87 per cent of the bread in London is adulterated. Very NEWS. few of those who have published anything on this subject give details respecting the process they adopt, but in most instances it seems to be somewhat to the following effect:The bread is first charred and burnt nearly to an ash; the latter is then boiled in diluted hydrochloric acid, with which a little nitric acid has been mixed; ammonia is then added, and the precipitate which it produces is boiled in potassa. After filtration, hydrochloric acid is to be added in excess, and then ammonia, when it is supposed that the Ir is unfortunate that proceedings under the Adulteration Act should have been taken in the matter of the so-called adulteration of flour and bread with alum. In the first place, it is highly probable that this so-called Adulteration is a meritorious Act, and that the inventor of it deserves a civic crown, as would be due to him who should increase the harvest every year. Alum is added to flour and bread in order that flour, which otherwise would not make good bread, may be enabled to do so. By treatment with a trace of alum, flour of doubtful soundness is endowed with soundness. For this purpose a proportion of alum is required which does not exceed 20 grains to a 4-lb. loaf. One of the most important functions of the public analyst is to withstand popular clamour and to oppose professional prejudice-prejudice which owes its origin to imperfect acquaintance with the matter in hand. And this case is an illustration in point. The 20 grains of alum have been sensationally dealt with; and the people, and professional persons who ought to know better, have attributed tanning of the stomach and ruin of the digestion to these 20 grains of alum in the 4 lb. loaf. Nothing is easier than to show the unreasonableness of such notions; and perhaps some of those persons who are suffering from them will be surprised to be told that the phosphate of potash in a 4-lb. loaf (and which existed in the flour of which the 4-lb. loaf is made) is far more than enough to transform the alumina contained in the 20 grains of alum into phosphate of alumina. It is useful to call to mind that of the 20 grains of alum about half is water, and that there are only about 2-2 grains of real alumina (Al2O3) in 20 grains of alum. Under these circumstances, we are almost tempted to rejoice in the difficulties which beset the public analyst in his attempts to detect traces of alum in bread. We are not surprised that the public analyst returns bread which has been purposely alumed as being devoid of alum, inasmuch as the detection of traces of alum in presence of the constituents of the ash of bread is one of the most difficult problems of chemical analysis. In connection with this subject the following remarks on the detection of alum in bread, published by the Editor of this journal some years ago, may not be inappropriate at the present time : "This problem is one of far more difficulty than is generally imagined, and it is doubtless to this fact that the discordant results obtained by different analysts are to be attributed one stating that out of sixty-four samples of bread purchased at various shops in poor neighbourhoods at the East of London, where, if anywhere, adulteration would be practised in the most barefaced manner, not a single one was found to contain alum; whilst another analyst, with equal positiveness, mentions the name of a baker who is, in his opinion, almost the only person in a large district at the West End of London who sells unadulterated bread, and proceeds to state that more than precipitate will consist of alumina. With a pure solution of alumina to start with, doubtless this process would give the alumina would be accompanied by phosphoric acid, as accurate results; but it must be remembered that in bread well as phosphate of lime and phosphate of magnesia, each of which would make its appearance in the last precipitate with ammonia, and would consequently pass for alumina. But, granting that this tendency of the phosphates of lime and magnesia to simulate the reactions of alumina had been provided against, it seems to have been almost entirely overlooked by popular writers on this subject that whenever alumina and phosphoric acid meet together in solution, they adhere with the greatest pertinacity, and should not have deemed these points worthy of mention will infallibly appear together in the last precipitation. I did I not know that many analysts are habitually employing similar processes to the above, and are even estimating quantitatively the amount of adulteration in bread by weighing this precipitate of the mixed phosphates of lime, magnesia, and alumina, and calculating it as pure alumina. "My attention was first drawn to this subject by the fact that a sample of bread which was known to be entirely free from adulteration had been pronounced by a somewhat experienced analyst as being largely adulterated with alum. My assistance was asked in order to disprove this injurious allegation, and, having accordingly submitted the subject to a somewhat lengthened examination, I am induced to lay the results before the readers of the CHEMICAL NEWS, in the hope that, when the attention of chemists is drawn to the subject, it