Specific Temperature Difference Research Articles

Influences of Average Temperature Difference and Measurement Period on Estimation of In Situ Thermal Transmittance of Building Exterior Walls Using the Average Method of ISO 9869-1

Many studies have sought to overcome the two main limitations of the average method of ISO 9869-1—its long test duration and low accuracy. These studies reported that the reliability of the results is dependent on the temperature differences. This consensus was based on the results of studies that measured a few cases with specific temperature differences, and the convergence criteria utilized for the representative thermal transmittance (U-value) were rarely examined. This study analyzed the influence of the average temperature difference and test duration on the convergence characteristics and accuracy of U-value estimation using the average method. Data from a north-facing exterior wall with a theoretical U-value of 0.145 W/m2·K were measured between June 2022 and May 2023. The influences of different measurement conditions were analyzed for cases divided based on four measurement periods and 11 average air temperature differences. The findings show that an accurate U-value can be obtained from 7 days’ worth of measurement data with an average temperature difference of 10 °C or higher and that the improvement in accuracy is minimal under stricter conditions. To achieve a convergence probability of over 90% for temperature differences of 10 °C or greater, the second and third criteria required measurement periods of 7 and 15 days respectively.

Modeling of inhomogeneous heating behavior in ultrafast laser interaction with dielectric–dielectric nanocomposite with band gap contrast

Inspired by the optical data storage and photothermal therapy applications of metal–dielectric nanocomposite materials relying on the difference in laser absorption mechanism between metal and dielectric, the ultrashort single pulse laser irradiation of zirconia–alumina nanocomposite, a dielectric–dielectric nanocomposite with band gap contrast, was investigated. A femtosecond (fs) laser of 250 fs pulse duration and 10 W maximum average power was used for the experiment. A seemingly unusual phase melting phenomenon - whereby the higher melting point zirconia phase (2715 °C) was melted, while the lower melting point alumina phase (2072 °C) remained intact - was observed, thereby suggesting a huge temperature heterogeneity in the composite under ultrashort single pulse laser irradiation. Theoretical modeling indicates that the material band gap plays a significant role in laser energy absorption under an intense laser field. A sharp increase in the total absorbed laser energy and concomitant temperature increase around the laser ablation threshold was revealed. Under appropriate laser fluence, the smaller band gap zirconia phase (5.8 eV) can absorb much more laser energy than the alumina phase (8.8 eV), resulting in a remarkable temperature difference between these two phases. This research demonstrates the capability of generating huge phase specific temperature differences in composite nanostructures composed of phases with band gap contrast by using ultrashort pulsed laser irradiation.

Influence of the aperture area on the performance of a solar funnel cooker operating at high sun elevations using glycerine as load

Five funnel solar cookers have been tested to investigate the influence of the aperture area on their performance. The largest cooker had an aperture area of 0.5 m2 and it was tested side by side with two other two smaller cookers. Each cooker was tested with the same amount of glycerine.The linear performance curves relating the efficiency with the specific temperature difference was determined. Then, the determined regressions of the cooker opto-thermal ratio and the reference time on the aperture area were used to predict: i) the influence of the solar irradiance and the aperture area on the maximum temperature achieved by the load, ii) the time duration required for achieving load temperature from 65 to 140 °C, and iii) the power of the cooker. It was found that for a solar irradiance range of 600–1100 W m−2, the pasteurization temperature can be achieved even by the smallest cooker, and the efficiency of the largest cooker is close to the efficiency of a cooker with optimum aperture area. Moreover, when using the largest cooker, under an irradiance of 1100 W m−2 and ambient temperature 20 °C, the load can achieve 180 °C, implying that frying is possible.

