Recently, an experimental technology published in Journal of Chemical Education (J. Chem. Educ., 10.1021/ed077p629) has attracted attention in the scientific research community. Using dry ice as the freezing source, this scheme can construct a continuous and stable low-temperature reaction medium by adjusting the mixing ratio of ethanol and ethylene glycol, covering a temperature range of -12℃ to -78℃, providing a more flexible option for low-temperature reactions in laboratories. In traditional cryogenic bath configurations, ice-salt baths are greatly affected by ambient temperature, making it difficult to reach below -10℃ in summer; although the combination of dry ice and organic solvents is widely used, the temperature range is discontinuous; liquid nitrogen requires complex operations and high costs. The new scheme solves these pain points. Precise temperature control can be achieved only by adjusting the volume ratio of two common solvents, which is easy to operate and cost-effective. Similar to the standardized configuration mode of vacuum distillation, it greatly reduces the experimental threshold. It is reported that there are various common cryogenic bath systems in laboratories. Ice-salt baths can achieve low temperatures from -4℃ to -54.9℃ by combining different salts with crushed ice. For example, mixing 143 grams of calcium chloride hexahydrate with 100 grams of crushed ice can reach -54.9℃; the combination of dry ice with solvents such as ethanol and acetone can obtain an environment of -72℃ to -100℃; liquid nitrogen can achieve ultra-low temperatures as low as -196℃. The advantage of the new scheme lies in temperature continuity, filling the gap in temperature control of traditional methods in specific ranges. The promotion of this technology will benefit researchers in many fields such as organic synthesis and materials science, especially suitable for experimental scenarios that require frequent adjustment of low-temperature parameters. Its standardized ratio mode also provides a new possibility for the standardization of low-temperature operations in laboratories.
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