may be investigated as fully as its commercial importance deserves. "The great difficulty in my hands has been to devise a process which should not confound other things with alumina. It was easy to frame various modes of operating by which a minute trace of alumina could be detected, but I was for a long time baffled by finding that they were equally delicate in their reactions, whether alumina were present or not. In fact, I do not hesitate to say that the accurate analysis of a mixture of those phosphates which are precipitated from an acid solution by ammonia is one of the most difficult problems in inorganic chemistry that the chemist is liable to meet with in technical analysis. I do not pretend to have yet solved the difficulty, but the process which I have at last adopted has at least the merit of not showing the presence of alumina when that body is absent. It has, on the other hand, the inconvenience of being rather tedious in its manipulation, and to some may seem to be needlessly complicated. No one can be sensible of this fact more than myself; but of the without separating the phosphoric acid, this was the only numerous methods which I have tried, both with and one which invariably gave me trustworthy results. "The bread, of which at least 500 grains should be taken, is first to be incinerated in a platinum or porcelain dish, until all volatile organic matter has been expelled and a black carbonaceous ash remains. The temperature must not be raised much beyond the point necessary to effect this. Powder the coal thus obtained and add about thirty drops of oil of vitriol, and heat until vapours begin to rise; when sufficiently cool, add water and boil for ten minutes. Filter and evaporate the filtrate until the fumes of sulphuric acid begin to be evolved, when ten grains of metallic tin and an excess of nitric acid must be added, together with water, drop by drop, until action between the acid and metal commences. When all the tin i oxidised, add water and filter. Evaporate the filtrate until fumes of sulphuric acid are again visible, when more water must be added, and the liquid again filtered if necessary. To the clear solution now add tartaric acid, then ammonia in excess and sulphide of ammonium. Evaporate the liquid, containing the precipitate suspended in it, in a dish, until all the smell of sulphide of ammonium has disappeared. Filter, evaporate to dryness, and ignite to get rid of the organic matter. Powder the black ash, boil it in moderately strong hydrochloric acid, filter, add a crystal of chlorate of potash, and boil for a minute. Now add chloride of ammonium and ammonia, and boil for five minutes. If, at the end of that time, any precipitate is observed it will be alumina. From the filtered solution, if oxalate of ammonia be added, the lime will be precipitated; and if to the filtrate from this, ammonia and phosphate of soda be added, the magnesia will come down." When solutions of equivalent weights of uranic sulphate and rubidium sulphate are brought together, and the proper degree of concentration has been reached, warty concretions of minute crystals form, possessing a hue of remarkable beauty and a brilliant fluorescence. So strong is this that the white porcelain dish in which the crystals form appears pink by contrast. Thallio-uranic sulphate forms in a precisely similar manner, but is of a golden yellow colour with a fine lustre, but very slight fluorescence. It is not readily soluble in water, but is very stable, being easily re-crystallised from hot solution. Analysis of these salts has not been completed in time for insertion in this preliminary notice. We will now pass to the optical study of these salts in their alphabetical order. Ammonio-Uranic Sulphate,U2O3SO3+NH OSO3+2HO. -The spectrum of this salt has been already described, but for completeness we will here reproduce it with some additional data. The bands of this substance are distinguished by great abruptness on their more refrangible side, rising as it were suddenly to a narrow brilliant line, and then fading off gradually on the lower side in a manner suggesting a rounded convex surface. Their positions are shown in 1 of Fig. 20. In the first experiments made with this salt it was heated to about 200° C. to drive off its water, but subsequent experience showed that the same result might be reached by a continued application of a temperature of 100° C. Two atoms of water in this salt would amount to 671 per cent; and it was found that a specimen Uranic sulphate has heretofore been known to form the bottle placed in a hot-water oven continued to lose weight following double salts : Double Sulphates. This for about twelve hours. At the end of this time its total PRELIMINARY INVESTIGATION OF THE FLUORESCENT AND ABSORPTIVE SPECTRA OF THE URANIUM SALTS.* By HENRY MORTON, Ph.D., U2O3SO3 + NH4OSO3+2HO. The last-named was obtained by Berzelius, but Ebel. The history of the ammonio-diuranic sulphate has been already given in a previous part of this paper, and we need only add here that we have as yet been unable to prepare it otherwise than by the decomposition of the Absorption Spectra of some SO3+7HO. (?) without further decomposition, yields a spectrum such as dark spaces on the lower side. The bands near 70 and 80 | relation; A being the normal salt, and B that which we of the cut are not correctly shown, the first being too low, can only name by a conjecture:and the second too high. They should show an even spacing, one having its upper edge at 70'5 and the other at 80. The absorption spectrum of this salt is shown at 2 of Fig. 19. Magnesio-Uranic Sulphate.