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CHEMISTRY.-No. XV.

ACIDS. NO. II.

PHOSPHORIC ACID is a compound of oxygen and phosphorus, in the proportion of 20 parts of oxygen, to 15 71 of phosphorus. It was formerly produced by burning phosphorus in oxygen gas, but it is now chiefly obtained from animal bones. When pure, it is formed in white and snowy flakes; but when exposed to the air, it attracts the aqueous vapour, and becomes a dense fluid. The phosphorus acid contains a smaller proportion of oxygen than the phosphoric, and may be produced by the slow combustion of phosphorus in oxygen gas. These acids have not been applied to any important use.

MURIATIC ACID is obtained from sea salt, and is a combination of chlorine and hydrogen. It has a yellowish colour, and emits white fumes of a disagreeable and suffocating smell. It is one of the most corrosive of all the acids, and has a very strong affinity for water and silver. It is generally employed as a test for silver, and however small may be the quantity of silver held in solution, it will be instantly detected by a drop of muriatic acid. This acid is extensively used in the arts, and it may be worthy of notice, that in a diluted state it may be employed for removing ink stains from books without affecting the print.

FLUORIC ACID is a compound of fluorine and hydrogen,and is obtained from a mineral substance called fluor-spar. Its smell has a great resemblance to that of muriatic acid. A remarkable and distinctive property of this acid is its power of corroding silica, and thus destroying the transparency of glass, and it is consequently used for etching on this substance.

BORACIC ACID is composed of boron and oxygen, in the proportion of one part of the former to two parts of the latter. The taste of this acid is at first sour, then bitter, and at last it leaves a sweet flavour on the palate. When united with sulphuric acid, it emits a smell greatly resembling musk. It is obtained in the form of thin scales, and combines with the alkalies, and with some of the earths and metallic oxides. It gives to turmeric paper a brown colour, similar to that produced by the alkalies, but it reddens litmus paper, and gives a green colour to flame. ARSENIC ACID was discovered by Scheele, and consists of arsenic and oxygen. It is a white heavy substance, obtained by dissolving common white arsenic (arsenious acid) in concentric nitric

acid, with a small quantity of muriatic, and distilling the solution to dryness. It is a remarkably active poison.

TUNGSTIC ACID, a compound of tungsten and oxygen, is a tasteless yellow powder, insoluble in water, and is found native in a mineral called wolfram. It dissolves several of the metals.

MOLYBDIC, CHROMIC, and TELLURIC ACIDS, are composed of molybdenum, chromium, and tellurium with oxygen, and belong to the class of acids we have been examining; but they do not possess any useful properties, and need not therefore be described.

The acids belonging to the second class are chiefly of vegetable origin, and contain more than two elementary substances, which are commonly oxygen, hydrogen, and carbon, and occasionally a portion of nitrogen.

When saccharine liquors have passed from the first or vinous fermentation to the second or acetous fermentation, an acid may be obtained from them, called the acetic acid. Vinegar is a diluted acetic acid, but when pure and concentrated it is colourless, has a pungent and acrid taste, and is of a volatile and corrosive nature. Pyroligneous acid is a substance possessed of the same properties, and is produced by the destructive distillation of vegetable matter. It is, however, extremely impure, being combined with tar, and a nauseous empyreumatic vegetable oil, though it may be purified and used as a substitute for vinegar. acetic acid consists of twenty-four parts of carbon, twenty-four of oxygen, and three of hydrogen.

Pure

OXALIC ACID is composed of twentyfour parts of oxygen with twelve of carbon, and is found in the juice of sorrel and in the roots of rhubarb. It may also be obtained from sugar, and has hence been sometimes called acid of sugar. It is an extremely active poison, and produces almost instantaneous death. It is extensively used by calico-printers, and is often employed to detect the presence of lime, for which substance it has a greater affinity than any other acid. If a few drops of the solution of oxalic acid be dropped into a neutral solution of muriate of lime, a precipitate will be immediately formed, which is the oxalate of lime. But it is always necessary that there should not be an excess of muriatic acid, for the lime would then be re-dissolved. If a person has taken oxalic acid into the stomach, powdered chalk, or magnesia in water, should

be immediately administered in large doses, and the operation of the poison may thus be generally prevented.

NEGROES AND PEOPLE OF COLOUR.

disadvantages, which are sufficient to raise expectation for the future, and to remove every idea of their natural inferiority to the white man.

INSECTS.-No. XXXIX.

(Taste.)

TASTE is absolutely necessary to the continuance of animal existence. In cattle, and animals which feed on green herbs, the tongue is both large and studded with large papillæ or tasters, abundantly moistened with saliva, and also with a peculiar mucus. In herbivorous animals this arrangement is peculiarly necessary, for the variety of herbs is so great, and they often grow so promiscuously together, that had not cattle a great acuteness of taste, they might soon be poisoned. This, however, very rarely happens.

