Aluminium absorbance

The aluminium absorbs the radiation, heats up and transfers the heat to xenon gas contained in the cell. As the temperature of the gas varies the curvature of a flexible mirror of antimony-coated collodion, forming a part of the cell, changes. Reflection of a light beam from this mirror, which is on the outside of the Golay cell, indicates its curvature and therefore the intensity of radiation absorbed by the cell. 

Aluminium is the third most abundant element on earth but it is known to have toxic effects that cause brain disease, bone disease, and anaemia. There is concern especially in relation to its possible role in Alzheimer s disease. The changes observed in animals exposed to aluminium are similar to those observed in patients with Alzheimer s disease. Aluminium has been found in some areas of the brain of victims of Alzheimer s at levels not too dissimilar from that in the brains of the animals exposed. Some of the findings and their interpretation are controversial. Unfortunately, the amounts of aluminium absorbed by the residents of Camelford are... 

Aluminium is much less sensitive to the attack by sulphur dioxide (SO2) than steel, galvanised steel and zinc. It has been shown that during exposure to industrial atmosphere, aluminium absorbs 1 mg-dm of SO2, while steel absorbs between 22 and 55 mg dm of SO2 under the same conditions [11]. 

Metal-carbon stretching frequencies occur in the region 775-420cm (12.90-23.81 pm) for metal-alkyl and metal-alkenyl bonds, aluminium absorbing at the high end of this range. 

Place an aluminium absorber (say 21.0 mg cm ) (M) on the second shelf of the counter s lead castle and count for 200 seconds. Repeat this after replacing the aluminium absorber by thicker absorbers in turn (e.g. 55, 82, 240, 712 and 1335 mg... 

Replace the aluminium absorber (1335 mg cm ) by a copper absorber of the same thickness on the second shelf and count for 200 seconds. Repeat using instead of copper, lead absorbers of the same thickness. Repeat using an iron absorber instead. 

To determine the background stick the Sr source at the bottom of aluminium absorber (1335 mg cm ) and count for 600 seconds. Calculate the count rate and subtract it from all count rates determined. 

Plot the corrected count rate against the thickness of the aluminium absorbers. Plot the corrected count rate, against the atomic number of the absorber used. Comment on your results. 

Aluminium oxide. The commercial material, activated alumina, is made from aluminium hydroxide it will absorb 15-20 per cent, of its weight of water, can be re-activated by heating at 175° for about seven hours, and does not appreciably deteriorate with repeated use. Its main application is as a drying agent for desiccators. 

A commonly used detector is a Golay cell, in which there is a far-infrared absorbing material, such as aluminium deposited on collodion, inside the entrance window of the cell. 

Several immersion treatments using solutions containing chromates have been developed for aluminium. It is not always clear to what extent the films formed can properly be called chromate films, i.e. films containing a substantial amount of a slightly soluble chromium chromate, but even if the film consists largely of aluminium oxide or hydroxide or other salt with chromate physically absorbed, it will still provide a reservoir of soluble chromate at the metal surface. Treatments fall into two classes alkaline and acid. The latter are of more recent development. 

Acid pickles Some of the acid pickles used to clean and etch aluminium alloy surfaces and remove oxide and anodic films, such as the chromic/ sulphuric acid pickle (method O of DEF STAN 03-2) and other chromic-acid bearing pickles (App. Foi DEF-151) probably leave on the surface traces of absorbed or combined chromate which will give at least some protection against mild atmospheres. 

Repeat the determination with a solution containing 100 jig of iron(III) and of aluminium ion the absorbance is unaffected. 

Discussion. Iron(III) (50-200 fig) can be extracted from aqueous solution with a 1 per cent solution of 8-hydroxyquinoline in chloroform by double extraction when the pH of the aqueous solution is between 2 and 10. At a pH of 2-2.5 nickel, cobalt, cerium(III), and aluminium do not interfere. Iron(III) oxinate is dark-coloured in chloroform and absorbs at 470 nm. 

Repeat the experiment using 50.0 mL of the iron(III) solution in the presence of 100 fig of aluminium ion and 100 fig of nickel ion at pH 2.0 (use a pH meter to adjust the acidity) and measure the absorbance. Confirm that an effective separation has been achieved. 

Fluoride, in the absence of interfering anions (including phosphate, molybdate, citrate, and tartrate) and interfering cations (including cadmium, tin, strontium, iron, and particularly zirconium, cobalt, lead, nickel, zinc, copper, and aluminium), may be determined with thorium chloranilate in aqueous 2-methoxyethanol at pH 4.5 the absorbance is measured at 540 nm or, for small concentrations 0-2.0 mg L 1 at 330 nm. 

Aluminium ions released from the dental silicate cement are also absorbed by hydroxyapatite and have a similar beneficial effect to that of fluoride (Halse Hals, 1976 Putt Kleber, 1985). Thus, the dental silicate cement confers protection against caries (dental decay) on surrounding tooth material. 

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