of the arms of the Crinoids, or in currents produced by the motions of the arms of the latter? The excrementitious matter of the Crinoid could doubtless have passed out under the foot of the Platyceras, supposing the opening in the Crinoid sometimes covered by these shells to have been the anus, but it is difficult to conceive how food could have passed in, if we suppose this opening to be the mouth. ART. IV.-On the effect of Atmospheric Air when mixed with Gas in reducing its illuminating power; by B. SILLIMAN, and HENRY WURTZ. THE data given in this article were obtained during an investigation of the Hydrocarbon Gas Process by the "Gwynne-Harris" "or American System," some notice of the results of which we propose to publish in a future number of this Journal. In the course of this investigation it became important to measure exactly the effect of atmospheric air in reducing the illuminating power of gas. Owing to a mechanical defect in the apparatus connected with the exhauster, it was found that a variable quantity of air had for some time found its way into the gas holder, the influence of which in diminishing the brilliancy of combustion was sufficiently conspicuous before the cause was ascertained. The only experiments on this subject known to us when its study was undertaken by us were those of Messrs. Audouin and Bérard (also quoted in the American Meter Cos. Pocket Almanac.) By these results the ratio of loss in illuminating power by the addition of each one per cent of air appeared to us so enormous, that we were desirous of confirming them. Subsequently we became acquainted with an important paper on this subject by Mr. Carl Schultz,† the main points of which are reproduced in this article; as they appear to have escaped attention; the author having modestly given us only his initials, and the journal in which they appeared being almost inaccessible to scientific readers. In conducting this research we soon found that the attempt to introduce by measure a given volume of air into the gas holders connected with the photometric apparatus, was attended with many sources of error, and that the requisite accuracy could be obtained only by the eudiometrical analysis of each successive * Ann. de Ch. et Phys., 3d series, vol. lxv, p. 423, 1862. experimental laboratory and apparatus at their Eighteenth-Street Station. New York, who with great liberality placed at our disposal their well appointed ously extended to us by the officers of the Manhattan Gas Light Company, in * Our labors in this research have been greatly aided by the facilities courte. opening a stop cock connected with the interior and adding plete admixture of the contents. The air was introduced by one transferred to the other and back again to secure a com ner that each could be used independently, or the contents of ers of ten cubic feet capacity each, connected in such a manmixture. The apparatus employed consisted of two gas hold 23 19. 387 433 1-61 6.54 4.95 14.81 11-28 13.76 3.53 23.83 4 83 ·501 13.32 11.71 14.81 8.67 13.07 6.14 41.46 3.54 *419 14.81 6.29 12:41 8.52 57.53 3.55 *378 15.09 weights to the counterpoise, measuring the influx by a centissimal scale of equal parts attached to the drum of each holder. This rude admeasurement was controlled by an analysis of each mixture. This required also the prior analysis of the street gas on each occasion, columns 3, 4, and 5 of the accompanying Table I, show the results of these mixtures as made known by the eudiometer. The illuminating power of each sample was determined by the Bunsen photometer on the average of fifteen successive observations of one minute each with the usual corrections. Columns 6 and 7 give these results, and in columns 1 and 2 will be found the corresponding densities determined by diffusion. Since the air added in each case is rendered as gas by the meter during the photometric measurement, it is important to determine the illuminating power of the gas alone after deducting the known volume of air present. The results of these calculations are given in column 8. In columns 9 and 10 the loss of illuminating power is given: in 8 in terms of the candle power lost for each admixture, and in 9 this loss is stated as a percentage. The ratio of loss of illuminating power in percentage volumes of gas and air is given in column 11, and in column 12 is the loss of power corresponding to each one per cent of air added. The results of the analyses and photometric measurements are more conspicuously seen in the curve projected from columns 5 and 10 of the table upon the annexed diagram, on which the vertical and horizontal scales are as 1:3. The following inferences depend upon the data herein given, viz: 1st. For any quantity of air, less than five per cent, mixed with gas, the loss in candle power due to the addition of each one per cent is a little over of a candle (·611 exactly); above that quantity the ratio of loss falls to a candle power for each additional one per cent up to about 12 per cent of air; above which, up to twenty-five per cent, the loss in illuminating power is as shown by column 12 of the table, nearly ths of a candle for each one per cent of air added to the gas. In column 11 of Table I, the ratio of loss in candle power is given in percentages for the several volumes, while in column 10 the destructive effect of air upon the illuminating power of gas is most conspicuously exhibited, twelve per cent of air destroying over 40 per cent of the illuminating power. In the diagram this loss of power is represented by the numerals in the right hand column, which are inverse to those in column 10, and stand with the maximum intensity = 100. 