Fact-checked by Grok 2 weeks ago

Cloud point

The cloud point is the temperature at which a binary or multicomponent mixture in the isobaric temperature-composition plane first exhibits a decrease in transparency due to the appearance of turbidity from phase separation.^[1] This phenomenon is characterized by the initial onset of cloudiness or haziness and can be induced by changes in temperature or composition, with the exact temperature influenced by factors such as heating or cooling rates.^[1] In physical chemistry, the cloud point is particularly significant for aqueous solutions of nonionic surfactants, where it marks the temperature above which the solution undergoes liquid-liquid phase separation, forming a surfactant-rich phase and a dilute aqueous phase that renders the mixture turbid.^[2] For polyoxyethylene-based nonionic surfactants, this occurs as dehydration of the hydrophilic chains reduces solubility with increasing temperature, typically resulting in an upper cloud point upon heating.^[3] This property serves as a key quality control parameter for water-soluble surfactants in emulsions and dispersions, influencing their stability and performance in formulations.^[4] The cloud point also finds applications in analytical techniques, such as cloud point extraction (CPE), an environmentally friendly method for separating and preconcentrating analytes from aqueous samples using nonionic surfactants without organic solvents.^[5] In this process, the surfactant solution is heated to its cloud point to form micelles that partition hydrophobic species, enabling efficient isolation for subsequent analysis.^[6] Additionally, in the petroleum industry, the cloud point of diesel fuels and other products is defined as the temperature at which a haze of wax crystals first becomes apparent upon cooling, causing visible cloudiness and indicating potential operability limits in cold conditions.^[7] This measurement, standardized by methods like ASTM D5772, helps predict fuel flow issues and guides additive use to improve low-temperature performance.^[8]

Fundamentals

Definition

The cloud point is the temperature at which a solution or liquid mixture begins to exhibit turbidity or cloudiness due to the formation of a dispersed second phase, such as crystals, micelles, or emulsions. This phase transition typically occurs upon cooling or heating, depending on the system, and marks the onset of incomplete miscibility between components. In chemical contexts, it serves as a critical indicator of stability limits in mixtures like fuels, oils, and aqueous surfactant solutions.^[1] Unlike the pour point, which represents the lowest temperature at which a liquid can still flow under prescribed test conditions due to increased viscosity from solidified components, or the freezing point, which denotes the temperature of complete solidification into a homogeneous solid phase, the cloud point specifically signals the initial formation of heterogeneous structures without full cessation of flow or solidification. For instance, in petroleum-derived liquids, this initial separation often involves wax crystals, while in surfactant systems, it may involve micelle aggregation leading to phase splitting.^[9] The term "cloud point" originated in early 20th-century petroleum chemistry to characterize the temperature at which haze from wax precipitation first appears in hydrocarbon mixtures, as traditionally defined in standards like ASTM D2500. The concept has been applied to surfactant science, where it describes the upper consolute temperature for aqueous solutions of nonionic surfactants prone to liquid-liquid phase separation.

Physical Mechanisms

In systems exhibiting lower critical solution temperature (LCST) behavior, such as aqueous solutions of nonionic surfactants, the cloud point marks the temperature above which the solubility diminishes with increasing temperature, resulting in liquid-liquid phase separation. This counterintuitive temperature dependence arises from thermodynamic principles where the Gibbs free energy of mixing becomes positive due to an unfavorable entropy contribution outweighing the enthalpic gains from interactions like hydrogen bonding. In aqueous systems, this is often mediated by the disruption of hydrogen bonds between solute and solvent at elevated temperatures, coupled with enhanced hydrophobic interactions that favor solute aggregation over solvation.^[10] Cloud points can be classified as upper (upon heating, typically LCST liquid-liquid demixing) or lower (upon cooling, often solid-liquid separation). In crystal-forming systems like petroleum products, the lower cloud point corresponds to the initiation of nucleation in supersaturated solutions, where solute molecules—such as paraffin-like hydrocarbons—begin to organize into ordered crystal lattices upon cooling below the saturation temperature. This process involves the formation of critical nuclei that overcome the energy barrier for crystallization, followed by growth through the attachment of additional molecules to the crystal surfaces, leading to visible turbidity as solid phases emerge from the liquid. Supersaturation, achieved by temperature reduction, drives this metastable-to-stable transition, with the rate of nucleation increasing exponentially near the cloud point.^[11]^[12] In micellar systems with non-ionic surfactants, the upper cloud point arises from the progressive dehydration of hydrophilic polymer chains, such as polyoxyethylene segments, as temperature rises and weakens the hydrogen bonds sustaining their hydration shells. This reduced solvation exposes hydrophobic moieties, promoting inter-micellar attractions and the coalescence of individual micelles into larger aggregates or networks, which scatter light and induce macroscopic phase separation into dilute and concentrated phases. The entropy gain from releasing structured water molecules around the chains further favors this aggregation over dispersed states.^[13]^[14] The temperature-dependent miscibility underlying these mechanisms is captured by the Flory-Huggins theory of polymer-solvent interactions, which models the free energy of mixing via the Flory-Huggins interaction parameter \chi. This parameter determines phase stability, with demixing occurring when \chi > 0.5 for binary systems. Its basic temperature dependence is expressed as

