Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 204

The statistical report of the navy for 1871 offers a gratifying contrast to the above figures. From this doc.u.ment it appears that out of a total force of 4720 sailors, only four were affected with scurvy during that year. The much greater number of men attacked by the disease on board merchant ships appears to be due to the inferior or worthless character of the lime or lemon juice purchased by them.

Writing on the hygienic condition of the merchant marine in 1867, Mr Harry Leach says:--

"We are prepared to maintain, from the following table (and other statistics from which these have been taken), that the want of good lime or lemon juice was distinctly the cause of scurvy in the vessels below mentioned.

No. of Hands Cases of Result of examination Name of Ship. (all told). Scurvy. of Lime juice.

Hermione 17 5 Sulphuric acid.

Merrie England 29 10 Stinking.

Stirling Castle 32 6 Very weak.

Hoang-Ho 21 5 Acetic acid.

Blanche Moore 35 8 Musty and nauseous.

St Andrew's Castle 19 7 Citric acid.

Tamerlane 21 4 Nauseous.

Marlborough 23 8 Very weak.

Galloway 29 6 Short allowance.

Tamar 17 2 Very weak.

French Empire 27 7 or 8 Citric acid.

Eaglet 14 3 Thick and nasty.

Geelong 14 9 Taken irregularly.

Thorndean 35 2 Spoiled (short supply of provisions).

Taken with ships that, with others, have arrived in the port of London during the past two years with cases of scurvy.

"Of direct causes this is undoubtedly first and foremost; but of indirect causes we have a few words to say. Dirt, bad provisions, and any form of disease to which sailors, in common with other men, are subject, will predispose to scurvy. This cannot and should not be denied, but it affords to parsimonious captains a very large peg whereon to hang sundry invectives as to the cry lately made about the continued prevalence of this disease in the mercantile marine. Such captains, with pardonable ignorance, consider scurvy a form of venereal disease, give the wretched subject thereof mercury, and bring him into port salivated as well as s...o...b..tic."

Mr Leach further adds:--

"In summing up statistics of scurvy for the past year (1867), we find that a total of 235 accredited cases were admitted into British hospitals, giving no account of those who convalesced in sailors' homes or elsewhere.

"To this we may add, that seven sailors were left at St Helena, from a ship recently arrived in the Thames; that a vessel put into Falmouth on the 29th ult., with no less than sixteen severe cases of scurvy on board, and that between twenty and thirty cases have arrived in this port during the present month. It would be well (as a supplementary aid to the prevention of scurvy by inspection of lime juice) that the dues levied for the St Helena Hospital should be abolished. It was stated to us some weeks ago by a very old inhabitant of that Island, that this fact alone caused many ships to pa.s.s without calling for needful supplies of antis...o...b..tic material.

"I would however remark, that if the system proposed by the Seamen's Hospital Society were put in force, no such aid to the prevention of this disease would be required, inasmuch as every ship would then be supplied with good lime juice."

The following figures, giving the number of patients suffering from scurvy admitted into the Seamen's Hospital, shows a decrease in the disease, since the publication of the above:--

In 1865, from British vessels, 101; foreign do. 1 " 1866 " " 96 " 5 " 1867 " " 90 " 4 " 1868 " " 64 " 10 " 1869 " " 31 " 9 " 1870 " " 30 " 21 " 1871 " " 24 " 16

=SEAL'ING WAX.= See WAX.

