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Boric acid is a weak acid, with pK a (the pH at which buffering is strongest because the free acid and borate ion are in equal concentrations) of 9.24 in pure water at 25 °C. But apparent p K a is substantially lower in swimming pool or ocean waters because of interactions with various other molecules in solution.
Phase behavior Triple point? K (? °C), ? Pa Critical point? K (? °C), ? Pa Std enthalpy change of fusion, Δ fus H o? kJ/mol Std entropy change of fusion, Δ fus S oJ/(mol·K)
Some of the anhydrous borates above can be crystallized from molten mixtured of sodium oxide and boric oxide. [6] Some sodium borates hower cannot be analyzed as combinations xNa 2 O·yB 2 O 3 ·zH 2 O of the three ordinary oxides. The most important example is sodium perborate, originally described as NaBO 3 ·H 2 O but actually (Na +) 2 [B 2 ...
In animals, boric acid/borate salts are essentially completely absorbed following oral ingestion. Absorption occurs via inhalation, although quantitative data are unavailable. Limited data indicate that boric acid/salts are not absorbed through intact skin to any significant extent, although absorption occurs through skin that is severely abraded.
The ion occurs in boric acid solutions at neutral pH, being formed by condensation of orthoborate and tetrahydroxyborate anions: 2 B(OH) 3 + 2 [B(OH) 4] − ⇌ [B 4 O 5 (OH) 4] − 2 + 5 H 2 O. The tetraborate anion includes two tetrahedral and two trigonal boron atoms symmetrically assembled in a fused bicyclic structure.
Borax is also easily converted to boric acid and other borates, which have many applications. Its reaction with hydrochloric acid to form boric acid is: Na 2 B 4 O 7 ·10H 2 O + 2 HCl → 4 H 3 BO 3 + 2 NaCl + 5 H 2 O. Borax is sufficiently stable to find use as a primary standard for acid-base titrimetry. [17]: p.316
Barium borate can be prepared by reaction of an aqueous solution of boric acid with barium hydroxide. The prepared γ-barium borate contains water of crystallization that can not be completely removed by drying at 120 °C. Dehydrated γ-barium borate can be prepared by heating to 300–400 °C.
Concrete cracks due to tensile stress induced by shrinkage or stresses occurring during setting or use. Various means are used to overcome this. Fiber reinforced concrete uses fine fibers distributed throughout the mix or larger metal or other reinforcement elements to limit the size and extent of cracks. In many large structures, joints or ...