Cleaning baths commercial

In the preceding chapters many aspects of sonochemistry and its application have already been discussed in details and now to conclude, few experiments are being discussed here to make the beginners in the field of sonochemistry, especially the undergraduate students, to ride on the sound wave and begin their journey of sonochemistry with some of these experiments, which can be conveniently carried out with an ultrasonic cleaning bath (Fig. 15.1) or an ultrasonic probe (Fig. 15.2) of 20 kHz, available commercially abundantly. 

Some of the problems associated with using a commercial cleaning bath can be overcome using an ultrasonic bath purpose built for sonochemistiy. Typically these baths are designed with a large area transducer in the base and external cooling/thermostat-ting (Fig. 7.9). 

Of the four types of laboratory ultrasonic apparatus commercially available for practising chemists in general (namely, whistle reactors, ultrasonic cleaning baths, probes and cup-horn devices) analytical chemists, except for a few specialists working in (or with) ultrasound detectors, use mainly cleaning baths and probes both of which are usually operated at a fixed frequency dependent on the particular type of transducer, that is usually 20 kHz for common probe systems and 40 kHz for baths. Both types of devices are described below. 

In the process of sonication, electrical energy is converted into mechanical energy. The sound waves produce cavitation (the process of formation and collapse of microscopic bubbles) which leads to great mechanical shear forces. Particles are hammered to form smaller particles, and the increased energy of the system can promote chemical reactions. Ultrasonic chemistry has recently been reviewed [34]. Most research in sonichemistry has been carried out in ultrasonic cleaning baths. Operations on scale can be carried out by using commercial flow cells [35],... 

Commercially available high-intensity ultrasonic probes (10 to 500Wcm ) are the most effective sources for laboratory scale sonochemistry. A typical system operates at 24 kHz with an adjustable total power output of up to 200W and also adjustable irradiation times per pulse of a few tenths of a second. Lower intensities can often be used in liquid-solid heterogeneous systems of interest here because of the reduced liquid tensile strength at the liquid-solid interface, and a common ultrasonic cleaning bath (about lWcm ) can often be adequate for SAE. 

Sodium nitrate is also used in formulations of heat-transfer salts for he at-treatment baths for alloys and metals, mbber vulcanization, and petrochemical industries. A mixture of sodium nitrate and potassium nitrate is used to capture solar energy (qv) to transform it into electrical energy. The potential of sodium nitrate in the field of solar salts depends on the commercial development of this process. Other uses of sodium nitrate include water (qv) treatment, ice melting, adhesives (qv), cleaning compounds, pyrotechnics, curing bacons and meats (see Food additives), organics nitration, certain types of pharmaceutical production, refining of some alloys, recovery of lead, and production of uranium. 

Electroless reactions must be autocatalytic. Some metals are autocatalytic, such as iron, in electroless nickel. The initial deposition site on other surfaces serves as a catalyst, usually palladium on noncatalytic metals or a palladium—tin mixture on dielectrics, which is a good hydrogenation catalyst (20,21). The catalyst is quickly covered by a monolayer of electroless metal film which as a fresh, continuously renewed clean metal surface continues to function as a dehydrogenation catalyst. Silver is a borderline material, being so weakly catalytic that only very thin films form unless the surface is repeatedly cataly2ed newly developed baths are truly autocatalytic (22). In contrast, electroless copper is relatively easy to maintain in an active state commercial film thicknesses vary from <0.25 to 35 p.m or more. 

A commercially available ultrasonic cleaner was used for the prqjaration of nickel powders from nickel salt in aqueous solution. This cleaner, Model 3210 (Branson Ultrasonic Corp., CT), is normally used as a cleaning apparatus, working at a frequency of 47 kHz with e power of 130 W that consists of a stainless-steel bath of 5.17 1 capacity and has an ultrasonic transducer attached to the bottom of the bath. A liquid solution temperature in the bath can be varied from room temperature to maximum of 80 °C. 

An air bath is a very cheap and convenient method of effecting even heating of small distillation flasks (say, 25 ml or 50 ml), where the use of a micro Bunsen burner, results in fluctuations in the level of heating due to air draughts. It may be readily constructed from two commercial tin cans (not aluminium) (those from tinned fruit or food are quite suitable), of such sizes that one fits into the other to provide a small concentric gap as an air insulator. The cleaned large can is cut to the same height as the small can, and the base is then removed. The... 

---