Tetraboric acid

Tetra-borsMure, /. tetraboric acid, -bromkoh-ienstoff, m. carbon tetrabromide. -chlor-kohlenstofF, m. carbon tetrachloride, -chlor-zinn, n. tin tetrachloride, -eder, n. tetra hedron. 

Orthoboric acid H3803 or B203.3H20 Metaboric acid HBOz or B2O3.H20 Tetraboric acid H2B407 or 2B203.H20... 

The parent acid, H3B03, functions as a weak acid in aqueous solution, possessing an ionization constant of about 6 x 10-, at 25°C in dilute solution. As its concentration increases, the ionization constant increases markedly. Kolthoff (220) investigated this effect by electrical conductivity and emf measurements, obtaining values of 4.6 x 1010 and 408 x 10 1 for boric acid concentrations of 0.1 M and 0.75 M respectively at 18°C. These results were attributed to the formation of tetraboric acid. 

In this preparation, borax, the sodium salt of tetraboric acid, is chosen as the source of boron. Although boron is decidedly a non-metal, still its acid-forming characteristics are not highly developed and its acids are readily displaced by strong acids from solutions of their salts. Thus tetraboric acid, H2B4O7, would be set free from borax by hydrochloric acid, but the acid which actually crystallizes is the more highly hydrated orthoboric acid, H3BO3. 

Explain the relations between orthoboric acid, metaboric acid, tetraboric acid, and boric anhydride. Experiment Place a few grams of boric acid on a watch glass upon the steam table (100-110°) and leave for hour. What is formed What would be formed if the acid were heated to 140° Suspend a little of the acid in a loop of platinum wire, and heat in the Bunsen flame. What is formed ... 

What effect has a solution of borax upon litmus Explain what is thus shown regarding the strength of boric or tetraboric acid. Explain why litmus will not be turned a bright red until more than 2 moles of HC1 have been added to 1 mole of borax. 

These minerals are salts of the complex acids H0B4O7, tetraboric acid, and hexaboric acid, which, like the acid anhydride boric... 

H0B4O7, tetraboric acid (HBOo)n, metaboric acid (u S) H3SLO7, disilicic acid... 

Melting point 170.9°C. When heated slowly to 181.0°C, boric acid loses water to form metaboric acid (HBO2) at 140°C, tetraboric acid (H2B4O7) is formed and at higher temperatures, boron trioxide (B2O3) is formed. ... 

The diprotic acid H2B4O7 is tetraboric acid. The hydrated sodium salt Na2B407 10 H2O, called borax, occurs in dry lake deposits in California and can also be prepared from other borate minerals. Solutions of borax are alkaline, and the substance is used in various laundry and cleaning products. 

Write a balanced equation for each of the following reactions (a) Diborane reacts with water to form boric acid and molecular hydrogen, (b) Upon heating, boric acid undergoes a condensation reaction to form tetraboric acid, (c) Boron oxide dissolves in water to give a solution of boric acid. 

In this experiment phosphate is determined by singlecolumn, or nonsuppressed, ion chromatography using an anionic column and a conductivity detector. The mobile phase is a mixture of n-butanol, acetonitrile, and water (containing sodium gluconate, boric acid, and sodium tetraborate). 

PORONCOMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vol 4) Disodium tetraborate pentahydrate [12045-88-4]... 

Boron. The principal materials used are borax [1303-96-4] sodium pentaborate, sodium tetraborate, partially dehydrated borates, boric acid [10043-35-3] and boron frits. Soil appHcation rates of boron for vegetable crops and alfalfa are usually in the range of 0.5—3 kg/hm. Lower rates are used for more sensitive crops. Both soil and foHar appHcation are practiced but soil appHcations remain effective longer. Boron toxicity is not often observed in field appHcations (see Boron compounds). 

