Potassio 99 In Fig. 1. we have given drawings of some of the most characteristic spectra of fluorescence and absorption. In these drawings the refrangibility of the light is indicated on the scale with millimetre divisions introduced for this purpose by Bunsen. This scale was selected for the double reason, that it corresponds very nearly with the appearance of the spectrum as seen in the spectroscope employed, which is one largely in use and peculiarly well adapted to such observations as the present, and that it is largely used in all chemico-spectroscopic work, and would therefore be most familiar to those likely to take interest in this work, which has a decided chemical affiliation. The relative intensities of various parts of the bands, and of the bands of each spectrum among themselves, is indicated by the depths of the white spaces, the distinction between the bright bands of fluorescence, and dark bands of absorption, being marked by making the first white and the other shaded. No attempt is made to indicate the relative brightness of different spectra. This woodcut is to be regarded, however, rather as an illustration than as a map in which various positions are to be found with great precision. From the nature of the work, correction after proof is limited to very slight variations, and the full difficulty of accurate execution did not appear until the work was finished. The spectra, as here shown, will be found correct in the character and arrangement of the bands in each, but small errors in the location of the maxima of bands must be expected, and, in fact, for all points where precision is required, it will be necessary to refer to the exact numerical expressions. As will be seen further on, the behaviour of absorptionbands is a very useful assistance and guide to the study of certain changes in these salts, and we have therefore given some attention to these, although a variety of considerations indicate that no such connection exists between the band of absorption and fluorescence in these salts, as would be at first suggested by their general similarity of arrangement. A single glance at the woodcut will exhibit the existence of very characteristic differences between the spectra of certain salts, and it will be evident that, in a number of cases, one body can be readily discriminated from another by this means. Indeed, in the course of this investigation, the fact of admixture in many of the commercial uranium salts was recognised in this way, without opening the bottles in which the materials in question were packed, and, in other cases, the progress and consummation of a change in composition, or in the formation of a compound, was watched and recognised with the greatest ease and precision. In almost every case there is a tendency of the light to fade off ade off in the bands towards one side more gradually than towards the other. In nearly all spectra this graduation is greatest towards the less refrangible end of the spectrum. The character of any one band is, as a rule, a type of all the bands of a spectrum; but to this a remarkable exception is found in the double acetates of uranium generally, and especially in the sodium salt whose fluorescence is the brightest. In the spectrum of this salt the first four bands at the lower end of the spectrum in the orange and red differ Potassio-uranic sulphate bi- entirely in character and spacing from the rest, except the bogatifth, which seems to be in a transition state. This will be seen at once by a glance at spectrum 3 of the woodcut. Do. (anhydrous). the sulphate and normal double sulphates, but in the case of the acetate and double acetates, fluoride and double fluorides, chloride and double chlorides, as also among the numerous hydrates of the sulphates, it fails to main It is also true, as a rule, that double salts with the same acid have bands of a like character; but to this also there are decided exceptions, and it is by no means true that all salts with the same acid-as, for example, acetates and double acetates, as stated by Becquereltain itself. have like bands. This chances to be true in the case of A glance at spectra 4 and 5 on Fig. 1 will show that FIG. 1.795 Buoy yw ei oi asonaladura biloa avisado o -iz eledelua bias-oilledenoiengmib atlaines adt 30 Istavi リ liam 5 ybus 2 1. Uranic nitrate. 2. Uranic acetate. 3. Sodio-uranic acetate. 4. Uranic oxychloride (acid), mixed hydrates. 5. Potassio-uranic oxychloride. 6. Uranic oxyfluoride. 7. Bario-uranic oxyfluoride. 8. Uranic phosphate, mixed hydrates. 