Aluminium Table

Aluminium has been included in the UK TDS only since 1988, owing to the difficulty of obtaining reliable analytical data in the presence of environmental levels of aluminium (Table 7.7). Dietary exposures for mean and 97.5th percentile for UK consumers in 1997 were 3.2 mg/day and 5.7 mg/day respectively,10 similar to the population exposure. All the estimated exposures were well below the JECFA PTWI of 7 mg/kg bodyweight, which is equivalent to 60 mg/day for a 60 kg adult. The population estimate is similar to dietary exposures reported for other countries. A dietary exposure in the USA of 11.5 mg/day was reported for 14-16-year old males,8 while dietary exposures in an Italian TDS were between 2.3-6.3 mg/day.37... 

When the relative composition of the biosphere is compared to that of the lithosphere, a new dimension for iron is noted. Iron now constitutes about 1.3 atoms of every 100 atoms of the lithosphere and, on a weight per cent basis, iron in crustal abundance ranks fourth in number, only behind oxygen, silicon, and aluminium (Table 7.3 in Geochemistry, Wedepohl, 1971, p. 60). On a comparative basis, the lithosphere is a dry metallic aluminium silicate, whereas the biosphere is wet and carbonaceous (Deevey, 1970). Iron is very limited in the hydrosphere and atmosphere. 

The dissolution potential of intermetallic compounds differs from that of aluminium (Table B.2.1). Intermetallic compounds can be... 

Prolonged contact with concrete, even in the presence of humidity, leads only to a superficial attack, shown by testing results with concrete blocks with embedded unprotected aluminium (Table G.4.1) that were exposed to various media, including marine atmosphere [3]. The zone of emergence in the air is not prone to corrosion (see Section B.2.7). 

As the carbon content of aluminium is generally low, combustion methods as such are only of limited use, as they suffer from blank problems and lack of sensitivity (1 /tg/g). In round robins organized by BCR on the analysis of carbon in primary ingot aluminium (Table V-8) only photon (or helium-3) activation analysis in combination with combustion and deuteron activation analysis in combination with Kjeldahl led to significant, and probably also accurate results. 

The measurements are done at a table with two in X- and Y- direction moveable axes. The measured structures, by an Aluminium-alloy, are situated at the X-axis. The sensor at the Y-axis scans the structure step by step. The position and the electoral signal are measured for every step. A computer controls the movement of the sensor and the data acquisition. 

By reference to the outline periodic table shown on p. (i) we see that the metals and non-metals occupy fairly distinct regions of the table. The metals can be further sub-divided into (a) soft metals, which are easily deformed and commonly used in moulding, for example, aluminium, lead, mercury, (b) the engineering metals, for example iron, manganese and chromium, many of which are transition elements, and (c) the light metals which have low densities and are found in Groups lA and IIA. 

Both these molecules exist in the gaseous state and both are trigonal planar as indicated by reference to Table 2.8. However, in each, a further covalent bond can be formed, in which both electrons of the shared pair are provided by one atom, not one from each as in normal covalent bonding. For example, monomeric aluminium chloride and ammonia form a stable compound ... 

The aluminium ion, charge -I- 3. ionic radius 0.045 nm, found in aluminium trifluoride, undergoes a similar reaction when a soluble aluminium salt is placed in water at room temperature. Initially the aluminium ion is surrounded by six water molecules and the complex ion has the predicted octahedral symmetry (see Table 2.5 ) ... 

The data in Tables 4.2 and 4.3 refer to ions in aqueous acid solution for cations, this means effectively [MlHjO), ]" species. However, we have already seen that the hydrated cations of elements such as aluminium or iron undergo hydrolysis when the pH is increased (p. 46). We may then assume (correctly), that the redox potential of the system... 

A non-metal or weakly electropositive metal X in Group III of the periodic table would be expeeted to form a covalent volatile hydride XHj. In fact, the simplest hydride of boron is BjHf, and aluminium hydride is a polymer (AlHj) . 

Boron and aluminium halides show many similarities but also surprising differences. Table 7.2 gives the melting and boiling points of the MX3 halides. 

The properties of the head element of a main group in the periodic table resemble those of the second element in the next group. Discuss this diagonal relationship with particular reference to (a) lithium and magnesium, (b) beryllium and aluminium. 

We have reproduced in a few Tables (AI6.3-AI6.15) for cables that are used more com-nionly in all voltage ratings and with aluminium conductors. For other cables and copper conductor cables, refer to the manufacturers of their catalogues. 

Copper, aluminium, steel and galvanized iron are the most widely used metals for the purpose of grounding. Choice of any of them will depend upon availability and economics in addition to the climatic conditions (corrosion effect) at the site of installation. In Table 22.3 we provide a brief comparison of these metals for the most appropriate choice of the metal for the required application. 

The ground conductor can be of aluminium, GI or copper, as discussed earlier. A humid or a chemically contaminated location is corroding in nature. Aluminium has a rapid reaction and is fast corroding. At such locations, use of GI or copper conductor would be more appropriate. Table 22.4 suggests the ground conductor sizes for aluminium conductor power cable.s for small and medium-ratine feeders when aluminium is used for the ground... 

Table 22.4 Size of aluminium ground conductor for different sizes of power cables for a grounding system...

Aluminium busbars, from Tables 30.4 and 30.6 Electrical conductivity = 1... 

The minimum shearing strength of aluminium is 1650 kg/cm (Table 30.1) which is much larger than the actual force to which the busbars will be subject, in the event of a fault. They are thus more than adequate in cross-section and numbers. Other than bending stress, there is no significant tensile or shearing force acting on the busbars. 

Correct-overlapping of joint is an important parameter to make a good joint, as well as to allow no excessive heat at the joints. Based on the recommendations of the leading aluminium section manufacturers, the desired overlaps are shown in Table 29.1, and two such joints are illustrated in Figures 29.4 and 29.6. Laboratory tests and site experience have revealed that a larger overlap is of no additional benefit. For larger sections also, only... 

In Table 30.1 we provide the general properties of aluminium and copper conductors. The table also makes a general comparison between the two widely used metals for the purpose of carrying current. 

The resistivity and conductivity of standard annealed copper and a few recommended aluminium grades being used widely for electrical applications are given in Table 30.1. Their corresponding current-carrying capacities in percent, with respect to a standard reference (say, 100% lACS) are also provided in the table. 

Table 30.1 Selected properties (average) of copper and aluminium at 20 C...

Table 30.4 Current ratings for rectangular aluminium sections, grade E91-E (6101 A)...

Table 30.6 Grades of aluminium alloys for electrical purposes...

X (p in Q cm) as in Table 30.1 /= frequency of the system in Hz p = effective permeability of the medium in which the field exists (aluminium in the present case), and will depend upon the electric field induced in the enclosure... 

Typical values of the energy to form vacancies are for silver, lOSkJmol and for aluminium, 65.5kJmol These values should be compared with the values for the activation enthalpy for diffusion which are given in Table 6.2. It can also be seen from the Table 6.2 that die activation enthalpy for selfdiffusion which is related to the energy to break metal-metal bonds and form a vacant site is related semi-quantitatively to the energy of sublimation of the metal, in which process all of the metal atom bonds are broken. 

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