HYBRID TEG SYSTEM FOR INDUSTRIAL AND AIR CONDITIONING APPLICATIONS

A new system to generate electric energy using thermoelectric generators (TEG’s) based on Peltier cells has been conceived, designed and built. The system consists of a Peltier cell assembly installed in a replica of an air conditioning circuit to benefit from hot and cold air flow to generate the appropriate temperature gradient. The new system has been characterized using a group of Peltier cells mounted on a dual thermostatic chamber where cold air from air conditioning equip and hot air coming from an industrial heater are flowing through independent half-chambers. The two half-chambers are separated by an insulation wall where Peltier cells have been inserted. Temperature difference between hot and cold air flow is used by the Peltier cells to generate a voltage and current using the Seebeck effect. Peltier cells are connected in series and parallel to increase voltage and current to obtain appropriate values compatibles with external applications. Experimental tests have been developed to characterize the new design obtaining electric current and voltage, thus power, from the Peltier cell assembly. The amount of power is proportional to the temperature difference between hot and cold side of the chamber through an exponential evolution with maximum performance for specific temperature difference. Power density of the TEG has been found of 2.5x10 4 W/m 2 for a temperature difference of 160º C. TEG assembly generates a current of 8 A and 5 VDC voltage at the peak power point. The system has been tested at temperature differences compatible with those created in air conditioning ducts to recreate a real situation. Power generation for set up conditions of 50º C at the hot side and 5º C at the cold one, like in conventional air conditioning ducts, has been found of very low value because of the low temperature difference. However, when using industrial conditions with hot temperature in the range 100º C to 130º C and cold temperature between -30º C and 0º C, the power generation has increased significantly, showing the critical influence of the temperature difference. The simulation analysis indicates that the new design is capable of generating enough power to cover energy demand in residential buildings.

An Experimental Method for Fast Evaluating Thermoelectric Generators Using One Pair of P- and N-Type Legs

Abstract Thermoelectric generators (TEGs) are widely used in many industries. The voltage and output power of TEG chips are critical indicators to evaluate the performance of TEGs. The conventional method is to directly test the output voltage and power of the whole TEG chip that contains 127 pairs of P- and N-type (PN) legs (127-PN-TEG). However, the assembling of these PN legs is very time-consuming. In order to reduce experimental time and the consumption of TEG materials, we proposed an experimental method. We developed the test apparatus for the rapid evaluation of TEG performance using a TEG chip with a single pair of PN legs (1-PN-TEG). We made several 1-PN-TEGs and 127-PN-TEGs using the same thermoelectric material (bismuth telluride). We then measured the voltage and the power of these 1-PN-TEGs and 127-PN-TEGs, respectively. The experimental results were compared and analyzed. The comparison showed that the voltage of 127-PN-TEG is equal to the voltage of 1-PN-TEG times 127, which implies that we could use the test data of 1-PN-TEG to evaluate the performance of 127-PN-TEG. Using the experimental device developed in this paper, we also studied the effects of the PN leg area (cross-sectional area of PN legs) and the pressure applied over the TEGs on the output power of 1-PN-TEG. The experimental results showed that the power per unit area decreases with an increase in the 1-PN-TEG's PN leg area when the temperature difference between the hot and cold sides was constant. Under specific temperature difference conditions, the open-circuit voltage and the output power will increase with the pressure applied on the TEG chips.

Study on the influence of temperature differences in the tunnel on ventilation system energy consumption

The formula of the atmospheric pressure difference caused by the temperature difference in the tunnel and the environment outside the tunnel was established in this paper based on the Clapeyron equation to study the influence of the temperature difference between inside and outside the tunnel on the energy consumption of the ventilation system. Then, a scaled-down model tunnel is established. The air inside the model is heated by electric heating, the temperature and velocity of airflow along the center of the tunnel model are measured in detail, and the atmospheric pressure difference and wind speed in the model tunnel with different slopes are discussed. The results indicate that the tunnel has an obvious natural ventilation effect under specific temperature difference between inside and outside, and it becomes better as the slope increases. The shaft-type natural ventilation can promote the overall tunnel ventilation, and making full use of natural wind can save 15% of the energy consumption of mechanical ventilation.

A novel optimization method for thermoelectric module used in waste heat recovery

When recycling fluid waste heat with thermoelectric devices, the current generated by the thermoelectric module is limited by the minimum current among the thermoelectric legs, which results in electric power losses. To address this issue, a novel optimization method for thermoelectric module structures is first proposed, wherein the length of the thermoelectric legs is determined by their specific temperature differences. Additionally, a fluid-thermal-electric multiphysics model is developed to predict the behaviour of an air-to-water thermoelectric generator system. To reduce the workload, a simplified thermoelectric module is used to conduct the optimization. The results indicate that the fluid-thermal-electric multiphysics model can determine the temperature distributions and voltage distributions of the thermoelectric generator system with acceptable accuracy. The proposed optimization method can effectively improve the output performance of the thermoelectric module. Despite using the same amount of thermoelectric materials, the novel thermoelectric module exhibits a higher output power than the base thermoelectric module structure whenΔl ≤ 0.03 mm, and the optimal value of Δl is approximately 0.01 mm for the simplified thermoelectric module. In addition, if the thermoelectric module contains a greater number of thermoelectric legs, the optimization method will provide greater performance enhancements. The proposed optimization method contributes to enhancing the output performance of thermoelectric modules used for fluid waste heat recovery.