A LETTER dated, some months ago, Ann Harbour, Michigan, from Mr. Metzgar, a Lutheran clergyman, gives an account of the disrespectful conduct of the Americans towards Mrs. Metzgar, simply because the colour of her skin was less fair than their eye had been accustomed to. The perusal of this drew my attention to a statement made by Sir Everard Home, some years ago, on the utility of the black substance in the skin of the negro, in preventing the scorching operation of the sun's rays; and as we know that nothing tends more to the removal of prejudice, than the rectification of the judgment upon those points upon which it may have been warped by false impressions, it is possible that some might be induced to look with respect and benevolence upon those they have hitherto slighted, when they con sider that the very colour which has awakened contrary dispositions, is an in-pharynx or swallow; and on its lower side, dication of the peculiar care of our heavenly Father over this portion of our fellow

creatures.

Some time ago, Sir Everard Home, at a meeting of the Royal Society, showed that by exposing the back of the hand or other parts of the body to the sun's rays, they become irritated and inflamed; small specks or freckles first appear, and these on continual exposure rise into blisters. The same is true, if the flesh be covered with thin white linen; but if the body be covered with a piece of black crape, though it will be hotter when exposed to the sun, yet the rays will no longer produce blisters. Thus the injurious effect of the heat of the sun may be prevented by an artificial blackening of the skin. How strongly does this show that the black man, though too often contemptuously treated by his fellow creatures, is not beneath the notice of his Creator; rather may we consider him as continually carrying about with him, in the colour of his skin, the memento of his heavenly Father's mercy.

The depressed and degrading circumstances to which negroes and people of colour have hitherto been subjected, have been very unfavourable to the developement of their moral and intellectual character; but many instances of talent and piety have appeared, notwithstanding these

The tongue of insects lies between the two lips, the labrum and labium. On its upper side, at the base, it meets the palate or roof of the mouth, below which it is attached, it may be presumed, by its roots to the crust of the head, on each side the

in many cases, it is attached to the labium, and that very closely, so as to appear to be merely a part of it, and to form its extremity; but in others it is more free, and in form somewhat resembling the tongue of quadrupeds. "When ants are disposed to drink," says M. P. Huber, "there comes out from between their lower jaws, which are much shorter than the upper, a minute, conical, fleshy, yellowish process, which performs the office of a tongue, being pushed out and drawn in alternately it appears to proceed from the lower lip. This lip has the power of moving itself forwards in conjunction with the lower jaws and when the insect wishes to lap, all this apparatus moves forward; so that the tongue, which is very short, does not require to lengthen itself much to reach the liquid." What a curious structure to meet the necessities and comfort of these little creatures!

Insects, it seems, are even nicer than cattle in their selection of food, and consequently in the acuteness of their taste. The caterpillar of the antler moth, (charcas graminis,) though it feeds on a variety of grasses, and sometimes ravages to so great an extent the meadows of Sweden, as to endanger the lives of the cattle for want of food, does not touch the fox-tail grass, though to us its leaves taste little, if at all

different from some of those it so greedily devours. Other creatures confine themselves to only one species of grass.

The bee-mite, though not very easily dislodged while the bee is alive, scampers off as soon as the bee dies, and even long before, when it becomes sickly from the irritation of the numbers by which it is infested. Whether this arises from their finding it more difficult to penetrate the skin, or from their not relishing the diseased fluids, we cannot tell; but the latter is the more probable reason, from the singular fact, that fleas and other parasitic insects never infest a person who is near death; a fact that has been so frequently observed, that it has become one of the popular signs of approaching dissolution.

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Perhaps," says the elder Huber, "the sense of taste is the least perfect of those enjoyed by bees; for, contrary to the received opinion, they display little choice in collecting honey; nor do they testify greater nicety in the quality of their water, for the most corrupted marshes and ditches seem to be preferred to the most limpid streams, nay, even to dew itself. Nothing, therefore, is more unequal than the quality of honey, the produce of one district differing from another, and the honey of spring being unlike that of autumn; while even the contents of one hive do not always resemble those of the one which is contiguous. But though bees are thus not very choice in their nutriment, and are by no means delicate in regard to the quality of honey, they are far from being indifferent with regard to the quantity. They soon discover, and consequently frequent, the places where most is to be found; and they quit their hive much less in regard to the fineness or temperature of the weather, than according to their prospect of a plentiful or a scanty collection. When the limetree and blackthorn blossom, they brave the rain, departing before sun-rise, and returning later than ordinary; but this activity soon relaxes; when the flowers begin to fade, and when the scythe has cut down the fields of clover, the bees are seldom tempted to go from their home by the most brilliant sunshine."

