CHEMICAL NEWS, }

Jan. 15, 1909

heavy gelatinous precipitate with ammonia which was readily soluble in excess of oxalic acid. The solution acidified with hydrochloric acid gave a very strong orangered colour with turmeric paper, from which it may be inferred that the bulk at least of the material was zirconia. If this is all zirconia it would amount to 151 per cent on the columbite. The matter which was brought into solution on the fusion with potassium carbonate was found to be a mixture of tantalic acid, niobic acid, and a little titanic acid; it amounted to o 4095 grm., equal to 2047 per cent on the mineral employed. Consequently the insoluble matter in this case was composed of :

Tantalic, niobic, titanic acids..
Zirconia (?)..
Silica ..

..

Total..

0'4095

0'3100 0'7005

I'4200

The resistance which zirconia offers when fused with potassium carbonate is so remarkable that it seems to afford a means of separating it from other bodies. To test this insolubility directly, I fused I grm. of (so-called) chemically pure zirconium hydrate with 4 grms. of potas sium carbonate for an hour at the highest temperature obtainable with a gas blast-lamp. On treating the fused material with water the aqueous solution was made slightly acid with hydrochloric acid, and ammonia then added in slight excess. No precipitate resulted. The insoluble zirconia was then gently boiled for four hours with hydrochloric acid and water in equal parts, keeping up the water from time to time. When this solution was filtered and a slight excess of ammonia added, there was a slight turbidity which in some hours deposited a few flocks of precipitate. These would certainly not weigh more than a milligrm. or two. Considering how exceedingly difficult it is to prepare really pure zirconia, it is even doubtful whether this trace of precipitate was really zirconia. On looking up the literature of zirconia, I found that Venables and Clark (CHEMICAL NEWS, lxxiv., 43) in their study on the zirconates had previously arrived at the same conclusions. It is possible that this insolubility of zirconia may be utilised in the very difficult problem of its separation from titanic acid; it certainly seems to answer in this respect with tantalic and niobic acids.

To recapitulate, I have endeavoured to show-(1) That it is more profitable to dissolve away the tantalic and niobic acid in tantalites and columbites by the action of potassium carbonate at a high temperature than it is to reverse the process, and to dissolve away the bases from the acids with potassium or sodium pyrosulphates.

(2) That by working in this manner in a reducing atmosphere, platinum vessels can be replaced by steel crucibles with advantage, and also that such metals as tin, &c., are by this means effectually removed in the first operation instead of requiring continual tedious and uncertain re-fusions with alkaline sulphides.

(3) That any zirconia appears to remain entirely with the small portion of insoluble matter left after the fusion has been treated with acid, whereas when potassium pyrosulphate is employed, it is dissolved and is likely to be con founded with the acids as Chandler states. Of course it

27

is not put forward as a quantitative process, but it certainly yields acids which are much purer than those obtained by fusions with bisulphates. Since the tin and similar metals unite in great part with the vessels used, it is impossible to estimate them even approximately. When it is desired to do this, I proceed as follows:-Fuse the finely powdered mineral in a platinum crucible at a high tem perature with three parts of pure potassium carbonate, extract all that will dissolve by digestion with a solution of citric acid at a gentle heat, filter and collect any insoluble matter on a filter, wash well, dry, and ignite it, then re-fuse it again with a smaller quantity of potassium carbonate, and treat again with citric acid solution. Everything now goes into solution except a little silica, zirconia, &c., which is filtered off, washed, and kept if necessary for further examination. Through the clear warm acid solution (which can be supersaturated with ammonia without causing any precipitation) hydric sulphide is passed to saturation, when the tin, antimony, &c., come down as sulphides. (By dissolving very small amounts of pure stannic and antimonious oxides in a large excess of citric acid, I could not trace that the presence of this acid impedes the precipitation). Filtering off the sulphides after washing, the solution, now free from heavy metals, can be used for the estimation of the tantalic and niobic acids as well as for the bases after the destruction of the citric acid.

