Bromine atomic weight

This method follows the ASTM D 1159 and D 2710 procedures and the AFNOR M 07-017 standard. It exploits the capacity of the double olefinic bond to attach two bromine atoms by the addition reaction. Expressed as grams of fixed bromine per hundred grams of sample, the bromine number, BrN, enables the calculation of olefinic hydrocarbons to be made if the average molecular weight of a sufficiently narrow cut is known. 

AN1) Name/Symbol Atomic weight Density at 20°C Melting point (°C)3) 35 Bromine Br 79.90... 

Consider the proper placement of tellurium and iodine in the periodic table, as shown in Figure 1-3. Te has the heavier atomic weight. The chemical properties of tellurium are like those of selenium because both are semi-metallic elements that form compounds like those of sulfur. Iodine resembles bromine because these elements are nonmetallic halogens that form compounds like those of chlorine. Therefore, the order in the table cannot be based solely on atomic weight. 

The assumption that PBBs and PBDEs share many toxicological characteristics with PCBs also does not consider geometrical differences due to the higher atomic weight and considerably larger molecular volume of bromine compare to chlorine (Hardy 2000, 2002). These differences contribute to dissimilar physical/chemical properties that can influence the relative toxicokinetics and toxicities of the chemicals. 

The atomic weight of bromine.—The at wt. of bromine has been determined by methods which follow in principle those employed for chlorine. A. J. Balard (1826),14 the discoverer of bromine, transformed a known weight of potassium bromide into the sulphate, and also reduced silver bromide to metallic silver by means of zinc the numbers 74 7 and 75 3 were respectively obtained. J. von Liebig (1826)... 

When the benzyl and xylyl bromides were brought in contact with indium tubes for sampling, the indium was quickly discolored and pitted. The spectra of the material so taken up were recorded despite the clear evidence of reaction between the indium and the bromide. Relative intensities in the low voltage spectra and suggested identities of the compounds responsible for the peaks are shown in Table II. The chief result of indium attack on a-bromo-o-xylene was expected to be removal of a bromine atom to produce a xylyl radical. If this were the case, the major stable products should be xylene polymers of molecular weight 210, 314,... 

If the mass percent of the isotopes of an element is known, then the average atomic weight can be calculated. For example, naturally occurring bromine has one isotope with a mass of 78.918 amu and makes up 50.69% of a bromine sample. Another isotope has a mass of 80.916 amu and an abundance of 49.31%. The average atomic mass of bromine equals the percent abundance of the first isotope divided by 100 times the mass percent of the isotope plus the percent abundance of the second isotope divided by 100 times the mass percent abundance of the second isotope (.5096) (78.918) plus (.4931) (80.916) equals 79.90, the average atomic mass of bromine. 

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