SECONDARY BATTERIES.
The application of secondary or storage batteries to electrical traction has been accomplished in a number of cities, with a varying amount of success. Roads equipped by batteries have now been sufficiently long in operation to allow us to draw some conclusions as to the practical results obtained and what is possible in the near future. The advantages which have been demonstrated on Madison Avenue, in New York; Dubuque, Iowa; Washington, D.C., and elsewhere, may be summarized as follows:
First. The independent feature of the system. The cars independent of each other, and free from drawbacks of broken trolley wires; temporary stoppages at the power station; the grounding of one motor affecting other motors, and sudden and severe strains upon the machinery at the power station, such as frequently occur in direct systems; the absence of all street structures and repairs to the same, and the loss by grounds and leakages, are also very considerable advantages, both as to economy and satisfactory operation.
Second. The comparatively small space required for the power station. Each car being provided with two or more sets of batteries, the same can be charged at a uniform rate without undue strain on the machinery of the power station, and as it can be done more rapidly than the discharge required for the operation of the motors, a less amount of general machinery is necessary for a given amount of work.
Another and important advantage of the system is the low pressure of the current used to supply the motors, and the consequent increased durability of the motor, and practically absolute safety to life from electrical shock.
It has been demonstrated also that the cars can be easily handled in the street; run at any desired speed, and reversed with far more safety to the armature of the motor than in the direct system. The increased weight requires simply more brake leverage.
The modern battery, improved in many of its details during the last year, is still an unknown quantity as to durability. There is the same doubt concerning this as there was at the time incandescent lamps were first introduced. At that time some phenomenal records were made by lamps grouped with other lamps.
Similarly, some plates appeared to be almost indestructible, while others, made practically in the same manner, deteriorate within a very short time. It is, consequently, very difficult to exactly and fairly place a limit on the life of the positive plates as yet. Speaking simply from observation of a large number of plates of various kinds, I am inclined to put the limit at about eight months; though it is claimed by some of the more prominent manufacturers—and undoubtedly it is true in special cases—that entire elements have lasted ten months, and even longer.
It must be remembered, however, that the jolting and handling to which these batteries are subjected, in traction work, increases the tendency to disintegrate, buckle and short circuit, and that the record for durability for this application can never be the same as for stationary work. A serious inconvenience to the use of batteries in traction work is the necessary presence of the liquid in the jars. This causes the whole equipment to be somewhat cumbersome, and unless arranged with great care, and with a variety of devices lately designed, a source of considerable annoyance.
The connections between the plates, which formerly gave so much trouble by breaking off, have been perfected so as to prevent this difficulty, and the shape of the jars has been designed to prevent the spilling of the acid while the car is running. The car seats are now practically hermetically sealed, so that the escaping gases are not offensive to the passengers.
The handling of the batteries is an exceedingly important consideration. Many devices have been invented to render this easy and cheap. I have witnessed the changing of batteries in a car, one set being taken out and a charged set replaced by four men in the short space of three minutes. This is accomplished by electrical elevators, which move the batteries opposite the car, and upon the platforms of which the discharged elements are again charged.
The general conclusions which the year's experience and progress have afforded us an opportunity to make may be summarized as follows:
Storage battery cars are as yet applicable only to those roads which are practically level; where the direct system cannot be used, and where cable traction cannot be used; and applicable to those roads only at about the same cost as horse traction.
I feel justified in making this statement in view of the guarantees which some of the more prominent manufacturers of batteries are willing to enter into, and which practically insure the customer against loss due to the deterioration of plates: leaving the question of the responsibility of the company the only one for him to look into.
Abstract of a paper read before the American Streel Railway Association, Oct. 23, 1891.
ON THE ELIMINATION OF SULPHUR FROM PIG IRON.[1]
By J. MASSENEZ, Hoerde.