-As we have already noticed, a mixture of uranic and magnetic sulphates will form two compounds, one of these, which seems easy to reproduce, having the formula U2O3SO3+ MgOSO3+4HO. The other we have only succeeded in obtaining once in small quantity. This and the fact that it was then mixed with magnesium sulphate, render an accurate analysis impossible, but a determination of the water and sulphuric acid seems to indicate that the body has the formula U2O3SO3+ MgOSO3+7HO. We would, however, only present this as a suggestion. The two salts yield fluorescent spectra, which are entirely distinct in the positions of their bands, although both are alike, and of what we have called the normal form in their general character. The following table will show this Fluorescent Spectra of Magnesio-Uranic Sulphates. Bands. B I. 2. 3. 4. 5. 6. 7. 8. 404 480 55'5 65'7 746 84.8 91.6 448 530 66 4 708 810 90'5 96'0 The measures here given are of the upper edges of bands' except the 8th, which is measured at its centre. The absorption spectrum of the normal salt, A, is given at 3 of Fig. 22, and is characterised by the absence of the lower bands found in other double sulphates. Potassio-Uranic Sulphate, U2O3SO3+KO,SO3+ +2HO. This salt readily crystallises out when a solution of the mixed sulphates in atomic proportions is allowed to evaporate in the air; it forms warty concretions of minute crystals of a yellow-green colour and very bright fluorescence. In this state it contains 2 atoms of water, and shows the spectrum represented in I of Fig. 24, which is of the normal character, with a sharp termination of each band on its upper edge, and the bands peculiarly broad and bright. This salt suffers no change by heating or drying at 100° C., but if dried at 150° C. it loses all its water, and its spectrum changes to that shown at 2 of Fig. 21, in which the bands are much rounded, and displaced a little upward in the spectrum. It would thus appear that this salt can exist, and display fluorescent action as a bihydrate and anhydrate, but we have obtained no evidence of its forming a monohydrate. The absorption spectrum of the hydrated salt will be seen at 1 of Fig. 19, being indistinguishable from that of the ammonio-salt. The spectrum of the anhydrate is more difficult to observe, but by using the substance in powder with a little oil between slips of glass we can make out bands whose centres are at 937, 1010, III7, and 1244 respectively, and which are therefore quite unlike those of the normal salt. Rubidio-Uranic Sulphate, U2O3SO3+ RbOSO3+ +2HO. The preparation of this salt we have already described, and we will therefore pass at once to its fluorescent spectrum. In this the bands are much blended or rounded, and are decidedly lower than the corresponding ones of the potassium salt. Their brightest parts are located as follows: Fluorescent Spectra of Rubidio-Uranic Sulphate. I. 2. 340 416 492 57'6 667 76.0 85.2 94.8 This substance loses 2 atoms of water if it is dried at 100° C., but its fluorescent spectrum is not changed as regards the position of its bands; the brightness of its fluorescence is, however, reduced. An exposure to a yet higher temperature (180° C.) causes a slight loss of weight (06 of 1 per cent), and yet further reduces its fluorescence without other effect. The absorption spectrum of the normal salt will be found at 4 of Fig. 19. Sodio-Uranic Sulphate, U2O3SO3+NaOSO3+5HO.This salt presented more difficulties at the outset than any other, and, as might be expected, has yielded some very curious results. Thus a certain specimen was observed to yield the peculiar spectrum shown at 2 of Fig. 22, while the rest of the crop of crystals in another bottle from which it had been taken showed nothing of the sort. A prolonged study of this body has evolved the following facts, and has shown that many more await further investigation :-This salt in its normal state, containing 5 atoms of combined water yields the spectrum shown at 1 of Fig. 19, which is | of the normal type. A portion of this water is, however, lost with great ease, occasioning the formation, under ordinary conditions, of mixtures of several hydrates. Some of these we have been unable to isolate and determine, but we have found that, by gradually drying at a temperature of 150° C., we obtain a monohydrate whose spectrum is that shown at 3 of Fig. 19. If the salt in a damp state is placed suddenly in the oven at 150° C., it will lose almost all its water, and give a spectrum sensibly continuous; in this condition it may be dried at 200° C. without suffering any change. When heated to 250° to 290° the salt loses all its water, and then acquires a spectrum such as is shown at 4 of Fig. 19, in which each band looks like a prismatic column. Under various conditions, which we have not yet been able to determine with certainty, intermediate amounts of water are lost, and mixtures