3. (Dollfuss' Concentrated Acetic Acid.) Take of dried acetate of lead, 12
oz.; sulphuric acid, 6 oz.; distil 7 ounces.
_d._ From ACETATE OF LIME:--
1. (Christl.) Raw acetate or pyrolignate of lime (prepared by Völckel's
process), 100 parts, is mixed with hydrochloric acid (20° Baumé, or sp.
gr. 1·1515), 120 parts; and after 12 hours, distilled in a copper vessel,
with a gradually applied heat. The product is 100 parts or lbs. of acetic
acid of 8° Baumé (sp. gr. 1·0556), containing about 47% of hydrated acid,
only slightly coloured and empyreumatic, fit for various manufacturing
purposes. The advantage of this process is the low price of hydrochloric
acid, and the product not being contaminated with sulphuric or sulphurous
acid.
_Obs._ It will be found that pyrolignate of lime generally contains 60% to
70% of neutral acetate; but should it contain either more or less, a
proportionate quantity must be employed. When the proper proportions are
used the distillate gives only a scarcely perceptible turbid cloud when
tested with nitrate of silver. If the hydrochloric acid used has the sp.
gr. 1·16, a less quantity being employed, the product will have the sp.
gr. of 1·058 to 1·061, and will then contain from 48 to 51% of the
monohydrate, or 41 or 42% of anhydrous acetic acid. The resin sometimes
found floating on the mixed ingredients should be carefully removed, by
skimming, before distillation.
As acid of the above strength is rarely required, and as the distillation
is more easily conducted when the ingredients are less concentrated, a
little water may be conveniently added either before or towards the end of
the distillation. Hence the following proportions have been recommended:--
2. (Völckel.) Acetate of lime (as last), 100 parts; hydrochloric acid (sp.
gr. 1·16), 90 to 95 parts; water, 25 parts; mix, and proceed as before.
Prod. 96 to 98 parts of an excellent acid, well adapted to trading
purposes, having a sp. gr. about 1·050, and containing nearly 40% of
hydrated acetic acid. It has been correctly remarked, that the acetic acid
produced with hydrochloric acid is always of better quality than that
produced with sulphuric acid; being not only less coloured, but also
entirely free from sulphurous acid. The distillation uniformly proceeds
with ease and regularity, and the whole of the acetic acid passes over
between 212° and 248° Fahr.; by which the danger of contamination with
other products, resulting from a high degree of heat, is obviated.
3. An Acetic acid sufficiently strong and pure for many ordinary purposes
may be obtained without distillation, by pouring strong sulphuric acid, 60
parts, diluted with water, 5 parts, on well-dried acetate of lime, 100
parts; digesting, with occasional agitation in a close vessel, decanting
the clear liquid, and straining the remainder.
[Illustration:
_A_, Furnace.
_B B B B_, Glass receivers.
_C_, Stoneware retort.
_D_, Bottle containing vinegar.
_E E E E_, Basins containing water.
_F F F F_, Supports for basins.
_G_, Welter safety-tube.
_H_, Supply-pipe of cold water.
_I I I I_, Cocks to supply water to the basins.
_J_, Water main.
_L_, Adapter connecting retort and globes.]