China 
Africa 
Explore chapters and articles related to this topic
Flow visualization methods and their application in electronic systems
Published in Kaveh Azar, in Electronic Cooling, 2020
A technique that allows the precise measurement of small fluid velocities (0 to 5 cm/s) while permitting visualization in three-dimensional flow fields uses a pH indicator and is applicable to aqueous solutions (Baker, 1966). The method consists of placing two electrodes in a solution of thymol blue which has been titrated to the end point (pH ≈ 8). Thymol blue changes color from blue to yellow as it goes from basic to acidic form. A DC voltage is impressed between the electrodes, the positive one of which is a fine wire (diameter ≤0.05 mm) placed in the region of measurement. The resulting current flow induces a proton transfer reaction near the wire, with an attendant change in the color of the solution. If the voltage is pulsed, a small cylinder of colored solution forms around the wire and then moves away from the wire with the fluid, forming a neutrally buoyant marker Eventually, the lower pH of the fluid far from the wire will cause the color to disappear; thus the solution may be used indefinitely A network of wires placed in the fluid and pulsed permits the visualization and measurement of a three-dimensional flow field. The negative electrode is a conducting plate placed away from the region of interest. It is important to keep the voltages low in order to avoid the production of hydrogen bubbles at the wire (a typical voltage for an electrode spacing of 0.5 cm is 5 V DC at a current flow of 5 mA).
Special Flows
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2020
In the rotating tank experiment, dyes like potassium permanganate or ink after dissolving in water, stain the entire mass. This calls for a fresh charge of water for each experiment. This could be avoided by using a dye whose color changes with the pH value of the water. Thymol blue is the most suitable dye for this purpose. A solution of thymol blue is orange in color when acidic and violet when alkaline. Before starting the experiment, add a little quantity (say 10 mg) of thymol blue crystals in water and allow it to dissolve. Few drops of dilute nitric acid or sulphuric acid will turn the entire water orange in color. Whenever the flow patterns have to be observed, inject some liquid ammonia with a fine glass tube. The color of the water will locally change to violet. After the experiment is over, the water can be changed to nearly clear condition by adding a few drops of acid. Thymol blue dissolves easily in alcohol without leaving any sediment. Therefore, it may be dissolved in a small quantity of alcohol before adding it to the rotating tank.
Special Flows
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2016
In the rotating tank experiment, dyes like potassium permanganate or ink after dissolving in water, stain the entire mass. This calls for a fresh charge of water for each experiment. This could be avoided by using a dye whose color changes with the pH value of the water. Thymol blue is the most suitable dye for this purpose. A solution of thymol blue is orange in color when acidic and violet when alkaline. Before starting the experiment, add a little quantity (say 10 mg) of thymol blue crystals in water and allow it to dissolve. Few drops of dilute nitric acid or sulphuric acid will turn the entire water orange in color. Whenever the flow patterns have to be observed, inject some liquid ammonia with a fine glass tube. The color of the water will locally change to violet. After the experiment is over, the water can be changed to nearly clear condition by adding a few drops of acid. Thymol blue dissolves easily in alcohol without leaving any sediment. Therefore, it may be dissolved in a small quantity of alcohol before adding it to the rotating tank.
Applications of aged powders of spray-dried whey protein isolate and ascorbic acid in the field of food safety
Published in Drying Technology, 2023
Chao Zhong, Songwen Tan, Zelin Zhou, Xia Zhong, Timothy Langrish
Compared with spray-dried WPI and AA powders or their solutions, an indicator label is relatively easy to carry and use under different conditions. This pH indicator label was produced by the method described in Section 2.6. The pH indicator label has the advantage of not degrading quickly due to microbiological action. In contrast, the corresponding solution may degrade due to microbiological changes over the time scale of days. Figure 11 shows the color changes of the indicator labels at different pHs, which can help to determine the acidity or alkalinity of unknown solutions by visual observation. These solutions may include any drinks or any water in the natural environment. The indicator label may be safer, compared with most pH test papers, such as thymol blue, methyl orange or methyl red, which include toxic chemicals. This new pH indicator is simple, rapid, low-cost and has relatively low safety impacts on human health or the environment.
Anaerobic biodegradability test for Lantana camara to optimize the appropriate food to microorganism (F/M) ratio
Published in Environmental Technology, 2020
Biswanath Saha, Arun Sathyan, Ajay S. Kalamdhad, Meena Khwairakpam
Different parameters were tested at an interval of every seven days i.e. volatile solids (VS), total solids (TS), moisture content (MS), and soluble chemical oxygen demand (sCOD). APHA [26] technique was used for the analysis of VS and sCOD. Volatile fatty acid (VFA) was examined directly through titration method [27]. For the preparation of sCOD and VFA, 5 g of sample was mixed uniformly and the volume was made up to 100 mL with distilled water. The sample was kept in a horizontal shaker for 2 h at 150 rpm and then the sample was filtered. After filtration, the sample was analyzed. Methane production was measured daily by water displacement method as shown in Figure 1a. 1.5 N NaOH was used in place of water so that CO2 produced can separate from methane [28]. This is due to the reaction taking place between CO2 and NaOH to form sodium carbonate. Alkali indicator thymol blue was added. The methane generated in the batch reactor passed through the bottle filled with NaOH. The passage of methane to NaOH bottle generates a pressure due to which aOH is displaced drop by drop and this NaOH is collected in a beaker and measured in a measuring cylinder [13]. Amount of NaOH displaced signifies the amount of methane produced and carbon dioxide reacts with NaOH to form sodium bicarbonate [19].
Review of pH sensing materials from macro- to nano-scale: Recent developments and examples of seawater applications
Published in Critical Reviews in Environmental Science and Technology, 2022
Roberto Avolio, Anita Grozdanov, Maurizio Avella, John Barton, Mariacristina Cocca, Francesca De Falco, Aleksandar T. Dimitrov, Maria Emanuela Errico, Pablo Fanjul-Bolado, Gennaro Gentile, Perica Paunovic, Alberto Ribotti, Paolo Magni
Based on this principle, spectrophotometric methods for pH measurement, reaching an accuracy as high as 0.001, have been developed using different indicators such as m-cresol purple, cresol red, bromocresol green, bromocresol purple and thymol blue (King & Kester, 1989; Millero et al., 2009). A schematic example of automated spectrophotometric pH system is reported in Figure 1. Once calibrated, these devices do not need to be recalibrated for use at sea. A description of a spectrophotometric pH sensor designed for in situ measurements can be found in Cullison Gray et al. (2011) and in Lai et al. (2018).