A practical reference on Sublimation: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-03-02. Anything still debated is marked as such rather than presented as settled.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
| Property | Value | Notes |
|---|---|---|
| Process name | Lyophilization or freeze-drying | Both terms appear in technical standards and literature. |
| Phase transition | Sublimation | Solid ice becomes vapor without a liquid step. |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product temperature and equipment. |
| Typical product temperature | -40 °C to -10 °C | Measured during primary drying; formulation sets limits. |
| Water content after drying | 0.5-3% w/w | Target varies by material and stability needs. |
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
== Four engineering approaches == Synthetic biology has traditionally been divided into four different engineering approaches: top down, parallel, orthogonal and bottom up. To replicate emergent behaviours from natural biology and build artificial life, unnatural chemicals are used. The other looks for interchangeable components from biological systems to put together and create systems that do not work naturally. In either case, a synthetic objective compels researchers to venture into new area in order to engage and resolve issues that cannot be readily resolved by analysis. Due to this, new paradigms are driven to arise in ways that analysis cannot easily do. In addition to devices that oscillate, creep, and play tic-tac-toe, synthetic biology has produced diagnostic instruments that enhance the treatment of patients with infectious diseases.
Amino acid dating is a dating technique used to estimate the age of a specimen in paleobiology, archaeology, forensic science, taphonomy, sedimentary geology and other fields. This technique relates changes in amino acid molecules to the time elapsed since they were formed. All biological tissues contain amino acids. All amino acids except glycine (the simplest one) are optically active, having an asymmetric carbon atom. This means that the amino acid can have two different configurations, "D" or "L" which are mirror images of each other. With a few important exceptions, living organisms keep all their amino acids in the "L" configuration. When an organism dies, control over the configuration of the amino acids ceases, and the ratio of D to L moves from a value near 0 towards an equilibrium value near 1, a process called racemization. Thus, measuring the ratio of D to L in a sample enables one to estimate how long ago the specimen died.
where V100 is the volume occupied by a given sample of gas at 100 °C; V0 is the volume occupied by the same sample of gas at 0 °C; and k is a constant which is the same for all gases at constant pressure. This equation does not contain the temperature and so is not what became known as Charles's Law. Gay-Lussac's value for k (1⁄2.6666), was identical to Dalton's earlier value for vapours and remarkably close to the present-day value of 1⁄2.7315. Gay-Lussac gave credit for this equation to unpublished statements by his fellow Republican citizen J. Charles in 1787. In the absence of a firm record, the gas law relating volume to temperature cannot be attributed to Charles. Dalton's measurements had much more scope regarding temperature than Gay-Lussac, not only measuring the volume at the fixed points of water but also at two intermediate points. Unaware of the inaccuracies of mercury thermometers at the time, which were divided into equal portions between the fixed points, Dalton, after concluding in Essay II that in the case of vapours, “any elastic fluid expands nearly in a uniform manner into 1370 or 1380 parts by 180 degrees (Fahrenheit) of heat”, was unable to confirm it for gases.
=== Pregnancy and breastfeeding === Hypothyroidism is common among pregnant women. A nationwide cohort study showed that 1.39% of all pregnant women in 2010 in Denmark received a prescription of levothyroxine during pregnancy. According to the U.S. Food and Drug Administration pregnancy categories, levothyroxine has been assigned category A. Given that no increased risk of congenital abnormalities has been demonstrated in pregnant women taking levothyroxine, therapy should be continued during pregnancy. Furthermore, treatment should be immediately administered to women diagnosed with hypothyroidism during pregnancy, as hypothyroidism is associated with a higher rate of complications, such as spontaneous abortion, preeclampsia, and premature birth. Thyroid hormone requirements increase during and last throughout pregnancy. As such, pregnant women are recommended to increase to nine doses of levothyroxine each week, rather than the usual seven, as soon as their pregnancy is confirmed. Repeat thyroid function tests should be done five weeks after the dosage is increased. While a minimal amount of thyroid hormones is found in breast milk, the amount does not influence infant plasma thyroid levels. Furthermore, levothyroxine was not found to cause any adverse events to the infant or mother during breastfeeding. Since adequate thyroid hormone concentrations are required to maintain normal lactation, appropriate levothyroxine doses should be administered during breastfeeding.
