Part 51
PRESSURE:--The weight or pressure of the atmosphere is shown by the rise of water in the barrel of the common 'lifting pump' and the suspension of the mercurial column in the tube of the barometer. The last affords a ready means of determining the actual pressure of the air, the column of mercury, and the column of air by which it is suspended, resembling two weights in equilibrio, at the opposite extremities of the same balance. The mean height of the barometer at the level of the sea, in England, is 28·6 inches (= about 33-1/2 feet of water); and as a cubic inch of mercury weighs 3425·92 gr., or ·48956 _lb._, it follows that the weight of a column of mercury whose base is a square inch is 14·6 _lbs._ avoirdupois. The pressure of the atmosphere is not merely downwards, but is equally diffused in all directions, and exerts a most powerful effect in the economy of organic beings. On the surface of the body of an adult of ordinary size (say = 15 sq. feet, or 2160 inches), it amounts to the enormous weight of 31,536 _lbs._, which is not sensible, only because it is balanced by the force of the elastic fluids in the interior of the body. Were this equilibrium to be suddenly destroyed, the consequence would be, either that the body would be instantly torn to pieces with explosive violence, or that it would be crushed under the overwhelming weight that would suddenly fall upon it. Even the comparatively slight variations of atmospheric pressure which occur with changes of wind, weather, and season, exercise a perceptible effect on the functions of life.
_Mean pressure of the Atmosphere at the level of the Sea, in different latitudes, at 32° Fahr., expressed in inches of mercury_.
+------------+----------+-----------+-----------+------------ Lat. | Height | Lat. | Height | Lat. | Height | (inches). | | (inches). | | (inches). -----+------------+----------+-----------+-----------+------------ 0° | 29·930 | 40° | 30·019 | 54-1/2° | 29·926 10 | 29·975 | 45 | 30·000 | 60 | 29·803 20 | 30·064 | 49 | 29·978 | 64 | 29·606 30 | 30·108 | 51-1/2 | 29·551 | 67 | 29·673 -----+------------+----------+-----------+-----------+------------
TEMPERATURE:--The temperature of the atmosphere, independently of changes arising from variations of latitude and season, diminishes, like its density, with its elevation. In general, every 100 yards of ascent causes the temperature to fall 1° Fahr. See AIR (Atmospheric), EPIDEMICS, VENTILATION, &c.
=Atmosphere=. In _engineering_ and _pneumatics_, the pressure of a column of mercury at 0° Cent. or 32° Fahr., which is 76 centimètres or 29·9218 inches high, at the mean level of the sea in latitude 45°, taken as a standard of that exerted by other elastic fluids. In practice this is assumed to be 15 _lbs_. to the square inch, under a barometrical pressure of 30 inches. Thus, steam or air condensed so as to exert a pressure of 30 _lbs_. per sq. inch is said to be of two atmospheres; at 45 _lbs_., of three atmospheres, &c.
=AT'OM (-[)u]m). Atomic Weight, Atomic Theory=. _Syn_. AT'OMUS, L.; ATOME, Fr.; ATOM, UNTHEILBARE THEILCHEN, Ger.
ATOMIC WEIGHT. When the elements unite chemically, they invariably do so in the proportions by weight represented by the numbers attached to them in the following table, or in multiples of these proportions. Dalton accounted for this law by supposing that the constituent particles of matter are indivisible, and believed that, if it were possible to place such particles in the balance, their relative weights would be found to correspond with the numbers given in the table.[101] In other words, the term _atom_, which is derived from the Greek [Greek: atomos], indivisible, is applied in modern chemistry to the smallest quantity by weight of an element which is capable of existing in a chemical compound, hydrogen being taken as unity.
[Footnote 101: Strictly speaking, Dalton, the inventor of the Atomic Theory, did not adopt the precise numbers given in the table, but others, which, however, bear a very simple relation to them.]
