[LM111237] Test Report, December 1888


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[LM111237] Test Report, December 1888

Editor's Notes

The amalgamations of the zinc seems to be necessary to order to positive good contact between plates and solution, and the working of the meter coul --- be depended upon -- practically ----- the remaining transition resistance if the subsequent chemical alterations above alluded to could be presented from taking place.##Chemical source of surface alteration##The chemical action which takes place independently of electrolysis in the meter bottle under ordinary circumstances has been found to be as follows:--##The zinc plates surface whether p----- or amalgamated absorb and occlude a certain amount of atmosphere oxygen. The solution of zinc sulphate generally contains also dissolved atmospheric oxygen. This zinc readily continues with this oxygen and the water forming hydroid or hydrate of zinc Zn (80)- the reaction being represented by the equation.##2 Zn + 2(-0)+0= 2 Zn (-0).##This hydrate is scarcely soluble in the solution and forms a cake of badly conducting material on the surface of the plates, so that the mercurial lustre of freshly immersed zincs give place gradually to the --- dull grey tint of the hydrate. The trnasition resistance increases at the same time. The resistance of a bottle that has been allowed to stand idle for 21 hours after the immersion of freshly amalgamated plates is sometimes high, and varies with the amount of hydration that has formed.##The passage of a current through the bottle in this condition sets up a diruptive action at the surface of the a---- and a coating action at the surface of the cathode, so that the ---- plate ----- off the -- coating of hydrate in the##[ page 130]##forms of a precipitate that falls to the bottom of the bottle, while pure zinc is built up as the gaining plate. In this way the effect of the current is to overcome and ------ the hydrate transition resistanfce restoring not the original luster but the original purity of the immersed surfaces experiments shew that the rate at which this regeneration change is brought about depends on the strength of the current. Appendix D gives the results and curves of a series of observations made with different strengths of current on No - bottles whose zincs had become strongly hydrated by idleness. Thus starting at a mean of 12 -- the resistance of the bottles --- dues reduced to 4 by our milliampere in 30 hours by 2 milliamperes in 5 hours and by 8 in 2 hours similarly cirve sheet No gives te plot of a series of daily observations on No 4 bottles alternately working and resting on a current of 25 milliamperes and These and similar appended results furnish the explanation of the observed underindication of the meter as well as of the increased tendency to error under light and discontinuous loads for in the case of a No 4 meter of a transition resistance of 1-- reduces the current in the bottle 9.1%##- - - - 3- - - - - - - - - - --16.7%##3- 23%###-- 28%##- 133%##during the time that these resistances remain in circuit so that a heavy load will quickly break down a hydrate transition resistance and the reduction of current experiment in the process will seriously affect a continuous average, while a lightly loaded meter will take a long time to bring the resistance down to the normal, and in intermittent practice may never so do completely####[page 131]####[chart]####[page 132]####[chart]####[page 133]####[chart]####[page 134]####Influence of men ----- alloyed with the zinc on is hydration.####Appendix E gives the results of a series of observations on the hydration of a number of zinc plates commencing with the pure metal and ending with an alloy of 5% distilled [mercury?]. These show that the hydration is least on the surface of pure metal and increases with the amount of mercury alloyed the gain in weight of the 8% alloys being in this case 40% in excess of that f---- with the pure zinc. These observations are also in accordance with current chemical [views?].##from this it would appear that the hydration and hence the transition resistance will be reduced if he zincs could be used unamalgamated. The influence of mercury [however?] in preventing local action together with the reasons that are given on page makes the advantage of amalgamation outweigh this disadvantage of increased tendency to hydration and mercury on the surface of the plates seems to be a necessity.##Influence of surface area on hydration.##The results obtained on this point have shown what might reasonably have been expected that the amount of hydration taking place in a given time is proportional to the area of the expressed plate surface. The results on page show that on working the No 4 bottles with the --cks and rims of the plates varnished, the amount of hydration taking place was only 26% of that found under similar circumstances with no varnish except on the top rims near the rods.##Relation between hydration and gian in weight.##The chemical question on page shows that if no precipitation from the disruptive effect of the current alluded to on page be supposed to take place every milligramme of weight found in cases at the end of the montly sum due to hydratic represents 2/3rds of a milligramme of zinc implicated in the hydrate combination and there to remain say 50 milligrammes of hydrates from the zinc surface by immersion on a bath of dilute acid, is to dissolve in the power of 30 milligrammes of zinc and - making the loss of the plate excessive to that extent.