(Dr John), a famous musician and composer, was a native of North Collingham in the county of Nottingham; and was one of the first set of children after the restoration, being bred up under Captain Henry Cook. He was also a pupil of Hingtonton, and after that of Dr Christopher Gibbons. On the 16th day of March, 1673, he was sworn one of the gentlemen of the chapel in the room of Roger Hill; and in July, 1674, upon the decease of Mr Pelham Humphrey, was appointed master of the children of the chapel. In 1685, he was made one of his majesty's private music; and in 1687, was appointed almoner and master of the choristers of the cathedral church of St Paul. Blow was not a graduate of either university; but archbishop Sancroft, in virtue of his own authority in that respect, conferred on him the degree of doctor in music. Upon the decease of Purcell in 1695, he became organist of Westminster-abbey. In the year 1699, he was appointed composer to his majesty, with a salary. Blow was a composer of anthems while a chapelboy, and on the score of his merit was distinguished by Charles II. 'The king admired very much a little duet of Carissimi to the words "Dite o Ciel,"' and asked of Blow if he could imitate it. Blow modestly answered he would try; and composed in the same measure, and the same key of D with a minor third, that fine song, 'Go, perjured man.' The Orpheus Britannicus of Purcell had been published by his widow soon after his decease; and contained in it some of that author's finest songs; the favourable reception it met with was a motive with Blow to the publication in the year 1700, of a work of the same kind, entitled Amphion Anglicus, containing compositions for one, two, three, and four voices, with accompaniments of instrumental music, and a thorough-bass figured for the organ, harpsichord, or theorboeute. To this book are prefixed commendatory verses by sundry persons; and among them an ode, in the second stanza of which are the following lines:
'His Gloria Patri long ago reach'd Rome, Sung and rever'd too in St Peter's dome; A canon will outlive her jubilees to come.'
The canon here meant is that fine one to which the Gloria Patri in Dr Blow's gamut service is set. Dr Blow set to music an ode for St Cecilia's day, in 1684, the words by Mr Oldham, published together with one of Purcell on the same occasion performed the preceding year. He also composed and published a collection of lessons for the harpsichord or spinnet, and an ode on the death of Purcell, written by Mr Dryden. There are also extant of his composition sundry hymns printed in the Harmonia Sacra, and a great number of catches in the latter editions of the musical companion.—This great musician died in the year 1708, and lies buried in the north aisle of Westminster-abbey. On his monument is the canon above mentioned, engraven on a book with an inscription above it.
a general sense, denotes a stroke given either with the hand, a weapon, or instrument. In fencing, blows differ from thrusts, as the former are given by striking, the latter by pushing.
Military Blow, alapa militaris, that given with a sword on the neck or shoulder of a candidate for knighthood, in the ceremony of dubbing him. The custom seems to have taken its rise from the ancient ceremony of manumission. In giving the blow, the prince used the formula Ego bonus miles, "Be a valiant soldier;" upon which the party rose a complete knight, and qualified to bear arms in his own right.
law. See Battery.
Fly-Blows, the ova of flies deposited on flesh, or other substances proper for hatching them.
Blow-Pipe, in chemistry and mineralogy, an instrument by which the blast of the breath may be directed upon the flame of a lamp or candle, in such a manner as to vitrify any small portion of mineral substance; and thus the process of assaying in the dry way may be performed in a very short time, where either want of instruments or opportunity prevent other methods from being used.
Mr Bergman observes that this instrument is extremely useful to chemists, as many experiments are daily neglected, either because they require furnaces and a large apparatus of vessels; from the want of time to examine them in the ordinary way; or from the quantity required in the common way for examination, when the matter may be too scarce or too dear. In all these cases the blow-pipe may be advantageously used; as, 1. Most of the experiments which can be performed in the large way may also be done with it; 2. The experiments which in the large way require many hours, may in this method be finished in a few minutes; and, 3. The smallest particle is sufficient. The only defect is, that the proportions cannot be determined with any precision; and therefore where the experiments can be tried on a large scale, it is always to be preferred. "But the first inquiry to be made," says our author, "is, what a substance contains, not how much; and I have learned by the experience of many years, that these trials in small suggest the proper methods of instituting experiments in large. These experiments besides have some advantage over those conducted in crucibles, viz. we can see all the phenomena from beginning to end, which wonderfully illustrates the series of operations and their causes. Experiments made in crucibles are often fallacious, as the substance of the vessel itself is corroded. We suppose that lime or magnesia melted with fixed alkali are united with it in the way of solution; Blow-pipe. lution; but the globule, when well fused in the spoon, by its transparency permits us plainly to see that, except the filaceous part, it is only mechanically mixed. The most intense degree of heat may in this way be obtained in a few minutes, which can scarcely be done in a crucible in many hours."
The blow-pipe was first introduced into the chemical apparatus about 50 years ago by the celebrated Swedish metallurgist Dr Andreas Swab, and the instrument was afterwards greatly improved by Meliss Cronstedt, Rinman, &c., and Dr Engelbrecht has an express treatise upon the subject. Mr Bergman proposes that the tube should be made of pure silver, to prevent it from being injured by rust; with the addition of a small quantity of platinum, to give a necessary hardness. It consists of three parts, which may be occasionally joined: An handle (fig. 3.) terminating in a truncated conical apex a a, which may by twisting be so adapted to the aperture b (fig. 4.) as to fit it more closely than can be done by a screw. It was an improvement of former chemists to have a hollow ball on the tube to collect the moisture of the breath, which if suffered to accumulate would greatly diminish the intensity of the flame. Instead of this Mr Bergman made use of the little box (fig. 4.) formed of an elliptical plate, so bent through the centre that the opposite sides become parallel, and are joined round by a plate equal in breadth to c c. Such a box collects the moisture of the breath as well as the sphere, and is besides attended with the advantage of a compressed figure and smaller circumference. The aperture b is somewhat conical, and hollowed out of the solid piece; and has no margin turned inward, left the efflux of the fluid collected after long blowing, or the cleansing of the internal parts, should in any degree be prevented. The tube (fig. 5.) is very small, and its shorter conical end e e exactly fitted to the aperture f, so that no air can escape except through the orifice g. Many of these tubes should be provided with orifices of different diameters, to be applied on different occasions: the orifice g itself ought to be smooth and circular, otherwise the cone of flame hereafter to be mentioned will be divided. The bands (hh ii) prevent the conical apices (aa ee) from being thrust in too far, and also serve another purpose; for when these apices are, by repeated attrition, at last so much diminished as to fall out spontaneously, by filing away a little of the bands they may again be made tight. The figures represent the whole apparatus of the proper size.
