This section is from the book "The Manufacture Of Liquors, Wines, And Cordials, Without The Aid Of Distillation", by Pierre Lacour. Also available from Amazon: Manufacture of Liquors, Wines, and Cordials, Without the Aid of Distillation.
Consists of from forty to forty-five per cent, of alcohol, and is known as single and double rectified whiskey; and probably the only difference between them is to be found in their names, as there is but little or none in their relative properties. It is possible that the double rectified whiskey may contain less essential oil than single rectified, by virtue of having passed through the rectifier for the third time; and this was a positive necessity, as the rectifiers were nearly exhausted; and thus it will be observed that three courses of filtration in exhausted rectifiers, are equivalent to one filtration through new rectifiers. For arranging rectifiers, and all information of interest upon this subject, see under the head of "Removal of Grain Oil."
This whiskey is noticed under the head of low proof spirit. It contains about twenty per cent, of alcohol, and the deficient alcohol is supplied from the usual articles used for giving artificial strength to spirits.
This oil is always present in the production of alcoholic fermentation, and is an ingredient in spirit distilled from grain and potatoes. Grain spirit contains one part in five hundred by measurement. Fusel oil is an oily, colorless liquid, of a.strong, disagreeable odor, and acrid, burning taste. It is soluble in a very small proportion of water, but in all proportions in alcohol.
There has been a multiplicity of plans proposed, and numerous theoretical suggestions offered, for the removal of grain oil for manufacturing purposes. We will notice a few of them. The first consists in saponifying "the oil by the aid of caustic potassa, rendering the oil of a soapy consistency, or forming the oil into flocculent particles, that would be easily sepa rated from the spirit by straining. Unfortunately for this theory, the potassa combines with the spirit, and forms an alkaline solution.
The other plans consisted of filtration through chloride of lime, magnesia, etc, - they have all been rejected as impracticable. The most feasible one, however, was the destruction of the oil by means of nitrate of silver; the oil, on coming in contact with the silver, subsides in the form of a black powder, and the powder to be separated by straining, and the silver to be recovered by the use of nitric acid.
Animal and vegetable charcoal are to be preferred, as presenting innumerable advantages over any other articles whose uses involve a chemical knowledge. The action of charcoal is simple, and adapted to the comprehension of all, being mechanical, when used for grain oil, as it acts by absorption. For full information see Charcoal Filterers.
The last process consists in concealing the oil, by infusing an article, the aroma of which conceals the odor of the grain oil.
Our list of aromatics, either singly or combined, furnishes some tempting inducements to those dis-poseed to deal in this manner.
Another process, involving but a trifling expense, consists in filtering the spirit through a body of wheat bran, from eight to twelve inches in depth. The liquid as it passes off is somewhat heavy in color; finings will remove this. To obviate this, oat meal is used to the same depth as the bran in the filter. By some rice is used in alternate layers, the better to enable the fluid to pass off rapidly. This process gives to the spirit a luscious taste, a fine bead, and is decidedly the most economical mode that is in use for the manufacture of low proof spirits.