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(H+Ca+Mg H+Ca+Mg+Na+ Fe Mg+Na+ Fe+Bi+Hg
the new hypothesis, to be of any value, should present us with a state of things in which basic molecules repreindi-senting bases of the so-called elements should give us their lines, varying in intensity from one condition to another, the conditions representing various compoundings. Suppose A to contain B as an impurity and as an element, what will be the difference in the spectroscopic result?
Following out these views, I some time since communicated a paper to the Society on the spectrum of calcium, to which I shall refer more expressly in the sequel. Differentiation of the Phenomena to be Observed on the Two Hypotheses.
When the reductions of the observations made on metallic spectra, on the hypothesis that the elements were really elementary, had landed me in the state of utter confusion to which I have already referred, I at once made up my mind to try the other hypothesis, and therefore at once sought for a critical differentiation of the phenomena on the two hypotheses.
Obviously the first thing to be done was to inquire whether one hypothesis would explain these short line coincidences which remained after the reduction of all the observations on the other. Calling for simplicity sake the short lines eommon to many spectra basic lines,
A in both cases will have a spectrum of its own; B as an impurity will add its lines according to the amount of impurity, as I have shown in previous papers. B as an element will add its lines according to the amount of dissociation, as I have also shown.
that, with gradually increasing temperature, the spectrum The difference in the phenomena, therefore, will be of A will fade, if it be a compound body, as it will be increasingly dissociated, and it will not fade if it be a simple one.
Again, on the hypothesis that A is a compound body, that is, one compounded of at least two similar or dissimilar molecular groupings, then the longest lines at one temperature will not be the longest at another, the whole fabric of impurity elimination," based upon the assumed single molecular grouping, fails to pieces, and the origin of the basic lines is at once evident.
This may be rendered clearer by some general considerations of another order.
General Considerations. Let us assume a series of furnaces A A is the hottest.
D, of which
Let us further assume that in A there exists a substance a by itself competent to form a compound body ẞ by union with itself or with something else when the temperature is lowered.
Then we may imagine a furnace B in which this compound body exists alone. The spectrum of the compound B would be the only one visible in B, as the spectrum of the assumed elementary body a would be the only one visible in A.
A lower temperature furnace C will provide us with a more compound substance y, and the same considerations I will hold good.
Now if into the furnace A we throw some of this doubly compounded body y we shall get at first an integration of the three spectra to which I have drawn attention; the lines of y will first be thickest, then those of B, and finally a would exist alone, and the spectrum would be reduced to one of the utmost simplicity.
This is not the only conclusion to be drawn from these considerations. Although we have by hypothesis B, y, and all higher, that is, more compound forms of a, and although the strong lines in the diagram may represent the true spectra of these substances in the furnaces B, C, and D respectively, yet, in consequence of incomplete dissociation, the strong lines of B will be seen in furnace C, and the strong lines of y will be seen in furnace D, all as thin lines. Thus, although in C we have no line which is not represented in D, the intensities of the lines in C and D are entirely changed.
In short, the line of a strong in A is basic in B, C, and D, the lines of ẞ strong in B are basic in C and D, and
Application of these General Considerations to Impurity Elimination.
Now let us suppose that in the last diagram (FIG. 2) the four furnaces represent the spectra of say, iron, broken up into different finenesses by successive stages of heat. It is first of all abundantly clear that the relative thicknesses of the iron lines observed will vary according as the temperature resembles that of A, B, C, or D. The positions in the spectra will be the same, but the intensities will vary; this is the point. The longest lines, represented in the diagram by the thickest ones, will vary as we pass from one temperature to another. It is on this ground that I have before stated that the whole fabric of impurity elimination must fall to pieces on such an hypothesis. Let us suppose, for instance, that manganese is a compound of the form of iron represented in furnace B, with something else; and suppose again that the photograph of iron which I compare with manganese represents the spectrum of the vapour at the temperature of the furnace D. To eliminate the impurity of iron in manganese, as I have eliminated it, we begin the search by looking for the longest and strongest lines shown in the photograph of iron, in the photograph of manganese taken under the same conditions. I do not find these lines. I say, therefore, that there is no impurity of iron in manganese, but although the longest iron lines are not there, some of the fainter basic ones are. This I hold to be the explanation of the apparent confusion in which we are landed on the supposition that the elements are elementary.
