So the little plant liberates by some wonderful means a material called diastase, which has the power of changing starch into sugar. It does it, of course, for the purpose of providing its own necessary food, but the maltster does not want the process to go too far: he only wants to produce the diastase, and that is
why he kills the plants, after which he has finished with the matter and hands the "malted" grain or "malt" over to the distiller for the next process.
The distiller mixes the malt with warm water, whereupon the diastase commences the conversion of the starch of the grain. At this stage fresh grain may be added and potatoes, indeed almost anything composed largely of starch for the diastase to work upon. The process goes on until, in time, the liquid consists very largely of sugar dissolved in water, which is strained away from what is left of the grain, etc.
Malt sugar is very similar to, but not quite the same as, cane sugar. It consists of twelve parts of carbon, twenty-two of hydrogen and eleven of oxygen. It is an interesting little puzzle to sketch those atoms out on paper, each with its proper number of hooks, and see how they can be combined together. Malt sugar, milk sugar and cane sugar all consist of the same three elements in the same proportions and the difference between them is no doubt due to the different ways in which the atoms can be hooked up together.
Yeast is next added to the liquid, upon which the process of fermentation is set up, the tiny living cells of the yeast plant producing a substance which is able to change the sugar into alcohol.
The alcohol thus formed is, of course, combined with water, but it can be separated from it by gentle heating since it passes off into vapour at a lower temperature than does water. Thus the vapour first arising from the mixture is caught and cooled
whereby the liquid alcohol is obtained. This operation, called fractional distillation, has to be repeated if alcohol quite free from water is required, in addition to which the attraction which quicklime has for water is called into play to coax the last remnant of water from the other.
And now, how about the methyl alcohol? That is obtained in quite a different way, by heating wood and collecting the vapours given off by it. Hence it is often called "wood spirit."
As a matter of fact, at least two very valuable substances are obtained by this operation, methyl alcohol and acetone.
The vapours given off by the wood are cooled, whereupon tar is formed while upon it there floats a dark liquid which contains the wood spirit, acetic acid and acetone.