Ultrasonic baths

Before testing, the blades have to be painted black to ensure a symmetrical thermal radiation. Painting is done in an additional cabin. After the measurement the blades or vanes are cleaned in an ultrasonic bath. 

Two major sources of ultrasound are employed, namely ultrasonic baths and ultrasonic immersion hom probes [79, 71]- The fonuer consists of fixed-frequency transducers beneath the exterior of the bath unit filled with water in which the electrochemical cell is then fixed. Alternatively, the metal bath is coated and directly employed as electrochemical cell, but m both cases the results strongly depend on the position and design of the set-up. The ultrasonic horn transducer, on the other hand, is a transducer provided with an electrically conducting tip (often Ti6A14V), which is inuuersed in a three-electrode thenuostatted cell to a depth of 1-2 cm directly facing the electrode surface. 

Dissolve 18.2 g vanadium pentoxide in 300 ml aqueous sodium carbonate solution, (cn. co, = 1 mol/1), with heating after coohng carefully add 460 ml sulfuric acid, (ch so. = 2.5 mol/1), and make up to 11 with water. Remove excess CO2 in the ultrasonic bath [1, 3, 4]. 

However, it should be mentioned that the dissolution process of a solid, crystalline complex in an (often relatively viscous) ionic liquid can sometimes be slow. This is due to restricted mass transfer and can be speeded up either by increasing the exchange surface (ultrasonic bath) or by reducing the ionic liquid s viscosity. The latter is easily achieved by addition of small amounts of a volatile organic solvent that dissolves both the catalyst complex and the ionic liquid. As soon as the solution is homogeneous, the volatile solvent is then removed in vacuo. 

Dipping solution Dissolve O.S g p-chloranil in 90 ml ethyl acetate, cautiously make up to 100 ml with 10 ml sulfuric acid (ca. 96<9b) and homogenize for S min in the ultrasonic bath or by vigorous shaking. 

Sample solution A 3 g sample of woodruff was added to 30 ml warm methanol and placed in the ultrasonic bath for 10 min. After filtration the solution was concentrated to ca. 20% of the initial volume under reduced pressure. A portion of the solution was centrifuged at 1200 rpm for 2 min and the clear supernatant was applied to the layer as a band. 

Ultrasonication was reported for the extraction of triazines from soil, previously sieved to 2 mm and stored at -18 °C, prior to analysis using CC/NPD and CC/lTD. A 5-g soil sample was placed in a polypropylene column and extracted for 15 min with 4 mL of ethyl acetate in an ultrasonic bath at room temperature. Subsequently, the solvent was filtered and collected in a graduated tube, and the extraction was repeated for another 15-min period using a second 4-mL portion of ethyl acetate. The two extracts... 

Figure 3.5 (a) Indirect sonication using an ultrasonic bath, (b) Direct sonication using an ultrasonic horn, (c) Direct sonication... 

Desrosiers [23] considers ultrasonic bath extraction to be one of the best methods of in-polymer extraction. 

Applications Extraction is typically accomplished by refluxing the polymer in an appropriate solvent for l-48h [84,199]. In many cases, ultrasonic exposure reduces the extraction time [90,200], According to Table 3.5 there are several reports of US extraction from polymers. Ultrasonic extraction has been used for HDPE/(BHT, Irganox antioxidants, Isonox, Cyasorb, Am 340, MD 1024, Irgafos 168) [56], LDPE/Chimassorb 81 [201], SBR/tri(nonylphenyl) phosphite [200], HDPE/(Tinuvin 770, Chimassorb 944) [114], etc. Nielson [90] compared the recoveries obtained for a variety of analytes from PP, LDPE and HDPE with Soxhlet, ultrasonic bath and microwave oven. For all samples, the ultrasonic extraction could be achieved within 1 h. For LDPE and PP most compounds (except Irganox 1010) were extracted within 10 min. Further experiments by Nielson [56] on extraction from HDPE confirmed these results. Where phosphite antioxidants (such as Irgafos 168) are present the use of the solvent mixture DCM-cyclohexane was preferred as it prevented hydrolysis of the phosphite by extraction solvents such as alcohols [56]. Similarly, phosphite esters also undergo hydrolysis... 

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

Good degreasing when hot and in an ultrasonic bath Highly basic... 

Phenylmethyldichlorosilane (Petrarch) was distilled prior to use and dried over CaH2- Toluene was distilled from CaH2 and dried over CaH2- The known amounts of sodium were placed in a flask filled with toluene and purged with dry argon. This flask was placed in the ultrasonic bath (75-1970 Ultramet II Sonic Cleaner, Buehler Ltd.) until stable dispersion of sodium was formed. In some experiments an immersion-type ultrasonic... 

We have observed a dependence of the yield, polymerization degree, and polydispersity of polysilanes on temperature and also on the power of ultrasonication. In the ultrasonication bath the simplest test of the efficiency of cavitation is the stability of the formed dispersion. It must be remembered that the ultrasonic energy received in the reaction flask placed in the bath depends on the position of the flask in the bath (it is not the same in each bath), on the level of liquid in the bath, on temperature, on the amount of solvent, etc. When an immersion probe is used the cavitation depends on the level of the meniscus in the flask as well. The power is usually adjusted close to 50% of the output level but it varies with the reaction volume, flask shape, and other rection conditions. The immersion-type probe is especially convenient at lower temperatures. 

GPC traces of poly(phenylmethylsilylenes) prepared in the ultrasonication bath are shown in Fig. 1. In contrast to thermal condensation, monomodal high molecular weight polymer is formed. Oligomeric cycles (mostly cyclic pentamer), formed usually in high yield (cf. Table 1), can be very easily separated from the reaction mixture by precipitation with isopropanol. The molecular weight of polysilanes decreases and polydispersity increases with temperature. 

Preliminary dispersion of the stationary phase in a suitable solvent is best carried out in an ultrasonic bath. To prevent sedimentation of the stationary phase during packing, a number of different approaches have been used ... 

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