Increasing the Quantity of Ammonia in a Gaswork.

BRUNET.

(Proceedings of the Société Technique de l'Industrie du Gaz en France, 1898, p. 102.)

When tar is removed from the tanks, it will be found that it contains ammoniacal liquor in suspension in a minutely divided state. Various means have been tried to effect its separation from the tar, one of the most efficacious being a centrifugal apparatus; this is said to leave only 1 per cent. of liquor in the tar, but to effect this the tar must be warmed to render it sufficiently fluid. The ammoniacal water is generally, for the most part, lost, but it contains an appreciable amount of ammonia, and the Author has endeavoured to prevent this loss. Ammoniacal gas is very soluble in pure water, which will take up 1,000 volumes of the gas at 32° F. and 740 volumes at 59° F.

A laboratory experiment proves this fact in a striking manner. If a flask is filled with ammoniacal gas over mercury, and stopped with a cork, through which a small glass tube, closed at the exterior end, is passed, and if this end is broken under water, the water will be found to rush into the flask, filling it in a very short time. This experiment suggested the idea of removing, by one operation, the greater part of the ammonia suspended in the tar in the tanks. The plan consists simply in constantly maintaining a layer of water, at least 3 feet deep on the surface of the tar. By this means the ammoniacal gases are aspirated from the layer of tar next to the water, and each time that there is a movement in the mass of tar the pockets of liquor, large or small, tend to rise towards the surface, where the ammonia they contain becomes dissolved in the water above. To maintain a constant layer of clean water on the tar, it is sufficient to change the water so soon as it has a density of 11° to 2° Beaumé. This plan has been used by the Author for 2 years, and he estimates that the quantity of water put into the tanks amounts to 132,129 gallons per annum, and the yield of ammonia has been successively increased from 4.10 to 4.36 and 4.83 lbs. per ton of coal carbonised, without the help of any special apparatus for collecting the ammonia, the gas being only washed in two ordinary coke scrubbers, one watered with weak ammoniacal liquor, and the other with clean water.

C. G.

Street-Lighting with Incandescent Gas-Burners in Munich. Dr. E. SCHILLING.

(Journal für Gasbeleuchtung, 1898, p. 397.)

Incandescent gas-burners are at present extensively used for both private and street lighting. In Munich they have been used for the latter purpose since October, 1897, there being at present 5,100 such burners fixed, all of which are provided with holophane glasses. The most frequented streets in Munich, especially in the old town, are lighted by electricity, and, in consequence of the increased light so obtained, it was found necessary to improve the gas-lighting in the other parts of the town. It was therefore decided to fit up the whole of the public gas-lamps with incandescent burners, and the conversion was completed by the 1st October, 1897, so that from that date to 1st April of this year, or for six months, the cost of working on a large scale, including maintenance, could be determined. The renewal of the mantles is an important item in the cost of maintenance, and the information available on this point varies considerably. In Munich the renewals of the chimneys has been at the rate of 2.011, and of the mantles at the rate of 4.2 per lamp per annum. A detailed estimate is given of the total cost, including all items, such as inspectors, fitters, labourers, workshop rent, repairs to burners, and interest and sinking funds on the original outlay. This amounts to 148. 5d. per burner per annum, with the mantles costing 10 2d. each. The price of the mantles has since been reduced to 6d. per mantle, which reduces the cost of maintenance to 128. 8d. per lamp per annum, but the town pays only 88.

According to the annual report of the Munich Statistical Office for 1896, there were 830 electric arc-lamps in use in the city, which cost £22,795 for the year. The amount paid by the town for 5,100 incandescent gas-lamps is at the rate of £11,965 per annum, so that an electric arc-lamp costs £27 9s., as compared with £2 78. for an incandescent gas-lamp.

The experience in Munich is that, in streets where there is considerable traffic, the electric arc-lights are useful, but that the incandescent gas-lights are eminently adapted for general street lighting.

C. G.

The Methods of Estimating the Volume of Carbonic-Acid Gas.

GERDA TROILI-PETERSSON.

(Zeitschrift für Hygiene, 1898, p. 331.)

