Laboratory reagents preparation

Laboratory reagents, preparation of, 8-1 to 4 Laboratory Solvents and Other Liquid Reagents, 15-13 to 22 Laguerre polynomials, A-83 to 85 Lanthanum see also Elements electrical resistivity, 12-39 to 40 electron configuration, 1-18 to 19 heat capacity, 4-135 history, occurrence, uses, 4-1 to 42 ionization energy, 10-203 to 205 isotopes and their properties, 11-56 to 253 magnetic susceptibility, 4-142 to 147 molten, density, 4-139 to 141 physical properties, 4-133 to 134 thermal properties, 12-201 to 202 vapor pressure, 6-61 to 90 vapor pressure, high temperature, 4-136 to 137... 

L.28 Silver nitrate is an expensive laboratory reagent that is often used for quantitative analysis of chloride ion. A student preparing to conduct a particular analysis needs 100.0 ml. of 0.0750 M AgNO,(aq), but finds only about 60 mL of 0.0500 M AgNO,(aq). Instead of making up a fresh solution of the exact concentration desired (0.0750 M), the student decides to pipet... 

A note on good practice Whether or not a reaction is spontaneous depends on the composition, so it is better to say that K > 1 for a reaction rather than that it is spontaneous. However, for reactions with very large equilibrium constants, it is very unlikely that the mixture of reagents prepared in the laboratory will correspond to 2 > K, and it is common to refer to such reactions as spontaneous. ... 

It is often necessary to carry out some reagent preparation. This may seem a trivial aspect of laboratory work, but its importance is often underestimated. It is a common source of error and it is worth taking a little bit of time to ensure reagents and, in particular, standards are correctly made-up. Very simple principles are involved. Follow any instructions available, implement safety instructions, use equipment properly and check that you know what you are doing before you start. 

Uses Antiseptic and disinfectant pharmaceuticals dyes indicators slimicide phenolic resins epoxy resins (bisphenol-A) nylon-6 (caprolactum) 2,4-D solvent for refining lubricating oils preparation of adipic acid, salicylic acid, phenolphthalein, pentachlorophenol, acetophenetidin, picric acid, anisole, phenoxyacetic acid, phenyl benzoate, 2-phenolsulfonic acid, 4-phenolsulfonic acid, 2-nitrophenol, 4-nitrophenol, 2,4,6-tribromophenol, 4-bromophenol, 4-/ert-butylphenol, salicylaldehyde, and many other organic compounds germicidal paints laboratory reagent. 

In our laboratory crude preparations of aphantoxins and anatoxin-a(s) are extracted similarly except at the final stages of purification (Fig. 2). A Bio-gel P-2 column (2.2 x 80 cm) is used for aphantoxins gel filtration and a Sephadex G-15 (2.6 x 42 cm) column for ana-toxin-(s). Both toxins are eluted with 0.1 M acetic acid at 1.5 ml/ min. Fractions of aphantoxins from Bio-gel P-2 run are spotted on thin-layer chromatography plates (Silica gel-60, EM reagents) and developed according to Buckley et al. (1976) (31). The Rf values for the aphantoxins, saxitoxin and neosaxitoxin standards (Table 1) indicates that two of the aphantoxins (i.e. I and II) are similar to saxitoxin and neosaxitoxin. 

Synthesis of well defined functionalized (- telechellc or multifunctional-) macromolecules Is an Important task for polymer chemists. The polymers with P0(0R)2, - Si(0R)3, -OH, - . .. functional groupslrS. are produced In limited quantities. The need for polymeric materials possessing specific properties has led to a renewed Interest Is functional polymers, especially if the initial material Is a common hydrocarbon polymer. One of the techniques that we use in our laboratory to prepare these new molecules Is based on anionic processes. This anionic technique is best suited to control the length of the chains prepared and to obtain samples with low polydlsperslty. Although the functionalization of carbanionic sites with various deactivating reagents Is easier than with other methods because of the long lived species, It Is still necessary to carefully control the deactivation reaction to prevent secondary reactions. 

