Hazards of Chemicals

Detonation Deflagration Thermal explosion Hypergolic reaction 

For substances found to participate in exothermic reactions, an experiment is necessary to establish the ease of initiation of such a reaction. For example, ease of detonation can be tested by mechanical stimulation, such as a blow or friction, or by detonation impulse such as a shock wave. Generally a mechanical stimulation gives a weak impact, and a 

Substances which explode by a weak impact (called highly sensitive substances) can be identified by a screening test like the drop ball test Whether deflagration occurs easily can be checked by an ignitability test Another screening test to examine the ease of occurrence of a reaction relies on the determination of the temperature at which decomposition is initiated by thermal analysis on micro-samples. This quantifies the ease of initiating a thermal explosion. 

Substances which react easily in the above tests should be regarded as materials which require considerable caution in handling. They should he used only if appropriate safety precautions may be taken. 

The magnitude of the reaction is an index of the potential of a hazard. The screening tests for the magnitude of a reaction include reaction heat calculation, reaction calorimetry and sealed cell differential scanning scanning calorimetry (SC—DSC). 

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Pb as the vessel burst pressure in bars. Other sources are Baker Explosion Hazards and Evaluation, Elsevier, 1983, p. 492) and Chemical Propulsion Information Agency Hazards of Chemical Rockets and Propellants Handbook, voT. 1 NTIS, Virginia, May 1972, pp. 2-56, 2-60). 

SOME HAZARDS OF CHEMICAL MANIPULATION IN PURIFICATION AND RECOVERY OF RESIDUES... 

This chapter provides a brief insight into selected fundamental principles of matter as a background to the appreciation of the hazards of chemicals. 

The hazards of chemicals are commonly detected in the workplace first, because exposure levels there are higher than in the general environment. In addition, the exposed population is well known, which allows early detection of the association between deleterious health effects and the exposure. The toxic effects of some chemicals, such as mercury compounds and soot, have been known already for centuries. Already at the end of the eighteenth century, small boys who were employed to climb up the inside of chimneys to clean them suffered from a cancer of the scrotum due to exposure to soot. This was the first occupational cancer ever identified. In the viscose industry, exposure to carbon disulfide was already known to cause psychoses among exposed workers during the nineteenth century. As late as the 1970s, vinyl chloride was found to induce angiosarcoma of the liver, a tumor that was practically unknown in ocher instances. ... 

For perspective, 1 g of hydrazine monohydrate is equivalent to (TNT) in terms of thermal potential T. Grewer, Thermal Hazards of Chemical Reactions Elsevier Amsterdam, 1994, Vol. 4. 

Dr K. Ziegler-Skylakakis, Secretariat of the Commission for the Investigation of Health Hazards of Chemical Compounds in the Workplace Area (MAK Commission), Freising-Weihenstephan, Germany... 

Baughman GL, Lassiter RR. 1978. Prediction of environmental pollutant concentration. In Carins J Jr, Dickson KL, Maxi AW, eds. Estimating the hazard of chemical substances to aquatic life. American Society for Testing and Materials, Philadelphia, PA. ASTM STP657, 35-54. 

Reducing the intrinsic hazard of chemicals is the most effective and most fundamental of the risk reduction options available. Intrinsic risk reduction is based on the principle that the structure of a chemical drives hazard and molecular intentional, informed manipulation will result in the design of safer chemicals. Wastewater treatment plants employ large filters packed with granular activated carbon to remove polluted water. Synthetic chemists are... 

Progressing toward the goal of designing safer chemicals requires that the relative safety of chemicals can be compared so that a clear decision process can be identified. The metrics to accomplish this evaluation of the relative hazards of chemicals are well estabhshed but have not been applied to the field of green chemistry, specifically, designing safer chemicals. 

Figure 5.4-57. Programmable DTA plot.s for variou.s heating rates 4-nitrobenzoic acid (reprinted from Grewer (1994), Thermal hazards of chemical reactions , Copyright (1994) with permission from Elsevier Science). 

Grewer, Th., 1994, Thermal Hazards of Chemical Reactions , Elsevier, Amsterdam. 

Despite ail of this, LEL is not regarded as an important inflammability parameter. In fact, as will be seen in paragraph 1.3, flashpoints are considered to be more convenient in the evaluation of fire hazard of chemical substances. 

In this section the special hazards of chemicals are reviewed (toxicity, flammability and corrosivity) together with the other hazards of chemical plant operation. 

The HCS was promulgated to provide workers with access to information about the hazards and identities of the chemicals they are exposed to while working, as well as the measures they can take to protect themselves. OSHA s HCS requires employers to establish hazard communication programs to transmit information on the hazards of chemicals to their employees by means of labels on containers, material safety data sheets, and training programs. 

Baughman, G.L. Lassiter, R. R. "Estimating the Hazard of Chemical Substances to Aquatic Life." Cairns, J., Dickson, K.L. and Maki, A.w., eds. American Society for Testing and Materials, Philadelphia, 1978. 

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. 

The results of a public opinion survey on the hazards of chemicals are shown in Figure 1-5. This survey asked the participants if they would say chemicals do more good than harm, more harm than good, or about the same amount of each. The results show an almost even three-way split, with a small margin to those who considered the good and harm to be equal. 

CPIA Publication 394, Hazards of Chemical Rockest and Propellants, Volume I. Safety, Health, and the Environment September 1984, Healy, J., Weissman, S., Werner, H., and Dobbs, N. 

Thermal Hazards of Chemical Reactions (Grewer 1994). Addresses the characterization of thermal hazards involved in reactions of liquid and solid substances and mixtures, particularly those having low to medium reaction energies. The publication aims to present methods for distinguishing hazardous from nonhazardous reactions. 

Hazard identification-structured approach to identifying and understanding the reactive hazards of chemicals used alone or in combination. 

The hazards of chemicals, as noted previously, are well-documented, and even the dominant formulator companies in the industry have been forced to acknowledge to their shareholders that there are inevitable risks inherent in the... 

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