How to supply it with a constant stream of air.
The greatest difficulty attending the use of the blow-pipe is the supplying it with a constant stream of air by means of the breath; for to such as are unaccustomed to it, it appears a contradiction to think of blowing a stream of air out by the mouth, at the same time that we are drawing it in by the nostrils to supply the necessary functions of respiration. An uninterrupted stream of air, however, is absolutely necessary; and, "to succeed in this operation (says Mr Bergman) without inconvenience, some labour and practice are necessary. The whole artifice, however, consists in this, that while the air is inspired through the nostrils, that which is contained in the mouth be forced out through the tube by the compression of the cheeks. To some persons this is extremely difficult; but frequent trials will establish the habit; so that a continual blow-pipe stream of air can be supplied for a quarter of an hour or more, without any other inconvenience than the latitude of the lips compressing the tube. A very great and obvious improvement, however, is still suggested by Dr Berkenhout, viz. to apply the tube to the wind-bag of a bagpipe; which being first blown full, may easily be kept so; and being compressed by the arm, will produce a blast either strong or weak as we have a mind. It will be a still farther improvement to supply this bag by means of a small bellows instead of blowing into it with the mouth; for thus the air will be more free from moisture, and also fitter for the support of flame, in other respects; as there is always a considerable quantity of fixed air produced at every respiration, which, according to that quantity, must unfit the air for keeping up the flame, and consequently render the heat less intense.
With regard to the flame proper to be chosen, Mr Bergman directs a slender candle, either of wax or tallow (fig. 6.), with a cotton wick (k l). The burned top must be cut at such a length, that the remainder may be bent a little (l m). The orifice (g) is to be held above and near to this arch, perpendicular to (l m), fig. 5, 6, and the air equably expressed. The flame being forced to one side by the violence of the blast, exhibits two distinct figures; the internal figure (l n), conical, blue, and well defined; at the apex of this, n, the most violent heat is excited; the external flame (l o), brownish, by the vague, and indetermined; which is spoiled of its phlogiston by the surrounding atmosphere, and occasions much less heat at its extremity (o) than the interior flame does.
Dr Black, as well as all other eminent chemists, greatly recommend the use of the blow-pipe for chemical experiments on minerals. The construction recommended by him differs not from that already described; only he says, that it may be made of tin, a cheaper material than silver; though formerly they were made of glass. The small stream of air issuing from the extremity of the tube, being more intimately mixed with the flame, and agitated with it, occasions a more complete consumption of the vapour arising from the candle, and makes it produce much more heat; so that any small body exposed to the extremity of the flame is heated to a surprising degree. Several artists who work in metals, as the goldsmiths, &c., find this instrument useful in soldering small pieces of metal together; and it is also used by the chemists in examining the effects of violent heat upon small bodies. Some of the artists who use it much, supply the stream of air with a pair of bellows placed under the table, with a pipe rising up through it, and to which the blow-pipe is fixed. In the examination of ores, the more simple instrument is preferred; and by a little practice it is easy to blow a continued stream of air with the mouth, by keeping it always full, and drawing in the air by the nostrils, which answers the same purpose as the upper part of a double bellows. Mr Cronstedt used the blow-pipe much in making the experiments on which his system of mineralogy is founded, blowing air through a bit of charcoal; and though the specimens are small, we can see the changes they undergo as well as if they were larger; and the eye can be assisted by a magnifying glass. The reason of the intense heat produced by the blow-pipe is, that in the ordinary way of burning, the air acts only upon the external surface of the fuel, so that it is not completely inflamed.
The blow-pipe used by Mr Cronstedt is composed of two parts; and this for the facility both of making, carrying it along, and cleansing it in the inside when necessary. The two parts are represented separately, and of the true size; the figure of the instrument, when these are put together, may be easily conceived.
The globe \(a\) (fig. 2.) is hollow, and made on purpose to condense the vapours, which always happen to be in the blow-pipe when it has been used some time; if this globe was not there, the vapours would go directly with the wind out into the flame, and thereby cool the affray. The hole in the small end \(b\), through which the wind comes out, ought not to be larger than the size of the finest wire. This hole may now and then happen to be stopped up by something coming into it, so as to hinder the force of the wind; one ought therefore to have a piece of the finest wire, to clear it when required; and, in order to have this wire the better at hand, it may be fastened round the blow pipe, in such a manner as is represented in fig. 1: \(c\) is the wire fastened round the blow-pipe, and afterwards drawn through a small hole at \(e\), made in the ring \(f\), to keep it more steady.
In order to determine the most convenient proportions of this instrument, several blow-pipes of different sizes, both bigger and smaller, have been tried: the former have required too much wind; and the latter, being too soon filled with the wind, have returned it back again upon the lungs; both these circumstances hindered greatly the experiments, and are perhaps even prejudicial to the health. The size here given is found to answer best; and though the hole must be as small as abovementioned, yet the sides of the pipe at the point must not be thinner, nor the point narrower, than here represented, else it will be too weak, and not give so good a flame. It is also to be observed, that the canal throughout the pipe, but particularly the hole at the small end, must be made very smooth, so that there be no inequalities in it; the wind would else be divided, and consequently the flame made double. That blow-pipe is to be reckoned the best, through which can be formed the longest and most pointed flame from off a common-sized candle. These blow-pipes are commonly made of brass or silver.