+------------+-----------+------------ Name. | Symbol. | Atomic | Atomic | | weight. | volume. --------------------+------------+-----------+------------ =ALUMINUM= | Al | 27·5 | ANTIMONY | Sb | 122 | ARSENIC | As | 75 | 1/4 BARIUM | Ba | 137 | BISMUTH | Bi | 208 | BORON | B | 11 | =BROMINE= | Br | 80 | 1 Cadmium | Cd | 112 | 2 Cæsium | Cs | 133 | =CALCIUM= | Ca | 40 | =CARBON= | C | 12 | Cerium | Ce | 92 | =CHLORINE= | Cl | 35·5 | 1 CHROMIUM | Cr | 52·5 | COBALT | Co | 58·8 | =COPPER= | Cu | 63·5 | Didymium | D | 96 | =FLUORINE= | F | 19 | 1 Glucinum | G | 14 | GOLD | Au | 196·7 | =HYDROGEN= | H | 1 | 1 Indium | In | 74 | =IODINE= | I | 127 | 1 IRIDIUM | Ir | 198 | =IRON= | Fe | 56 | Lanthanum | L | 92 | =LEAD= | Pb | 207 | Lithium | Li | 7 | MAGNESIUM | Mg | 24 | =MANGANESE= | Mn | 55 | =MERCURY= | Hg | 200 | 2 Molybdenum | Mo | 92 | NICKEL | Ni | 58·8 | Niobium | Nb | 97·6 | =NITROGEN= | N | 14 | 1 Osmium | Os | 199 | =OXYGEN= | O | 16 | 1 PALLADIUM | Pd | 106·5 | =PHOSPHORUS= | P | 31 | 1/4 PLATINUM | Pt | 197·4 | =POTASSIUM= | K | 39 | RHODIUM | Rh | 104 | Rubidium | Rb | 85·5 | Ruthenium | Ru | 104 | Selenium | Se | 79 | 1 =SILICON= | Si | 28·5 | =SILVER= | Ag | 108 | =SODIUM= | Na | 23 | STRONTIUM | Sr | 87·5 | =SULPHUR= | S | 32 | 1 Tantalum | Ta | 137·5 | Tellurium | Te | 128 | Thallium | Tl | 204 | Thorium | Th | 231·5 | TIN | Sn | 118 | TITANIUM | Ti | 50 | TUNGSTEN | W | 184 | URANIUM | U | 120 | Vanadium | V | 51·2 | Yttrium | Y | 68 | =ZINC= | Zn | 65 | 2 Zirconium | Zr | 90 | --------------------+------------+-----------+------------
ATOMIC VOLUME. The volume or space occupied by the atomic weights of gases at a temperature of 60° F., and under a pressure of 30 inches of the barometer, compared with that occupied by one part by weight of hydrogen under the same conditions.
In the same table the most important elements are distinguished by the largest type, those next in importance by medium type, and those of rare occurrence, or of which we know but little, by the smallest type.
=ATOMIC WEIGHTS.= See ATOM.
=ATON'IC.= _Syn._ ATON'ICUS, L.; ATONIQUE, Fr.; ATONISCH, SCHLAFF, Ger. Weak; debilitated; deficient in tone or strength. In _pathology_, applied to diseases or conditions of the body (ATONIC DISEASES; ATONY) in which debility is the leading feature. In _pharmacology_, ATONICS are agents which relax or lower the tone of the system.
=AT'ONY.= _Syn._ ATO'NIA, L.; ATONIE, &c., Fr., Ger. In _pathology_, loss of tone, relaxation, morbid diminution of vital energy or power; commonly applied to debility of any kind.
=AT'ROPHY= (-fe). _Syn._ ATRO'PHIA, L.; ATROPHIÉ, &c., Fr.; ATROPHIE, Ger. In _pathology_, wasting or emaciation, with loss of strength, and unaccompanied by fever or other sensible cause; defective nutrition; decline.
_Classif., Causes, &c._ It is either local, as in the case of a limb which is small, imperfectly developed, or withered; or general, affecting the whole body. GEN'ERAL ATROPHY appears to depend on deficient nutrition, arising from a want of due balance between the functions of assimilation and absorption, or from profuse evacuations draining off the materials necessary for the support of the body. In the former case only may it be regarded as an independent disease. LO'CAL ATROPHY commonly arises from some cause which lessens the normal circulation of blood in the part; or from a diminution of the nervous influence, as in paralysis. General atrophy is most frequent in infancy, childhood, and old age. In the first two it may be often traced to bad nursing, worms, or a scrofulous taint; and not unfrequently to continually inhaling impure or damp air. In adults, the causes are impaired digestion and imperfect action of the chyliferous organs, and sometimes diseased action of the liver. In many cases it results from the use of tobacco.