=SEA SICKNESS.= The most effectual preventive of sea sickness appears to be the horizontal position. When there is much pain, after the stomach has been well cleared, a few drops of laudanum may be taken, or an opium plaster may be applied over the region of the stomach. Persons about to proceed to sea should put their stomach and bowels in proper order, by the use of mild aperients, and even an emetic, if required, when it will generally be found that a gla.s.s of warm and weak brandy-and-water, to which 15 or 20 drops of laudanum, or, still better, 1 or 2 drops of creasote, have been added, will effectually prevent any disposition to sea sickness, provided the bowels be attended to, and excess in eating and drinking be at the same time avoided. A spoonful of crushed ice, in a wine-gla.s.sful of cold water, or weak brandy-and-water, will often afford relief when all other means fail. Smoking at sea is very apt to induce sickness. M. F. Curie, in the 'Comptes Rendus,' a.s.serts that drawing in the breath as the vessel descends, and exhaling it as it ascends, on the billows, by preventing the movements of the diaphragm acting abnormally on the phrenetic nerves, prevents sea sickness. On this Mr Atkinson, at one of the meetings of the British a.s.sociation, observed that--if a person, seated on board ship, holding a tumbler filled with water in his hand, makes an effort to prevent the water running over, at the same time allowing not merely his arm, but also his whole body, to partic.i.p.ate in the movements, he will find that this has the effect of preventing the giddiness and nausea that the rolling and tossing of the vessel have a tendency to produce in inexperienced voyagers. If the person is suffering from sickness at the commencement of his experiment, as soon as he grasps the gla.s.s of liquid in his hand, and suffers his arm to take its course and go through the movements alluded to, he feels as if he were performing them of his own free will, and the nausea abates immediately, and very soon ceases entirely, and does not return so long as he suffers his arm and body to a.s.sume the postures into which they seem to be drawn. Should he, however, resist the free course of his hand, he instantly feels a thrill of pain, of a peculiarly stunning kind, shoot through his head, and experiences a sense of dizziness and returning nausea.

Dr Doring, a Viennese physician, states that an ordinary dose of chloral hydrate is an unfailing remedy for sea sickness. In various cases recorded by him it seems to have been of the greatest service, even during long sea voyages, ensuring a good night's rest, arresting violent sickness when it has set in, and preventing its return.

=SEDATIVE PILLS, Gunther's.= These are composed of the following ingredients:--a.s.saftida powder, 50 parts; extract of valerian, 50; extract of belladonna, 3; oxide of zinc, 1 part; castor, 2 parts. Make into a pill-ma.s.s, to be administered in doses of 3 to 10 grains, twice daily, in ch.o.r.ea, &c.

=SED'ATIVES.= _Syn._ SEDATIVA, L. Medicines and agents which diminish the force of the circulation or the animal energy, and allay pain. Foxglove, henbane, tobacco, pota.s.sio-tartrate of antimony, and several of the neutral salts and acids, act as sedatives. Cold is, perhaps, the most powerful agent of this cla.s.s.

=SEED.= _Syn._ s.e.m.e.n, L. The seeds of plants are conspicuous for their vast number and variety, and their extreme usefulness to man. The seeds of certain of the _Graminaceae_ furnish him with his daily bread; some of those of the _Leguminosae_ in either the immature or ripe state, supply his table with wholesome esculents, or provide a nourishing diet for his domestic animals; whilst those of numerous other plants, dispersed through every cla.s.s, orders, and family, yield their treasures of oil, medicinals, or perfumes for his use.

=SELEN'IC ACID.= H_{2}SeO_{4}. _Syn._ ACIDUM SELENIc.u.m, L. _Prep._ By fusing selenium with nitrate of pota.s.sium or of sodium, acting on the fused ma.s.s with water, precipitating the resulting solution with acetate or nitrate of lead, and decomposing the precipitate (selenate of lead), diffused in water, with sulphuretted hydrogen. The selenic acid, thus obtained, may be cautiously concentrated in a gla.s.s vessel, if necessary; but if this be pushed too far, it is resolved into selenious acid (H_{2}SeO_{3}) and oxygen.

_Prop., &c._ Hydrated selenic acid is a colourless liquid, closely resembling sulphuric acid; its salts (selenates) bear the closest a.n.a.logy to the sulphates.

SELENIC ACID (H_{2}SeO_{4}). No selenic anhydride is known. Selenic acid may be obtained in solution by deflagrating selenium or a selenite with pota.s.sic nitrate. The residue dissolved in water is mixed with a solution of plumbic nitrate, an insoluble plumbic seleniate being precipitated. The plumbic seleniate is suspended in water and decomposed by means of a current of sulphuretted hydrogen. Plumbic sulphide is precipitated, and the liberated selenic acid separated by filtration is concentrated until it acquires a sp. gr. of 26; if heated above 554 F. it decomposes into selenious anhydride, water, and oxygen. Selenic acid has a great resemblance to sulphuric acid. It acts upon the metals in the same manner, and even dissolves gold. The seleniates are also very similar in properties to the sulphates, and both cla.s.ses of salts are isomorphous.

