Acid, phosphoric

Write the formulas of the following phosphoric acids metaphos-phoric, pyrophosphoric, and orthophosphoric. Acquaint yourself with their appearance. 

Metaphosphoric Acid. Reactions jor Determining Metaphosphoric Acid and Its Salts. 1. Pour about 1 ml of an aqueous protein solution into a test tube and add to it approximately the same amount of a sodium metaphosphate solution acidified with acetic acid. What do you observe See whether the protein solution is affected in the same way by sodium metaphosphate and acetic acid solutions taken separately. 

Pour a few drops of silver nitrate into a sodium metaphosphate solution. Note the colour of the precipitate. See how it reacts with dilute nitric acid. Write the equations of the reactions. In what medium can silver metaphosphate be precipitated  

Preparation oj Metaphosphoric Acid. 1. Dissolve 0.1 g of phosphoric anhydride in water and test the solution with an aqueous protein solution. What do you observe  

Put 1-2 ml of a 95% orthophosphoric acid solution into a porcelain bowl. Heat it on a sand bath until it acquires a syrupy consistence, after which roast it at 350 °C. How can you prove that me-taphosphoric acid has been obtained Write the equation of the reaction. 

The Brensted acids so far studied are weak acids. In contrast, stronger chiral Bronsted acid catalysts have emerged recently. Phosphoric acid (41a) had been already employed as a chiral resolving agent [153], and its lanthanide salt was used as a chiral catalyst [154], but (41a) itself had not been employed as a chiral catalyst for the C-C bond forming reactions. 

A biomimetic transfer hydrogenation [168] approach, which employs a Hantzsch ester (44a) as an nicotinamide adenine dinucleotide plus hydrogen (NADH) model [169] thus has been independently reported by Rueping, List, and MacMillan. 

This acid, like the preceding, is a powerful deoxidising agent. When heated in close vessels, the anhydrous acid, obtained by the combustion of phosphorus in rarefied air, yields phosphorus, and anhydrous phosphoric acid, -i-P. The 

With bases phosphorous acid forms salts, which are called phosphites and the general formula of the neutral phosphites fsP,03,3M0,orP,0 M,. 

This compound is formed only when phosphorus is burned in dry air or oxygen gas. It then appears as a white solid, like snow, which rapidly attracts moisture from the air, and passes into metaphosphoric acid, P, O, HO, or P, 0, H and this, again, soon changes, in contact with water, especially if heated, into common or hydrated phosphoric acid, P,jO, 3HO, or P, Oj, H3. The anhydrous phosphoric acid, hke the anhydrous sulphuric acid, can hardly be said to be an acid body, as it does not exhibit acid properties until it has been brought into contact with water.,  

There are three different acids to which this name may be given. If we view them as compounds containing water, then they all contain anhydrous phosphoric acid, combined in each with a different proportion of water, and their formulae will bePjO, HO P,Oj,2HO and P,05,3H0. If, on the other hand, we view them as hydrogen acids, then they contain no anhydrous phosphoric acid, but axe quite distinct compounds, and their formulae will be as follows—P,0 , H P,0  

This acid is easily obtained by dissolving phosphoras in diluted nitric acid wiUi the aid of heat, evaporating to a syrup, and exposing the residue to a red-heat in a platinum crucible. Or the solution of the anhydrous acid may be treated in the same manner or phosphate of ammonia may be ignited in a j platinum crucible. IVhen phosphoric acid has once come in contact with water, it can never be rendered anhydrous by heat it can only be reduced to the state of monobasic acid. 

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Lecithins are fatty acid esters of glycero-phosphoric acid derivatives. Commercially glycerophosphoric acid is used to prepare the medicinal glycerophosphate salts, c.g. the calcium salt. 

Phosphorous acid, H3PO3, HP(0)(0H)2-A dibasic acid (PCI3 plus cold water), strong reducing agent. 

The hydrophilic parts can contain oxygenated groups (glycol ether types) or amines. The first detergents used amine and phosphoric acid salts or... 

More recently, alternative chemistries have been employed to coat oxide surfaces with SAMs. These have included carboxylic 1129, 1301, hydroxamic 11311, phosphonic 1124, 1321 and phosphoric acids 11331. Potential applications of SAMs on oxide surfaces range from protective coatings and adhesive layers to biosensors. 

Phosphorus(III) oxide dissolves slowly in cold water to yield phosphoric(III) acid, H3PO3 (phosphorous acid) ... 

Phosphonic acid, H3PO3, often called just phosphorous acid , is prepared by the hydrolysis of phosphorus trichloride a stream of air containing phosphorus trichloride vapour is passed into ice-cold water, and crystals of the solid acid separate ... 

The important phosphoric acids and their relation to the anhydride P4O10 are ... 

Tetraoxophosphoric acid is a colourless solid, very soluble in water an 85% solution is often used ("syrupy phosphoric acid ). It is tribasic. giving the ions ... 

Two examples of condensed phosphoricfV) acids are heptaoxo-diphosphoric(V) (pyrophosphoric) and polytrioxophosphoric (meta-phosphoric) acids. 

It is however more complicated, esters of phosphorous acid being also formed (c/. p. 308). Iodides are usually prepared by a modification of this method, the ethanol being mixed with red phosphorus, and iodine added. The phosphorus iodide is thus formed in situ, and at once reacts with ethanol to give the corres ponding iodide. 

This is a modification of Method 5, iodine being added to a mixture of red phosphorus and ethanol phosphorus tri- iodide is thus formed m situ, and readily reacts with the ethanol, giving ethyl iodide and phosphorous acid (p. 96). 

