October 17, 1884.] 



SCIENCE 



387 



to one plate, hydrogen to the other. For a new exper- 

 iment 1 have taken solutions which suffer decompo- 

 sition without delivering free hydrogen and oxygen. 

 I have taken, for instance, solutions of the sub-salts 

 of lead. A current causes decomposition, and a depo- 

 sition upon one plate of peroxide of lead, and, upon 

 the other, of metallic lead. For instance : I have taken, 

 for one plate, a plate of carbon, and, for the other, a 

 plate of lead. A solution of a low sub-salt of lead 

 was used as an electrolyte. By passing a current of 

 electricity through it, the action is to raise the sub- 

 salt to a proto-salt. This takes energy, which is 

 absorbed by the chemical action. Then the charge 

 of electricity is returned until the peroxide of lead 

 has again entered the solutions, and the lead has also 

 entered into the solution. The action of the char- 

 ging current of electricity is to raise the electrolyte to 

 an acid condition; but the charging action is stopped 

 before that point is reached, because the end would 

 be defeated in passing it. I am also carrying on 

 some experiments in the way of storage for elec- 

 tricity or in the use of secondary batteries. I can 

 hardly give particulars, except this: the idea is to 

 preserve the integrity of the plate — of the inside 

 plate — for an indefinite length of time, say, as long 

 as may be practically worth while. So far, after 

 some months' use, I have been able to oxidize the 

 plate to the desired depth (say, one-sixteenth of an 

 inch), and preserve a backing of metallic lead. Under 

 this change, if my theory and practice be correct, I 

 will not be obliged to replace, as in the present known 

 storage-batteries, the oxide plate. 



Prof. Charles H. Koyle. — I should like to say 

 something in reference to the theory of the secondary 

 battery. There are no substances which, placed in 

 juxtaposition in a secondary battery, will give the 

 electromotive force that the peroxide of lead, and 

 the lead of the Plante cell, laid opposite to each 

 other, will. It remains as it was in 1859, when 

 Pi ante experimented and wrote. I have experiment- 

 ed upon other substances ; and, although my experi- 

 ence has not been exactly useless, it has been the 

 next thing to it. 



The necessities of the plate, then, are the only 

 difficulties to be considered. They are three, and 

 they are very simple ones. First, the plate made must 

 be a conductor of electricity, and that leaves us the 

 metals. The plate, in the second place, must resist 

 the ordinary action of sulphuric acid: that leaves 

 us lead and four or five expensive metals, — platinum, 

 and so on, and gold and carbon. Our list is very 

 much reduced, as we have practically, for this pur- 

 pose, only carbon, as the expense of the other metals 

 is too great to allow them to be used extensively for 

 commercial purposes. 



Now, when we get the third and last condition, — 

 and that is, that the plate must resist both electro- 

 lytic action and the oxidizing action of the current, — 

 lead will resist the electrolytic action of the current 

 moderately well. But the oxidizing action of the 

 plate reduces the lead to a peroxide in a very short 

 time. That leaves us only one thing for a secondary 

 battery of the future, — carbon. 



I think there is no way of upsetting that very short 

 argument. I should be very glad to know if there is. 

 Now, then, the manufacturer of the carbon plates 

 called good, makes plates which shall contain a very 

 large amount of the substance, because the capacity 

 of the storage-battery depends entirely upon the 

 amount of lead and peroxide of lead which you can 

 put upon these plates. They are the substances that 

 you will have to depend upon for your electricity. 

 Of course it is not necessary to say that they will 

 answer the purpose : they are the substances in which 

 the chemical action takes place. 



Now, it is possible to take carbon and to manu- 

 facture carbon plates by the ordinary method. Take 

 ground charcoal, ground gas-carbon, ground flint, 

 and mix gas-tar with it, or molasses, or any hydro- 

 carbon. This is put into a press and the shape is 

 given to it; and then it is put into a closed furnace 

 and carbonized, so as to drive off the gas, and leave 

 the carbon free. Those plates are pretty good for 

 ordinary primary batteries ; but when your lead con- 

 tains a lot of little holes, very much as the lead now 

 in use does, the plate is very apt to disintegrate. 

 There is such an enormous amount of surface ex- 

 posed, that the action of the cell is apt to disin- 

 tegrate the plate, and the metal will scale off. A 

 better way to make the plate is then to be considered. 

 There is a method of making these plates which is 

 very much liked, — a method in use by the U. S. 

 lighting company in the manufacture of carbon for 

 their incandescent lamps; that is, to take celluloid 

 and put it through some chemical operation which 

 deprives it of a part of its gum, thereby leaving a sub- 

 stance very easily carbonized. That substance may 

 be cut into any shape of plates desired. You can 

 make some of these plates thick, and some thin, and 

 you will always have a good plate. It is not very 

 strong, but it is a good plate. Another method, 

 which I myself have used, I have found to work very 

 well, and I shall have more to say about it in the 

 course of a few minutes. At present I can only tell 

 you the general method. I take gas-tar and put it 

 in a closed furnace, and drive out the gas, and so 

 get rid of the ordinary illuminating-gas, the heavier 

 gas, which is condensed as it passes through the tubes. 

 The constitution of the coal-tar depends, first, upon 

 the constitution of the coal; in the second place, 

 upon the temperature at which the gas is driven out. 

 The object is to get out the lighter parts of the coal- 

 tar. Coal-tar is a very composite substance. The 

 physical qualities of coal-tar vary very much, accord- 

 ing to the temperature at which the gases were 

 originally driven out, and, again, according to the 

 temperature at which evaporation is carried on. It 

 requires months of experiments, as I have already 

 said, before one can determine what is needed. This 

 coal-tar, when it is thus taken and evaporated, and 

 brought down to a requisite consistency, which is a 

 matter of experience, is taken and put into a box 

 prepared for the purpose, and put in an oven which 

 is closed. The tops of these vessels are covered with 

 sand, and one thing and another, in the ordinary way, 

 to prevent the presence of air; then the heat is 



