ISSN:0003-2654    

DOI:10.1039/AN87702FP043

出版商:RSC    

年代:1877

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN87702BP045

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

THE A N A L Y S T . THE SOMERBET HOUSE COURT OF APPEAL? IT will be in the recollection of nearly all our readers, that when the Sale of Food and Drugs Act, 1874, was before the House of Commons, the Public Analysts of this country and many independent members of the House of Commons acting on behalf of their constituents, opposed very strongly the appointment of the Inland Revenue Chemists as referees in disputed cases under the Sale of Food and Drugs Act.This opposition was not made from personal grounds, but simply because the members and the analysts doubted the sufficiency of the experience which the Inland Revenue Chemists had had in such cases. From time to time since a few incidental matters have cropped up which have been sufficient to show that the doubt was not without foundation; but the mode of procedure which the chemists at Somerset House have adopted, has been SO extremely cautious and tentative that it is only occasionally that a case has come to light to which it has been necessary to draw public attention through the failure of justice which has been occasioned by their conduct.At the time when the question was before the House of Commons, the arguments on the point were very strong, and it was contended that tradesmen were suffering severely by the want of a competent ! Court of Appeal ; but the fact that the Inland Revenue Chemists only had to analyse five or six samples during the first year in which this duty was imposed upon them-and if our memory he right, they confirmed the analyses of the analysts in three cases of these five, and in one other case had opposed to them five chemists of wide reputation, and who all disagreed with their deductions- is sufficient, we think, to show that there was not much need for szcch a Court.The letters which are published in our correspondence column this month, throw some further light on the matter. Our readers will also remember the letter from Dr, Norgan, of Swansea, which we published in our last number, wherein he stated that these gomerset House Chemiats having found a certain sample of beer to contain 66.5 grains of common salt per gallon, added Strong Burton Beers contain about 60 grains of common salt per gallon, solely derived from the water, malt, and hops used.” This statement, however, although made above the three signatures of Messrs.Bell, Bannister, and Helm, is not only different from the results which the Chemists of the Inland Revenue Department at Somerset House themselves found only a few years since, but is, in fact, inaccurate. The circumstances under which the previous investigation took place were, that salt having been inserted in the schedule of the Licensing Act as one of the prohibited ingredients, and complaints having been made by some of the brewers in reference to this, the Somerset House Chemists were directed t o make an investigation into the amount of salt contained in ordinary ales, and the result of the investigation which they then made was that the rule was relaxed so far as to allow of the excessive amount of 50 grains of salt per gallon; and if our memory be right-we have not the figures before us now-the waximutn amount in all the samples (several hundred in number), which were examined for the purposes of this enquiry was not more than about 55 grains per gallon, and wc believe that this occurred in one ease only.128 THE AN AT,YST.It is hardly to be wondered at that the Burton brewers, resent such an outrageous statement.The Burton water certainly does not derive its excellence for brewing purposes from the amount of salt it contains, or it would be easy to imitate it; and it is scarcely possible for the Inland Revenue Chemists to make a more unjust or unfounded statement than to say that the strong Burton ales contain about 60 grains of common salt per gallon.The paper which we publish from Mr. Gatehouse, shews pretty conclusively what i B the maximum amount which can be derived from the malt and hops used. The amount present in the waters is capable of the most ready determination, and there can be no possible difficulty in allowing for the amount of concentration which takes place during the brewing process, and we affirm, unhesitatingly, that it is extremely rare to find a sample of genuine ale from any of the leading Burton breweries containing so much SB 60 grains of salt per gallon.In this case, therefore, the want of knowledge on the part of the Inland Revenue Chemists has led to a failure of justice. Not content with failing to make themselves acquainted not only with what had been done by other analysts, but also with the reports which had been issued from their own laboratory, the Inland Revenue Chemists, who were, up to 1873 or 1874 unfamiliar with the subject of milk analysis-while other chemists had worked on the matter for many years previously-have since then examined samples of milk, many of which have, apparently, been taken from under-fed or imperfectly -milked cows, and a large proportion of which have, in all probability, been some days in the course of transmission to Somerset House, and on the basis of these experiments they have evidently come to the absurd conclusion that milk always decomposes at a certain definite rate, and that if they analyse a sample a certain time after it has been examined by the original analyst, they must make allowances on the results which they obtain before they form their conclusions as to its purity or otherwise.More than this, instead of taking the milk of average cows or an average dairy as a standard, or instead of taking the milk even from the poorest healthy cow which they could meet with, and which was not half-milked-they actually go out of their way, not only to take as a etandard the milk of under-fed cows, but also to do, what the Sale of Food and Drugs Act certainly does not in any way authorise them to do, viz., receive and act upon exTarte statements of the g'poor proseczlted milkman," as t o the character of the food upon which the COWS have been kept.It is incredible that any Court of Justice could, for one moment, admit evidence founded upon irregular statements of this kind.By whom are the analyses at Somerset House executed? We cannot forget the fact that before a Committee of the House of Commons, not many years since, the heads of this very laboratory gave evidence " that neither by chemistry nor by any other means was the admixture of chicory with coffee to be detected." Even supposing that we admit that these men themselves do the work, are they honestly qualified to successfully contradict, by the examination of stale samples, the evidence of men who have been selected, by open competition, for the posts which they hold, and whose appointment has been in every case confirmed by the Local Government Board, and who have worked upon the fresh sample, while it was still in a state fit for analysis ? Still more : is it just that a certificate from Somerset House, should be taken fts a certificate representing the actual work of three men who in most cases are not cross- examined, in contradiction to the evidence o f Public Annlpts who w e cross-examined, We must go further.Still one more point we must raise.THE ANATJYST. 129 when the fact is notorious that only one, if any, of the three signatories t o the Somerset House certificate has been actually concerned in the analysis? Let the certificate of each man’s work bear its own proper signature only, and then there will be a fair basis on which to act, as his position and salary will be then known, and the magistrates will be better able to judge into whose hands the reputation of the original analyst has been placed.We do not say more now, because we know that as Boon as Parliament meets, the matter is t o be brought before the House of Commons, and we think this will be the most satisfactory mode of ventilating the whole subject; and, as amendments are certain to be made in the Bct next session, it will probably be a convenient time for amending this point also, and relieving the Inland Itevenue authorities from this source of anxiety.If prosecuting solicitors mould only insist on the personal attendance of these gentlemen in the witness box, and give them full scope t o air their little wisdom, the world would be the wiser, and the Somerset House Chemists more laughed at. THE CHEMICAL SOCIETY’S JOURNAL. SOME months ago a general meeting of the Fellows of the Chemical Society was held at Bur- lington House.At this meeting, among other things, the condition of the Society’s Journal was discussed, and various improvements were suggested and promised. So far, however, we are sorry to say, no beneficial results seem to have been produced. The Journal appears as late as ever, and the character of the abstracts becomes less arid less satisfactory.Take the September number, for example. In this (page 271) we have an abstract of rather more than half a page, in which we are informed that, as it was difficult to form an abstract we had better consult the original. Why then attempt abstraction at all? On the same page an abstract of rather more than a page in length begins, written by some one, (whose initials, by-the-bye, we do not find among the recognised abstractors given on the cover,) which few, we believe, will understand fully unless they have read the original ; the attempted explanation of the fact that bubbles are sometimes attracted, sometimes repelled by heat being particularly unsatisfactory.On page 275 space is wasted on a perfectly childish experiment, called 4 d Abortive experiment on Torpedoes,” and the three abstracts, Apparatus for Oxidation,’’ (‘ Laboratory Gasometer,” and “ A cheap Gas Blow-pipe,” would have been more advantageously placed in the waste paper basket of the editor.The next sixty pages are chiefly devoted to abstracts on organic chemistry, which we pass over with the remark that a very undue proportion of space is devoted to abstracts of papers, the authors of which claim an intimate acquaintance mit.h the exact position of every atom in even the most complicated compound.This may be very interesting to chemista who, like the authors of these papers, fancy them- selves hail-fellows-well-met with every atom under the sun, but it is somewhat tedious to ordinary chemists not on the visiting list of either atom8 or molecules.Passing on to other portions we come, on page 373, to what is probably the gem of the collection, entitled ‘‘ Differences observed in unadulterated milk (we suppose unadulterated milk from healthy cows is meant) in which the specific gravity of cows’ milk is said to vary between 1018 and 1045 ! ! ! This is really too much for our feelings, we must stop, and can only exclaim, whisper it not at Somerset House, or the increase in our dairies of the130 THE ANSLYST.well-known breed of cows favoured with iron tails. will be something truly alarming. I n order to improve this lamentable condition of things, and to render the journal worthy of the Chemical Society of London, and an expenditure on it of over $1,500 a year, me renture to offer the following suggestions. Instead of hampering our able Xditor with two dozen abstractors, occasioning the loss of much time and the frittering away of money, let there be but two, or at most three. These should be required to devote the greater part, if not the whole, of their time to the work of abstraction. A room in Burlington House should be set apart for their labour, and as an additional inducement to young but able chemists, the laboratory of the Society should be fitted up and placed at their disposal for certain kinds of work to be determii,ed, or approvod, by the Council. Under such an arrangement the Editor, and the Council of Publication, would have the whole work much better under control, which in consequence would be done with much greater regularity, and on the whole, much better than at present.