With regard to the estimation of niobic acid in company with tantalic acid, I mentioned in a former paper (CHEMICAL NEWS, xcv., 1) some peculiarities observed when these acids are brought into solution with oxalic acid or oxalates. I have spent much time in endeavouring to utilise these reactions as a means for their separation, but I regret to say without any useful result. When they are associated the acids do not behave in the same manner as they do separately. At the time this prior paper was written, I was unaware that Fuss (Zeit. Anorg. Chem., xxxi., 42) had previously studied these oxalates, but he too comes to the conclusion that "The separation of tantalum and niobium by means of the complex oxalates cannot be effected." In my previous paper I also mentioned that I found that the hydrated tantalic and niobic acids can be brought into solution with phosphoric acid, and I showed that when such solutions were treated with zinc dust the niobic acid yielded intensely brown or black solutions. I have since noticed that these deeply coloured solutions are very much more permanent than those obtained with oxalic or other acids, and I have endeavoured to estimate the niobic acid by filtering the solutions in phosphoric acid through a column of zinc dust or spongy electrolytic zinc, receiving the deeply coloured niobous phosphate in a solution of ferric sulphate, in which the reduced iron is afterwards estimated by permanganate. Some difficulties in the manipulation of this process have been encountered, but an apparatus has been recently contrived by which the solutions can be digested with the zinc as long as may be desired, and finally filtered without any exposure to the air. When these experiments are concluded I hope in a further article to give an account of them. I believe that these steel crucibles, protected from oxidation in the way I have described, may find useful applications for opening up other minerals such as rutile, zircons, beryl, monazite, and zenotime.

3

Royal Institution.-On Tuesday next, January 19, at o'clock, Prof. Karl Pearson begins a course of two lectures at the Royal Institution on "Albinism in Man"; on Thursday, January 21, Prof. J. O. Arnold commences a course of two lectures on "Mysteries of Metals"; and on Saturday, January 23, Prof. Sir Hubert Von Herkomer delivers the first of two lectures on (1) "The Critical Faculty," (2) "Sight and Seeing." The Friday Evening Discourse on January 22 will be delivered by Dr. Alfred Russel Wallace on "The World of Life as Visualised and Interpreted by Darwinism," and on January 29 by Colonel Sir Frederick L. Nathan on " Improvements in Production and Application of Gun-cotton and Nitro-glycerin."

THE NATURE OF CHEMICAL CHANGE.*

By HENRY E. ARMSTRONG.

"That which is far off and exceeding deep, who can find it out?"Ecclesiastes, vii., 24.

p. 233.

"Le plus grand déréglement de l'esprit est de croire les choses parce qu'on veut qu'elles soient."-La Vie de Pasteur: VALLERY-RADOT, NOTHING is more surprising than the apparent unwillingness of chemists to formulate a consistent and comprehensive theory of chemical change: the text-books are silent on the subject. Whatever service- and it is not inconsiderable-the ionic dissociation hypothesis may have rendered, it has not given us such a theory: its advocates tell us merely that, in the case of electrolytes, action takes place between the so-called ions, yet only on dry land as it were-on leaving the bath; what happens in the case of non-electrolytes we are not informed. Such a conclusion is at best little more than a statement that the action is between the acting units-a fairly evident proposition; of the process we learn nothing. Unfortunately phrases and phases have taken the place of clear ideas in our text-books and every schoolboy prates of ions nowadays. I am tempted to apply Wordsworth's words to the situation:

--

"No single volume permanent, no code,

No master spirit, no determined road
But equally a want of books and men."

In replying to the discussion which followed this communication, I took occasion to animadvert upon the lack of chemical feeling displayed by the adherents to the physical school and drew attention to the need of once more cultivating the use of fingers in the laboratory, remarking that we must have practical and not paper chemists if we were to regenerate our industries and to play the part the President of the Section had advocated in his Address. I mentioned that prominent representatives of industrial chemistry in Germany, in discussing the situation with me recently, had deplored the evil results which had followed from the unbalanced development of so-called physical chemistry, leading, as this has done, to the neglect of the practical side and the substitution of an off-hand attitude of superiority for that of careful unbiassed inquiry so characteristic in days gone by of the German school. The effect on the younger generation is disastrous, Paucity of judgment will only be recovered when this is admitted. It is essential that we should recognise that "physical chemistry" is at best only a very minor branch of our subject and that the special prominence which has been accorded to it of late years is, after all, largely the consequence of bold advertisement. Nowhere, in recent years, has the uncompromising worship of the cult of the ion-the elevation of the ion into the position of an iconbeen more fashionable than in the United States of America almost every text-book is devoted to the display of ionic rites, so that for years to come it will be useless to pray that youth be delivered from temptation.