There are two different kinds of matter made use of for the support of these substances usually examined by the blow-pipe: the one is charcoal of fir, or beech, cut into the form of a parallelipiped; the other a silver, or, which is better, a golden spoon, fitted with a wooden handle. The former is generally used, excepting where phlogiston is to be avoided, or the subject of examination is apt to be absorbed by the charcoal. The golden spoon should be much less than the figure (7,) as the bulk of the support prevents the heat from being raised to a proper degree. To prevent the fine light particles from being carried off by the blast, a small cavity should be hollowed out in the charcoal; in which, being partly protected by another smaller piece of charcoal, they may be exposed to the apex of the flame.
Were it possible to procure a sufficient quantity of dephlogisticated air, experiments with the blow-pipe blowpipe could be rendered still more important than they are, as we might by this means be able to fuse and vitrify substances per se, which we are now scarce able to do excited with the most powerful fluxes. The difficulty of procuring this kind of air, however, has as yet, in a great cated air measure, excluded the use of it from chemistry, though M. le Blond, Medicin Naturaliste du Roi, in a letter to the editor of the Journal de Physique for February 1787, proposes, instead of blowing through the tube, to adapt to the wide end of it a leathern bag, the size of an ox's bladder, filled with pure air. Were this bag made to communicate, by means of a pair of small bellows, with a reservoir containing a considerable quantity of this dephlogisticated air, there is no doubt that many chemical operations might by its means be very advantageously performed; and we are already assured, that, by the use of this kind of air, platinum itself may be melted. As dephlogisticated air, however, has not yet come into use, we can only expect such effects as may be produced by a violent blast of common atmospheric air; and for this purpose we must accommodate ourselves with proper fluxes. The following are recommended by Mr Bergman.
1. The phosphoric acid, or rather the microcosmic properties of the phosphoric acid, as it is called, which contains that acid partly saturated with mineral, partly with volatile alkali, and as a flux loaded besides with much water and a gelatinous fat. This fat, when exposed to the flame, boils and foams violently, with a continual crackling noise, until the water and volatile alkali have flown off; afterwards it is less agitated, sending forth something like black scoria arising from the burned gelatinous part: these, however, are soon dispersed, and exhibit a pellucid sphericle encompassed by a beautiful green cloud, which is occasioned by the deflagration of the phosphorus arising from the extrication of the acid by means of the inflammable matter. The clear globule which remains, upon the removal of the flame, continues longer soft than that formed by borax; and therefore is more fit for the addition of the matter to be dissolved. The volatile alkali is expelled by the fire; therefore an excess of acid remains in what is left behind, which readily attracts moisture in a cool place.
2. The mineral alkali, or sal soda, when put upon charcoal, melts superficially, penetrates the charcoal with a crackling noise, and then disappears. In the spoon it yields a permanent and pellucid sphericle as long as it is kept fluid by the blue apex of the flame; but when the heat is diminished, it becomes opaque, and assumes a milky colour. It attacks several earthly matters, particularly those of the filaceous kind, but cannot be employed on charcoal for the reasons assigned above.
3. Crystalized borax, exposed to the flame urged by the blow-pipe or charcoal, first becomes opaque, white, and excessively swelled, with various protuberances, or branches proceeding out from it. When the water is expelled, it easily collects itself into a mass, which, when well fused, yields a transparent sphericle, retaining its transparency even after cooling. If calcined borax be employed, the clear sphericle is obtained sooner.
Having thus provided every thing necessary, the following directions are next to be attended to. 1. A common tallow candle, not too thick, is generally preferable to a wax candle, or to a lamp. The snuff must not be cut too short, as the wick should bend towards the object.
2. The weaker exterior flame must first be directed upon the object, until its effects be discovered; after which the interior flame must be applied.
3. We must observe with attention whether the matter decrepitates, splits, swells, vegetates, boils, &c.
4. The piece exposed to the flame should scarcely ever exceed the size of a pepper-corn; but ought always to be large enough to be taken up by the forceps (fig. 10). When the particle is too large, part of it must necessarily be without the focus; and thus cool both the support and the part immersed in the blue apex (fig. 6.). It may, however, be broken into pieces sufficiently small by means of the hammer (fig. 8.), upon the steel plate (fig. 9); any of the small parts being prevented from flying off by the ring H.
5. A small piece should be added separately to each of the fluxes: concerning which it must be observed, whether it dissolves wholly, or only in part; whether this be effected with or without effervescence, quickly or slowly; whether the mass be divided into a powder, or gradually and externally corroded; with what colour the glass is tinged; and whether it becomes opaque, or remains lucid.
Having given these directions, our author (Mr Bergman) proceeds next to consider the subjects proper to be examined by the blow-pipe. These he divides into four classes: 1. Saline; 2. Earthy; 3. Inflammable; and, 4. Metallic.
1. The Salts, though distinguished by their taste and solubility in water, differ so much in degree, that it is impossible to distinguish them absolutely from the earths by any natural boundaries. Many of them, when exposed to the flame, easily melt by the water of crystallization they contain. After this is dissipated, they split; and by a more intense heat are readily fused: others are deprived of their water without any fusion; and then melt once by a heat more or less intense, according to their nature; and some fly off with the heat.