_Treatm._ This consists in a close attention to diet (which should be liberal and nutritious), exercise, clothing, ventilation, warmth, &c., with gentle stimulants, and chalybeate tonics where not contra-indicated; and, in the case of adults, the moderate use of pure generous wine or malt-liquor. Among special remedies, both in this disease and anæmia, may be mentioned pure sweet cod-liver oil, which seldom fails to arrest or greatly retard the progress of the disease, and in very many cases effect an entire cure. When this affection is symptomatic of any other disease, as worms, stomach or liver complaints, &c., the removal of the latter must of course be first attempted. See ANÆMIA, CHLOROSIS, TABES, &c.
=ATRO''PIA= (tr[=o]pe'y'[)a]). C_{34}H_{23}NO_{6}. [L.; B. P.] _Syn._ AT'ROPINE (-pin; sometimes atro'p[)i]ne[double-dagger]), Eng., Fr.; ATROPI'NA, ATRO''PIUM*, L. An alkaloid discovered by Brandes in _at'ropa belladon'na_ or deadly nightshade.
_Prep._ 1. (B. P. Process.) Take of belladonna-root, recently dried, and in coarse powder, 2 _lbs._; rectified spirit, 10 _pints_; slaked lime, 1 _oz._; diluted sulphuric acid, carbonate of potash, of each a sufficiency; chloroform, 3 _fl. oz._; purified animal charcoal, a sufficiency; distilled water, 10 _fl. oz._ Macerate the root in 4 pints of the spirit, for 24 hours, with frequent stirring. Transfer to a displacement apparatus, and exhaust the root with the remainder of the spirit by slow percolation. Add the lime to the tincture placed in a bottle, and shake them occasionally several times. Filter, add the diluted sulphuric acid in very feeble excess to the filtrate, and filter again. Distil off three fourths of the spirit, add to the residue the distilled water, evaporate at a gentle heat, but as rapidly as possible, until the liquor is reduced to one third of its volume and no longer smells of alcohol; then let it cool. Add very cautiously, with constant stirring, a solution of carbonate of potash so as nearly to neutralise the acid, care, however, being taken that an excess is not used. Set to rest for six hours, then filter, and add carbonate of potash in such quantity that the liquid shall acquire a decided alkaline reaction. Place in a bottle with the chloroform; mix well by frequently repeated brisk agitation, and pour the mixed liquids into a funnel furnished with a glass stop-cock. When the chloroform has subsided, draw it off by the stop-cock, and distil it on a water-bath from a retort connected with a condenser. Dissolve the residue in warm rectified spirit; digest the solution with a little animal charcoal: filter, evaporate, and cool until colourless crystals are obtained.
2. Expressed juice of belladonna is evaporated over a water-bath to the consistence of an extract, and then triturated in a marble or porcelain mortar with a strong solution of caustic potassa; the resulting mass is digested and well agitated for some time, at the temperature of 75° to 80° Fahr., with benzole, q. s.; and, after repose, the benzole-solution is carefully separated, and its volatile hydrocarbon is distilled off by the heat of a water-bath; the residuum in the retort is now exhausted with water acidulated with sulphuric acid, and the resulting 'acid-solution,' after filtration, precipitated with carbonate of soda; the precipitate is crude ATROPIA, which is collected on a filter, pressed between folds of bibulous paper, and dried; after which it is purified by one or more re-solutions, in alcohol, and crystallisations, which may or may not be modified in the manner noticed. The proportion of potassa should be about 1 dr. to every quart of the expressed juice. An excellent and economical process. The product is 0·3 to 4% of the weight of the plant from which the juice has been obtained.