ISSN:0003-2654    

DOI:10.1039/AN8770200127

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

130 THE ANSLYST. ON THE AUOUNT OF SALT IN BEER. By J. W, GATEHOUSE. ON July 30th, a sample of beer, brought me for analysis by our Local Inspector, w;is found to contain 68.5 grains of common salt pcr gallon. The case on being taken before the Bath Magistrate, mas by them, at the request of the defendant, referred t o the analjsts at Somerset House. On September 7th, at the adjourned inquiry, a report was read, signed by Messrs.Bell, Bannister & Helm, which, whilst giving the amount of salt present as 66.5 grains per gallon, and thus substantially corroborating my own analysis, yet appended as iz rider, that they considered the beer might not be adulterated as they had found certain samples of strong Burton beer to contain about 60 grains of salt per gallon, derived solely from the water, malt, and hops used in brewing.On the strength of this statement the magistrates dismissed the case. Feeling assured that the Somerset House Chemists had made some mistake in the latter part of their statement, I have investigated the possibility of discovering from the composition of the beer itself, the maximum amount of salt that could be derived from the malt and hops, so that supposing the amount of chlorine in the water used to be known, the maximum amount which could naturally exist in the beer might be calculated. In order toarrive at this conclusion, we must, in the first place, know the percentage of chlorine calculated as salt present in malt and hops; and secondlp, be able to calculate from the analysis of the beer, the amount of each used in brewing a given quantity of' the beverage.Oudeman's gives the amount of ash in barley at 3.1 per cent., and that of malt as 2-7 per cent. Fehling and Faist; find the ash of barley to vary between 3.04 and 2.1. Polson gives it as 2-8, and Way and Ogston from 1.79 to 2.3 per cent., the mean of nine analyses being 2.09. I n experiments made by myself, a sample of barley gave 2.44 per cent.of ash, of which 2.04 was soluble in acid and *4 insoluble. Xalt from the same barley gave 2.47 per cent. of ash, of which 1.91 was soluble, and *56 insoluble in acid. The malt dust from the same sample yielded 8.4 per cent. of ash, of which 5.43 was soluble and 2.57 insolublc i n acid. Another analysis of ;t Muspratt found for barley 3 per cent., and malt 2.52.TI€E ANALYST. 131 different sort of malt, and malt dust from the same sample gave respectively 2-44 and 5.69 per cent.of ash, so that it is plain that in the act of germination barley loses not only organic, but also a considerable amount of its inorganic constituents, and it will be seen that a goodly percentage of this inorganic matter is derived from the soluble chlorides contained originally in the seed.Way and Ogston state that the ash of barley contains from a trace of salt only an amount varying up to 2.47 per cent,, their analyses of nine samples being respectively : a trace, 0.41, 0 56, 0.61, 0.725, 1.44, 1.59, 2-01 and 2.47 per cent., giving a mean of 1.09 per cent., and as malt certainly contains a less percentage than this, the amount of salt possible in a beer derived from the malt alone could not be greater than the highest of these percentages, and would with grcat probability, be lower than the mean.An analysis made by myself of the malt and malt dust mentioned above, gave for the malt only an unweigha'nle trace of chlorine, but for the malt dust 0 04 per cent. of argentic chloride, which equals 0.0164 per cent.of salt. The barley, malt, and malt dust also mentioned before, gave respectively -008 15, *0053, and -0.256 per cent. of salt. I n each case 1,000 grains were burnt, and the chlorine caleu- lated in the whole amount. We are therefore warranted in corning to the conclusion that the ash of malt is not higher than 2-5 per cent., and also that the percentage of salt this ash contains theoretically, as calculated from the total amount of chlorine present, is certainly less than 1 per cent., giving a percentage of -025 of sale in malt, as a possible maximum, this being probably many times higher than the average amount.From the analysis of Way and Ogston, hops appear to contain from 5.95 to 8.07 per cent. of ash, and of this from 3.72 to 4.28 per cent.consists of salt. Taking the highest of these numbers, this would give us 0.345 per cent. of salt in hops. My owu analjsie of a sample gave an amount of chlorine corresponding to 0.062 per cent. of salt. As the amount of hops used in brewing is seldom, if ever, more than 20-lbs. per quarter of malt for bitter beer, and generally less than half this in strong beer, and as this weight of malt would brew at least two barrels of beer or 72 gallons, the salt derived from the hops, could not in bitter beer exceed 6.7 grains, and in strong beer 3.35 grains per gallon.I n order to find the original amount of malt used in brewing any sample of beer, we require to know two things : first;, the amount of alcohol; and secondly the amount of solid extract the beer contains, or the specific gravity of the boiled beer made up t o its original bulk; from which, neglecting the small quantity of acid, we can find the original gravity of the wort, and the total amount of malt extract before fermentation.From these data the weight of malt used in the brewing, is easily deduced, as by Ure's experiments, a quarter of malt weighing on the average 320-lbs., will yield about 210-lbs.of extract, or in brewer's language, a barrel of 84-lbs. gravity. That the calculations based on these facts may be more clear, we will now take an actual example of beer analysis, in order to compare the amount of salt it could contain, with that actually present. The beer was a sample of the strongest Burton I could procure, made by a well-known firm. Specific gravity .. . . . . . . . . . . 1025.8 per cent. Amount of alcohol"' . . . . . . . . . . . . 8.65 ?? Specific gravity of boiled beer . . . . . . . . . . . . . . . 1,039'6 Specific gravity of the alcohol 985.5, giving a c( spirit indication " of 14.5, vhich by the tables, gives an additional gravity of 67'6 Original gravity of wort . . . . . . . . . 1107.2132 THE ANALYST. From this ( ( original gravity,” we next proceed to find the quantity of malt extract it contained, which may be done either from Ure’s tables or by the following calculation.Subtract 1,000 from the original gravity, divide by 100, and multiply by 2.5, will give the total amount of malt extract per gallon in pounds weight. To show that the above rule agrees with the tables, a wort of specific gravity 1032 would, by the tables, contain 7-95 per cent.of extract, or ,795 pounds per gallon, whereas by calculation 1032-1000=32, and 0.32 x 2*5=*8. Proceeding with our calculation above, an original gravity of 1107.2 = 1.072 x 2.5 = 2.68 pounds of malt extract per gallon, and as 320 of malt = 210 of extract, the amount of malt used =- 2.65 x 320 But as the percentage of salt in malt is not greater than 0025 per cent, the amount I n this calculation we haw taken no note of the amount of salt derived from the hop, but as it was not a bitter beer, if we add 3.35 grains, as before calculated, we shall obtain a total of 10*5 grains due t o malt and hops alone.The published analyses of the water used in the brewery where this beer was made, gives about 14 grains of salt per gallon, so that from malt, hops, and water, we get a possible amount of 24.5 grains of salt per gallon.The amount actually obtained by an analysis of the same beer was 18.24 grains, or about As the whole of the numbers above used are constauts, except the 2.68 obtained from the beer under examination, me may materially shorten the process by the annexed rule.To find the possible amount of salt in a beer due to malt alone,-Deduct 1,000 from the original gravity of the wort, divide the result by 100, and multiply by 6.6, which gives the salt in grains per gallon. of salt in this = 2’68 X 320XYF! or expressed in grains 820 210 x 100 ‘02‘ X 7000 = 7.1 5 . 210 x 100 of the possible amount. To take a case :- A Beer just analysed by me was found to contain Alcohol 5.2 per cent.The specific gravity of the Alcohol being *9911 the spirit indication ,.. Malt Extract 7-38 ,, was 8.9 which by the tables gives an original gravity of 38-6 Gravity of Boiled Beer ... ... ... ... ... 1030.6 Original gravity of Wort ... ... ... 1069.2 Salt due to Malt alone ... ... ... = -692 X 6.6 = 4’567 Salt due to Water unknown Salt due to Hops ...... ... 3.35 Possible total due to Malt and Hops ... 7.917 Amount of salt actually found by analysis 8.55. This process will thus, if the amount of salt in the water be known, always give a theoretical amount largely in excess of any that will actually be found, and yet sufficiently near to enable one to judge of the actual amount of adulteration, as the general character of the water in his district will always be known to the analyst.A very slight consideration of the statement made by the Somerset House Chemists, that a certain Burton beer contained 60 grains of salt per gallon, due to the water, malt, and hops alone, will thus be seen t o be based on some mistake, except the beer were purposely brewed from a water largely charged with salt, and much more so than is usually the case, even with Burton waters.THE ANALYST. 133 Even if a beer were brewed, BO strong as to contain the extract from a quarter of malt in a barrel, the amount of salt per gallon could not possibly exceed- From Malt 3 ' 0 x l ~ ~ ~ 3 ) E ' 0 2 5 = 15.5 grains. Maximum due to hops ... 6.7 Maximum due to malt and hops 22.2 leaving nearly 40 grains per gallon for the water alone. This, however, is in every respect an extreme theoretical case, the amount of 18.24 grains as actually found in the strong Burton, examined by me, being much nearer what I believe will be actually found in practice. This case shews, a t least, how much Public Analysts lie at the mercy of statements made by Somerset House officials, without proof of their accuracy being offered.