9. Calcio-uranic phosphate.sd1o. Ammonio-uranic sulphate. nothing could well be more unlike than the spectra of uranic oxychloride and the potassium chloride. The question naturally arises, how far the spectra of substances are constant, and in what way a change in spectrum if observed is to be interpreted. To this we would reply that we have so far found that no substance has its spectrum changed by anything which does not affect its composition, excluding the effect of heat, which in all cases temporarily modifies fluorescent action, and the destruction of crystalline structure by fusion, which in some cases has a like effect permanently. We must also exclude certain cases in which, by peculiar treatment, a substance has been caused to give a continuous spectrum, in place of what may be considered its normal one. We may, therefore, confidently assert in many cases whether (under certain treatment) a body has or has not suffered a change in composition, and, indeed, trace such a change step by step. This part of the subject can be best elucidated by a narration of our experience in the first case in which this principle was applied. Stokes had noticed certain effects in nitrate of uranium which had been fused and partly dehydrated, and after an FIG. 2. NEWS refrangible extremities of the scale. The following table will give some notion of these spectra : Fluorescent Spectra of Ammonio-Uranic Sulphates. Normal salt (hydrated) Dried salt (anhydrous) Heated salt.. I. II. III. IV. V. VI. VII. VIII. 360 416 49'2 581 680 770 860 95'0 334 400 480 56'3 657 75'2 860 92.8 36'0 424 512 60'3 700 79.8 89°2 96.8 As also Figure 2, in which I is the normal salt, 2 the mixture of this and the anhydrate obtained by partial drying, 3 the pure anhydrate, 4 the mixture of this and the new salt obtained by partial ignition, and 5 the pure ammonio-di-uranic sulphate. The white fumes expelled in the process of heating were ammonium sulphate, and the resulting compound yielding the new spectrum, therefore, might have been formed in one of two ways; either all the ammonium sulphate had been driven out, or a portion only. It became necessary, therefore, to test the heated salt for ammonia, which was done by distilling a portion with hydrate of calcium, and receiving the distillate in Nessler's reagent. The abundant precipitate obtained established the presence of ammonia in such quantity as to render the delicacy of the test applied quite superfluous. The question then arose, Is this salt a definite compound of uranic sulphate with ammonium sulphate? Analysis alone could reply. The heated salt possessed a somewhat stronger greenish hue than the normal salt; it was completely soluble in water with the exception of a few dark coloured grains, probably consisting of U304 For analysis the salt was dissolved in water, and the sulphuric acid thrown down by barium chloride; after separating the excess of this reagent in the filtrate the uranic oxide was precipitated by ammonia, ignited and weighed as U3O4 in the usual manner : 06444 grm. gave o'5284 grm. BaOSO3=28'15 per cent SO3, and 0'4194 grm. U304-66 30 per cent U203. The formula, 2(U2O3SO3)+NH2OSO3, requires the following percentages: attempt to reproduce his results, the ammonio-uranic sulphate was in turn treated in a like manner. A little of the crystallised salt containing 2 atoms of water was placed in a short test-tube, and heated until part of its water had been expelled. On examination (after cooling, for while hot little fluorescence was manifested) its spectrum was found to be of a duplicate character, consisting of the bands belonging to the normal salt, and another set, each line of which was a little displaced downwards in the spectrum. On heating again and expelling more water, the intensity of the new spectrum was increased, and that of the old one diminished; and this continued until-when water ceased to come off-the new spectrum alone occupied the field. It was, therefore, concluded that this was the spectrum of the anhydrous salt. On now pushing the heat further white fumes were expelled from the salt, and on examination-in addition to the spectrum just described-yet another new one was perceived, having its bands displaced upwards in a very marked manner. Further heating drove off more white fumes and strengthened this new spectrum, while it diminished the one proper to the anhydrous salt, until at last fumes were no longer expelled even at a temperature of about 650° F., and the last spectrum in turn occupied the field alone. It was then seen to be like the spectrum of the normal salt in character, but with its bands displaced upwards in a degree increasing from the less to the more From this it is evident that one-half the am monium sulphate in the normal salt is driven out by heating, leaving an anhydrous ammonio-di-uranic sulphate. In his recent memoir Becquerel describes, under the name of a sub-ammonio sulphate of uranium, a salt obtained in the preparation of nitrate of uranium from impure materials, and states that it is the only uranium compound