The seleniates give the same characteristic odour before the blowpipe as the selenites. Their solutions give white precipitates with the salts of barium, strontian and lead, insoluble in nitric acid. If a soluble seleniate is boiled with hydrochloric acid, selenic acid is set free, and is reduced to selenious acid, sulphurous acid will then precipitate reduced selenium from the solution. Baric seleniate may be also decomposed in a similar manner, and this reaction distinguishes it from baric sulphate.

=SELE'NIUM.= Se. A rare chemical element, discovered by Berzelius in 1817 in the refuse of a sulphuric acid manufactory near Fahlun, in Sweden, it having been derived from the pyrites employed in the manufacture of the acid. Hence the pyrites of Fahlun forms the chief source of this rare body, although it exists, but less abundantly, in combination with a few other metals, termed selenides. Selenium is chiefly interesting to the chemist from its remarkable a.n.a.logy in chemical properties to sulphur.

Like this latter element, it is capable of a.s.suming three allotropic forms--the amorphous, the vitreous, and the crystalline.

The latter variety of selenium, like the crystalline form of sulphur, dissolves in bisulphide of carbon, but much less readily. Selenium boils below a red heat and becomes converted into a deep yellow vapour, which, when heated, is subject to the same anomalous expansion as sulphur vapour.

It is not so combustible as sulphur, which it still further resembles by burning with a blue flame when ignited in the air. During combustion it gives off a peculiar and characteristic smell, resembling that of putrid horse-radish. Heated with strong sulphuric acid, selenium forms a green solution. If this solution is poured into water, the selenium separates and is thrown down. Selenium is without taste or smell, is insoluble in water, and in its normal state is a non-conductor of heat and electricity.

Selenium may be extracted from the Fahlun residue by the following process:--It should be first boiled with sulphuric acid, diluted with an equal volume of water, and nitric acid should then be added in small quant.i.ties until the oxidation of the selenium is accomplished, which may be known when red fumes cease to be cooled. The solution which contains selenious (SeO_{2}) and selenic (SeO_{3}) acid is then to be largely diluted with water, filtered, the filtrate mixed with about one fourth of its bulk of hydrochloric acid, and then concentrated a little by evaporation, the result of which is that the hydrochloric acid reduces the selenic to selenious acid. A current of sulphurous acid being then pa.s.sed through the solution, the selenium is precipitated in red flakes, which form into a dense black ma.s.s when the liquid is gently heated. The following equation ill.u.s.trates the reaction:--

H_{2}O,SeO_{2} + H_{2}O + 2SO_{2} = 2(H_{2}SO_{3}) + Se.

Like sulphur, selenium combines with oxygen and forms an anhydride corresponding to sulphurous anhydride. SELENIOUS ANHYDRIDE (SeO_{2}) may be obtained by burning selenium in a current of oxygen; it is, however, more easily prepared by boiling selenium with nitric acid or with aqua regia, the excess of acid being expelled by heat, the selenious anhydride is left as a white ma.s.s. When this is dissolved in water it yields a crystalline hydrate of selenious acid (H_{2}SeO_{3}). The salts formed by selenious acid (selenites), with the exception of those of the alkali metals, are mostly insoluble in water. They are easily known by the peculiar odour of selenium which they give off when heated on charcoal in the reducing flame of the blowpipe; solutions of the selenites give a reddish-brown precipitate when treated with sulphurous acid.

