Ultrasonic baths, hazards

Ultrasonic baths can be used to remove detritus from delicate moulds. This method eliminates the possibility of damage by blasting techniques and does not present the health hazard of chemical methods. 

There are at least four different kinds of equipment used in biomedical laboratories that can produce hazardous amounts of electromagnetic radiation. These are ultraviolet lamps, lasers, microwave ovens, and x- and gamma ray-producing equipment. Although ultrasonic baths do not produce electromagnetic radiation, the injury caused by this equipment is similar to that caused by microwaves thus we will discuss its use in this section. The hazards that these pieces of equipment pose and the preventive measures workers must observe are discussed in the following pages. 

A very reactive form of a finely divided metal is a so-called Rieke powder [79]. These materials are produced as fine powders by chemical precipitation during the reduction of various metal halides ivith potassium metal in refluxing tetrahydrofuran. Obviously this is a potentially hazardous laboratory procedure and ultrasound has provided an alternative method of preparation of these extremely valuable reagents [80]. The sonochemical technique involves the reduction of metal halides with lithium in TH F at room temperature in a cleaning bath and gives rise to metal powders that have reactivities comparable to those of Rieke powders. Thus powders of Zn, Mg, Cr, Cu, Ni, Pd, Co and Pb were obtained in less than 40 min by this ultrasonic method compared with reaction times of 8 h using the experimentally more difScult Rieke method (Tab. 3.1). 

---