1

Reference is made to a previous communication on this subject in which attention was directed to the mode of employing the Pettersson-Palmqvist apparatus, as modified by the Author, for experiments in regard to ventilation. Several varieties of similar apparatus, small in size and free from complex parts, have already been introduced, and exception is taken by the Author to the statement that the modified form of the above apparatus gave results which were inferior in point of accuracy to that described, for instance, by Bleier. It is shown that the figures relate not as assumed to percentages but to the parts per 1,000, and that while the greatest difference obtained between two estimations of the same sample of air by the use of the Author's portable apparatus was but 0.07 part per 1,000, the original form of the Pettersson and Palmqvist portable apparatus gave readings which might vary as much as 0.15 part per 1,000. Some later trials conducted by the Author with the two forms of portable apparatus are described, and in one case the air in a dwelling-room was found, after it had been occupied by one individual for 9 hours, to contain 0.82 part of carbonic-acid gas per 1,000 parts, the initial composition having been 0.65 part per 1,000. Some larger subsequent increases were suspected to be due to the escape into the room of the products of combustion in a close stove. In order to decide this point some tests were made with the stove by closing the valve, when the volume of carbonic-acid gas in the atmosphere of the room rose rapidly to 1.40 part per 1,000. Attention is directed to the errors likely to be caused in the use of all kinds of apparatus of this nature by variations in temperature, and some observations are given to illustrate this source of inaccuracy. For instance, a set of readings in two school-rooms are given in a Table showing the volume of carbonicacid gas present at various short intervals, with the values obtained by the readings of different instruments. In these latter tests the opening of the windows between the lessons and the changes in the temperature induced great differences in the results. G. R. R.

1 Minutes of Proceedings Inst. C.E., vol. cxxxi. p. 476.

Acetylene Gas from the Hygienic Point of View.
JOSEPH VÉRTESS.

(Gesundheits-Ingenieur, 31 July, 1898, p. 225.)

The employment of acetylene is already becoming widespread, and while much has been written concerning its composition, its mode of production, and the burners best adapted for its combustion, little is known with respect to its influence upon health. These facts can conveniently be discussed under three heads:(1) Acetylene gas when mingled with the atmosphere; (2) products of combustion in the case of acetylene, and (3) impurities in acetylene. It is pointed out that in consequence of the fact that calcium carbide is hygroscopic, this substance is liable to cause the spontaneous evolution of gas by gradually attracting moisture from the atmosphere. An American physician, Dr. Birchmoore, has maintained that even a volume of 0.01 per cent. of this gas in the atmosphere produces headache and sickness, but according to the Author this is a ridiculous exaggeration. Trouvé has asserted that this gas relieves colds and coughs. According to Gréhant even 20 per cent. of this gas in the atmosphere produces no evil effects, when breathed by animals, but with 40 per cent. the mixture was speedily fatal. The Author discusses the volume of gas absorbed by water, and calls attention to the fact that acetylene, when it constitutes one-twelfth part of the volume of air with which it is mingled yields an explosive mixture.

Under the second head, after a full consideration of the gases caused by burning pure acetylene, and after comparing them with those obtained by the combustion of common coal-gas, it is affirmed that acetylene under similar conditions, that is to say, with the production of an equal amount of light, vitiates less than one-half the volume of air that coal-gas does, and gives rise to far fewer products of combustion. An enumeration follows of the impurities likely to be present in acetylene; these are caused by certain substances found in the raw materials used in making the calcium carbide, and they consist mainly of phosphorus, sulphur, silicon and nitrogen compounds. The Author maintains that these substances, except perhaps phosphorus, cannot, with common care in the manufacture, exist in sufficient quantities to cause any ill effects to health.

G. R. R.

The Electricity Works of the Town of Schaffhausen.

K. P. TAUBER.

(Schweizerische Bauzeitung, 1898, p. 167 et seq. 8 Figs.)

In the spring of 1895 the Town Council of Schaffhausen opened a competition for designs of an electricity works, and the plans of the Oerlikon Company for a single-phase alternating-plant were accepted. Work began in the spring of 1896, and in February, 1897, the works were taken over by the town. The energy is obtained from the turbines on the Rhine, installed in 1887-90 by the Water-Power Company; the plant is itself an extension of one put down 30 years ago for rope and shaft transmission of power to the district. In the new turbine house there are five Jonval turbines with vertical shafts by Escher, Wyss & Company. Each develops 300 HP. at 48 revolutions per minute; two are used to drive direct-current dynamos for the power-transmission to the Schaffhausen worsted-spinning mill, and two others for the electricity works now being described. Each turbine drives one dynamo through bevil wheels. Originally it was intended to fix a pulley on the shaft and drive the dynamo by ropes, but the more direct method was adopted. The possibility of placing the alternator direct on the vertical shaft was not overlooked, but the low speed and lack of space rendered it impracticable. The generators run at 167 revolutions, and give 100 amperes at 2,000 volts, with a periodicity of 50 per second, and they are of the Oerlikon inductor type. The exciter is a shunt wound machine giving 120 amperes at 50 volts, and 420 revolutions. Full details are given of the machines, and also of the switchboard. All the feeders are laid underground and are of the concentric lead-covered type, the potential is transformed down, and the secondary network in the town is all on the twowire system and underground, while in the suburbs it is on the three-wire system, carried overhead. There are nineteen transformer stations of three types, the underground chamber, the iron chamber like a pillar letter-box, and a similar chamber with a lofty pole for the overhead wires. There are only two sizes of transformers, the 10-kilowatt and 20-kilowatt, and the primary current is transformed to 120 volts. The maximum output of the station at present is about 100 amperes at 2,110 volts, and it has been at work about 12 months.

E. R. D.