Application of these Considerations to Known Compounds.
Now to apply this reasoning to the dissociation of a known compound body into its elements
A compound body, such as a salt of calcium, has as definite a spectrum as a simple one; but while the spectrum of the metal itself consists of lines, the number and thickness of some of which increase with increased quantity, the spectrum of the compound consists in the main of channelled spaces and bands, which increase in like manner.
In short, the molecules of a simple body and a compound one are affected in the same manner by quantity in so far as their spectra are concerned; in other words, both spectra have their long and short lines, the lines in the spectrum of the element being represented by bands or fluted lines in the spectrum of the compound; and in each case the greatest simplicity of the spectrum depends upon the smallest quantity, and the greatest complexity (a continuous spectrum) upon the greatest.
The heat required to act upon such a compound as a salt of calcium so as to render its spectrum visible, dissociates the compound according to its volatility; the number of true metallic lines which thus appear is a measure of the quantity of the metal resulting from the dissociation, and as the metal lines increase in number, the compound bands thin out.
I have shown in previous papers how we have been led to the conclusion that binary compounds have spectra of their own, and how this idea has been established by considerations having for a basis the observations of the long and short lines.
It is absolutely similar observations and similar reasoning which I have to bring forward in discussing the compound nature of the chemical elements themselves.
In a paper communicated to the Royal Society in 1874,
referring, among other matters, to the reversal of some lines in the solar spectrum, I remarked *:
"It is obvious that greater attention will have to be given to the precise character as well as to the position of each of the Fraunhofer lines, in the thickness of which I have already observed several anomalies. I may refer more particularly at present to the two H lines 3933 and 2968 belonging to calcium, which are much thicker in all photographs of the solar spectrum [I might have added that they were by far the thickest lines in the solar spectrum] than the largest calcium line of this region (42263), this latter being invariably thicker than the H lines in all photographs of the calcium spectrum, and remaining, moreover, visible in the spectrum of substances containing calcium in such small quantities as not to show any traces of the H lines.
"How far this and similar variations between photographic records and the solar spectrum are due to causes incident to the photographic record itself, or to variations in the intensities of the various molecular vibrations under solar and terrestrial conditions, are questions which up to the present time I have been unable to discuss."
An Objection Discussed.
I was careful at the very commencement of this paper to point out that the conclusions I have advanced are based upon the analogies furnished by those bodies which, by common consent and beyond cavil and discussion, are compound bodies. Indeed, had I not been careful to urge this point the remark might have been made that the various changes in the spectra to which I shall draw attention are not the results of successive dissociations, but are effects due to putting the same mass into different kinds of vibration or of producing the vibration in different ways. Thus the many high notes, both true and false, which can be produced out of a bell with or without its fundamental one, might have been put forward as analogous with those spectral lines which are produced at different degrees of temperature with or without the line, due to each substance when vibrating visibly with the lowest temperature. To this argument, however, if it were brought forward, the reply would be that it proves too much. If it demonstrates that the h hydrogen line in the sun is produced by the same molecular grouping of hydrogen as that which gives us two green lines only when the weakest possible spark is taken in hydrogen inclosed in a large glass globe, it also proves that calcium is identical with its salts. For we can get the spectrum of any of the salts alone without its common base, calcium, as we can get the green lines of hydrogen with out the red one.
I submit, therefore, that the argument founded on the overnotes of a sounding body, such as a bell, cannot be urged by any one who believes in the existence of any compound bodies at all, because there is no spectroscopic break between acknowledged compounds and the supposed elementary bodies. The spectroscopic differences between calcium itself at different temperatures is, as I shall show, as great as when we pass from known comFounds of calcium to calcium itself. There is a perfect continuity of phenomena from one end of the scale of temperature to the other.
Inquiry into the Probable Arrangement of the Basic
As the results obtained from the above considerations seemed to be so far satisfactory, inasmuch as they at once furnished an explanation of the basic lines actually observed, the inquiry seemed worthy of being carried to a further stage.
The next point I considered was to obtain a clear mental view of the manner in which, on the principle of evolution, various bases might now be formed, and then become basic themselves.