\chi = \frac{\Delta H - T \Delta S}{RT},

where \Delta H and \Delta S represent the enthalpic and entropic contributions to mixing, T is the absolute temperature, and R is the gas constant; as T increases, the entropic term -T \Delta S can render \chi sufficiently large to destabilize the homogeneous phase, aligning with LCST-type transitions in polymer-like surfactant systems.^[15]

Industrial Applications

In Petroleum Products

In petroleum products, the cloud point serves as a critical indicator of low-temperature performance for fuels like diesel and biodiesel, marking the onset of wax precipitation that can lead to fuel filter clogging and engine failure in cold conditions. For conventional diesel fuel, this precipitation occurs when paraffin waxes begin to crystallize as temperatures drop below the cloud point, typically ranging from -10°C for winter-grade formulations to 10°C for summer grades, ensuring reliable operability across seasonal climates. In biodiesel, derived from vegetable oils or animal fats, the cloud point is often higher—around 0°C to 5°C for common feedstocks like soybean oil—due to the presence of saturated fatty acid methyl esters that form biowax crystals more readily, exacerbating cold flow issues in blends with petroleum diesel.^[8]^[16]^[17] Standards such as ASTM D2500 and its equivalent IP 219 define the manual test method for determining cloud point in these products, providing the basis for regulatory limits in major markets. In the United States, ASTM D975 for diesel fuel implies seasonal cloud point controls through operability requirements, while biodiesel under ASTM D6751 lacks a direct cloud point specification but emphasizes cold soak filterability to mitigate related risks. European specifications under EN 590 mandate maximum cloud points varying by climate class, such as ≤ +3°C for summer diesel and ≤ -10°C for winter grades in milder regions, extending to ≤ -34°C in arctic conditions to prevent precipitation during transport and use. These standards ensure fuels meet performance thresholds, with biodiesel blends (e.g., B7) required to align with diesel limits under EN 14214. As of 2022, ASTM D975 includes updated provisions for renewable diesel blends to address cold flow properties.^[18]^[19]^[20]^[21] A high cloud point in diesel and biodiesel carries significant economic and safety implications, particularly following the 2000s biofuel mandates like the U.S. Renewable Fuel Standard and EU Renewable Energy Directive, which boosted biodiesel adoption and highlighted cold-weather vulnerabilities. Precipitation can cause fuel gelling, leading to stalled vehicles, emergency towing, and repair costs, as well as safety risks including stranded motorists in remote or harsh conditions, potential accidents from power loss, and broader supply chain disruptions in cold climates, underscoring the need for seasonal formulations or pour point depressants to maintain flow. For instance, untreated biodiesel blends may fail at temperatures 10–15°C above their cloud point, increasing additive demands and blending expenses for refiners.^[17]^[22] Compared to other fuels, heating oils—similar to No. 2 diesel—exhibit higher cloud points around 0°C to 5°C, tolerable in stationary heating systems but still requiring winterization to avoid line blockages. In contrast, aviation kerosene (Jet A fuel) prioritizes freeze point stability (maximum -40°C), with typical cloud points below -20°C, to prevent solidification at high-altitude cruising temperatures.^[23]^[8]^[24]