ISSN:0003-2654    

DOI:10.1039/AN8770200130

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

THE ANALYST. 183 ON THE PRODUCTS OF COMBUSTION OF COAL GAS. By C. HEISCH, F.C.S. Now that the excitement of Parliamentary contest is (at least for the present) over, I think it may be well to lay calmly before your readers some, at least, of the reasons which have led me to the conclusion (shared, I am glad to find, by Silliman and other good authorities,) that the greater part, if not the whole, of the sulphur contained in coal gas, is converted during combustion into snlphiiric acid.As there can bc no question that sulphurous or sulphuric acid must be the result of tlic combustion, the investigation is really confined to establishing the presence of one or other, or both, of these compounds in the air of a gas-lighted room. My experiments were first directed to establishing the presence or absence of sulphurous acid.I n a small room, containing only 292 cubic feet of air, an ordinary batming burner, consuming 4 cubic feet per hour, was burned continuously for from 24 to 48 hours. The gas contained an average of 22 gr. of sulphur, per 100 C.F. The only ventilation was the want of absolute tightness in the door and window, and one or two chinks in a boarded parti* tion.Pieces of paper moistened with a solution of iodic acid and starch paste were suspended in various parts of the room, but no coloration was to be found, though in this small space from 20 to 40 grs. of sulphur were burned dJring the different experiments. This was repeated many times, and on one occasion only, two of the slips of paper were dis- colored : one of these was supended directly over the burner, the other over one of the chinks in the partition, before mentioned, so as to catch any outward draught there might be.An examination of the gas was conducted in the ordinary way, at the same time, and on this particular day the gas contained nearly three times as much aniulonia as usual, which led to the belief that the discoloration of the paper was due to some nitrous compound formed by the combustion of the ammonia, and not to Sulphurous acid.This idea was confirmed by the fact that when the gas was passed through acid before being burned no discolouration occurred. This experiment was many times repeated, always with the same negative result. Much stress has been laid by some on the fact that if the gas be burned in a Referees’ sulphur apparatus without ammonia, little sulphuric134 THE ANALYST. acid is condensed, and, impressed with the idea of the high boiling point of that acid, the conclusion has been arrived at that if present it must be condensed. By connecting the end of the eduction tube of the Referees’ apparatus with a good condenser, I found that much more sulphuric acid could be obtained, showing that it did pass out of the eduction tube, though there is no doubt a large amount of sulphurous acid is formed in the apparatus.Does the combustion, then, in this apparatus correspond with the ordinary combustion in a room where the products of combustion are at once mixed with an enormous excess of air? To test this several analyses were made of the air from the eduction tube, and it was found to contain only from 13 t o 14 per cent.of oxygen, and 4 per cent. of carbonic acid; indeed it extinguished the flame of a taper when brought in contact with it. Having thus shown the difference between experiments, conducted in this apparatus an6 the ordinary combustion of gas, I made the following experiment to see how soon the sulphurus acid from the eduction tube would oxidize if brought into the air.A common lamp chimney, 7 inches long and 2 inches wide, was suspended over the end of the eduction tube, so as to receive the ascending current of hot air. Paper moistened with iodic acid and starch was suspended in this, and though such paper was rapidly blued at the mouth of the eduction tube, half way up the chimney it remained uncoloured.I come now to the more positive proofs of the presence of sulphuric acid in the atmosphere of rooms in which gas is burned. I put on one side for the present all experiments with leather and metal goods, though in an economic point of view they are very important, and confine myself simply to the amount that can be condensed by merely lowering the temperature of the air, and its relation to the quantity of sulphur contained in the gas.I n the small room before mentioned gas was burned at 4 cubic feet per hour in a bat wing burner, after three hours a half-gallon flask full of powdered ice was taken into the room and left till the ice was all melted (about 3 hours). The flask was placed at 4-ft. 6-in. from the ground, or about breathing height.The outside of the flask was then washed with distilled water, and the washings precipitated with Ba C1. An averago of several experiments thus made with gas containing just over 20 grs. of sulphur per 100 cubic feet gave Hz SO, -3 grs. condensed. A similar set of experiments made with gas containing an average of 10 grs. per 180 cubic feet gave only H2 SO, 0056.Now as there can be no doubt that the mischief done by the acid formed must be, t o a great extent, in proportion t o the ease with which it is condensed, we have here a proof that the mischief increases much more rapidly than the actual increase of sulphur. These experiments are also interesting as showing that notwithstanding its very high boiling point, the condensing point of sulphuric acid, when mixed with air, is like all other vapours, altered very rapidly, according to the proportion of air with which it is mixed. This need not surprise us when we remember t h a t water which boils at 212O has been found in the state of vapour in the atmosphere at a temperature of-lOO* F, and there is good reason to believe exists at much lower temperatures. I am now engaged in a series of experiments to test those facts still more strongly and precisely, and these together with the experiments on the effect on metals and other bodies of the air of gas- lit rooms, I hope to lay before your readers on a future occasion,

