Patented Dec. 25, 1928. 1,696,873

UNITED STATES PATENT OFFICE. m ROBERT T. wood, OF NIAGARA FALLS, NEW.YORK, ASSIGNOR. To AMERICAN AGENE sIUM. CORPORATION, A CORPORATION oE NEW YoRk. MAGNESIUM. . to Drawing. Application filed August 5, 1925. serial No. 48,385. The invention relates to primary, or voltaic, ride solution that the cell becomes valuelessin 50 cells or batteries of either the wet or so-called a few hours, even on open circuit. The same “dry” type, which make use of a substantially disadvantage applies to all the commercially neutral electrolytein connection with suitable used primary cell . . . Ihaye discovered, however, that this corro It would seem that a relatively high sign of magnesium or magnesium base alloys age primary cell would be obtained by using will be greatly decreased or even practically. a suitable positive with magnesium inhibited by the use of an which as the negative electrode and I am aware contains. One or more strong oxidizing agents O that attempts have been made to develop such in Solution. The amount of protection of a cell. As far as I am aware, however, these fered by the use of such an electrolyte depends have all been unsuccessful, and it has been upon the composition of the solution and the generally accepted that magnesium could oxidizing agent utilized. In general, it may not be commercially utilized as a primary cell be said that a substantially neutral or basic 15 electrode. electrolyte is more effective for this purpose One object of the invention is to make than is one which shows an acid reaction. 65 feasible the use of magnesium or magnesium I have found that salts of chromic acid, base alloys as a negative electrode in primary particularly sodium and potassium dichro cells by minimizing corrosion of the metal on mates, and the nitrates of the alkali and alka 20 open circuit, so that the cell will compare line earth metals are especially effective for favorably in life with the common “’ reducing electro-chemical corrosion of magne 70 or the Leclanché cell. sium or magnesium base alloys. With the Another object of the invention is to pro alkali metals I include also the ammonium vide a cell which develops, a substantially radical, which behaves much like them in higher voltage than the Leclanché cell or the certain reactions and is generally classed with usual “dry cell’. . them for analytical purposes. 5 These objects are rendered feasible and com The base of the electrolytein which the oxi mercially practicable by the use of a suitable dizing agent is dissolved may be an aqueous and novel electrolyte, whose advantages and solution of any of a large number of chemical 30 use will be described more fully in the follow compounds. The chlorides of the alkali and ing specification alkaline earth metals and the sulphates and 80 The Leclanché cell makes use of a negative chlorates of the alkali metals are particularly electrode of and a positive one of suitable. in conjunction with an electrolyte containing As an example of an electrolyte suitable for 35 ammonium chloride. In order to maintain the performance of my invention, and which the voltage of the cell during use, a depolari will not corrode magnesium appreciably on 85 zer, such as solid , is used. open circuit, the following compositions may This type of cell is used extensively for so be given:- called open circuit work, where the battery is Parts by weight. 40 not required constantly to supply a current, Ammonium chloride------2 such uses being bell circuits, gasoline engine 90 ignition, etc. In the most common formit is Ammonium nitrate------1 made up as the well-known “dry” cell. Sodium dichromate------1. Magnesium stands near the top of the elec Water------8 45 trochemical series and because of its high solu s In order to maintain the voltage of the tion potential a much higher voltage should be cell, I preferably use manganese dioxide as 95 produced if the zinc of the Leclanché cell is a in the usual manner. A cell replaced by magnesium. However, magnesi composed of this electrolyte in conjunction um will corrode so rapidly in ammonium chlo with carbon and pure magnesium electrodes 2 1,896,87s will develop about 2 as compared with hance greatly local corrosion of the electrode, 65 1.6 volts for carbon and zinc electrodes in the thereby shortening the life of the cell. This ordinary lueclanche cell. c requirement applies to all metallic electrode The following examples demonstrate the material and equally well to magnesium and efficacy of my electrolyte as compared with its alloys. Likewise the electrolyte should the common ammonium chloride solution: . not contain metals which are capable of be 70 Two simple cells were constructed, one elec ing precipitated as such on the magnesium trode of each being a carbon rod seven electrode, as these also will cause local ac eighths inch in diameter. The other electrode tion. 9 of each was a piece of commercially pure Magnesium base alloys which are resistant magnesium sheet, one inch wide and 0.05 to corrosion can be employed in my cells and 75 inch thick. A solution of 25 grams ammoni have found magnesium base alloys contain um chloride in 100 cc. water was placed in ing aluminum and mangahese to be partic one cell; the electrolyte in the other was ularly applicable. 