In Surfactants and Detergents

In non-ionic surfactants, the cloud point represents the temperature at which ethoxylated chains lose hydration, leading to dehydration of the hydrophilic polyoxyethylene head groups and subsequent lower consolute solution temperature (LCST) phase separation into a surfactant-rich phase and a dilute aqueous phase.^[25] This phenomenon arises from the reduced solubility of the surfactant as thermal energy disrupts hydrogen bonding between the ethylene oxide units and water molecules, causing micelle aggregation and turbidity.^[26] The cloud point typically ranges from 0°C to 100°C, directly influenced by the ethylene oxide content, where higher degrees of ethoxylation increase the cloud point by enhancing hydrophilicity and water solubility.^[26] In detergent formulations, the cloud point determines the maximum operating temperature for effective performance in laundry and dishwashing applications, as exceeding it results in phase separation that reduces cleaning efficacy and stability.^[3] Higher cloud points above 60°C are preferred for products intended for hot-water washing, ensuring the surfactant remains soluble and active during typical household cycles up to 60–90°C, thereby maintaining detergency and preventing precipitation.^[27] For instance, in automatic dishwashing detergents, surfactants with cloud points in the 20–70°C range are selected to balance low-foaming properties with soil removal under varying water temperatures.^[28] Formulation strategies often involve polyethoxylated alcohols, such as linear C12E6 (dodecaoxyethylene monododecyl ether), which exhibits a cloud point around 57°C, allowing control over solubility and phase behavior in aqueous systems.^[29] Branched variants of these alcohols provide greater tunability, as the branching in the hydrophobic tail alters packing and hydration, enabling adjustment of the cloud point for specific temperature requirements without compromising micellar stability. Environmental considerations have driven the adoption of biodegradable non-ionic surfactants like alkyl polyglycosides (APGs), derived from renewable glucose and fatty alcohols, which emerged prominently in the 1990s amid green chemistry initiatives to replace less sustainable ethoxylates.^[30] In APGs, the cloud point is modulated by the sugar chain length, with longer glycoside units (e.g., average degree of polymerization 1.4–5) increasing hydrophilicity and often resulting in higher or absent cloud points, promoting better cold-water solubility and ultimate biodegradability into non-toxic components.^[31]^[32] This shift supports eco-friendly detergent designs that minimize aquatic impact while preserving performance.^[33]

In Extraction Techniques

Cloud point extraction (CPE) is a separation technique that employs non-ionic or mixed surfactants to partition target analytes, including metal ions and organic compounds, into a compact surfactant-rich phase when the solution is heated above the cloud point temperature, thereby enabling efficient recovery from aqueous matrices. This method leverages the temperature-dependent phase behavior of surfactant solutions, where the cloud point marks the onset of phase separation, concentrating analytes for subsequent analysis or purification. The process begins with micelle formation in the aqueous phase below the cloud point, solubilizing hydrophobic or complexed analytes within the micellar cores; upon heating beyond this threshold, the solution becomes turbid, leading to rapid phase disengagement into a viscous surfactant-rich phase (typically 1-5% of the original volume) and a bulk aqueous phase, with analytes enriched in the former by factors up to 100-fold.^[34] Phase separation is often accelerated by centrifugation, followed by analyte recovery from the surfactant phase via dilution or back-extraction. In wastewater treatment applications, CPE achieves extraction efficiencies up to 99% for heavy metals such as lead and chromium, significantly reducing contaminant levels while minimizing waste generation.^[35]^[36] Introduced in the 1970s for environmental trace analysis, CPE was first detailed by Watanabe and Tanaka in 1978, who demonstrated its utility for metal ion preconcentration using polyoxyethylene surfactants.^[34] The technique gained broader adoption in the 2000s as a sustainable alternative to conventional organic solvent extraction, aligning with green chemistry principles by avoiding volatile and toxic solvents.^[37] Key advantages include the low toxicity and high recyclability of surfactants like Triton X-114 or PONPE-7.5, which can be reused multiple cycles with minimal loss of performance, reducing operational costs and environmental impact compared to methods like liquid-liquid extraction.^[38] Representative applications highlight CPE's versatility in analytical purification; for instance, it effectively preconcentrates polycyclic aromatic hydrocarbons (PAHs) from environmental waters, achieving detection limits in the parts-per-billion range for monitoring pollution. Similarly, CPE enables the enrichment of pesticide residues, such as organophosphates, from food samples like vegetables, with recovery rates exceeding 95% and enrichment factors around 50, supporting regulatory compliance in food safety assessments.^[39] The tunability of surfactant cloud points through additive selection further optimizes extraction selectivity for diverse analytes.