##Temperature effect on hydration.##The results do not seem to show any decided effect of temperature on the rate of hydration the gain in weight being sometimes greater in bottles kept at hight, at other times greater in bottles kept at lower temperatures. If any such effect exists, it is lost in the irregularities which individual bottles exhibit.##Influence of the quality of solution on the rate of hydration.##The quality of water employed in making up the zinc sulphate solution has been found to have a marked influence on the rate of hydration. This is shown by the results given in Appendix F of the showed resistance to a very weak current (1 ----) and tested at different dates. Solutions made from --- water one very rich in di----ed oxygen and seems to hydrate the zincs most rapidly. On the other hand solutions prepared from distilled water, particularly if]##this distilled water has been kept in closed vessels out of constant access to the air, are found to produce hydration more slowly, the transition resistance in such cases, remaining low for a much longer period. This while the resistance of bottles XXIV and XXXI made up in the usual way with distilled water kept from access to air were 2.75 and 3.65 ohms respectively after ten days, bottles XXXI and XXX with solutions made up from ion water and tap water had resistances of 17 and 21 ohms at the end of the same time.##The resistance which a bottle can attain through hydration while idler is sometimes very high if measured with a feeble current. One instance in the case of bottle No IV pages is recorded as having been repeatedly measured with 1 milliampere of current and found to be 500 --. Fifty ohms is however a more common amount after the lapses of several weeks, but all such high resistances are soon moderated by the action of current as already stated.##The transition resistance of hydration has in this way been traced to the single cause of the chemical[onion?] between the zinc and the free atmosphere oxygen together with this water, and there is reason to suppose that if this combination could be prevented the transition resistance would after the first few hours of the meters operation, vanish indefinitely.##[page 137]##[chart]##[paqge 138]##Liquid resistance##General feature##The variations to which the bottle's transition resistance is liable ------- all attempts made to arrive at the effect of the solution's temperature and density on the resistance by direct observation on the bottle the soon under similar treatment gave concordant results. It was therefore necessary to obtain their particulars in another way, and for this purpose a glass tube was selectdd about six feet long and 1 1/3 " internal diameter. The ------- were zinc ----- carefully) amalgamated before each experiment and fitting into [rubber?] stoppers at each end of the etubes which was then filled with the zinc sulphate solution of dnesity under test. The whole was placed in a ----gh readily filled with hot or cold water. Under these circumstances the resistance between the electrodes was never less than 300- in relation to which the transition resistance that may have been present is negligible. There is reason to believe that the results so obtained are correct to 2%##As already mentioned, the liquid resistance in the both depends on the specific resistance of the solution for the particular degree of temperature purity and density existing at the moment and secondly on the mechanical dimensions of the liquid space such as its height and diameter, the distance intervening between the plates and the extent of metallic surface in good liquid contact; so that irregular transition resistance may be said to affect also the liquid resistance. If this transition resistance be constant or absent, these mechanical relations in the bottle are all [fixed?], and the resistance will vary only in direct proportion with the specific resistance##Specific liquid resistance.##Effect of chemical ---- of solution.##The results obtained in this direction go to show that with good smples of pure zinc sulphate alt and with distilled or rain water, the specific resistance of solutions at the same density and temperature may be taken as constant. The effect of impurities is generally to lower the resistance.##Effect of temperature##The specific resistance of the solution always diminish as the temperature rises and does so in a ratio that is constant for all solution densities. The specific resistance of any solution at 30 [degree symbol] is approximately one third of that it offers at 0 [degree symbol] C. The practical range of meter temperatures probably [has?] between -- and 25 [degree symbol] C and at 10 [degree symbol] C . The practical range of meter temperatures probably has between 10 [degree symbol] and 25 [degree symbol] C and at 10 [degree symbol] C the ---- of any solution is very nearly -- now than its resistance are probably that for the standard meter density 1.05-- -- --- is shown in Appendix E together with the formula by which it can be independently computed##Effect of density.