Automatic detection of risk zones in diabetic foot soles by processing thermographic images taken in an uncontrolled environment

Diabetes mellitus has become a global healthcare issue with incidence levels growing exponentially each year. Diabetic foot is one of the complications related with the ailment, and if it is not attended in time, it can progressively deteriorate to a condition that necessitates foot amputation. This study aimed to establish a non-invasive monitoring system for diabetic foot. This proposed system detects and classifies temperature differences in foot sole zones as ulcerous if >2.2 °C and necrotic if <−2.2 °C, by processing thermographic images of foot soles. This is achieved without homogeneous background or room temperature control. There are reports of systems that are designed to work under controlled environments; however, their performance declines or falters altogether under uncontrolled, home environments.The system proposed in this paper combines step-by-step and end-to-end algorithms that compensate for the limitations in data and, at the same time, enhance performance. It uses deep-learning techniques to segment visible-spectrum images using a retrained Mask R-CNN model, which is adjusted with 141 images to segment foot soles. These results are used over the temperature matrix in order to isolate the foot sole temperatures. The visualisation and classification methods use step-by-step algorithms with comparisons of homologous foot sole regions, convolutions with a two-dimensional (2D) Gaussian function, filters that process and compare areas of 1.5 cm2 over each foot sole, and a thermal threshold to differentiate ulcerous from necrotic zones.The results illustrated a detection accuracy of 90% for ulcers and 88% for necrosis, while the labelled areas had an error of 7.05% and 10%, respectively. These results demonstrated that the system is capable of successfully detecting and visualising the specific temperature differences over samples under an uncontrolled environment.

Wave propagation characteristics of a cylindrical laminated composite nanoshell in thermal environment based on the nonlocal strain gradient theory

In this article, the wave propagation behavior of a size-dependent laminated composite cylindrical nanoshell in a thermal environment is presented. The small-scale effects are analyzed based on nonlocal strain gradient theory (NSGT). The governing equations of the cylindrical laminated composite nanoshell in a thermal environment were obtained using Hamilton’s principle and solved by the analytical method. The novelty of this study is considering the effects of the composite layers and NSGT in addition to considering the thermal environment of the cylindrical composite nanoshell. Finally, the investigation was performed on the influence of temperature difference, wave number, angular velocity and the different types of laminated composite on the phase velocity using the mentioned continuum mechanics theory. The results show that wave number, ply angle, shear correction factor and thermal environment play an important role on the phase velocity of the laminated composite nanostructure. Another significant result is that, in a specific temperature difference, there is an inverse relation between the number of layers in a laminate and the dynamic behavior of the nanostructure. The outcome of the present work can be used in a structural health monitoring and ultrasonic inspection techniques.

Optimization design of a thermal protection structure for the solar array of stratospheric airships

Abstract Renewable power system using solar array is one of the most critical subsystems for stratospheric airships. It is important of thermal protection for the stratospheric airship, because excessive temperature of solar cell may reduce its conversion efficiency and age the envelope material underlaid solar cells. Multi-objective optimization of a thermal protection structure with heat dissipation and insulation layers for solar array of a stratospheric airship is performed in this paper. The optimization process is carried out by a Nondominated Sorting Genetic Algorithm to decrease the sensitivity toward weights or demand levels. The specific temperature difference, which indicates the ratio of temperature reduction and structure density, and the output power of solar array are used to present the optimization aims. Three geometric variables related to the number of fins, width ratio of fins and thickness ratio of dissipation and insulation layer are selected as the design variables. Pareto optimal fronts representing the trade-offs between the performance parameters are obtained at last and optimization results are compared with previous studies and the thermal protection effects and output power of the solar array are both more excellent. Furthermore, the simulation of the thermal protection structure with optimization parameters are carried out at last.