Nondurable Finishes. Flame-retardant finishes that are not durable to launderiag and bleaching are, ia general, relatively iaexpensive and efficient (23). In some cases, a mixture of two or more salts is more effective than either of the components alone. For example, an add-on of 60% borax (sodium tetraborate) is required to prevent fabric from burning, and boric acid is iaeffective as a flame retardant even at levels equal to the weight of the fabric. However, a mixture of seven parts borax and three parts boric acid imparts flame resistance to a fabric with as Utde as 6.5% add-on. 

Wa.terBa.la.nce Chemicals. Water balance chemicals include muriatic acid, sodium bisulfate, and soda ash for pH control, sodium bicarbonate for alkalinity adjustment, and calcium chloride for hardness adjustment. A recent development is use of buffering agents for pH control. One of these products, sodium tetraborate, hydrolyzes to boric acid and a small amount of orthoborate (50) which provides significantly less buffering than carbonate and cyanurate alkalinity in the recommended pool pH range of 7.2—7.8 even at 100 ppm. 

The commercial ores, beryl and bertrandite, are usually decomposed by fusion using sodium carbonate. The melt is dissolved in a mixture of sulfuric and hydrofluoric acids and the solution is evaporated to strong fumes to drive off siUcon tetrafluoride, diluted, then analy2ed by atomic absorption or plasma emission spectrometry. If sodium or siUcon are also to be determined, the ore may be fused with a mixture of lithium metaborate and lithium tetraborate, and the melt dissolved in nitric and hydrofluoric acids (17). 

Manufacture. Potassium tetraborate tetrahydrate may be prepared from an aqueous solution of KOH and boric acid having a B202 K20 ratio... 

Ammonium tetraborate tetrahydrate is prepared by crystallization from an aqueous solution of boric acid and ammonia having a B202 (NH4)20 ratio of 1.8 2.1. Ammonium pentaborate is similarly produced from an aqueous solution of boric acid and ammonia having a B202 (NH4)20 ratio of 5. Supersaturated solutions are easily formed and the rate of crystallization is proportional to the extent of supersaturation (130). A process for the production... 

Titration of borate ion with a strong acid. The titration of the tetraborate ion with hydrochloric acid is similar to that described above. The net result of the displacement titration is given by ... 

Boric acid behaves as a weak monoprotic acid with a dissociation constant of 6.4 x 10-10. The pH at the equivalence point in the titration of 0.2M sodium tetraborate with 0.2 M hydrochloric acid is that due to 0.1 M boric acid, i.e. 5.6. Further addition of hydrochloric acid will cause a sharp decrease of pH and any indicator covering the pH range 3.7-5.1 (and slightly beyond this) may be used suitable indicators are bromocresol green, methyl orange, bromophenol blue, and methyl red. 

B. Standardisation against sodium tetraborate. The advantages of sodium tetraborate decahydrate (borax) are (i) it has a large relative molecular mass, 381.44 (that of anhydrous sodium carbonate is 106.00) (ii) it is easily and economically purified by recrystallisation (iii) heating to constant weight is not required (iv) it is practically non-hygroscopic and (v) a sharp end point can be obtained with methyl red at room temperatures, since this indicator is not affected by the very weak boric acid. 

Procedure. Weigh out accurately from a weighing bottle 0.4-0.5g of pure sodium tetraborate into a 250 mL conical flask (Note 1), dissolve it in about 50 mL of water and add a few drops of methyl red. Titrate with the hydrochloric acid contained in a burette (for details, see under A) until the colour changes to pink (Note 2). Repeat the titration with two other portions. Calculate the... 

Either the Mohr titration or the adsorption indicator method may be used for the determination of chlorides in neutral solution by titration with standard 0.1M silver nitrate. If the solution is acid, neutralisation may be effected with chloride-free calcium carbonate, sodium tetraborate, or sodium hydrogencarbonate. Mineral acid may also be removed by neutralising most ofthe acid with ammonia solution and then adding an excess of ammonium acetate. Titration of the neutral solution, prepared with calcium carbonate, by the adsorption indicator method is rendered easier by the addition of 5 mL of 2 per cent dextrin solution this offsets the coagulating effect of the calcium ion. If the solution is basic, it may be neutralised with chloride-free nitric acid, using phenolphthalein as indicator. 

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