Chapter LII: Part 2 (13)

As the pressure of oxygen in the surrounding air depends on two factors, the percentage proportion and the barometric pressure, the barometric pressure may be reduced to 6 centimètres for sparrows, if the proportion of oxygen in the air is increased; and it may be raised to 23 atmospheres without causing death, if the proportion of oxygen is reduced by mixing the air with nitrogen. Aeronauts might, therefore, ascend higher than it has hitherto been possible to do by taking with them a bag of oxygen to inhale; and the danger that threatens divers of being poisoned by the oxygen in the compressed air might be averted by using a mixture of air and nitrogen.

From an examination of the gases in the blood of animals confined in rarefied air the author finds that both the oxygen and the carbonic anhydride in the blood diminish. The dyspnœa which is felt in ascending mountains is therefore due to want of oxygen in the blood. The diminution in oxygen becomes diminished at 20 centimètres pressure, yet this is the pressure under which the inhabitants of the elevated Mexican plateau of Anahuac live. The oxygen diminishes more quickly and more regularly than the carbonic anhydride. Although there are but very small quantities of gases simply dissolved in the blood, the chemical combinations in which they take part are dissociated very easily and in a progressive manner under the influence of diminished pressure, and this dissociation takes place more easily in the organisms than in experiments in vacuo.

=PRINCE’S METAL.= One of the names for Dutch gold. (See GOLD, DUTCH.)

=PRINT′ING (Anastatic).= A method of zincography, patented in 1845, having for its object the reproduction of drawings, engravings, and letter-press, from copies however old. To describe briefly the preparation of a plate or cylinder, let us suppose a newspaper about to be reprinted by this means. The sheet is first moistened with dilute acid and placed between sheets of blotting paper, in order that the superfluous moisture may be absorbed. The ink resists the acid, which attacks the blanks only. In all cases where the letter-press is of recent date, or not perhaps older than half a year, a few minutes suffice for this purpose. The paper is then carefully placed upon the plate with which the letter-press to be transferred is in immediate contact, and the whole passed under a press, on removal from which, and on carefully disengaging the paper, the letters are found in reverse on the plate. A preparation of gum is then applied to the plate by means of a roller, after which the letters receive an addition of ink, which is immediately incorporated with that by which they are already formed. These operations are effected in a few minutes. The surface of the plate round the letters is next bitten in a very slight degree by dilute acid, and on the fresh application of the ink it is rejected by the zinc, and received only by the letters, which are charged with the ink by the common roller used in hand-printing. Each letter comes from the press as clear as if it had been imprinted by type metal; and the copies are fac-similes, which cannot easily be distinguished from the original sheet.

When pen-and-ink drawings are to be reproduced, they are made on any paper free from hairs or filaments, and well-sized. The ink used is a preparation made for the purpose, closely resembling lithographic ink, and may be mixed to any degree of thickness in pure distilled water. It should be used fresh, and slightly warm when a fine effect is to be given. In making or copying a design a pencil may be used; but the marks must be left on the paper, and by no means rubbed with india rubber or bread. It is necessary to add that the paper should be kept quite clean and free from friction, and should not be touched by the fingers, inasmuch as it will retain marks of very slight touches.

Before closing this notice of anastatic printing it may be proper to remark, that the great pretensions originally set up by the patentees have not been fulfilled by its extensive adoption in trade.

=PRINTING (Letterpress).=[123] _Syn._ TYPOGRAPHY. The art of collecting together and arranging movable types for the purpose of printing, in one or more colours, by pressure applied from a flat surface or by means of a cylinder biting the paper to be printed, and which is inserted between itself and the type.

[Footnote 123: The Editor is much indebted to Mr J. E. Adlard for this interesting article.]

In illustration of this section, some specimen types are appended, the greater portion being from the well-known foundry of Messrs V. & J. Figgins, and should now be carefully read down to render the further remarks intelligible. The key is contained in itself by reading the column as one continuous paragraph with the help of the foot-notes. Some idea may thus be formed of the vast number of distinct kinds of type necessary to carry out the requirements of the present system of printing.

Mention there has been made that the name of the body is determined by its number of lines to a foot; but this must be qualified. The Imperial foot, or inch, or yard, is an arbitrary measure of length in reality as well as in name. When one foundry was sufficient to supply all the types that were required for use in the early ages of printing, then a name and its dimensions could be taken as absolute. But with the increase of printing, type-founders also increased; and this has produced the variations of bodies which are so annoying to the typographer, for one single letter or space taken from a body larger than its own, yet of the same name, will be enough to throw the column of type out of a straight line all the way through. Still, when we look to the fact that, according to the ancient masters, the large-sized type called _Pica_ (No. 3 and Nos. 18, 19,20 & 21) requires 72-1/2 lines to the foot, and that _Nonpareil_, half its size (No. 9, and Nos. 26, 27, 28 & 29), requires 145 lines to the foot, and recollecting that the slightest variation multiplied 145 times must produce a very sensible deviation, the wonder is that each of the founders should approach each other so closely as they do. An attempt was made some years ago to introduce a certain fixity of standard for each body throughout the trade, based on the French system; the difficulties of altering the standards and matrices of each foundry were seen to be so great that the effort was unavailing.

BODY. BOOKWORK FACE. DISPLAY FACE.
1 Great Primer—— Roman 14 Gt Primer Manuscript
15 Gt Primer Ext. Ornamented
16 Gt Primer Black
2 English—— Roman 17 Gt Primer Condensed Black
3 Pica—— Roman 18 Pica Antique
19 Pica Clarendon
20 Pica Rustic
4 Small Pica—— Roman 21 Pica Narrow Gauge
5 Long Primer—— Roman 22 Long Primer [Condensed
6 Bourgeois—— Roman [Sansserif
7 Brevier—— Roman 23 Brevier Grotesque
24 Brevier Extended
8 Minion——Rom. & Italic 25 Brevier Open Sansserif
9 Nonpareil—— Roman 26 Nonpareil Egyptian
27 Nonpareil Hair line
28 Nonpareil Ornamented
29 Nonpareil Condensed Grotesque
10 Ruby—— Roman
11 Pearl—— Roman 30 Pearl Clarendon
12 Diamond—— Roman 31 Diamond Grotesque
13 Small Pica 2-line (No. 4 doubled) German Text

During the latter half of the present century there has been a growing disposition to return to the cut of the letters as used by the early printers. To meet this desire, nearly all the type-founders have introduced Old-style faces, but yet modernised as to their peculiarities. Considering that this article would not be complete without some such notice thereof, as well as to show the contrast, the following is here introduced to the reader.

