Effect of phosphoric acid

Platinum has also had its share of attention in recent years. The effect of phosphoric acid concentration on the oxygen evolution reaction kinetics at a platinum electrode using 0-7 m-17-5 m phosphoric acid at 25°C has been studied with a rotating disc electrode . The characteristics of the ORR are very dependent on phosphoric acid concentration and H2O2 is formed as an intermediate reaction. Also, platinum dissolution in concentrated phosphoric acid at 176 and 196°C at potentials up to 0-9 (SHE) has been reported . 

The Effect of Phosphoric Acid as a Casting Dope Ingredient on Reverse-Osmosis Membrane Properties... 

Figure I. Effect of phosphoric acid concentration in additive on the activation energy of viscous flow of casting solutions...

Fig. 4. Effects of phosphoric acid (PA) treatment on the thermo-oxidative stability of PBI and PBI/PEI blend films aged in air at 315 °C...

H3P04.H20 B is the melting point of this hydrate (29-35°) BC, the effect of phosphoric acid on the m.p. of the hemihydrate CD, the solubility curve of 10H3P04.H20 and C is the eutectic point (23-5°) of the two hydrates D is the transition point (26-2°) DE is the solubility curve of orthophosphoric acid and E is the melting point (42-30°) of orthophosphoric acid. W. H. Ross and R. M. Jones observed no break in the curve at D, and were unable to confirm the existence of the hydrate, 10H3P04.H20. J. Kendall and co-workers studied the hydrate formation with this and related acids. 

To study the effect of phosphoric acid on the structure of complex adsorbents XRD measurements were performed. All of the adsorbents were amorphous with one exception (C/GLioo-P4-65). This sample was partially crystalline because there are XRD peaks characteristic for Si5P6025.7... 

Besides ester formation another effect of phosphoric acid is hydrolytic splitting of glycosidic bonds. This effect is more pronounced for celluloses with a higher DP and depends also on the amount of acid used for impregnation and the pretreatment temperature. 

Taircell impregnated with 3.5% acid and without pretreatment gave levoglucosenone yields of up to 17 %. The amount of levoglucosan is the same as for initial cellulose, namely 19 %, which is a proof for a catalytic effect of phosphoric acid on cellulose depolymerisation. Thermocell and Kraft pulp showed an increase in the summary yield of 1,6-anhydrosaccharides after impregnation with of 3.5 % acid... 

Voss [69] has published a comprehensive review of the effects of phosphoric acid on the performance of lead-acid batteries. This review included previously unpublished tests by Kugel, Rabl, and Woost conducted between 1926 and 1935, in which phosphoric acid was added to the positive paste at the 0.9, 2.0,2.9, or 4.0wt.% level, and at 0.9wt.% in the electrolyte. The results showed that, during cycling, the phosphoric acid concentration increases in the electrolyte but decreases in the phosphated positive active-material. It is also higher in the electrolyte when the cell is discharged. Tables 4.8-4.10 show the results of these studies. 

Table 4.10. Effect of phosphoric acid dosage on cycle-life of Ky Faure t5 pe cells...

Many other workers have studied the effects of adding phosphoric acid to the electrolyte. The results vary dramatically with the acid concentration, paste composition, acid paste ratio, and application. Voss recommends that cells should be operated above 15°C to decrease mossing, and summarizes the effects of phosphoric acid in lead-acid cells as follows ... 

Gel batteries are sometimes produced with phosphoric acid added to the electrolyte and sometimes without. Phosphoric acid is not generally used for standby applications it is mainly used for applications, which includes some cycling. Investigations of the effect of phosphoric acid, especially with regard to an improvement in cycle-life, can be found in the literature [64-70]. According to the results of these investigations, there is an adsorption of phosphoric acid on to the lead dioxide surface, which modifies crystal growth. It has also been pointed out that... 