##The specific resistance of zinc sulphate solution diminishes as the density increases according to some unknown law until the specific gravity of 1.29 (- 20 [degree symbol] C) is reached, when it finds as minimum and then already increases with the density. As the density ----- the variation in resistance is very rapid for weak solutions but diminishes until the neighborhood of the minimum when it is very slow. The curves showing this rate of change is given in Appendix -##The effect of density on the resistance is equal at all temperature (except in the neighborhood of saturation which has no practical meter interest), so that if as certain solution of one density has a specific resistance of say 30% in excess of the second solution at another density, then tha tratio of resistance will be maintained by then at all temperatures between 0 [degree symbol] and 50 [degree symbol] C. In other words if we take the actual specific resistance at all practical temperature of a certain solution density as ------- then the corresponding resistance at any temperature of any other density can be found at once by multiplying -- a constant belonging to the density in question###Section -##On the means that can be adopted to make the present form of meter more accurate.##As already stated the principal existing cause of error is the high transition resistance thta is set up in bottle by the hydration of the zincs during the inactive periods.##Various methods of treatment tried with the ---- of preventing the hydration by --pelling the atmosphere ----- dissolved in the solution and occluded in the amalgam. Among these were####Heating the bottle and its contained plates solution to boiling points####Heating the solution to boiling point, and heating the plates in --- to various temperatures after amalgamation. &c. &c.##If these methods only ones has met with continued practical success. It is to boil the solution and to heat the zincs -- boiling ---- ------ before amalgamating show. It has been found preferable to heat the amalgamating mercury as well by ---- under water to ---- fumes--but it may be found in practical experience that it is unnecessary to do more than heat the plates themselves. The boiling of the solution is of principal importance.##Solution made from freshly distilled water or distilled water kept for some time in closed vessels out of contact with -- need not be it seems be boiled; when made from distilled water that has been once used so that has had free access to air just raising to the boiling point has been sufficient, but solutions prepared from -- water or water known to be##--- -- dissolved oxygen -- --- boiled for --- half an hour before it is ------ to ---- laboratory experiments, whether -- --- that has ---- boiled and --- in for one bottle in an ordinary ---- meter bottle ---- is be boiled before using again possibly it will not be necessary to boil it till the second or third time has ----- but this can clearly be decided by [practice?] In any case [filtering?] has to be adopted --- each --- --- - ----[boiling?] --- give very little --------##It can be readily ----- ---- solution supplied by Mr Edison from ---- laboratory for the use of meter station can be poured into bottles at once without boiling - --- first session.##To boil the solution, it will be found [convenient?] to heat three or four gallons at ----- . The density will be somewhat increased by the process and by a high temph----n a it may be necessary to add a little ---- or boiled wrote to the solution as it [ends?]##A results appended show that on a light - - - meter giving an underindication of about -- with bottle made up in the usual ---- -- under similar conditions records to one - two of the ----- amount when the bottles have been subjected to the above treatment.##Section III####Suggested -----ments --able of being made in [future?], ------- meters in accordance with results of this entire investigation.##(1) Calibration.##It is submitted that the shunts and spools should be calibrated and fixed in terms of the legal ohm and not as at present in terms of the B.A. ohm.##This is not in any case a matter of much importance since it is the ratio between the meter circuits and ---- their absolute unless that effects their accuracy, and all meters are presumably repaired when necessary by the meters. Still the suggestion offers itself on the ground of uniformity in the electric light system which universally adopts the legal ohm in its operations.##(3) Platinoid Shunts##It is suggested that platinoid should replace german silver in the use of shunts, the reason being that while the coefficient of temperature variation in german silver is 0.044% per [degree symbol] C it is only 0.021 % per [degree symbol] C in platinoid, and consequently an equal variation of temperature will only produce half the usual alteration in resistance.##The platinoit metal supplied to the Edison laboratory by the S---vill Manufacturing Co of Waterbury Conn. has been found by several trials to have a specific resistance of 40 [mier ohms?] and a temp: --ff of 0.021%##The permanence in the resistance of a strip some 15 long and of approximately the same##breadth and thickness --- that in a No 4 Meter shunt was ---- by measuring its resistance ---- when ------- at its extremities into two clips and those operating it ---- in the circuit of a No 8 Edison under absorbing from 5 to 20 40f. during working hours, the current being from 15 to over 150 amperes according to the ---- at the end of a fortnight the resistance of the strip agreed with the originals determination to 1/4th of one percent, and the metal was as bright as when first used. The figures are given in Appendix K##The introduction of platinoid is not a matter of great moment, as the present limit of temperature variation with german silver is as already stated put--- within 1% on each side of the normal, but if no disadvantage can be offered to the trial of platinoid it is well worthy of consideration.