These old-faced types cut by the celebrated William Caslon, in or about the years 1716-30, are even now viewed with great satisfaction, and held in high esteem, by judges of the typographic art as master-pieces of shape and finish.

To the list of types presented, and which give a sufficient general view, may be added _Emerald_——between _Minion_ and _Nonpareil_——for book-work, and also for borders and flowers to be used in neat and artistic work; Gem and _Semi-Nonpareil_ for music; and _Minikin_, for music and Oriental work.

The larger sizes of type are, with very few exceptions, simple multiples of the Pica; for instance, 6-_line Roman_ means a roman letter of the depth of six lines of Pica; 20-_line Antique_, an antique of the depth of twenty lines; and so on.

Very little more need be said on the names applied to the different faces. Letters used in Title-pages are especially cut for and styled _Titling——Square, Condensed_, and if very much condensed in width, _Compressed_ or _Narrow-Gauge_. On the other hand, when the letters seem pulled out right and left, they are styled _Extended_.

If the reader will notice the type in which this volume is composed, he will observe that the bottoms of the _tail letters_ are very close down upon the tops of the tall letters, and all but touch: this is termed _solid_. When a page or book is required to look light and less wearisome to the vision, the lines of type are removed from each other, and a space-line inserted between them——the page is now termed _leaded_. These space-lines used to be cut, by the compositor, from milled lead, first in strips of the necessary width, then of the required length; hence the term _leads_, by which name they are commonly known. However, they were but poor appliances at the best. Moulds are now used for casting the metal to the specified thickness in strips of about 9 inches long, then cut by a machine to a set gauge; by these means the thickness of the space-lines, or leads is not only more uniformly secured, but far greater regularity obtained in the lengths cut. Here, as in the large type, as above mentioned, Pica is the standard which regulates the lead; in other words, leads are cast as 3 to a pica, that is, 3 leads form the solid measurement of the Pica body; 4-to-pica requires 4 leads, and the body of the lead continues to decrease according to the prefixed figure, which simply denotes into how many parts the pica is to be divided. Leads are cast so delicately fine that 16 form the pica, but they are seldom used. In many of the News offices brass space-lines have superseded those cast from type-metal.

The method of manufacturing type is——

The face having been determined upon——light or heavy, round or narrow, as well as the thickness of the downstroke——a piece of prepared soft iron is taken, and upon the tip-end thereof the proposed letter is cut in relief; when this cutting is finished it is case-hardened, and afterwards styled the punch. The strike is the next operation. The punch (the letter cut upon which, by-the-bye, is backward) is now punched, or struck, into an oblong piece of copper, about 3 inches long and 1/3rd of an inch thick, the breadth such as the size of the letter may require: this is the matrix. A most particular part has now to be performed, called justifying; which means that the matrices shall, when placed in the mould, deliver the letters perfectly upright, and all to be true on a line as fine as a razor’s edge. When the process of justifying is accomplished, the matrix is fixed at the bottom of a mould, of the shape of a parallelogram, of the size of the body one way, of the width of the letter the other, and the depth the standard height of the type; the molten metal is forced down this tube, either by hand or by a pump worked by hand or steam, the metal filling the matrix (the sunk letter upon which is now forward) receives the shape of the letter, which is once more reversed, or in a backward position, like as the original punch was cut. The castings are released from the mould by a very ingenious method of opening from the two diagonal corners. The types as cast are forwarded on to the dressers to remove burrs and other superfluities; then are placed in long lines in a frame for finishing; next turned face downwards, and a grooving plane driven across the feet to insure correctness in height; finally looked over for blemishes, when all faulty letters are thrown out; the process is completed by ranging into lines of handy length, and tied up——ready for delivery to the typographer.

=PRINT′ING INK.= _Prep._——_a._ The VARNISH. Linseed or nut oil, 10 or 20 galls., is set over the fire in an iron pot capable of containing fully as much more; when it boils, it is kept stirred with an iron ladle, and, if it does not take fire of itself soon after the smoke begins to rise, it is kindled by means of a piece of burning paper, stuck in the cleft end of a long stick; the pot is shortly afterwards removed from the fire, and the oil is suffered to burn for about half an hour, or until a sample of the varnish cooled upon a palette knife may be drawn into strings of about 1/2 inch long, between the fingers; the flame is now extinguished by the application of a closely fitting tin cover, and, as soon as the froth of the ebullition has subsided, black resin is added, in the proportion of 3/4 lb. to 1 lb. for every quart of oil thus treated; the mixture is next stirred until the resin is dissolved, when dry brown soap, cut into slices, 1-3/4 lbs., is further added (cautiously), and the ingredients are again stirred with the spatula until the whole is united, the pot being once more placed over the fire to promote the combination; when this is effected, the varnish is removed from the heat, and, after a good stirring, is covered over and set aside.

_b._ The INK. Indigo and Prussian blue, of each, in fine powder, 2-1/2 oz.; mineral lampblack (finest), 4 lbs.; vegetable lampblack, 3-1/2 lbs.; stir them gradually into the warm varnish (_a_), and submit the mixture to careful grinding, either in a mill or by means of a slab and muller. On the large scale, steam power is now generally employed for this purpose.

An extemporaneous superfine black ink may be made by the following formula:——Take of balsam of copaiba (pure), 9 oz.; lampblack, 3 oz.; indigo and Prussian blue, of each 1/2 oz.; Indian red, 3/4 oz.; yellow soap (dry), 3 oz.; grind the mixture to an impalpable smoothness by means of a stone and muller. Canada balsam may be substituted for balsam of copaiba where the smell of the latter is objectionable, but the ink then dries very quickly.