of other hydrates are produced, in which, no doubt, salts with 2, 3, or 4 atoms of water are involved. These, once formed, will, like the corresponding hydrates of uranic sulphate, maintain themselves in the presence of desiccating treatment, which would deprive the normal salt of much more water. The absorption spectrum of the normal salt is shown at 5 of Fig. 19. It is, perhaps, unnecessary to state that the peculiar spectrum shown at 2 of Fig. 22 is believed to be produced by three or more overlapping spectra belonging to as many mingled hydrates. Thallio-Uranic Sulphate, U203SO3+TIO,SO3+3HO.This substance has a very faint fluorescence. Bands can be made out at 92'4 (?), 356, and 760; below the first of these three seems to be a faint continuous spectrum. This salt loses 3HO and all its fluorescence by drying at 100° C. Its absorption spectrum is shown at 6 of Fig. 19. NOTES OF WORK BY STUDENTS OF PRACTICAL CHEMISTRY IN THE LABORATORY OF THE UNIVERSITY OF VIRGINIA. (No. II.) Communicated by J. W. MALLET, Professor of General and Applied Chemistry in the University. (1). On the Best Mode of Converting Calcium Oxalate into Carbonate in the course of Analytical Work. By Mr. J. R. McD. IRBY, of New Orleans, Louisiana. CALCIUM precipitated as oxalate is sometimes weighed as such after drying at 100° C., is sometimes converted into carbonate by heating to a carefully regulated temperature just short of redness, sometimes converted into lime by heating to bright redness or beyond, and sometimes given the form of sulphate by treatment with sulphuric acid or ammonium sulphate. Of these four modes of procedure, although accurate results can be obtained by any one of them, the second is, on several grounds, to be preferred for general use. If the oxalate itself be weighed, an unburnt filter, previously tared when dried at 100° C., has to be weighed with it, and the errors which may be allowed to arise from aygroscopic moisture affecting this filter at either of its weighings, and the tube or watch-glasses used to contain it are more likely to influence the result to a serious extent than those from similar causes when but the ash of a filter and a small crucible are concerned. The conversion into caustic lime requires a very strong heat, generally obtained by means of a blast lamp, the blowing being kept up for some time. The last traces of carbon dioxide are driven off with difficulty, and the platinum crucible is liable to alter slightly in weight, while the risk of mechanical loss from the blast, and the great readiness with which moisture is taken up from the See paper by Aug. Souchay in Fresenius's Zeitschr. f. Anal. Chem. 10 jahrg., 3 heft, s. 323, and remarks upon same by Fresenius in same periodical, s. 326. atmosphere by the lime during cooling and weighing, are not to be altogether overlooked. The acid fumes given off during the conversion into sulphate and final evaporation are annoying, and the heating is tedious and requires very careful watching to prevent loss. Pure calcium carbonate is undoubtedly the most stable and desirable form in which to obtain the final product for weighing, and if at once obtained by carefully managed heating of the oxalate, as may be accomplished in welltrained hands, leaves nothing to be desired; but if the temperature be allowed to rise a little too high, and a little caustic lime be formed, the necessary evaporation with solution of ammonium carbonate is tedious and troublesome, and cannot be hastened without almost certain loss from spirting. Moreover, while a very small quantity of lime can thus easily be restored to the condition of carbonate, if any considerable amount of material have to be dealt with the moistening and evaporation will often need to be repeated more than once before the weight becomes constant. The object in heating is, therefore, to so regulate the temperature as to ensure the complete destruction of all oxalate, and to avoid altogether the decomposition of the carbonate. The statement of the writers on analytical chemistry, that the proper temperature is represented by very low redness, or should be just short of redness, is wanting in precision. Working at night or in the daytime, by bright sunlight or on a dark, cloudy afternoon, one's estimates of barely visible redness will represent by no means a small range of temperature, and it needs a good deal of personal supervision to teach a new laboratory student exactly how to proceed, so as to obtain at once, without the delays above referred to, a result so often called for as an accurate determination of calcium. Calcium oxalate (specially prepared and found to be quite pure, and fully dried at 100° C.) heated to the melting-point of lead for a short time, was found, on cooling, to have begun to decompose, but the extent of the change was quite small. At just the melting-point of zinc the weight could easily be reduced to within one or two per cent of the theoretical amount, but several hours' exposure to this temperature scarcely produced complete reduction to carbonate. Several metallic alloys were tried, in order to get from some one of them a barely-fused bath of the proper temperature, but they all gave too much trouble from surface oxidation and the tendency to separate