vided nickel, serving as a catalyst, the two unite and we have
alcohol, according to this reaction:

C_{2}H_{4}O + H_{2} --> C_{2}H_{6}O

acetaldehyde _added to_ hydrogen _forms_ alcohol

Alcohol we are all familiar with--some of us too familiar, but the
prohibition laws will correct that. The point to be noted is that the
alcohol we have made from such unpromising materials as limestone and
coal is exactly the same alcohol as is obtained by the fermentation of
fruits and grains by the yeast plant as in wine and beer. It is not a
substitute or imitation. It is not the wood spirits (methyl alcohol,
CH_{4}O), produced by the destructive distillation of wood, equally
serviceable as a solvent or fuel, but undrinkable and poisonous.

Now, as we all know, cider and wine when exposed to the air gradually
turn into vinegar, that is, by the growth of bacteria the alcohol is
oxidized to acetic acid. We can, if we like, dispense with the bacteria
and speed up the process by employing a catalyst. Acetaldehyde, which is
halfway between alcohol and acid, may also be easily oxidized to acetic
acid. The relationship is readily seen by this:

C{2}H_{6}O --> CC_{2}H_{4}O --> C_{2}H_{4}O_{3}

alcohol acetaldehyde acetic acid

Acetic acid, familiar to us in a diluted and flavored form as vinegar,
is when concentrated of great value in industry, especially as a
solvent. I have already referred to its use in combination with
cellulose as a "dope" for varnishing airplane canvas or making
non-inflammable film for motion pictures. Its combination with lime,
calcium acetate, when heated gives acetone, which, as may be seen from
its formula (C_{3}H_{6}O) is closely related to the other compounds we
have been considering, but it is neither an alcohol nor an acid. It is
extensively employed as a solvent.

Acetone is not only useful for dissolving solids but it will under
pressure dissolve many times its volume of gaseous acetylene. This is a
convenient way of transporting and handling acetylene for lighting or
welding.

If instead of simply mixing the acetone and acetylene in a solution we
combine them chemically we can get isoprene, which is the mother
substance of ordinary India rubber. From acetone also is made the "war
rubber" of the Germans (methyl rubber), which I have mentioned in a
previous chapter. The Germans had been getting about half their supply
of acetone from American acetate of lime and this was of c