COLOURED PRINTING INKS are made in a similar way from the following pigments:——Carmine, lakes, vermilion, chrome yellow, red lead, orange red, Indian red, Venetian red, for red; orange chrome, chrome yellow, burnt terra di sienna, gall-stone, Roman ochre, yellow ochre, for orange and yellow; verdigris, Scheele’s green, Schweinfurt green, blues, and yellows mixed, for greens; indigo, Prussian blue, Antwerp b., cobalt b., charcoal b., for blue; lustre, bronze powders, &c., for metallic colours; and umbia, sepia, &c., for brown.

_Obs._ It is necessary to prepare two kinds of varnish, varying in consistence, from more or less boiling, to be occasionally mixed together as circumstances may require; that which answers well in hot weather being too thick in cold, and _vice versâ_. Large characters also require a thinner ink than small ones. Old linseed oil is preferable to new. Yellow resin soap is preferred for black and dark-coloured inks, and white curd soap for light ones.

A good varnish may be drawn into threads like glue, and is very thick and tenacious. The oil loses from 10% to 14% by the boiling. Mr Savage obtained the large medal of the Society of Arts for his black ink made as above.

A PRINTER’S INK EASILY REMOVED FROM WASTE PAPER. The following process for the preparation of a printer’s ink that can be far more readily removed from waste paper than ordinary printer’s ink has been patented by Kirscher and Ebner. Iron is dissolved in some acid——sulphuric, hydrochloric, acetic, &c., will answer, and half of the solution is oxidised with nitric acid and added to the other half and the oxide precipitated from the mixture by means of soda or potash. The precipitate is thoroughly washed, and treated with equal parts of solutions of tannic and gallic acids, and the bluish black, or pure black pigment formed, is thoroughly washed and dried, and mixed with linseed-oil varnish, and can then be immediately used for printing from type, copper, wood, steel, or stone. Waste paper printed with it can be bleached by digesting it for 24 hours in a lukewarm bath of pure water, and 10 per cent. of caustic potash or soda, and then grinding it well in the rag engine, and throwing the pulp upon cloth and allowing it to drain. It is then to be washed with pure water, containing 10 per cent. of hydrochloric, acetic, or oxalic acids, or of binoxalate of potassa, and allowed to digest for 24 hours, and may then be worked up into paper, or it can be dried and used as a substitute in the manufacture of finer paper.

=PRINTS (Ackerman’s Liquor for).= _Prep._ Take of the finest pale glue and white curd soap, of each 4 oz.; boiling water, 3 pints; dissolve, then add of powdered alum, 2 oz. Used to size prints and pictures before colouring them.

=PRINTS, To Bleach.= Simple immersion of the prints in a solution of hypochlorous acid (the article remaining in the solution for a longer or shorter space, according to the strength of the solution) is generally all that is required to whiten it.

=PRIVIES.= See WATER-CLOSETS.

=PROOF.= See ACETIMETRY, ALCOHOLOMETRY, &c.

=PROOFS (Correcting).= The specimen below, with the notes, will, if carefully perused, put the reader into possession of all the secrets of this useful art.

[_The same corrected._]

As the _vine_, which has long twined its graceful foliage about the oak, and been lifted by it into sunshine, will, when the hardy plant is rifted by the thunderbolt, cling round it with its caressing tendrils, and bind up its shattered boughs so is it beautifully ordered by Providence, that WOMAN, who is the mere dependant and ornament of man in his happier hours, should be his stay and solace when smitten by sudden calamity; winding herself into the rugged recesses of his nature, tenderly supporting the drooping head, and binding up the broken heart.

It also is interesting to notice how _some_ minds seem almost to create THEMSELVES, springing up under every disadvantage, and working their “solitary, but irresistible way,” through a thousand obstacles. Nature seems, &c.

IRVING.

_Explanation of the marks_:

1. When a letter or word is to be in _italics_.

2. When a letter is turned upside down.

3. The substitution of a comma for another point or letter.

4. The insertion of a hyphen; also marked (-).

5. When letters should be close together.

6. When a letter or word is to be omitted.

7. When a word is to be changed to roman.

8, 9. Two methods of marking a transposition: when there are _several_ words to be transposed, and they are much intermixed, it is a common plan to number them, and to put the usual mark in the margin.

10. Substitution of a capital for a small letter.

11. When a word is to be changed from small letters to capitals.

12. The transposition of letters in a word.

13. The substitution of one word for another.

14. When a word or letter is to be inserted.

15. When a paragraph occurs improperly.

16. The insertion of a semicolon.

17. When a space or quadrat stands up, and is seen along with the type.

18. When letters of a wrong fount are used.

19. When words crossed off are to remain.

20. The mark for a paragraph, when its commencement has been neglected. Sometimes the sign [, or ¶, or the word ‘_break_,’ is used instead of the syllables ‘_New Par_,’

21. For the insertion of a space when omitted or insufficient.

22. To change capitals to small letters.

23. To change small letters to small capitals.

24. When lines or words are not straight.

25, 26. The insertion of inverted commas. The apostrophe is similarly marked.

27. The insertion of a period when omitted, or in place of another point or letter.

28. Substitution of one letter for another.

29. The method of marking an omission or insertion when too long for the side margin.

=PROPYLA′MINE.= _Syn._ TRITYLAMINE.

C_{3}H_{9}N, or C_{3}H_{7} }
H } N.
H }

This compound or substituted ammonia, in which one of the three atoms of hydrogen is displaced by the radicle propyl or trityl (C_{3}H_{7}), is isomorphous with trimethylamine, which has been often mistaken for it.

Proposed as a remedy for acute and chronic rheumatism.

Hence it is that the commercial substance known under the name of ‘propylamine,’ which has been proposed and employed as a remedy for rheumatism, has been shown to be not propylamine, but its isomer, trimethylamine, or a mixture of this latter, in varying proportions, with ammonia.

Mendius gives the following process for the preparation of propylamine:——36 grams of cyanide of ethyl, 500 grams of common alcohol, 200 grams of water, and 50 grams of 20 per cent. hydrochloric acid, are allowed to act on excess of granulated zinc, and then distilled.

