Hydrides toxicity

Dry dichloromethane (0.5 ml distilled from calcium hydride) toxic, irritant... 

Beryllium Hydride. BeryUium hydride [13597-97-2] is an amorphous, colorless, highly toxic polymeric soHd (H = 18.3%) that is stable to water but hydroly2ed by acid (8). It is insoluble in organic solvents but reacts with tertiary amines at 160°C to form stable adducts, eg, (R3N-BeH2 )2 (9). It is prepared by continuous thermal decomposition of a di-/-butylberylhum-ethyl ether complex in a boiling hydrocarbon (10). 

Hydrogen-storage alloys (18,19) are commercially available from several companies in the United States, Japan, and Europe. A commercial use has been developed in rechargeable nickel—metal hydride batteries which are superior to nickel—cadmium batteries by virtue of improved capacity and elimination of the toxic metal cadmium (see BATTERIES, SECONDARYCELLS-ALKALINe). Other uses are expected to develop in nonpolluting internal combustion engines and fuel cells (qv), heat pumps and refrigerators, and electric utility peak-load shaving. 

Generalizations on the toxicity of hydrides as a class of compounds are difficult to make because of variations in their chemical reactivity. Furthermore, there is Htde pubHshed toxicological information available. 

Although there is Httle toxicity information pubHshed on hydrides, a threshold limit value (TLV) for lithium hydride in air of 25 fig/has been established (52). More extensive data are available (53) for sodium borohydride in the powder and solution forms. The acute oral LD q of NaBH is 50-100 mg/kg for NaBH and 50-1000 mg/kg for the solution. The acute dermal LD q (on dry skin) is 4-8 g/kg for NaBH and 100-500 mg/kg for the solution. The reaction or decomposition by-product sodium metaborate is slightly toxic orally (LD q is 2000-4000 mg/kg) and nontoxic dermally. 

Copper sulfate, in small amounts, activates the zinc dust by forming zinc—copper couples. Arsenic(III) and antimony(TTT) oxides are used to remove cobalt and nickel they activate the zinc and form intermetaUic compounds such as CoAs (49). Antimony is less toxic than arsenic and its hydride, stibine, is less stable than arsine and does not form as readily. Hydrogen, formed in the purification tanks, may give these hydrides and venting and surveillance is mandatory. The reverse antimony procedure gives a good separation of cadmium and cobalt. 

Arsenic is both toxic and cai cinogenic element. It is necessary to have a fast, reliable and accurate method for determination of ai senic in water. The hydride-generation atomic fluorescence spectrometry (HG AFS) is one of the simple and sensitive techniques for the determination of this element in various types of waters. 

The metal itself, having an appreciable vapour pressure, is also toxic, and produces headaches, tremors, inflammation of the bladder and loss of memory. The best documented case is that of Alfred Stock (p. 151) whose constant use of mercury in the vacuum lines employed in his studies of boron and silicon hydrides, caused him to suffer for many years. The cause was eventually recognized and it is largely due to Stock s publication in 1926 of details of his experiences that the need for care and adequate ventilation is now fully appreciated. 

Although modern chemistry allows development of even more effective rocket propellants, energy efficiency is not the only consideration factor. For example, fluorine and its derivatives arc better oxidizers than oxygen, but their extreme toxicity make them environmentally dangerous. The same concerns prevent the use of beryllium hydride—an excellent fuel that combines high density with the energy efficiency comparable to liquid hydrogen. 

Its solubility characteristics in aqueous systems are such that retention of toxicity to insects by dissolved crystal protein is always suspect, and loss of activity on dissolution owing to denaturation is often observed. The protein is soluble only in relatively strong aqueous alkali. Thus, it has been variously reported to be soluble in 0.01N- to 0.05N sodium hydroxide (1) and alkali at pH 10.5 in the presence of thioglycollate (35) we have also observed its solubility in alkali at pH 9.5 in the presence of urea and potassium boro hydride. One difference between the characteristic proteins produced by various strains of crystalliferous bacilli is observed in the degree of alka-... 

To be useful as CVD precursors, a metallo-organic compound should be stable at room temperature so that its storage and transfer are not a problem. It should also decompose readily at low temperature, i.e., below 500°C. The compounds listed in Table 4.1 meet these conditions with the exception of the alkyls of arsenic and phosphorus, which decompose at higher temperatures. For that reason, the hydrides of arsenic and phosphorus are often preferred as CVD precursors (see Ch. 3). These hydrides however are extremely toxic and environmental considerations may restrict their use. 

Battery technology continues to advance at a steady pace. Lithium batteries and nickel-metal-hydride batteries are now commonplace. These new rechargeable batteries eliminate the need for toxic cadmium and store more energy per unit mass. The detailed chemistry that underlies the newest advances in battery technology involves principles that are beyond the scope of an introductory course. 

Owing to the expense, toxicity, and purification problems associated with use of stoichiometric amounts of tin hydrides, there has been interest in finding other hydrogen atom donors.205 The trialkylboron-oxygen system for radical generation (see Part A, Section 11.1.4) has been used with fra-(trimethylsilyl)silane or diphenylsilane as a hydrogen donor.206... 

Reacts with many metals to give hydrogen, sometimes violently. With non-metals pyrophoric hydrides may result. Frequently initiates explosive reactions between other substances. Violent reactions with many non-metal and some metal halides and oxyhalides, also with many organometallic compounds. Many metal nonmetal-lides produce toxic, flammable or pyrophoric gases on contact with diprotium monoxide. 

The hydride (and the metal) when finely divided are spontaneously flammable, and binning causes a specially dangerous contamination problem, in view of the radioctive and toxic hazards. 

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