3. (Mein and Liebig.) Belladonna-root (fresh-dried and coarsely powdered) is exhausted by alcohol (sp. gr. 0·822); slaked lime (1 part for every 24 of the dried root employed) is then added to the tincture, and the whole digested, with agitation, for 24 hours; sulphuric acid is next added, drop by drop, to slight excess, and, after filtration, rather more than one half the spirit is removed by distillation; a little water is now added to the residue, and the remainder of the alcohol evaporated as quickly as possible by a gentle heat; after again filtering, the liquid is reduced by further evaporation to the 1/12th part of the weight of the root employed, and a concentrated solution of potassa dropped into the cold liquid (to throw down a dark greyish-brown matter), carefully avoiding excess or rendering the liquid in the slightest degree alkaline; in a few hours the liquid is again filtered, and carbonate of potassa added as long as a precipitate (ATROPIA) falls; after a further interval of from 12 to 24 hours, this precipitate is collected and drained in a filter, and after pressure between folds of blotting-paper, dried by a very gentle heat. It is purified by making it into a paste with water, again squeezing it between the folds of blotting-paper, drying it, re-dissolving it in 5 times its weight of alcohol, decolouring it with pure animal charcoal, distilling off greater part of the alcohol, and evaporation and crystallisation by a very gentle heat; or only about one half the spirit is distilled off, and 3 or 4 times its volume of water gradually agitated with it, the resulting milky liquid being then heated to boiling, and allowed to cool very slowly, when nearly the whole of the ATROPIA crystallises out after a few hours. The same may be effected by at once agitating 6 or 8 volumes of water with the alcoholic solution, and setting aside the mixture for 12 to 24 hours, by which time the crystallisation will be completed. This process originated with Soubeiran, was improved by Mein, and subsequently, with slight modifications, adopted by Liebig. The product is about 0·3% of the weight of root operated on.
4. (Bouchardat and Cooper.) The filtered tincture is precipitated with iodine dissolved in an aqueous solution of iodide of potassium, the resulting ioduretted hydriodate of atropia, decomposed by zinc-and-water, the metallic oxide separated by means of carbonate of potassa, and the alkaloid thus obtained dissolved in alcohol and crystallised.
5. (Mr Luxton.) The dry leaves of belladonna are gently boiled for 2 hours in distilled water just sufficient to cover them, and the resulting decoction is strained through a coarse cloth into a large precipitating jar; this process is repeated with a second quantity of distilled water, and the two decoctions mixed; concentrated sulphuric acid is now added in the proportion of 2 dr. to every pound of leaves operated on, by which the vegetable albumen of the decoction is precipitated, and the liquid becomes clear and sherry-coloured; the clear liquor is now decanted or syphoned off, and, if necessary, filtered; the filtrate is now decomposed by either passing a stream of gaseous ammonia through it, or by suspending in it a lump of carbonate of ammonia. The effect is that the liquid turns black, and crystals of ATROPIA are slowly formed and deposited. At the expiration of a day or two, the supernatant mother-liquid is removed with a syphon, and the crystals thrown on a filter to drain and dry.[102] It may be purified by re-solution and crystallisation. 1 lb. of leaves yields 40 gr.; or at the rate of fully ·57%.
[Footnote 102: 'Pharm. Journ.,' 1854-5, p. 209{?}.]
6. (Rabourdin.) To the crystallised juice of the plant (previously heated to coagulate its albumen, filtered, and allowed to cool), 1 quart, is added of caustic potassa 1 dr., and afterwards of chloroform 1 oz.; the whole is then agitated well, and after half an hour's repose, the supernatant liquor is poured from the discoloured chloroform, which, after being washed with distilled water as long as it gives any colour to that liquid, is placed in a small retort, and the chloroform distilled off by the heat of a water-bath; the residuum is dissolved in a little water acidulated with sulphuric acid, and precipitated with carbonate of potassa, in slight excess; the precipitate is redissolved in alcohol, and the solution, by spontaneous evaporation, yields crystals of ATROPIA.
7. (Ure.) From the expressed juice of the fresh, or the watery extract of the dry plant, by treating it with caustic soda, in slight excess, and then agitating the mixture with 1-1/2 times its volume of ether; the ATROPIA taken up by the ether is again deposited after repose for some time, and is then purified by repeating the treatment with fresh ether as often as necessary.
8. Freshly precipitated hydrate of magnesia is added to the coagulated and filtered expressed juice, and the mixture evaporated to dryness, as quickly as possible, in a water-bath; the residuum is pulverised and digested in strong alcohol, and the clear liquid allowed to evaporate spontaneously. The crystals may be purified by repeated re-solutions in alcohol.
_Prop., Tests, &c._ The crystals obtained from hot concentrated solutions, colourless, transparent, silky prisms; from solutions in dilute spirit, silky needles, like those of disulphate of quinine. It is colourless; has a bitter, acrid, and somewhat metallic taste; dissolves in 200 parts (300 parts--Thomson) of cold and 50 to 54 parts of boiling water, in 1-1/2 parts of cold alcohol, and in 25 parts of cold, and 6 parts of boiling ether; it has an alkaline reaction, fuses at about 194° Fahr., is slightly volatile at common temperatures, and freely rises in vapour at 212° Fahr.; at higher temperatures it volatilises with partial decomposition; with the acids it forms salts, of which several are crystallisable.
