This book is included in the Self Reliance Primitive Industry section.
THE EDITOR'S PREFACE.
IN the compilation of the present, as in the preceding
volumes of the series, it has been the aim of the Editor
to combine conciseness with practical utility. He hopes
his endeavours may have been successful.
The Editor takes this opportunity of thanking his
friends, Mr. JAMES TAYLOE and Mr. JOHN LINFORD, for
many valuable suggestions; as well as for having given
the sheets the benefit of their revision.
JOHN GARDNER, F.I.C., F.C.S.
CONTENTS
Chapter I. ACETIC ACID AND VINEGAR
Chapter II. AMMONIA
Chapter III. ALUM AND ALUM-MAKING
CHAPTER I. - ACETIC ACID.
Acetic Acid, HC2H3O2
or C2H4O2. Syn. Acid of Vinegar, Normal
Acetic Acid, Real Acetic Acid, Hydrated Acetic Acid, Absolute Acetic
Acid.
ACETIC ACID is the sour principle of
vinegar. Mention of vinegar occurs both in "Numbers" and "Proverbs."
HIPPOCRATES employed it in medicine, and the alchemists obtained acetic
acid in a concentrated form by distilling verdigris. LOWITZ was the
first to procure pure hydrated or normal acetic acid ; and Dr. JOHN DAVY
first pointed out that acetic acid was produced when spongy platinum was
brought into contact with the vapour of alcohol.
Commercial acetic acid is met with under the forms of the pure glacial
and dilute acids of the chemist and pharmacist, and of vinegar, of which
there are many varieties.
Its sources are Fermented liquors; the vinegars of commerce; alcoholic
liquors; wood, from which it is obtained, as pyroligneons acid, by
distillation; the commercial acetates of soda, potassa, lime, lead,
copper, &c. The acetic acid of the chemist and of commerce is almost
wholly obtained from the acetates, either by the action of a strong
acid, which seizes on the base, setting the acid free; or by dry
distillation, in which the high degree of heat employed separates the
acetic acid from the base in the form of vapour. It is also obtained by
the oxidation of alcohol.
Acetic acid is produced either by the partial dehydrogenation and
subsequent oxidation of bodies containing its
elements, or by their destructive distillation. The first is effected by
their exposure, in a finely divided state, to the
action of air or atmospheric oxygen, as in the quick process of making
vinegar; or by submitting them, in combination with ferments, to contact
with a free supply of atmospheric air, as in the old field process of
making vinegar; or by exposure to the direct action of chemical or
mechanical oxidizing agents, as condensed air (platinumblack process),
chromic and nitric acid, &c.; in which latter case pure acetic acid is
obtained. In general it is alcohol more or less dilute, particularly as
it exists in fermented liquors, which is thus converted into acetic
acid. In the second process viz., by destructive distillation wood is
the substance usually employed, and heat is the agent which develops the
acid.
The conversion of alcohol into acetic acid is not immediate and direct.
The atmospheric oxygen first oxidizes two
atoms of its hydrogen, aldehyd and water being formed; and this aldehyd,
uniting with one atom of oxygen, produces one molecule of acetic
acid. The changes are represented in the following equations: --
1. Alcohol (C2H6O) + Oxygen (O) = Aldehyd. (C2H4O) + Water (H2O)
2. Aldehyd. (C2H4O) + Oxygen (O) = Acetic Acid (HC2H3O2)
After the first formation of aldehyd, the two processes,
unless artificially checked, go on simultaneously, as long as any
undecomposed alcohol is present.
The conversion of alcohol into acetic acid, although
greatly accelerated by the presence of yeast or of other
ferments, is rather a case of slow combustion than of fermentation.
Acetification effects combination, as shown by
the foregoing equations ; whereas fermentation resolves
complex bodies into simpler ones, as when sugar is converted
into alcohol and carbonic anhydride. Moreover, the
presence of ferments is not essential to the change, since
pure alcohol becomes acidified when exposed to the oxidizing
agents already named.
Another remarkable distinction between acetification and fermentation is, that the former requires the continuous
presence of atmospheric oxygen, whilst the vinous fermentation,
after being once established, proceeds perfectly
without it.
During the oxidation of the alcohol of vegetable solutions,
some of the other organic matters present also suffer change.
A white gelatinous mass known as Mother of Vinegar is
commonly deposited, but this is a secondary result of the
process, and not, as formerly supposed, one essential to it.
In ordinary cases acetification occurs only at or near the
surface of the liquid; which accounts for the length of
time required for the operation under the old process of
fielding, and the shorter time in which it is accomplished
under HAM'S process.
Acetification proceeds favourably at temperatures ranging
from 60 Fahr. (15.5° Cent.) to 90° Fahr. (32.2° Cent.), and,
according to LIEBIG, most rapidly at 95° Fahr. (35° Cent.).
In the quick process of vinegar-making, a temperature of 90°
(32.2° Cent.) to 92° Fahr. (33.3° Cent.) is generally aimed
at ; but it often rises to 100° (37.7° Cent.), or even to 105° Fahr. (40.5 Cent.). As the temperature falls, acetification
proceeds more slowly, and at 46° (7.7° Cent.) to 50° Fahr.
(10° Cent.) it ceases altogether.
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