Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 131

_Tests._ The following reactions characterise the ordinary or other phosphates:--1. Chloride of barium produces in aqueous solutions of the neutral and basic phosphates a white precipitate, which is insoluble in either hydrochloric or nitric acid, and with difficulty soluble in a solution of chloride of ammonium.--2. Solution of sulphate of calcium produces in neutral and alkaline solutions of the phosphates a white precipitate, freely soluble in acids, even the acetic.--3. Sulphate of magnesium produces in solutions of the phosphates, to which some chloride of ammonium and free ammonia has been added, a white, crystalline, and quickly subsiding precipitate of the phosphate of ammonium and magnesium, which is insoluble in a solution of either ammonia or chloride of ammonium, but readily soluble in acids, even the acetic.--4. Nitrate of silver, with neutral and basic alkaline phosphates, gives a light yellow precipitate. If the fluid in which the precipitate is suspended contained a basic phosphate, it does not affect test paper; if it contained a neutral phosphate, the reaction will be acid. 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 pota.s.sium 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. This test is highly characteristic, and of general applicability.

_Obs._ The insoluble phosphates must be first treated with diluted hydrochloric or sulphuric acid, and the resulting solution filtered and neutralised with an alkali, before applying the reagents. When the substance under examination consists of a very small quant.i.ty of phosphoric acid or phosphate, with a large quant.i.ty of sesquioxide of iron, it should be fused with some carbonate of sodium, the residuum of the ignition exhausted with water, and the tests applied to the filtered solution. a.r.s.enious acid, if present, should be removed by sulphuretted hydrogen before applying the tests. When phosphate of aluminum, the solution in hydrochloric acid is neutralised with carbonate of sodium; carbonate of barium is next added in excess, followed by the addition of hydrate pota.s.sium, also in excess, after which the whole is boiled. An insoluble phosphate of barium is formed, which may be decomposed by sulphuric acid, as before. See MOLYBDATE OF AMMONIUM.

_Estim._ Pure solutions of phosphoric acid may be tested by the common methods of acidimetry. When in a state of combination, it may be separated and weighed in either of the forms noticed under GUANO.

_Uses, &c._ This acid is the common form, and is the compound alluded to when 'phosphoric acid' is spoken of. It is extensively employed by the bleacher, dyer, calico-printer, and enameller. Unlike sulphuric acid and the other strong acids, it does not coagulate alb.u.men nor injure vegetable fibre, and is not decomposed by contact with organic matter. In combination with alumina and a large boracic acid, it is said to be capable of producing a glaze for earthenware of extreme beauty and durability, and perfectly innocuous. It is also used in medicine.

PHOSPHORIC ACID, DILUTED. (B. Ph.) Put 6 fl. oz. of nitric acid (sp. gr.

142), diluted with 8 oz. of distilled water, into a tubulated retort connected with a Liebig's condenser, and having added 413 gr. of phosphorus, apply a very gentle heat until 5 fl. oz. of liquid have distilled over. Return this to the retort, and renew and continue the distillation until the phosphorus has entirely dissolved.

Transfer the contents of the retort to a porcelain capsule and evaporate the liquid until it is reduced to 4 fl. oz. Transfer to a platinum vessel and evaporate to about 2 fl. oz., and until orange vapours cease to form.

Mix when cool in such an amount of distilled water that the volume shall become one pint. (It contains 10 per cent. by weight of anhydrous acid.

Sp. gr. 108.)--_Dose_, 10 to 30 minims properly diluted.

=PHOSPHORUS, BALDWIN'S.= Recently fused nitrate of calcium. For this purpose it must be broken into fragments whilst still warm, and at once placed in dry and well-stopped phials. After exposure for some time to the direct rays of the sun it emits sufficient light in the dark to render visible the figures on the dial-plate of a watch.

=PHOSPHORUS, BOLOGNIAN.= _Syn._ KERCHER'S PHOSPHORUS, BOLOGNIAN STONE.

