Alkali poisoning

The common impurities found in amines are nitro compounds (if prepared by reduction), the corresponding halides (if prepared from them) and the corresponding carbamate salts. Amines are dissolved in aqueous acid, the pH of the solution being at least three units below the pKg value of the base to ensure almost complete formation of the cation. They are extracted with diethyl ether to remove neutral impurities and to decompose the carbamate salts. The solution is then made strongly alkaline and the amines that separate are extracted into a suitable solvent (ether or toluene) or steam distilled. The latter process removes coloured impurities. Note that chloroform cannot be used as a solvent for primary amines because, in the presence of alkali, poisonous carbylamines (isocyanides) are formed. However, chloroform is a useful solvent for the extraction of heterocyclic bases. In this case it has the added advantage that while the extract is being freed from the chloroform most of the moisture is removed with the solvent. 

The emetics are used mainly in poisoning when gastric lavage facilities are not available. But in certain poisoning e.g. kerosene poisoning, corrosive acid or alkali poisoning, emetics are contraindicated. They are also not advisable in unconscious patients as they may aspirate vomitus. 

As expected for silica-alumina as a mixed oxide (see also Section IV.B.5), the PyH+ and PyL species are observed simultaneously (160, 205,206,221-223). Two distinct types of Lewis acid sites could be detected (19b mode at 1456 and 1462 cm-1, respectively) on a specially prepared aluminum-on-silica catalyst (160). On water addition, the Lewis sites can be converted into Br nsted sites (160, 205, 221), The effect of Na+ ions on the acidity of silica-aluminas has been studied by Parry (205) and by Bourne et al. (160). It can be concluded from Parry s results that Na+ ions affect both types of acid sites, so that alkali poisoning does not seem to eliminate the Br nsted sites selectively. For quantitative determination of the surface density of Lewis and Br nsted acid sites by pyridine chemisorption, one requires the knowledge of at least the ratio of the extinction coefficients for characteristic infrared absorption bands of the PyH+ and PyL species. Attempts have been made to evaluate this ratio for the 19b mode, which occurs near 1450 cm-1 for the PyL species and near 1545 cm-1 for the PyH+ species (160,198,206,221,224,225). The most reliable value as calculated from the data given by Hughes and White (198) seems to be... 

Poisoning by water vapor is a reversible effect and can be overcome by redrying the catalyst. Alkali poisoning, on the other hand, is permanent and may involve the formation of a salt, such as a manganite or cobaltite in the surface layer. In such cases, the manganese or cobalt atom is more completely coordinated and the reactivity of the surface considerably lessened thereby. Carbon monoxide is therefore oxidized only stoichiometrically by poisoned Mn02. 

Rostrup-Nielsen JR, Christiansen LJ (1995) Internal steam reforming in fuel-cells and alkali poisoning. Appl Catal A 126 381... 

Buzanowski and Yang [76] studied the kinetics over both unpoisoned V2O5 on Ti02 and alkali poison-doped catalysts. The results for two unpoisoned vanadia on titania catalysts are given in Fig. 5.21. It was observed that the higher the vanadia load the higher the conversion. 

Liang used n.m.r. to characterize amines adsorbed on hydrated silica-alumina they found evidence for protonated species on sites which were not sterically hindered. Further work on the thermal desorption of pyridine and n-butylamine from silica-aluminas (13 and 25 wt % AI2O3) showed that the stronger acid sites, where pyridine was adsorbed, were of varied acid strength, and both number and strength of the sites were affected by alkali poisoning. An i.r. study of pyridine adsorbed on sodium-poisoned silica-alumina also showed both Lewis and Bronsted sites to be affected. 

For alkali poisoning (a) neutralize and dilute the alkali with a weak acid such eis dilute lemon juice or vinegar, then give milk or (b) give an all-purptose antidote. 

Fig. 4.39 The effect of alkali poisoning of MoO.—TiOj on the catalytic aaivity in the reduction of NO with NHj MoO, content 10 atomic %, reaction temperature, 523 K, 548 K, 0 573 K.

Fig. 4.40 The eiTect of alkali poisoning of MoO Ti02 on the catalytic activity in the isomerization of cyclopropane Ol 3rd pulse, 10th pulse.

C2oH4qO- a diterpenic alcohol obtained by the action of alkalis on chlorophyll. Colourless oil b.p. 202-204 C/lOmm. On oxidation it yields a ketone CigHsoO b.p. 175 "C/l I mm. phytoxic Poisonous to plants. 