Acids in general cannot bear the action of the blow-pipe, such at least as are easily kept in a fluid state. It is otherwise, however, with some of those which attract the inflammable matter, generates white arsenic, and flies off in vapours. In the spoon it melts without emitting smoke, unless it can acquire phlogiston either from the support on which it is placed, or the flame of the candle. The acid of molybdena, according to our author, seems to be the basis of some metal, as it has a specific gravity of 3.461, possesses the property of tingling fluxes, and decomposing the phlogisticated alkali; he adds, "Is this the acid of tin?" This acid is absorbed by charcoal; and in the spoon emits a white smoke, which on touching the apex of the interior flame, affumes a beautiful blue colour, and again grows white upon exposure to the exterior flame. It tinges microcosmic salt of a fine green; borax affumes an ash-colour by reflection, but has a dark violet when we look through it. The acid of borax, commonly called salpetre, easily liquefies, in the same manner with borax itself, but does not swell so much as that salt does. It leaves a fixed pellucid globule. Acid of tartar liquefies on the first contact of blow-pipe, the exterior flame, swells, foams, grows black, and sends forth a smoke and blue flame, leaving a spongy coal, the greatest part of which is soon converted into ashes of a calcareous nature. The combustion, however, must be slow, and the weakest part of the flame only employed, in order to observe these changes distinctly. By the contact of the exterior flame, crystalized acid of sugar is first made of an opaque white, of sugar; then melts, and, lastly, flies off without leaving any residuum. Acid of phosphorus easily melts into a pellucide of the acid globule, which afterwards deliquesces in the air, of phosphoric acid. Crystalized vegetable alkali first becomes opaque, and then decrepitates long and violently; then melts into a globule, which remains in the spoon; but expands on charcoal, and is absorbed with a crackling noise. The volatile alkaline alkali liquefies a little, and is then dissipated.
Several of the neutral salts flow twice, according to the quantity of water they contain in their crystals, decrepitating. The decrepitating salts are broken and dispersed by a neutral sudden heat. Of this kind are vitriolated tartar, vitriolic acid ammoniacal, common salt, and sal digestive. Those which have a volatile alkali for their basis, fly off in a very short time. —By the application of the salt of external flame, salt of amber laid on charcoal liquefies amber, and smokes, the contact of the internal flame sets it on fire, and it continues to burn with a blue flame till it totally disappears. The same thing takes place when it is put in the spoon, excepting when it contains too great a quantity of oil, which indeed very frequently happens. In this case, some traces of coal are to be met with. The spurious salt of amber presents different phenomena according to the substances made use of in adulterating it.
The detonating salts, into which the nitrous acid always enters as a component part, liquefy in the spoon, and are not decomposed on the charcoal until it takes fire: they are then decomposed with violent flame and noise, but which is different in degree according to the basis with which the nitrous acid is united. Thus the nitrous acid combined with vegetable alkali burns with a blue flame, but with the mineral and volatile alkali has a yellow one.
The carbonaceous salts yield spongy coals by the combustion of their acid, which by ignition becomes fusible. White, leaving their alkaline basis pure behind them. These are the acid of tartar, crude tartar, salt of forrel, and tartarized mineral and vegetable alkali.
The hepatic salts, when put on charcoal, melt into a red or yellow mass, which diffuses an hepatic smell, especially when moistened by an acid. To this class belong all those fixed in the fire which contain the vitriolic acid, and which when saturated with phlogiston produces sulphur; such as vitriolated tartar and Glauber's salt.
Few of the earthy salts flow sufficiently thin to be reduced into a perfect globule; nor do they all actually enter into fusion, though the water of crystallization excites a great foam by its going off. Those which contain the vitriolic acid effervesce violently with borax and microcosmic salt, but are dissolved with difficulty by the salt of soda.
The intumescent salts. 1. Vitriolated magnesia, intumescently called ephem salt, swells, foams, and may be cent salts, melted by being repeatedly exposed to the flame. 2. Alum Alum is somewhat different; for finally all ebullition ceases, and the mass remains incapable of further change by fire than to split. When hot, it is variegated with blue spots. 3. A combination of lime with acetic acid swells much like alum, but scarcely adheres to the charcoal. 4. Nitrated magnesia swells with a crackling noise, but without any detonation. 5. To this class also belongs the combination of marine acid with magnesia.
Gypsum eluded the utmost force of Mr Pott's furnace, but may be fused in a moment by exposing a section of the lamella to the blue flame. Though naturally pellucid, it instantly becomes opaque; and the water it contains flies off without any ebullition.
The following substances are soluble in borax and microcosmic salt with effervescence:
1. Lime, magnesia, alum, and combination of lime with acetic acid.
2. The metallic salts which do not decrepitate. Some of these containing either a large quantity of water in their crystals, or obstinately retaining their acid, flow in the fire, while others only foam. Most of them recover, in part at least, their metallic appearance, especially when they touch the coal, leaving at the same time a shapeless scoria. By the addition of borax, the scoriae are dissolved, and the regulus better collected; the fluxes are tinged in the same manner as by the metallic calces.
3. The decrepitating metallic salts; lead combined with nitrous acid, and antimony with that of tartar.
4. Volatile metallic salts which have mercury for their basis. Those which contain marine acid in general fly off more quickly than those in which the metal is combined with any other menstruum.
5. Detonating metallic salts, as silver, mercury, lead, and bismuth united with nitrous acid.
6. The intumescing metallic salts, vitriolated and nitrated copper, iron and cobalt vitriolated, and nitrated zinc. These swell with noise and a certain degree of ebullition on the first contact of the flame, but afterwards remain unchanged.
7. The fusible metallic salts, as silver and lead combined with vitriolic acid, and zinc combined with marine acid.
8. Antimony combined with acid of tartar, a carbonaceous metallic salt.
9. Metallic salts communicating a certain colour to the flame. Blue vitriol, and solution of copper in nitrous acid, produce a greenness; but solution of copper in spirit of salt acts with much more efficacy. The green crystals of this first grow red by the contact of the external flame; afterwards they liquefy and grow black, making the flame at first of a deep blue, which afterwards verges to a green. The flame thus tinged expands much, and remains in that state until the whole of the salt be dissipated. This green salt, added to microcosmic salt in fusion, immediately shows a beautiful flame: the clear globule is tinged green, and does not grow opaque or brown, unless a large quantity of the microcosmic salt be added; a circumstance which takes place much sooner on adding a small quantity of borax.