This substance was accidentally discovered by a shoemaker of Bologna, and excited much interest about the middle of the 17th century. The following is said to have been the formula employed by the Logani family, who were particularly successful in its preparation, and acquired wealth by its sale to the curious throughout Europe.

_Prep._ Reduce recently calcined native sulphate of barium to powder, make it into a paste with mucilage of gum tragacanth, and roll the ma.s.s into pieces about 1/4 inch thick and 1 to 2 inches long; dry these slowly by a moderate heat, and then expose them to ignition in a wind furnace, by placing them loosely among the charcoal; lastly, allow them to cool slowly, and at once place the pieces in well-stopped phials. Like the preceding substance, it phosph.o.r.esces in the dark after exposure to the sun's rays.

=PHOSPHORUS, CANTON'S.= _Prep._ From calcined oyster sh.e.l.ls, 3 parts; flowers of sulphur, 1 part; placed in alternate layers in a covered crucible, and exposed to a strong heat for about an hour. It is preserved and used like the above.

=PHOSPHORUS, HOMBERG'S.= Recently ignited chloride of calcium.

=PHOSPHORUS BOTTLES.= _Prep._ 1. Phosphorus, 12 gr.; olive oil, 1/2 oz.; mix in an oz. phial, and place the latter, loosely corked, in a basin of hot water; as soon as the phosphorus is melted, remove the phial, cork it securely, and agitate it until nearly cold. On being uncorked it emits sufficient light in the dark to see the time by a watch, and will retain this property for some years if not too frequently employed. These are frequently called 'luminous phials.'

2. (BRIQUETS PHOSPHORIQUES.)--_a._ From phosphorus, 3 parts; white wax, 1 part; cautiously melted together by the heat of hot water; as the mixture begins to cool, the bottles are turned round, so that it may adhere to the sides.

_b._ (Bendix.) Cork (rasped small, and dry) and yellow wax, of each 1 part; phosphorus, 4 parts; petroleum, 8 parts; mixed, by fusion, as the last.

Used as instantaneous-light bottles. A sulphur match rubbed against the composition immediately inflames on exposure to the air. They should be only unstoppered at the instant of introducing the match, and should be handled with caution.

=PHOSPHORUS MATCHES.= See MATCHES, and _above_.

=PHOSPHORUS PASTE.= _Syn._ ANTI-a.r.s.eNICAL RAT-POISON, PHOSPHOR-PASTE.

_Prep._ 1. Phosphorus, 1 oz.; warm water, 1 pint; place them in a bottle, cork it, and agitate them well together, until the phosphorus is reduced to a minute state of division, adding towards the end moist sugar, 1/2 lb.; next add of lard (melted by a gentle heat), 1 lb., and repeat the agitation until the whole is nearly cold; when cold, form it into a stiff dough with oatmeal or barley meal, and make this into small b.a.l.l.s or cakes; lastly, dry these in the air, without artificial heat.

2. (Simon.) Phosphorus, 8 parts; water (lukewarm), 180 parts; mix in a mortar, and add of rye meal, 180 parts; when cold, further add of b.u.t.ter or lard, 180 parts; sugar, 125 parts; and mix the whole thoroughly together. This is the formula authorised by an ordinance of the Prussian Government, dated April 27th, 1843.

_Obs._ Rats, mice, &c., eat the above composition with avidity, after which they soon die. It is said that the best method of using it is to place small pieces of it in and about the holes, with some water in a shallow vessel for them to drink. It has the advantage of retaining its efficacy for many years, and is less dangerous to human beings than compositions containing a.r.s.enic, whilst it is even more effective for the purpose for which it is employed. Some persons recommend the addition of a little oil of rhodium or oil of aniseed. See RATS, &c.

=PHOS'PHURET.= _Syn._ PHOSPHIDE; PHOSPh.o.r.eTUM, PHOSPHIDUM, L. A compound of phosphorus with a metal or other basic radical. See the respective METALS, &c.

=PHOSPHURETTED HY'DROGEN.= _Syn._ PHOSPh.o.r.eTTED HYDROGEN. See HYDROGEN.

