Inorganic lead compounds, solubility

Lead compounds are preferentially concentrated in a cumulative way, in soft tissues after absorption, mainly in the liver and kidneys. Certain soluble inorganic lead compounds (i.e., lead acetate and lead phosphate) are A3 confirmed carcinogens to animals, and unknown effects on humans [38]. 

Work with low solubility inorganic lead compounds when tested for low solubility... 

Table 4 presents solubilities and other physical properties of inorganic lead compounds. Inorganic lead (II) salts of lead sulfide, and lead oxides are poorly soluble in water. Notable exceptions are lead nitrate, lead acetate, lead chlorate, and, to a lesser degree, lead chloride. Inorganic lead (II) salts have relatively high melting points, with corresponding low vapor pressures at room temperature. 

L. W. Newland and K. A. Daum Table 4. Solubility of some inorganic lead compounds ... 

In water, tetraalkyl lead compounds are subject to photolysis and volatilization with the more volatile compounds being lost by evaporation. Degradation proceeds from trialkyl lead to dialkyl lead to inorganic lead. Tetraethyl lead is susceptible to photolytic decomposition in water. Triethyl and trimethyl lead are more water-soluble and therefore more persistent in the aquatic environment than tetraethyl or tetramethyl lead. The degradation of trialkyl lead compounds yields small amounts of dialkyl lead compounds. Removal of tetraalkyl lead compounds from seawater occurs at rates that provide half-lives measurable in days (DeJonghe and Adams 1986). 

Conventional materials like different metal oxides are used in the curing systems of the rubber compounds. When used, these are freely present in the compound, soluble in the inorganic acids that are used in the oil exploration industry and lead to high swelling effects on rubber. 

Nervous System. The nervous system is also a common target of toxic metals particularly, organic metal compounds (see Chapter 16). For example, methylmercury, because it is lipid soluble, readily crosses the blood-brain barrier and enters the nervous system. By contrast, inorganic mercury compounds, which are more water soluble, are less likely to enter the nervous system and are primarily nephrotoxicants. Likewise organic lead compounds are mainly neurotoxicants, whereas the first site of inorganic lead is enzyme inhibition (e.g., enzymes involved in heme synthesis). 

Organic tetraethyl lead was a component of gasoline (Goldings and Stewart 1982). It is converted in the liver to triethyl lead, a water-soluble metabolite that can accumulate in the brain (Robinson 1978). This compound can be further broken down to inorganic lead. 

Lead compounds such as lead naphthalene tetracarboxylate, lead pyrophosphate, lead stannate, lead sulfide, and others which are not listed in Table 3, were proved to be effective uranium sorbents in sea water 131). However, sorbent materials containing toxic metals must be excluded with respect to sea contamination which would be inevitable even in the case of slight solubility. On the other hand, many metal compounds are decomposed in sea water by hydrolysis and carbonate formation. Among the inorganic sorbents presented in Table 3, hydrous titanium oxide and... 

Tetraethyl lead and tetramethyl lead are lipid-soluble compounds that are absorbed readily from the skin, GI tract, and lungs. The toxicity of tetraethyl lead is believed to be due to its metabolic conversion to triethyl lead and inorganic lead. The major symptoms of intoxication with tetraethyl lead are referable to the CNS insomnia, nightmares, anorexia, nausea and vomiting, diarrhea, headache, muscular weakness, and emotional instability. Subjective CNS symptoms such as... 

Lead added to soil may react with available soil anions such as S04 " P04 or COa " to form sparingly soluble salts [8]. Compounds such as basic lead carbonate, Pb3(0H)2(C03)2 (log — —46.8 at 25° C) and chloropyro-morphite, Pbs(P04)3Cl, (log = —84.4) provide the least soluble simple inorganic. lts at near-neutral pH. In fact, X-ray powder diffraction (XRD) studies by Olsen and Skogerboe [18] have shown the more soluble PbS04 to be the major crystalline lead compound in contaminated soils. The results of these workers are shown in Table 4.5. 

The solubility of most inorganic compounds is reduced by the addition of organic solvents, such as methanol, ethanol, propan-l-ol, acetone, etc. For example, the addition of about 20 per cent by volume of ethanol renders the solubility of lead sulphate practically negligible, thus permitting quantitative separation. Similarly calcium sulphate separates quantitatively from 50percent ethanol. Other examples of the influence of solvents will be found in Chapter 11. 

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