The distillate is put back once, and 400 grams of hydrochloric acid are added.

The product is distilled to get rid of the alcohol, then excess of alkali added to the residue, and the distillation continued, whereupon propylamine and water come over. Mendius says 36 grams of the cyanide of ethyl yield 9 grams of pure propylamine. The propylamine is dried by distillation from solid potash.

Propylamine is a bright, colourless, highly refracting, very mobile liquid, possessing a peculiar, strongly ammoniacal odour. It mixes with water, heat being generated by the mixture. It boils at 50° C., and has a sp. gr. of ·7134 at 21° C.

Propylamine combines with acids, and forms crystallised salts. The chloride is a very deliquescent salt. The sulphate occurs in crystals, and is also deliquescent. See TRIMETHYLAMINE.

=PROPYL′IC ALCOHOL.= C_{3}H_{7}O. _Syn._ HYDRATED OXIDE OF PROPYL, TRITYL ALCOHOL. A liquid boiling at 204·8° Fahr., obtained by repeatedly rectifying the first products of the distillation of the fusel oil of marc brandy. It stands to ethylic alcohol (ordinary alcohol) in the same relation in which the latter stands to methylic alcohol (pyroxylic spirit).

=PRO′TEIN.= The name given by Mülder to a substance which he regarded as the original matter from which animal albumen, casein, and fibrin, were derived; but which is now considered as a product of the decomposition of those important principles by moderately strong caustic alkali.

_Prep._ (Liebig.) Albumen, casein, or fibrin is dissolved in moderately strong potassa, the solution heated for some time to 120° Fahr., and acetic acid added; a gelatinous precipitate subsides, which, after being washed and dried, is protein.

_Obs._ The names binoxide and teroxide of protein have been given by Mülder to products of the long-continued action of boiling water upon fibrin in contact with the air.

=PRO′TIDE.= A soluble, straw-yellow substance, formed, along with other products, by the action of strong solution of potassa on albumen, fibrin, or casein. See ERYTHROPROTIDE.

=PROTO-.= See NOMENCLATURE.

=PROVI′′SIONS (Preservation of).= See PUTREFACTION.

=PRUNES.= [Fr.] The fruit of cultivated varieties of _Prunus domestica_ (Linn.). The dried fruit (FRENCH PRUNES or PLUMS; PRUNUM——B. P., Ph. L., PRUNA——Ph. E. & D.) is cooling and gently laxative, and, as such, is useful in habitual costiveness and fevers.

=Prunes, Pulp of.= _Syn._ PREPARED PRUNES; PULPA PRUNORUM, PRUNUM PRÆPARATUM (Ph. L.), L. _Prep._ The imported dried fruit is boiled gently for four hours with water, q. s. to cover them, and then pressed, first through a fine cane sieve, and afterwards through a fine hair sieve; the pulp is, lastly, evaporated by the heat of a water bath to the consistence of a confection. A better plan is to use as little water as possible, by which the necessity of subsequent evaporation is avoided. Used in the preparation of confection of senna.

=PRU′NING= varies according to the kind of plant or tree operated on and the particular object in view, and its skilful performance must, therefore, greatly depend on the experience and knowledge of the gardener. “In the operation of pruning, the shoots are cut off close to the buds, or at a distance not greater than the diameter of the branch to be cut off; because without the near proximity of a bud the wounds will not heal over. In shoots which produce their buds alternately the cut is made at the back of the bud sloping from it, so that it may be readily covered by the bark in the same or in the following year; but in the case of branches where the buds are produced opposite each other, either one bud must be sacrificed or the branch must be cut off at right angles to its line of direction, which is most conveniently done with the pruning shears.” (Loudon.)

=PRUS′SIAN AL′KALI.= Ferrocyanide of potassium.

=PRUS′SIAN BLUE.= _Syn._ BERLIN BLUE, PARIS B., FERROCYANIDE OF IRON, PRUSSIATE OF I., CYANURET OF I. This is the well-known blue pigment of the shops.

_Prep._ 1. The crude but clear solution of ferrocyanide of potassium (blood lye) is precipitated by a mixed solution of alum, 2 parts, and green sulphate of iron, 1 part; the dingy greenish precipitate that falls gradually becomes blue by absorption of atmospheric oxygen, which is promoted by exposure and agitation of the liquor; as soon as it has acquired its full colour, the sediment is repeatedly washed with water, and is then drained, and dried, at first in a stove, but afterwards on chalk stones. Product large, but inferior in quality.

2. Repeatedly digest and wash the precipitate obtained by the above process in very dilute hydrochloric acid, and then in pure water; drain and dry it, as before. Superior.

3. (Paris blue.)——_a._ Neutralise the solution of ferrocyanide of potassium (blood lye) with dilute sulphuric acid, precipitate the liquid with a solution of any persalt or sesquisalt of iron (as the persulphate, nitrate, sesquichloride, or peracetate); well wash the precipitate with water, and dry it, as before. A very rich and intense colour.

_b._ (Hochstätter.) Crystallised ferrocyanide of potassium and green sulphate of iron, of each 6 parts, are each separately dissolved in water, 15 parts; after the admixture of the solutions, and frequent agitation, oil of vitriol, 1 part, and fuming hydrochloric acid, 24 parts, are stirred in; after some hours have elapsed a strained solution of chloride of lime, 1 part, dissolved in water, 80 parts, is gradually added, the addition being stopped as soon as an effervescence from the escape of chlorine is perceived; the whole is now left for 5 or 6 hours, when the precipitate is thoroughly washed in pure soft water, drained, and dried. Or, instead of the above, the precipitate is at once washed in dilute nitric acid until its colour ceases to be improved by the process. The product is of the finest quality.

_Prop._ Insoluble in water and in dilute acids, except the oxalic, in solutions of which it dissolves freely when pure; oil of vitriol dissolves it to a white pasty mass, which is again precipitated of the usual blue colour by water; alkalies instantly decompose it, and so do red oxide of mercury and some other oxides when boiled with it; it burns in the air like tinder, leaving an ash of oxide of iron. It is not poisonous.

