Phosphoric acid

“ Phosphorus itself is a remarkable substance, much resembling sulphur, but much more inflammable. It has been procured chiefly, till of late, from urine, but now more generally from bones, by means of the vitriolic acid, which unites with the calcareous earth of which bones consist, and sets at liberty the phosphoric acid, or the base of that acid, with which it was naturally combined. The acid thus procured, mixed [Pg 60] with charcoal, and exposed to a strong heat, makes phosphorus. ”

“ There are five combinations, of phosphorus and oxygen:—1. the white oxide; 2. the red oxide; 3. hypophosphorous acid; 4. phosphorous acid; 5. phosphoric acid. The last is the only one of interest in the arts. It may be obtained from the syrupy superphosphate of lime above described, by diluting it with water, saturating with carbonate of ammonia; evaporating, crystallizing, and gently igniting the salt in a retort. The ammonia is volatilized, and may be condensed into water by a Woulfe’s apparatus, while the phosphoric acid remains in the bottom of the retort. ”

“ If the phosphate examined has been heated to redness before solution, it then, as a metaphosphate, gives a white precipitate with nitrate of silver.—5. Hydrochloric acid is added to the solution to acid reaction, and afterwards 1 or 2 drops of a concentrated solution of ferric chloride; a solution of acetate of potassium is next added in excess, when a flocculent, gelatinous, white precipitate will be formed if phosphoric acid or any phosphate was present in any form or combination in the original liquor. ”

“ Syn. Hydrated phosphorous acid. Pure phosphorus is volatilised through a layer of powdered mercuric chloride, contained in a glass tube;1274 terchloride of phosphorus comes over, which, on being mixed with water, is resolved into hydrochloric acid and phosphorous acid; by evaporating the mixed liquid to the consistence of a syrup, the first is expelled, and the residuum forms a crystalline mass of hydrated phosphorous acid on cooling.
Prop., &c. It is a powerful deoxidising agent. Heated in a closed vessel, it is resolved into hydrated phosphoric acid and pure phosphuretted hydrogen gas. ”

“ The functions which phosphoric acid fulfils in plant life would appear to be connected rather with the maturing of the plant than with the actual growth of the structure. Phosphates are found concentrated in those parts of the plant where cell growth and reproduction are most active. More especially is this the case with the seed in which phosphates are present in greatest quantity. While nitrogen delays maturity, phosphoric acid has just the opposite effect, and cereal crops not sufficiently supplied with it ripen much more tardily than do others. ”

“ Solution of Phosphatic Slags.—Sulfuric acid has been found to be an excellent solvent for basic slags preparatory to the determination of phosphoric acid. There is, however, no unanimity of opinion concerning the best method or means of solution. Aqua regia and nitric acid are objected to because they may convert any phosphorus in combination with the iron into phosphoric acid and thus increase the quantity present. ”

“ It is unaffected by light when pure, but if phosphorus be present, even in minute quantity, it turns yellow and ultimately dark red. It oxidizes on exposure to air to the pentoxide, and with a brilliant inflammation when thrown into oxygen at 50°–60°. It slowly reacts with cold water to form phosphorous acid; but with hot water it is energetically decomposed, giving much red phosphorus or the suboxide being formed with an explosive evolution of spontaneously inflammable phosphoretted hydrogen; phosphoric acid is also formed. ”

“ The green of phosphoric, or the phosphates, is much less intense than that of the borates or boracic acid, but yet the reaction is a certain one, and is susceptible of considerable delicacy, either with the forceps, or still better upon platinum wire. Sulphuric acid is a great aid to the development of the color, especially if other salts be present which would be liable to hide the color of the phosphoric acid. ”

“ The Phosphoric acid frequently exists in the urine in a free state, when it would appear to act, like any other acid, as a precipitant of the Lithic acid; this however is not the circumstance that renders its presence formidable; it is to the abundance of its compounds that we are to look for mischief. In healthy urine the phosphoric acid appears to exist in union with soda and ammonia, and partly with lime and magnesia; the latter salts being retained in solution by an excess of acid; but the proportion of these bodies is liable to considerable variation. ”

