Syrupy phosphoric acid

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 ... 

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... 

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. 

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. 

Addition of the appropriate amount of water to anhydrous H3PO4, or crystallization from a concentrated aqueous solution of syrupy phosphoric acid, yields the hemihydrale 2H3PO4.H2O as a congruently melting compound (mp 29.3 "). The crystal structure shows the presence of 2 similar H3P()4 molecules which, together with the H2O molecule, are linked into... 

Preparation. A continuous process is described in Ref 26 for its prepn from nitric acid and acetylene. Other prepns on both lab and industrial scales are by the action on Tetranitro-methane (TeNMe) of K hydroxide in aq glycerol (Ref 16), aq HOCHjSOaNa, or 30% aq H peroxide (Ref 19a) to give the K salt which is treated with sulfuric acid (Ref 16), syrupy phosphoric acid (Ref 20), or best by passing gaseous HC1 thru a suspension of the K salt in anhyd eth (Ref 19a). It has also been prepd by the action of nitric acid on malonamide,... 

The early history of the material is obscure. According to Palmer (1891) it goes back to 1832, but this statement has never been corroborated. Rostaing (1878) patented a series of pyrophosphate cements which could include Zn, Mg, Cd, Ba and Ca. Rollins (1879) described a cement formed from zinc oxide and syrupy phosphoric acid. In the same paper he mentions zinc phosphate cements recently introduced by Fletcher and Weston. Similar information is given in a discussion of the Pennsylvania... 

A year-old bottled sample, containing syrupy phosphoric acid as stabiliser and which already showed signs of tar formation, exploded in storage. The pressure explosion appeared to be due to polymerisation, after occlusion of inhibitor in the tar, in a container in which the stopper had become cemented by polymer [1], A similar pressure explosion occurred when dry redistilled nitrile, stabilised with ethanol [2], polymerised after 13 days [3], The spontaneous and violent decomposition of the nitrile on standing for more than a week is usually preceded by formation of a red polymer [4],... 

Sometimes the hydrocarbon is blue, probably owing to traces of an azulene. The contaminant is easily removed by dissolving the hydrocarbon in an equal volume of hexane or petroleum ether and shaking this solution with an equal volume of 85% syrupy phosphoric acid until the color has been removed. The hydrocarbon is then obtained on evaporation of the solvent it does not need redistillation. 

In a 5-I. flask, provided with a two-hole stopper fitted with a 90-cm. fractionating column uand a dropping funnel, are placed 1500 g. of benzoic acid, 1500 g. of acetic anhydride, and 1 cc. of syrupy phosphoric acid. The mixture is very slowly distilled, at such a rate that the temperature of the vapor at the head of the column does not exceed 120° (Note 1). When 250 cc. of distillate has been collected, 250 g. of acetic anhydride is added, and distillation is continued. This process is again repeated, so that in all 2000 g. of acetic anhydride has been taken. Fractionation is then continued, fractions which distil respectively below 1200, at 120-130°, and at 130-140° being collected. Heating is continued until the temperature of the reaction mixture in the flask reaches 270°. 

Zinc oxide has a wide range of uses apart from its use as an artist s pigment where it provides a more translucent white than flake white or titanium white. It is used in cosmetics, driers, quick-setting cements with syrupy phosphoric acid or zinc chloride in dental cement in the manufacture of opaque glass, enamels, car tyres, white glue, matches, white printing inks and porcelain. The photophysics of zinc oxide has been reviewed.1468 ... 

Phosphoric Add.—The commercial acid (D. 1-5) contains 65% H3P04 syrupy phosphoric acid contains about 90% H3P04. Usual impurities sulphuric acid, iron and arsenic acid. 

Sulphurous Acid.—200 c.c. of the beer, acidified with 5 c.c. of syrupy phosphoric acid, are distilled in a current of carbon dioxide, about 100 c.c. of distillate being collected in 50 c.c. of iodine solution (5 grams of iodine and 7-5 grams of potassium iodide per litre). The iodine solution is afterwards acidified with hydrochloric acid and boiled to expel the excess of iodine, the sulphuric acid formed being then precipitated by means of barium chloride. The presence of more than traces of sulphates indicates the addition of sulphite or sulphurous acid to the beer in such case, the barium sulphate is collected and weighed as usual BaSO X 1-372 = weight of SO per litre of the beer. 

Detection and Determination of Ketones in Presence of Aldehydes.—(A) Qualitative Test. A certain amount of the distilled alcohol is diluted so as to obtain about 50 c.c. of about 50% alcohol and then boiled with 10 c.c. of 10% sodium hydroxide solution in a reflux apparatus for 15 minutes. The liquid is afterwards allowed to cool a little and then distilled, about 30-40 c.c. of distillate being collected. The distillate is diluted to 50 c.c. and boiled with 0-5 c.c. of syrupy phosphoric acid and 0 5 c.c. of colourless aniline in a reflux apparatus for about half an hour. By this treatment the aldehydes in the spirit are destroyed or fixed. After cooling to some extent, the liquid is distilled slowly, two portions of distillate of 5 c.c. each being collected and tested for ketones by one of the two methods given above (see p. 252). If ketones are present in more than mere traces, positive reactions should be given by both portions of the distillate. 

B) Qualitative Determination. Exactly 25 c.c. of the distilled spirit are boiled with about 30 c.c. of water, 0 5 c.c. of syrupy phosphoric acid and 0-5 c.c. of aniline under a reflux condenser for half an hour. After cooling,the bulk of the liquid is distilled and the distillate collected in a 50 c.c. measuring flask and made up to volume with water. The ketones are then determined (see section 2), 20 c.c. or 4 c.c. being used according as the gravimetric or volumetric method is employed. 

Orthophosphoric acid of a high degree of purity may be prepared by crystallizing the acid from concentrated solutions. These solutions are obtained by removing water from ordinary syrupy phosphoric acid at low temperature and pressure. This concentration must be performed with care, since the incomplete removal of water results in the... 

A modificatioa of the phosphorus pentoxide method involves the use of syrupy phosphoric acid.221 This affords the advantage of a homogeneous reaction mixture, but there is no indication that the method is an improvement, since so little experimental work is available. 

Direct sulfonation of toluene with concentrated sulfuric acid gives a mixture of ortho and para sulfonic acids from which about 40% of toluene para sulfonic acid can be isolated as the sodium salt. The free acid is important as a convenient solid acid, useful when a strong acid is needed to catalyse a reaction. Being much more easily handled than oily and corrosive sulfuric acid or syrupy phosphoric acid, it is useful for acetal formation (Chapter 14) and eliminations by the El mechanism on alcohols (Chapter 19). It is usually called tosic add, TsOH, or PTSA (para toluene sulfonic acid). 

Procedure Transfer about 250 mg of sample, accurately weighed, into the reaction flask, D, add 25 mL of 0.1 A hydrochloric acid, insert several boiling chips, and connect the flask to the reflux condenser, F, using syrupy phosphoric acid as a lubricant. 

Place a drop of 05m iron(III) chloride solution and 7 drops of syrupy phosphoric acid (sp. gr. 1-75) on a spot plate containing 1 drop of the test solution and stir well. Add a drop of the pyrrole reagent and stir again. A greenish-blue colouration is obtained. 

Chromates, vanadates, and cerium salts give colour reactions with the reagent and should therefore be absent. Iron salts give a yellow colour with hydrogen peroxide, but this is eliminated by the addition of syrupy phosphoric acid. Fluorides bleach the colour (stable [TiF6]2 ions are formed), and large amounts of nitrates, chlorides, bromides, and acetates as well as coloured ions... 

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