The Blowpipe Vade Mecum. The blowpipe characters of minerals: deducted from the original observations of Aquilla Smith. Alphabetically arranged and edited by ... S. Haughton and R. H. Scott

Preface

The following Tract contains — A Sketch of the History and Use of the Blowpipe ; such characters of minerals as can be ascertained by the use of a penknife and blowpipe ; and a new blowpipe arrangement of Irish Minerals. We have adopted the alphabetical arrangement, as being the most useful to travellers and others using this work as a Mine ralogical Vade Mecum, and have carefully verified Dr. Smith's original observations in very many instances. The name of the same mineral is frequently repeated, as it has been found that the blowpipe characters of these minerals vary with the locality in which they are found. The Collection of Minerals on which these observations were made was very extensive, and we believe that the present work is a most valuable addition to British Blowpipe Literature — [Eds.]

Introduction

. HISTORY AND USE OF THE BLOWPIPE. The Blowpipe is an instrument by means of which the flame of a lamp or candle may be concentrated, so as to communicate a very intense heat to small bodies placed within the flame. Although this instrument was employed in the arts by the ancient Egyptians about 1500 years before our era, and in more modern times has been used for various purposes, particularly by goldsmiths and jewellers in the soldering of metals on a small scale, whence it derives its name in the German language, "Lbth rohr," from "Lothen" to solder, and "rohr" a tube or pipe, it is scarcely more than a century since the idea of applying it to mineralo gical purposes was conceived. The accompanying woodcut is taken from Rosellini, and represents an Egyptian silversmith using the Blowpipe.

It was found in a Theban tomb, in conjunction with representations of workers of gold. The following description of this remarkable figure is given by Rosellini : — "L'artefice sta seduto dinnanzi ad un fornello posto in una vasa di terra, nel quale, mentre soffia con un tubo di canna armato in cima di B

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. metallo per difcsa dal fuoco, sembra prcndere o aggiustar colle molle la matcria che fonde, o che arroventa. A' suoi pede e figurato un mucchio che par d' argilla, della quale usano i fondatori de' metalli, o per forme, o per altre bisogne dell' arte loro."— Rosellini. I Monummti delP Fgdto e della Nubia. Parse seconda. Monummti Civili. — Tom. ii., p. 292 ; Tavola lii, fig. 4. Bergmann informs us that, about the year 1738, Andrew Swab, a Swedish metallurgist, and Counsellor of the College of Mines, was the first to employ this simple and elegant instrument for the purpose of assaying metallic minerals. He, however, left no work on the subject, and it is unknown to what extent his researches with this instrument were carried. The subject does not appear to have received any particular at tention from any one until Cronstedt, a Swedish nobleman, in 1758, pro posed his system of mineralogy, in which the arrangement is dependent on the chemical composition of the minerals.

In order to recommend the general adoption of his system, it became to him a matter of great import ance to possess some ready and simple means of determining the consti tuents of mineral bodies, as it was evident that the slow and laborious operations of chemical analysis could not be generally employed by mine ralogists. He found the object of his pursuit in the Blowpipe; and by the employment of fluxes in the experiments performed with this instrument, he may be considered as the founder of a new mode of investigation in chemical science. He used the Blowpipe to distinguish mineral sub stances from one another, by the means of fusible reagents, whose actions should produce such modifications on the objects to which they were ap plied as might afford some conclusions respecting their composition, and serve as a basis for the classification he adopted.

He carried the use of the Blowpipe to a degree of perfection that could only have resulted from the most persevering industry. The results obtained by him are to be found in the first edition of his " System of Mineralogy," published in Sweden, in 1758, a translation of which into English, by his pupil, G. von Engestrom, was published in 1765. The last edition is that by J. H. de Magellan, 2 vols., 1788. The employment of the Blowpipe, being thus brought into notice, excited the attention of chemists and mineralogists to the use of the in strument, who, however, derived little advantage from it, except as a means of ascertaining the fusibility of bodies, and occasionally their solubility in borax ; for the want of skill in its application, which can only be acquired by patience and practice, prevented a just estimate of its value being formed.

In Sweden, however, it appears to have been cultivated with the greatest success; and it is. to the chemists and mineralogists of that country that we arc indebted for the greater portion of the information we possess on this subject, particularly to Bergmann, Gahn, and above all to Berzelius. Bergmann extended the use of the Blowpipe by a series of original researches, in which he investigated the properties of most of the then known species of minerals, and applied it to the field of inorganic che mistry, in discovering very minute portions of metallic matter in analytic researches ; and published the result of his observations at Vienna, in 1 779, in a treatise under the following title : " De Tubo Eerruminatorio, ejusdemque usu in explorandis Corporibus, præsertim Mineralibus ;" a translation of which into English will be found in the 2nd vol. of Bergmann's Physical and ChemicalEssays, by Dr. Edmund Cullen, Lond., 1788.