ISSN:0003-2654    

DOI:10.1039/AN8770200133

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

THE ANALYST. 135 ON THE PRODUCTS OF COMBUSTION OF COAL GAS. By W. C. YOUNG, F.C.S. DOES the presence of sulphur in gas produce sulphuric acid in sufficient quantity by its combustion to be injurious to health or property ? This is a question which has exercised the minds of many for a long period, and was recently warmly debated before a committee of the House of Commons. Having dated to that committee my firm belief that the greater part, if not the whole, of the sulphur is converted into sulphuric acid, I propose to give in this paper, an account of the experiments upon the results of which I based my conviction. The surfaces of varnished wood work, and the moisture condensed upon the cold surfaces of windows exposed in a room where nothing but gas had been used for lighting or heating purposes, gave very strong acid reactions to litmus paper, which acid proved to be sulphuric, and although I found considerably more on the upper part of the room, still the evidence was strong from the lowest portions. This led me t o suspend various moistened surfaces in the room, so that by measuring the gas consumed during the time they were hanging, I could ascertain the amount of sulphuric acid deposited upon every square foot for each 100 cubic feet of gas burnt.Ist,-Two square feet of linen, moistened with water : 100 cubic feet of Gas burnt, gave -9 Ba SO4 = *377 H2 SO4 100 cubic feet of Gas = .189 grains HD 804 on 1 square foot. 2nd-One square foot of bibulous paper, moistened with water : 100 cubic feet of Gas burnt, gave 045 Ba so4 = *19 H2 SO4 100 cubic feet of Gas = -19 grains HZ SO4 on 1 square foot, In the foregoing experiments no attempt was made t o check the ventilation of the room, which was of the most perfect kind, there being an opening six inches square into the flue close to the ceiling, and another communicating with the outer air, close to the floor.The paper and linen dried in about two hours.3rd.--Nine inches square of bibulous paper, moistened with weak solution of bicarbonate of soda, suspended a few inches in front of ventilator, in upper part of room : 150 cubic feet of Gas burnt, gave *70 Ba 804 = *293 Hz SO4 100 cubic feet of Gas = .347 grain HO 804 on 1 square foot. 4th-Repetition of 3rd, using weak solution of potash instead of bicarbonate of soda, paper being 4B-inches square : 72 cubic feet of Gas burnt, gzlve 1 Ba SO4 = -42 H2 so4 100 cubic feet of Gas = 4.14 grains H2 SO4 per square foot.The two last experiments show clearly that a great part of the sulphuric acid produced was being removed by the very perfect means of ventilation in use, and the gas did not, at any time during the experiments, contain more than 12 grains of sulphur per 100 cubic feet. These results seem to me to show that whatever the sulphur was resolved into immediately after combustion, it was ultimately converted into sulphuric acid. Having noticed that dust collected in rooms where gas had been much used was strongly acid, I collected some from the top of a wardrobe cupboard, which had been standing in a bedroom undisturbed for six months.The dust was boiled in water,136 THE ANALYST. filtered, and the acidity of the liquid, ascertained in the usual way, I found to be equal to 1.005 grains, H2 SO,. The top of the cupboard was 3-ft. by 1-ft. in surface, so that each square foot would give 0335 grain, H2 SO,. This calczdated for the whole surface of the four walls (the room being 12-ft.by g-ft., and 9-ft. high), supposing the acid to be evenly distributed over them, the gas having been burnt for twelve hours a day on an average, at the rate of about one cubic feet per hour, making altogether about 2000 cubic feet, would indicate that two grains of sulphur per 100 cubic feet was deposited thereon as sulphuric acid. As the wood upon which the dust had collected, had no dosbt absorbed some of the acid into its pores, I: cut three square feet out of the top of the canopy of the bed furniture in the same room, and treated it Kith boiling water, filtered, and took the acidity of the solution.This amounted to 1.42 grains H, SO,, which, calculated as above, would indicate that three grains of the sulphur in each 100 cubic feet of gas consumed was deposited as sulphuric acid.Certainly a very large proportion, considering that the room had been in ordinary use during the whole six months, the window opened for a considerable time daily. I obtained from a tradesman two glazed show cards, which had been hanging in his shop for six months, in which no coal fire had been used. There had been five burners, burning about three cubic feet per hour each, in use for about three hours per day, so that in round numbers about 6,000 cubic feet feet had been burnt.The cards were well washed with hot water and the acidity of the solution taken. 1 card, 3-ft. by 1-ft. c 1.78 grains H2 SO4 2 ditto, l-ft. by 1-ft. = ,588 ,, 9 7 Calculated on the amount found upon the first card there would be ~ 0 1 grain H, SO, on one square foot from 100 cubic feet of gas.These cards had been suspended vertically, but the following experiment was made upon the top of a tin box, which had been laid upon a shelf, of course presenting a horizontal surface. The box had remained undisturbed for fifteen months; during that time four burners had been in use for lengths of time per day varying with the season of the year. I have made an average which indicates that about 16,000 cubic feet of gas had been consumed during the whole period.The acidity found was equal to 1.96 grains of sulphiiric acid upon the whole surface, which was one square foot. This, then, would show that 100 cubic feet of gas burnt had deposited 0012 grain H, SO, on one square foot of surface, or rather more than was found on the cards, The box was taken from another shop than the one from which I obtained the show cards, but the t3ame Company’s gas was used in each, and I should mention that upon examination I found that a perfectly new show card, similar t o those I had previously tested after they had been exposed, contained no acid of any sort.Both these shops were exceptionally well ventilated, and I am of opinion that the greater part of the acid was deposited with the moisture condensed by the cooling of the room, consequent upon turning out of the gas and closing the door at the end of the day.I obtained from an old-established library, where but little gas was burnt, 8 octaro volumes which had been upon an upper shelf for a space of about 3 years. The books were well-dusted and carefully sponged with water, but I could not by these means washTHE ANA1,PST.137 the whole of the acid off the face of the bindings, its I found after sponging six times that they were still strongly acid to test paper. The dust was added t o the washings, boiled, filtered, and in the filtrate was estimated the free and combined sulphuric acid. Result, Total Hn SO4 = 4-16 grains.Free do. = 1.37 ,, Some dust merely shaken off, eight other octavo volumes from the same shelf, gave Total €12 SO4 = 2.1 grains, Free do. =: -441 ,, so that the greater past of the acid is absorbed into the leather. This dust was very hygroscopic, and when washed and dried, appeared exactly like powdered charcoal, in fact, presenting all the appearances of organic matter, subjected to the action of sulphuric acid.I also examined dust from cellars where no gas or coal fires had been burnt, and found it quite neutral to test paper ; containing only a trace of combined H2 SO,. I conclude from these results, that the atmosphere of a room becomes charged with the vapour of sulphuric acid in proportion to the amount of gas burnt, and the means of ventilation in use; that this acid is condensed with the moisture upon the cooling of the room, and the weak acid so deposited is deprived of its water when the room is again heated, so becoming concentrated, the process being repented day after day, until the acid is in sufficient quantity to damage anything exposed to it, and even as instanced above to char it.I n favour of the theory that sulphuric acid per se is produced by burning gas containing sulphur, and not by the oxidation of sulphurous acid after admixture with the air, I may xLerition the following experiment, which, apart from the application, is curious in itself.The glass chimney of the ‘‘ Sugg’~ London Argand,” is, when in use, more quickly covered with a deposit on its interior surface than other argands.This fact has been noticed by many, and I have heard several theories as to its origin, the more general being that it is due to the mineral matter or ashes of the suspended particles contained in the air supplied t o the burner. I f this were so, the same would be observed in other argands. In order to ascertain the composition of this incrustation, I left a chimney on a burner consuming about one foot per hour for two months.I noticed that the deposit first appeared as an opaque coating extending up the chimney a distance of about one inch, the base being on a line with the upper edge of the cone. The deposit increased in thickness until it covered the same space with innumerable transparent globules, which, in time, decreased in number and increased in size. These globules were evidently in a molten condition, as on cooling they became opaque a d hard, whereas when hot they were transparent and soft. They proved to be highly deliquescent, very strongly acid, and on analysis gave results showing them to be stannic sulphate. The amount collected was nine grains; 1 need hardly say the tin was derived from the cone of the burner. Here, then, is sulphuric acid found, where it would be least looked for, condensed on a very hot surface, and close to the base of a flame, that is t o say, where combustion is admittedly not so complete as at any other part of the flamc,