Sources: en.wikipedia.org
Lee & Co as concrete contractor using a Lee's Mixer, an early example of concrete mixers used during construction on the Admiralty Pier. Further construction from 1897 onwards established the Eastern Arm of the current harbour, the Southern Breakwater and a further extension of the Admiralty Pier. During the First World War, a former cargo ship, the Spanish Prince, was deliberately sunk by the Admiralty close to the entrance to Dover Harbour to prevent German U-Boats from firing torpedoes into the harbour. During World War II, the remains of another ship, the War Sepoy, were sunk alongside the Spanish Prince.
== Structure == Graphene is a single layer of carbon atoms tightly bound in a hexagonal honeycomb lattice. It is an allotrope of carbon in the form of a plane of sp2-bonded atoms with a molecular bond length
== Research == Frank's laboratory projects include an evaluation of MALDI-TOF identification of microorganisms and molecular methods for microbial identification. Frank's research collaboration with Juliane Bubeck Wardenburg in the departments of pediatrics and microbiology at the University of Chicago focused on the pathogenesis of Staphylococcus aureus pneumonia. Using microarray analysis of murine lung RNA, we examined the response of the host to a virulent Staphylococcal strain compared to a strain deficient in the alpha-toxin. We determined that the cellular immune response to infection was characterized by a prominent TH17 response to the wild-type pathogen. Investigation of the host-pathogen interaction and the pathogenesis of Staphylococcal lung injury will contribute to programs aimed at the development of novel therapeutic approaches for Staphylococcal disease.
==== Peptide chain ==== Several of the genes responsible for pyoverdine biosynthesis (e.g., pvdH, pvdA, and pvdF) are involved in the generation of precursor and alternate amino acids necessary for various portions of the molecule. Several others (e.g., pvdI, and pvdJ) are directly responsible for "stitching" together the peptide chain. pvdD terminates the chain and releases the precursor into the cytoplasm, which is consistent with identification of pyoverdine-like molecules in the cytoplasm with incompletely matured chromophores.
=== Brand names === Oxazepam is marketed under many brand names worldwide, including: Alepam, Alepan, Anoxa, Anxiolit, Comedormir, durazepam, Medopam, Murelax, Nozepam, Noripam, Oksazepam, Opamox, Ox-Pam, Oxa-CT, Oxabenz, Oxamin, Oxapam, Oxapax, Oxascand, Oxaze, Oxazepam, Oxazépam, Oxazin, Oxepam, Praxiten, Purata, Selars, Serax, Serepax, Seresta, Séresta, Serenid, Serpax, Sobril, Delipam, Tazepam, Vaben, and Youfei. It is also marketed in combination with hyoscine as Novalona and in combination with alanine as Pausafrent T.
Sources: en.wikipedia.org
=== Economics === In the UK, trastuzumab emtansine was not recommended for use by the National Health Service by advisory body NICE, reportedly because an acceptable pricing agreement could not be reached with Roche. Originally it cost £5,900 a month. and NICE estimated it cost £166,000 per QALY (well over the usual maximum). It has been funded by the English NHS Cancer Drugs Fund but in January 2015 it was proposed to remove it from the approved list. After a secret discount was agreed by Roche the Cancer Drugs Fund will continue to fund it. In June 2017, the NHS Confederation and NHS Chief Executive Simon Stevens announced that the NHS would be offering trastuzumab emtansine to a limited number of women after striking a deal with Roche on the price.
