Ethanol always boils at the same temperature, on one condition: the atmospheric pressure must be constant. Meanwhile the weather, and especially altitude, shifts that point by up to several degrees. For home distillers this is not a theoretical number - it is a practical challenge that affects the quality of fractionation and the efficiency of separation.<\/p>\n
What should you do? Use our calculator based on the Antoine equation. Enter the atmospheric pressure (check it in a weather app before distilling), and the calculator shows you the boiling point of alcohol under exactly that condition. That way you know which temperature to aim for to separate the fractions precisely, whatever the weather or the altitude.<\/p>\n
Ethanol boils at 78.3 \u00b0C at a standard pressure of 1013 hPa<\/strong> (at sea level, \u201cnormal\u201d weather). That is the number that appears in every chemistry textbook. In a real home or on a farm, however, the pressure is rarely exactly 1013 hPa, so temperatures can shift by 1-3 \u00b0C either way.<\/p>\n The difference may seem small, but for distillation it is crucial. If you want to separate an unwanted fraction, you need to know the exact boiling point of the alcohol. Too high a temperature means you are already collecting tails rather than the main alcohol (hearts) before you have got rid of the unwanted smells. Too low - and the hearts will take too long to distil.<\/p>\n That is why the EQUINOX T-4 WiFi thermometer with an alarm is the answer: it reads the temperature sensor in the liquid, and you know what that temperature should be in your particular atmospheric conditions.<\/p>\n The lower the pressure, the lower the boiling point. It is a law of physics: liquid molecules need less energy (a lower temperature) to escape as vapour when there is less air pressure on them.<\/p>\n Practical consequences:<\/strong> At low altitude and normal pressure you have ~78.3 \u00b0C. But at 800 m above sea level (pressure ~930 hPa), the boiling point drops to about 75 \u00b0C. That 3 \u00b0C difference changes the whole dynamics of the process. Ethanol evaporates faster, the phases are shorter, and the distillation speed is sometimes harder to control.<\/p>\n Many home distillers are not aware of this. They set their thermometer to a fixed \u201c78 \u00b0C\u201d and do not adjust it to the weather. As a result, on a rainy day (lower pressure) the thermometer can mislead by a couple of degrees. Those couple of degrees are enough to collect the fractions wrongly.<\/p>\n The Antoine equation is the mathematical route from pressure to temperature. It looks like this:<\/p>\n Where P is the pressure in millimetres of mercury (mmHg), T is the temperature in degrees Celsius, and A, B, C are constants specific to ethanol (A=8.04494, B=1554.3, C=222.65).<\/p>\n Sounds complicated? In practice you do not have to calculate by hand. That is what the calculator is for. Enter your atmospheric pressure (you can get it from the EQUINOX T-4 thermometer app, a weather station or a digital barometer), and the calculator solves the equation for temperature.<\/p>\n What do you gain? Precision. Instead of blind faith in \u201calways 78 \u00b0C\u201d, you work with a number adjusted to the real conditions. That is exactly the difference between amateur work and a serious approach.<\/p>\n Imagine two scenarios: winter with high pressure (1013 hPa) and autumn with a low (980 hPa). Both are realistic conditions.<\/p>\n Scenario 1: Fine weather, pressure 1013 hPa<\/strong> Scenario 2: Changeable weather, pressure 980 hPa<\/strong> It is not a great tragedy, but it shows why the calculation matters. An experienced distiller always takes the weather into account.<\/p>\n Not directly. A WiFi thermometer is a temperature sensor that shows you the temperature of the liquid. But if you know the boiling point for your altitude and pressure (thanks to our calculator), you can program it to warn you at exactly the right moment.<\/p>\n The WiFi controllers we offer can set temperature alarms with a resolution of 0.1 \u00b0C. This means you can tell the system: \u201cHeat to exactly 76.8 \u00b0C, then reduce the power to 30% and hold.\u201d That prevents overheating and using up the fraction you want to keep.<\/p>\n Many people learn that \u201cethanol boils at 78 degrees\u201d and never change that assumption. In reality you should check the pressure before every distillation. It takes 10 seconds, and the effect on your work is real.<\/p>\n If you live in the mountains or distil in different places, the boiling point changes too. A low-lying area has a different pressure from the foothills or the mountains. Do not ignore it.<\/p>\n If your thermometer or controller has a \u201cfixed\u201d boiling point that cannot be changed, you lose flexibility. Good solutions allow adjustment.<\/p>\n Temperature is one of the signals, but not the only one. In changing conditions there can be small lags between the theoretical boiling point and reality. Always watch how the distillate tastes and smells, alongside monitoring the temperature.<\/p>\n Wash, yield, dilution, alcoholmeter correction, sugar scales, column and heating element power, costs - 16 distilling calculators in one place. Enter your data and the result updates live.<\/p><\/header> How does atmospheric pressure affect the boiling point?<\/h2>\n
The Antoine equation - how does it work in practice?<\/h2>\n
log\u2081\u2080(P) = A \u2212 B \/ (C + T)\n<\/code><\/pre>\nWorked example: the difference between 1013 hPa and 980 hPa<\/h2>\n
\nThe boiling point of ethanol is 78.3 \u00b0C<\/strong>. You switch on the heating element, the temperature in the column rises, and when you reach 78 \u00b0C, distillation starts shortly afterwards. You adjust the power, control the speed, everything runs smoothly.<\/p>\n
\nThe boiling point drops to about 76.5 \u00b0C<\/strong>. If you watch the thermometer waiting for 78 \u00b0C, you will already be in the main distillation. Because of the 1-1.5 \u00b0C difference you can lose part of the transition phase, which could contain interesting aromas.<\/p>\nDoes a WiFi thermometer help control this parameter?<\/h2>\n
Common mistakes when setting the boiling point<\/h2>\n
Always using the same temperature<\/h3>\n
Ignoring altitude<\/h3>\n
Calibrating the thermometer to a fixed value<\/h3>\n
Watching only the temperature and ignoring the taste and smell of the distillate<\/h3>\n
\nDistillation calculator<\/h2>