ISSN:0003-2654    

DOI:10.1039/AN8770200135

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

138 THE ANALYST. ON THE PRODUCTS OF COMBUSTION OF COAL GAS. By G. W. WIGNER, F.C.S. FOR many years past this question has been thoroughly misunderstood. No doubt this may seem a very sweeping assertion, but when I find statements made by an eminent gas engineer, who is an ex-manager of gas works, that the question of the sulphur in gas is simply ridiculous, because sulphuric acid ‘‘ could not be formed and is not formed,” the matter becomes of some importance to meet and answer, and when further, this gentleman says in reference to the formation of sulphate of copper and sulphate of zinc caused by the burning of gas, ‘( it is ridiculous,” it is clear that there is reason to ventilate the subject. Now what are the actual facts? Gas, as originally produced from the retorts, contains at least two different and distinct forms of sulphur impurities. One of these is unquestionably sulphuretted hydrcgen, as is shown by its action on lead paper and other tests ; the other is either bisulphide of carbon or a closely allied substance.Oxide of iron entirely removes the former, i.e. sulphuretted hydrogen, but for the removal of the bisulphide of carbon the use of lime in some form or other is essential, and it is also essential that this lime should be used in a judicious and careful way.The contention of the gas companies throughout has been that the products produced by gas containing sulphur in the second of these forms, did contain sulphurous, but not sulphuric acid, while the contention of those who have thoroughly investigated the matter has always been that the product was sulphuric acid.I have recently carried out a series of experiments, and invefitigated the question, and will, as briefly as possible, describe them. I may state at once, that I do not at all doubt that just at the instant of ignition of the gas, and in the actual zone of the flame itself, a certain amount of sulphur has been burnt into the form of sulphurous acid only, so that if, for example, the products are drawn from a spot only half way up the chimney of an Argand burner, sulphurous acid will be found present, but this is hardly to be wondered at, when we consider that the combustion of the gas has reduced the oxygen present in the air by some five or lsix per cent., and replaced it by a corresponding quantity of carbonic acid. It is scarcely likely that oxidation could go on under such circumstances as these, but the moment these products of combustion leave the chimney of an Argand, or the globe of an ordinary batsming burner, oxidation again sets in, promoted largely, no doubt, by the amount of aqueous vapour present in the air, and the sulphur is oxidized into sulphuric acid, and becomes still more injurious in its effects.Having referred to the matter in this general way, I will now consider it in the special light of the experiments I hare carried on, to prove the correctness or otherwise of these deductions. The experiments were mostly tried in a room which was 10-ft. 6-in. high, and had nearly 2,000 cubic feet capacity. The room had been ventilated by means of an ordinary Arnott’s ventilator, having an area of 36 square inches, but instead of continuing the ventilation through this, a series of plate glass tubes about 16-ft.long and of the same area, viz., 36 square inches, were constructed, and the ventilation was allowed to take place through these tubes. This was effected by carrying the tubes round two sides of the room, so as to put the opening of the ventilator in a position nearly opposite to the old position of the Arnott’s rentilator, over the fire place,THE AXALYST.139 and in order to prevent any obstruction to the draft the ventilator was changed from a natural one into an artificial one, i.e., instead of taking place from the lower specific gravity of the heated air, it was artificially forced by means of a small jet of steam in the chlmney, and regulated to such an extent as to keep the room during the experiments at a temperature fairly accordant with the number of burners going. The fire place was stopped UP during the experiments.These tubes t o which I have referred, and which fornied, in fact, the ventilator of the room, were then used as follows :-The first tube, which was about 5-ft.long, was surrounded with ice so as t o cool the escaping air, and condense, as far as might be, any condensible vapour which existed in the products of combustion, and the cooling effect was sufficient to bring the air at the end of this first tube t o an average teniperature of about 80" E: the products of combustion thus having been drawn from a level, some three inches below the ceiling, at a temperature of nearly looQ 3'.The next tube, of about 4-ft. in length, mas used to contain various articles, such as pieces of colored silk and other dress materials, which were exposed t o the current of air in order to test the effect which was produced upon them, and this tube also contained a number of pieces of test papers of different kinds (which I shall refer to afterwards), in order to ascertain whether sulphuric or sulphurous acid was given off.The next-four tubes were each of short length, and were filled with glass Bubbles kept moistened with water, or with solutions of alkalies or baryta salts, so as to absorb any sulphuric or sulphurous acid which might have been given oft'; while the last tube of all contained an air meter, so fixed as to register the exact quantity of air which passed through the apparatus, or in other words the amount of ventilation of the room.There was practically no escape for the air from the room, except that which took place through this apparatus, and the only way in which the products of combustion could escape condensation was by their passing too rapidly through the tubes, and consequently still existing in a state of vapour instead of being absorbed.I carried on the experiments under extremely varied circumstances, sometimes using three ordinary fish-tail