11. Earthy Substances.—1. Crude calcareous earth effervesces a little with mineral alkali, and is divided into small particles, but sparingly dissolved. When over-burned, it seems not to be divided or diminished. The former diffuses in borax with effervescence; but the latter scarcely produces any bubbles. The same phenomena takes place with microcosmic acid, only the effervescence is somewhat greater. A very small piece of calcareous earth is easily dissolved in borax and microcosmic salt, yielding quite pellucid sphericles: but if more earth be gradually added, the flux, saturated at length, retains the dissolved matter indeed while in perfect fusion, but on removing it from the flame, the part which was taken up by the heat alone soon separates. Hence clouds first begin to appear, and at length the whole globule becomes opaque, but recovers its transparency again by fusion. If the melted pellucid globule, however, which would grow opaque by cooling, be plunged while hot into melting tallow, water, or other substances likewise hot (for cold generally cracks it), so as to grow suddenly hard, it retains its transparency; the particles being as it were fixed in that state which is necessary to transparency.
2. Terra ponderosa, exposed alone to the flame, becomes caustic, fusible in water, and loses its property deroga of effervescing with acids. It effervesces a little, and is sensibly diminished by salt of soda; dissolves with a slight effervescence in borax, as well as in microcosmic salt, but effervesces somewhat more violently in the latter.
3. Magnesia by itself loses its aerial acid, and with Magnesia, it the property of effervescing with acids. In salt of soda, it is scarcely diminished, but effervesces a little. It dissolves in borax also, with a slight effervescence; and likewise in microcosmic salt, but with a greater effervescence.
4. Common clay contains a number of heterogeneous particles, particularly siliceous earth, of which the quantity is generally one half of the whole. When pure clay therefore is required, the earth of alum digested in an alkaline lixivium, and well washed, must be employed. This earth, on exposure to the flame, grows hard, contracts in bulk, but does not melt. It effervesces a little in sal soda, but is sparingly dissolved. In borax it dissolves with a very considerable effervescence, and with a still greater in microcosmic acid.
5. Siliceous earth, by itself, is not fused. In sal soda it dissolves with remarkable effervescence; and if earth, the siliceous earth dissolved exceeds the weight of the flux, it yields a pellucid glass. This, and all the other operations with sal soda, must be performed in a spoon. In borax it dissolves slowly, without any effervescence; and in a similar manner, only still more slowly, in microcosmic acid.
Mr Bergman next enumerates the various earths of all different kinds which he had subjected to the blow pipe; and of these he found that the following did not without the utmost difficulty show any signs of fusion: viz. Pure asbestos, refractory clay, pure mica, sapphire, flint, and steatite. The four last are indurated by fire. Of the same kind are the chrysolite and emerald, chalcedony, cornelian, hydrophanus, siliceous, jasper, onyx, opal, and quartz. The rest are fusible either by themselves or with the addition of proper fluxes. On these, he observes, in general, that when the effervescence is to be examined, only a very little piece of the matter is Blow pipe, is to be added to the flux; as the most subtle powder contains air, which being expelled by the heat, forms an appearance of effervescence. 2. The solution is often accelerated by lime, spathum ponderofum, gypsum, and other additions. 3. Gypsum alone is often an excellent flux. With an equal quantity of mineral flour it is easily reduced to a pellucid globule, which grows white and opaque on cooling. The spathum ponderofum also unites with mineral flour; but the mass does not become pellucid.
III. Most Inflammable Substances, when exposed to the apex of the flame, begin to liquefy, unless they have a great quantity of earth in their composition; which, however, does not generally prevent their inflammation. When they are once inflamed, the blast ought to be stopped until they have burned away either alone or with a flux; after which the residuum is to be examined by the flame. The most remarkable appearances exhibited by inflammable substances, when examined by the blow-pipe, are the following:
1. Ambergris burns with a white, smoky, and odoriferous flame, until it is totally consumed; but when impure, it is extinguished, leaving behind a black mass which soon grows white by ignition, and consists partly of calcareous powder. 2. Transparent amber exhibits almost the same appearance, but vanishes totally by heat in the spoon; so that in this way we can scarcely form any judgment of the residuum; which, however, is easily obtained from opaque amber.
3. Pure asphaltum burns with smoke, and is totally consumed without any residuum. 4. Mountain pitch leaves black scoriae, thinning, and of a brittle nature. 5. Bituminous schist and lithanthrax, besides their matrix, leave an oily coal, or even spongy scoriae, if the residuum liquefies at all. 6. Common sulphur readily melts alone, and grows red; after which it takes fire, and is consumed with a blue flame and a most penetrating and suffocating odour. 7. Molybdena contains a portion of common sulphur united to a peculiar acid. It does not take fire, and suffers but little change on the charcoal; but on being exposed to the flame in the spoon, it deposits a white smoke in direction of the blast. This smoke grows blue by the contact of the interior flame, but loses its colour by the exterior one. It undergoes little change by borax or the microcosmic salt, but dissolves in salt of soda with violent effervescence. It grows red and transparent by fusion; and when cold, affumes a dilute red colour and opaque, with an hepatic smell. 8. Plumbago emits smoke on burning, but which is only perceptible the instant the flame ceases. It differs from molybdena in not depositing any white powder, and particularly in not being taken up by salt of soda. It is not changed by borax or microcosmic salt.
Inflammable ores take fire with difficulty; some are scarcely changed, while others are consumed or fly off, leaving the metallic calx behind.
The fluxes in general are tinged by phlogiston; but unless this be fixed by some metallic calx, it is easily destroyed by burning.
IV. The perfect Metals lose no part of their phlogiston even in the most intense heat; and when calcined in the moist way, recover their former nature by simple fusion. The imperfect metals are calcined by fire, especially by the exterior flame; and then, in order to their being reduced, indispensably require the contact of a phlogistic substance. With respect to fusibility, the two extremes are mercury and platinum; the former of the difference being scarce ever seen in a solid form, and the latter almost as difficult of fusion. The metals therefore of fusibility may be ranked in this order, according to their degree of fusibility: 1. Mercury. 2. Tin. 3. Bismuth. 4. Lead. 5. Zinc. 6. Antimony. 7. Silver. 8. Gold. 9. Arsenic. 10. Cobalt. 11. Nickel. 12. Iron. 13. Manganese. 14. Platinum. The two last do not yield to the blow-pipe, and indeed forged iron does not yield not melt without difficulty; but cast iron perfectly.
