Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 127

_g._ Stop-c.o.c.k to regulate or arrest the pressure of air on the contents of the cylinder (_a_).]

The method of displacement, although apparently simple, requires for its successful application no inconsiderable amount of experience and skill in manipulation. The princ.i.p.al points to be attended to are--the reduction of the substance to the proper state of comminution (neither too coa.r.s.e nor too fine),--the due regulation of the period of maceration according to the hardness, density, and texture of the substance; and, more important still,--the proper packing of the ingredients in the cylinder. On the correct performance of the last the success of the process mainly depends.

Some substances require considerable pressure to be used, whilst others, when even lightly packed, scarcely permit the fluid to pa.s.s through them.

When the material is too loosely packed, the menstruum pa.s.ses through quickly, but without exerting its proper solvent action; when too great pressure is employed, percolation either progresses very slowly or not at all. On the whole, the firmness of the packing should be inversely as the solvent and softening power of the menstruum upon the solids exposed to its action; but to this rule there are many exceptions, and each substance may be said to require special treatment. An excellent plan, applicable to all substances, and especially to those of a glutinous or mucilaginous nature, is to mix the powder with an equal bulk of well-washed siliceous sand before rubbing it up with the menstruum. In reference to the coa.r.s.eness of the powder it must be observed that substances which readily become soft and pappy when wetted by the menstruum, should not be used so fine as those that are more woody and fibrous, and not of a glutinous or resinous nature.

The 'method of displacement' has the advantage of expedition, economy, and yielding products possessing considerable uniformity of strength; but the difficulties attending its application by the inexperienced are serious obstacles to its general adoption in the laboratory. It answers admirably for the preparation of all tinctures that are not of a resinous nature, and for most infusions of a woody and fibrous substances, as roots, woods, barks, leaves, seeds, insects, &c., and particularly when cold or tepid water is taken as the solvent. It is also especially adapted for the preparation of concentrated infusions and essences, as they may thus be obtained of any required strength without loss, or requiring concentration by heat, which is so destructive to their virtues.

"When (ordinary) tinctures are made in large quant.i.ties, displacement is never likely to supersede maceration, on account of any practical advantages it may possess. If the prescribed directions be duly attended to, the process of maceration is unexceptionable. The process is more simple than the other; the mode of operating is more uniform, it is, in fact, always the same; it requires less of skill and dexterity in conducting it; it requires less constant attention during its progress which, in operating on large quant.i.ties is a consideration; and, finally, the apparatus required is less complicated. When, however, only small quant.i.ties of tincture are made at a time, and kept in stock, the adoption of the process of displacement will often be found convenient and advantageous. It offers the means of making a tincture in two or three hours, which, by the other process, would require as many weeks." (Mohr and Redwood.)

Another useful application of the method of displacement is to the manufacture of extracts on the large scale. Here it is superior to any other plan. By the simple and inexpensive forms of apparatus in block-tin, stoneware, or gla.s.s, which have recently been designed for the purpose, not merely a first-cla.s.s product is ensured, but a great saving in fuel and labour is at the same time effected. The reader is referred to the last edition of the 'United States Pharmacopia,' and to papers by Messrs Saunders and Schweitzer in the 'Pharmaceutical Year Book for 1873,' and by Mr Campbell in the same publication for 1874, for additional information in the subject of "Percolation." See BREWING, EXTRACT, TINCTURE, &c.

=PERCUS'SION.= _Syn._ PERCUSSIO, L. In _medicine_, the act of striking any part of the body with the fingers, or any instrument, to ascertain its condition.

=PERCUS'SION CAPS.= The composition employed to prime these articles is noticed under FULMINATING MERCURY.

=PER'FECT LOVE.= See LIQUEUR (Parfait amour).

=PER'FUME.= A substance that emits or casts off volatile particles which, when diffused through the atmosphere, agreeably affect the organs of smelling. The term is also applied to the volatile effluvia so perceived.

