Using Salt in Distillation

Maurice advises ..
    ..put a teaspoonful of ordinary table salt into the wash ..the spirit comes over much better..
Salts are sometimes used during extractive distillation (eg when trying to distill past the 95.6% azeotrope) so as to depress the volatility of the water (eg effectively increase its boiling point, so you get a greater % of ethanol off compared to normal). Because the salt is non-volitile, it will always remain in the pot, and not turn up in the distillate.

The "Household Cyclopedia" recommends ...
    Table-salt thrown into the still, in the proportion of 6 oz. (180 g) to 10 galls. (38 L) of any liquid to be distilled, will greatly improve the flavor, taste, and strength of the spirit. The viscid matter will be fixed by the salt, whilst the volatile matter ascends in a state of great purity.

David cautions though ..
    make sure you use ordinary non-iodised salt not iodised. Virtually all salt sold in NZ in containers for domestic consumption is iodised. Also be aware that salt is sodium chloride and that chlorides attack stainless steel and can bad pit it. It can also and will generally shorten your element life.

Bokakob advises ..
    The best time to introduce salt in the distillate is when distilling second time. The first distillation, stripping, is used to reduce the amount of liquid and some of impurities. The second run is the place where this salt helps in separating boiling point of water. I always add regular salt for the second distillation in proportion of about two heaping table spoons for about 8-10 liters of 65% abv.

Ken recommends using Sodium Carbonate to reduce the amount of fusel oils present ..
    .. try sodium carbonate @ 4.5 grams/ litre, add it when the wash temperatire is at 35-40 degrees C, add slowly then continue with your distillation in the normal manner. Sodium Carbonate is used in the production of soap and it combines with the oils to form a compound that does not evaporate at the normal distillation temperatures that we are using. Voila, cleaner spirit, less carbon treatment needed and more happy faces.
Alex finds
    ... that adding baking soda delineates the border between the good and the bad stuff very sharply. In regular distillation tails presence increases gradually and it is very difficult to decide when to start separating it from the good collection. In presence of baking soda this division is much more defined. (I added 3 full heaped table spoon of regular baking soda per liter of pure alcohol.)

Rob details the bicarb advantage too:
    Assumptions and facts:
    1. A well run column distillation will separate a mixture into fractions based on the boiling points of the components.
    2. There will be some overlap in most real-life stills.
    3. ethyl acetate can be smelled at very low concentrations
    4. acetic acid cannot (it has a higher flavour threshold)
    5. under neutral or acidic conditions acetic acid will esterify to some extent in the presence of ethanol.
    6. sodium acetate is not volatile
    7. sodium bicarbonate will neutralise acetic acid.
    8. sodium bicarbonate may hydrolyse ethyl acetate to a greater or lesser extent.
    9. Adding sodium bicarbonate at some point between a stripping run and final distillation has the effect of decreasing the volume of fractions collected which smell of ethyl acetate.
    10. Adding sodium bicarbonate at some point between a stripping run and final distillation has the effect of making the main fraction "cleaner smelling"
    11. without bicarb the main fraction _can_ smell of ethyl acetate (ymmv)
    12. Sodium acetate is not esterified by ethanol.

    1. Why is there ethyl acetate in the fractions after the heads? (no NaHCO3)
    2. What does NaHCO3 addition do?
    3. How do we best (read easiest) use it?

    Rob's Answers/Opinions (currently!):
    1. During distillation (after column stabilization) ethyl acetate is being formed in the boiler/column. This is why it continues to be present even after heads removal. (see assumptions 1, 5, 11)
    2. Bicarb addition neuralises acetic acid, preventing ethyl acetate formation, distillation of acetic acid, and hence future esterification. (see assumptions 6, 7, 9, 10, 12)
    3. Bicarb addition can hydrolyse ethyl acetate, thus decreasing it's quantity (see assumptions 8, 9)
    4. There is actually a tiny amount of ethyl acetate about, but it is highly noticable (assumption 3). Using bicarb (as opposed to hydroxides) actually has a rather small effect on the amount of esters in the mix. What it does (primarily) is to prevent further formation, and hence allowing the still to do its job without the moving target of continually increasing ester concentrations in the boiler.
    5. Based on this lot, adding bicarb at the start of the final distillation is sufficient, as neutralisation of acetic acid is instantaneous.
Mike warns though ..
    It's OK to add baking soda or other alkali to a STRIPPED wash, but NEVER put it in the primary ferment and then distill. If you do, and your still contains ANY copper, you will severely corrode the copper, and get blue, ammonia-smelling distillate. Not fun!

    Why? Yeast and yeast nutrient both contain lots of ammonium salts (like DAP), which are very stable under acidic conditions, but which release lots of ammonia as the approach neutral conditions. Actually, you will start getting ammonia at about pH 5! Ammonia gas is very corrosive to copper, and you will find your condenser coil packed up with blue crystals after such a run (and blue alcohol too !)

    Schweitzer's reagent is cuprammonium hydroxide, and is formed when copper hydroxide dissolves in a dilute ammonia solution). It is a deep blue colour, and is particularly known for its ability to dissolve cotton. The chemist who first discovered this property was Eduard Mathias Schweizer (1818 -1860), so it seems that it should really be called Schweizer's reagent.

    It forms in stills when ammonia released from alkaline washes (nitrogen source may be plant material or yeasts) reacts with copper hydroxide formed by the action of steam on copper oxides coating the inside of copper columns or components. It may be avoided by ensuring that the liquid in the boiler is slightly acid (pH less than 7).     This page last modified Tue, 20 Jan 2015 20:51:05 -0800