If in the acid and the basic Bessemer processes the molten pig iron is taken direct to the converter from the blast furnace, there is the disadvantage that the running of the individual blast furnaces can hardly ever be kept so uniform as it is desirable should be the case in order to secure regularity in the converter charges. In the manufacture of Bessemer steel the variable proportions of silicon and of carbon here come chiefly under consideration, while in the basic process it is chiefly the varying proportions of silicon and of sulphur; and in cases where either ores containing variable percentages of phosphorus, or puddle slags, are treated, the varying proportion of phosphorus has also to be considered. This disadvantage of the irregular composition of the individual blast furnace charges is obviated in a simple and effective manner by W.R. Jones's mixing process. In this as much pig iron from the various blast furnaces of a works as is sufficient for a large number of Bessemer charges, say from seven to twelve charges, or, in other words, from 70 to 120 tons of pig iron, is placed in a mixing vessel. Only a portion of pig iron placed in the mixer is taken for further treatment for steel, while new supplies of pig iron are brought from the blast furnace. In this way homogeneity sufficient for practical purposes is obtained.
In the treatment of phosphoric pig iron, which is employed in the production of basic steel, it is, however, not sufficient merely to conduct the molten pig iron in large quantities to the converter in a mixed condition, but the problem here is to render the proportion of sulphur also independent of the blast furnace process to such an extent that the proportion of sulphur in the finished steel is so low that the quality of the steel is in no way influenced by it. The question of desulphurization has, especially of late years, become of the utmost importance, at any rate for the iron industry of the Continent. By the great strike of 1889, the German colliers have succeeded in greatly improving their wages; and with this increase in wages not only is there a distinct diminution in the amount of coal wrought, but, unfortunately, the coal produced since then is raised in a much less pure condition than was formerly the case. Consequently the proportion of sulphur in the coke has considerably increased. Whereas formerly this proportion did not exceed one per cent., it has now in many cases risen to 18 per cent.; so that an unpleasant ratio exists between the wages of the workmen and the amount of sulphur in the coal raised. It is therefore not remarkable that, even when ores fairly free from sulphur are treated, it easily happens that a sulphureted pig iron is obtained.
In order to effect satisfactory desulphurization, attention has been bestowed on the fact that iron sulphide is converted by manganese into manganese sulphide and iron. If sulphureted pig iron, poor in manganese, is added in a fluid condition to manganiferous molten pig iron, poor in sulphur, the metal is desulphurized, and a manganese sulphide slag is formed. It may be urged that it does not seem necessary to effect the desulphurization by means of the reaction of the manganese and iron sulphide outside of the blast furnace, as it is possible, by suitably directing the blast furnace, by the employment of manganiferous ores or highly basic slag, so to desulphurize the iron in the blast furnace itself that it would be unnecessary further to lower the percentage of sulphur. Every blast furnace manager, however, will have observed that, even with every precaution in the blast furnace practice, pig iron will often be obtained with so high a percentage of sulphur as to render it useless for the Bessemer acid or basic processes. If the desulphurization in the blast furnace is carried sufficiently far, it is always necessary to work the furnace hot, and thus to obtain hotter iron than is desirable for further treatment in the converter. On the other hand, the method of further desulphurization outside the blast furnace, described in this paper, presents the double advantage that part of the blast furnace can be kept cooler, and thus lime and coke be saved, and that there is a certainty that no red-short charges are obtained in the treatment in the converter, while the pig iron passes to the converter at a suitable temperature.
A further advantage presented by the direct process described in this paper is that the Bessemer works is independent of the time at which the individual blast furnaces are tapped, as the pig iron required for the Bessemer process can be taken at any moment from the desulphurizing plant. In Hoerde, where the mixing and desulphurizing process has for a considerable time been regularly in use, it has been found that all the chief difficulties formerly encountered in the method of taking the fluid pig iron direct from the various blast furnaces to the converter have been obviated. At Hoerde the mixing and desulphurizing plant shown in the accompanying engravings is employed. This apparatus holds 70 tons of pig iron. It is, however, advisable to have an apparatus of greater capacity, say 120 tons. The apparatus has the shape of a converter, and the hydraulic machinery by which it is moved is simple and effective. An hydraulic pressure of eight atmospheres is sufficient to set it in motion. The vessel is provided with a double lining of firebricks of the same quality as those used for the lining of blast furnaces. This lining is gradually attacked only along the slag line, and does not require repair until it has been in use for some six weeks. Further repairs are then necessary every three weeks. Only the few courses of spoilt bricks are renewed, and for the repairs, including the cooling of the vessel, a period of two or three days is required. At the end of the week the vessel is kept filled, so that its contents suffice for the last charge to be blown on Saturday. On Sunday night the vessel is again filled. The consumption of manganese is very low; theoretically, it is the quantity required for the formation of manganese sulphide, and in practice it has been found that this amounts to about 0.2 per cent. The proportion of manganese which the desulphurized pig iron coming from the vessel should contain is best kept at about 1.5 per cent. in order to render the desulphurization as complete as possible. Thus, a mean proportion of 1.7 per cent. of manganese in the pig iron passing into the vessel is more than sufficient to effect a thorough desulphurization. Indeed, 1 to 1.2 per cent. of manganese is sufficient to effect a satisfactory desulphurization. For the extent of the removal of the sulphur, the temperature and the duration of the reaction are of importance. It has been found that if highly sulphureted pig iron is poured from the blast furnace into the desulphurizing vessel, fifteen to twenty minutes are sufficient to effect the desulphurization requisite for the steel process. The part played by the duration of the process is seen from the results obtained with the last charges, if the vessel is emptied at the end of the week without fresh pig iron being added from the blast furnace. If, for example, 60 tons of pig iron with 0.065 per cent. of sulphur remain in the vessel, the proportion of sulphur with the last charges falls to 0.03 per cent. The iron in the vessel remains sufficiently fluid for several hours. When necessary, a little wood is thrown in. It has been found quite unnecessary to obtain heat by passing and burning a current of gas above the bath of metal.
