Using chemical tests

Carboxylic acids are soluble in either aqueous NaOH or NaHC03. The other common group of organic acids, phenols, are weaker than the carboxylic acids. Phenols are only soluble in aqueous NaOH. Di- and trinitrophenols are stronger acids than most other phenols, so they are also soluble in aqueous NaHCOj. 

The neutralization equivalent is a useful means of determining the molecular weight of a carboxylic acid. The process begins with a simple neutralization reaction of acid with standard base (usually sodium hydroxide). The reaction is 

Written in this form, you see that the equivalents (or milliequivalents) of acid are equal to the equivalents of base. The equivalent weight of the acid is the grams of acid divided by the equivalents of base. The equivalent weight of monoprotic acid is equal to the molecular weight. The equivalent weight of diprotic acid is equal to half the molecular weight. 

Aaron -was envied tor being the first student -. in his chemistry class-with an iSpectrometer. = 

Next you shift your focus to organometallics, those organic compounds that incorporate metals into their structure. Here you study one of the most useful organic reactions, the Grignard reaction. 

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You are given samples of propanal, 2-propanone, and ethanoic acid. Describe how you would use chemical tests, such as acid—base indicators and oxidizing agents, to distinguish among the three compounds. 

Five of the seven respondents who use a matrix also use chemical testing results as a data source. A similar number review the matrix during qualitative hazard evaluation studies (i.e., hazard and operability [HAZOP] studies, what-if, checklist, etc.). 

Using chemical tests, how would you distinguish among 2-pentanone, 3-pentanone, and pentanal ... 

In addition to bioassays, HPLC and TLC analyses, and UV and RI detectors, one can use chemical tests to locate compounds of interest. For example, when desalting a sample with a BioGel P-2 column, the NaCl-containing fractions can be located by adding a small aliquot of each ftaction to parallel tubes contaming a... 

The herbicide 3-amino-1,2,4-triazole is effective against developing rather than mature plant tissues. Fredrick and Gentile (1961) have used chemical tests and infrared spectra as evidence for a o-glucose-3-amino-1,2,4-triazole adduct (CXXX) as a product of the metabolism of this herbicide by treated plants. 

However, antioxidant screening in complex mixtures of plant origin requires simple and rapid in vitro models for a possible combination with chromatographic techniques such as TLC, HPLC, HSCCC, or CPC. The reduction of the stable free-radical DPPH (l,l-diphenyl-2-picryUiydrazyl) by antioxidant substances is currently the most widely used chemical test for the screening of plant extracts. Only a few bioassay-guided fractionation processes have also evaluated the antimicrobial, antibacterial activity, or cytotoxicity of fractions enriched in specific flavonoids by using HSCCC or CPC liquid-liquid systems [30, 35]. 

The presence of functional groups can be established using chemical tests, for example bromine water for alkenes, and by infrared spectroscopy (Chapter 21). 

If oil and water are mixed as an emulsion, dehydration becomes much more difficult. Emulsions can form as oil-in-water or water-in-oil if mixed production streams are subjected to severe turbulence, as might occur in front of perforations in the borehole. Emulsions can be encouraged to break (or destabilise) using chemicals, heat or just gentle agitation. Chemical destabilisation is the most common method and laboratory tests would normally be conducted to determine the most suitable combination of chemicals. 

In the light of these results there is little doubt that the t-curve (or a,-curve] used in testing for microporosity should be based on the isotherm of a nonporous solid chemically similar to the substance under test and not on a reference isotherm which happens to have the same value of the c-constant. 

The procedures used for estimating the service life of solid rocket and gun propulsion systems include physical and chemical tests after storage at elevated temperatures under simulated field conditions, modeling and simulation of propellant strains and bond tine characteristics, measurements of stabilizer content, periodic surveillance tests of systems received after storage in the field, and extrapolation of the service life from the detailed data obtained (21—33). 

Liquid Fabric Softeners. The principal functions of fabric softeners are to minimize the problem of static electricity and to keep fabrics soft (see Antistatic agents). In these laundry additives, the fragrance must reinforce the sense of softness that is the desired result of their use. Most fabric softeners have a pH of about 3.5, which limits the materials that can be used in the fragrances. For example, acetals cannot be used because they break down and cause malodor problems in addition, there is the likelihood of discoloration from Schiff bases, oakmoss extracts, and some specialty chemicals. Testing of fragrance materials in product bases should take place under accelerated aging conditions (eg, 40°C in plastic bottles) to check for odor stabiUty and discoloration. 

Sacrificial adsorption agents such as lignosulfonates (148—151) can be used to reduce the adsorption of more expensive polymers and surfactants. Other chemicals tested include poly(vinyl alcohol) (152), sulfonated poly(vinyl alcohol) (153), sulfonatedpoly(vinylpyrrohdinone) (153), low molecular weight polyacrylates (154), and sodium carbonate (155). 

The development of rehable uv analysis permitted the dependable detection and assay of the provitamins and vitamins. Prior to this, the Lieberman-Bouchard chemical test was used, but the color reaction gave many false positives and was relatively inaccurate. 

Beverages. The quahty control for carbonated beverages encompasses all aspects of the product from actual chemical components to the physical condition of the container. The beverage is evaluated using laboratory tests as well as in-line monitors. 

Testing and Control. Analysis and testing are required whenever a new plating solution is made up, and thereafter at periodic intervals. The analyses are relatively simple and require Httie equipment (78—80). Trace metal contaminants can be analy2ed using spot tests, colorimetricaHy, and with atomic absorption spectrophotometry (see Trace and residue analysis). Additives, chemical balance, impurity effects, and many other variables are tested with small plating cells, such as the Hull cell developed in 1937 (81,82). 

Application. In the past, the yield for a chemical process has heen established at 89.6 percent with a standard deviation of 3.4 percent. A new supplier of raw materials will he used and tested for 7 days. 

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