burners, which would be a good average amount of liglit for a room of such a size ; on one or two occasions using eight burners of various kinds, some Argand and some batswing ; on one or two other occasions using only one burner, and not consuming more than 4-ft.of gas per hour. I n every case the gas was tested during the whole time the experiment was going on, by the Referaes sulphur test, to ascertain the amount of sulphur which it contained, and the gas was supplied to the burners through an independent meter, so that the quantity of gas burned was accurately known.The amount of gas consumed during each experiment varied from 34-ft. to 350-ft. The gas tested was of varying quality; sometimes the sulphur in it was as low as nine grns, per 100 cubic feet, while, in one case, it ran up t o 185 gmu. per 100 cubic feet. The burners which I used were, as I have said, of all kinds, Argand, batswing, and fish-tail.The experiments therefore resolve themselves into this :--That a room was ventilated, artificaliy it is true, but in the ordinary way, viz., at the ceiling, and at the ordinary speed-and that the air escaping from the ventilator was cooled and tested. First as to the sulphurous acid; during the whole of the experiments a piece of iodide of starch paper was exposed to the effects of the products of combustion, of something like 6,000 cubic feet of gas, and at no one time was there any discoloration of it, that is, it was exposed for about 180 hours to the products of colvbustjon of ordinary coal gas, ranging from good to inferior 1 now come to the results of my experiments.140 THE ANALYST.quality, passing through a small tube, and yet there was never sufficient sulphurous acid to tint it in any way, although part of it was continually kept moist.Another piece of the same paper, prepared in the same way, was in twenty seconds tinted to a heavy blue tint, by the combustion of on17 5 grs, of bisulphide of carbon in a room of similar sizc. I am, therefore, quite justified in saying, that vhatever the products of combustion mag be, while they are within the chimney or globe of the gas burner, yet that the moment they are discharged into the room itself, the sulphurous acid which may have been produced, is entirely oxidised and sulphuric acid is the result.Having obtained this result, I will now consider the question of the amount of sulphuric acid which can be recovered from these products of combustion, and looking at this it must not be forgotten that sulphuric acid, like all other liquids, is volatile even at ordinary temperatures, and consequently exists in the air in a state of vapour, which even at low temperatures it is extremely difficult to remove or absorb.I n the morst of my experiments, while burning in the experimental room six large burners which consumed an average of nearly 40-ft.of gas per hour, I succeeded in recovering in the form of sulphuric acid 22 per cent. of the total sulphur present in the gas, a very considerable proportion of which was present as free and not combined sulphuric acid, while, in the best of my experiments, when I was burning only 1.5-ft. of gas per hour, i.e. lighting the room in the proportion in which an ordinary dining room would be lighted, I succeeded in recovering as sulphuric acid more than 62 per cent.of the total quantity of sulphur present. Therefore nearly two-thirds of the sulphur was formed into corrosive acid, and, in my opinion, it is not only justifiable, but right to assume that the air passing away through these tubes, carried off in the form of vapour the remaining one-third as sulphuric acid vapour.It now becomes important to see to what extent these results are corroborated by other experiments which hare been made in order t o prove an opposite supposition. I would, first of all, say that the result of the exposure during the whole time oE thc iodide of starch paper proves that there was no sulphurous acid, and that, therefore, all we have to consider is, whether my experiments as to the production of sulphuric acid are capable of corroboration, and I think they are.I find, for instance, from some evidence which Dr. Odling gave in an earlier part of this year, that, burning gas containing 33 grains of sulphur per 100 cubic feet, at the rate of 15 cubic feet per hour for 5 hours consecutively, in a room having a capacity of 8,800 cubic feet he found at a height of 1-ft.6-in. from the ceiling, -160 of a grain of sulphur per cubic foot of air ; at a height of 5-ft. 6-in. from the ceiling, -056 of ti grain per cubic foot ; at a height of 3-ft 6-in. from the floor, *59 of a grain per cubic foot. I f we take the mean of thcse results, multiply them by 3,800 cubic feet, i.e.by the capacity of the room ; this would amount to as much sulphur in the form of sulphuric acid as would be produced by gas burned for 40 consecutive minutes; in other words, if the ventilation of the rooms were so bad that the air was not changed more than once in 40 minutes, Dr. Odling would have succeeded in finding the whole of the sulphur which would have been given off by the combustion of the gas.Dr. Stevenson and Dr. Russell also obtained very similar results ; their experiment8 were of a different kind, and took the form of hanging plates upon the wall in order to ascertain how much acid condensed upon the surface of the plates. Some of the plates were clean glass ones, and some were iLoistened with au alkali, but when we calculatedTHE ANALYST. 141 these results, we found that in Dr. Stevenson’s drawing room, the area of which is about 3000 cubic feet, the amount of sulphuric acid deposited on the wails of the room is about 9-4 grains per hour, or according to his figures 42 per cent. of the total quantity of sulphur present in the gas burnt. A more striking confirmation of the presence of sulphuric acid in the products of combustion can scarcely be wanted. It is quite clear, therefore, that whether the injurious effects of sulphur in gas have or have not been over- rated, sulphuric acid is the product which is formed during the combustion.