Surely it were time that we cleared our minds of cant and set to work to introduce an element of philosophy into our science that we swept aside the jargon which now disfigures our literature and substituted honest straightforward statements of fact or clear admissions of ignorance for the specious illusions which have too long been foisted upon the unwary student.

I venture to think that chemists need to be freed from the control of the pseudo-mathematical-physical speculations to which they have heedlessly subjected themselves of late years; that they need to give clear expression to that sense of feeling and knowledge of fact which is theirs and theirs alone in virtue of contact with actual materials in process of change. The speculations of the mathematician are very properly often guided by pure fancybut chemists are bound to be realists. Our attitude too is

The introduction to a discussion on the subject in Section B Chemistry) at the meeting in Dublin of the British Association for he Advancement of Science.

very different from that of the physicist, who is concerned mainly with the mere gambols of molecules whose internal structure and interactions it is our province to study. Physicists appear to have no conception of the depths to which we have penetrated nor of the certainty of not a few of our methods, a certainty due to the fact that we are often able to pile up odds to such an extent that the formal correctness of our explanations becomes almost unquestionable. We need to cast off our subserviency to mathematicalphysical speculation. The physicist is rightly prepared to give rein to his fancy and to propound hypotheses to the th degree of improbability merely in order that he may be able to give mathematical expression to his results. It is his way of recording as well as of advancing his position. We, however, are in no manner called upon either to be misled or to be carried away by the apparent agreement of hypothesis with fact when expressed in mathematical form. We have only to remember that there is an infinite power in mathematical expressions of cloaking ignorance as well as of summarising knowledge; that the same expression may be applicable to cases in which the operations are quite diverse in character or vice versa. Wendell Holmes must have had premonition of the reception that was to be accorded to the ionic dissociation hypothesis when he wrote the lines:

"That boy with the grave mathematical look
Made believe that he had written a wonderful book
And the ROYAL SOCIETY thought it was true!
So they choose him right in; a good joke it was too!"

-The Professor at the Breakfast Table. However much others may contemn our chemical feelings and our pedantic regard for facts in opposition to mathematical "let it be granted" fiction, let us not forget that it is our business to dissect and display the inner meaning of the phenomena of chemical change. We have been far too generous in allowing well-meaning speculators, who have in no way been conversant with the facts generally, to dictate a policy to us: it is to be hoped that we shall now once more take the control of our affairs into our own hands.

Since 1885, when I first brought the matter before the Chemical Section of the Association in my Address from the Chair, I have consistently maintained that the generalisation upon which we should base our conceptions of the nature of chemical change is that postulated by Faradaynamely, that chemical affinity and electricity are one and the same force. If this view be adopted, it follows that the conditions operative in electrolysis are equally operative in all chemical interchanges. The important step taken by Arrhenius in 1883 was the discovery of a practical method which appeared to correlate chemical with electrolytic activity.

It is noteworthy, however, that as far back as 1878, Ayrton and Perry contended that the electrical law of Ohm is the chemical law-or as they express it: "the quantity of chemical action in unit time equals the sum of a great number of terms, each of which is an electromotive force divided by a resistance." All that we know is in accordance with this view.

The dissociationist school, following Clausius, always contend that the apparent fact that any electromotive force, however small, will produce sensible electrolysis in the solution of an electrolyte is complete proof that free ions

*Chemistry and physics are necessarily interdependent disciplines -it is impossible to be a chemist without also being to some extent a physicist, although apparently the practice of physics is compatible with a complete disregard of chemistry. Chemistry did not become a science until it availed itself of the balance. Sooner or later, all properties must be quantified if an exact expression is to be given of their value; but the introduction of one or two new methods of measurement cannot be held to justify the treatment of measurement work as a separate discipline. Chemistry is a single science - the exclusive cultivation of any of the sections into which it may conveniently be divided must always conduce to narrowness of purview. The worker who is generally well informed and who applies his wide knowledge to the development of some special subject is the true specialist; such men are urgently required at the present day to restore the sense of proportion and to promote once more the development of the comparative and critical spirit among us.