Measurement Methods

Manual Methods

Manual methods for determining the cloud point of petroleum products rely on visual observation of wax crystal formation during controlled cooling, with the ASTM D2500/IP 219 standard serving as the primary procedure. This method is applicable to transparent liquids, such as middle distillate fuels, that are clear in layers up to 40 mm thick and have cloud points below 49°C. The technique detects the temperature at which the first haze or cloud of wax crystals appears at the bottom of the sample, indicating the onset of phase separation.^[40] The required equipment includes a cylindrical clear glass test jar with flat bottom (outside diameter 33 to 35 mm and height 115 to 125 mm), a series of cooling baths capable of maintaining temperatures down to -60°C or lower, a high-precision thermometer (graduated in 1°C intervals), and a contrasting background such as a black-and-white printed chart for enhanced visibility. The sample volume is standardized at 40 mL to ensure consistent optical depth and thermal uniformity within the jar. This setup allows for manual control of the cooling environment while minimizing external influences like vibration or direct light.^[8]^[41]^[18] The procedure begins by heating the sample, if necessary, to at least 14°C above its expected cloud point to dissolve any existing wax, then pouring it into the test jar up to the 40 mL mark. The jar is placed in the initial cooling bath, and the assembly is observed against the background. The jar is transferred sequentially through a series of cooling baths maintained at progressively lower temperatures (such as 0°C, -18°C, -33°C, -51°C, and -69°C), achieving an approximate cooling rate of 1.5°C/min. The operator examines the sample at 1°C intervals by tilting the jar to inspect the bottom and lower walls, recording the temperature at which the first persistent cloud of wax crystals is visible; this point is confirmed by reheating and recooling if needed to verify reproducibility. The entire process typically takes 20–30 minutes per sample, depending on the cloud point temperature.^[8]^[18] For nonionic surfactants, the manual cloud point determination follows standards such as ISO 1065 or ASTM D2024, which involve preparing a dilute aqueous solution (typically 1% w/v) and heating it gradually from room temperature while observing for the onset of turbidity. The solution is stirred intermittently during heating to ensure uniformity, and the cloud point is recorded as the lowest temperature at which persistent cloudiness appears upon cooling slightly or confirming reversibility. This heating-based method reflects the upper cloud point typical for these materials.^[42]^[43] This method offers repeatability within ±2°C under ideal conditions but is susceptible to operator subjectivity in identifying the initial cloud, variations in cooling rate homogeneity, and imprecise temperature measurements, which can lead to inconsistencies across laboratories. Due to these limitations, including the labor-intensive nature and potential for human error, manual techniques like ASTM D2500 have been increasingly supplemented or replaced by automated alternatives in standards since the late 1990s, particularly for high-volume testing.^[44]^[45]

Automated Methods

Automated methods for cloud point determination rely on instrumental techniques that objectively detect phase transitions through optical changes, offering enhanced precision and efficiency over manual approaches. The primary standard, ASTM D5771, outlines an optical detection stepped cooling method for petroleum products and biodiesel fuels transparent in 40 mm layers, applicable over a temperature range of -60°C to +49°C with 0.1°C resolution.^[46] In this procedure, the sample is introduced into a test jar or flow-through cell within an automated apparatus, cooled at controlled rates via a programmable jacket, and monitored for wax crystal formation using light transmission or scattering detection.^[47] The cooling profile follows predefined steps, with jacket temperature transitions limited to 90 seconds to ensure gradual sample cooling, and the cloud point is recorded when the optical sensor first registers a signal change indicative of turbidity.^[47] Commercial equipment, such as the ISL CPP 5Gs analyzer, implements this standard using a built-in refrigeration system and photodiodes to measure light intensity variations from crystal-induced scattering, achieving sample temperature accuracy of ±0.1°C and jacket accuracy of ±0.5°C.^[48] The method's precision includes repeatability of 2.2°C and reproducibility of 3.9°C for general petroleum products, with improved values of 1.2°C and 2.7°C for biodiesel blends, surpassing manual methods like ASTM D2500 in objectivity.^[47] These analyzers often feature compact designs with microprocessor controls, enabling operation down to -95°C without external cooling fluids.^[48] For surfactants and detergents, automated adaptations focus on nephelometric detection of light scattering from micelle aggregation during temperature ramps, building on principles from ISO 1065 for non-ionic agents.^[42] Instruments like the Phase Technology 70Xi employ diffusive light scattering optics compliant with ASTM D2024, warming the sample until cloudiness appears and then cooling to measure the transition temperature where micelles separate, with a small 0.15 mL sample volume and resolution of 0.1°C.^[49] This approach achieves repeatability better than 0.5°C, detecting subtle changes in solution turbidity as non-ionic surfactants like polyethylene oxide derivatives phase-separate above their cloud point.^[49] These methods provide key advantages, including minimization of operator subjectivity, test durations of 5–10 minutes, and alignment with regulatory requirements such as EN 14214 for biodiesel, which mandates cloud point reporting and accepts automated optical techniques following updates incorporating ASTM D5771 equivalents since 2010.^[50] By standardizing detection via photodiodes or scattering sensors, they support high-throughput testing in industrial labs while maintaining traceability to international standards.^[46]

