Barium aluminates

Aluminum nitrate nonahydrate is prepared by dissolving aluminum or aluminum hydroxide in dilute nitric acid, and crystaUi2ing the product from the resulting aqueous solution. It is made commercially from aluminous materials such as bauxite. Iron compounds may be extracted from the solution with naphthenic acids (21) before hydrate precipitation. In the laboratory it is prepared from aluminum sulfate and barium nitrate. 

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

Barium is reported in the kiln spill in three different forms water-soluble, eg, BaS, BaO acid-soluble, eg, BaCO, aluminate, siUcate, ferrate and insoluble, eg, unreduced barite. 

Numerous other specialty cements composed of various magnesium, barium, and strontium compounds as siUcates, aluminates, and phosphates, as well as others, are also produced (85). 

The difference in catalytic activity between the La- and the Ba-based hexa-aluminates results from the following reasons the first difference is the valence of cation in the mirror pleuie between tri-valent lanthanum ion and di-valent barium ion. The second is the crystal structure between magnetoplumbite and P-alumina, which are different in the coordination of ions and concentration of Frenkel-type defect in mirror plane. The redox cycle of transition metal in hexa-aluminate lattice, which closely related with catalytic activity, is affected sensitively with these two factors. 

Calcium aluminate chloride, phase in Portland cement clinker, 5 472t Calcium aluminate fluoride, phase in Portland cement clinker, 5 472t Calcium aluminoferrite, phase in Portland cement clinker, 5 472t Calcium aluminoferrite hydrate, 5 477t Calcium—aluminum alloys, 4 530 Calcium amalgam, 22 773 Calcium ammonium nitrate, 2 724 Calcium analysis, of water, 26 37 Calcium A zeolite, separation of hydrocarbons by, 16 823 Calcium—barium—silicon alloy, 22 519 Calcium-bearing manganese silicon,... 

The major reactions are complicated by a number of minor or secondary reactions, and by impurities in the raw materials. As a result the black ash may contain 1 to 2 per cent, of sodium silicate to If per cent, of sodium aluminate 1 per cent, of sodium ferrous sulphide small proportions of sodium cyanide and thiocyanate derived from the nitrogen of the coal a relatively small amount of ultramarine etc. Proposals to use barium carbonate, etc., in place of limestone in the black-ash process are indicated in connection with the preparation of sodium carbonate from sodium sulphide. 

Barrer and Mainwaring (20) report the use of metakaolin as the aluminosilicate raw material for reaction with the hydroxides of K and Ba as well as the binary base systems Ba-K and Ba-TMA to form zeolites. Zeolite phases previously synthesized in the analogous hydrous aluminosilicate gel systems were crystallized with KOH, including phillipsite-, chabazite-, K-F-, and L-type structures. The barium system yielded two unidentified zeolite phases (Ba-T and Ba-N) and a species Ba-G,L with a structural resemblance to Linde zeolite L. Ba-G,L was reported previously by Barrer and Marshall (21) as Ba-G. Similar phases were formed in the Ba-K system and in the TMA-Ba system where, in addition, erionite-type phases were formed. The L-type structures are said to represent aluminous analogs of the zeolite L previously reported (22). 

This is by far the most frequently encountered interference in AAS. Basically, a chemical interference can be defined as anything that prevents or suppresses the formation of ground state atoms in the flame. A common example is the interference produced by aluminium, silicon and phosphorus in the determination of magnesium, calcium, strontium, barium and many other metals. This is due to the formation of aluminates, silicates and phosphates which, in many instances, are refractory in the analytical flame being used. 

Barium hexa-aluminate. BaAli20i9, being a compound of high practical importance, is usually synthesized via thermal decomposition of alkoxides. 

Europium doped barium aluminates of the type Bai xEuxMg2Ali6027 are used as a blue component in fluorescent lamps, and are also being investigated for possible use in flat panel displays. The crystal structure of this material is characterized by an intergrowth of spinel and magnetoplumbite units (See 3.4.2 and 3.11). 

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