_Pur., &c._ The quality of Prussian blue may be estimated by the richness of its colour, and by the quantity of potassa or soda required to destroy this. If it effervesces with acids, it contains chalk; and if it forms a paste with boiling water, it is adulterated with starch. It is pure if, “after being boiled with dilute hydrochloric acid, ammonia throws down nothing from the filtered liquid.” (Ph. L. 1836.) It is distinguished from indigo by exhibiting a coppery tint when broken, but which is removed by rubbing with the nail.

_Concluding Remarks._ The commercial Prussian blue is not pure ferrocyanide of iron, but a mixture of this salt with varying proportions of the ferricyanide of iron and potassium, which also has a fine deep blue colour. The object in employing alum is to prevent or lessen the precipitation of oxide of iron by the free alkali in the blood lye, but a portion of alumina is in consequence thrown down with the blue, and tends to render it paler and increase the product. The quantity of alum employed may be varied according to the shades of the intended blue. Samples containing this contamination must not be employed medicinally. (See page 324.)

=Prussian Blue, Sol′uble.= _Prep._ 1. (BASIC PRUSSIAN BLUE.) By adding a solution of protosulphate of iron to a solution of ferrocyanide of potassium; a bluish-white precipitate, turning dark blue by free exposure, is formed, which, after it has acquired this colour, is washed until it begins to dissolve in the water, and colour it blue; it is then either collected and dried, or is at once dissolved in pure water. This variety is not precipitated from its solution by alcohol.

2. (FERROCYANIDE OF POTASSIUM AND IRON.) By precipitating a solution of a sesquisalt or persalt of iron (as the persulphate, pernitrate, peracetate, or sesquichloride) with a stronger solution of ferrocyanide of potassium, so that the latter may be in considerable excess. A blue precipitate is formed, which is treated as before. This variety is precipitated by alcohol. Both are freely soluble in pure water, but not in water which has the slightest saline contamination. Hence it is that lengthened exposure to the atmosphere and the use of the common steel pen causes the gradual precipitation of this substance from its solution when used as ink. See WRITING FLUIDS.

=PRU′′SSIC ACID.= See HYDROCYANIC ACID.

=PSEU′DO-MOR′PHIA.= A substance of little importance, occasionally found in opium. It differs from morphine chiefly in not decomposing iodic acid. It is said to contain nitrogen.

=PTIS′AN.= _Syn._ PTISANA, L. A decoction made of pearl barley, liquorice, raisins, and other like vegetable matters, either alone or so slightly medicated as to be taken as a common drink in fevers, catarrhs, &c. Those retained in English pharmacy have been already noticed. The French physicians often employ this form of medicine. The ’tisanes’ of the P. Cod. are numerous. See DECOCTION, INFUSION, JULEP, TISANE, &c.

=PTY′ALIN.= A peculiar animal matter, analogous to diastase, obtained from the saliva. It is soluble in water, but insoluble in alcohol.

Mialhe named ptyalin “animal diastase,” and regarded it as the principal agent in effecting the digestion of starchy foods, by converting them into soluble glucose. One part of ptyalin, according to Mialhe, was capable of transforming 800 parts of insoluble starch into sugar. It has been computed that the average daily secretion of ptyalin by an adult amounts to 116 grains. It very quickly decomposes, and in properties somewhat resembles sodic albuminate.

=PUCHA PAT.= _Syn._ PATCHOULI. Puchá pât is the dried foliaceous tops of _Pogostemon Patchouli_, an Indian species of _Labiatæ_. It is much used in perfumery, particularly for making sachets; but its odour, although very durable, is not so agreeable as that of many other substances, unless it is combined with lavender, bergamot, ambergris, musk, or some other like perfume.

=PUD′DINGS.= The instructions given under CAKES, PIES, &c., will be found, with some slight modifications, also to apply to puddings, and, therefore, need not be repeated here. Soyer tells us that every sort of pudding, if sweet or savory, is preferably dressed in a basin instead of in a cloth. If boiled in a basin the paste receives all the nutriment of the materials, which, if boiled in a cloth, are dissolved out by the water, when by neglect it ceases boiling. To cause them to turn well out, the inside of the basin should be thoroughly ‘larded’ or rubbed with butter.

In the preparation of meat puddings the first and most important point is never to use any meat that is tainted; for in pudding, above all other dishes, it is least possible to disguise it by the confined progress which the ingredients undergo. The gradual heating of the meat, which alone would accelerate decomposition, will cause the smallest piece of tainted meat to contaminate all the rest. Be particular, also, that the suet and fat are not rancid, ever remembering the grand principle that everything which gratifies the palate nourishes.”

“A pudding cloth, however coarse, ought never to be washed with soap; it should be simply dried as quickly as possible, and kept dry and free from dust, and in a drawer or cupboard free from smell.” (Soyer.)

=PUD′DLING.= See IRON.

=PULMONI′TIS.= Inflammation of the lungs.

=PULP.= _Syn._ PULPA, L. The softer parts of plants, more particularly of fruits, separated from the fibrous and harder portions.

“Pulpy fruits, if they be unripe, or ripe and dried, are to be placed in a damp situation until they become soft; then the pulp is to be pressed out through a hair sieve; afterwards it is to be boiled with a gentle heat, frequently stirring; and finally, the (excess of) water is to be evaporated in a water bath, until the pulp acquire proper consistence.

“Press the pulpy fruits which are ripe and fresh through a hair sieve, without boiling them.” (Ph. L. 1836.)

=PULVERISA′TION.= The reduction of any substance to dust or powder.