Influencing Factors

Compositional Variables

In petroleum products such as diesel fuels, the cloud point is strongly influenced by the paraffin (wax) content and the chain length of n-alkanes. Higher concentrations of paraffins, particularly those with longer carbon chains (e.g., C20 and above), elevate the cloud point because these molecules have reduced solubility at higher temperatures, leading to earlier precipitation of wax crystals. Empirical correlations, such as those relating cloud point (\theta_{cp}) to wax percentage (%wax), demonstrate this direct proportionality, where increased wax content raises \theta_{cp} by enhancing the solid-forming tendency of the mixture. For instance, the average n-alkane chain length in fuel blends contributes to higher cloud points as chain length increases, with models showing that distributions favoring longer chains shift precipitation to warmer temperatures. In surfactant solutions, particularly nonionic types like alkyl ethoxylates, the ethylene oxide (EO) to propylene oxide (PO) ratio plays a critical role in determining the cloud point. Increasing the EO content enhances hydrophilicity, thereby raising the cloud point, as each additional EO unit strengthens hydrogen bonding with water and delays phase separation. This effect is approximately linear, with studies indicating an increment of about 5–10°C per EO unit in polyethoxylated chains. Conversely, higher PO content, which introduces more hydrophobic character, lowers the cloud point by reducing overall solubility in aqueous media. Impurities and blend compositions further modulate the cloud point through specific interactions. In petroleum fuels, aromatic compounds depress the cloud point by improving the solvency of paraffins, partitioning into the liquid phase and inhibiting wax crystallization at lower temperatures. In surfactant solutions, added salts induce a salting-out effect that lowers the cloud point by dehydrating the hydrophilic EO chains, reducing micelle stability and promoting earlier phase separation; this is particularly pronounced with anions like sulfate or chloride. Quantitative models for cloud point prediction often rely on basic linear regressions tailored to composition. For nonionic surfactants, a simple form is \theta_{cp} = a + b \times ([EO](/page/EO)\ number), where a and b are empirical coefficients derived from structural data, capturing the hydrophilicity-driven increase with EO units. Similar regressions extend to petroleum blends, correlating \theta_{cp} with %wax or average n-alkane chain length for predictive tuning in formulations.

External Conditions

External conditions, such as pressure and cooling rates during measurement, significantly influence the observed cloud point in petroleum products and surfactant solutions by altering phase separation dynamics. In diesel fuels, elevated pressures, as encountered in common rail engines, can increase the cloud point by approximately 25°C compared to atmospheric conditions, as higher pressure promotes earlier wax crystallization through enhanced molecular interactions.^[51] For nonionic surfactant solutions, pressure also elevates the cloud point, with reported increases on the order of 1.05 × 10^{-7} K Pa^{-1}, attributed to enhanced hydrogen bonding between water and ether oxygens under compression.^[52] Additionally, the cooling rate during testing affects the apparent cloud point; faster rates (e.g., 0.5°C/min versus 0.1°C/min) lead to a depression of up to several degrees due to kinetic supercooling, where wax crystals or phase separation lag behind equilibrium conditions.^[53] Solvent quality, particularly water purity in surfactant systems, plays a critical role in modulating the cloud point through impurity interactions. In nonionic surfactant solutions, ionic impurities such as salts act as salting-out agents, promoting dehydration of the hydrophilic headgroups and thereby lowering the cloud point; for instance, additions of NaCl or Na₂SO₄ can reduce it by 10–20°C depending on concentration and anion type.^[54] This effect arises because electrolytes reduce the water structure around micelles, enhancing aggregation at lower temperatures.^[55] In contrast, highly pure deionized water minimizes such perturbations, yielding higher and more reproducible cloud points closer to the intrinsic value.^[56] Aging and storage conditions contribute to cloud point variations, especially in biodiesels, where oxidative degradation over time elevates the cloud point. Exposure to air, light, and moderate temperatures during storage induces peroxidation of unsaturated fatty acid chains, forming polymeric species and gums that accelerate precipitation and raise the cloud point by several degrees after months of storage, as documented in studies since 2005.^[57] This degradation is exacerbated in blends without antioxidants, leading to up to 5–10°C increases within 6–12 months under ambient conditions.^[58] Operational contexts, including altitude, introduce subtle pressure-related effects on cloud point determination, though these are generally minimal for petroleum products. At high altitudes, reduced atmospheric pressure (e.g., 0.7 bar at 3000 m) can slightly depress the cloud point in surfactant systems by 1–2°C per 10 bar decrease, as lower pressure disfavors the compact dehydrated phase.^[59] For boiling-influenced surfactant cloud points, altitude lowers the effective temperature scale due to reduced boiling points, necessitating pressure-adjusted testing protocols in elevated locations. In petroleum fuels, however, such effects are negligible compared to compositional factors, with standard measurements conducted at sea-level pressure.^[8]

