Thermodynamic Properties


by Adam Chambers

Theory of Thermodynamics

Among the numerous physical properties governing the natural world, there are few more widely applicable than those of thermodynamics. Controlled variance in pressure and temperature can be used as effective tools to serve a wide variety of applications. The effects these variables have on a solvent such as Ethanol (EtOH) or Carbon Dioxide (CO2) are the basis for their use in extracting essential products from Cannabis. The mastery of these principles is the cornerstone of any effective process engineer’s knowledge base within the Cannabis industry and beyond.

Solvency, or the capacity of one substance’s ability to dissolve another, can be increased or decreased according to the temperature and/or pressure it operates under. Lowering the temperature of the solvent slows the atomic resonance amongst the atoms, which will in turn progressively limit what substances are soluble in it. The opposite is true when heating a solvent. This thermal expansion can be observed by the pressure created when a cold solvent is heated up in a sealed vessel. Thermal expansion is also responsible for the state changes we observe such as water boiling or freezing.

When extracting Cannabis with EtOH, for example, this information proves useful as it provides an inkling as to how one can arrange the conditions under which an optimal extraction can be performed for any particular circumstance. If the cannabinoids are the sole target of an extraction, it behooves the operator to consider the fact that chilling the solvent might increase its’ selectivity and exclude many unwanted impurities. Conversely, if a full spectrum representation of the biomass is desired, thermodynamics suggest that this feat would be most effectively accomplished with a room temperature solvent.

The absence or presence of heat is not the only variable that controls the physical qualities of a substance. Pressure is another physical property whose proper manipulation can prove quite useful. By adding pressure to a substance, once can raise the temperature at which it freezes or crystalizes by reducing the same resonant quality of the atoms, forcing them to more easily adopt a solid state. On the other hand, when relieving pressure from a system, the temperature at which a substance will boil is lowered in direct correlation.

A good exemplar for the use of this knowledge would be during the creation of THCa diamond Cannabis concentrates. After using a hydrocarbon blend to conduct an extraction, the extract can be placed in a highly pressurized vessel known as a diamond mine and be left to sit. Under this high pressure, the acidic groups on the cannabinoids are forced to bond into a geometric configuration we observe as a crystalline shape.

Combining the use of both of these thermodynamic properties, the purification of cannabinoids via molecular distillation is made possible. The practice of distillation can be traced back to Roman Egypt in which a substance was purified by boiling it in a vessel, allowing to travel across a short vapor path, and recondensing on a cooler surface in its’ purified form. At atmospheric pressures, however, the temperatures required to vaporize cannabinoids would damage them to the point that they would lose their valuable biological qualities. By reducing the pressure in this distillation system, however, the boiling points of these cannabinoids is lowered significantly, which allows them to be vaporized and recondensed while preserving those valuable biological properties.

Needless to say, though these principles may seem simple in nature, they can be creatively applied for astounding results. From their crucial role in the creation of Cannabis extracts, and beyond, thermodynamics provide remarkably fundamental insights into what is possible with the materials around us.


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