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,