Man possesses salivary fountains for moistening his organs of taste, and an analogous structure is discoverable in insects. Thus a fly contrives to suck up through its narrow haustellum a bit of dry lump-sugar; and for this it seems unprepared, as the small crystals are not only unfitted to pass, from their angular form, but adhere too closely together to be separated by any

force the insect can exert. But when some sugar has been placed on the outside of a window, while observation has been carried forward through a magnifying glass in the inside, it has been seen that the fly lets fall a drop of fluid occasionally on the sugar, in order to melt it, and thereby render it fit to be sucked up, just as we moisten a mouthful of dry bread with saliva, to fit it for being swallowed.

Vessels which supply the saliva in more than one species of insects, seem to have been first observed by Swammerdam, in the small tortoise-shell butterfly, vanessa urticæ; but as he could not trace their termination, he says, with his usual scrupulous caution, "what the office of these vessels is, and whether they may not be the salivary ducts, I cannot take upon me to determine." Lyonnet afterwards discovered a conspicuous pair of these vessels in the caterpillar of the goat-moth, (cossus ligniperda,) distinct from the silk reservoirs, with which Swammerdam was inclined to confound them, and their existence has been placed beyond all doubt by Ramdohr, to whom we are indebted for the following interesting facts.

"The pipes which carry the saliva do not always open into the mouth, but sometimes into the gullet, as in a sort of bug, (pentatima,) and sometimes into the stomach itself, as in the bee-flies. It is remarkable that the latter insects, from feeding exclusively on the nectar of flowers, do not require a supply of saliva to moisten their food in the first instance, though it appears to be indispensable to digestion; while in bugs, which feed on vegetable and animal juices, one pipe opens into the sucker, to enable the animal to soften, if necessary, the skin it has to pierce through, and another into the stomach or gullet to aid digestion. In the common fly again, and the gad-fly, both pipes open into the sucker, and we have already seen the ingenious use which is made of this when the insect feeds on dry sugar. In the waterscorpion, there are no fewer than six of these vessels, though it is rare that there are more than two in other insects. It is wor.. thy of remark, that the exterior double pair in it is found, when highly magnified, to consist of little globules resembling a bunch of currants; and a similar structure has also been detected in one of the bee-flies, precisely like what occurs in our own salivary fountains."

Ants are very fond of water. One of them has been seen quaffing a drop of dew almost as large as its whole body; and

of the general welfare of the community as they are fatal to the happiness of individuals. Among others, the following effects may be distinctly traced:

The destruction of an immense amount of wholesome and nutritious grain, given by a bountiful Providence for the food of man, which is now converted by distillation into a poison; the highest medical authorities,

when those in glass formicaries have water given them, they seem quite insatiable in drinking it; a circumstance well shown in the following anecdote from Huber : "The feet," he says, "of my artificial formicary (abode of the ants) were plunged in vessels constantly filled with water. This, which was originally adopted to prevent the escape of the inmates, proved to them a fruitful source of enjoyment, by supply-examined in great numbers before your ing them with a plentiful beverage during Committee, being uniform in their testithe heats of summer. One day, while mony that ardent spirits are absolutely poithey were assembled at this fosse of the sonous to the human constitution; that in formicary, occupied in licking up the little no case whatever are they necessary, or drops which filtered between the fibres of even useful to persons in health; that they the wood, which they preferred to taking it are always in every case, and to the smallest from the basin itself, I amused myself in extent, deleterious, pernicious, or destrucdisturbing them, upon which the greater tive, according to the proportions in which number ascended; but a few remained, they may be taken into the system; so that whom my presence had not alarmed, and not only is an immense amount of human who continued carousing. One of those, food destroyed in such a manner as to inhowever, who had regained the nest, came jure greatly the agricultural producers themback, and approached another, apparently selves, for whose grain, but for this perquite absorbed in the pleasure of drinking. verted and mistaken use of it, there would It pushed the drinker with its mandibles be more than twice the present demand for several times successively, raising and low- the use of the now scanty-fed people, who ering its head alternately, and at length would then have healthy appetites to consucceeded in driving it off. The officious ant sume, and improved means to purchase then reached another similarly engaged, with nutriment for themselves and children, in whom it found no less difficulty; at length, grain as well as in all other varied producbeing persuaded of the necessity of with- tions of the earth. drawing, the drinker passed precipitately to the bell glass. A third, warned in the same manner and by the same ant, quickly regained the nest; but a fourth remained alone at the water's edge, and would not retire, nor pay any attention to the reiterated blows of its friendly monitor, who at length seized it by one of its legs and dragged it away rather roughly. The toper, however, returned, keeping his large mandibles extended with all the appearance of rage, and again stationed himself to quaff the delightful beverage; but its companion would give it no quarter, and, coming in front, it seized it, and dragged it by main force to

the nest.