ISSN:0003-2654    

DOI:10.1039/AN8770200138

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

THE ANALYST. 141 POISONING OF FOURTEEN MEN BY SUGBR CONTAINING ARSENIC. IN THE AKALYST for August, an account was given, copied from a Glasgow newspaper, of the alleged poisoning of fourteen of the crew of the ship ( ( Crown Prince,” on her voyage between Laneton and Callao. I n the course of the voyage six of the men died, with all the symptoms of irritant poisoning, but the cause of their death was not ascertained at the time.On the arrival of the vessel in Glasgow, howeyer, a Board of Trade Inquiry was held, the result of which was that a report was made to the Board of Trade Authorities in London, to the effect, that in the opinion of the officials who conducted the Inquiry, the illness and death of the men had resulted from the use of unsound pork, a barrel of which had been opened, and a portion used, shortly before142 TEE ANALYST. the first symptoms were noticed.Before the Inquiry opened, however, the owners of the vessel had requested Mr. Tatlock, one of the Public Analysts for Glasgow, to examine some sugar which the Captain (Cochrane) suspected was the cause of the illness and death of tho men ; the result was that 139 grains of arsenious acid were found in one pound of the sugar, which was duly reported, and the report was furnished t o the officials who held the enquiry, but the fact did not seem to influence them in their opinion.I n consequence of their report, Mr. Tatlock communicated with Mr. Anderson, M.P. for Glasgow, who saw Mr. Stanhope, Secretary of the Board of Trade in London, and he at once telegraphed to Qlasgow, and indicated that the Inquirr would probably be re-opened.Shortly afterwards the Captain was apprehended on a charge of culpable homicide, or neglect of duty, by supplying unsound pork to the crew, and thereby causing their illness and death, and was tried at the Circuit Court, before the Lord-Justice-Clerk, a t Qlasgow, on the 13th September last.Several of the crew gave evidence to the effect that some rancid pork had been served out to them on a particular day, and that they were afterwards seized with sickness and vomiting of a violent and protracted character, and while some of them said that they considered the pork t o hat-e been the cause of their illness, the steward said that he never suspected the pork. * Professor Ferguson, (Chemistry), Glasgow University, and Professor Xuclagan, (Medical Jurisprudence), Edinburgh University, were called for the Crown, and corroborated the presence of arsenic in the sugar; and Dr.Dunlop, (Surgery), Anderson’s College, Dr. Moore and Dr. Johnstone gave it as their opinions, that the symptoms and the appearance of the men (some of whom were so paralysed in their lower limbs, that they were permitted to B i t in the witness-box,) distinetly indicated blood poisoning by unsound meat. Dr. Maclagan, however, was so clearly and emphatically opposed to this view, and gave his evidence in favour of the probability of arsenical poisoning, with so much force and precision, that Lord Moncrieff after consulting with the Advocate-Depute, said it was impossible, after hearing Dr. Maclagan, to go on with the case, and instructed the Jury to return a verdict of “Not Guilty.”