Phenol has a wide range of uses, including in the preparation of phenolic and epoxy resins (bisphenol-A), nylon-6 (caprolactam), 2,4-D, selective solvents for refining lubricating oils, adipic acid, salicylic acid, phenolphthalein, pentachlorophenol and other derivatives in germicidal paints as a laboratory reagent and in dyes and indicators and as a slimicide, biocide and general disinfectant (Lewis, 1993). The world demand for phenol by use in 1993 was reported as (%) phenolic resins, 35 bisphenol-A, 30 caprolactam, 15 alkylphenols, 7 aniline, 5 and others, 8 (Wallace, 1996). 

Neutralization.—The preparation of reducing salts by neutralization requires no special comment. The most familiar examples are the soluble sulfites and sulfides. Since these are salts of weak, dibasic acids, it is not satisfactory to rely upon indicators for neutrality. The usual procedure is to prepare a solution of the base and divide it into two equal parts. One of these is saturated with the acid, producing the acid salt, and the other portion is then added, with the formation of the normal salt (example, preparation of (NH4)2S as a laboratory reagent). 

Synthesis. Benzenehexol is available only from laboratory reagent suppliers. The simplest laboratory preparation involves the aeration of the glyoxal—bisulfite addition product in sodium carbonate solution at 40—80°C, isolation of the sodium salt of tetrahydroxybenzoquinone, followed by acidification to obtain the free tetrahydroxy-p-benzoquinone in about 8% yield the latter is reduced with stannous chloride in boiling dilute hydrochloric acid solution to benzenehexol (77) in 77% yield (261). A similar procedure affords dipotassium rhodizonate (80) in good yield (262). 

Chloride. Potassium chloride, [CAS 7447-40-7]. KC1, colorless or white crystals strong saline taste. Occurs naturally as sylvite. Soluble in water slightly soluble in alcohol. Sp. gr. 1.987 mp 772VC sublimes at 1500ftC noncombustible low toxicity, Used in fertilizers, as a source of potassium salts pharmaceutical preparations photography spectroscopy plant nutrient salt substitute laboratory reagent. See also Fertilizer,... 

Bromelain preparations are widely used in medicine, as laboratory reagents, and to a lesser extent in industry. It is important to keep in mind that bromelain used... 

To prepare a solution of this salt for use as a laboratory reagent, explain why it is necessary to add nitric acid. (Compare with Question 1 under Mercurous Nitrate, page 232.)... 

In preparing a solution of stannous chloride for a laboratory reagent, what is the necessity of adding hydrochloric acid and of placing a piece of metallic tin in the bottle ... 

In searching for a relationship between antijuvenile hormone activities and epoxide chemical reactivity, we attempted to apply as a chemical probe the m-chloroperoxybenzoic-alkaline fluoride system, a reagent developed in this laboratory for preparation of acid labile epoxides (20). However, formation of hemiesters of 3,4-dihydroxy precocene, was the predominant reaction in the case of activated chro-mene structures. 

So-called stock solutions are solutions typically 10, 100 or 1000 times more concentrated than that ultimately required in the final solution. Stock solutions are particularly useful when the same ingredients are required in multiple test solutions, when various concentrations of these ingredients are required or simply for storage purposes. A useful example is fruit-flavoured drink concentrates (syrups or cordials) that are mixed/diluted with water to taste if these drinks were pre-diluted they would typically fill hundreds of bottles. The same principle applies to the preparation and storage of chemical concentrates for preparation of laboratory reagents, solutions and buffers. 

Today, more than 2000 enzymes are known. Several hundred have been isolated, many in pure or crystalline form. Over 400 are available commercially, some of them from as many as 10 different sources (8). Because of the relatively recent availability of increasing numbers of highly purified, very active enzyme preparations at reasonable cost, these biocatalysts are now commonly used as laboratory reagents for routine analytical work (16). 

British Drug Houses Laboratory Reagent yellow mercuric oxide was used for most runs. The preparation was not apparently improved by the use of freshly precipitated mercuric oxide. 

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