2d. With less than one-fourth of atmospheric air, not quite 15 per cent of the total illuminating power remains; and with between 30 per cent and 40 per cent air, it totally dis appears. Now, during December and January the hydro-carbon gas made at Fair Haven had often as much as 12 per cent of air in it; during the month of February the air by analysis averaged nearly 9 per cent; while in March after the separation of the pump from the exhaustion apparatus, the air was reduced at times to nearly nothing. By column 3 of the Table it will be observed that the air found by analysis in the street gas at the Eighteenth-Street Station of the Manhattan Gas Light Campany, New York, averaged nearly 2 per cent, and the New Haven City Gas contained about the same quantity. We allow, therefore, this quantity (2 per cent) as a normal amount of air in street gas; and consequently in the Journal of the daily operations with the hydro-carbon process at Fair Haven,* these corrections have been applied; giving in two columns the "corrected candle power," by the addition of the ratio determined in our Manhattan experiments, and the "corrected volume," or yield per pound of coals carbonized, air being deducted. It is obvious that the records of the station meter give the contaminating air as gas, and without the correction thus obtained the apparent yield is too great. In large gas-works the liability to contamination by air accidentally introduced from various causes, diminishes in proportion to the total make of gas, and an amount of air which, when diffused in a very large volume of gas, becomes insignificant, if confined to ten or fifteen thousand feet daily product, will become a most serious injury to its illuminating power. This cause of deterioration in gas has been overlooked almost entirely by gas engineers; but in all small gas-works it deserves special attention, and we have no doubt that the low illuminating power too often obtained in such works is largely due to this cause. Results of Messrs. Audouin and Bérard.-We have already alluded to these results obtained by Messrs. A. and B. which form part of an important memoir published in 1860, under authority of the French Government upon the various burners employed in gas lighting and researches on the best conditions for the combustion of gas.' Their table, which we append for the sake of comparison, shows "a considerably higher ratio of loss than we have obtained, being rather more than six per cent loss for each one per cent of air added to the The Hydro-carbon Gas Process. Report of working results on a la cale under the Gwynn-Harris Patents, Nov., 1868, to May, 1869, by Benja M.A, M.D., and Henry Wurtz, M. A., N. Y. 8vo, pp. 126, printe distribution. gas, reaching a total loss of 80 per cent with 15 per cent of air added; while we obtain 57.53 per cent loss with 16 per cent; and 93 per cent loss with 20 per cent air, while with the latter volume of air added we get 72.90 per cent loss. These differences may be accounted for by the French trials being made upon a gas of not more than 12 candles power, our trials being made on a gas averaging nearly 15 candles. Also, by the fact that in the French experiments the gas was burned from a batswing burner, ours from a standard Argand. In the experiments of Messrs. Audouin and Bérard, two gas holders of equal capacity were filled, one with standard gas and the other with the same gas mixed with 1, 2, 3, etc. per cent of air. Each fed a burner of the second class, regulated to a consumption of 140 litres of gas per hour. The illuminating power of the two were compared by making that of the pure gas equal unity. The results are given in the following Table, where each figure gives the mean of 6 or 8 concordant observations. TABLE II. Table showing the results of mixture of air with gas, by Messrs. Audouin and Bérard. By this table it appears that the introduction of 6 to 7 per 100 of air, suffices to diminish the intensity by one half, and a mixture of 20 of air with 80 of gas leaves almost no illumination. Unfortunately Messrs. A. and B. do not record the actual illuminating power of their standard gas, which however we are led to believe cannot be more than 12 candles of the English and American standard. |