5 made up according to the preferred propor It will be apparent that other electrolyte tions given above. The amount of solutions compositions may be applied than that de 80 was such that all electrodes were immersed to scribed and other oxidizing agents may be a depth of ene inch. utilized without departing from the spirit The magnesium electrode in the simple am of the invention, the aforementioned com 20 monium chloride solution was attacked im positions being cited not as limitations, but mediately by the electrolyte, and there was merely as examples suitable for the accom 85 a very brisk evolution of gas, which possessed plishment of my invention. the odor characteristic of . After In using the term “magnesium' in the four hours' immersion half of the portion in claims, I comprehend not only the pure 25 the solution had been eaten entirely away, and metal, as commercially produced, but also the remainder was but 0.006 inches thick and such alloys, composed chiefly of magnesium, 90 penetrated by many holes. as lend themselves to the same use. On the other hand, the magnesium elec claim: trode immersed in the electrolyte made up in 1. A primary cell comprising an electrode accordance with my invention was not visibly of magnesium and a neutral electrolyte con attacked. The evolution of gas was so slight taining a strong soluble oxidizing agent 95 as to be almost imperceptible and no diminu adapted to reduce the rate of corrosion of the tion in thickness could be detected with a magnesium electrode on open circuit. micrometer after 24 hours, nor was any pit 2. A primary cell comprising an electrode 35 ting visible. This cell developed a potential of magnesium and a neutral electrolyte con of 1.4 volts, measured on open circuit, and the taining a salt of chromic acid adapted to re 100 straight ammonium chloride cell, measured in duce the rate of corrosion of the magnesium the same manner, produced 1.5 volts. electrode on open circuit. l By applying a pasty mass of finely pow 3. A primary cell comprising an electrode 40 dered manganese dioxide to the carbon elec of magnesium and a neutral electrolyte con trodes, the cell made up in accordance with taining the dichromate of an alkali metal 105 my invention showed an adapted to reduce the rate of corrosion of the of 2.0 volts on open circuit, and the other magnesium electrode on open circuit. cell generated 2.2 volts. An ordinary dry 4. A primary cell comprising an electrode 45 cell will develop about 1.6 volts. of magnesium and a neutral electrolyte con The lower voltage of my cell as compared taining salts of chromic and nitric acids O with one made by using carbon and mag adapted to reduce the rate of corrosion of nesium electrodes in a solution of ammonium the magnesium electrode on open circuit. chloride appears to be due to the presence of 5. A primary cell comprising an electrode 50 oxidizing agents in solution, which tend to of magnesium and a neutral electrolyte con lower somewhat the solution tension of me. taining the dichromate of an alkali metal and 5 tallic electrodes immersed therein and there the nitrate of an alkali metal adapted to re fore lower the theoretical voltage of the cell. duce the rate of corrosion of the magnesium Metallic magnesium, however, has such a electrode on open circuit. 55 high solution tension that even with the con 6. A primary cell comprising a negative centrations of oxidizing agents necessary to electrode of magnesium and a substantially 20 inhibit corrosion, the cell will still develop a neutral solution of an oxidizing agent in con higher voltage than one containing another tact therewith adapted to reduce the rate of metal, such as zinc, in place of magnesium. corrosion of the said electrode on open cir 60 It is well known in the art that metals or cuit. alloys used as electrodes should be as free 7. A primary cell comprising an electrode 125 as possible from impurities or constituents of magnesium and an electrolyte containing which form galvanic local couples in the presence of an electrolyte. Such couples en ammonium8. A primary chloride cell andcomprising sodium andichromate. electrode 1,696,873 3 rode magnesium, the said electrolyte contain of magnesium and an electrolyte containing. ing in addition to the said base another re ammonium chloride, ammonium nitrate and agent which causes a reduction in the rate of O sodium9. A dichromate.primary cell comprising a negativew corrosion of the said electrode on open cir 5 electrode of magnesium and an electrolyte cuit. having as its base a substantially neutral re In testimony whereof I affix my signature. agent, which on open circuit will rapidly cor . . . " ROBERT T. WOOD.