Influence of material properties and structural parameters on the performance of near-space use lightweight insulation structure

We recently developed a lightweight insulation structure (LIS) which had a high request in thermal insulation performance and structural weight and was promising to be used as the thermal control element for a near-space aircraft. In the present paper, the effects of the material properties and structural parameters on the thermal insulation performance of near-space use LIS were numerically investigated in detail. In the proposed theoretical model, the equivalent thermal conductivities and specific temperature differences of LIS were studied to make detailed thermal features clear. Compared with the experimental and previous simulation data, the theoretical model has been validated, showing a good consistency. The results showed that the thermal conductivity of insulating material had a great influence on the specific temperature difference due to its strong effect on the equivalent thermal conductivity of LIS. In addition, it can be seen that the structural parameters mainly influenced the insulation performance of LIS by changing the areal density of LIS. The results demonstrated that the theoretical model suggested a pathway towards designing the structure parameters of near-space use LIS and selecting suitable insulating materials quickly.

Thermal insulation performance of lightweight substrate for solar array on stratospheric airships

Experimental and theoretical studies are reported on the thermal insulation performance of three types of lightweight substrate for application in solar array on stratospheric airships. A concept, specific temperature difference, is proposed which expresses temperature difference of unit area density and can estimate the overall thermal insulation performance of lightweight substrate. The experimental apparatus and instrumentation have been designed and built to measure temperature difference between the upper and lower surface of the test samples under different solar radiation flux conditions. The experimental data are studied to assess thermal insulation performance of the lightweight substrates. The theoretical models of three types of insulation structures are investigated to predict the temperatures. Then, the models are verified by comparison with the experimental data. On the basis of analyzing theoretical models, the effects of two critical parameters of the heat sink substrate on thermal insulation performance are analyzed which give the most important evidences for optimizing the design of heat sink substrate. The obtained result is a valuable reference for the selection of insulation substrate of solar array on stratospheric airships.

Plasma Membrane Vesicle Critical Temperature Scales with Growth Temperature in a Zebrafish Cell Line

Giant plasma membrane vesicles (GPMVs) isolated from mammalian cell lines contain coexisting liquid phases at low temperature, a single liquid phase at elevated temperatures, and undergo robust micron-sized critical fluctuations near the miscibility transition which is typically close to room temperature. In past work, we have measured the temperature dependence of critical composition fluctuations and speculated that mammalian cells tune their membrane composition to maintain a room temperature critical point in order to experience <100nm super-critical composition fluctuations under growth conditions of 37°C [1]. Here, we present evidence that cells actively tune membrane critical temperatures (Tc) to a specific temperature difference below growth temperatures by preparing GPMVs from ZF4 cells, a zebrafish cell line that is capable of growing at temperatures ranging between 20° and 32°C. As was the case in mammalian cell lines, ZF4 cells produce GPMVs with coexisting liquid phases at low temperature and micron-sized critical fluctuations near the miscibility transition. ZF4 derived GPMVs transition temperatures shift to lower values when cells are grown at lower temperature, such that Tc was 16.8±1.2°C below growth temperatures for ZF4 cells grown between 20 and 32°C. We also examined the time-course of Tc adjustment by preparing GPMVs from cells adapted for growth at 28°C then subsequently grown at 20°C. Transition temperatures adjust with a time-constant of 1.5 days, in good correspondence with the doubling time under these growth conditions.1.S.L. Veatch, P. Cicuta, P. Sengupta, A. Honerkamp-Smith, D. Holowka, B. A. Baird. ACS Chem Biol. 2008 3(5):287-93. (2008)

Relationship between Nighttime Wind Speeds and Thermal Conditions above a Sloping Forest

Researchers have examined relationships between wind speeds and thermal conditions above a slope for pure drainage flow with nearly no disturbance by shear flow, though disturbances by shear flow are commonly present. This study examined the relationship between wind speeds and thermal conditions above a slope when wind speed is affected by shear as well as drainage flow. Data used in this study were obtained at a sloping forest site in Thailand, which had been also used in our previous studies (Komatsu et al. 2003, 2005). The canopy height (h) of the forest was approximately 30 m above ground level and wind speeds were measured at 34 m, 43 m, and 50 m (i.e., 1.13h, 1.43h, and 1.67h, respectively). After classifying measured wind speed data based on vertical air temperature differences, the mean and minimum wind speeds of each temperature-difference class were determined. Here, mean and minimum wind speeds refer to means and minimums among wind speeds for a specific temperature difference class. Regarding the 34-m wind speeds, mean wind speeds generally increased with increasing temperature difference and minimum wind speeds were non-zero, indicating the effect of drainage flow was generally dominant over the effect of shear flow at this height. Regarding the 50-m wind speeds, mean wind speeds decreased with increasing temperature difference and minimum wind speeds were nearly zero regardless of the temperature difference, indicating the effect of shear flow was dominant over the effect of drainage flow at this height. The 43-m wind speed data showed results that were intermediate to those of the 34- and 50-m wind speed data. Results of such analysis bring information on the significance of the drainage flow effect on wind speed data measured at different heights above a slope. Thus, such an analysis would be useful for examining vertical structures of wind flow above a slope when both drainage and shear flow effects are present.

