Borate poisoning

If borate is found to be present, transfer the centrifugate from Group II to a small crucible, heat to expel hydrogen sulphide (do not evaporate to dryness), and allow to cool. Add 2-3 drops concentrated hydrochloric acid and 5-6 drops methanol, and heat on a water bath until the solution is almost evaporated to dryness. Repeat the addition of hydrochloric acid and methanol, and evaporate to dryness on the water bath. If borate is the only interfering ion, dissolve the residue in 2 ml of 2m hydrochloric acid, and continue the analysis for cations. The borate is volatilized as methyl borate (poisonous). 

A. The mechanism of borate poisoning is unknown. Boric acid is not highly corrosive, but is irritating to mucous membranes. It probably acts as a general cellular poison. Organ systems most commonly affected are the skin, gastrointestinal tract, brain, liver, and kidneys. 

Their principal parent compound is Hydrofluoric (or Phthoric) Acid Gas. (Hydrogen Fluoride), HF, mw 20.01 colorless, very poisonous gas, density 0.713(Air l,0), sp gr of liquid 0.988 at +13.6°, fr p -83°, bp +19-4° sol in w or ale. Can be prepd by distilling from a mixture of Ca fluoride (fluorspar) and sulfuric acid. Used as an additive in liquid rocket proplnts and in refining of uranium. Also as fluorinating agent in org and inorg reaction prepn of A1 fluoride, other fluorides, fluoro-borates, fluomcarbonaces, fluorocarbons and fluorosili cates... 

A great advantage of the borates is that the ratio of borate to metallocene is about 1 to 1 and not 5000 to 1, as in the case of MAO for homogeneous systems. On the other hand, the borate system is highly sensitive to poisons and decomposition and must be stabilized by addition of aluminum alkyls such as triisobutylaluminum (TIBA) the necessary ratio of TIBA to zirconocene is in the range of 100-500. 

The other hydrolysis product of Reaction [1], sodium borate, is water soluble and environmentally innocuous. Borates have not been shown to pose environmental hazards in water supplies. Since Reaction [1] is totally inorganic, it produces no fuel cell poisons... 

Boric acid alone is more rapidly eliminated as the volatile methyl borate, B(OCH3)3, (highly poisonous). If much boric acid is present, two treatments with CH3OH and HC1 may be required. 

If borate is present and fluoride is absent, the former may be removed by repeated evaporation to dryness on a water bath with a mixture of 5 ml methanol (inflammable ) and 10 ml concentrated HC1. The borate slowly volatilizes as methyl borate, (CH3)3B03 (POISONOUS). 

Borate buffers The useful pH range for borate buffers is 8.5-10.0. Boric acid is poisonous in high concentration, and it complexes with vicinal diols like ribose. 

As mentioned earlier in Section IV, Insects, there have been few poisonings from the pesticidal nses of borates. Most poisonings have resulted from injudicious uses in hnman medicine aimed at suppressing bacterial growth, snch as compresses for bnms. Many poisonings of newborns occurred in the 1950s and 1960s. 

In the past, boric acid was falsely considered to be relatively non-toxic, and had an unwarranted reputation as a germicide. However, it is only bacteriostatic, even in a saturated aqueous solution, and can cause adverse reactions. Boric acid has often proved poisonous, either by ingestion or after local use. Cases from the world literature have been reviewed (1,2). In 172 cases of boric acid intoxication, including 83 deaths, 37 deaths occurred after external use, including 23 children with nappy rash. From 1974 to 1984, the Poison Centre in Paris recorded 134 cases of intoxication with boric acid or borates, 88 of which were accidental and 31 iatrogenic. 

The efficient synthesis of a potent topoisomerase I poison terbenzimidazole was developed in the laboratory of P.J. Smith. The desired aryl-aryl bonds were created via iterative Suzuki-cross couplings. The arylboronic ester was derived from 1-benzyl-5-iodo-1/-/-benzimidazole using the Miyaura boration. 