=PHOSPHATIC DIATHESIS.= _Syn._ WHITE GRAVEL. A morbid condition of the system, characterised by the deposition in the urine of certain salts of phosphoric acid or phosphates. In this affection the urine, contrary to its normal condition, is always alkaline, and the nature of the phosphatic deposit is influenced by the source of the alkalinity. If, as most frequently happens, this is owing to the presence of carbonate of ammonia (formed by the decomposition of the urea by the bladder mucus), the deposit will be found to consist of the triple phosphate, or phosphate of magnesia and ammonia, almost always a.s.sociated with a small quant.i.ty of amorphous phosphate of lime. Under these circ.u.mstances the urine is pale in colour, and upon standing soon decomposes, in doing which it gives off a strong ammoniacal odour. Phosphatic diathesis is a frequent accompaniment of spinal affections and of chronic inflammation of the mucous lining of the bladder.

In mild attacks the best treatment consists in living rather generously, and in the administration of vegetable tonics combined with proper doses of the mineral acids.

=PHOTOG'RAPHY.= _Syn._ HELIOGRAPHY. The art of producing images on prepared surfaces by means of the actinic or chemical rays of the sun's light. The princ.i.p.al photographic processes now in use are the positive-, negative-, and dry-collodion processes, in each of which a thin film or skin of iodised collodion forms the sensitive surface, a plate of gla.s.s being generally used as the foundation of the film. In a positive picture the 'lights' are silvery white by reflected light, and the 'shades' are produced by a 'backing' of black varnish or velvet, showing through the gla.s.s plate. In a negative picture the 'lights' are of a dirty yellow or brown by reflection, and being formed by opaque deposits, appear dense black by transmitted light. Negatives are used in the various paper-printing processes; they are placed upon prepared paper and exposed to direct light, which darkens those parts of the paper not protected by the opaque 'lights,' and thus produces positive prints with natural lights and shades. In this way the portrait 'cartes de visite' and other paper photographs are formed.

Of late years there have been devised a great variety of new photographic processes, some of which are given below, together with modern formulae for the princ.i.p.al solutions, &c., in general request by the photographer.

The Daguerreotype process, discovered by M. Daguerre in 1839, has been entirely superseded by the easier, healthier, and less expensive collodion processes described further on. It consists in submitting a plate of silver or silvered copper to the vapour of iodine and bromine in the dark.

A sensitive film of iodide and bromide of silver is thus formed on the plate, which is immediately exposed to the image of an object in the camera obscura. The latent image impressed on the plate is brought out or developed by exposing the plate to the action of the vapour of mercury.

It is to be noted that in all English photographic formulae the solid and fluid measures of apothecaries weight are used; but in buying or selling chemical articles, the avoirdupois weight is employed.

_Nitrate of Silver Bath_ (_for Positives_). Recrystallised nitrate of silver, 5 dr., dissolved in 10 oz. of distilled water. Filter the solution until it is quite clear, then add 3 drops of nitric acid and 10 drops of collodion. Shake well together and filter. Blue litmus paper should slightly redden in this bath; should it turn very red, add a little ammonia, or oxide of silver; should it not redden at all, add a little acid carefully drop by drop. It is preferable to have a slight excess of acid.

_Developing Solution_ (_for Positives_). Protosulphate of iron, 2 dr., dissolved in 8 oz. of distilled water; add 2-1/2 dr. of glacial acetic acid, 2-1/2 dr. of alcohol, and 5 minims of nitric acid, filter, and pour into a well-stoppered bottle; do not expose to the air.

_Fixing Solution_ (_for Positives_). 50 gr. of cyanide of pota.s.sium dissolved in 5 oz. of distilled water; that is to say, for every fluid ounce of solution required, mix 10 gr. of cyanide of pota.s.sium in 1 oz. of distilled water. Filter and keep in a well-stoppered bottle, and label "Poison."

_Positive Paper._ Plain paper requires preparing or salting before it is ready for use, or it may be purchased already salted.

Procure some sheets of plain Saxe paper, and immerse them for five minutes (removing air-bubbles) in the following solution:--

Chloride of ammonium 100 gr.