Minimum temperature difference detected by the thermal radiation of objects

The spectral dependence of the Noise Equivalent Temperature Difference (NETD) that can be detected from the objects thermal radiation and is limited by photon fluctuations in quantum photodetectors is calculated. An absolute limit of its specific value (NETD∗) depends only on one physical variable—the temperature of the object T: NETD ∗ min = 5.07 × 10 −8 300 T [ K cm s 1 2 ] . This relationship shows that there is a decrease of the information capacity of thermal images with decreasing object temperature T. In the widely used thermal imagery wavelength region below 15μm the spectral dependence of a specific temperature difference caused by background fluctuations is expressed with acceptable precision by the relationship: NETD ∗ ideal (γ m ) ≈ kT 2 × D ∗ ideal (γ m ) . This is the so called “ kT 2 rule” where D∗ ideal (λ m) is the specific detectivity of an ideal photodetector with cutoff wavelength λ m) and k is Boltzmann's constant. For a particular case, considered in the Appendix, the efficiencies of thermal imagers sensitive in different spectral regions are compared, including atmospheric transmission for horizontal paths of different length.

Limiting cases of DTA curves of one-step reactions and their application to the study of complex processes

Useful relationships are discussed for DTA studies of reactions in solution which are based on two proved concepts: 1.For missing thermal feedback, i. e. linear increase of the reaction temperature, the influence of the kinetic cell constant, c, appears exclusively as a product with the specific time of the reaction, u. 2.Interference of temperature feedback by the reaction heat is considered by the ratio of the maximum temperature difference (DTA peak height) over the specific temperature difference of the reaction. This can be understood from the Semenov Theory of Thermal Ignition of Gases under Adiabatic Conditions.

Comparative study between vapor compression and multi effect boiling desalination systems

In the present study the following arrangements are considered: a- Multi effect vapor thermocompression (Fig. 1) b- Multi effect boiling (Fig. 2) c- A hybrid multi-effect boiling/vapor thermocompression. In arrangement “c” the effects operated at pressures higher than atmospheric pressure are of the vapor thermocompression type while these operated at sub atmospheric pressures are of the multi effect boiling type. Thermodynamics relations for the three systems under consideration are analysed. The numerical study includes the solution of these equations together with calculations of the heat transfer areas required for the units. The enter effect variations of the thermodynamics properties of water are accurately computed using special subroutines designed for this purpose. The present analysis starts by the arrangement “a” for which the thermodynamics representation of an effect is shown in Fig. 3. Sample of the results for the thermocompression process is presented in Fig. 4 which gives the entrainement ratio (the mass ratio of the secondary to priming steam) as a function of the temperature difference between the priming and secondary streams with the temperature difference across the evaporator condenser as a parameter. It should be realized that using an ejector to perform the compression of the entrained vapor is considered to be a low efficiency process due to irreversibilities encountered in the entrainment, mixing, and compression process. However, the advantages of using the ejector here is that it acts as a controlling device, influenced by the following parameters: 1- total temperature difference between the hot and cold ends of the plant 2- concentration ratio of the brine and its effect on the boiling point elevation 3- number of effects 4- temperature difference across the condenser evaporator units curves of Fig. 4 are used to calculate the performance ratio of the considered systems. The outcomes showed that using ejectors over the same total temperature difference would result in a reduction of the number of effects used in a conventional MEB without experiencing a proportional reduction in the plant productivity. That would lead to a reduction in the capital and running costs as far as the pumping power is concerned. For specific temperature difference, this arrangement could be benificial for small capacities since a smaller number of effects would require less maintaince and gives more stable characteristics. On the other hand, the hybrid arrangement would include the advantages of both MEB and VTC. That means less number of effects without loosing the plant's potential performance ratio. The deviding pressure line between the VTC and the MEB is chosen in such a way to avoid the interference of different ejectors, namely the driving and venting ejectors, in a subatmospheric effect.