References

[1]
cloud point (12241) - IUPAC
A cloud point is characterized by the first appearance of turbidity or cloudiness. A cloud point can be induced by varying temperature or composition. A cloud ...<|control11|><|separator|>
[2]
What is the cloud point in chemistry? - AAT Bioquest
Jul 16, 2018 · The cloud point is the temperature at which a nonionic surfactant starts to phase-separate. The mixture becomes cloudy as two phases begin to appear from the ...
[3]
Cloud Point - an overview | ScienceDirect Topics
Although the cloud point is defined as the dehydration of polyoxyethylene-type nonionic surfactants, anionic/cationic mixed surfactant systems are also reported ...
[4]
Cloud Point of Surfactants | METTLER TOLEDO
The cloud point is a reliable quality control parameter for water-soluble surfactants, applicable to both emulsions and dispersions.
[5]
Cloud Point Extraction - an overview | ScienceDirect Topics
Cloud point extraction refers to a technique that utilizes the property of non-ionic surfactants to form micelles and become turbid when heated to a specific ...
[6]
Cloud Point Extraction for Electroanalysis: Anodic Stripping ... - NIH
Cloud point extraction (CPE) is a well-established technique for the pre-concentration of hydrophobic species from water without the use of organic solvents.
[7]
D5772 Standard Test Method for Cloud Point of Petroleum Products ...
Jan 27, 2021 · 5.1 For petroleum products and diesel fuels, the cloud point is an index of the lowest temperature of its utility for certain applications.
[8]
Fuel Property Testing: Low Temperature Operability - DieselNet
The cloud point is defined as the temperature at which a cloud or a haze of wax crystals starts to appear in the fuel under the test conditions.
[9]
Cloud Point - an overview | ScienceDirect Topics
The cloud point is defined as the temperature at which aqueous solutions of nonionic surfactants exhibit sudden cloudiness or turbidity (Aktar et al., 2020; ...<|control11|><|separator|>
[10]
https://pubs.rsc.org/en/content/articlehtml/2023/lp/d3lp00114h
[11]
Thermoresponsive polymers with LCST transition - RSC Publishing
Aug 29, 2023 · Above LCST, hydrogen bonding with water molecules is disturbed and the intra- and intermolecular hydrophobic and hydrogen bonding interactions ...
[12]
The importance of supersaturation on determining the solid-liquid ...
Oct 15, 2017 · A supercooling is required for the onset of wax precipitation in waxy oils. · The higher the cooling rate the higher the metastable region width.
[13]
Liquid-Solid Phase Equilibria of Paraffinic Systems by DSC ...
The WAT or cloud point is the singularly most important parameter relating to wax formation [4] and it is the temperature at which waxes first crystallize from ...
[14]
Thermodynamic parameters of clouding phenomenon in nonionic ...
Hydration of oxyethylene chains decreases as the solution temperature is increased because hydrogen bonding is strongly affected by variety in temperature [9], ...Missing: dehydration | Show results with:dehydration<|separator|>
[15]
Cloud point transition in nonionic micellar solutions - ACS Publications
Altering Phase Separation in Aqueous Nonionic Surfactant Solutions by Power Ultrasound. Journal of Solution Chemistry 2013, 42 (6) , 1229-1237. https://doi ...Missing: dehydration | Show results with:dehydration
[16]
Application of a theory of polymer solutions to the cloud points of ...
Thus, the cloud point curve of nonionic surfactants has been frequently analyzed by applying the Flory–Huggins model developed for the phase separation of ...
[17]
Winter Weather and Diesel Fuel: How to Avoid a Breakdown
But, generally speaking, #2 diesel fuel has a Cloud Point from -18 to 20 degrees F. (-28 to -7 degrees C.), while #1 diesel fuel can withstand temperatures as ...Missing: economic implications 590 IP 219
[18]
biodiesel applications - Phase Technology
The cloud point for biodiesel blends is higher than it is for conventional diesel fuel, so it has a higher risk of congealing and forming wax crystals at cold ...Missing: issues | Show results with:issues
[19]
ASTM D2500 Method for Cloud Point Testing - Ayalytical
Cloud point of a petroleum product is an index of the lowest temperature at which wax crystals begin to precipitate and can create fuel flow blockage.<|control11|><|separator|>
[20]
IP 219: Petroleum products - Determination of cloud point
Determines cloud point of transparent petroleum products below 49°C, including diesel with up to 30% FAME, paraffinic diesel, and lubricants.Missing: standard | Show results with:standard