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The loss of productive labour in every department of occupation to the extent of at least one day in six throughout the kingdom, (as testified by witnesses engaged in various manufacturing operations,) by which the national wealth, created as it chiefly is by labour, is retarded or suppressed to the extent of £1,000,000 out of every £6,000,000 that is produced; to say nothing of the constant derangement, imperfection, and destruction in almost every agricultural and manufacturing process, occasioned by the intemperance and consequent unskilfulness, inattention, and neglect of those affected by intoxication, producing great injury to our domestic and foreign trade.

The extensive loss of property by sea from shipwrecks, founderings, fires, and innumerable other accidents, many of which, according to the evidence of the most experienced shipowners, mercantile men, and others, examined by your Committee, are clearly traceable to drunkenness in some of the parties employed in the navigation and charge of such vessels, whose vigilance, had they been sober, would have been sufficient safeguards against their occurrence.

The comparative inefficiency of the navy

and army; in both of which, according to the testimony of eminent naval and military officers examined by your Committee, intemperance is a cankerworm that eats away its strength and its discipline to the core; it being proved beyond all question that onesixth of the effective strength of the navy, and a much greater proportion of the army, is as much destroyed as if the men were slain in battle by that most powerful ally of death, intoxicating drinks; and that the greater number of accidents occurring in both branches of the service, seven-eighths of the sickness, invalidings, and discharges for incapacity, and nine-tenths of all the acts of insubordination, and the fearful punishments and executions to which these give rise, are to be ascribed to drunkenness alone.

That the mere pecuniary loss to the nation from these several causes already enumerated; namely, the destruction of an immense amount of grain subjected o distillation, the abstraction of prodctive labour from the community, the diminished efficiency of the navy and army, the decrease and deterioration of the physical and mental powers of the population, the increase of pauperism, the spread of crime, and the retardation of improvement, caused by the excessive use of intoxicating drinks, may be fairly estimated at little short of £50,000,000 sterling per annum.

THE POST-OFFICE.

ing, and the rates of postage that were then fixed were continued till the reign of Queen Anne. Mails were, however, down to 1784, conveyed either on horseback or in small carts; and instead of being the most expeditious and safest conveyance, the post had become, at the latter period, one of the slowest and most easily robbed of any in the country. In 1784, the coaches accomplished the journey from London to Bath in seventeen hours, while the post took forty hours. This great disproportion gave rise to the establishment of mailcoaches, and such is their regularity at the present time that a post-office regulation fixes to a minute, and in more than one instance to half a minute, the time at which the mails are to arrive at the several towns and villages on the road.

The number of letters and newspapers conveyed to the British post-office is immense. The letters, only, despatched from London, may, we believe, be estimated to average about forty thousand a day; and the postage sometimes exceeds two thousand five hundred pounds in a single morning: yet so complete are the arrangements at the post-office, that forty-four thousand letters have been sorted and marked by one hundred and five persons in the space of forty-five minutes. There may, in all, be about three thousand persons employed in the carriage and distribution of letters in Great Britain only; besides about one hundred and eighty coaches, and from four thousand to five thousand horses. The sum produced by the postage has, of course, progressively increased since the establishment of the post-office. Thus it was,

In 1722 In 1800 In 1814

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£ 204,804 1,083,950 2,005,987

THE post-office was not established in England till the seventeenth century. Post-masters, indeed, existed in more ancient times; but their business was confined to the furnishing of post-horses to persons who were desirous of travelling expeditiously, and to the despatching of since which year it has varied but little. extraordinary packets upon special occa- After all deductions of expenses, the nett sions. In 1635, Charles 1. erected a letter-profit to government amounts to about office for England and Scotland; but this one million three hundred and fifty thouextended only to a few of the principal sand pounds a year. roads, the times of carriage were uncertain, and the post-masters on each road were required to furnish horses for the of letters at the rate of twoconveyance

pence halfpenny a mile. This plan did not succeed; and, at length, a post-office for the weekly conveyance of letters to all parts of the kingdom was established in 1649; by which plan the public saved several thousand pounds a year on account of post-masters. In 1657, the post-office was established nearly on its present foot

RIPE BREAD

BREAD made out of wheat flour, when first taken out of the oven or skillet, is unIt should go prepared for the stomach through a change, or ripen before it is eaten. Young persons, or persons in the enjoyment of vigorous health, may eat bread immediately after it is baked, without any sensible injury from it, but weakly and aged persons cannot; and no one can

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