##The [anti?] abolition of duplicate bottle. The abolition of duplicate bottles is a subject that has already engaged the attention of the Standardizing Bureau. The treatment of the bottles will probably so far remove the tendency of the meter to underindicate, that the necessity for a duplicate bottle on the ---- of inaccuracy will disappear. It is submitted that under the form and treatment proposed the second bottle will be superfluous, and it was pointed out, at a late meeting of the Bureau, that the complaints of customers might as validly be met with the argument of a duplicate plate in the same bottle as of a duplicate bottle itself. This proposition if adopted would reduce space and labour.##The nominal resistance of shunt and ----.##It is suggested as a matter well worthy of consideration that the present ---- of the bottle circuits and shunt circuit be -----. This of course has no effect on the meter constant that has a very marked effect on the meter accuracy. It has already been pointed out that an increase of resistance in the bottles amounting to one ohms reduce the current passing during that time through the bottles by 9.1% and considering the tendency that may occasionally present itself towards hydration even in spite of treatment, there is a wide range open to underindication. By doubling the resistance of each circuit, the deduction of current for -- of extra resistance in the bottle would then be only half as much 2.5%.#The adoption of this stop means no more than to take the old type of meter with two bottle on each side of the [neutral?], each bottle with a separate shunt, to throw aside the duplicate bottle and place the remaining bottle in circuit with the two shunts and two spools together with a slight alteration in the spools). The drop of potential will then be no greater with the proposed meter then with the double shunt meter and the only difference in cost of construction will be in a little ---- spool wire.##The ratio of shunt and bottle circuits.####It is submitted that the advisability of altering the existing ratio between bottle and shunt circuits needs consideration, this being a matter that affects the meter-constant and is independent of the suggestion of double resistances last made.##The reason for this suggestion is that it ----tting seems --- generally take place in the bottles##when a current of 10 milliampere passes through it continuously for more than 40 hours. That is equivalent to a steady load of 50% full values in a No 4 meter. It is certainly [rare?] for such a [can?] to present itself practically, but it seems desirable that a meter should be able to sustain permanently a greater activity than 50% of full load.##This ----tting has been the subject of experiments given in Appendix - It seems to be almost independent of the -ensity of solution, but takes place more readily of at low temperature. The 'smut' itself prove by chemical analysis to be pure zinc with perhaps a little hydrate. It appears that when the rate of deposit on a given area exceeds a contains amount the molecules of zinc do not have time to arrange themselves in the crystalline form their mutual-- attraction desires, and consequently an amorphous condition of small density and coherence results. This smelt has evidently less resistance than the layers of liquid through which it projects, fo it ---tinences to build up more rapidly on the formations, but it certainly has a distinct resistance considerably in excess of pure metal since smelting will continue as long as any liquid space remains unfilled between the plates.####Although 10 milliamperes generally produces sm--t after 30 hours in -- -- 4 plates as above mentioned, current of 200 milliamperes can be ---- for 6 hour without appreciable smelting.##No means have yet been found by which this action can be reduced. The density of current is the only menas that can at present control it. consequently as it seems undeisrable to increase the size and are of the present plates, th question for consideration is whether the current flowing through the bottle should be reduced. The advantage to be gained being the lessened#liability to smelt, and the disadvantages being that each milligramme transferred in a month would represent a greater amount of current than at present and thus call for a proportionally greater degree of care in weighing.##If however it is considered inadvisable to allow the constant, it will be necessary to observe precaution in the disposition of meters and their nominal rating, so that at no time any be called upon to operate continuously on over 50% of their present full load duty, so that for example the present 20 amperes for a limite period continuously.