The princ.i.p.al source of perfumes is the Vegetable Kingdom. Its flowers, seeds, woods, and barks furnish a rich variety, from which the most fastidious connoisseur may select his favourite bouquet. A few perfumes, as musk, ambergris, and civet, are derived from the Animal Kingdom; but none of these evolve an aroma comparable in freshness to that of the rose, or in delicacy to that of the orange-blossom, or even the unpretending jasmine. The Inorganic Kingdom yields not a single perfume, so called; nor has the science of chemistry yet been able to produce a single odoriferous compound from matter absolutely inorganic.

=PERFU"MERY.= Perfumes in general; also the art of perfuming them. In its commercial application, this word embraces not merely perfumes, but also cosmetics, and other articles of a closely allied character employed at the toilet, the manufacture and sale of which const.i.tute the trade of the modern perfumer. Formulae for the preparation of all the more valuable perfumes, as well as of others met with in trade, both simple and compound, will be found under the heads COSMETICS, DEPILATORY, ESSENCE, HAIR DYES, OILS, PASTES, PASTILS, POMADE, SPIRIT, WATERS, &c., to which we refer the reader.

=PERFUMES, ACE'TIC.= See VINEGAR.

=Perfumes, Ammo"niated.= These may be prepared by simply adding a sufficient quant.i.ty of ammonia to the liquid perfumes. When the articles are to be distilled, a cheaper plan is to add about 5 dr. of sal ammoniac and 8 dr. of carbonate of pota.s.sa to each pint of the article just before distillation. Ammoniated Cologne water is now a fas.h.i.+onable substance for spirit of sal volatile.

=PERIODIC ACID.= _Syn._ HYDRIC PERIODATE. (HIO_{4}.) 1. By pa.s.sing a current of chlorine gas through a solution of sodic iodate, containing caustic soda, in the proportion of 3 atoms of the latter to one atom of sodic iodate. The hydrated basic sodic periodate, which crystallises out, is dissolved in diluted nitric acid, and precipitated by the addition of argentic nitrate; a normal argentic periodate crystallises as the liquid cools, and this salt being treated with water, is decomposed into a basic argentic periodate, which is insoluble, and periodic acid, which is dissolved. By evaporating the solution, the periodic acid may be obtained in deliquescent, oblique, rhombic prisms, which are somewhat soluble in alcohol and in ether.

2. From perchloric acid by the action of iodine. See IODINE.

=PERISTAL'TIC PERSUA'DERS.= See PILLS (Kitchener's).

=PER'MANENT WHITE.= See BARIUM (Sulphate) and WHITE PIGMENTS.

=PERNAMBU'CO WOOD.= _Syn._ PEACH WOOD. The wood of _Caesalpinia echinata_.

It const.i.tutes the paler variety of Brazil wood used by the dyers.

=PER'RY.= _Syn._ PYRACEUM, L. A fermented liquor prepared from pears in the same way as cider is from apples. The red rough-tasted sorts are princ.i.p.ally used for this purpose. The best perry contains about 9% of absolute alcohol; ordinary perry from 5 to 7%.

Perry is a very pleasant-tasted and wholesome liquor. When bottled 'champagne fas.h.i.+on,' we have seen it frequently pa.s.sed off for champagne without the fraud being suspected.

=PER'SIAN BER'RIES.= See FRENCH BERRIES.

=PERSPIRA'TION.= The liquid or vapour secreted by the ramifications of the cuticular arteries over the surface of the body. The perspiratory apparatus consists of a gland deeply seated in the corium, communicating by means of tubules (pores) with the surface of the scarf-skin.