“ As phosphorus has a sufficient affinity for oxygen to attract it from the nitric and muriatic acids, we may form phosphoric acid, by means of these acids, in a very simple and cheap manner. Fill a tubulated receiver, half full of concentrated nitric acid, and heat it gently, then throw in small pieces of phosphorus through the tube, these are dissolved with effervescence and red fumes of nitrous gas fly off; add phosphorus so long as it will dissolve, and then increase the fire under the retort to drive off the last particles of nitric acid ”

“ Salts are formed when a “basis,” i.e., a metal oxide, replaces water. When potassium-acid sulfate is neutralized by sodium base, the acid-salt divides into Glauber’s salt and potassium sulfate, which proves the acid-salt to be a mixture of the neutral salt with its acid. Sodium-acid phosphate behaves quite differently. After neutralization by a potassium “base” (hydroxide) , the salt does not split up; a uniform sodium-potassium phosphate is obtained. Therefore, phosphoric acid is truly three-basic! ”

“ Nitric acid is easily reduced to nitrogen, whilst phosphoric acid is reduced with very much greater difficulty. All the compounds of phosphorus are less volatile than those of nitrogen. Nitric acid, HNO3, is easily distilled; metaphosphoric acid, HPO3, is generally said to be [157] non-volatile; triethylamine, N (C2H5) 3, boils at 90°, and triethylphosphine, P (C2H5) 3, at 127°.
Phosphorus not only combines easily and directly with oxygen, but also with chlorine, bromine, iodine, sulphur, and with certain metals, and red phosphorus when heated combines with hydrogen also. ”

“ The phosphoric acid is precipitated from the clear liquid which is still ammoniacal with magnesia mixture, using ten cubic centimeters for each 100 milligrams of phosphorus pentoxid present. This is added, drop by drop, and the liquid kept stirred during the addition. Allow it to stand at least two hours, filter, wash with dilute ammonia, dry, and ignite. This last is done at first with a very small flame but is finished with the blast-lamp or in a Rössler furnace. To insure burning to whiteness, nitric acid may be used, but not more than one or two drops. ”

“ It is usually made by treating calcium phosphate with concentrated sulphuric acid. The calcium sulphate produced in the reaction is nearly insoluble, and can be filtered off, leaving the phosphoric acid in solution. Very pure acid is made by oxidizing phosphorus with nitric acid. It forms large colorless crystals which are exceedingly soluble in water. Being a tribasic acid, it forms acid as well as normal salts. Thus the following compounds of sodium are known:
These salts are sometimes called respectively primary, secondary, and tertiary phosphates. ”

“ To produce the phosphoric acid which is supplied in fertilizers, the industry obtains the barren phosphatic rock from Tennessee, Carolinas, Florida, etc., grinds this material and treats it chemically so as to make the phosphoric acid available. ”

“ In addition to free phosphoric acid, iron phosphate is separated, which gradually passes into an insoluble form by the abstraction of water due to the crystallization of the gypsum. The alumina present [Pg 141] in a superphosphate seems to have no direct influence on the process of reversion. Its phosphate salt is not acted on by the acid calcium phosphate. Even when a superphosphate solution is treated with alum no precipitation is produced, except on warming, and this disappears when the mass is again cold. ”

“ Thus, from phosphatides, phosphoric acid is generated, and they could also be called phosphagens. Since 1926, however, the name phosphagens has been reserved for a group of organic substances that release their phosphoric acid very readily. The link between phosphorus and carbon is provided by oxygen in the phosphatides, by nitrogen in the phosphagens. In vertebrates, the basis for the phosphoric acid is creatine, whereas invertebrates have arginine instead.
Creatine Phosphate
Arginine phosphate Nuclein and Nucleic Acids
All parts of an organism are essential for life. ”

“ It was formerly obtained from urine, as that fluid contains some phosphoric salts. It is now prepared from bones. These are burnt to an ash, and diluted sulphuric acid is poured on it; the phosphoric acid it contains is then disengaged, and remains in the fluid. The sulphate of lime is then separated, the fluid boiled to dryness, and the dry mass is mixed with charcoal, and distilled in the open fire.
The phosphoric pencil, for writing on a wall, paper, &c. to be luminous in the dark, is nothing more than a bit of phosphorus put into a quill. ”