[21]
EN 590 Diesel Fuel Specifications (ULSD) - Crown Oil
Cloud point. Summer, °C, –, +3, -2. Cloud point. Winter, °C, –, -5, -10. Hydrogen, % (m/m), –, –, 12.75. Nitrogen, % (m/m), –, –, 0.01-0.05. Gross specific ...
[22]
Avoid cold-weather diesel problems - Cenex
If No. 2 diesel cools during colder, overnight temperatures, it may reach “cloud point,” when wax crystals develop in the fuel. The fuel will look cloudy ...Missing: economic 590 IP 219
[23]
https://noraweb.org/wp-content/uploads/2016/10/NORA-Silver-Chapter-2.pdf
[24]
[PDF] Chapter 2 - Heating Oil and Its Properties
Additives or kerosene are added to heating oil during the winter to ensure that it flows. Cloud point. Cloud point is the temperature at which wax crystals ...Missing: aviation | Show results with:aviation
[25]
[PDF] Thermodynamic of Clouding Behavior of Non-ionic Surfactant ...
Non-ionic surfactant solutions have the property to undergo clouding on heating, followed by phase separation into two isotropic phases [1]. This separation is ...
[26]
Effect of chemical structure on the cloud point of some new non-ionic ...
Cloud points range from 0° to 100 °C (32–212 °F), limited by the freezing and boiling points of water. Cloud point is characteristic of non-ionic surfactants.
[27]
Design and performance optimisation of detergent product ... - NIH
May 6, 2020 · The cloud point of the nonionic surfactant was set to be 20° higher than the highest washing temperature in Asia (Smulders et al., 2007) to ...Missing: points | Show results with:points
[28]
Dishwashing composition comprising high cloud point surfactants
Cleaning product for use in automatic dishwashing comprising at least one surfactant having a cloud point in the range from 20 ~C to 70 ~C.Missing: points hot
[29]
[PDF] Glycidyl methyl ether: A safer alternative to ethylene oxide for
For instance, C12E6 and C12MeGly3 are isomers, yet their cloud points are 57 °C. 227 and 8 °C, respectively. In the case of C12MeGly5, its polar head is ...Missing: variants | Show results with:variants
[30]
A review on the synthesis of bio-based surfactants using green ... - NIH
A comprehensive literature review around alkyl polyglucosides (APGs) and sucrose esters (SEs) as bio-based surfactants, through the lens of the 12 green ...Missing: cloud | Show results with:cloud
[31]
Cloud point phenomena in the phase behavior of alkyl ...
Mixed Micelles Containing Alkylglycosides: Effect of the Chain Length and the Polar Head Group. ... X‐Shaped Sugar‐Derived Emulsifiers From 'Click Chemistry ...<|control11|><|separator|>
[32]
US6117934A - Alkylpolyglycoside containing surfactant blends for ...
Preferred alkyl glycosides are alkyl glycosides of fatty alcohol mixtures having a chain length ... alkyl glycosides containing on average from 1.4 to 5 sugar ...
[33]
(PDF) Analysis of the Influence of Alkyl Polyglycoside Surfactant and ...
Aug 5, 2025 · They have green chemical characteristics of low toxicity and good biodegradability as they break down into harmless products on degradation ...
[34]
Surfactant-Mediated Extractions, Part 1: Cloud-Point Extraction
Jan 31, 2016 · Cloud-point extraction (CPE) manipulates temperature and surfactant concentration to move aqueous solutes into a micelle phase for separation.Missing: definition | Show results with:definition
[35]
Mercury‐Free Determination of Lead in Water by Cloud Point ...
Aug 7, 2025 · This corresponds to extraction efficiencies of 96% ± 4% (HNO3), 99% ± 2% (HCl), and 102% ± 2% (H2SO4). The CPE-BE extraction process exhibited ...
[36]
Cloud Point Extraction of Trivalent Chromium from Aqueous ...
The extraction yield percentage of Cr (III) ion increased from 37 to 100% at 5 mL of APDC, and from 43 to 100% at 13 mL of APDC, when using polyethylene glycol, ...
[37]
Novel, energy efficient and green cloud point extraction - NIH
Cloud point extraction (CPE) is a technique in which extraction of organic/inorganic compounds from chemical or biological systems, using benign extractants ...Key Steps In Cpe · Types Of Surfactant Micelle... · Mycotoxin Analysis
[38]
Cloud Point Extraction as an Environmentally Friendly Technique for ...
Cloud point extraction is a sample preparation technique that involves using surfactants that are not harmful to the environment.
[39]
Cloud Point Extraction of Pesticide Residues - ResearchGate
Mar 4, 2021 · An efficient and environmentally friendly analytical process based on cloud point extraction (CPE) has been developed for the determination of ...