are present in solution and that as these are transported by the current others are liberated spontaneously and take their place. I have always maintained that this interpretation should not be put on the facts. The experiment quoted by Helmholtz in his Faraday lecture, on which reliance is placed, is not a valid proof, as the means used to remove oxygen from the liquid (viz., a third electrode of palladium charged with hydrogen) could not effect this object completely and some hydrogen would necessarily pass into solution, otherwise there would be no equilibrium; the inevitable consequence would be that the electrodes would remain more or less polarised. I even venture to think that the Helmholtz atomic charge hypothesis is entirely open to question. We have been taught to think of hypothetical simple ions-free ions—as carrying the charges; but in point of fact the bodies we charge are always highly complex viscous electrolytes of low conductivity; it may therefore be questioned whether there be any proof that individual ions can be charged, whether it be not more probable that the charge is always carried by a complex system.

The conditions in a solution are certainly by no means simple; in fact, it is little short of impossible to avoid the conclusion that behind the apparent simplicity of Faraday's law there is probably a give-and-take process at work of which no account can be rendered, the summation result of which alone has been taken into account in framing the hypothesis.

The atomic charge hypothesis, moreover, is not in accordance with our conceptions of valency. Thus in a series of oxides taken in the order of their heats of formation, commencing with those in the production of which but little heat is evolved, such as silver oxide, heat is developed if the metal in any one of the oxides be displaced by that of the oxide next below it in the series. If the two charges of the oxygen atom be given up in the formation of the initial term of the series, whence-it may be asked-is the energy derived which is liberated each time on passing to an oxide having a higher heat of formation? It cannot well be supposed that the oxygen remains a non-contributor and that the energy is derived from the metal alone; whatever the nature of the process, metal and oxygen are in some way reciprocal agents. In like manner, the properties of water are incompatible with the assumption that the two single charges of the two hydrogen atoms simply neutralise the two charges of the oxygen atom. Physicists have never attempted to deal with facts such as these.

The conception of a definite "valency volume" recently introduced by Barlow and Pope may well prove to be applicable to the problem: it is conceivable that the volume of material displaced in electrolysis is in some way proportional to the power of the displacing agent.

The majority if not all of the results arrived at by the application of the ionic dissociation hypothesis are independent ot the fundamental premises which underlie it and depend merely on the recognition of the fact that the order in which electrolytes exercise their chemical activity is practically the order of their activity as electrical conductors in an electrolytic circuit. Any hypothesis which would satisfy this relationship might take its place; indeed, for many purposes of calculation, it is probably unnecessary to go further than to assume that it is established and

to make no hypothesis in explanation of the fact; whilst in cases in which it is necessary to go further, it is prob able that the phenomena are by no means so simple as is supposed and that conclusions based on the application of the hypothesis cannot be accepted even provisionally. The fact that discussion has been confined almost entirely to weak solutions has been a most fertile source of misconception: when all degrees of concentration are considered, results are arrived at which are by no means such as should follow from the premises adopted. Comparing, for example, electrical conductivity with hydrolytic activity although the order of activity of a series of hydrolysts is that of their activity as electrolytes, in the one case (hydrolysis), there is a decrease, in the other (electrolysis) an increase of “molecular " activity as the concentration is diminished; furthermore, when nitric is compared with chlorhydric acid, whereas the hydrolytic activity of the nitric is always inferior to that of chlorhydric acid at all concentrations and the more so the weaker the solutionin the case of conductivity, in moderately and very dilute solutions chlorhydric acid is a better conductor than nitric acid but in concentrated solutions it is a worse conductor, the difference becoming the more pronounced the stronger the solution. The values given in Table I. have been obtained by Mr. Wheeler and myself in a set of preliminary experiments.

There is a well-known adage that you cannot have your cake and eat it if conductivity and hydrolytic activity were both properties to be referred to the operations of dissociated ions, they should run not only on more or less parallel lines but also in similar directions: in point of fact, they run in opposite directions; it is rational, therefore, to assume that the two processes are essentially different in character, not similar as the dissociationist school would have us believe.

The Faraday theory of chemical change, as I propose to term it, involves the assumption that the conditions operative in a voltaic cell must be realised before any change can take place-that is to say, that a conducting system must be established consisting of at least three components; no less a number, I imagine, will afford a slope of potential. One of the components must be an electrolyte of the two remaining members of the system, the one must be a substance-a metal, for example-with which the negative radicle of the electrolyte can be associated; the other may be either active or neutral (in the chemical sense) towards the positive radicle of the electrolyte. The only difference between the case of a voltaic battery and that of a chemical change taking place in a fluid mixture without electrodes is that in the battery conducting electrodes or feelers are introduced which enable us to tap the circuit and utilise the energy set free in the interactions. In a fluid medium, this energy is frittered down into heat in any case, our chance of being able to utilise the energy of chemical change as electricity depends on our ability to interrupt the circuit by the interposition of conducting terminals.

