Standards laboratory weights

Percentage compaction usually is used to measure soil density in a fill situation. Generally, the maximum Proctor specific weight (dry, Ib/ft ), determined by a standard laboratory test, is set up as the standard for the soil. Normally, 90-100% compaction is specified. 

Asphalt concrete is properly proportioned to resist the potentially damaging effects in the road. Asphalt concrete paving mixtures should be evaluated for the following properties stability, flow, air voids, stripping resistance, resilient modulus, compacted density, and unit weight. Table 4.18 provides a list of standard laboratory tests that are presently used to evaluate the mix design or expected performance of fresh and hardened asphalt concrete. 

Iridium s most common use is as an alloy metal that, when added to platinum, makes it harder and more durable. It is also mixed with other metals to make electrical contacts, thermocouples (two dissimilar metals joined to form a special type of thermometer), and instruments that will withstand high temperatures without breaking down. It is also used to make special laboratory vessels because iridium will not react with most chemical substances. An alloy of iridium and platinum is used as the standard kilogram weight because it is noncorrosive and will not oxidize and, thus, change its weight over long periods of time. 

Annual Book of ASTM Standards, ANSI/ASTM E617-97 Standard Specification for Laboratory Weights and Precision Mass Standards, Book of Standards Vol. 14.04, ASTM, 2003. 

From ASTM Designation E 617 Standard Specification for Laboratory Weights And Precision Mass Standards, reprinted with permission. 

Tolerances The analytical weights meet the tolerances of the American National Standard ANSI/ASTM E617, Laboratory Weights and Precision Mass Standards. This standard is incorporated by reference and should be consulted for full descriptions and information on the tolerances and construction of weights.3 Where quantities of 25 mg or less are to be accurately weighed, any applicable corrections for weights should be used. 

Class 2 weights are used as working standards for calibration, built-in weights for analytical balances, and laboratory weights for routine analytical work. 

T. W. Lashof and L. B. Macurdy, Precision Laboratory Standard of Mass and Laboratory Weights, Natl. Bur. Stand. Cir. 547, U.S. Government Printing Office, Washington, DC (1954). 

Male Wistar rats (body weight approximately 250 g). House in groups of four under standard laboratory conditions and free access to food (rat chow) and water. 

Use Alloy with platinum for ammonia fuel-cell catalyst, electric contacts and thermocouples, commercial electrodes and resistance wires, laboratory ware, extrusion dies for glass fibers, jewelry. Primary standards of weight and length. 

Investigators who wish to check their measurement techniques against those of a standardizing laboratory can buy a sample of silicon powder from the U.S. Bureau of Standards. These samples, known as Standard Reference Material 640, were made available in 1974 [11.8]. The Bureau states the weighted average of the lattice parameter of this material to be 5.43088 A, with an estimated standard error of 3.5 X 10 A. 

While all the above methods have been used very successfully on standard laboratory scale, they also have significant potential for rapid synthesis on medium scale (up to several kg) and possibly even larger. High-loading resins can bind an equal weight of substrate and so are efficient in terms of volume. ... 

Materials. Three samples of poly-7-benzyl-L-glutamate were studied. Polymer I was obtained by polymerizing 7-benzyl A-carboxy-L-glutamate anhydride by sodium methoxide in DMF and polymer II by a similar polymerization using n-hexylamine as initiator. Both were purified by reprecipitation. The molecular weights determined from the viscosity-molecular weight ratio of Doty et al. (4) were 67,000 for polymer I and 21,000 for polymer II. Polymer III was a commercial sample (Pilot Chemical Co.) of molecular weight 275,000. All solvents were purified by standard laboratory procedures. 

The Standard Atomic Weights apply to the elements as they exist naturally on Earth, and the uncertainties take into account the isotopic variation found in most laboratory samples. Further comments on the variability are given in the footnotes. 

In the laboratory we determine the mass of an object by using a balance. A balance compares the mass of the object to a set of standard masses (weights). For example, the mass of an object can be determined by using a single-pan balance (see Figure 5.4). 

The falling weight or dart drop test method simulates actual day-to-day abuse and can be carried out either on standard laboratory specimens or on the articles themselves. Failure may occur in various ways ranging from brittle to ductile failure (Figure 14). Particular care must be taken to avoid the brittle failure by proper selection of grade. At temperatures below -20 °C, elastomer-modified PP is more impact resistant than PP copolymer and homopolymer. 

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