The uses of the perspiratory functions appear to be to preserve the suppleness and sensibility of the skin, to maintain the temperature of the body at a uniform standard, and to remove from the system a number of compounds noxious to animal life. The perspiration "is a fluid whose regularity and continuance of exhalation are not merely conducive, but absolutely necessary, to health; without such regularity the animal temperature would run riot, and substances of an injurious quality would be allowed to permeate the finest and most delicate of the tissues of the body." (Eras. Wilson.) "From the constriction or constipation of the cutaneous pores by the ambient air, especially when the body, beforehand put into a heat, is suddenly exposed thereunto, the serous particles which used to fly off continually in vapour, being now pent in, excite an intense and feverish effervescence; till, finding some other pa.s.sage, either by the kidneys or by the glandules of the nose and windpipe, they are discharged by way of a catarrh; or, missing this separation, still keep up the ebullition, very often to the hazard of life, by suffocating the vital flame. And this is the natural consequence of obstructed insensible perspiration, which, in the vulgar phrase, is the same with what they mean by catching cold, and of which, give me leave to remark, that as fevers make two thirds of diseases infesting mankind, according to the computation of the judicious Sydenham, so two thirds of fevers very probably may take their rise from perspiration hindered." (Daniel Turner.) Suppressed perspiration is also one of the commonest causes of diarrha.

=PERU'VIAN BALSAM.= See BALSAM OF PERU.

=PERU'VIAN BARK.= See CINCHONA.

=PES'SARY.= _Syn._ PESSUM, PESSARIUM, L. An instrument made of caoutchouc, gutta percha, box-wood, or ivory, inserted into the v.a.g.i.n.a to support the mouth and neck of the uterus. They are variously formed, to meet the prejudices of the party or the necessities of the case. The cup, conical, globe, and ring pessaries (pessi) are those best known.

Medicated pessaries are prepared by adding the active ingredients to a hard cerate, and pressing the mixture into the desired form. Astringents (various), belladonna, acetate of lead, mercury, &c., have been thus applied by Dr Simpson and others.

The different formulae are given below:--

=Pessary, Alum.= _Syn._ PESSUS ALUMINIS. Alum, catechu, wax, of each 1 dr.; lard, 5-1/2 dr.

=Pessary, Belladonna.= _Syn._ PESSUS BELLADONNae. Extract of belladonna, 10 gr.; wax, 22-1/2 gr.; lard, 1-1/2 dr.; in each pessary.

=Pessary, Mercurial.= _Syn._ PESSUS HYDRARGYRI. Strong mercurial ointment, 1/2 dr.; wax, 1/2 dr.; lard, 1 dr. Mix.

=Pessary, Lead.= _Syn._ PESSUS PLUMBI. Acetate of lead, 7-1/2 gr.; white wax, 22-1/2 gr.; lard, 1-1/2 dr.

=Pessary, Iodide of Lead.= _Syn._ PESSUS PLUMBI IODIDI. Iodide of lead, 5 gr.; wax, 25 gr.; lard, 1-1/2 dr.

=Pessary, Tannin.= _Syn._ PESSUS TANNINI. Tannin, 10 gr.; wax, 25 gr.; lard, 1-1/2 dr.

=Pessary, Zinc.= _Syn._ PESSUS ZINCI. Oxide of zinc, 15 gr.; white wax, 22-1/2 gr.; lard, 1-1/2 dr.

=PEST'ILENCE.= See PLAGUE.

=PESTILEN'TIAL DISEASES.= All those diseases which are epidemic and malignant and a.s.sume the character of a plague. See CHOLERA, &c.

=PETONG'.= Same as _packfong_.

=PET'ROLENE.= The pure liquid portion of mineral tar. It has a pale yellow colour, a penetrating odour, and a high boiling point; is lighter than water, and is isomeric with the oils of turpentine and lemons. In its general proportions it resembles rectified mineral naphtha.