=Seleniuretted Hydrogen= (H_{2}Se). This may be obtained in a precisely similar manner, namely, by acting on selenide of iron or pota.s.sium with diluted sulphuric or hydrochloric acid. Seleniuretted hydrogen is soluble in water, and precipitates many metals from their salts as selenides. The solution is feebly acid, and, like its a.n.a.logue solution of sulphuretted hydrogen, if exposed to the air, absorbs oxygen and deposits selenium. The selenides of the alkali metals are soluble in water. The selenides of cerium, zinc, and manganese are flesh-coloured; most of the others are black. This gas is inflammable like sulphuretted hydrogen; it has, however, a still more offensive smell than this latter gas, Berzelius lost his sense of smell for several hours by the application to his nose of a bubble of seleniuretted hydrogen not larger than a pea. There are two chlorides of selenium--a dichloride (Se_{2}Cl_{2}), a volatile liquid of a brown colour, and a tetra-chloride (SeCl_{4}), which occurs as a white crystalline solid. Selenium unites with sulphur, forming a bisulphide (SeS_{2}) and a tersulphide (SeS_{3}). A very curious physical property of selenium when exposed to the action of light was first noticed in 1873 by Mr May, a.s.sistant chemist at the Telegraph Station at Valentia, in Ireland, who observed that a stick of crystallised selenium which had been used for some time in telegraphy, where high electrical resistance was required, offered a considerably diminished resistance to the current when exposed to the light than when kept in the dark. Mr May's discovery, which was at first received with some amount of incredulity, has since been amply corroborated by the observations and researches of many physicists, amongst them by Professor Werner Siemens, the result of whose experiments on this interesting subject we quote from a lecture delivered at the Royal Inst.i.tution by his brother, Dr William Siemens, in February, 1876. After describing the method by which his brother arranged the selenium, so that, when inserted in the galvanic current of a single Daniell's cell, the surface action produced by the light upon it attained a maximum effect, and thereby did away with the necessity of employing a large galvanic battery, and at the same time allowed an ordinary galvanometer to be used instead of a delicate one, as. .h.i.therto employed, Dr Siemens proceeded to ill.u.s.trate the action of light upon the element by experiment. "I here hold," he said, "an element so prepared of amorphous selenium, which I place in a dark box, and insert in a galvanic circuit comprising a Daniell's cell and a delicate galvanometer, the face of which will be thrown upon the screen through a mirror by means of the electric light.

"In closing the circuit it will be seen that no deflection of the needle ensues. We will now admit light upon the selenium disc and close the circuit, when again no deflection will be observed, showing that the selenium in its present condition is a non-conductor both in the dark and under the influence of light. I will now submit a similar disc of selenium which has been kept in boiling water for an hour and gradually cooled to the same tests as before. In closing the circuit while the plate is in the dark a certain deflection of the galvanometer will be discernible, but I will now open the lid of the box so as to admit light upon the disc, when on again closing the circuit a slight deflection of the galvanometer needle will be observed. In closing the box against the light this deflection will subside, but will again be visible the moment the light is readmitted to the box. Here we have, then, the extraordinary effect of light upon selenium clearly ill.u.s.trated.

"I will now insert into the same circuit another selenium plate which has been heated up to 210 C, and, after having been kept at that temperature for several hours, has been gradually cooled; it will be observed that this plate is affected to a greater extent than the former by the action of light, and other conditions, to which I shall presently allude, prove the selenium heated to a higher temperature to be in other respects dissimilar to the other two modifications of the same. These differences will be best revealed in describing my brother's experiment. He placed one of his amorphous preparations of selenium in an air-bath heated above the melting point of selenium (to 260 C.), while the connecting wires were inserted in a galvanic circuit consisting of only one Daniell's element and a delicate reflecting galvanometer, and every five minutes the temperature and conductivity of the selenium were noted. Up to the temperature of 80 C. no current pa.s.sed; from this point onward the conductivity of the material rapidly increased until it obtained its maximum at the temperature of 210 C., being nearly its melting point, after which an equally rapid diminution of conductivity commenced, reaching a minimum at a temperature of about 240 C., when the conductivity was only such as could be detected by a most delicate galvanometer. In continuing to increase the temperature of the fluid selenium very gradually but steadily, its conductivity increased again.

The interpretation of these experiments is as follows: Amorphous selenium retains a very large amount of specific heat, which renders it a non-conductor of electricity: when heated to 80 this amorphous solid ma.s.s begins to change its amorphous condition for the crystalline form, in which form it possesses a greatly reduced amount of specific heat, giving rise to the increase of temperature beyond that of surrounding objects when the change of condition is once set in. If care is taken to limit the rise of temperature of the selenium to 100 C., and if it is very gradually cooled after being maintained for an hour or two at that temperature, a ma.s.s is obtained which conducts electricity to some extent, and which shows increased conductivity under the influence of light. But in examining the conductivity of selenium so prepared at various temperatures below 80, and without accession of light, it was found that its _conductivity increases with rise of temperature_, in which respect it resembles carbon, sulphide of metals, and generally electrolytes. This my brother terms his first modification of selenium.

But in extending the heating influence up to 210, and in maintaining that temperature by means of a bath of paraffin for some hours before gradually reducing the same, he obtained a second modification of selenium, in which its conductivity increases with fall of temperature, and in which modification it is, therefore, a.n.a.logous to the metals. This second modification of selenium is a better conductor of electricity than the first, and its sensitiveness to light is so great that its conductivity in sunlight is fifteen times greater than it is in the dark, as will be seen from the following table, in which is given the effects of different intensities of light on selenium (Modification II) obtained at Woolwich on the 14th of February, 1876:--

--------------------------------------------------------------- Selenium in Relative Conductivities. Resistance in ------------------------- Ohms.

