DE162199C - - Google Patents

Description

IMPERIAL

PATENT OFFICE.

The application of iron-oxygen compounds as an effective mass for negative Pole electrodes of alkaline collectors are no longer new. First from Pollak (German Patent Specification 107727) and recently especially by Edison are different Methods for making iron electrodes are given.

The main difficulty in using iron-oxygen compounds to the specified The goal of many of them is the impossibility, they electrolytically to reduce.

Edison has made several claims in the past that everyone is dry Oxygen compounds in iron are not reduced by the galvanic current could (e.g. Transactions of the Americ. Institute of Electr. Engineers, Vol. XVIII, No. 5, p. 342) and therefore manufactures the iron electrodes from iron monosulfide, the through desulfurizes the galvanic current and converts it into iron or iron-oxygen compounds (British Patent 2490/1901, American Patent 678722).

In the British patent specification 10505/1901 and the American patent specification 700136, however, Edison explains that anhydrous iron oxide can still be used, ie can be reduced by the galvanic current. He produces this "anhydrous iron oxide or a mixture of anhydrous iron oxide and iron compounds with less oxygen" in two different ways. Either the anhydrous iron oxide Fe ₂ O _{8 is} partially reduced in the heat in a stream of hydrogen gas or iron is annealed with the admission of air and the oxide layer that has formed is removed after cooling. The latter should then contain a considerable fraction of iron oxide and poorer oxygen compounds, which are protected from decomposition by being mixed with air-resistant iron oxides. In British patent specification 10505/1901, the product is described as a black mass, the particles of which consist of metallic iron, iron oxide and magnetic iron oxide in a very finely divided state, predominantly of electrolytically attackable iron oxide, while the metallic iron is caused by the current only slowly oxidized and the magnetic oxide is hardly ("scarcely") reduced.

The glowing of the iron in the air must not be allowed in the Edison 'see process be extended for a long time, because otherwise the content of the useful less oxygenated Connections are lower, that of iron oxide, on the other hand, is greater (cf. the British. Patent 10505/1901).

Contrary to Edison's assertion that the magnetic oxide Fe ₃ O _{4 cannot be used} because of its low reducibility, it has now been found that the magnetic oxide Fe ₃ O _{4 can} nevertheless be used well, especially if it is magnetically removed from the after the

position by annealing iron in air or by reducing Fe ₂ O ₃ in a stream of hydrogen, the iron oxide Fe O and iron oxide Fe ₂ O ₃ that are always added to it is freed after the crude product initially obtained in the specified process, consisting of a mixture of different oxidation stages ( Hammer blow) was finely powdered.

ίο To show that there is a new effect in in terms of capacity, durability, etc. by using magnetically cleaned A number of tests have been carried out by of which the following two are given as examples.

In both cases, element 1 consisted of magnetically cleaned hammer blows, element 2 of hammer blows of exactly the same origin (forge waste), but which had not been subjected to magnetic cleaning and therefore contained a large amount of iron oxide Fe ₂ O ₃ . Both masses were evenly and finely powdered, and 20 percent flake graphite was added to both to produce the necessary internal conductivity.

The two elements were in the same

Circuits connected in series and were therefore made in exactly the same way treated. In each element there were two plates made with a hammer opposite bare nickel sheets. 20 percent potassium hydroxide was used as the electrolyte.

As is well known, the discharge of an iron electrode takes place in two stages, the voltage curve therefore shows two sharp kinks, the correspond to the termination of the two reactions.

The average voltage of the first part of the discharge is around 0.2 volts higher than that of the second and is primarily in the alkaline collectors exploited (first capacity), while the second discharge is, so to speak, only as Reserve should serve.

From the fact that the discharge curve of an iron electrode shows two stages, it follows that the oxidation of the metallic iron present in the charged electrode takes place in at least two stages, namely first to Fe O or Fe ₃ O ₄ and finally to Fe ₂ O ₃ . It is probable that the latter does not always occur in the iron electrode of the alkaline collector, because good iron electrodes do not look red through and through, but black-brown, even after a complete discharge. The polarization of the oxygen separation therefore generally does not reach the high value required for the formation of Fe ₁ , O _3. Only if particles of Fe ₂ O ₃ are already present can this happen to them, and these therefore have a triggering effect on the formation of the last oxidation stage.

The -Fe ₂ O ₃ can only be reduced again with difficulty, and this explains why the capacity of the iron electrodes is adversely affected as the _{formation of Fe 2} O _{3 progresses.}

Is an iron electrode made of Fe ₃ O ₄ must therefore be useful if the Fe ₃ O ₄ in some way (eg., By magnetic purification) from the always admixed _s Fe ₂ O ₃ free.

1st attempt.

First capacities in ampere hours.

Amps 1. cleaned 2. uncleaned

5 » ⁰⁰ 5.0 3.33

5.00 6.67 4.17

4> °° 9'33 '6.33

6.00 10.0 8.0

6.00 13.5 6.0

6.00 10.5 4.5.

Second attempt.

First capacities in ampere hours. Discharge 1. cleaned 2. uncleaned
No. I 5.25 4.50

14 9> ⁰⁰ 8.25

46 5.25 3.00

- 88 5.25 4.50

- 104 6.00 5.25

- 135 6.75 6.00

- 195 11.00 5.00.

The strength of the discharge current was here consistently three amps.

The gradual increase in capacities is due to that which occurs over time better formation of the iron mass.

From these figures it can be clearly seen that the _{plates made from purified Fe 3} O ₄ correspond to those made from uncleaned! Hammer blow are considerably superior in capacity, and that this becomes more pronounced the more discharges are made, i.e. the more the traces of Fe ₂ O ₃ present in the uncleaned hammer blow from the beginning triggering the formation of further quantities which cannot be reduced in the sense of what has been said above Iron oxide Fe ₂ O ₃ can cause.

The manner in which the hammer blow, which is technically obtained by annealing iron, is freed from added Fe ₂ O ₃ is completely irrelevant in itself. Magnetic cleaning is just as convenient

and probably also given the only practically useful method.

Claims (1)

Patent claim: Process for producing the effective mass for negative pole electrodes of alkaline collectors using iron hammer blow, characterized in that only the magnetic iron oxide (Fe ₃ OJ extracted from the hammer blow) is used.