[40]
D2500 Standard Test Method for Cloud Point of Petroleum Products ...
Mar 6, 2023 · This test method covers only petroleum products and biodiesel fuels that are transparent in layers 40 mm in thickness, and with a cloud point below 49 °C.Missing: first | Show results with:first
[41]
ASTM D97 & D2500 - Methods - Tamson Instruments
For cloud point (ASTM D2500): the specimen is cooled at a specified rate and examined periodically. The temperature at which a cloud is first observed at the ...
[42]
The Limitations of the Cloud Point Measurement Techniques and ...
Aug 5, 2025 · Cloud point measurements via ASTM-D2500 or ASTM-D3117 have been critically discussed due to imperfections in temperature homogeneity within ...
[43]
[PDF] the limitations of the cloud point measurement techniques
This method presents multiple weaknesses in what concerns the cooling rates, temperature measurements and the subjective judgement of the operator ... ASTM D2500.
[44]
D5771 Standard Test Method for Cloud Point of Petroleum Products ...
Jan 27, 2021 · 1.1 This test method covers the description of the determination of the cloud point of petroleum products and biodiesel fuels that are ...
[45]
[PDF] Cloud Point of Petroleum Products (Optical Detection Stepped ...
This test method describes an alternative procedure for the determination of cloud point of petroleum products Test Method D 2500 using an automatic apparatus.
[46]
[PDF] CPP 5Gs
CPP 5Gs Cloud & Pour Point Analyzer with built-in cooling system. Delivered complete, ready for operation, with one detection head: pour point OR cloud point.Missing: 5G | Show results with:5G
[47]
ISO 1065:1991 - Non-ionic surface-active agents obtained from ...
Determination of cloud point.Missing: nephelometric | Show results with:nephelometric
[48]
[PDF] 70Xi Series Surfactants Analyzer - Phase Technology
The 70Xi analyzer measures cloud point of surfactants, which is the temperature at which they become insoluble in water, using a quick, precise test method.Missing: nephelometric | Show results with:nephelometric
[49]
[PDF] ASTM Updates Biodiesel Specifications for Measuring Cloud Point
May 7, 2012 · ASTM D6751 is generally comparable to the European standard EN 14214. Cloud point is the temperature at which an oil or fuel, when cooled, ...
[50]
The pressure effect on the wax formation in diesel fuel
The results obtained show an increase in the diesel cloud point of about 25 °C at the operating pressure of a common rail engine.
[51]
Effects of Pressure on the Cloud Point of Nonionic Surfactant ...
The elevation of the cloud-point temperature with pressure was 1.05×10−7 and 1.09×10−7 K Pa−1 for respective surfactant. Both volume and enthalpy changes ...Missing: testing petroleum
[52]
Influence of image analysis strategy, cooling rate, and sample ...
Nov 25, 2020 · Experimental parameter variation showed a TCloud,app depression for increasing cooling rates (0.1–0.5 °C/min), and larger sample volumes (5–24 ...
[53]
Salt effect on solutions of nonionic surfactants and its influence on ...
The effect of various salts on the cloud points of nonionic surfactant solutions has been studied by turbidimetry. The elevation or depression of cloud ...
[54]
Effect of inorganic additives on solutions of nonionic surfactants VI
Electrolytes which salt octoxynol 9 out lower its cloud point, while salting-in electrolytes raise it. The observed cloud point effects are discussed according ...
[55]
Cloud Point of Non-ionic Surfactants | METTLER TOLEDO
The cloud point of a solution corresponds to the temperature above which a sample becomes turbid. This phenomenon can be observed with non-ionic surfactants in ...Missing: definition | Show results with:definition
[56]
Long-term storage stability of biodiesel and biodiesel blends
Biodiesel blends are shown to be stable for 3 years in stable storage conditions. Stability loss prior to fuel degradation can be indicated by induction time.
[57]
Oxidative stability of biodiesel: recent insights - Wiley Online Library
Oct 30, 2021 · In this review, the factors that promote this oxidation are presented, including molecular composition, metal contamination, temperature and light exposure.
[58]
Effect of pressure on the solution behavior of nonionic surfactants in ...
The cloud temperature increased and its increasing rate became smaller with increasing pressure. By considering that the cloud temperature—composition curve is ...