=== Fatty Acid Synthesis === Fatty acid synthesis begins in the cytosol. During the first reaction, irreversible carboxylation of acetyl-CoA to malonyl-CoA is catalyzed by the biotin-dependent enzyme acetyl-CoA carboxylase (ACC). Notably, the conversion of acetyl-CoA to malonyl-CoA is the rate-limiting step of fatty acid synthesis. Acetyl-CoA carboxylase (ACC) thus represents the rate-limiting enzyme in fatty acid synthesis; ACC activity is stimulated by increasing concentrations of cytosolic citrate, and inhibited by increasing concentrations of the fatty acid palmitate. After malonyl-CoA becomes available by virtue of ACC, fatty acid synthase (FAS) is then able to complete a series of reactions to form the 16-carbon molecule palmitate. FAS is a complex, multifunctional protein containing seven different catalytic sites: acetyl transacylase, malonyl transacylase, β-ketoacyl synthase, β-ketoacyl carrier protein (ACP) reductase, 3-hydroxyacyl-ACP dehydratase, enoyl-ACP reductase, and thioesterase. These different enzymes are covalently linked within the FAS complex, allowing for intermediates to be handled efficiently from one active site to another without leaving the assembly. After the completion of the first reaction by ACC, fatty acid synthesis thus continues on the FAS complex. During the second reaction of fatty acid synthesis, acetyl transacylase and malonyl transacylase catalyze the formation of acetyl-ACP and malonyl-ACP, respectively.
== See also == Oxides, e.g., Al2O3, CaO, Fe2O3, MgO, MnO, P2O5, K2O, SiO2 Carbonates: Na2CO3 (soda ash), K2CO3 (potash) Bicarbonates, e.g., NaHCO3 (baking soda) Sulfates: sulfate ash, according to Ph. Eur. Inductively coupled plasma emission spectrometry Atomic absorption spectroscopy
Lord Nelson (1758–1805) was preserved for two months in brandy and spirits of wine mixed with camphor and myrrh after which time the body was found to be in excellent condition and completely plastic. Various communist leaders have been embalmed and put on public display. Perhaps the most famous embalmed body of the 20th century is that of Vladimir Lenin, which continues to draw crowds decades after his death in 1924, and is seen in his Moscow mausoleum. Joseph Stalin was also embalmed and placed next to Lenin, but his body was buried in 1961 during de-Stalinization. Klement Gottwald of Czechoslovakia, who died just five days after attending Stalin's funeral, was embalmed and displayed in a mausoleum at National Monument in Vitkov in Prague. However, in 1962 due to political reasons, the body was removed and cremated. Bulgarian Georgi Dimitrov was embalmed and placed on display in the Sofia Georgi Dimitrov Mausoleum. After the fall of Communism in Bulgaria, his body was buried in 1990 in the Central cemetery of Sofia. Mongolia's Khorloogiin Choibalsan, Angola's Agostinho Neto, Romania's Gheorghe Gheorghiu-Dej and Guyana's Forbes Burnham were also embalmed by the same Russian team. Currently, embalmed communist leaders can also be found in the Mausoleum of Mao Zedong, the Ho Chi Minh Mausoleum, and the Kumsusan Palace of the Sun for Kim Il Sung and Kim Jong Il.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.
Lowering pressure reduces the boiling point of water and allows ice to sublimate at temperatures below freezing. Vacuum also limits convective heat transfer, so heat is usually supplied by shelves or radiation. The pressure must stay below the vapor pressure of ice at the product temperature.
The cycle typically includes freezing, primary drying, and secondary drying. Freezing solidifies water and sets the pore structure; primary drying removes bulk ice; secondary drying removes bound water. Some cycles add annealing or pre-freezing steps.
Yes. Lyophilization and freeze-drying are synonyms for the same vacuum-assisted sublimation process. The term lyophilization is more common in pharmaceutical and laboratory settings, while freeze-drying is widely used in food and general contexts.