracting from 20 the number of cubic centimeters of sulphocyanide
(R) required with 50 cc. of the filtrate. The quantity of NaCl p. m.
therefore under these circumstances = 20 — R, and the percentage of
NaCl = ^.
If it is necessary to destroy the organic urinary constituents before titration,
this can be best performed, according to Dehn, 1
by evaporating the urine (10 cc.)
to dryness on the water-bath after the addition of a small amount of sodium per-
oxide, then faintly acidifying with nitric acid and then titrating according to
Volhard. Incineration is unnecessary.
For the approximate estimation of chlorine in the urine Ekehorn has made
use of Volhard’s titration method by using for the determination a glass tube
closed at one end and divided into half cubic centimeters and called the chlorom-
eter. The reagents necessary are: (a) a mixture of 20 cc. silver-nitrate solution
(according to Volhard), 5 cc. nitric acid and water to 100 cc; (b) 40 cc. sul-
phocyanide solution and 60 cc. of a ferric alum, chlorine free and saturated at
the ordinary temperature. The silver-nitrate solution, of which each cubic
centimeter corresponds to 0.002 gm. NaCl, is equivalent to the iron sulphocyanide
solution. First 2 cc. of the urine are placed in the graduated tube and then 0.5
cc. sulphocyanide solution, and the silver-nitrate solution gradually added (shak-
ing the tube closed with a rubber stopper) until the coloration of the sulphocyanide
just disappears. 0.5 cc. is subtracted from the silver solution for the 0.5 cc. of
the sulphocyanide; the tube is so graduated that the quantity of XaCl in the
urine in parts per thousand is read off directly on the tube. The difference
between these results and those obtained by Volhard’s titration method amounts
only, according to C. Th. Mobner,2
to 0.25 to at most 0.5 p. m.
The approximate estimation of chlorine in the urine (which must be free from
protein) is made by strongly acidifying with nitric acid and then adding to it,
drop by drop, a concentrated silver-nitrate solution (1: 8). In a normal quantity
of chlorides the drop sinks to the bottom as a rather compact cheesy lump. In
diminished quantity of chlorides the precipitate is less compact and coherent,
and in the presence of very little chlorine a fine white precipitate or only a
cloudiness or opalescence is obtained.
Phosphates. Phosphoric acid occurs in acid urines partly as dihydro-
gen, MH2PO4, and partly as monohydrogen, M2HPO4, phosphates,
both of which may be found in acid urines at the same time. The
proportion of these may vary eonsiderabby ; acid urines contain chiefly
dihydrogen phosphate and in many cases the urine seems to contain only
dihydrogen phosphate and sometimes indeed only a small quantity of phos-
1
Zeitschr. f. physiol. Chem., 44.
2
Ekehorn, Hygiea, Stockholm, 1906; Morner, Upsala Lakaref. Forh. (N. F.), 11.
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