into a more and a less fusible portion. Finally, it being ascertained that a heat but very little beyond the melting-point of pure zinc was required, the following arrangement was found practically successful. A solid cylinder of cast-iron, smoothly turned, 53 m.m. high and 66 m.m. in diameter, had a cylindrical hole of 40 m.m. deep and 40 m.m. diam., drilled into the upper end, thus producing a sort of crucible with walls and bottom 13 m.m. thick. A turned disc of cast-iron, 58 m.m. in diameter and 6.5 m.m. thick, with a little knob in the middle of the upper surface to serve as a handle, formed a cover; and in the upper surface of this cover, two hemispherical cavities, each 10 m.m. in diameter, were drilled at opposite sides, the centre of each 15 m.m. distant from the edge. Round the outside of the cylinder a little groove was turned, which enabled the whole to be supported over a lamp by a stout iron wire triangle. Fresenius, in his excellent "Anleitung zur Quant. Chem. Anal.' 5 aufl., s. 201, has given minute directions as to the details. The figure shows this thick walled crucible and cover in vertical section. The total weight was about 1050 grms. In the little cavities (a a) bits of metallic zinc of about a gramme each were placed, a piece of porcelain, such as a small crucible cover, was placed in the bottom of the cast-iron vessel, and upon this a platinum or porcelain crucible (the latter being found to answer best, on account of its inferior conducting power) containing the calcium oxalate to be heated. Gas from a Bunsen burner with tube of 9 m.m. diameter was used as the source of heat, and the position of the burner was so regulated that, when the stopcock was fully opened, the flame played over the bottom of the cast-iron block and about onefourth up the outside all round. With quantities of I to 15 grm. of oxalate, the full flame of the lamp was turned on at once, the mass of iron in the block ensuring sufficiently gradual heating, and it was then only necessary to notice when the bits of zinc in the cavities of the iron cover had fully melted; the decomposition was then complete. This took about thirty minutes, but during that time no attention on the part of the operator was needed. The calcium carbonate left in the crucible was quite free from caustic lime. The foliowing are two examples of the results: Calcium oxalate taken. Grm. 1.0388 1.5765 21 Calcium Calcium carbonate carbonate obtained. calculated. Grm. Grm. 0'7109 0'7115 I'0792 1'0798 It proved to be important that the decomposition of the greater portion of the oxalate should take place without the carbon monoxide gas given off taking fire, since the additional heat produced by its combustion through and on the mass sufficed to burn a little of the carbonate into lime, and the tendency to separation of carbon (rendering the mass dark in colour) was much greater when the gas took fire, while carbon once separated could not be well burnt off again without increasing the heat too much. The effect of too rapid heating, attended with the burning off of carbon monoxide, is shown by the following results, obtained in experiments in which the maximum temperature derived from the lamp was no higher than in others of entirely satisfactory character: Found. 38.18 38.19 38.32 38.33 Percentage of Lime obtained from Oxalate. Calculated. 38.36 gradually and to keep up the heat longer, about three quarters of an hour being required, while, for quantities of 3 grms., an hour was necessary. Hence, when the oxalate amounted to about 2 grms., it was found better to turn on the gas to the lamp somewhat In the course of actual analysis, the oxalate being upon a filter, as much as possible of the substance should be detached from the paper and treated as above described, while the filter itself is burnt upon the lid of the platinum or porcelain crucible, the minute residue left treated with one or two drops only of strong solution of ammonium carbonate, which small quantity can be dried up quite quickly and easily on a water-bath or gently heated sandbath, and the cover then introduced into the cast-iron cylinder along with the crucible; the two to be taken out, cooled, and weighed together. Lime (derived Lime calcu as calculated from carbonate. Per cent. from oxalate) lated directly which probably represents the composition of normal atacamite, while the larger proportions of water found in some of the recorded analyses may perhaps be due to alteration. from oxalate. 38.36 99'77 The figures in the last column are calculated from the formula Cupric oxide.. Copper Chlorine.. Water Quartz The water was determined directly by Mr. Cabell, and the facts carefully established that it had all been driven off and that no chlorine had been volatilised. Calculated. 55.85 14.87 16.63 12.65 (HO)3, I myself obtained some years ago, from a specimen of clean, sandy atacamite from Chili (Rammelsberg, "Handw. d. Ch. Th. d. Mineral.," 5 suppl., s. 57). 100'00 55'94 14'54 16.33 12.96 0'08 99.85 numbers agreeing well with the above results. (3). Analysis of Burnonite. By Mr. C. E. WAIT, of Little Rock, Arkansas. Choice fragments of beautifully crystallised bournonite, from Herodsfoot Mine, near Liskeard, in Cornwall, of sp. gr. 5.826, gave, on analysis |