ISSN:0003-2654    

DOI:10.1039/AN877020141b

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

142 TEE ANALYST. ABdTRACT OF A PAPEE ON THE CONSTITUENTS OF THE IVY.- ‘( HEDERIC ACID.” BY .ROBT. H. DAVIES, F.C.S. Read: before the British Pharmaceutical Conferennos at Plymouth. AT last year’s Conference in Glasgow, I had the honour, in conjunction with Nr. C. H. Hutchinson, of reading a paper in which some of the leading characters of so-called hederic acid were mentioned. Some little additional work having been done upon this substance during the past year, I proceed t o report upon it.As already stated, so-called hederic acid consists solely of carbon, hydrogen, and oxFgen. Three analyses have already been published of this body-two in 1849 by Professor Posselt, to whom we owe its discovery, aod one in April, 1875, in Dr. Hartsen’s paper on “ A New Substance in Ivy Leaves.” This new substance I last year showed to be identical with Posselt’s hederic acid.hederic acid ” completely by the combustion process. When oxide of copper is employed 1 have never succeedcd in I have found it exceedingly difficult to burnTHE ANALYST. 143 converting the whole of the carbon into CO,. With chromate of lead better results have been obtained, but the method finally adapted was to mix the substance with a mixture of chromate of lead and bichromate of potassium in a tube, the fore part of which for 6 or '7 inches was filled with dry copper oxide.By this means I have obtained results which compare favorably with those obtained by burning the weighed substance mixed with granular oxide of copper in a stream of oxygen. The following table indicates the percentages obtained in five experiments.The first three being combinations with granular oxide of copper, in a stream of oxygen, and the two last with a mixture of chromates. Theory for I. XI. 111. 1V. Average* C16H104 Carbon ...,.. 67.88 67.37 68.03 67-41 67.63 67.66 68.08 Hydrogen ..., 9-33 9.24 9.16 9.19 9.43 9.27 9-22 Oxygen ...... 22T9 23.39 22.81 23-40 22.94 23.07 22.70 (by difference) 100~00 100*00 100-00 100~00 100*00 100*00 100~00 - - - - - - - - - - - - - - The percentage of carbon is greater in every case than was obtained by either of the experimenters before alluded to,% an error on their part which I think due to the diffi- culty of completely burning the mbstance. Attempts to produce salts of barium, calcium, potassium, sodium, aluminum, copper, and silver, have been attended with uniformly negative results; and I have no reason to doubt that my former statement that this substance is not an acid is correct.An ammo- nium compound has been produced, but the amount of ammonia is so small as t o preclude the probability of its being an ordinary salt. It is now under investigation.

ISSN:0003-2654    

DOI:10.1039/AN8770200142

出版商:RSC    

年代:1877

数据来源: RSC

摘要:

THE ANALYST, 143 ABSTRACT O F A NOTE ON HEDERIC ACID F&OM I V Y LEAVES. BY CHARLES T. ENGZETT, P.C.S. Read before the British Pharmnceutical Conference, at Plymouth. HEUEBIC ACID, when pure, is a snow-white powder, insoluble in ether, but soluble in hot alcohol. That specimen which formed the subject of the present paper, was kindly given to the author by Mr. R. H. SDaTies, and amounted to several grams only.When Mr. Davies read his paper, I suggested that hederic acid was a body constructed on the type of a saccharide, inasmuch as I had found many bodies of this constitution to give, with strong sulphuric acid, a purple colour, like to that given, as Posselt found, by hederic acid, and because this substance gives, on boiling with dilute sulphuric acid, a solution which reduces Fehling’s copper test.Since the time mentioned, I have, in conjunction with my friend Dr. H. W. Hake, published an accountt of a number of new reactions in organic chemistry, similar to the one above-described, due to hederic acid, and in the continued prosecution of‘ this study, I have subjected this last-named body to a closer examination. When heated on platinum foil, hederic acid melts to a colourless oily-like substance, which emits a dense white aromatic and inflammable vapour, and on continuing the heat, the whole of the substance boils away in this manner, leaving no ash and no charcoal.66-43 per cent. carbon, 9.5 and 9.41 per cent. hydrogen. Nay 12th, 1876. * In Hartsen’s paper the numbers are C 63.44 per cent., H 10.4 per cent.t. “ On Borne new Reactions in Orgmic Chemistry and their Ultimate Bearings.” Posselt gave 66.49 and Phnrm. Joum.,144 THE ANALYST. As already stated, it strikes with strong sulphuric acid a purple colour, which does not form immediately ; but this colour is not nearly ao intense or so beautiful as that which is immediatly formed when a trace of sugar is present, or more faintly when a drop of water is added ; furthur addition of water causes the destruction of this colour. An attempt was made by the writer to isolate sugar from the molecure of hederic acid by boiling it for a long time (twenty hours) in contact with a two per cent.solution of sulphuric acid. No visible change occurred, but the solution contained a substance much resembling sugar in its properties.The sulphuric acid was removed by baryta water, and the excels of this by carbonic anhydride, and on evaporation of the filtrate t o dryness it left a sticky transparent barley-sugar-like mass, possessed of the following characters :- It contained barium. It gave with camphor and sulphuric acid the purple colour which Hake and I have Its aqueous solution reduced Fehling’s test readily, and also nitrate of silver. Strong sulphuric acid charred it in a manner resembling the action of the acid upon After drying at loo0 it admitted of pulverization. I have no doubt that the body represents an intermediate state occurring in the spontaneous change of glacosate into glucinate of barium. Of its sugar-like character, however, there can be no doubt. ahown sugar to produce. sugar.

ISSN:0003-2654    

DOI:10.1039/AN8770200143

出版商:RSC    

年代:1877

数据来源: RSC