Metals in fusion affect a globular form, and easily roll off the charcoal, especially when of the size of a grain of pepper. Smaller pieces therefore ought to be used, or they should be placed in hollows made in the charcoal. On their first melting they afford the fume a polished surface, an appearance always retained by the perfect metals; but the imperfect are soon obscured by a pellicle formed of the calx of the metal. The colours communicated by the calces vary according to the nature of the metal from which the calx is produced. Some of the calces easily recover their metallic form by simple exposure to flame upon the charcoal; others are reduced in this way with more difficulty; and some not at all. The reduced calces of the volatile metals immediately fly off from the charcoal. In the spoon they exhibit nitrous globules; but it is very difficult to prevent them from being first dilipated by the blast.
The metals are taken up by the fluxes; but as mineral alkali yields an opaque sphere, it is not to be perused of. Globules of borax dissolve and melt any metal with metallic calx; and unless too much loaded with it, appear pellucid and coloured. A piece of metal calcined in the flux produces the same effect, but more slowly. A portion of the calx generally recovers its metallic form, and floats on the melted matter like one or more excrescences. In proportion as the globule is more loaded it extends itself more on the charcoal, and at length cannot assume a globular form; for the metallic additament augments the attraction for phlogiston.
The calces of the perfect metals are reduced by boiling in the spoon, and adhere to it at the point of contact, and there only. The microcosmic salt acts as a perborax, but does not reduce the metals. It attacks them more powerfully on account of its acid nature; at the same time it preserves the spherical form, and therefore is adapted in a peculiar manner to the investigation of metals.
The tinge communicated to the flux frequently varies, being different in the fused and in the cooled globule; for some of the dissolved calces, while fused, the fluxes show no colour, but acquire one while cooling; but others, on the contrary, have a much more intense colour while in the state of fluidity. Should the transparency be injured by too great a concentration of colour, the globule, on compressing it with the forceps, or drawing it out into a thread, will exhibit a thin and transparent mass; but if the opacity arises from supersaturation, more flux must be added; and as the fluxes attract the metals with unequal forces, the latter precipitate one another.
Metals when mineralized by acids have the properties ties of metallic salts; when mineralized by fixed air, they possess the properties of calces, that volatile substance being easily expelled without any effervescence; but when combined with sulphur, they possess properties of a peculiar kind. They may then be melted, or even calcined upon the charcoal, as also in a golden or silver spoon. The volatile parts are distinguished by the smell or smoke; the fixed residue by the particles reduced or precipitated upon iron, or from the tinge of the fluxes.
Gold in its metallic state fuses on the charcoal, and is the only metal which remains unchanged. It may be deprived of its phlogiston in the moist way by solution in aqua regia; but to calcine it also by fire, we must pursue the following method: To a globule of microcosmic salt let there be added a small piece of solid gold, of gold leaf, purple mineral, or, which is best of all, of the crystalline salt formed by a solution of gold in aqua regia containing sea-salt. Let this again be melted, and added while yet soft to turpith mineral, which will immediately grow red on the contact. The fusion being afterwards repeated, a vehement effervescence arises; and when this is considerably diminished, let the blast be stopped for a few moments, again begun, and so continued until almost all the bubbles disappear. After this the sphere, on cooling, affumes a ruby colour; but if this does not happen, let it be just made soft by the exterior flame, and upon hardening this tinge generally appears. Should the process fail at first, owing to some minute circumstances which cannot be described, it will succeed on the second or third trial. The ruby-coloured globule, when compressed by the forceps while hot, frequently becomes blue; by sudden fusion it generally affumes an opal colour, which by refraction appears blue, and by reflection of a brown red; if further urged by the fire, it loses all colour, and appears like water; but the redness may be reproduced several times by the addition of turpith mineral. The flux is reddened in the same manner by the addition of tin instead of turpith; but it has a yellowish hue, and more easily becomes opaque; while the redness communicated by turpith mineral has a purple tinge, and quite resembles a ruby. Borax produces the same phenomena, but more rarely; and in all cases the slightest variation in the management of the fire will make the experiment fail entirely.
The ruby colour may also be produced by copper; whence a doubt may arise, whether it be the gold or the remains of the copper that produces this effect. Mr Bergman thinks it probable that both may contribute towards it, especially as copper is often found to contain gold.
This precious metal cannot directly be mineralized by sulphur; but by the medium of iron is sometimes formed into a golden pyrites. Here, however, the quantity of gold is so small, that a globule can scarcely be extracted from it by the blow-pipe.
Grains of native platinum are not affected by the blow-pipe either alone or mixed with fluxes; which, however, are frequently tinged green by it; but platinum, precipitated from aqua regia by vegetable or volatile alkali, is reduced by microcosmic salt to a small malleable globule. Our author has been able to unite seven or eight of these into a malleable mass; but more of them produced only a brittle one. Platina scarcely loses all its iron unless reduced to very thin fusion.
Silver in its metallic state easily melts, and results Of silver in calcination. Silver leaf fattened by means of the breath, or a solution of borax, may easily be fixed on it by the flame, and through the glass it appears of a gold colour; but care must be taken not to crack the glass. Calcined silver precipitated from nitrous acid by fixed alkali is easily reduced. The microcosmic acid dissolves it speedily and copiously; but, on cooling, it becomes opaque and of a whitish yellow, which is also sometimes the case with leaf-silver. Copper is discovered by a green colour, and sometimes by that of a ruby, unless we choose rather to impute that to gold. The globules can scarcely be obtained pellucid, unless the quantity of calx be very small; but a longer fusion is necessary to produce an opacity with borax. The globule, loaded with dissolved silver during the time of its fusion in the spoon, covers a piece of copper with silver, and becomes itself of a pellucid green; antimony quickly takes away the milky opacity of dissolved luna cornea, and separates the silver in distinct grains. Cobalt and most of the other metals likewise precipitate silver on the same principles as in the moist way, viz. by a double elective attraction. The metal to be dissolved remains untouched as long as it retains its phlogiston; but is taken up when a sufficient quantity of that principle has shifted to the precipitate and reduced it. This metal, when mineralized by marine and vitriolic acids, yields a natural luna cornea, which produces a number of small metallic globules on the charcoal; it dissolves in microcosmic salt, and renders it opaque; and is reduced, partially at least, by borax. Sulphurated silver, called also the glairy ore of that metal, fused upon charcoal, easily parts with the sulphur it contains; so that a polished globule is often produced, which, if necessary, may be depurated by borax. The silver may also be precipitated by the addition of copper, iron, or manganese. When arsenic makes part of the compound, as in the red ore of arsenic, it must first be freed from the sulphur by gentle roasting, and finally entirely depurated by borax. It decrepitates in the fire at first.