##Should it be considered desirable to ins---- the capacity of these meters in the manner suggested then the question arises as to what amount of change should be mad ein the resistance ratio and meter constant. To this there can be only one answer, that the change should not exceed 20% as more than that degree of responsibility can hardly be thrown on the weighing in commercial practice. This therefore leads to another point viz that the reduction of current density by increase of resistance, in the bottle circuit to the amount of 20% will not only increase the accuracy of the meter so far as guarding against e----- bottle resistance is concerned, reducing the effect of an ----- ohm from 4.5% to 3.7%; but it would also result in causing cash milligramme of zinc transferred to represent one ampere hour of current and thus simplify the meter constant. It is true that this sompl---te of the constant would only come into consideration on establishing a station changing the subscriber's rates but on the other hand since the whole object of the meter is to record ampere hours, any##undetrimental means by which the indication of ampere hours could be obtained immediately from milligrammes without calculation could be hailed as an advantage.##The uses of two different classes of meters in any one station, each with its separate constant might give rise to confusion; but if the new meter with its changed constatnt were supplied to new stations as they formed, the difference in appearance and type would be ample means of distinction.##Plates.##The Bureau has already sanctioned and authorized the introduction of a modified form of the - plate for all meters of that and higher exp---ties. THe plate is - thicker than the original form but its areas remains unchanged. These paltes have been case in an ion mould at the Edison Laboratory from Bergmann rolled zinc from electrolysis zinc, both zinc, and alloy with mercury from 1 up to 5%. These mercury castings seem to require only one amalgamation at the ------ in order to work will thus ---ing the second and third amalgamations generally given to the existing form of plate; the metal seems well and if carefully handled oin casting some reliable and homogenous. Appendix M gives some measurements that show its density to be practically the same as Bergmann zinc if no mercury is used, so that there seems to be no danger to be apprehended from softness of material.##An important advantage is seemed by casting a tube of zinc [1/4?]'' long over the copper rod above the entrance of the latter in the plate proper. Appendix H give some measurements which hsow that when the junction between metal rod is submerged and the copper surface is not protected by varnish, local action produce loss of weight in the zinc.##The action however does not [proved?] [very far?], owing to the fact that --- metallic zinc is thereby deposited upon the exposed copper surface by bringing the zinc --- to the very stopper of the bottle the junction can never remain submerged and this source of danger disappears. The casting of the rods in this way into the substance of the zincs, particularly if barbed by a chisel, renders loose connection impossible and the rod cannot be withdrawn. This therefore saves the labor required to ----- the rods into the zincs as at present.##plates alloyed with 8% weight of mercury are recommended. They ---- ---- 110 to 120 grammes.##Varnish.##All the results show, what practical experience has conferred, that the outer surfaces of the zincs in the bottle have practically no activity. The resistance of the bottle is not appreciably altered by varnishing a covering these outside surfaces of the paltes, and [scarcely?] any deposit takes place upon them. Consequently since this surface has in practice to be kept clean, and as also liable to gain weight by hydration as much as the active face, without being of any appreciable electrical service, it would be advantageous to cover it with some permanent varnish or enamel.##Various varnishes have been tried, and though those are several which satisfy ordinary requirements, none have yet been found that will stand the necessary testing in the new treatment. In some cases as varnish that had apparently stood the treatment satisfactorily was found to subsequently give off material to the solution and these interfere with the transition resistance suggestions as to a good varnish or enamel that would be absolutely insoluble in zinc sulphate solution and that would stand raising to 100 [degree symbol] C without cracking, blistering, or decomposing; are thus in demand.##One substance has been found however to give so far satisfactory results, and that is japan?. A member of couples cast at the laboratory have been temporarily fitted together f--- inwards and the whole remaining zinc surface has then been conveniently japanned and baked for 12 or 18 hours at 200 [degree symbol] F. Two coatings successivelly applied seem to produce a tough reliable coating. The zincs are then separated and a f---st strokes of the file render their f---- ready for one amalgamation at boiling water temperature and immediate use. In this form the plates can be handled with much greater convenience, and much time is saved in their cleansing and preparation.##It should be pointed out that the coating of the sides of the plates in addition to their backs, here recommended does slighly increase the resistance of the bottle--about 7% and in this way slightly favors the tendency to sm--t by increasing the current density to that extent. Still the advantages derived from the side protection in handling and in pressing the form of the plate sum to outweigh this [detractive?] but it is a point that calls for due consideration, especially as regards the introduction of varnished plates into the existing form of meter.####As already mentioned this process of varnishing has been found to reduce the ordinary hydration gain in weight by 75%, but under the new treatment the hydration is so far lessened that it is questionable if a still further reduction to this [contact?] could be anticipated by the --- of varnish.