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SULPHATES. 765
greater part is formed by the burning within the body of the proteins
which contain sulphur, and it is chiefly this formation of sulphuric acid
from the proteins which gives rise to the previously mentioned excess
of acids over the bases in the urine. The quantity of sulphuric acid
eliminated by the urine amounts to about 2.5 grams H2SO4 per day.
As the sulphuric acid chiefly originates from the proteins, it follows that
the elimination of sulphuric acid and the elimination of nitrogen runs
almost parallel, and the relation Nit^SO* is about 5:1. A complete
parallelism can hardly be expected, as in the first place a part of the sul-
phur is always eliminated as neutral sulphur, and secondly because the
small proportion of sulphur in different protein bodies undergoes greater
variation as compared with the large proportion of nitrogen contained
therein. In general the elimination of nitrogen and sulphuric acid under
normal and under diseased conditions seems to run parallel. Sulphuric
acid occurs in the urine partly preformed (sulphate-sulphuric acid) and
partly as ethereal-sulphuric acid. The first is designated as A- and the
other as ^-sulphuric acid.
The quantity of total sulphuric acid is determined in the following
way, but at the same time the precautions described in other works
must be observed. 100 cc. of filtered urine is treated with 5 cc. of con-
centrated hydrochloric acid and boiled for fifteen minutes. While
boiling precipitate with 2 cc. of a saturated BaCb solution, and warm for
a little while until the barium sulphate has completely settled. The
precipitate must then be washed with water and also with alcohol and
ether (to remove resinous substances), and then treated according to
the usual method.
The separate determination of the sulphate-sulphuric acid and the
ethereal-sulphuric acid may be accomplished, according to Baumann’s
method, by first precipitating the sulphate-sulphuric acid by BaCb from
the urine acidified with acetic acid, then decomposing the ethereal-
sulphuric acid by boiling after the addition of hydrochloric acid, and
finally determining the sulphuric acid set free as barium sulphate. A
still better method is the following, suggested by Salkowski l
:
200 cc. of urine are precipitated by an equal volume of a barium solu-
tion, which consists of 2 vols, barium hydrate and 1 vol. barium chloride
solution, both saturated at the ordinary temperature. Filter through
a dry filter, measure off 100 cc. of the filtrate which contains only the
ethereal-sulphuric acid, treat with 10 cc. of hydrochloric acid of a specific
gravity 1.12, boil for fifteen minutes, and then warm on the water-bath
until the precipitate has completely settled and the supernatant liquid
is entirely clear. Filter and wash with warm water and with alcohol
and ether, and proceed according to the generally prescribed method.
The difference between the ethereal-sulphuric acid found and the total
quantity of sulphuric acid as determined in a special portion of urine
is taken to be the quantity of sulphate-sulphuric acid.
1
Baumann, Zeitschr. £. physiol. Chem., 1; Salkowski, Virchow’s Arch., 79.
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