=PETRO'LEUM.= _Syn._ ROCK OIL, LIQUID BITUMEN, OIL OF PETRE; OLEUM PETRae, BITUMEN LIQUIDUM, L. PETROLEUM is an oil found oozing from the ground or obtained on sinking wells in the soil. To a limited extent it is met with in most countries of Europe and in the West India islands, but occurs in abundance in Pennsylvania and other parts of the United States and in Canada. It varies in colour from slight yellow to brownish black, in consistence from a thin mobile liquid to a fluid as thick as treacle, in specific gravity from 800 to 1100 (water being 1000) and is either clear and transparent or turbid and opaque. Petroleum is essentially a volatile oil, and when submitted to distillation yields gases h.o.m.ologous with light carburetted hydrogen of marsh-gas (Ronalds obtained three), liquids of similar const.i.tution (Pelouze and Cahours isolated twelve), and solid paraffin-like bodies. Commercially petroleum is distilled so as to yield petroleum-spirit or mineral naphtha used as a subst.i.tute for turpentine and for burning in sponge-lamps and costermongers' barrow-lamps; petroleum oil used all over the world as mineral lamp oil for illuminating purposes; and a heavy oil employed for lubricating machinery. The value of a sample of rock-oil is determined by thus distilling a weighed quant.i.ty in a small gla.s.s retort and weighing the products. The petroleum or middle product must be of such a character as to have a specific gravity not higher than 810 or 820 and to contain so little petroleum spirit that it only evolves inflammable vapour when heated to 100 Fahr. in the manner prescribed in the Petroleum Act, 1871 (see _below_). Any petroleum product or mineral oil which will not stand this test, and which is kept in larger bottles than one pint, and in larger total quant.i.ty than three gallons, cannot be stored or sold except by licence of the local authorities.

_Directions for Testing Petroleum to ascertain the temperature at which it gives off inflammable vapour._

The vessel which is to hold the oil shall be of thin sheet iron; it shall be two inches deep and two inches wide at the opening, tapering slightly towards the bottom; it shall have a flat rim, with a raised edge one quarter of an inch round the top; it shall be supported by this rim in a tin vessel four inches and a half deep and four and a half inches in diameter; it shall also have a thin wire stretched across the opening, which wire shall be so fixed to the edge of the vessel that it shall be a quarter of an inch above the surface of the flat rim. The thermometer to be used shall have a round bulb about half an inch in diameter, and is to be graduated upon the scale of Fahrenheit, every ten degrees occupying not less than half an inch upon the scale.

The inner vessel shall be filled with the petroleum to be tested, but care must be taken that the liquid does not cover the flat rim. The outer vessel shall be filled with cold, or nearly cold water; a small flame shall be applied to the bottom of the outer vessel, and the thermometer shall be inserted into the oil so that the bulb shall be immersed about one and a half inches beneath the surface. A screen of pasteboard or wood shall be placed round the apparatus, and shall be of such dimensions as to surround it about two thirds and to reach several inches above the level of the vessels.

When heat has been applied to the water until the thermometer has risen to about 90 Fahr., a very small flame shall be quickly pa.s.sed across the surface of the oil on a level with the wire. If no pale blue flicker or flash is produced, the application of the flame is to be repeated for every rise of two or three degrees in the thermometer. When the flas.h.i.+ng-point has been noted, the test shall be repeated with a fresh sample of the oil, using cold, or nearly cold water as before; withdrawing the source of heat from the outer vessel when the temperature approaches that noted in the first experiment, and applying the flame test at every rise of two degrees in the thermometer. See NAPHTHA, OILS (Mineral), &c.

=PEW'TER.= This is an alloy of tin and lead, or of tin with antimony and copper. The first only is properly called pewter. Three varieties are known in trade:--

_Prep._ 1. (PLATE PEWTER.) From tin, 79%; antimony, 7%; bis.m.u.th and copper, of each 2%; fused together. Used to make plates, teapots, &c.

Takes a fine polish.

2. (TRIPLE PEWTER.) From tin, 79%; antimon, 15%; lead, 6%; as the last.

Used for minor articles, syringes, toys, &c.

3. (LEY PEWTER.) From tin, 80%; lead, 20%. Used for measures, inkstands, &c.