On the small scale, pulverisation is usually performed by means of a pestle and mortar; on the large scale, by stamping, grinding or cutting the substance in a mill. A few soft substances, as carbonate of magnesia, carbonate of lead, &c., may be pulverised by simply rubbing them through a fine sieve, placed over a sheet of paper; whilst many hard, gritty substances can only be reduced to fine powder by porphyrisation or levigation. Elutriation, or ‘washing over,’ is adopted for several substances, as chalk, antimony, &c., which are required to be reduced to fine powder on the large scale. For some articles which are very tough, fibrous, or resisting, a rasp or file is employed. Whichever of these methods is adopted, the body to be powdered must be very dry, and where spontaneous drying is insufficient, artificial desiccation in a stove or oven, gently heated, is employed. To facilitate this, the substance should be first cut into pieces or crushed small. On the other hand, a few substances, as rice, sago, nux vomica, and St Ignatius’s bean, are often soaked in water, or steamed, before being further operated on. Whenever a substance cannot be dried completely, without an alteration of its properties, an intermedium is had recourse to, by which the moisture may be absorbed, or its state of aggregation modified. Thus, sugar is employed in pulverising civet, musk, nutmeg, and vanilla. When camphor is to be pulverised, the addition of a very small quantity of alcohol renders the operation easy. In other cases the intermedium is of so hard a nature as to assist in breaking down the substance to be powdered; thus, gold leaf is reduced to powder by rubbing it with sulphate of potassa, and afterwards removing this last by means of water. Fusible metals, as zinc and tin, are powdered by pouring them into a mortar, and stirring them rapidly whilst cooling; or, by briskly agitating them, in the melted state, in a wooden box covered with chalk or whiting. Phosphorus is powdered by melting it in urine or lime water, and then shaking the bottle until its contents have become quite cold. Glass, quartz, and silicated stones, require to be heated red hot, and in this state to be thrown into cold water, by which they become sufficiently friable to admit of pulverisation. Many salts which are reduced to fine powder with very great difficulty, and do not dissolve in spirit of wine, are easily obtained in a pulverulent form, by agitating their concentrated aqueous solution with a considerable quantity of rectified spirit; the disengaged fine crystallised powder may then be dried, and further divided by trituration. Potassio tartrate of antimony may be advantageously thus treated. A large number of salts, including nitre, sal ammoniac, and carbonate of potash, may also be reduced to powder by keeping their solutions in a state of constant and violent agitation during their rapid evaporation.

The following rules should be observed in the preparation of powders:——

1. If possible, perfectly dry articles should alone be operated on, and only in dry weather.

2. The nature of the mortar, and the mode of operating, should be adapted to the nature of the substance. Thus, woods and barks should be pulverised in an iron mortar; sugar, alum, and nitre, in one of marble or wedgwood-ware; and corrosive sublimate, only in one of glass.

3. The mortar should be provided with a cover, to prevent loss and annoyance to the operator. If much powder escapes, or if it is dangerous or disagreeable when breathed, or if the substance is rare or costly, the mortar should be covered with a skin of leather, to which the pestle is attached, so that the latter may be freely moved without causing the slightest opening for the escape of the dust occasioned by the process. When aloes or gamboge is powdered, a few drops of olive oil are commonly added with the same intention.

4. The pulverised portions should be separated from time to time by aid of a sieve, the coarser particles being returned to the mortar to be again beaten and triturated; and this alternate pulverisation and sifting is to be repeated until the process is complete.

=PUM′ICE STONE.= _Syn._ PUMEX, LAPIS PUMICEUS, L. PUMICIS, L. Found in the neighbourhood of volcanoes. Used, in the solid form, to polish wood, paint, &c.; also, when pulverised, as a polishing powder for glass, bone, ivory, marble, metals, &c.

=PUMP FOR USE IN CHEMICAL, PAPER, and other Works.= The Perreaux Pump Valve is made of vulcanised india rubber, and is of the form of the valves in the human body. It is of the greatest, and perhaps the really only valuable improvement in valves applicable, equally, to the common hand or jack pump, and the most elaborate mechanical combinations for raising water.

The valve may be taken as the key of the pump; a perfect valve renders an indifferent pump a valuable and effective machine, whereas an imperfect valve, in an otherwise excellently constructed pump, renders it practically useless.

The pump which Simon the tanner, of Joppa, used for pumping his pits, nearly two thousand years ago, may be taken as the type of the common hand pump in use to this day. Various mechanical improvements have been made in its form and construction, but, practically, and effectively, the only real and valuable improvement is the Perreaux valve, now under consideration.

Constructed of a flexible material, and made in form, as nearly as may be, to the valves of the human body, they may be said to be automatic in their action, or self acting; upon the pump being actuated, the least motion of the pump ensuring a corresponding action of the valve, and the most rapid action of the pump, being equally responded to by the pulsation of the valves.

Although the most perfect valves for pumping clear water, because, what is mechanically termed the duty of the pump is complete, in other words, the quantity displaced is discharged, absolutely without loss, yet their most valuable feature is that they pump semi-fluids equally well as clear water.

For the pulps and stuffs in paper mills, for bleaches, dyes, and corrosive liquors, for liquid manures and other such semi-fluids, they stand alone, they are absolutely unchokable.

Used in conjunction with cylinders or barrels made of toughened glass, they form the most perfect pump where the fluid to be raised is of a caustic or corrosive nature, and where the fluid would be destructive to or destroyed by its action upon metals, such for example as the caustic bleach used in the manufacture of paper, &c. See VALVES.

=PUNCH.= An acidulous, intoxicating beverage, composed of water sweetened with sugar, with a mixture of lemon juice and spirit, to which some aromatic, as nutmeg, mace, or cinnamon, is occasionally added. Wine is sometimes substituted for spirit. It is much less drunk than formerly. Rum punch is the most popular amongst sailors, who are now the principal consumers of this beverage.

_Prep._ 1. Juice of 3 or 4 lemons; yellow peel of 1 lemon; lump sugar, 3/4 lb.; boiling water, 3-1/2 pints; infuse 1/2 an hour, strain, and add, of bitter ale, 1/2 pint; rum and brandy, of each 3/4 to 1 pint (or rum alone, 1-1/2 to 2 pints). More hot water and sugar may be added if the punch is desired either weaker or sweeter.

2. (COLD PUNCH.) From arrack, port wine, and water, of each 1 pint; juice of 4 lemons; white sugar, 1 lb.

3. (GIN PUNCH.) From the yellow peel of 1/2 a lemon; juice of 1 lemon; strongest gin, 3/4 pint; water, 1-3/4 pint; sherry, 1 glassful.