whose fluorescent light yields a continuous spectrum. The composition given by him (Ur2O3 4 parts, SO, 2 parts, ammonia 1 part), unless regarded as a mere rude approximation, would agree better with a mixture of several salts than with any probable formula of an ammonio-uranic sulphate. This may, however, be a case of what may be called the abnormal continuous spectrum already alluded to. We have found uranium compounds yielding continuous spectra, but the true sub-ammonio sulphate-or, rather, ammonio-di-uranic sulphate-does not appear to belong to that class. (To be continued.) to stage sd sdt sdila Tom ad llew bluos gaidion Estimation of Magnesium as Pyrophosphate, og de ban boldogu CHEMICAL NEWS microcosmic salt as a precipitant, and to precipitate from 31 07064 ❞ 0.3181 400808ol,, 0*3666us ,,W 9802 (15yea The formula SO4Mg+70H2 requires 9.76 per cent.s The mean of the four analyses is o'04 per cent too high. In a second series the same process was employed, but ammonic chloride was added to the magnesic solution before precipitation. In this manner:2009 In view of the great consumption of commerciale fertilisers in the Southern Country, it may be deemed proper to devote a few pages of this journal to the consideration o of certain questions involved in the valuation and use of d article leaves much undone, to the consideration of which superphosphates. Although the writer feels that this points he intends returning on the completion of other experiments, still he is led to publish the results of some investigations, carried on in his laboratory, in answer The mean of the four analyses gives 9'78 per cent, or to the wishes of certain friends of agriculture and agricul 0'02 per cent too high, tural chemistry. The basis of the superphosphates employed in this region is, pre-eminently, the South Carolina phosphatic rock, an impure phosphate of lime. It consists of about 55 per cent phosphate of lime, 5 to 10 per cent carbonates of lime and the protoxide of iron, a few per cent oxides of iron, and traces of magnesia and alumina, partially combined with phosphoric acid; the remainder being unimportant for our present study. The phosphate of lime is, in all probability, entirely of the character of the socalled bone phosphate, or basic phosphate of lime, i.e., the chemical compound of 1 atom of phosphoric acid and 3 of lime. This form of phosphoric acid, the one important for vegetable and animal life, requires 3 atoms of base, whether they be metallic oxides (as lime) or simply atoms of water. The basic phosphate of lime is, practically considered, insoluble in water (especially in its mineral state), as is also the neutral phosphate of lime, a compound of 1 atom of phosphoric acid, 2 of lime, and I of water. On the other hand, the acid phosphate of lime, a compound of 1 atom of phosphoric acid, 1 of lime, and 2 of water, is highly soluble in water. The "free" phosphoric acid, also quite soluble, is an atom of this acid with 3 atoms of water joined chemically to it. Dr. Piccard has shown (in the Swiss Polytechnical Journal)-(1). That a complete solution of 1 equivalent of basic phosphate of lime is produced by the addition of not less than 2 equivalents of hydrated sulphuric acid, (i.e., 2 equivalents of hydrated sulphuric acid act on i equivalent of basic phosphate of lime to produce 2 equivalents of gypsum and 1 of acid phosphate of lime, substances readily soluble in water) back" (or the conversion of phosphoric acid from soluble into insoluble forms) takes place, independent of the amount of water which they contain, in such superphosphates which contain a large amount of basic phosphate of lime, in consequence of the employment of an insufficient quantity of sulphuric acid. (4). An increase in the amount of the soluble phosphoric acid can only take place where, in consequence of the use of large quantities of sulphuric acid, the insoluble phosphate of lime contains more phosphoric acid than is present in the neutral phosphate. The preceding observations have reference, it is true, more especially to the continental high-grade superphosphates, which, when freshly manufactured, contain from 10 to 25 per cent of soluble phosphoric acid, equivalent to from 20 to 50 per cent of bone phosphate dissolved, but they apply also to the articles prepared and sold in America. These latter, being manufactured from articles containing basic phosphate of lime, carbonate of lime and iron, oxides of iron, magnesia, and alumina (partially joined to phosphoric acid), present for our study causes of a reduction of the soluble phosphoric acid other than the large amount of originally unacted-upon basic phosphate of lime, always present in superphosphates prepared from South Carolina rock by the application of a comparatively small quantity of sulphuric acid. In