Phosphoric Acids and Phosphates

Abstract

Most commercial applications of phosphorus‐containing materials are based on phosphoric acids and the phosphates. Uses, other than as fertilizer, include applications in detergency, foods and food processing, dental materials, dentifrices, metal surface treatments, flame retardency, etc. Structures and properties of orthophosphoric acid and condensed phosphoric acids are presented. The manufacture of technical‐ and food‐grade phosphoric acids by thermal and wet acid purification processes, as well as some of the uses of the various phosphoric acids, are discussed. The chemistry and properties of orthophosphates and condensed phosphates are presented. Emphasis is placed on alkali metal and calcium salts and their solution properties. Properties specific to condensed phosphate salts such as hydrolysis and metal ion complexation are outlined. Manufacturing schemes for the phosphates are described and attention is given to the control of product properties.

Determination and Correlation of Vapor–Liquid Equilibria for the Phosphoric Acid + Water + Cyclohexane + Ethanol System

“…Binary System. The vapor pressure data 29 for the phosphoric acid + water system at various temperatures were employed in regressing the electrolyte NRTL parameters, as tabulated in Table 3, for the pairs of H 3 PO 4 −H 2 O and H + [H 2 PO 4 ] − −H 2 O. The comparison between the literature data and correlation is illustrated in Figure 1.…”

“…Boiling point of phosphoric acid aqueous solution at 1 atm: ■, literature; ○, experiment; −, electrolyte NRTL model.…”

Re‐evaluation of aluminium sulphates (E 520–523) and sodium aluminium phosphate (E 541) as food additives

“…The general scheme to manufacture phosphate salts can be summarised as follows (Gard, 2006): orthophosphoric acid (H 3 PO 4 ) is allow to react with the appropriate bases (e.g. sodium hydroxide, aluminium hydroxide, ammonia) until neutralisation is reached, to yield a solution or slurry with an acid/base ratio according to the orthophosphate product desired.…”

“…Aluminium salts (sodium and potassium sulphate) have been evaluated by JECFA in 1978(JECFA, 1978 that concluded that the use of aluminium metal as a silvering decoration for certain items of confectionary was not considered to present a health hazard. SALP (E 541) was evaluated by JECFA in 1982, 1985, 1986, 1988, 2006(JECFA, 1982, 1986, 1987, 1989. In its first evaluation in 1982, a temporary acceptable daily intake (ADI) of 0-6 mg/kg body weight (bw) was allocated due to insufficient data.…”

“…With reference to EC Inventory, the aforesaid EINECS (EC) number pairs with CAS Registry No 7785‐88‐8. For NaAl 3 H 14 (PO 4 ) 8 ∙4H 2 O, Gard () reports CAS Registry No 10305‐76‐7.…”