The close and continued application whiehBergmann bestowed on his studies had such an effect on his health, as to oblige him to continue his philosophical pursuits with the help of an assistant. He accordingly em ployed Assessor Gahn, wjio performed, under his directions, a series of operations on all the minerals then known, by which he was taught in what manner each individual conducted itselfbefore the Blowpipe. The experience thus acquired enabled Gahn to employ the instrument in every kind of chemical and mineralogical inquiry; and he attained such a degree of skill in its use, that he could detect the presence of substances in a body by its means, which had escaped the most careful analysis, conducted by the ablest chemists of those times. Gahn was indefati gable in his observations and experiments with the Blowpipe, without which he never travelled; and though he wasted to contrive several im provements in its application, which were imagined and executed with such sagacity and precision that his results were entitled to the greatest confidence, — he appears never to have thought of publishing an account of his labours, which no doubt would have been of great importance.

As an instance of his power of detecting the presence of metallic bo dies, we are told by Berzelius that he had often seen him extract from the ashes of a quarter of a sheet of paper distinct particles of metallic copper, and that too before the knowledge of the occurrence of this metal in vegetables was known, and therefore before he could have been led from this circumstance to suspect its presence in paper. Although we cannot but feel regret at having received no work from a man so eminently qualified to instruct on this subject as Gahn, still we must consider it fortunate, that, under such circumstances, the know ledge and experience of so long and laborious a life has not altogether been lost. Fortunately for science, accident, as it were, made Berzelius the medium through which this information was to be communicated to the world, and it must be universally felt and acknowledged that he has most ably fulfilled the task assigned to him.

The zeal and assiduity of Gahn in this study, together with the circumstances to which we are indebted for the preservation of his labours, are told in an interesting manner by Berzelius, in his treatise on the Blowpipe. Such, then, is the origin of Berzelius' treatise, a work which has been acknowledged as the highest authority on this subject by almost every writer on mineralogy, for the last 20 years. An English translation of the French edition, by M. Fresnel, was published by Mr. Children in 1822. We have now given as full an account of the rise and progress of the Blowpipe, in its application to mineralogy, as the nature of the subject

INTRODUCTION.

. will admit ; and before we conclude this part of our subject, we feel called on to show that the use of this valuable little instrument was not as much neglected in England as we might be led to suppose from an assertion made by Berzelius, at the close of his history of the Blowpipe:— "In all the rest of Europe only one naturalist, but he a very distinguished one, has applied himself to the study of the Blowpipe and its uses, and sub mitted a large number of mineral substances to its test: this was H. de Saussure." Some years previous to the publication of Berzelius' work, Mr. Arthur Aikin, the author of a Manual of Mineralogy, the second edition of which was published in London in 1 81 5, had arranged all mi neral substances according to their habitudes before the Blowpipe, yet it must be admitted that it was applied by him in a limited manner; for in many instances he only states the degree of fusibility of the mineral, and occasionally its colour after fusion, rarely noticing the minute dctailB which are so useful, as in many instances offering most satisfactory characteristics, particularly when the aggregate of the characters are taken into consideration.

And although Dr. Wollaston has never commu nicated his knowledge on this subject to the world, it is well known that he was eminently distinguished for his dexterity in managing this useful little instrument ; and in later times Mr. Children and the late Dr. Turner made many important discoveries respecting the use of re-agents with the Blowpipe. I. — Description of the Blowpipe. Blowpipes are of two kinds, simple and compound. A simple Blowpipe consists merely of a conical tube, generally made of metal, through which air is blown from the mouth of the operator. A compound Blowpipe consists of a tube through which common air or gas of some kind is blown by some secondary apparatus, to which the tube is attached. As our object is to simplify, as much as possible, the application of the Blowpipe to the purposes of the practical mineralogist, we shall only describe the one we have found to answer best, and for the descrip tions of the various kinds, both simple and compound, refer to the work of Berzelius, or the useful little manual " on the Use of the Blowpipe," published by Mr. Griffin of Glasgow.

