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43
be got out, yet that the sulphate of lime does not contain
oil of vitriol—that A added to B is not A + B, but is C.
Of course it is very difficult for a learned magistrate to
see his way through the fog thus raised, and many professional
chemists would be unable to do so. But, unless
the sulphuric acid can be shown really to exist in the
vinegar in a free or uncombined condition, it is difficult to
get a conviction against wealthy manufacturers who bring
up Queen's Counsel and strings of scientific chemists as
expert witnesses on their behalf. It may, however, as
truly be said that pickles which are greened with copper do
not contain any copper, i.e., that the copper exists in the
vinegar as a combination, and cannot be discovered as
metallic copper.
Genuine malt vinegar always contains potash and other
alkaline bases in combination with acetic acid—as acetates.
If sulphuric acid be added to such vinegar, the first portions
of the sulphuric acid combine with these alkaline bases and
form sulphate of potash (K2 SO4) and other sulphates.
The acetic acid is then set free, and serves to sharpen the
acidity of the vinegar. It is, therefore, only the excess of
sulphuric acid over that required to saturate the alkaline
bases of the vinegar which would be found in the vinegar
as free sulphuric acid. Here again, if not more sulphuric
acid than the equivalent for the alkaline bases had been
poured into the finished vinegar, these chemical experts
would take the view that "the vinegar contained no
sulphuric acid."
In the British Food Journal (Feb., 1900, pages 35, 36,
and 42; and March, pages 65 and 66) these four vinegar
cases Nos. 28, 36, 38, and 51 were fully and instructively
commented upon.
The certificates signed by the chemists of the Government
Laboratory and sent to the learned magistrate were
as follows:—
"The three samples of vinegar marked Nos. 28, 36, and 38, respectively,
and referred to in your letter of the 29th ultimo were
received here on the following day securely sealed.