The crude acetonitrile contains as impurity chiefly acetic acid, arising from the action of phosphoric acid on the acetamide. Therefore add to the nitrile about half its volume of water, and then add powdered dry potassium carbonate until the well-shaken mixture is saturated. The potassium carbonate neutralises any acetic acid present, and at the same time salts out the otherwise water-soluble nitrile as a separate upper layer. Allow to stand for 20 minutes with further occasional shaking. Now decant the mixed liquids into a separating-funnel, run off the lower carbonate layer as completely as possible, and then pour off the acetonitrile into a 25 ml, distilling-flask into which about 3-4 g. of phosphorus pentoxide have been placed immediately before. Fit a thermometer and water-condenser to the flask and distil the acetonitrile slowly, collecting the fraction of b.p. 79-82°. Yield 9 5 g. (12 ml.). 

A satisfactory bath suitable for temperatures up to about 250° may be prepared by mixing four parts by weight of 85 per cent, ortho-phosphoric acid and one part by weight of meta-phosphoric acid the mixed components should first be heated slowly to 260° and held at this temperature imtil evolution of steam and vapours has ceased. This bath is liquid at room temperatures. For temperatures up to 340°, a mixture of two parts of 85 per cent, ortho-phosphoric acid and one part of meta-phosphoric acid may be used this is solid (or very viscous) at about 20°. 

Phosphoric acid. The commercial syrupy orthophosphoric acid has a sp. gr. of 1-75 and contains about 88 per cent, of H3PO4. An approximately 100 per cent, acid is also marketed. 

The alicyclic secondary alcohol, cycZohexanol, may be dehydrated by concentrated sulphuric acid or by 85 per cent, phosphoric acid to cyciohexene. It has a higher boiling point (82-83°) than amylene and therefore possesses some advantage over the latter in.the study of the reactions of unsaturated hydrocarbons. 

Phosphoric acid method. The advantages of phosphoric acid as a dehydrating agent in this preparation are the absence of carbonisation and the freedom of the product from sulphur dioxide. 

The phosphoric acid may be recovered by diluting the residue in the three-necked flask with water, filtering, and then evaporating with a little nitric acid to a concentration of about 85 per cent. 

Pinacol upon dehydration with acid catalysts e.g., by distillation from 6A sulphuric acid or upon refluxing for 3—4 hours with 50 per cent, phosphoric acid or hydrated oxalic acid) is transformed into methyl ter<.-butyr ketone or plnacolone ... 

The functions of the potassium carbonate are (a) to neutralise the acetic acid arising from the action of the phosphoric acid upon the acetamide, and (6) to salt out the otherwise soluble methyl cyanide as an upper layer. 

B3 the slow distillation of an aromatic carboxylic acid and acetic anhydride in the presence of a little phosphoric acid ... 

Place 150 g. of benzoic acid, 150 g. (139 ml.) of acetic anhydride and 0-2 ml. of syrupy phosphoric acid in a 500 ml. bolt-head flask. Fit the latter with a two-holed stopper carrying a dropping funnel and an efficient fractionating column (compare Fig. 7/7, 61, 1) it is advisable to lag the latter with asbestos cloth. Set up the flask in an oil bath or in a fusible metal bath. Distil the mixture very slowly and at such a rate that the temperature of the vapour at the head of the column does... 

Study of the solubility behaviour of the compound. A semi-quantitative study of the solubility of the substance in a hmited number of solvents (water, ether, dilute sodium hydroxide solution, dilute hydrochloric acid, sodium bicarbonate solution, concentrated sulphuric and phosphoric acid) will, if intelligently apphed, provide valuable information as to the presence or absence of certain classes of organic compounds. 

Compounds which dissolve in concentrated sulphuric acid may be further subdivided into those which are soluble in syrupy phosphoric acid (A) and those which are insoluble in this solvent (B) in general, dissolution takes place without the production of appreciable heat or colour. Those in class A include alcohols, esters, aldehydes, methyl ketones and cyclic ketones provided that they contain less than nine carbon atoms. The solubility limit is somewhat lower than this for ethers thus re-propyl ether dissolves in 85 per cent, phosphoric acid but re-butyl ether and anisole do not. Ethyl benzoate and ethyl malonate are insoluble. 

This group may be further subdivided into Group VA—soluble in concentrated sulphimic acid and soluble in 85 per cent, phosphoric acid— and Group VB—soluble in concentrated sulphuric acid and insoluble in 85 per cent, phosphoric acid. 

Alcohols, esters (but not ethyl benzoate, ethyl malonate or ethyl oxalate), aldehydes, methyl ketones and cyclic ketones containing less than nine carbon atoms as well as ethers containing less than seven carbon atoms are soluble in 85 p>er cent, phosphoric acid. 

Solubility in syrupy phosphoric acid. This test should only be apphed if the compound is soluble in concentrated sulphuric acid. Place 3 0 ml. of 85 per cent, orthophosphoric acid in a dry test-tube and add 0 10 g. of a solid or 0 - 20 ml. of a Liquid. If the compound does not dissolve immediately, agitate for some time but do not boil. 

The essential basis of the scheme for the separation of water-soluble compounds is, therefore, distillation of (a) an aqueous solution of the mixture, (b) an alkaline (with sodium hydroxide) solution of the mixture, and (c) an acidic (with sulphuric oj phosphoric acid) solution of the mixture. The residue will contain the non-volatile components, which must be separated from inorganic salts and from each other by any suitable process. 

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