A number of results, showing the separation of sulphur at the Hoerde Works, was published a few months ago[2] by Professor P. Tunner, one of our honorary members.
The totals represent, respectively, 138,500 kilogrammes of pig iron and 98,654 kilogrammes of sulphur.
Thus, from 138,500 kilogrammes of pig iron there has been eliminated 179,577-98,654 = 80,923 kilogrammes of sulphur, or, in other words, 45.063 per cent.
The proportion of sulphur in the slags rises with that in the iron from the blast furnace to 17 per cent., an inappreciable portion of the sulphur of the slag being oxidized to sulphurous anhydride by access of air. An analysis of the slag yielded the following results:
| Per cent. | |
| Sulphur | 17.07 |
| Manganese | 30.31 |
| Phosphoric anhydride | 0.61 |
| Iron | 7.13 |
| Bases | 35.04 |
An analysis of an average sample gave:
| Per cent. | |
| Manganese sulphide | 28.01 |
| Manganous oxide | 20.23 |
| Ferrous oxide | 25.46 |
| Silica | 18.90 |
| Alumina | 5.00 |
| Lime | 3.53 |
| Magnesia | 0.43 |
The great convenience and certainty presented by the method described in this paper will in all probability lead to its general adoption. As a matter of fact, several works are now occupied with the installation of this mixing and desulphurizing plant.
Paper read before the Iron and Steel Institute.
"Oesterreichische Zeitschrift fur Berg und Huttenwesen," 1891, No. 19.
ON THE OCCURRENCE OF TIN IN CANNED FOOD.
By H.A. WEBER, Ph.D.
The following investigation of the condition of foods packed in tin cans was prompted by an alleged case of poisoning, which occurred at Mansfield, Ohio, in April, 1890. A man and woman were reported to the writer as having been made sick by eating pumpkin pie made from canned pumpkin. The attending physician pronounced the case one of lead poisoning. The wholesale dealer from whose stock the canned pumpkin originally came, procured a portion of the same at the house where the poisoning occurred, and sent it to the writer for examination.
The results of the examination as reported in Serial No. 552, below, showed that the canned pumpkin contained an amount of stannous salts equivalent to 6.4 maximum doses and 51.4 minimum doses of stannous chloride per pound. On being notified of this fact, the dealer sent a can of the same brand of pumpkin from his stock. The inner coating of the can was found to be badly eroded, and upon examination, as reported in Serial No. 563, below, one pound of the pumpkin contained tin salts equivalent to 7 maximum and 56 minimum doses of stannous chloride.
The unexpected large amount of tin salts in such an insipid article as canned pumpkin, and the claimed ill effects of the consumption of the same, suggested the advisability of extending the investigation to other canned goods in common use. Accordingly a line of articles was purchased in open market as sold to consumers, no pains being taken to procure old samples. The collection embraced fruits, vegetables, fish and condensed milk. With the exception of the condensed milk, every article examined was contaminated with salts of tin. In most cases the amount of tin salts present was so large that there can be no doubt of danger to health from the consumption of the food, especially if several kinds are consumed at the same meal.