Dangers in the Laboratory

There is a wide variety of potential dangers in the laboratory (Table 3.3) so try to keep alive to them all. 

In conclusion, there are a number of techniques that will give reliable results for lead analysis. The spectrophotometric method, while probably the most popular, suffers from lack of specificity, and great care must be taken to ensure that a positive test is due to lead. In addition, the technique is quite tedious, requiring several extractions and pH adjustments, and the use of cyanide solutions always poses a danger in the laboratory. The use of sulfuric acid for digestion in the procedure recommended by Rice et al. for blood and urine should be used with caution. 

Sand. Buckets of dry sand for fire-extinguishing should be available in the laboratory and should be strictly reserved for this purpose, and not encumbered with sand-baths, waste-paper, etc. Most fires on the bench may be quickly smothered by the ample use of sand. Sand once used for this purpose should always be thrown away afterwards, and not returned to the buckets, as it may contain appreciable quantities of inflammable, non-volatile materials e.g., nitrobenzene), and be dangerous if used a second time. 

The most dangerous solvent in the laboratory is carbon disulphide, the flash-point of which is so low that its vapour is ignited, e.g., by a gas-ring 3 4 minutes after the gas has been turned out. CarlK>n disulphide should therefore never be used in the laboratory unless an adequate substitute as a solvent cannot be found. Probably the next most dangerous liquid for general manipulation is ether, which, however, has frequently to be employed. If the precautions described on pp. 79, 163, are always followed, the manipulation of ether should however quite safe. 

The inflammable solvents most frequently used for reaction media, extraction or recrystallisation are diethyl ether, petroleum ether (b.p. 40-60° and higher ranges), carbon disulphide, acetone, methyl and ethyl alcohols, di-Mo-propyl ether, benzene, and toluene. Special precautions must be taken in handling these (and other equivalent) solvents if the danger of Are is to be more or less completely eliminated. It is advisable to have, if possible, a special bench in the laboratory devoted entirely to the recovery or distillation of these solvents no flames are permitted on this bench. 

In the past ten years laboratory workers have become increasingly conscious of safety in the laboratory environment. We have therefore in three places in Chapter 1 (pp. 3 and 33, and bibliography p. 52) stressed more strongly the importance of safety in the laboratory. Also, where possible, in Chapters 3 and 4 we draw attention to the dangers involved with the manipulation of some hazardous substances. 

Ethers are relatively stable and unreactivc in many respects, but some ethers react slowly with the oxygen in air to give peroxides, compounds that contain an 0-0 bond. The peroxides from low-molecular-weight ethers such as diisopropyl ether and tetrahydrofuran arc explosive and extremely dangerous, even in tiny amounts. Ethers are very useful as solvents in the laboratory, but they must always be used cautiously and should not be stored for long periods of time. 

Safety procedures must be observed in the laboratory at all times. Many chemicals encountered in analysis are poisonous and must be carefully handled. Whereas the dangerous properties of concentrated acids and of widely recognised poisons such as potassium cyanide are well known, the dangers associated with organo-chlorine solvents, benzene and many other chemicals are less apparent. 

Professor Martel s book addresses specifically some of the more technical eispects of the risk assessment process, mainly in the areas of hazard identification, and of the consequence/effect analysis elements, of the overall analysis whilst where appropriate setting these aspects in the wider context. The book brings together a substantial corpus of information, drawn from a number of sources, about the toxic, flammable and explosive properties and effect (ie harm) characteristics of a wide range of chemical substances likely to be found in industry eind in the laboratory, and also addresses a spectrum of dangerous reactions of, or between, such substances which may be encountered. This approach follows the classical methodology and procedures of hazard identification, analysing material properties eind... 

For technical purposes (as well as in the laboratory) RuOz and Ru based thin film electrodes are prepared by thermal decomposition techniques. Chlorides or other salts of the respective metals are dissolved in an aqueous or alcoholic solution, painted onto a valve metal substrate, dried and fired in the presence of air or oxygen. In order to achieve reasonable thicknesses the procedure has to be applied repetitively with a final firing for usually 1 hour at temperatures of around 450°C. A survey of the various processes can be found in Trasatti s book [44], For such thermal decomposition processes it is dangerous to assume that the bulk composition of the final sample is the same as the composition of the starting products. This is especially true for the surface composition. The knowledge of these parameters, however, is of vital importance for a better understanding of the electrochemical performance including stability of the electrode material. 

Whoever sets about preparative work carelessly and thoughtlessly may easily come to harm. Bui even the careful are not secure against all danger. The serious accidents which, alas, again and again occur in chemical laboratories make it imperative that every worker in the laboratory should fully and seriously consider his duty towards his fellows. 

For valence band studies, for instance, energy dependent UPS in the 30-300 eV excitation range is certainly of interest, and would be available in synchrotron radiation sources. This experiment, however, is difficult to realize, since it would involve the construction of safely enclosed systems, in which to handle dangerous a, p (and sometimes y or neutron) emitters in considerable quantities. This systems must be well separated from the main beam lines. And all of this must be done in the laboratories of a storage ring, which are usually not adapted for radioactive hazards. 

The permissible exposure limit, PEL in table A3, is given in ppm in the air for an ordinary work shift in the laboratory in industry (Kirk-Othmer, 1978). This quantity is also called the threshold limit (Riddick et al., 1986). Concentrations that are of immediate danger to life or health, called IDLH in table A3, in ppm in the air, may be much higher than the PEL and be tolerated for short periods of time, say 30 min. 

In the same connection it. is pointed out the inherent danger in the use of fuming nitric acid for laboratory nitrations. Aniline and such acid are used in some JATO units The action of alkalies on nitroparaffins may result in formation of intermediates, leading eventually to salts of fulminic acid There is also danger in handling of strong hydrogen peroxide, of its salts, and... 

Be familiar with the properties of all chemicals used in the laboratory. This includes their flammability, reactivity, toxicity, and proper disposal. This information may be obtained from your instructor or from an MSDS. Always wear disposable gloves when using potentially dangerous chemicals or infectious agents. 

Osmium tetroxide, like the skunk, carries its own warning system-a strong odor described variously as resembling chlorine, bromine, or ozone. Clearly, a commonsense approach to the use of this reagent in an efficient hood is called for, and under these conditions osmium tetroxide should be regarded as no more dangerous than many other reagents found in daily use in the laboratory. 

Concern with the hazards associated with the use of flammable and toxic chemicals in the laboratory often causes the dangers from electrical equipment to be overlooked. However, many accidents are caused by the malfunctioning of electric appliances and by thoughtless handling. 

AH0 is — 28 kJ mol-1 and AG°is —130 kJ mol-1. This should illustrate the dangers of purely thermodynamic arguments in assessing stability. (It also demonstrates the dangers which accompany the handling of perchlorates in the laboratory.)... 

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