Copper, together with sulphur and arsenic mixed with silver, called the white ore of silver, yields a regulus having the same alloy.
Galena, which is an ore of lead containing sulphur and silver, is to be freed in the same manner from the sulphur; after which the lead is gradually distillated by alternately melting and cooling, or is separated in a cupel from the galena by means of the flame. Our author has not been able to precipitate the silver distinctly from the lead, but the whole mass becomes malleable; and the same is true of tin, but the mass becomes more brittle.
Pure mercury flies off from the charcoal with a moderate heat, the fixed heterogeneous matters remaining behind. When calcined it is easily reduced and distilled, and the fluxes take it up with effervescence; but it is soon totally driven off. When mineralized by sulphur it liquefies upon the charcoal, burns with a blue flame, smokes, and gradually disappears; but on exposing, exposing cinnabar to the fire, on a polished piece of copper, the mercurial globules are fixed upon it all round.
Lead, in its metallic state, readily melts, and continues to retain a metallic splendor for some time. By a more intense heat it boils and smokes, forming a yellow circle upon the charcoal. It communicates a yellow colour, scarcely visible, to the fluxes; and when the quantity is large, the globe, on cooling, contracts more or less of a white opacity. It is not precipitated by copper when dissolved; nor do the metals precipitate it from sulphur in the same order as from the acids. When united to aerial acid, it grows red on the first touch of the flame; when the heat is increased, it melts, and is reduced to a multitude of small globules. When united with phosphoric acid, it melts and yields an opaque globule, but is not reduced. With fluxes it shows the same appearances as calx of lead. When mineralized by sulphur, lead easily liquefies, and, being gradually deprived of the volatile part, yields a distinct regulus, unless too much loaded with iron. It may be precipitated by iron and copper.
A small piece of copper, either solid or foliated, sometimes communicates a ruby colour to fluxes, especially when assisted by tin or turbith mineral. If the copper be a little more or further calcined, it produces a green pellucid globule, the tinge of which grows weaker by cooling, and even verges towards a blue. By long fusion with borax, the colour is totally destroyed upon charcoal, but scarcely in the spoon. When once destroyed, this colour can scarcely be reproduced by nitre; but it remains fixed with microcosmic salt. If the calx or metal to be calcined be added in considerable quantity during fusion, it acquires an opaque red on cooling, though it appears green while pellucid and fused; but by a still larger quantity it contracts an opacity even while in fusion, and, upon cooling, a metallic splendor. Even when the quantity of copper is so small as scarcely to tinge the flux, a visible pellicle is precipitated upon a piece of polished iron added to it during strong fusion, and the globule in its turn takes the colour of polished iron; and in this way the smallest portions of copper may be discovered. The globule made green by copper, when fused in the spoon with a small portion of tin, yields a spherule of the latter mixed with copper, very hard and brittle; in this case the precipitated metal pervades the whole of the mass, and does not adhere to the surface. Cobalt precipitates the calx of copper dissolved in the spoon by a flux, in a metallic form, and imparts its own colour to glass, which nickel cannot do. Zinc also precipitates it separately, and rarely upon its own surface, as we can scarcely avoid melting it. When mineralized by the aerial acid, copper grows black on the first contact of the flame, and melts in the spoon; on the charcoal, the lower part, which touches the support, is reduced. With a superabundance of marine acid, it tinges the flame of a beautiful colour; but with a small quantity shows no appearance of the metal in that way. Thus the beautiful crystals of Saxony, which are cubic, and of a deep green, do not tinge the flame, though they impart a pellucid greenness to microcosmic salt. An opaque redness is easily obtained with borax; but Mr Bergman could not produce this colour with microcosmic salt. Copper No. 49.
Simply sulphurated, when cautiously and gently roasted by the blow-pipe, by the exterior flame, yields at last, by fusion, a regulus surrounded with a sulphurated crust. The mass roasted with borax separates the regulus more quickly.
If a small quantity of iron happens to be present, the piece to be examined must first be roasted; after which it must be dissolved in borax, and tin added to precipitate the copper. The regulus may also be obtained by sufficient calcination and fusion, even without any precipitant, unless the ore be very poor. When the pyrites contain copper, even in the quantity of the one-hundredth part of their weight, its presence may be detected by these experiments: Let a grain of pyrites, of the size of a flax-seed, be roasted, but not so much as to expel all the sulphur; let it then be dissolved by borax, a polished rod of iron added, and the fusion continued until the surface when cooled loses all splendor. As much borax is required as will make the whole of the size of a grain of hemp-seed. Slow fusion is injurious, and the precipitation is also retarded by too great tenacity; but this may be corrected by the addition of a little lime. Too much calcination is also inconvenient; for by this the globule forms slowly, is somewhat spread, becomes knotty when warm, corrodes the charcoal, destroys the iron, and the copper does not precipitate distinctly. This defect is corrected by a small portion of crude ore. When the globule is properly melted, according to the directions already given, it ought to be thrown into cold water immediately on stopping the blast, in order to break it suddenly. If the copper contained in it be less than one-hundredth part, one end of the wire only has a cuprous appearance, but otherwise the whole.
Dr Gahn has another method of examining the ores of copper; namely, by exposing a grain of the ore, freed of ex-well freed from sulphur by calcination, to the action of the flame driven suddenly upon it by intervals. At those instants a cuprous splendor appears on the surface, which otherwise is black; and this splendor is more quickly produced in proportion as the ore is poorer. The flame is tinged green by cuprous pyrites on roasting.