The instrument we have always used is that invented by Dr. WoUaston ; it is made of copper, and consists of three pieces, two of which, when united, form the tube, about seven inches in length, the widest extremity of which constitutes the mouth-piece, and is plated, to prevent the disagreeable taste which copper would produce in the mouth of the operator. The third part, or nozzle, which when fitted on the smaller end of the tube forms a right angle with it, is sometimes constructed bo as to form an oblique angle with the tube, which, in our opinion, is not as convenient as the former. The nozzle is also sometimes made of platina. We have, however, used one of brass for some years, and it is as good now as when first it was made. This instrument is very light, so that the operator can, when occa sion requires, hold it steadily between his teeth while blowing, and enjoy the use of both his hands for a time, and for portability it far ex ceeds aU others; for when the instrument is not in use, the nozzle fits into the open extremity of the second piece, and the latter within the mouth-piece ; in this form its length is reduced to less than four inches, and it occupies no more room than a pocket pencil-case.

One inconvenience attends the use of this instrument, that is, the condensation of the vapour of the breath in the interior of the tube ; and contrivances have been made to obviate this, by attaching a hollow chamber to some part of the tube to collect the condensed vapour. In our opinion, this trifling objection, which can at all times be readily removed by inverting the tube or blowing forcibl}- through it, is not at all compensated for by the addition of the chamber, which adds considerably to the weight of the instrument. II. — The Combustible or Flame. A great diversity of opinion exists respecting the material which should be used to produce the flame for the Blowpipe : wax, oil, and tallow have been recommended ; we have always preferred a candle made of pure wax, about an inch in diameter, with the wick rather thick in proportion to the size of the candle ; it is far more cleanly than tallow or oil, burns with a clear flame, does not emit any disagreeable odour, and affords a heat sufficiently intense.

The candle should never be more than about six inches in iength; and we have found advantage in using a supporter made of tin plate, to the socket of which is attached a stem about three inches long, which is made to slide in a tube of the same length, attached to the foot of the supporter. By means of the sliding socket, the flame of the candle can always be kept at nearly the same elevation from the table, at a height most convenient to the operator. III. — Method of Blowing. The operation of keeping up a continued and steady stream of air througti the Blowpipe, simple as it seems, is difficult at first ; the whole artifice, however, consists in this, that while the operator breathes through his nostrils, he must blow the air contained in his mouth by the mere compression of the cheeks ; to accomplish which, the first thing to be done is to acquire the habit of breathing easily, and without fatigue, through the nostrils alone, while the mouth is filled and the cheeks in flated with air ; when this is acquired, the Blowpipe may be put into the mouth, and the confined air expelled through the tube by means of the muscles of the cheek.

As soon as the air is nearly exhausted, the ex piration from the lungs, instead of being made entirely through the nos trils, is to be partly forced into the cavity of the mouth : all subsequent supplies of air are to be introduced in the same manner as the first. Thus, with a little practice, the power may be obtained of keeping up a

INTRODUCTION.

. continued blast for as many minutes as may be necessary for any ordinary operation.* IV. — Of the Blast and Flame. Having accomplished the first object of keeping up a steady blast, the next requisite is to produce a good heat: this is best attained by keeping the wick of the candle of a moderate length, and avoiding all drafts or currents of air, which would render the flame unsteady. The point of the Blowpipe should be held just above the wick; and as soon as the blast is directed on the flame it will be observed to assume a conical form, and to consist of two parts, an outer and inner, the latter of a light blue colour, converging to a point at the distance of about an inch from the nozzle ; the former of a yellowish colour, and converging less per fectly. The most intense heat will be just at the point of the inner flame.

To attain the maximum degree of heat, we must neither blow too strongly nor too gently; and we should bear in mind that our pyrognostic operations are not confined to obtaining the highest possible tempe rature; other phenomena must be produced, which require a less intense heat. A very important point in pyrognostic assays is the power of producing at will the phenomena of oxidation and reduction, both of which are easily effected, although diametrically the reverse of one another. 1. Oxidation. — Oxidation goes on most actively at an incipient red heat; and the further we recede from the flame, the better the oxidation is effected, provided we can keep up a sufficient heat. The opening in the nozzle of the Blowpipe, we are told, should be larger for this ope ration than in other cases : however, we have always succeeded with the ordinary nozzle we use for all purposes; and which in this case answers very well, by holding it a little further from the flame. 2.

Reduction. — Reduction or de-oxidation is best effected in the brilliant part of the flame, immediately beyond the point of the inner blue flame, and it requires more expertness in the operator than the very simple process of oxidation. A very good mode of acquiring the art of making a good reducing flame is to fuse a small portion of tin on a piece of charcoal, so that its surface may always retain its metallic brilliancy : tin has so great a tendency to oxidation, that the moment the flame begins to become an oxidating one, it is converted into an oxide of tin, which covers the metal with an infusible crust. V. — Of the Support. The assay, or substance to be examined by the Blowpipe, must ne cessarily rest on a solid body, or be fixed in a steady position by some * It is generally supposed that it is a matter of some difficulty to use the Blowpipe— that it requires threat pulmonary exertion, and may on this account be injurious to the health.