Chloride of barium 100 gr.

Citrate of soda 20 gr.

Water 20 oz.

Hang the sheets up to dry. For portraits and most other uses the paper is alb.u.minised on one side. When photographs are printed to be afterwards coloured, unalb.u.minised paper is used.

_Alb.u.minised Paper._ There are several well-known papers sold; _Rive's_, which is a French paper, has a high glaze and fine surface; the _Saxe_, which is more uniform in its texture, is made in Germany. Another maker is _Towgood_. Positive paper is alb.u.minised by placing it in a mixture composed of white of eggs and salt. To the white of each moderate-sized egg use 15 gr. of common salt reduced to a fine powder; whisk until the alb.u.men is all white froth. Leave this froth in a glazed earthen pan for about 12 hours, by which time most of it has settled into clear alb.u.men; pour the clear portion into a flat porcelain tray. This tray should be somewhat larger than the sheets of paper to be alb.u.minised. Lift the paper up by the ends and lay it carefully on the alb.u.men, keeping the side marked as "inferior" uppermost and dry.

The paper should be slightly damp before it is thus treated, as it then takes the alb.u.men more regularly, and is not so liable to air-bubbles. The paper must be lifted at each end, and should any air-bubbles appear, brush them off with a card or small brush, replacing the paper in the bath. Wherever the alb.u.men does not come into actual contact with the paper, a white mark will appear in the print. Remove the paper from the bath and place it to dry on a cardboard frame, or suspend it at the corners by clips. Paper glazed with pure alb.u.men acquires too brilliant a glaze for portraits; the alb.u.men may be diluted with from a 1/4 to 1/3 its bulk of water. It should be kept in tin or zinc cases.

_Plain Paper._ Alb.u.minised paper may be used as plain paper if, instead of sensitising the glazed side, the plain side is placed in the sensitising solution.

_Nitrate of Silver Bath_ (_for Negatives_). Recrystallised nitrate of silver, 1/2 oz.; distilled water, 7 oz.; collodion, 7 drops. Shake well together until the crystals have dissolved, then filter.

The purity of the negative bath is a matter of great importance, hence the necessity of employing the very best nitrate of silver, and also of excluding all foreign matters of every kind. When the bath gets out of order, it should be diluted with an equal bulk of distilled water, and exposed to the sun for a few days, in a white gla.s.s bottle, then filtered, and sufficient nitrate of silver added to restore the strength to 35 grains an ounce, as indicated by the argentometer.

_The Argentometer._ This instrument is for ascertaining the strength of the nitrate of silver solution, which becomes weakened to a certain extent, after the immersion of every plate.

_Developing Solution_ (_for Negatives_). Protosulphate of iron, 75 gr.; glacial acetic acid, 2 dr.; alcohol, 2 dr.; distilled water, 5 oz.

Dissolve the crystals in the water, then add the acid and alcohol, and filter. In hot weather a little more acetic acid may be added, and if it does not flow readily, the alcohol may be increased.

_Intensifying Solution_, No. 1 (_Negatives_). Pyrogallic acid, 10 gr.; citric acid, 10 gr.; distilled water, 5 oz. When it becomes brown it is useless. No. 2. Recrystallised nitrate of silver, 40 gr.; distilled water, 1 oz.; dissolve and filter. This latter will keep for any length of time in the dark.

_Another Intensifying Bath_ (_Negatives_). A saturated solution of b.i.+.c.hloride of mercury in water. Place the negative plate in a bath of the solution, remove when the film a.s.sumes a milky-white appearance, wash, and then plunge into a solution of 1 oz. of liquid ammonia to 10 oz. of water.

Remove the plate, wash, and place to dry. This mode of intensifying may be regulated by leaving the plate in the b.i.+.c.hloride of mercury a shorter time, when it will require a weaker ammonia bath than that above given.

_Fixing Solution_ (_for Negatives_). Hyposulphite of soda, 5 oz.; distilled water, 5 oz.; dissolve and filter.