this case, whatever carbonate may have remained undecomposed will most likely suffer decomposition from the action of acid phosphate of lime, the results being the liberation of carbonic acid and the substitution of the metallic oxide (previously combined with carbonic acid) for atoms of water in the acid phosphate; thereby Whatever free reducing it to the insoluble condition. alumina or peroxide of iron may be present in the superphosphate acts in a similar manner. Where sulphate of (2). By the action of more than I and less than 2 equiva-phuric acid, there is no reason to fear a direct exchange iron or alumina have been formed by the action of sullents of hydrated sulphuric acid upon I of basic phosphate of elements between them and the acid phosphate of lime. of lime, either of the following cases may occur:(a). Where only 1 equivalent of sulphuric acid is taken, and At another time I hope to speak of the modifications of these reactions produced by the liberal use of alkaline subsequent changes in the mixture are arrested by an chlorides. early separation of the soluble and insoluble portions; in this case one-half of the basic phosphate of lime is converted into acid phosphate of lime and gypsum. (b) Where the mixture is allowed to stand for a long time, and opportunity is thus afforded for the completion of chemical reaction, the acid phosphate of lime (formed from one-half of the basic phosphate by the action of the acid) reacts upon the remaining undecomposed basic phosphate, producing the intermediate neutral phosphate of lime, CaO,2HO,PO5+3CaO,PO5=2(2CaO,HO,PO,). In his studies concerning superphosphates, R. Jones, assistant at the Kuschen Experimental Station, comes to the following conclusions as the result of a long series of interesting and careful experiments : 3CaO,PO5+2(HO,SO3)=CaO,2HO,PO5+2(CaO.SO3). The excess of water ordinarily present furnishes the requisite quantity of water to produce 2 equivalents of hydrated sulphate of lime, CaO, SO3+2HO. (1). The superphosphates are not unchangable mix tures of gypsum, acid phosphate, and undecomposed basic phosphate of lime; but they contain the soluble phosphoric acid in the form of free phosphoric acid and acid phosphate of lime, the insoluble phosphoric acid as basic and neutral phosphate, and, in rare cases, in combinations which stand between the neutral and acid salts. Sulphuric acid is contained in them in the form of gypsum, and only exceptionally do any considerable quantities of free sulphuric acid appear to occur in them. (2). These different chemical combinations are undergoing a constant interchange of elements; which decompositions produce, according to the external conditions and the quantity of sulphuric acid employed, an increase or a decrease in the amount of soluble phosphoric acid. (3). A decrease takes places in every superphosphate, independent of the amount of sulphuric acid employed, where it loses in water, either by the action of artificial heat, or from long exposure to dry air. Again, "going * Annalen der Landwirthschaft, b. 56. Having thus endeavoured to introduce some of the causes for the decrease in soluble phosphoric acid of old superphosphates, I would here call attention to various methods which have been employed to determine the degree of reduction. It is well to state that the desideratum is a method by which the amount of the decomposed phosphate of lime in a superphosphate can be determined; the soluble phosphoric acid having been previously extracted by water. This decomposed phosphate, whether wholly or partly a lime salt, may be either the neutral or the precipitated basic phosphate. It is requisite that the solvent for the decomposed phosphate shall not attack to any considerable extent the undecomposed phosphatic basis of the superphosphate, otherwise the results are indeed questionable. The weaker vegetable acids have been recommended as fit solvents for the reduced phosphates, but they are liable to the above objections. Again, the ammoniacal salts of carbonic and certain vegetable acidst have been used for a like purpose. Without entering upon a detailed criticism of the results of the treatment of superphosphates and pulverised raw phosphates by other chemists, nor upon my own investigations in this direction, I would mention that the bicarbonate and succinate of ammonia do not dissolve the neutral and freshly precipitated phosphate in a sufficient degree to allow of their use. The oxalate of ammonia is an admirable solvent of these phosphates, but, unfortunately, it attacks the raw basic phosphate so as to vitiate the analytical results. The neutral citrate of ammonia, however, while it dissolves nearly entirely the neutral and * J. A. Chesshire, CHEMICAL NEWS, July, 1869. t Dr. J. König, Annalen der Landwirthschaft, bd. 58. |