Such, however, is not the case, as the experience of half au hour will convince any person, under the direction of a skilful teacher. means; and the material or instrument by which this is effected, is called the Support, of which there are two kinds, the combustible and incom bustible. 1 . Combustible Supports. The combustible support generally used is charcoal, and that prepared from the light woods in general answers best ; and as it is not always easy to obtain charcoal which possesses all the qualities, which it should possess, we shall detail the manner of pre paring such as we have found to answer very well. Take pieces of white pine-wood of a fine grain and free from knots, about six inches in length, and an inch or more square ; place them in a large common crucible, and cover them with fine sand ; then place the crucible in the centre of a strong fire, and leave it there until the wood is perfectly charred, which will take place in about an hour.

The crucible should then be removed from the fire, and allowed to cool slowly ; and when cold, the charcoal will be ready for use. When well prepared, it should be perfectly black, very Light, possess some lustre, and be easily broken across the grain ; that which splits, scintillates, smokes, or emits flame when heated, is not of good quality. Mr. Children recommends alder wood, as possessing all the necessary qualities to make good charcoal. Charcoal is chiefly used in the examination of the metallic ores when our object is to reduce them, because it attracts the oxygen from the oxide, and thereby accelerates reduction to the metallic form. The intensity of the heat may be greatly increased by making a cavity for the assay in the charcoal, and covering it with another piece of charcoal, which by reverberating the heat converts it into a reverberating furnace of great intensity.

Gahn* directs that a small hole should be made in the charcoal, and into this hole the substance to be examined must be put. The assay should be placed on the side of the charcoal, and not the end ; otherwise, the substance to be fused spreads about, and a round bead will not be formed. But Berzelius, in the following passage, gives us directions quite contrary (p. 31): — " In order to fix the flux to a point on the surface of the support, one of the ends perpendicular to the layers of the wood is to be chosen for its receptacle ; if placed on the section parallel to the layers, it woxdd spread over the surface." We have occasionally used both me thods, but prefer placing the assay on the side of the charcoal ; however, a little experience wiU be the best guide for the experimenter. 2. Incombustible Supports. — Platinum Wire.

The only incombusti ble substance used as a support which it is necessary to notice is platina, which, from the difficulty of fusing it even in a very high temperature, its malleability, and property of conducting heat very slowly, render it preferable to any other material. ■• Vide Thompson's " Annals of Philosophy," vol. xi., p. 40, on the Blowpipe, from a treatise on the Blowpipe by Assessor Gahn, of Fahlun, by Dr. Ure, as Mr. Griffin in forms us.

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. Platinum Forceps.— One of the greatest advantages of this instrument is, that it enables us to fix the object of experiment in a steady position ; and by this means a very minute fragment, which it would be impossible to keep fixed on charcoal, can be examined with great advantage. The chief advantage of this instrument is that it enables the operator to submit a mere fragment of a mineral to a high and uniform temperature, which could not be effected on charcoal, as the assay would be blown away the moment the jet fron the pipe would be directed on it. Hence we have found several minerals which on charcoal were apparently infusible, yet when placed in the forceps, and submitted to a welldirected flame, fuse without difficulty on the edge ; and besides it enables us to observe the effect of the assay on the flame, in producing certain colours which are very characteristic of some minerals, as Carbonate of Strontia andLepidolite, which tinge the flame red; Cyprine and Boracite, which impart a green colour.

The forceps may be used with advantage in the examination of all the earthy and many of the metallic minerals, particularly such as are refractory on charcoal. We should, however, be careful not to employ it as a support for those metallic oxides and compounds which are reducible per se before the Blowpipe, and readily form an alloy with platina. The forceps are used for holding a small portion of a mineral, when we wish to try its fusibility. The most convenient form of this instrument consists of two thin plates of steel, each having apiece of flattened platina about the sixteenth of an inch wide riveted on its extremity. The platina points should possess as little bulk as possible, in order that little heat may be abstracted. These plates are fastened in the middle to a small piece of iron or brass, somewhat of wedge-shape, so that the platina extremities are held in close apposition by the spring of the steel plates, while the other extremities are separated about a quarter of an inch, and may be used as an ordinary spring forceps.

