Microscale laboratory

Recently, microscale laboratory equipment has appeared in the undergraduate laboratory and has materially changed some of the operations and equipment you ll be using. Pay attention ... 

That s clear enough. You lose lots of your microscale product with a reduced-pressure (vacuum) distillation. As far as I know, no microscale laboratory manual has anyone perform this. Yes, you might be asked to... 

J. G. Ibanez, M. Hemandez-Esparza, C. Doria-Serrano, A. Fregoso-Infante, and M. M. Singh, Environmental Chemistry Microscale Laboratory Experiments, Springer, New York, NY, 2007. 

MSDSs must describe control measures and precautions for work on a variety of scales, ranging from microscale laboratory experiments to large manufacturing operations. Some procedures outlined in an MSDS may therefore be unnecessary or inappropriate for laboratory-scale work. An unfortunate consequence of this problem is that it tends to breed a lack of confidence in the relevance of the MSDS to laboratory-scale work. Many MSDSs comprehensively list all conceivable health hazards associated with a substance without differentiating which are most significant and which are most likely to actually be encountered. This can make it difficult for laboratory workers to distinguish highly hazardous matmals from moderately hazardous and relatively harmless ones. 

McMaster University. Microscale Laboratory Techniques, 1997/1998 available at http //www. chemistry.mcmaster.ca/" chem2o6/labmanual/microscale/complete.html (accessed January 17, 2009). 

The decrease within the majority of the environmental impact categories can be related to the savings in energy consumption, the reduction in solvent use and the increase in the reaction yield achieved in the microscale laboratory set-up. These... 

A clean work area is of utmost importance when working in the laboratory. The need for cleanliness is particularly great when working with the small amoimts of materials characteristic of microscale laboratory experiments. 

Review Introduction to Microscale Laboratory (Experiment 1) Technique 8 Filtration, Sections 8.1-8.6 Technique 9 Physical Constants, Melting Points New Technique 5 Measurement of Volume and Weight... 

Review Experiment 1 Introduction to Microscale Laboratory Techniques 5 and 6... 

The sand bath is used in some microscale laboratories to heat organic mixtures. Sand provides a clean way of distributing heat to a reaction mixture. To prepare a sand bath, place about a 1-cm depth of sand in a crystallizing dish or a Petri dish and then set the dish on a hot plate/stirrer unit. The apparatus is shown in Figure 6.5. Clamp the thermometer into position in the sand bath. You should calibrate the... 

Filtration is a technique used for two main purposes. The first is to remove solid impurities from a liquid. The second is to collect a desired solid from the solution from which it was precipitated or crystallized. Several different kinds of filtration are commonly used two general methods include gravity filtration and vacuum (or suction) filtration. Two techniques specific to the microscale laboratory are filtration with a filter-tip pipette and filtration with a Craig tube. The various filtration techniques and their applications are summarized in Table 8.1. These techniques are discussed in more detail in the following sections. 

Microscale Apparatus. The apparatus shown in Figure 15.2 is the one you are most likely to use in the microscale laboratory. If your laboratory is one of the better-equipped ones, you may have access to spinning-band columns like those shown in Figure 15.10. The distillation temperature can be monitored most accurately by using a partial immersion mercury thermometer (see Technique 13, Section 13.3). 

Chapter lOW), indicating its location online. Furthermore, an icon will be used in the margin to indicate website material that will be of interest to the user. We hope this treatment of the laboratory will make the more important aspects of the basic text easier to access and will speed your laboratory work along. We then give you a few words of advice, which, if they are heeded, will allow you to avoid many of the sand traps you wiU find as you develop microscale laboratory techniques. Finally, we wax philosophical and attempt to describe what we think you shorUd derive from this experience. 

Study the experiment before you come to lab. This rule is a historical plea from all laboratory instructors. In the microscale laboratory it takes on a more important meaning. You wiU not survive if you do not prepare ahead of time. In microscale experiments, operations happen much more quickly than in the macroscale laboratory. Your laboratory time wiU be overflowing with many more events. If you are not familiar with the sequences you are to follow, you wUl be in deep trouble. Although the techniques employed at the microscale level are not particularly difficult to acquire, they do demand a significant amount of attention. For you to reach a successful and happy conclusion, you cannot afford to have the focus of your concentration broken by having to constantly refer to the text during the experiment. Disaster is ever present for the unprepared. 

The smaller quantities used in the microscale laboratory carry with them a reduction in hazards caused by fires and explosions hazards associated with skin contact are also reduced. However, care must be exercised when working with even the small quantities involved. 

Procedure. In the microscale laboratory, two different t) es of melting-point determinations are carried out (1) simple capillary melting points and (2) evacuated melting points. 

Packed Columns. In packed columns the liquid (stationary) phase in contact with the sample contained in the mobile gas phase is maximized by coating a finely divided inert support with the nonvolatile liquid. The coated support is carefully packed into the column so as not to develop empty spaces. Packed columns are usually i or inch in diameter and range from 4 to 12 feet in length. These columns are particularly useful in the microscale laboratory, since they can be used for both analytical and preparative GC. Simple mixtures of 20-80 jlL of material can often be separated into their pure components and collected at the exit port of the detector. Smaller samples (0.2-2.0 (jlL range) will exhibit better separation. 

Preparative GC in the microscale laboratory often replaces the macroscale purification technique of fractional distillation. Distillation is impractical with less than 500 xL of liquid. 

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