An air-cooled solar collector using all-cylindrical elements in a low-loss body

A novel IX air-cooled solar collector has a phenolic polymer structural foam body, a black painted fiberglass mat absorber and a coplanar, parallel, close-packed array of evacuated cylindrical glass tubes for a cover. Modeling suggests, and measurements confirm, high efficiency performance as well as a substantial dispersion of performance characteristic arranged so that the specific temperature difference increases as the radiant intensity decreases. This dispersion suggests greatly improved cloudy weather performance. In a steady state simulation at full sun under northern midwinter conditions this collector can deliver a minimum of 1.9 times more heat per day to Glauber's Salt storage than can a IX double glazed water-cooled collector with a non-selective black flat absorber plate. Under cloudy conditions this advantage ratio rises to 12.1 at 5 13 sun. Effective heat collection continues at intensities as low as 3 13 sun. Under summertime conditions the collector can operate an absorption air conditioner at 6 13 sun.

21. Pumps and pump fluids

In the present study the following arrangements are considered:a- Multi effect vapor thermocompression (Fig. 1)b- Multi effect boiling (Fig. 2)c- A hybrid multi-effect boiling/vapor thermocompression.In arrangement “c” the effects operated at pressures higher than atmospheric pressure are of the vapor thermocompression type while these operated at sub atmospheric pressures are of the multi effect boiling type.Thermodynamics relations for the three systems under consideration are analysed. The numerical study includes the solution of these equations together with calculations of the heat transfer areas required for the units. The enter effect variations of the thermodynamics properties of water are accurately computed using special subroutines designed for this purpose.The present analysis starts by the arrangement “a” for which the thermodynamics representation of an effect is shown in Fig. 3. Sample of the results for the thermocompression process is presented in Fig. 4 which gives the entrainement ratio (the mass ratio of the secondary to priming steam) as a function of the temperature difference between the priming and secondary streams with the temperature difference across the evaporator condenser as a parameter.It should be realized that using an ejector to perform the compression of the entrained vapor is considered to be a low efficiency process due to irreversibilities encountered in the entrainment, mixing, and compression process. However, the advantages of using the ejector here is that it acts as a controlling device, influenced by the following parameters:1- total temperature difference between the hot and cold ends of the plant2- concentration ratio of the brine and its effect on the boiling point elevation3- number of effects4- temperature difference across the condenser evaporator unitscurves of Fig. 4 are used to calculate the performance ratio of the considered systems. The outcomes showed that using ejectors over the same total temperature difference would result in a reduction of the number of effects used in a conventional MEB without experiencing a proportional reduction in the plant productivity. That would lead to a reduction in the capital and running costs as far as the pumping power is concerned. For specific temperature difference, this arrangement could be benificial for small capacities since a smaller number of effects would require less maintaince and gives more stable characteristics.On the other hand, the hybrid arrangement would include the advantages of both MEB and VTC. That means less number of effects without loosing the plant's potential performance ratio. The deviding pressure line between the VTC and the MEB is chosen in such a way to avoid the interference of different ejectors, namely the driving and venting ejectors, in a subatmospheric effect.

Effect of Electrolytes upon Kahn Precipitates from Human and Animal Sera

The problems created by the existence of falsely positive serologic reactions have been a source of difficulty since the advent of the Wassermann test. Kahn reported the first satisfactory differential test; this was based upon specific temperature differences. We became interested in determining whether or not reactions in human and animal sera could be distinguished by the effect of electrolytes. Animal sera were used in these studies because they give general biologic reactions which are apparently of the same type as those found in human falsely positive serologic reactions., while studying the effect of Nacl solutions upon the Kahn Precipitates from animal sera, it was observed that the precipitate resulting from the reaction of Kahn antigen and horse serum was soluble in 4% NaCl solution. At the same salt concentration, precipitates from syphilitic human sera remain insoluble. The effect of other concentrations of NaCl (ranging from 0% to 30%) upon horse, human, guinea pig, hog, cow, sheep, and chicken sera were investigated. All sera were diluted to give approximately two plus reactions in the standard Kahn test by a method previously described. Verification tests were made upon each serum to check the specificity of the reaction. All sera gave the expected reactions (i.e., either syphilitic, general biologic, or negative type) with this test. Controls were also made using the same quantities of serum and salt solution. However, an artificial antigen containing the same quantities of alcohol and saline as in the original antigen was used. Control reactions were completely negative except in the chicken sera. It was found that each species of animal serum investigated gave characteristic aggregation and dispersion patterns of the Kahn precipitate.