The platina extremities are opened by pressing the fore-finger and thumb against two small buttons, the shank of each of which is fixed in one plate, and passes through the other. VI. — Additional Instruments. Under this head we arrange all those instruments which are used for various purposes, subservient to the examination of minerals. 1. The Common Steel Cutting Pliers — Is very useful for detaching small portions from a specimen, without the risk of injuring it by the concussion which would be caused by a hammer. 2. A small Jeweller's Hammei — Is also useful for detaching fragments for examination from specimens, and for ascertaining the mallea bility of the globules obtained from metallic minerals. 3. A small Anvil — Is used for crushing pieces of minerals, which are to be wrapped in paper, in order to prevent the dispersion of the fragments, and also for trying the maUeability of metals.

We have preferred a small smoothing-iron, the face of which has become black by oxidation, the advantage of which will be pointed out hereafter. 4. A Pocket Knife — With well-tempered blades, is an indispensa ble instrument for trying the hardness of minerals, which is estimated by the resistance they oppose to it. It may also be applied for the purpose of mixing a pulverized mineral in the palm of the hand with water or the fluxes. 5. A Small Triangular File — Is requisite to test the degree of hardness of such minerals as resist the knife, and also for the purpose of cut ting glass tubes, &c. 6. A Small Agate Mortar and Pestle — For the purpose of pulveriz ing the harder minerals, and separating minute metallic globules from the charcoal on which they have hardened; and a piece of pumice-stone should be at hand, to remove the traces left on the surface of the mortar by the trituration of metallic substances. 7.

A Pocket Microscope — Containing three glasses of different powers, which may be combined if necessary, is perhaps the most con venient. VII. — Of the Size of the Assay, and its Preparation for Examination by the Blowpipe. 1. Size of the Assay. — The fragment of the substance submitted to the Blowpipe for examination is termed the Assay, and it is a matter of the greatest importance in pyrognostic experiments that some definite size for the assay should be agreed on by experimenters. Mr.Mawe tells us that "the piece of mineral to be examined should not in general be larger than a peppercorn." Dr.Ure (Chemical Diet., art. Blowpipe) says that "it should notexceedthe size of half a peppercorn." Bergmann, however, with whom the specification of this bulk originated, observes " that we must often operate on smaller portions."

Von Engestrom recommends a piece about the size of a cube one-eighth of an inch on the side. Now, it may be safely asserted, that no correct or extended set of experiments on minerals with the common Blowpipe could be made on pieces nearly so large ; and that no person using the Blowpipe for the first time, could make any impression on a piece of that size, unless he happened to meet with a very fusible substance. It is probable that many persons (and I have known instances myself), have failed in thenattempt to use the Blow pipe, by using an assay of too large a size ; for nothing can be more evident, than that if the assay be large, a part of it must necessarily be out of the force of the flame, which is very small, and must therefore tend to cool the part immersed in the flame ; the consequence of which is, that the heat is carried off, and the operator will be tired before the assay is in the least affected, unless it be very fusible indeed.

Mr. Aikin, who published his Manual of Mineralogy in 1813, was the first who perceived the necessity of operating on pieces of very small bulk ; and recommends that the size of the assay " should scarcely exceed the bulk of a, pin's head," which is perhaps as good a type of the size as could be given. c

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. Berzelius says, " As to the size of the morsel operated on, it is large enough, if we can distinctly see the effects produced on it ; and we are more likely to fail in our object by using too large, rather than too small a piece ;" and adds, that " a piece of the size of alarge grain of mustard seed is almost always sufficient," and that " the only instance in which it may be convenient to operate on portions larger than a mustard-seed is when we wish to extract metals, because in that case we obtain a larger portion of the metal sought for, which may consequently be examined and distinguished with greater ease." In the first experiment the assay should never exceed the size as signed by Aikin; for unless we attend particularly to this, we can never arrive at uniform results, or institute comparisons which would be of any value.

There are many minerals which, if used the size of a peppercorn, which has been recommended by most authors, would be alto gether infusible by the means we adopt, yet a small fragment of the same substance will be fused without any difficulty. When we have ascertained that a mineral is easily fused, it is often desirable to operate on a larger piece in metallic minerals. If we find a fragment infusible in the first attempt, we should select another with a thin edge, and sub mit it to the most intense heat we can produce ; and in this way we sometimes succeed in fusing the thin edge of an assay which, under other circumstances, might be pronounced infusible : in such cases we should always examine the edge of the assay with the microscope. Minerals sometimes occur in very minute grains or pulverulent (aslserine) which cannot be held in the forceps ; and if they cannot be retained on charcoal, the only mode of proceeding then is to reduce them to powder, and form it into a paste with a little water in the palm of the hand, and then place it on charcoal, when in some cases it will form a cake, which may then be held in the forceps, if necessary. 2.