The remarkable results arrived at by Dixon and by Brereton Baker with which, it may be supposed, all are familiar,* have always appeared to me to afford complete

* It is noteworthy that they are entirely disregarded by the ionic dissociationist school.

Justification of the above conclusions. Baker's observations show that liquid water alone does not promote the interaction of hydrogen and oxygen gases; change only takes place when impurity is present-that is to say, when the water becomes a composite electrolyte. Larmor, in his recent Wilde Lecture, has dwelt on the probability of encounters taking place between pairs of the different molecules rather than between any greater number of molecules in a mixture of gases. Í venture, however, to think that the experimental evidence is of so convincing a character that it may be affirmed that whatever the statistical probability of an effective meeting may be, the mating of the hydrogen and oxygen molecules is neces sarily dependent on the advent of a suitable composite electrolyte so that the patience of the molecules within the mixture must be exercised until proper opportunities occur for the interchange of affections-i.c., for affinity to operate; probably no great demand is made, because of the almost infinite rapidity with which molecular motion is propagated in gases, especially under compression. From the point of view here advocated chemical interchanges are essentially all associative processes and their occurrence is dependent on the operation of a catalyst. But of late the doctrine has been promulgated that a catalyst is a substance which merely accelerates change not one which directly conditions change; that the actions which take place more or less rapidly under the influence of catalysts also take place without them but so slowly that their occurrence cannot be detected in a measurable time. I venture to question this. Take the case of canesugar. Does anyone who has really worked with and learnt to appreciate this substance believe that any change would take place if the pure compound were dissolved in pure water and the solution were preserved in a clean vessel and no acid impurity were allowed to gain access to

it ? And yet a trace of acid would almost immediately

condition a perceptible change in such a solution.

In solution, probably, the sugar is to some extent combined with water and certainly the water must be in intimate contact with its molecules: why then does not water act to an appreciable extent-why does acid produce Because there are so few hydrogen ions free in water;* and that the acid acts by increasing the proportion of hydrogen ions. But to what extent can a trace of acid be supposed to have this result? Its effect is altogether out of proportion to the extent to which, ex hypothesi, it can be supposed to furnish hydrogen ions.

such an effect? The dissociationists will answer :

But it may be and I contend has been demonstrated that hydrogen ions are not the effective cause of hydrolysis-in fact, the selective action of enzymes is incompatible with the ionic explanation. The effects produced by enzymes are in all respects comparable with those produced by acids, so that if the action of acids be exercised not by the acid molecules as wholes but by hydrogen ions liberated from them in solution, enzymes, in like manner, might be supposed to contribute hydrogen ions, in which case, since acids generally act on cane-sugar, enzymes generally should effect its hydrolysis; in point of fact, however, only one enzyme is known which has the power (invertase).

THE WIDE DISTRIBUTION OF SCANDIUM
IN THE EARTH.
By Prof. G. EBERHARD.

Up to the present scandium has been numbered amongst the rarest of the elements occurring on the earth, so that but little is known of it, in spite of its obviously very interesting chemical properties. In fact, since the experiments of Nilson and Cleve, who obtained a few grms. of a scandium oxide which was not quite pure but still contained some ytterbium,* further work upon this element has not been published, undoubtedly only because of its great scarcity, while, moreover, the working up of the expensive minerals which are known to contain scandium, and which do not occur in great quantity-gadolinite, yttrotitanite, euxenite-by uneconomical and uncertain methods (e.g., fusing the nitrates), is a very tedious and troublesome process. Thus, according to the statements of Cleve (Comptes Rendus, 1879, lxxxix., 419) and Nilson (Ber., 1880, xiii., 1439), the three above-named minerals contain only 0.001-00015, 0'0005, 0.02 per cent Sc2O3 respectively. Another difficulty is one which I encountered, namely, that euxenites from different sources do not always contain scandium, and, moreover, of gadolinites only that from Ytterby appears to contain it.

