Hood index

Kennedy, B. P., Kawachi, I. and Prothrow-Stith, D. (1996), Income distribution and mortality cross-sectional ecological study of the Robin Hood index in the United States , British MedicalJournal, 312, 1004-1007. 

The evaluation methods could be direct, e.g., measuring a containment index, or indirect, e.g., measuring pressure loss or velocity distribution. The direct methods are used to measure the performance of a hood or an inlet during periodic preventive maintenance. Indirect methods are used for verifying or checking on a daily basis (routine checks). How often each method is used depends on the availability of instrumentation and qualified personnel, since direct measurement of a hood s performance can be both expensive and difficult. On the other hand, indirect methods are usually easier to use and can sometimes include inexpensive, continuously monitoring instruments (pressure gauges or velocity indicators). 

To size the fan it is necessary to know the total air volume and the pressures in the system. These are calculated from the losses in the system on the longest or index leg, and begin with the hood. The hood entry loss can be expressed as 0.6 of the velocity head and is accurate enough for first estimates. The losses are then calculated on the velocities in the ducts. Each change of direction means a small loss in each length of duct. Added to the pressure drop loss across the collector and the outlet losses, these give the total static pressure required in the system. 

Bromoallylamine discolors slowly even when stored at 0° in a dark container. The refractometer to be used for determination of the refractive index should be placed in a good hood. 

In a hood, to a well-stirred dispersion of 62 gm (1.35 moles) of methyl-hydrazine, 175 ml of chlorobenzene, and 20 gm of powdered, anhydrous sodium sulfate is added dropwise, with cooling, 61 gm (0.663 mole) of freshly distilled l-chloro-2-propanone. After the addition has been completed, the reaction mixture is stirred for 1 hr. The moist sodium sulfate is separated by filtration and the filtrate is distilled. The fraction boiling between 60°C and 64°C is collected as product, yield 16.8 gm (31 %) of a yellow liquid. On redistillation the boiling point is raised slightly to 61°-64°C, index 1.4300. 

The major problem with both of these solutions is their toxicity. The first solution should only be used in a fume hood, and the second is so toxic that it should not be used at all. An alternative solution, albeit a bit messier, is common kitchen com oil. It does not match the index of refraction as closely as do the two solutions mentioned above, but it does the job and is safe to use. The com oil can be removed with soap and water. 

Patel JM, Block ER, Hood Cl. 1984. Biochemical indexes of cyclophosphamide- induced lung toxicity. Toxicol Appl Pharmacol 767 128-138. 

Subsequently, a completely remote, bench-scale apparatus was developed in the late 1960s Figure 1 shows the apparatus. The control box shown to the left can be mounted outside a fume hood and used to control and monitor a reaction remotely. Next to the control box is a turntable with four indexing stations (i.e., decant, wash, filter, etc.), while on the far right is the 600-ml reaction kettle... 

In a chemical fume hood, remove acrolein (Polysciences, Warrington, Pennsylvania) from bottle using a syringe. At a 2% concentration, it is obnoxious, but not harmful. It penetrates tissue rapidly and aides in the ability to rapidly dissect the embryo with minimal overall distortion. If possible, do the dissection in an exhaust hood. At the very least, work in a well-ventilated space where traffic is minimal. It is possible to eliminate acrolein from the fixative, and simply wait longer between puncturing and dissection, as paraformaldehyde also penetrates relatively rapidly. If acrolein is used, consult the Merck index or the Material Safety Data Sheet for acrolein. 

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