Deflections. Ratio. --------------------------------------------------------------- 1. Dark 32 10 10,070,000 2. Diffused daylight. 110 34 2,930,000 3. Lamplight 180 56 1,790,000 4. Sunlight 470 147 680,000 ---------------------------------------------------------------

Unfortunately, however, the second modification is not so stable as the first; when lowered in temperature parts of it change back into the first or metalloid modification by taking up specific heat, and in watching this effect a point is discovered at which ratio of increase of conductivity with fall of temperature changes sign, or where the electrolyte substance appears to predominate over the metallic selenium. If cooled down to 15 C., the whole of the metallic selenium is gradually being converted back into the first variety. The physical conclusions here arrived at may be said to be an extension of Helmholtz's theory that the conductivity of metals varies inversely as the total heat contained in them. Helmholtz had only the sensible heat of temperature (counting from the absolute zero point) in view, but it has already been shown by Hittorf and Werner Siemens that it applies in the case of tin and some other metals, also to specific heat and to the latent heat of fusion. In selenium the specific heat is an extremely variable quant.i.ty, changing in the solid ma.s.s at certain temperatures, and, it is contended, under the influence of light.

Aided by these experimental researches, my brother arrives at the conclusion that the influence of light upon selenium may be explained by a "_change of its molecular condition near the surface, from the first or electrolyte into the second or metallic modification_, or in other words, by a _liberation of specific heat upon the illuminated surface of crystalline selenium_, which liberated heat is reabsorbed when the liberating cause has ceased to act." Professor Adams, who has likewise investigated this singular action of light upon selenium, ascribes it to a different cause. He says:--

1. That the light falling on the selenium causes an electromotive force in it in the same direction as the battery current pa.s.sing through it, the effect being similar to the effect due to polarisation in an electrolyte, but in the opposite direction.

2. That the light falling on the selenium causes a change on its surface akin to the change which it produces on the surface of a phosph.o.r.escent body, and that in consequence of this change the electro-current is enabled to pa.s.s more readily over the surface of the selenium.

=SEM'OLA (Bullock's).= This preparation consists of wheaten flour deprived of much of its starch by washings with water, and contains the largest amount (48 per cent.) of nitrogenous or alb.u.menoid principles consistent with its adaptability to culinary purposes. It is specially intended as a food for infants, weakly children, and invalids.

=SEMOLI'NA.= _Syn._ SeMOULE, SEMOULINA. The large hard grains of wheat flour retained in the bolting machine, after the fine flour has pa.s.sed through its meshes. "The best semoule is obtained from the wheat of the southern parts of Europe. With the semoule the fine white Parisian bread called '_gruau_' is baked." (Ure.)

=SEN'EGA.= _Syn._ SENEKA, SNAKEROOT, RATTLESNAKE R.; SENEGae RADIX (B. P.); SENEGA (Ph. L., E., & D.), RADIX SENEGae, L. "The root of the _Polygala Senega_, Linn." (Ph. L.) A stimulating diaph.o.r.etic, and expectorant; in large doses diuretic, cathartic, and emetic. In America it is used as an antidote to the bite of the rattlesnake. Drs Chapman and Hartshorne extol it as an emmenagogue. Dr Pereira says that it is an exceedingly valuable remedy in the latter stages of bronchial or pulmonary inflammation, when this disease occurs in aged, debilitated, or torpid const.i.tutions.--_Dose_, 10 to 30 gr., in powder or decoction (combined with aromatics, opium, or camphor), thrice daily.

According to Patrouillard senega is occasionally adulterated with the roots of _Asclepias vincetoxic.u.m_. The branches of the latter root are cylindrical, very white, and almost devoid of taste; those of senega, on the contrary, are yellowish and twisted, and have a very acrid taste. The froth produced by shaking an infusion of senega keeps much longer than that produced by an infusion of the adulterant. In other respects there is a great resemblance between the two roots.

=SEN'EGIN.= _Syn._ POLYGALIN, POLYGALIC ACID. A white odourless powder, discovered by Gehlin in the bark of seneka root (_Polygala Senega_).