Glassware preparation

The dictionary defines simulation as the representation of the behavior or characteristics of one system through the use of another system (/). The use of simulations in chemistry is prevalent enough to have been the subject of educational research (2-5). In a lot of the corresponding software, the objects being represented are the chemicals and pieces of equipment of an actual laboratory or, equally common, cartoon-style abstractions of chemical concepts. Students thus get to manipulate simulated glassware, prepare solutions by dragging icons, or shuffle electrons to satisfy the rules of quantum mechanics. In software for beginners, they may on occasion even cause fake explosions. 

This is the second edition of this book and, although some sections have been extensively revised, others are little changed. For instance the details of glassware preparation have not changed over the last 10 years but what has changed is the use of glassware which has been superseded almost entirely with presterilised plastic ware. 

Equipment and methods will be operated/performed in accordance with cGMPs. Instruments will be calibrated, automatic analyzers and equipment will be qualified computer-related systems will be validated analytical methods from USP/NF will be verified and glassware preparation, media preparation, and noncompendial methods will be validated. 

Ni(cod)2 is an air-sensitive complex requiring some care in handling. The yellow crystalline material (used as purchased, without further purification) is transferred in a glovebag under N, or in Schlenk-type glassware. Preparation of a stock solution of Ni(cod)2 (ca. 0.1 M in toluene) is convenient for small-scale reactions. This yellow solution can be stored in a freezer for at least 2 months with only slight deposition of a black precipitate. 

Solutions, wrapped glassware prepared with caps or foil, etc. 

All glassware should be scrupulously clean and, for most purposes, dry before being employed in preparative work in the laboratory. It is well to develop the habit of cleaning all glass apparatus immediately after use the nature of the dirt will, in general, be known at the time, and, furthermore, the cleaning process becomes more difficult if the dirty apparatus is allowed to stand for any considerable period, particularly if volatile solvents have evaporated in the meantime. 

The accuracy of a standardization depends on the quality of the reagents and glassware used to prepare standards. For example, in an acid-base titration, the amount of analyte is related to the absolute amount of titrant used in the analysis by the stoichiometry of the chemical reaction between the analyte and the titrant. The amount of titrant used is the product of the signal (which is the volume of titrant) and the titrant s concentration. Thus, the accuracy of a titrimetric analysis can be no better than the accuracy to which the titrant s concentration is known. 

I. 000 X 10- 1.000 X 10-k 1.000 X 10-k and 1.000 X 10- M from a 0.1000 M stock solution. Calculate the uncertainty for each solution using a propagation of uncertainty, and compare to the uncertainty if each solution was prepared by a single dilution of the stock solution. Tolerances for different types of volumetric glassware and digital pipets are found in Tables 4.2 and 4.4. Assume that the uncertainty in the molarity of the stock solution is 0.0002. 

The solutions must be carefully prepared so as to be free of dust particles and other extraneous scatterers. Filtration through sintered glass or centrifugation is widely used to clarify solutions of particles which would compete with polymeric solutes. This concern for cleanliness also extends to glassware, especially scattering cells. A fingerprint on the viewing window is disastrous ... 

Caution Since the toxic gas phosgene is employed in this preparation, the reaction should be performed in an efficient hood. The glassware, which may be coated with a solution of phosgene, should be washed before it is removed from the hood. 

Practical experience enables us to emphasize the simplicity and the efficiency of the activation of aldehydes by their conversion into N- -haloalkyl)heteroarylium halides upon treatment with an azine and a thionyl halide. Preparation of these salts requires a minimum of precautions, and a wide variety of solvents can be used. Special glassware and/or the use of an inert gas is not necessary. Tire salts can be reacted under numerous experimental conditions and, in most cases, it is unnecessary to isolate them. Tire flexibility of the method represents an interesting feature for the study of the reactivity of A-(l-haloalkyl)heteroarylium halides and deserves further investigations in this held. Many elegant compromises can be found in a judicious choice of the precursors and of the experimental conditions, and it is possible to design readily a salt suitable for each individual purpose. 

Standard tests are the American and the German . Several other continental standards are essentially based on the German. The present British standard relates only to laboratory glassware. The German and American standards differ in a number of details and to try to establish an international uniformity the ISO have issued recommended procedures ". A new British standard in preparation will be based on these procedures. 

Caution Since the odor of the thiophenol (benzenethiol) used in this preparation is unpleasant, both steps of this preparation should be conducted in a hood and the glassware used should be washed before it is removed from the hood. 

Lam, R. B., and Isenhour, T. L., Minimizing Relative Error in the Preparation of Standard Solutions by Judicious Choice of Volumetric Glassware, Anal. Chem. 52, 1980, 1158-1161. 

Precautions. Prepared materials were treated with techniques used for radioactive or infectious material. The work was performed in an isolated laboratory. Glassware and tools were segregated. The hood was... 

As already discussed in Section 2.2, crystalline dimethylsilanediol 53 can be prepared by hydrolysis from hexamethylcyclotrisilazane 51, from dimethoxydimethyl-silane [40], and from octamethylcyclotetrasilazane (OMCTS) 52. The most simple preparation of 53 is, however, controlled hydrolysis of dimethyldichlorosilane 48 in the presence of (NH4)2C03 or triethylamine [41]. Likewise, hydrolysis of hexam-ethylcyclotrisiloxane 54 and of octamethylcyclotetrasiloxane 55 eventually gives rise to dimethylsilanediol 53. In all these reactions the intermediacy of the very reactive dimethylsilanone 110 has been assumed, which can be generated by pyrolytic [42, 43] and chemical methods [44—46] and which cyclizes or polymerizes much more rapidly, e.g. in contact with traces of alkali from ordinary laboratory or even Pyrex glassware [40, 47] to 54, 55, and 56 than trimethylsilanol 4 polymerizes to hexamethyldisiloxane 7. Compound 111 is readily converted into dimethylsilanone 110 and MesSil 17 [46] (Scheme 3.6). 

All chemicals are of reagent grade bidistilled water is used throughout this work. Anionic surfactant AOT is vacuum-dried for 24 h at 333 K directly before use. Water-free hydrocarbon (e.g., extra dry isooctane, water <30 ppm) is used for a ME preparation. All glassware is air-dried at 393 K. 

Anon., Lab. Accid. Higher Educ., item 8, Barking, HSE, 1987 During the preparation of the As-oxidc in glassware by oxidation with hydrogen peroxide (conditions unknown), an explosion occurred, possibly due to presence of impurities. 

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