Numerous investigations have been conducted to determine the effects of the various by-products. Thus Dujardin-Beaumetz and Audige found that the pig, whose digestive organs are very similar to those of man, when fed for 3o months with pure alcohol, suffered no ill effects, whereas when similarly treated with imperfectly purified spirit (whether derived from beet, potato or grain) suffered considerably. The same investigators, experi menting on dogs, found that the lethal dose of various alcohols was: ethyl 5 to 6 grammes, per kilo body weight, propyl 3.75 grammes, butyl 1.8 grammes and n-amyl 1.5 grammes. Brunton and F. W. Tunnicliffe demonstrated a poisonous action of fur fural upon man and, comparing the after effects upon animals of spirits containing, and freed from, aldehydes, found certain im portant physiological differences between them.
It is important therefore that the spirit manufacturer should adopt all possible precautions to obtain a product which, whilst satisfying commercial requirements, will ensure the minimum possibility of harm to the consumer. The ordinary precautions which at all times should be followed include clean stills and apparatus, a good water supply, high-class and appropriate materials, and careful control of all operations during mashing, fermentation and distillation. The removal of acids can be effected
by neutralization with an alkali in the still, whilst for the elimina tion of fusel oil treatment with charcoal is the common method.
Many processes have been suggested for the artificial maturing of spirits. The most practical are those embodying the passage of hot or cold air, oxygen or ozone through the liquid. Miels and Barr suggest the maturation of new whisky by the addition of a little sherry and a minute trace of sulphuric acid (subsequently neutralized by lime). Hermite suggests a method which consists essentially of adding an electrolysed solution of common salt to the spirit and subsequently redistilling.
Immediately after the Repeal of the Prohibition Amendment in the United States many processes for the quick ageing of spirit were used. None of the spirit so produced could overcome the tradition of age because for centuries consumers of spirit have placed a premium on the age of spirit.
United States Government regulations forbid the labelling of spirit less than 2 years old as whisky and the incentive to produce an artificially matured spirit has therefore been removed.