• Phil. Trans., vol. clxiv., part 2, p. 807.
It did not seem unnatural that the bases should increase their complexity by a process of continual multiplication, the factor being 1, 2, or even 3, if conditions were available under which the temperature of their environment should decrease, as we imagined it to do from the furnace A down to furnace D. This would bring about a condition of molecular complexity in which the proportion of the molecular weight of a substance so produced in a combination with another substance would go on continually increasing.
Another method of increasing molecular complexity would be represented by the addition of molecules of different origins. Representing the first method by A+A, we could represent the second by A+B. A variation of the last process would consist in a still further complexity being brought about by the addition of another molecule of B, so that instead of (A+B), merely, we should have A+ B2.
Of these three processes the first one seemed that which it was possible to attack under the best conditions, because the consideration of impurities was eliminated; the prior work has left no doubt upon the mind about such and such lines being due to calcium, others to iron, and so forth. That is to say, they are visible in the spectra of these substances as a rule. The inquiry took this form Granting that these lines are special to such and such a substance, does each become basic in turn as the temperature is changed?
I therefore began the search by reviewing the evidence concerning calcium and seeing if hydrogen, iron, and lithium behaved in the same way.
(To be continued)
ANALYSIS OF BOILER FEED-WATERS.
By W. F. K. STOCK. F.C.S., F.I.C.
BEING frequently engaged in the analysis of boiler feedwaters, I have found, as a result of several years' experience, that unless the person to whom a report is submitted happens to be possessed of considerable chemical knowledge, a statement giving an exhaustive analysis of a water residue is apt to be very much more puzzling than edifying, and, as a matter of fact, such an analysis is by no means necessary to the purpose of selecting waters for boiler use. A much more simple method of procedure has stood one in good stead in several difficult cases, and is the one I always follow, of course with modifications to meet special requirements.
Most of the readers of the CHEMICAL NEWS will be familiar with the characteristics of a good boiler water, but for the sake of making more complete the description of the mode of working, I may be allowed to point them out as follow:
1. Freedom from any very appreciable quantity of suspended mineral matter.
2. Absence of any trace of mineral acids or of acid salts, or corrosive salts of any kind.
3. Absence of oily or fatty substances. 4. A good boiler water should not contain more than 30 grains solids per gallon, and not more than half of this should precipitate on boiling under pressure. Some little consideration is here due to the statements thus made. For example, the amount of suspended mineral matter a boiler water may contain is, to a great extent, governed by the quantities of carbonates of lime and magnesia, and sulphate of lime it contains, and by the manner in which the boiler is fed. If a water gave a coherent deposit on boiling, I should feel bound to object to more than 2 or 3 grains of mineral matters per gallon in suspension, as tending to augment and harden such deposit; and, again, if a boiler were to be fed without subsidence or filmation, the same objection would hold
Analysis of Boiler Feed-Waters.
good on account of damage to pumping and feed appa ratus. With respect to mineral acids or corrosive salts my opinion is that any such contamination ought to condemn a water utterly for boiler purposes, unless simple and effective means could be adopted for their neutralisation.
