Water and n-butanol form an azeotrope; what happens if the temperature is lowered below 0 degrees?

Hello: When an organic solvent is added to water, such as the butanol solution you mentioned, the boiling and freezing points of the water will definitely change. As for by how much the freezing point decreases, an accurate answer can only be found by consulting a manual. Just as industrial salt is added to ice and snow on roads in winter, the ice and snow melt quickly when such salt is added; it doesn’t freeze even at temperatures several degrees below zero. There are very classic and detailed explanations of this in physical chemistry; for the specific mechanisms, please refer to physical chemistry textbooks.

Hello, thank you. May I ask where I can find out the specific freezing point?

Hello, OP. As you mentioned, it’s quite difficult to find information on the physical properties of azeotropes in standard manuals. I suggest checking domestic core journals to see if there are any experimental data from researchers in China who have studied this area, such as those in the CNKI database. However, it’s not certain that such information will be available, as not many people in China engage in this kind of fundamental research; most are focused on obtaining projects and research funding, as well as making money more quickly； If CNKI cannot provide the information, it is recommended that you search for it in foreign-language sources, namely core journals from other countries; this requires a certain level of English proficiency, but it’s also possible that such data is not made public ； If you don’t want to use any of the methods above, you can try Aspen Plus; it’s a simpler and faster approach. Most of such important physical property data are related to patent rights; some even more critical data is not made public, and even if it is released, it may not be accurate and is only for reference purposes.

Okay, thank you so much{:1_90:}

70% of the moisture content is in the air – is this related to exhaust gas treatment? Are by-products still formed under such conditions?

I’m asking out of curiosity: with 70% water content, what is the temperature? When the temperature drops to 0 degrees, most of the water will definitely precipitate. What exactly do you mean by freezing? Moreover, the freezing point of such a mixture drops significantly; it definitely won’t freeze at 0 degrees

Hello, the temperature is 35°C; if butanol is present, water should not precipitate, right?

This post was last edited by yjqin1 on 2015-9-10 at 16:30. I have seen supercooled water below zero degrees, but I have never seen superheated ice at +35°C. If by water precipitation you mean the formation of two liquid phases, an aqueous phase and an organic phase, then this is possible. At 35°C, the saturated solubility of water in the n-butanol phase is 20 wt%, while the saturated solubility of n-butanol in water is 7 wt%. The boiling point of the azeotrope formed by butanol and water is around 94.5°C. Whether it is a homogeneous solution formed by water dissolving in n-butanol or n-butanol dissolving in water, its freezing point (more precisely, the ice point) should be well below 0°C.

Azeotropy requires strict conditions; substances with a fixed ratio cannot be formed under just any circumstances. You can check the saturated vapor pressures at 0 degrees Celsius – the partial pressure ratio at 0 degrees and 35 degrees Celsius is significantly different

In addition to forming an azeotrope, water and n-butanol also present solubility issues; they form immiscible organic and aqueous phases. The solubility decreases as the temperature drops, and this depends on the experimental data