If it were concluded correctly from these facts that scandium is to be regarded as one of the rarest elements occurring on the earth, it would be all the more astonishing that outside the earth it undoubtedly occurs in other heavenly bodies in abundant quantities. Rowland, in the with those of known terrestrial elements, was able to detect identification of the Fraunhofer lines of the sun's spectrum with certainty some of the strongest scandium lines, and, moreover, the scandium lines appeared strongly in the this element, even the faintest, have been found with spectrum of the sun. At the present time all the lines of absolute certainty in the solar spectrum.

Moreover, not only in the solar absorption spectrum, but also in the emission spectrum of the sun's atmosphere (flash spectrum), seen for a few seconds during total solar eclipses, the strongest scandium lines have been recognised amongst those of the few elements occurring there. There can thus be no doubt that scandium is present in relative abundance in the sun.

The same is true of the stars.

By examining their spectra it is found that the scandium lines appear plainly, and not only in those stars which resemble the sun. As soon as a star has advanced so far in its development that the number of lines in its spectrum is large (Vogel's Spectral Class I.a) the lines of scandium appear, generally very clearly. As an example, I may mention the star a-Persei, which has not yet reached the stage in which our sun now

is.

Also in the red stars, e.g., a-Orionis and a-Herculis (Class III.a) which have long passed the state of the sun,

the scandium lines are still visible and unaltered.

From the first it seemed clear to me that there cannot

The effects produced by carriers, the use of which is so familiar to workers in organic chemistry, may be explained

in a similar way.

(To be continued).

* The conclusion, based on Kohlrausch's observations, that there are free ions in pure water is quite illogical: the experiments do not justify it and it is impossible to admit that pure water has ever been examined or ever will be.

minerals.

CHEMICAL NEWS,

Jan. 15, 1909 method.

As it was evident that this element would occur in a state of great dilution in the crust of the earth, I first tried to obtain information about the sensitiveness of the spectral reaction of scandium, so as not to work in vain. As I had no scandium at that time, after thorough practical study of the chemistry of the rare earths, I chose, to settle the question, one of those minerals which are known to contain scandium. When o'i grm. of the oxides of two different yttrotitanites (Nos. 247 and 248) were vaporised in the arc, both showed very plainly the principal scandium lines. They were also still plainly visible after I had diluted the oxides to one-tenth the strength with yttrium earths free from scandium, and again vaporised o'i grm. of this preparation. As according to Cleve the oxides of yttrotitanite contain o'005 per cent Sc2O3, the spectral reaction of scandium must be regarded as extraordinarily sensitive, even if the yttrotitanite oxides contain ten times as much scandium as Cleve states, which, according to my experience, seems to be the case. In any case, on the ground of this experiment, it seemed very promising to proceed to the spectrographic examination of minerals for scandium.

I first used minerals in which, according to the experiments of Nilson and Cleve, scandium might be supposed to occur, euxenite (Nos. 214 and 217) and gadolinite (Nos. 226 and 227) without, however, detecting this element. This was the case when I examined a piece of gadolinite from Ytterby, most kindly sent to me by Dr. Benedicks (Upsala), but here I observed phenomena which surprised me, and which led me to perform further experiments. After three extractions of the very finely divided mineral, the unextracted part contained considerable amounts of alumina and beryllium earth. (All the gadolinites examined by me contained beryllium earth, in spite of the statements to the contrary in literature). Moreover, the scandium lines appeared in the arc not much fainter than in the part which had gone into solution, while the lines of the rare earths, and especially those of yttrium, had been much weakened. This behaviour of the unextracted part led me to suppose that the felspar-like matrix adhering to the gadolinite, which I had not removed in the working up of the mineral, and which cannot be extracted with acids, must be a silicate of alumina containing beryllium and scandium, for pure gadolinite would be completely extracted by the three processes.

To test this supposition, I asked Dr. Benedicks for specimens of the matrix rocks of Ytterby gadolinite, and meanwhile investigated another beryllium alumina silicate, a smaragd (No. 25) which I happened to have. It contained easily detectable quantities of scandium, and, moreover, the other rocks found in the Ytterby mine, felspar, mica, and mica-schist, contained scandium, the last two to a considerable extent. Thus, for the first time it was proved that scandium might occur in other minerals as well as in those of the rare earths, and simultaneously the direction in which further search for scardium should be made was indicated. It was found that this element was present in a series of beryllium minerals and of micas. Among the micas tested, zinnwaldite from Zinnwald in the Ore Mountains contained specially large amounts of scandium, and when I examined whether other minerals from Zinnwald also contained scandium I found a great number contained this element, among them tinstone (SnO2) and wolframite, which occur in large quantities and are rich in scandium.