The action of oils and fats has of late received considerable attention in connection with boiler waters. For some time the opinions respecting their influence were extremely various, but it is now pretty generally acknowledged that their presence is of no possible good, and may lead to very serious harm. The following case, which came under my own observation in March, 1876, may be of interest in this connection. A boiler at a large ironworks in [the Cleveland district was being fed with Tees water (a most excellent boiler water), which was slightly heated on its way to the boiler, by the exhaust steam from the blowing engines, with which steam, however, it never came into actual contact. It was observed that after the boiler had been at work for about two years, the feed pipe supplying it with the warmed Tees water became leaky in places not far removed from a flanged joint, the perforations from which the water oozed being like very small pin-holes. The boiler was neighbour to another, having a cast-iron feed pfpe, in which no leak whatever existed. The faulty pipe was removed, and put into my hands for examination. I first of all paid attention to the feed water, and, finding no clue there, turned my attentions upon the pipe itself. I had some difficulty in detecting the exterior preparations, but where they occurred the interior of the pipe was eaten away to such an extent that a walnut would have laid in the holes. These holes were filled with spongy masses of what appeared to be ferric oxide, but which upon analysis gave the following results:
The organic matter yielded oleic acid in quantity, on treatment with ether, and this, coupled with the presence of both ferric and ferrous oxides, and the comparative ease with which wrought-iron filings are attacked by oleic acid in presence of water, when heated under pressure, led me to adopt the following explanation of the corrosion. The presence of the fatty matter must, under the circumstances, be attributed to accident; most probably this had occurred during erection of plant. The first effect of the action of the fatty acid upon the metal was the production of a ferrous salt, which was oxidised by the oxygen existing in solution in the water, the iron only being raised in the scale of oxidation, the fat acid being liberated, and seizing upon another portion of metal, which was again oxidised, and so the action became local and continuous. I do not believe the cast metal pipe would have suffered at all under such circumstances, because the graphite it contained would have protected it from corrosion, and under my advice cast pipes were supplied to all the boilers as a preventive measure. It is seldom, indeed, or never that all the features I have pointed out would occur in any individual sample of water, and as a rule the most the analyst has to do is to indicate what amount of scaleforming matter the sample contains; and when it is called to mind what terrible accidents have occurred, and are constantly happening, through the unadvised use of hard waters, it becomes a matter of the utmost importance to have some reliable and simple method of making this
January 3, 1879.
point clear to steam users. I have placed the limit of this figure in a water analysis for boiler purposes at 15 grains per gallon, which number is the result of observation partly, and of inquiry amongst practical men using waters which were known to me. Any greater contents leads to more frequent blowing off and chipping than is the rule, and loss of time is the consequence. The evil becomes much worse if attention is withheld, and the ultimate result is local overheating, unequal expansion and con traction, culminating either in sudden destruction of the boiler, with its too-often attendant horrors, or the fabric becomes utterly leaky and unmanageable. The following is the method I have devised and adopted as embracing the whole of the foregoing, and as furnishing in a very short time most reliable information as to the character of any given water generally :
1. The suspended matter is determined by filtering 700 cc. of the water through tared papers. The residue is washed, dried at 110°C., and weighed, then burnt and weighed again. The weight in centigrammes gives grains per gallon, and the difference between first and second weighings gives crganic suspended matter.
2. The examination for free mineral acids consists in testing the water, which must be rendered clear by filtration, if necessary, with dilute cochineal tincture, and determining the acid so found with decinormal soda. If corrosive salts are suspected they are best arrived at by the evaporation of a large volume of the water (700 to 1500 c.c.), and a trial of the action of the concentrated liquid upon a weighed strip of pure iron, which should be afterwards carefully washed with boiled distilled water, then with strong alcohol, dried, and weighed. The nature of the corrosive substance is, of course, given in the report, with any other information the analyst can supply regarding it.
3. Oily and fatty matters occasion a milky appearance in water containing them, which disappears on treatment with a moderate quantity of ether. Oil or fat is determined by evaporating 350 c.c. on the water-bath (with the addition of one or two drops The of dilute sulphuric acid) to about 70 c.c. residual acid liquid is cooled, digested with ether in a stoppered tube about two centimetres diameter. The ethereal portion is decanted into a weighed capsule, the acid liquid washed with more ether, which is added to that in the dish, and the mixed ethereal solutions evaporated over the water-bath and weighed; and this weight, reported along with the weight of caustic soda needed to render the fat, or oil, found harmless. It is only in condensed waters that such substances are found as a rule; if, however, grease should occur in water, giving also lime and magnesia salts, sufficient soda would be required for their removal also.
4. The proportions of solids deposited on boiling under pressure and solids retaining solubility on boiling under pressure, are found by taking an observation of the total solid matter the water contains, the evaporation of 70 c.c. in platinum, and drying at 100° C., is quite sufficiently accurate. It is then necessary to boil 700 c.c. of the water for three hours in a flask connected by an india-rubber stopper, with an inverted Liebig's condenser, well fed with cold water. The boiled water is cooled to temperature at which it was measured, and if the condenser has received proper attention, no appreciable diminution of volume will have taken place. The cooled water is run through a dry filter, and 70 c.c. are evaporated at 100° C. as before. The difference between the weights of the two residues gives solids deposited on simply boiling. We have now to add to this the calcium sulphate