4. (ICED PUNCH.) From champagne or Rhenish wine, 1 quart; arrack, 1 pint; juice of 6 lemons; yellow peel of 3 lemons; white sugar, 1 lb.; soda water, 1 or 2 bottles; to be iced as cream.

5. (MILK PUNCH; VERDER.) Steep the yellow rinds of 18 lemons and 6 oranges, for 2 days, in rum or brandy, 2 quarts; then add 3 quarts more of either spirit; hot water, 3 quarts; lemon juice, 1 quart; loaf sugar, 4 lbs.; 2 nutmegs, grated; and boiling milk, 2 quarts; mix well, and in 2 hours strain the liquor through a jelly-bag.

6. (NORFOLK PUNCH.) Take of French brandy, 20 quarts; yellow peels of 18 oranges and 30 lemons; infuse for 12 hours; add, of cold water, 30 quarts; lump sugar, 20 lbs.; and the juice of the oranges and lemons; mix well, strain through a hair sieve, add of new milk 2 quarts, and in 6 weeks bottle in. Keeps well.

7. (ORANGE PUNCH.) As No. 1, using oranges, and adding some orange wine, if at hand. A little curacoa, noyau, or mareschino improves it.

8. (RASPBERRY PUNCH.) As the last, but using raspberry juice, or raspberry vinegar, for the oranges or lemons.

9. (REGENT’S PUNCH.) From strong hot green tea, lemon juice, and capillaire, of each 1-1/2 pint; rum, brandy, arrack, and curacoa, of each 1 pint; champagne, 1 bottle; mix and slice a pineapple into it.

10. (TEA PUNCH.) From strong hot tea, 1 quart; arrack, 1/2 bottle; white sugar, 6 oz.; juice of 8 lemons; and the yellow rinds of 4 lemons; mixed together.

11. (WINE PUNCH.) From white sugar, 1 lb.; yellow peel of 3 lemons; juice of 9 lemons; arrack, 1 pint; port or sherry (hot), 1 gall.; cinnamon, 1/4 oz.; nutmeg, 1 dr.; mix.

12. (YANKEE PUNCH.) Macerate sliced pineapple, 3 oz.; vanilla, 6 gr.; and ambergris (rubbed with a little sugar), 1 gr., in the strongest pale brandy, 1 pint, for a few hours, with frequent agitation; then strain with expression; add, of lemon juice, 1 pint; lemon syrup, and either claret or port wine, of each 1 bottle; with sugar, 1/2 lb., dissolved in boiling water, 1-1/2 pint. See SHRUB.

=PURG′ATIVES.= _Syn._ DEJECTORIA, PURGANTIA, PURGATIVA, L. These have been divided into five orders or classes, according to their particular actions. The following are the principal of each class:——

1. (LAXATIVES, LENITIVES, or MILD CATHARTICS.) Manna, cassia pulp, tamarinds, prunes, honey, phosphate of soda; castor, almond, and olive oils; ripe fruit.

2. (SALINE or COOLING LAXATIVES.) Epsom salt, Glauber’s salt, phosphate of soda (tasteless salt), seidlitz powders, &c.

3. (ACTIVE CATHARTICS, occasionally acrid, frequently tonic and stomachic.) Rhubarb, senna, aloes, &c.

4. (DRASTIC or VIOLENT CATHARTICS.) Jalap, scammony, gamboge, croton oil, colocynth, elaterium, &c.

5. (MERCURIAL PURGATIVES.) Calomel, blue-pill, quicksilver with chalk, &c.

In prescribing purgatives regard should be had to the particular portion of the alimentary canal on which we desire more immediately to act, as well as to the manner in which the medicine effects its purpose. Thus, Epsom salt, sulphate of potassa, and rhubarb, act chiefly on the duodenum; aloes on the rectum; blue-pill, calomel, and jalap on the larger intestines generally; and tartrate and bitartrate of potassa, and sulphur on the whole length of the intestinal canal. Again, others are stimulant, as aloes, croton oil, jalap, scammony, &c.; others are refrigerant, as most of the saline aperients; magnesia and its carbonate are both aperient and antacid; whilst another class, including rhubarb, damask roses, &c., are astringent. Further, some produce only serous or watery dejections, without greatly increasing the peristaltic action of the bowels; whilst a few occasion a copious discharge of the fæces in an apparently natural form. See DRAUGHT, MIXTURE, PILLS, PRESCRIBING, &c.

=PURL.= _Prep._ To ale or beer, 1/2 pint, gently warmed, add of bitters, 1 wine-glassful, or q. s. Some add a little spirit. A favourite beverage with hard drinkers early in the morning.

=PUR′PLE.= A rich compound colour, produced by the admixture of pure blue and pure red. This colour has always been the distinguishing badge of royalty and distinction. The celebrated Tyrian purple was produced from a shell-fish called murex.

=Purple An′iline.= _Syn._ PERKIN’S PURPLE, MAUVE. This valuable dye-stuff is prepared under W. H. Perkin’s patent, by mixing solutions of sulphate of aniline and bichromate of potassa in equivalent proportions, and, after some hours, washing the black precipitate with water, drying it, digesting it repeatedly in coal-tar naphtha, and, finally, dissolving it in boiling alcohol. It may be further purified by evaporating the alcoholic solution to dryness, dissolving the residue in a large quantity of boiling water, reprecipitating by caustic soda, washing with water, dissolving in alcohol, filtering, and evaporating to dryness. Thus purified, mauve forms a brittle substance, having a bronze-coloured surface. It imparts a deep purple colour to cold water, though dissolving sparingly in that liquid; it is more soluble in hot water, and very soluble in alcohol. See PURPLE DYE (_below_), and TAR COLOURS.

=Purple of Cassius.= _Syn._ PURPLE PRECIPITATE OF CASSIUS, GOLD PURPLE, GOLD PREPARED WITH TIN; AURUM STANNO PARATUM, PURPURA MINERALIS CASII, L. _Prep._ 1. Crystallised protochloride of tin, 1 part; crystallised perchloride of tin, 2 parts; dissolve each separately, mix the solutions, and add of crystallised terchloride of gold (in solution), 1 part; carefully wash, and dry the precipitate. Very fine.