But if micas contain scandium, rocks of which mica (especially biotite) forms an essential constituent, e.g., granite, gneiss, mica-schist, &c., must also contain scandium. This conclusion I also confirmed, thanks to the extraordinary spectral sensitiveness of scandium in the great majority of cases, and I now undertook the examination of as many different kinds of minerals and rocks as I could obtain from all possible places upon the earth, to see if they contained scandium, in order to acquire an adequate knowledge of the occurrence of this element, which had hitherto been thought to be so rare.

31

Before I give the results obtained I will make some remarks upon the details of the experiments. The minerals of the rare earths, especially the titanates, niobates, &c., give a spectrum which is so extraordinarily rich in lines that they must be worked up chemically before their spectra are photographed; i.e., must be decomposed into their chief constituents. (Prof. R. J. Meyer, Berlin, very kindly performed for me in his laboratory part of the very tedious and lengthy extraction processes. This renowned authority upon the chemistry of the rare earths often gave me valuable advice upon the further working up of the raw rare earths, and I am glad to take this opportunity of expressing my thanks to him). The part which could be extracted with acids was first separated from the non-extractive part, and the former was then further separated by treatment with oxalic acid into a part which was precipitated by this acid, and a part which was not precipitated by oxalic acid but gave a precipitate with ammonia. This precipitation of the remaining liquors with ammonia was always necessary, as scandium oxalate is exceedingly soluble even in weak mineral acids, such as the extraction always contains, and thus a part of the scandium remains in the liquid after precipitation with oxalic acid. The rare earths precipitated with oxalic acid were subjected to many other processes (precipitations, fractional crystallisations) to concentrate the scandium, but I will not now go into the details of these operations.

The preparation of other minerals and rocks was essentially simpler. They were first finely powdered and then heated to a bright red heat for some time in a porcelain crucible to remove the gases and water contained in them. If this preliminary treatment is neglected unpowdered particles spirt with little explosions, and powdered pieces crumble up as soon as the arc is started. All preparations were vaporised with the same strength of current so as to obtain spectra under the same conditions, and a comparatively strong current was chosen 20 A. at 120 volts), because some minerals, e.g., quartz, zircon, bauxite, &c., are thoroughly vaporised only at high current strengths. The vaporisation is carried out in ordinary somewhat hollowed out arc lamp carbons, as with currents between 5 and 40 ampères I could not, with the rods of far purer Acheson graphite given me by Prof. Muthmann (Munich), get anything but a very strongly hissing, unsteady, and easily interrupted arc. Two precautions are so important for taking the photographs that failure usually follows their neglect. First, large quantities of material (in my experiments about o'5 grm.) must be vaporised, as scandium mostly occurs only in extremely small amounts in the minerals, and only when large amounts of material are used are its spectral lines visible (in the photographs. But when such large quantities of substance are vaporised on the arc carbon, generally a fairly bright continuous spectrum appears, which would completely mask the faint scandium lines. Therefore a spectrograph with very large dispersion must be used to efface the continuous spectrum sufficiently. I took the spectra with a concave grating apparatus of the observatory (Zeitschrift für Instrumentenkunde, 1905, xxv., p. 371) and by means of it could practically completely suppress the continuous spectrum.

The second condition necessary for the success of the experiment is that the substance put in the arc carbon must be completely vaporised until all spectral lines disappear, which can easily be seen by observing the arc with a good pocket spectroscope. The vaporisation of rocks in the arc corresponds to a fractional distillation, the greater part of the most volatile constituents (e.g., the alkalis) vaporises at the beginning of the process, while most of the difficultly vaporised constituents, to which scandium belongs, vaporise quite at the end. If then a large quantity of mineral were put on to the arc carbon, and the photographs of the spectrum were taken as soon as a small portion or the substance had vaporised, no indication of the less volatile elements (e.g., Sc, Zr, Th, Ta) would be obtained in the resulting spectrum if they