In order to obtain a detailed model of the conductivity for an operating HT-PEFC, the above-described effects of phosphoric acid and water should be combined with the interaction of the membrane material, the dynamic water production at the catalyst sites, and the dynamic water removal due to the gas flow in the channels. A fully featured model with atomistic resolution seems to be impossible at present. Recent modeling approaches can describe the proton conductivity mechanism at a single concentration with atomistic resolution [50, 51]. 

The effect of phosphoric acid on silica has been examined by Mitsyuk (193), who found that HjPO is adsorbed on silica gel from water. The amount corresponds to about one HjPO molecule per surface silicon atom, indicating formation of a surface compound of silicon phosphate. Once treated with as little as 0.06% HjPO, the rate of dissolution of the silica in water is greatly reduced. The addition of H2SO to the dilute H,PO< solution prevents the formation of an adsorbed film and accelerates dissolution. In strong HjPO there is further reaction as silica is converted to SiPjOr in which silicon is coordinated with six oxygen atoms. 

Fig. 20.21 Schematic illustration of the effect of phosphoric acid and heat treatment on SnO -nH O (Adapted with permission from Korosi et al. 2005, Copyright 2005 Elsevier)...

Korosi L, Papp S, Meynen V, Cool P, Vansant EF, Dekany 1 (2005) Preparation euid characterization of SnO nanoparticles of enhanced thermal stability the effect of phosphoric acid treatment on SnO -nH O. Colloid Surf A 268 147-154... 

Zielinski S. The effect of phosphoric acid composition on the growth of gypsum crystals. In iTuiustrialCrystalUzatioTi 81, (eds. Jan5ld, S.J., de Jong, E.J.), p. 329, North-HoUand, Amsterdam 1982... 

Glass JT, Cahen GLJ, Stoner GE. The effect of phosphoric acid concentration on electrocatalysis. J Electrochem Soc 1989 136 656-60. 

Hirata, T. Yamanaka, M. DFT Study of Chiral-Phosphoric-Acid-Catalyzed Enantioselective Friedel-Crafts Reaction of Indole with Nitroalkene Bifunctionality and Substituent Effect of Phosphoric Acid. Chem. Asian J. 2011, 6, 510-516. 

Pandey SN, Nair P. Effect of phosphoric acid treatment on physical and chemical properties of cotton fiber. Text Res J 1974 December 927. 

Ikeda Y, Sakaihori T, Tomishige K, Fujimoto K (2000) Promoting effect of phosphoric acid on zirconia catalysts in selective synthesis of dimethyl carbonate from methanol and carbon dioxide. Catal Lett 66 59-62... 

On the other hand, a study funded by Pepsi suggests that insufficient intake of phosphorus leads to lower bone density. The study does not examine the effect of phosphoric acid, which binds with magnesium and calcium in the digestive tract to form salts that are not absorbed, but rather studies general phosphorus intake. 

Ikeda, Y Sakaihori, X Tomishige, K. Fujimoto, K. Promoting Effect of Phosphoric Acid on Zirconia Catalysts in Selective Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide. Catal. Lett. 2000,66,59-62. 

Zhang J, Zhang B, Zhang J, Lin L, Liu S, Ouyang P (2010) Effect of phosphoric acid pretreatment on enzymatic hydrolysis of microcrystalline cellulose. Btotechnol Adv 28 613-619... 

Desulfonation is the most useful application of a decomposition reaction to analysis of anionics. Desulfonation is generally conducted by reaction with phosphoric acid. While desulfonation and analysis can be conducted within seconds of each other in a pyrolysis gas chromatograph, there are operational difficulties because of the deleterious effect of phosphoric acid on quartz (13). Most investigators opt to perform the reaction and chromatography in separate steps. The reaction is often conducted in a reflux apparatus which permits trapping the resulting hydrocarbons without the need for further cleanup. However, the reaction can be performed in a simple sealed tube (14). The sealed tube is the basis of the international standard method for analysis of LAS (15). The reaction mixture must then be extracted to isolate the alkylbenzenes for GC analysis. 

---