At high rates of 1.2-3.5 tons of B20,/ha, all three borates are used pre-and postemergence as total herbicides for soil sterilisation on non-crop sites. At these rates they are suitable also for the eradication of St. John s wort (Litzenberger et al., 1945) and poison ivy (Stodard, 1944). At lower rates of40-100 kg B20j/ha they can also be used for selective weed control in sugar beet and fodder b t (Crafts and Raynor, 1936 Wang and Klotz, 1938 Crafts et al., 1941). 

Borate and chromate poisoning cause oliguria which is treated with supplementation of N-acetylcysteine (Banner et al. 1986). N-Acetylcysteine also reduces paracetamol (acetaminophen) toxicity (Flanagan and Meredith 1991), by diminishing the analgesic effect (Levy 1986). 

Chromium green, or emerald green, is a green hydrate, formed hy decomposing a double borate of chromium and potassium by HjO. It is used in the arts as a substitute for the arsenical greens, and is non-poisonous. 

Boric acid and sodium borate have been used for many years in a variety of products as antiseptics and fungistatic agents in baby talcum powder. Boric acid powder (99%) is still used as a pesticide against ants and cockroaches. In the past, repeated and indiscriminate application of boric acid to broken or abraded skin resulted in many cases of severe poisoning. Epidemics have also occurred after boric acid was mistakenly added to infant formula or used in food preparation. Although chronic toxicity seldom occurs now, acute ingestion by children at home is common. 

The fast (E > 0.18 MeV) neutron flux exiting the active core is attenuated by the graphite reflectors. The attenuation of the total neutron flux exiting the permanent side reflector is enhanced by inclusion of borated steel pins (a neutron absorber material) in the outer portions of the reflector. The shielding poisons are located as far as practical away from the active core boundary to limit their impact on the core reactivity. 

Sodium borate decahydrate fly poison, flypaper Quassia foam... 

Organophosphorus compounds, when heated to 400°C, form a phosphate residue [109] that is tenaciously held on the carbon surface, acting as a poison, blocking active sites and reducing the rate of oxidation up to working temperatures of 850 900°C. This temperature can be extended when phosphates are used in conjunction with other inhibitors like B2O3, Si02 and SiC. Phosphates are not as effective as borates. 

In the PHWR 220s two systems, i.e. 14 mechanical shut-off rods which fall freely under gravity into the core and 12 liquid poison stand-pipes into which sodium-penta borate solution is introduced, provide fast acting redundant and diverse shut-down systems. These are reinforced by slow-acting automatic liquid poison addition into the moderator system for prolonged shut-downs. 

The basic design feature of SPWR is an integrated PWR with poison tanks filled with highly borated water (boric acid water) in place of control rods for reactor shutdown. 

Two poison tanks which contain highly borated water (12,000 ppm of boron concentration) are installed in the CV for the passive reactor shutdown system (PRSS). Each poison tank (60 m ) is connected to the RPV by two pipes. The upper pipe has two normally closed hydraulic pressure valves. The pressure in the poison tank is maintained to be equal to that of the primary system under normal operation. The borated water in the tank is cooled by the C V water. The inside wall and the nozzle part of the poison tank have liners for mitigating a thermal stress due to temperature change during poison injection. 

Under normal operation, the valve disk is kept in the closed position by the delivery pressure of the MCP against the spring force. The valves open passively due to loss of the delivery pressure of the MCP in case of MCP failure. If the delivery pressure of the MCP is lost, the disk is pushed back to open position by the spring force. Borated water in the poison tanks has enough ability to maintain a cold shutdown condition. 

The time for the borated water in the poison tank to reach the core would be approximately 24 seconds by natural circulation and approximately 8 seconds by forced circulation. Shutdown time is relatively long in the SPWR. However, this is not regarded as an... 

Control Element Absorber (PRSS) X Highly borated water injection passively from poison tank (2 trains, 1 tank and 2 valves/train)... 

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