##The japan varnish is found to give way on the edges of the plates, but if in future mould then be rounded off, no failure on this --- ---- be expected.##Production in weight and dimensions of bottles. It is suggested that the present form of No 4 bottle might -----ge useful modification, and the bureau has authorized the i---- of bottles above this in size.##There seems to be in the present form of bottle more solution then the [correct?] performance of the meter demands. Appendix F gives some measurements which show that at ordinary temperature the increase of resistance produced by taking a pair of ---- plates out of a No 4 bottle are [putting/] into a closely fitting tube 1 --" --- ---- thus circumscribing the liquid circuit--was only 0.07 and in the case of a pair of varnished plates no difference whatever could be appreciated. Since solutions [undergone?] no change during the operation of the meter it appears superfluous to plan in the bottle any excess beyond the requirements of resistance and evaporation. The ---- bottle only requires about 80 cubic centimeters of solution, while a No 4 bottle takes ---- 340. A number of their tube bottles have been tried under various conditions and the results give no reason to suppose that they would have any electrical faults in practice. They would be more economical in solution and now postaable then the present form thus saving labor in every way.##The proposed bottle would therefore be at the bottom just wide enough to freely admit the plates, and would ----- outwards towards the top to meet the demands of moulding in manufacture. It would hold about 180 c.c. of solution with the zincs in place.##It is proposed to close the bottle with a good cork and this would be a more convenient and useful stopper than the present lid of glass with corks inserted.##Couplings##The ----ge is ----tended in the hard rubber coupling, but the f--t appear to be consequently hih and it is suggested that it be reduced to one quarter of an inch, [clear?] of the zincs.##T------ density.##It is suggested that the density of the meter ---- might be incrased with advantage.####The result obtained will be a lessened resistance in this bottle, and in this way the variations in its resistance due to temperature -- accidental causes will al be compressed into a smaller compass. The effect also of [coincidental?] changes of density above or below the standard will [alter?] the resistance much less than at present, and this may be worth additional consideration if it nis decided, no recommended to boil the solution. the particular density for adoption is open to choice, but the one recommended has a specific gravity of 1.11 at 20 [degree symbol] C. This curve in Appendix J shews that the specific resistance of the solution would be reduced --% by the change and also that whenever the variation of density in the present solution from -- 54 to 1.049 or 1.089 at normal temperature reduce or increase the specific resistance by nearly 10% similar variations upon 1.110 to 1.105 or 1.115 would only affect the specific resistance by 2.3%##Some measurements made on the comparative resistance of couples freshly prepared in this proposed solid ---- and in ordinary standard solution are given --- Appendix -- it will be seen that the##----- resistances and also the extent of variation in that resistance with temperature are 50 or 60% --- for the denser solution as anticipated.##Te curve in Appendix J above referred to show that there is no great advantage to be [govnd?] by using a greater density then 1.11, as the rate of change b----- very slow after that point is reached.##One or two bottles made up with this solution and set ---- do not seem to show any greater tendency to the sublimation of salt generally called "creeping" , than the usual bottles.####Another advantage gained by the use of a density solution is that the deposit formed on the ------ would be [hinder?] ------ance consistent than that in the present bottle.####If this ---- or any other particular density of solution other than the present standard of solution other than the present standard be authorized by the Bureau it will be necessary to make a series of experiments with it and with the form of bottle adopted, in order to arrive at the best average temperature compensation. This compensation cannot be determined from a few laboratory measurements only, but requires to be also known from experiment with actually a working meters in practical uses.####A number of measurements make for checking the compensation of the existing meter are given in Appendix -.##Review of suggested alteration##the alterations that are recommended ---- -- thus recapitulated in ordser of statement.##(1) The calibration of the meter shunts and spoils in terms of the legal ohm for uniformity in system##(2) the adoption of platinoid for the use of shunts##(3) The abolition of duplicate bottles##(4) The doubling of the resistance in the shunt circuit and bottle circuits##(5) The additional increase of resistance into the bottle circuit to reduce smelting and to make the milligramme of weight represent the ampere hour current in as No 4 meter.##(6) The alloy of the plate with 5% by weight of -----y in the form already approved.##(
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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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