The Birmingham age-herald., 1922-08-20
LONG FORGOTTEN
 DETECTOR CELL IS
 HIGHLY SENSITIVE
EIectroIytic Detector Slightly Better Than Crystal, Aban- doned When Vacuum
 Tube Came
By JACK BINNs

Like all OIner dTLSt TdulO mas LIS mysteries, and one of the most out standing of these is the mystery sur rounding the downfall of the electro lytlc detector. This detector Is of especial interest to those radio fans who at present own crystal receiving sets, but yet have the opportunity ana time to make parts for themselves.
 The electrolytic detector Is equally as sensitive as the best crystal, and, In my opinion, little more sensitive than galena. It enjoyed a brief reign in the realm of radio, and just as 1t was about to become the supreme ruler the vacuum tube was brought forth and all attention was promptly turned from the electrolytic to the newcomer.
 The possibilities of the vacuum tube were so promising that all further ex- perimentation with the electrolytic detector was abandoned. and 1t quick not deserve, and which was not shared by the crystal detector.
 Similar to Crystal in Operation
 In operation the eleotrolytic de- tector Is, to a great extent, very simi- lar to the crystal detector and, in fact, Its construction Is almost identi- cal. There Is nothing difficult In it's construction or adjustment. It con sists of small glass or carbon cup. in which is placed a few drops Of a 20 per cent solution of nitric acid. This acid forms the electrolyte. Tho electrode consists of a piece of very fine platinum known as "Woolaston'' wire. which just dips under the sur face of the acid.
 The circuit in which 1t is connected Is exactly the same as that for a carborundum detector. in which dry cell battery and potentiometer are used. It's operation, however, is en- tirely different The generally accept ed theory is as follows: That as soon as the local current is applied from the potentiometer across the cell, bub- bles form around the platinum elec- trode, completely insulating it and stopping any further flow in the cir cult through the telephones.
 Theory of Operation
 As soon as the electromagnetic waves received by the aerial pass through the oscillation circuits, con sisting of the particular type of tuner used with the detector, the high fre- quency current induced dissipates the bubbles and restores the pathway for the local current to flow through, and this Is recorded In the telephones in the usual manner. corresponding to the particular form of the received signals, whether 1t be voice or tele- graph code.
 The electroiytic cell is very fine l detector of radio telephone signals, and, In fact, was one of the first de- tectors to be used in the original ex- perimental work that was undertaken | in the development of telephony by means of wireless as far back as 1907. In constructing an electorlytic de- tector. practically the same form can be used as that now employed for the | galena detector. The arm which car ries the cats whisker for the galena can be used for the electrolytic de- tector. There Is this very important exception, however, that the screw carrying the platinum wire should have a left-handed thread of very fine gauge, so that an extremely small distance will be covered by one com plete turn.
 | Wire Must Only Touch Acid
 This is very important, because if more than the tip of the platinum Is immersed In the acid the detector will | not operate as efficiently as it will when the wire is only just touching. The platinum wire should be fuse.l into the lower end of the screw. and 1t should have a diameter of .000l of an inch.
 IT Woilaston wire Is used 1t will be found to be coated with silver in or oer 10 permit easier handling. This silVer coating can be removed by a very strong solution of chemically pure hydrochloric acid, or else 1t can be removed by dipping 1t into a small amount of mercury that has been heated over a Bunsen burner.
 The cup which holds the acid can he either glass or high grade carbon. In the bottom of this very small piece or platinum, about three -sixteenths of an inch square, should be placed. and this should be connected to one of the binding posts of the detector: the screw holding the platinum wire. of course being connected to the other binding post.
 Ihree-Cell Dry Battery
 The local battery used in con iur,. ton with this detector should consist of three dry cells, around wbicn should be shunted a s,00o-ohm poten. tiometer.
 Ihe telephones used in continuation with the electrolytic detector may nave resistance as low as 75 ohm but the ordinary 2.000-ohm radio tele phones can be used without any diffi. culty whatsoever. The main noi,, about the telephones Is that the, should be well constructed and sens, tive Another important point tha, must be observed is that the nositiv, pole of the local battery must be con. nected to the arm carrying the plati. mum wire.
 As stated before, the detector vii not operate in a sensitive condition unless the very faintest portion of tn, wire is touching the acid, and this |, one Of the reasons that the electroly. tic cell was abandoned because of tn, oiil'cuIty or getting that adjustment Wire Fused in Glass
 At the time of It's abandonnAnt however. 1t had been discovered tba, If the platinum wire was fused intf glass and then filed down so that a very minute portion of 1t was exnose5 the electrode could then be solidI, immersed In the acid and the detecto, left In rugged. sensitive condition This entails little more trouble ir making the detector. but 1t is trouble that Is amply repaid by the result, obtained. If the rlatinum Is fused into r1ass 1 In this manner the detector can then be put into a sensitive condition by screwing down the electrode into the acid and leaving 1t there. It will then be found to operate perfectly under all conditions without any trouble whatsoever and without any bothe. about readjustment at any time. It should not be forgotten that with the potentiometer across the dry cell battery the battery Ia running down all the time and . switch should bc nlaced in this circuit. 10 that when -he receiver is not actually heinr used