US2038486A - Electrochemical recording of electric currents - Google Patents

Description

Patented Apr. 21, 1936 UNITED STATES ELECTROCHEMICAL RECORDING OF ELECTRIC CURRENTS Emil Glas, Vienna, Austria No Drawing. Application May 3, 1933, Serial No. 669,278. In Austria May 4, 1932 1 Claim.

The present invention relates to electrochemical recording of electric currents of any kind; and has among its objects the production of material upon which the record may be made and a proc- 5 ess of making a record of electric currents and of variations therein. A further object of the invention is the production of impregnated or coated material upon which the recording is to be made, which contains a reagent or reagents which will combine with the metal ions leaving the recording electrode to form immediately and directly an insoluble coloring substance. Other objects and advantages of the present invention are apparent or stated in the text below.

isted for recording electric currents, and vibrations therein which methods fundamentally may be classified into the two groups considered below.

(1) Some reaction was used by which, when the current passed, a soluble colored product was produced. There were, however, serious drawbacks in this method, the most important of g which are the comparatively low sensitivity of the reaction, and the fact that the color turns pale under the influence of air and light.

(2) These drawbacks were partly avoided by methods which are essentially founded upon first forming an insoluble reaction product (a carrier substance) and only thereafter coloring said reaction product. To this group belongs especially the reaction between ferrous ions and potassium ferrocyanide which, as is well .known, primarily forms a colorless precipitate of ferrous ferro cyanide, which is only thereafter oxidized into colored ferric ferrocyanide. In order toobtain records of constant quality, it is not only necessary to keep constant the concentration of the soaking solution and the method of soaking, but 9 also to control the conditions under which the secondary coloring reaction is performed. Moreover, it is necessary that this primarily formed substance has an adsorption power as high as possible, for the colored substances are only held fast by the adsorbing effect of the carrier substance. The whole accomplishment of this prior method recording therefore becomes very complicated. The adsorbing effect is dependent only upon. the nature of the surface of the carrier substance. Therefore the color. will not be proportional to the intensity of the current, because the secondary coloring reaction needs a certain time for completion while'the adsorbing power of the carrier substance decreases.

Heretofore several electrochemical methods ex- Contrary to all these old methods, the present invention, by the use of proper imbibing substances and the electrochemical effect of the electrode recording the current, induces immediately (and without intermediate or catalytic reaction) a coloring reaction which gives a reaction product which is practically insoluble and at the same time colored. This reaction takes place practically instantaneously; and results in practically absolute sharpness of recording. Another important matter to be considered in choosing the reactions is that they also must b'e fit for recording high frequencies, like the highest musical audible frequencies. Therefore one had to take into consideration the most sensitive reaction groups, which at the same time satisfy the condition of an insoluble colored reaction product or precipitate. Another advantage obtained by the present invention is that the coloring reaction is not merely superficially done and fixed like in the methods mentioned under 2, but that much more a penetrating effect of the coloring reaction together with an intensity of color (color tone) proportional to the current flow is obtained. Owing to the penetrating effect of the method of the present invention the resistance against mechanical stress by the electrode pin (pencil) is essentially increased. On account of the stability of the final products, it is also perfectly impossible for the color to turn pale or fade. Since, regardless of whether reacting substances are brought in the soaking solution by the electric current, or are produced from components present therein or whether by catalytic effect reactions are induced, the quantitative yield per unit of time will be low and it is only possible to increase the conductivity of the soaking solution to a limited extent, the sensitiveness of a reaction, which, as above mene tioned, is of outstanding importance in the pres- .ent case, can be evaluated from two points of view. For the present purpose especially the test limit is important, i. e. the smallest quantity of substance which can be found by the reaction, no matter in what volume. on the other hand, the limiting concentration is less important. Therefore one has to take into account especially such reactions, the test limit of which is as low as possible. The sensitiveness is in many cases limited by the visibleness of the final products. If the molecules are enlarged by bringing in weight increasing groups of atoms and the coloring effect is intensified by the addition of cbloring groups, this limit is extended. As also insolubility and stability are required, the number of available reactions is considerably diminished. In the present invention all these necessities are satisfled by the use of reactions which lead to the formation of inner complex. comr ounds. Compounds which have a ring of five or six members are especially suitable, which compounds are characterized by high stability. In this group we find a series of reactions which fully satisfy all conditions. The copper salt or the diamide oi thio-oxalic acid serves as illustrative. The copper is not only by principal valencies linked to the two sulphur atoms, but also by secondary valencies to the two Nil-groups.

Practical realization is extremely simple. The record ribbon is soaked with a solution of the compound capable of reaction and is used for recording either immediately or later on (in the latter case it is wetted again with some proper liquid). It ,necesasry, a reagent improving the conductivity which also advances the reaction can be added. Metallic ions are preferably introduced in known manner by the use of a pin of the corresponding metal or of a proper alloy-mainly for reasons of solidity. The form of the pin is dependent on particular working conditions.

Recording can be made on opaque material like paper or on transparent material like cellophane, gelatine, etc. when a record ribbon is mentioned herein is always meant a sheet of the substance to be impregnated in any form and not only in the form of a long narrow ribbon.

The described method is explained by the following examples.

(1) The record ribbon is suitably impregnated with a solution (for example alcoholic solution) of diamide of thio-oxalic acid. For improving the conductivity a salt can be added, for instance sodium acetate, which at the same time advances the reaction by shifting the equilibrium in the solution in favor of the aciiorm of the diamid. For anode one uses a copper or nickel pir. or a pin of silicon bronze (Cu-+0.05% Si) which by the action 01 the current goes into solution. The record is of black color. The slight original hue of the diamide can easily be removed by subsequent washing in case it should be bothersome, without changing in the least the color of the lines. The high sensitiveness allows the highest speeds of recording.

(2) For soaking, a slightly acid (with acetic acid) or alkaline solution of nitrous naphthol (nitrosonaphthol). 'For anode a cobalt pin is used. Here also the conductivity can be increased by the addition of salts. Otherwise, the process is the same as .with diamide of thio-oxalic acid.

I claim:

In the art of electro-chemical recording by means of a metallic stylus upon a sensitized base material of the type of paper, cellophane, and gelatin the step which comprises electr'o-chemically recording with a metallic stylus upon a sen.- sitized base material in which the sensitizing agent is chosen from the group consisting of the diamide of thio-oxalic acid and nitrosonaphthol the metal stylus being one whose ions, formed as a result of the passage of the electric current through the stylus, form colored salts with said sensitizing materials, said stylus containing a metal chosen from the group consisting of copper, nickel, and cobalt.

EMIL GLAS.