2. (Frick.) Dissolve pure grain tin in cold dilute aqua regia until the fluid becomes faintly opalescent, then take the metal out and weigh it; next, dilute the solution largely with water, and add, simultaneously, a dilute solution of gold and dilute sulphuric acid in such proportion that the tin in the one shall be to the gold in the other in the ratio of 10 to 36.

3. (P. Cod.) Terchloride of gold, 1 part, is dissolved in distilled water, 200 parts; another solution is made by dissolving in the cold, pure tin, 1 part, in a mixture of nitric acid, 1 part, and hydrochloric acid, 2 parts; this last solution is diluted with distilled water, 100 parts, and is then added to the solution of terchloride of gold until precipitation ceases to take place; the powder is, lastly, washed by decantation, and dried by a very gentle heat.

4. Silver, 150 parts; gold, 20 parts; pure grain tin, 35 parts; fuse them together under charcoal and borax, cool, laminate, and dissolve out the silver with nitric acid.

_Obs._ Purple of Cassius is generally supposed to be a combination of oxide of gold and sesquioxide of tin, in which the latter acts as an acid. Heat resolves it into a mixture of metallic gold and binoxide of tin. It is used as a purple in porcelain painting, and to communicate a ruby-red colour to glass, when melted in open vessels.

=PURPLE DYE.= The purples now in vogue are the numerous shades of ‘mauve’ and ‘magenta’ obtained by the ‘aniline colours.’ (See _above_, also RED.) For silk and woollen goods no mordant is required. The proper proportion of the clear alcoholic solution is mixed with water slightly warm, any scum that may form is cleared off, and the goods are entered and worked until the required shade is obtained; a small quantity of acetic or tartaric acid is recommended to be added in some cases. For dyeing on cotton with the aniline colours, the cloth or yarn is steeped in sumac or tannic acid, dyed in the colour, and then fixed by tin; or it may be steeped in sumac and mordanted with tin, and then dyed. Purples were formerly, and are still occasionally, produced by first dyeing a blue in the ‘indigo vat,’ and then dyeing a cochineal or lac scarlet upon the top. See VIOLET DYE.

=PUR′PURATE OF AMMO′′NIA.= See MUREXIDE.

=PURPU′RIC ACID.= See MUREXAN.

=PURPURIN.= C_{9}H_{6}O_{3}. _Syn._ MADDER PURPLE. The name given by Robiquet and Colin to a beautiful colouring principle obtained from madder.

_Prep._ Coarsely powdered madder is allowed to ferment with water, after which it is boiled in a strong solution of alum; the decoction is next mixed with sulphuric acid, and the resulting red precipitate is purified by one or more crystallisations from alcohol.

_Prop., &c._ Crystalline red needles, insoluble in cold water, but soluble in hot water, and in alcohol, ether, and solutions of alum and the alkalies. It differs from alizarin or madder red in containing 2 atoms less of carbon.

=PUR′REE.= _Syn._ INDIAN YELLOW. A yellow substance, of doubtful origin, imported from China and India, and now extensively used in both oil and water-colour painting. According to the researches of Stenhouse and Erdmann it consists of purreic acid, a strongly tinctorial vegetable substance, united to magnesia.

=PURRE′IC ACID.= _Syn._ EUXANTHIC ACID. This substance is obtained from purree. It crystallises in nearly colourless needles, which are only sparingly soluble in cold water, and forms rich yellow-coloured compounds with the alkalies and earths. Heat converts it into a neutral, crystallisable substance, called purrenone.

=PUS.= The cream-like, white or yellowish liquid secreted by wounded surfaces, abscesses, sores, &c.

=PUTREFAC′TION.= _Syn._ PUTREFACTIO, L. The spontaneous decomposition of animal and nitrogenised vegetable substances, under the joint influence of warmth, air, and moisture. The solid and fluid matters are resolved into gaseous compounds and vapours, which escape, and into earthy matters, which remain. The most striking characteristic of this species of decomposition is the ammoniacal or fetid exhalations that constantly accompany it.

The nature of putrefaction, and the conditions essential to its occurrence, have been briefly alluded to under fermentation, to which we must refer the reader. It may here, however, be useful to reiterate that this change can only be prevented by the abstraction or exclusion of the conditions essential to its occurrence. This may be affected by——reduction of temperature,——exclusion of atmospheric air, or——the abstraction of moisture. The antiseptic processes in common use are effective in precisely the same degree as these preventive means are carried out. Frozen meat may be preserved for an unlimited period, while the same substance will scarcely keep for more than a few days at the ordinary heat of summer. Animal substances will also remain uninjured for a long period if kept in vessels from which the air is entirely excluded, as in the process now so extensively adopted for the preservation of fresh meat for the use of our army and marine. The third condition is fulfilled when nitrogenised matter is preserved in alcohol, brine, or any similar fluid, and when it is dried. In either case water is abstracted from the surface, which then loses its propensity to putrefy, and forms an impervious layer, which excludes atmospheric oxygen from the interior and softer portion of the substance. Creasote, and most of the antiseptic salts, also act in this way.

Among special antiseptic processes are the following:

APPLICATION OF COLD. The accession of putrefaction is prevented, and its progress arrested, by a temperature below that at which water freezes. In the colder climates of the world, butchers’ meat, poultry, and even vegetables, are preserved from one season to the other in the frozen state. In North America millions are thus supplied with animal food, which, we can state, from personal experience, is often superior in flavour, tenderness, and apparent freshness, to that from the recently killed animal. In temperate climates, and in cold ones during their short summer, ice-houses and ice-safes afford a temperature sufficiently low for keeping meat fresh and sweet for an indefinite period. Substances preserved in this manner should be allowed to gradually assume their natural condition before cooking them; and on no account should they be plunged into hot water, or put before the fire, whilst in the frozen state.

BUCANING. A rude kind of drying and smoking meat, cut into thin slices, practised by hunters in the prairies and forests.