_Tests._--1. Nitric acid forms with it a yellow solution:--2. With cold sulphuric acid it gives a colourless solution, which becomes red only when heated:--3. Aqueous solutions of atropia and its salts are--_a_, turned red by tincture of iodine--_b_, gives a citron-yellow precipitate with terchloride of gold--_c_, a flocculent whitish precipitate with tincture of galls, and--_d_, a yellowish-white one with bichloride of platinum:--4. Heated with caustic potassa or soda, it suffers decomposition, and ammonia is evolved:--5. A weak solution cautiously applied to the eyelid or conjunctiva, produces dilation of the pupil lasting for several hours.
_Pur., &c._ Alkaloid prepared from the root of atropa belladonna. Crystals; white, in the form of prisms; soluble in water and rectified spirit. It leaves no ash when burned with free access of air (B. P.).
_Phys. eff._ It is a very powerful narcotico-acrid poison.[103] Its effects are similar to those of belladonna, but considerably more powerful. "A very minute (imponderable) quantity applied to the eye is sufficient to dilate the pupil." (Pereira.) The 1/12 to 1/10 gr. often causes very serious effects in the human subject. The 1/6th of a grain accelerates the pulse, affects the brain, causes dryness of the throat, difficulty of deglutition, dilation of the pupil, dimness of sight, giddiness, strangury, numbness of limbs, sense of formication in the arms, rigidity of thighs, depression of pulse, and sometimes feebleness or loss of voice. These symptoms continue for from 12 to 24 hours. In larger doses death ensues.
[Footnote 103: A "cerebro-spinal poison."--Taylor.]
_Ant., &c._ These may be similar to those described under BELLADONNA and ALKALOID.
_Uses._ Chiefly as an external agent, as a substitute for belladonna, to cause dilation of the pupil; and as a local anæsthetic or anodyne, especially in facial neuralgia. Internally, it has been occasionally given in hooping-cough, chorea, and a few other nervous diseases.--_Dose_, 1/30 gr., gradually increased to 1/20, or, occasionally, even 1/15 gr. in solution, or made into a pill with liquorice powder and honey, or syrup, or used endermically; for a collyrium, 1 gr. to water 1 oz., a few drops only being applied to the eye at a time, the greatest caution in each case being observed. It is also employed to make the sulphate. In dispensing it a single drop of acetic acid, or dilute sulphuric acid, will be found to facilitate and ensure its perfect solution. See BELLADONNA and BELLADONINE.
=Atropia, Sul'phate of.= _Syn._ ATRO'PIA SUL'PHAS, L. _Prep._ (B. P.) Take of atropia, 120 _gr._; distilled water, 4 _fl. dr._; diluted sulphuric acid, a sufficiency.
Mix the atropia with the water and add the acid gradually, stirring them together until the alkaloid is dissolved and the solution is neutral. Evaporate it to dryness at a temperature not exceeding 100°.
_Characters and Tests._--A colourless powder, soluble in water, forming a solution which is neutral to test-paper, and when applied to the eye dilates the pupil as the solution of atropia does. It leaves no ash when burned with free access of air.
Intended for external application. It is a powerful poison.
_Uses, &c._ The same as those of the pure alkaloid.--_Dose_, 1/25 to 1/20 gr., either in solution or pills; 1 to 3 gr. to water 1 fl. oz., as a collyrium, of which a few drops seldom fail to produce full dilation of the pupil in about a quarter of an hour; 1 to 2 gr. to lard 1 dr. forms an excellent ointment in neuralgic affections.
_Obs._ Sulphate of atropia (which is intended for external use only) is rather difficult to crystallise, as it has a tendency to assume an amorphous or gum-like condition. It is more soluble than the pure alkaloid; and, like it, is a terrific poison.
=ATROPIA, VALERIANATÈ.= The Paris Codex directs this salt to be prepared as follows:--Dissolve valerianic acid in ether, and add atropia just sufficient to saturate the acid. Let the ether evaporate.
=ATROP'IC ACID.= _Syn._ ACIDUM ATROP'ICUM, L. The name given by Richter to a volatile crystallisable substance, possessing acid properties, found in atropa belladonna or deadly nightshade. In many respects it resembles benzoic acid, from which, however it is distinguished by not precipitating the salts of iron.
=ATROPI'NA, At'ropine.= See ATROPIA.