Forged iron is calcined, but can scarcely be melted; and liquefies on being fused. It cannot be melted by borax, though it may by microcosmic salt; and then it becomes brittle. Calcined iron becomes magnetic by being heated on the charcoal, but melts in the spoon. The fluxes become green by this metal; but in proportion as the phlogiston is more deficient they grow more of a brownish yellow. On cooling, the tinge is much weakened; and, when originally weak, vanishes entirely. By too much saturation the globule becomes black and opaque. The sulphurous pyrites may be collected into a globule by fusion, and is first surrounded by a blue flame; but as the metal is easily calcined, and changes into black scorine, neither by itself nor with fluxes does it exhibit a regulus. It grows red on roasting.
Tin easily melts before the blow-pipe, and is calcined. The fluxes dissolve the calx sparingly; and, when saturated, contract a milky opacity. Some small particles of this metal dissolved in any flux may be distinctly precipitated upon iron. Crystallized ore of tin, urged by fire upon the charcoal, yields its metal in a reguline state.
Bismuth Bismuth presents nearly the same appearances as lead; the calx is reduced on the coal, and fused in the spoon. The calx, dissolved in microcosmic salt, yields a brownish yellow globule, which grows more pale upon cooling, at the same time losing some of its transparency. Too much calx renders the matter perfectly opaque. Borax produces a similar mass in the spoon; but on the coal a grey one, which can scarcely be freed from bubbles. On fusion the glass smokes and forms a cloud about it. Bismuth is easily precipitated by copper and iron.
Sulphurated bismuth is easily fused, exhibiting a blue flame and fulgurous smell. Cobalt, when added, by means of the sulphur, enters the globule; but the scoria soon swells into distinct partitions; which when further urged by fire, throws out globules of bismuth. Sulphurated bismuth, by the addition of borax, may be distinctly precipitated by iron or manganese.
Regulus of nickel when melted is calcined, but more slowly than other metals. The calx imparts an hyacinthine colour to fluxes, which grows yellow on cooling, and by long continued fire may be destroyed. If the calx of nickel be contaminated by ochre of iron, the latter is first dissolved. Nickel dissolved is precipitated on iron, or even on copper; an evident proof that it does not originate from either of these metals. Sulphurated nickel is no where found without iron and arsenic: the regulus is obtained by roasting, and fusing with borax, though it still remains mixed with some other metals.
Regulus of arsenic takes fire by a sudden heat, and not only deposits a white smoke on charcoal, but diffuses the same all around. The calx fumes with a smell of garlic, but does not burn. The fluxes grow yellow, without growing opaque, on adding a proper quantity of calx, which is dispelled by a long continuance of the heat. This semimetal is precipitated in a metallic form by iron and copper, but not by gold. Yellow arsenic liquefies, fumes, and totally evaporates: when heated by the external flame, so as neither to liquefy nor smoke, it grows red and yellow again upon cooling. When it begins to melt it acquires a red colour, which remains after cooling. Realgar liquefies more easily, and is besides totally dissipated.
Regulus of cobalt melts, and may partly be depurated by borax, as the iron is first calcined and taken up. The smallest portion of the calx tinges the flux of a deep blue colour, which appears of a violet by refraction, and this colour is very fixed in the fire. Cobalt is precipitated upon iron from the blue globule, but not upon copper. When calx of iron is mixed with that of cobalt in a flux, the former is dissolved. This semimetal takes up about one third of its weight of sulphur in fusion, after which it can hardly be melted again. It is precipitated by iron, copper, and several other metals. The common ore yields an impure regulus by roasting. The green cobalt, examined by our author, tinges the microcosmic salt blue; but at the same time shows red spots indicating copper.
Zinc exposed to the blow-pipe melts, takes fire, sending forth a beautiful bluish green flame, which however is soon extinguished by a lanuginous calx; but if the reguline nucleus included in this lanuginous matter (commonly called flowers of zinc) be urged by the flame, it will now and then inflamed, and as it were explodes and flies about. With borax it froths, and at first tinged the flame. It continually diminishes, and the flux spreads upon the charcoal; but in fused microcosmic salt it not only froths, but sends forth flashes with a crackling noise. Too great heat makes it explode with the emission of ignited particles. The white calx, or flowers, exposed to the flame on charcoal, becomes yellowish, and has a kind of splendor, which vanishes when the flame ceases. It remains fixed, and cannot be melted. The fluxes are scarcely tinged; but when saturated by fusion, grow opaque and white on cooling. Clouds are formed round the globules of a nature similar to that of the metallic calx. Dissolved zinc is not precipitated by any other metal. When mineralized by aerial acid, it has the same properties as calcined zinc. In the pseudo-galena sulphur and iron are present. These generally, on the charcoal, smell of sulphur, melt, and tinge the flame more or less, depositing a cloud all around. Those which have no matrix are tinged by those which contain iron, and acquire by saturation a white opaque colour, verging to brown or black, according to the variety of composition.
Regulus of antimony fused and ignited on the charcoal, affords a beautiful object; for if the blast of air be suddenly stopped, a thick white smoke rises perpendicularly, while the lower part round the globule is condensed into crystalline spiculae, similar to those called Argentine flowers. The calx tinges fluxes of an hyacinthine colour; but on fusion smokes, and is easily dissipated, especially on the charcoal, though it also deposits a cloud on it. The dissolved metal may be precipitated by iron and copper, but not by gold. Crude antimony liquefies on the charcoal, spreads, smokes, penetrates it, and at last disappears entirely except a ring which it leaves behind.
Regulus of manganese feebly yields to the flame. The black calx tinges the fluxes of a bluish colour; borax, unless saturated, communicates more of a yellow colour. The colour may be gradually dissolved altogether by the interior flame, and again reproduced by a small particle of nitre, or the exterior flame alone. Combined with aerial acid, it is of a white colour, which changes by ignition to black. In other respects it shows the same experiments as the black calx.