390 



SCIENCE 



[Vol. IV., No. 



battery composed of carbon plates and one composed 

 of lead plates. I do not see myself the reason for 

 an expression of the opinion that the Plante bat- 

 tery is decidedly more scientific than any other bat- 

 teries composed of a plate of polarizing substance 

 distinct from a plate of lead. It is easy to construct 

 a Faure battery that will last forever, if you only 

 make the plates large enough. Lead has some weight, 

 as is well known; and, when you are going to make 

 a Plante battery of sufficient size to last any length 

 of time, you will have to make a secondary battery 

 of enormous weight. For any other purpose than 

 putting it down in the cellar to stay, the weight is a 

 great factor. I think that a lead plate a foot square, 

 the ordinary size, will weigh something in the vicinity 

 of six pounds, — I do not guarantee that exactly, but 

 I believe it is in the neighborhood of six pounds, — 

 and a square of carbon plate of the same size weighs 

 about three- fourths of a pound. Now, a battery 

 made of eleven plates of lead of this size gives you 

 something like sixty or seventy pounds. If you want 

 to use electromotive force, as in some cases you do, 

 of a hundred volts, you have a great weight: it would 

 be fifty of those cells, of sixty pounds each, which 

 would give you about three thousand pounds; and 

 that is altogether apart from the weight of the elec- 

 trolyte and the box. Carbon plates will make a dif- 

 ference of about twenty per cent, and the carbon 

 plate has the advantage of always remaining intact. 

 It will not disintegrate, and will remain permanent 

 as long as the box will, or any thing else about it. 



Mr. Elthu Thompson. — I should like to have a 

 method which will tell whether the plates will disin- 

 tegrate or not. Consider the plates that received the 

 deposition of peroxide of lead. Suppose we were to 

 select one particle of oxide which has been formed 

 from the surface of the lead: what will be the elec- 

 tro-chemical conditions of that particle ? Evidently 

 the peroxide itself is in an electro-negative condition, 

 far more so than the lead plate: consequently it will 

 set up an open circuit, and distribute its oxygen more 

 or less to the surrounding lead, and thereby eat into 

 the lead deeper and deeper, destroying the life of the 

 battery in time. It would seem, from this considera- 

 tion alone, that the lead-battery is certainly limited 

 in its life. 



Let us take the case of the carbon plates. Has it 

 yet been proved that carbon is stable in the presence 

 of peroxide of lead, in contact ? Perhaps this may 

 disintegrate the carbon, and oxidize it into oxide of 

 carbon, and at the same time reduce the peroxide 

 of lead to the teroxide of lead (Pb0 3 ). 



We have here two different substances, one highly 

 electro-negative; and the carbon, perhaps, may be 

 inert, and then it may be different in electromotive 

 force ever so slightly, and we will have a local circuit 

 which will take oxygen from the peroxide of lead, 

 and oxidize the carbon. If we wish to make a test 

 of that, let us take a massive piece of peroxide of 

 lead and a specimen of the carbon which is to be 

 tested, and place them in an electrolytic liquid (for 

 instance, dilute sulphuric acid), and see whether 

 we have a difference of electromotive force between 



those two substances, putting in the circuit some 

 means of testing a feeble current. If there is no 

 such difference, the stability of carbon in contact 

 with the peroxide of lead would be established. It 

 may be, also, that the states in which carbon is 

 known to exist may control the matter to some de- 

 gree. It is well known, that if we take a stick of 

 carbon, and put a current through it of a sufficient 

 degree to almost vaporize the carbon, it undergoes a 

 certain change of condition into the graphitic variety, 

 and, in fact, it takes a plastic form, as I have often 

 observed. You can take this carbon and use it, or 

 any portion of it, to write with as you would write 

 with a lead-pencil: whether it would be suitable in 

 that form is another question. 



Professor James Dewar. — There is one point I 

 have noticed that is of practical use in reference to 

 secondary batteries, and that is as to the inequalities in 

 the various styles of batteries. I have had an expe- 

 rience of six months with one form of storage-bat- 

 tery, — the commercial battery as it is now in use on 

 a lamp-circuit. As it is arranged, it is used for light- 

 ing forty incandescent lamps. We have only ten or 

 twelve of these lamps in use at any one time : con- 

 sequently the demand on the battery is not very 

 great; and hence, in charging the battery, we find 

 with a twenty- ampere current, which is the cur- 

 rent used in charging them, that instead of having 

 to charge the battery all day, as I believe would have 

 to be done in case the whole forty lamps were to be 

 used, we charge for two hours in the morning, or 

 until the cells give off gas from the plates, when we 

 consider the charging as completed. I believe, after 

 three weeks' use of this battery, that some four or 

 five of the cells that were to serve in the first place 

 became feebler than usual; that is, the lamps were 

 not up to their usual standard of power. The next 

 morning it was found that certain of these cells, 

 four or five of the twenty-one that formed the bat- 

 tery, were much lower in their electromotive force 

 than the other cells of the battery; that is to say, 

 if the mean of the electromotive force was 1.85 volts, 

 they were down to less than one volt. It was 

 thought, in the first place, these cells might, per- 

 haps, become exhausted by short circuits; but, from 

 very close examination, there were revealed no short 

 circuits in the cells; and, furthermore, when the 

 charging current was put on again, those cells were 

 the first of the whole battery to give evidence of 

 being charged. In other words, it would seem as if 

 the storage capacity, if I may use that expression 

 with regard to those cells — the storage capacity of 

 these particular cells had been diminished in some 

 simple way. 



Now, we restored those cells by a process, — 

 the process which we were instructed to use in the 

 first place. A battery was first set up ; that is to say, 

 a prolonged charging of the whole body, — a charging 

 of some twenty hours with a current of twenty am- 

 peres, and then a discharging of the whole battery on 

 a fixed resistance, which was about equal to the ulti- 

 mate resistance (say, eight-tenths of an ohm); then 

 a charge of twenty hours with a twenty-ampere cur- 