Other sources of hazard arise from the handling of such chemicals as concentrated acids, alkalis, metallic sodium and bromine, and in working with such extremely poisonous substances as sodium and potassium cyanides. The special precautions to be observed will be indicated, where necessary, in the experiments in which the substances are employed, and will also be supplied by the demonstrator. The exercise of obvious precautions and cautious handling will in most cases reduce the danger to almost negligible proportions. Thus, if concentrated sulphuric acid should be accidentally spilled, it should be immediately washed with a liberal quantity of water or of a solution of a mild alkali. 

Sodium cyanide is very poisonous and must be handled with great care. The hands should be washed immediately after using it. All the residual solution.s containing alkali cyanides must be emptied into the main drain of the laboratory and washed down with a liberal supply of water they should never be treated with acid. 

Alkali AletalIodides. Potassium iodide [7681-11-0] KI, mol wt 166.02, mp 686°C, 76.45% I, forms colorless cubic crystals, which are soluble in water, ethanol, methanol, and acetone. KI is used in animal feeds, catalysts, photographic chemicals, for sanitation, and for radiation treatment of radiation poisoning resulting from nuclear accidents. Potassium iodide is prepared by reaction of potassium hydroxide and iodine, from HI and KHCO, or by electrolytic processes (107,108). The product is purified by crystallization from water (see also Feeds and feed additives Photography). 

Strychnicine. This alkaloid, isolated from nux-vomica leaves grown in. lava, forms needles, m.p. 240° dec.), and is characterised by the following colour reaction. When sodium hydroxide solution is added drop by drop to a solution of a salt of the alkaloid in water, the precipitate formed dissolves on addition of more alkali, forming an orange-coloured liquid which develops a violet colour on addition of hydrochloric acid. Strychnicine is scarcely poisonous, but is said to produce tetanus in frogs. 

If the bleach is mixed with an acid, it can release poisonous chlorine gas. To prevent this from happening, commercial bleaches leave extra alkalies in the solution to keep the pH very high (pH 12). This small amount of extra lye in the solution, along with the caustic nature of the hypochlorite itself, is what eats away the cloth if undiluted bleach gets spilled on the clothing. 

The catalytic system used in the Pacol process is either platinum or platinum/ rhenium-doped aluminum oxide which is partially poisoned with tin or sulfur and alkalinized with an alkali base. The latter modification of the catalyst system hinders the formation of large quantities of diolefins and aromatics. The activities of the UOP in the area of catalyst development led to the documentation of 29 patents between 1970 and 1987 (Table 6). Contact DeH-5, used between 1970 and 1982, already produced good results. The reaction product consisted of about 90% /z-monoolefins. On account of the not inconsiderable content of byproducts (4% diolefins and 3% aromatics) and the relatively short lifetime, the economics of the contact had to be improved. Each diolefin molecule binds in the alkylation two benzene molecules to form di-phenylalkanes or rearranges with the benzene to indane and tetralin derivatives the aromatics, formed during the dehydrogenation, also rearrange to form undesirable byproducts. 

Thus the promoting and poisoning role of Li, or any other alkali, can be predicted in a qualitative way from the simple rules of section 2.5 or, equivalently, from equations (2.28) and (2.29). 

Pt-Re-alumina catalysts were prepared, using alumina containing potassium to eliminate the support acidity, in order to carry out alkane dehydrocyclization studies that paralleled earlier work with nonacidic Pt-alumina catalysts. The potassium containing Pt-Re catalyst was much less active than a similar Pt catalyst. It was speculated that the alkali metal formed salts of rhenic acid to produce a catalyst that was more difficult to reduce. However, the present ESCA results indicate that the poisoning effect of alkali in Pt-Re catalysts is not primarily due to an alteration in the rhenium reduction characteristics. 

Octamethyl pyrophosphoramide is a colorless oil, completely soluble in water, benzene, acetone, and many other common organic solvents except the paraffinic hydrocarbons. Its hydrolysis rate has not been measured, but it appears stable in the absence of alkali. In England, this systemic insecticide has been used to control aphids on hops. There it has been calculated that only a negligible quantity of the poison ultimately may find its way into the beer made from the hops. Despite calculations of this sort, the use of octamethyl pyrophosphoramide on food or fodder crops in this country is definitely not to be recommended. However, it may prove useful if properly applied to control certain insects, especially those attacking ornamental plants, such as rosebushes, and possibly on the cotton aphid and grape phylloxera. The compound has only recently been made available experimentally. 

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