“ The compound is dried in a current of hot air, or in any other way that will not discolor it, and it is ground to a fine powder. The intimate union of the phosphoric acid and casein during the gradual concentration of the mixture and during the grinding and drying, removes the hydroscopic property of the phosphoric acid, and produces a dry and stable product, which may be regarded as a hyperphosphate of casein. When it is mixed with water, it swells and dissolves slowly. When this compound is mingled with its equivalent of sodium bicarbonate it yields about 17 per cent of gas. ”

“ As a concrete acid is formed by the combustion of phosphorus, it is probable that very little caloric remains in the acid, and, consequently, that the above experiment gives us very nearly the whole quantity of caloric contained in the oxygen gas. Even if we suppose the phosphoric acid to contain a good deal of caloric, yet, as the phosphorus must have contained nearly an equal quantity before combustion, the error must be very small, as it will only consist of the difference between what was contained in the phosphorus before, and in the phosphoric acid after combustion. ”

“ The quantity of phosphoric acid absorbed by the plant is also less than that of nitrogen; and lastly, the different chemical compounds of phosphoric acid occurring in the soil are not nearly so numerous as those of nitrogen. Phosphoric acid, however, must be regarded as ranking next to nitrogen in its importance as a soil-constituent.
Occurrence of Phosphoric Acid in Nature.
That phosphoric acid is of universal occurrence may be assumed from the fact of the almost universal [Pg 200] occurrence of vegetable life on the earth's surface; for plants are unable to grow without it. ”

“ The solution is filtered off, boiled till free of sulphuretted hydrogen, and ammonium chloride and ammonia added. If phosphoric acid is absent, aluminium, chromium and ferric hydrates are precipitated. If, however, phosphoric acid is present in the original substance, we may here obtain a precipitate of the phosphates of the remaining metals, together with aluminium, chromium and ferric hydrates. In this case, the precipitate is dissolved in as little as possible hydrochloric acid and boiled with ammonium acetate, acetic acid and ferric chloride. ”

“ As the green colour is more or less interfered with by the presence of organic matters, he passes the gas through a solution of nitrate of silver; the resulting precipitate [Pg 270] is then placed in another hydrogen apparatus, as just mentioned, and the colour of the flame of the issuing gas noted. Phosphorus may become decomposed in the body; and as phosphoric acid is taken in most articles of food, the only satisfactory evidence of phosphorus having been taken is to produce it in its free state, or at least to exhibit its luminosity. ”

“ If it is acid, i.e. if it holds much more than 20% of so powerful an acid as silica, then the phosphoric acid has so feeble a hold on the base in the slag that it is immediately re-deoxidized by the carbon of the metal, or even by the iron itself, P2O5 + 5Fe = 2P + 5FeO, and the resultant deoxidized phosphorus immediately recombines with the iron. Now in an acid-lined converter the slag is necessarily acid, because even an initially basic slag would immediately corrode away enough of the acid lining to make itself acid. Hence phosphorus cannot be removed in an acid-lined converter. ”

“ Phosphorous acid, the effects of which have been examined experimentally by Professor Hünefeld of Greifswalde, differs in its operation from phosphoric acid. Twenty-five grains had no effect on a rabbit; but a drachm caused difficult breathing, restlessness, bloody vomiting, slight convulsions, and death in twelve hours; and the stomach was found not much injured. The urine contained phosphoric acid. ”

“ The phosphoric acid may also be estimated by the gravimetric method by dissolving the precipitate again in hydrochloric or nitric acid, evaporating to dryness, and drying for one hour at from 110° to 120°, dissolving again in hydrochloric acid, filtering, and washing the precipitate well. The filtrate, which is now free from silica, can be treated with Joulie’s solution, precipitated with magnesia mixture, the precipitate washed, ignited, and weighed as described. The molybdenum method is preferred in the estimation of citrate-soluble phosphoric acid, especially in slags. ”