A selenium cell in its simplest form consists merely of some prepared selenium placed between two or more metal electrodes, the selenium acting as a high resistance conductor between them.
Selenium is prepared by heating it to a temperature of 120deg C.
The selenium cell {9} E is in series with a battery F and the mirror galvanometer H.
In its natural state selenium is practically a non-conductor of electricity, its resistance being forty thousand million times greater than copper.
Attempt was made to study organic selenium compounds of the heterocyclic series in reference to those properties leading to tinctorial and pharmaceutical possibilities.
Some experiments have been published claiming the similarity of the action of selenium and sulphur on rubber(4)(5).
In the perusal of the organic records of the metal, distributed over the span of a century, there are indications of the value of selenium compounds for pharmaceutical and tinctorial uses.
The tinctorial value of the selenium derivative is further evidenced by the ease with which it forms azo dyes and the deep colors of the latter.
Two series of azo dyes of selenium have been prepared and have been shown to possess a marked tinctorial value.
The clear benzalaniline was then poured into 160 grams of selenium dust in a pyrex flask on a sand bath, the flask being connected with an air condenser as before.
Lesser and Weiss(41) in their research on selenoindigo stated that the selenium dyestuff, on account of its greater molecular weight than sulphur, shows a deeper blue.
The above method has the disadvantage that water is formed in the reaction and this in turn reacts upon benzanilid at the higher temperature necessary (as selenium only melts at 217 deg.
No attempt has ever been made to compile a bibliography of selenium organic compounds.
It is equally natural to expect some organic selenium compound which liberates finely divided selenium to exert a remedial influence on animal bodies.
The crystals on standing in the presence of air and light decomposed with separation of finely divided selenium and methyl quinazolone.
Twenty grams of benzanilide was mixed in a pyrex flask with 160 grams of selenium dust and the flask placed in a nitrate bath under an air condenser.
Six years later the former(9) used a similar preparation introduced into the animal intravenously, and selenium was again found in the liver, although in smaller quantity.
Some new heterocyclic compounds ofselenium were studied and their characteristic properties more closely examined along the desired line.
You remember doubtless that the element seleniumvaries its electrical resistance under light?
Korn's apparatus depends on the ability of the element selenium to vary the strength of an electric current passing through it in proportion to the brightness with which the selenium is illuminated.
The parabolic reflector over there catches these light vibrations and focuses them on the cell of selenium which you perhaps noticed in the centre of the reflector.
Selenium even emits notes under a vibratory beam of light, the pitch depending on the frequency.
Let the diaphragm of a telephone transmitter have a very light, thin mirror on one side of it, and a beam of sunlight be thrown upon it and reflected from that on to the selenium cell, which may be some distance away.
Suppose a picture is laid off into small squares and there is a selenium cell corresponding to each square and for each selenium cell there is a wire that runs to a distant station in which circuit there is a battery.
Another curious application of the selenium cell has been attempted, but has scarcely gone beyond the domain of theory.
Selenium is thrown down at first of a fine brownish red, which gradually becomes darker.
If the current is feeble, the deposit of selenium is moderately compact; that of tellurium is always loose, and it often floats on the liquid.
That pushed-in end of the box which we hid over in Warrington's had, as you might have noticed, a selenium plate on the inside partition, facing the open end of the box.
Selenium in the dark is a poor conductor of electricity; in the light it, strange to say, becomes a good conductor.
As the speed of the disc increased the rate of the light-flashes increased also, and produced in the selenium cell the same number of passages to the electric current, converted into a musical note by the receiver.
He hopes to record not merely sounds but even pictures by means of light and a selenium plate.
The film is then passed between a lamp and a selenium plate connected with an electric circuit and a telephone.
The receiver consisted of a parabolic reflector to catch the rays and focus them on a selenium cell connected by an electric circuit with an ordinary telephone earpiece.
When a dark portion of the film intercepts the light of the lamp the selenium plate offers high resistance; when the light finds its way through a clear part of the film the resistance weakens.
Selenium has the peculiar property of offering less resistance to electrical currents when light is thrown upon it than when it is in darkness: and the more intense is the light the less is the obstruction it affords.
On delivering a message into the mouthpiece the speaker would, by agitating the mirror, send a succession of light waves of varying intensity towards the distant selenium cell.
The resistance of the selenium to the current varies according to the power of the light thrown upon it.
The assistant had shoved the photograph into the holder from which each section was projected on the selenium cell screen.
That telephotograph apparatus, I remembered, depended on the ability of the element seleniumto vary the strength of an electric current passing through it in proportion to the brightness with which the selenium is illuminated.
Instead of prolonging the operation, I do it all at once, projecting the image on a sheet of tiny selenium cells.
Well," began the assistant, "this is a screen of very minute and sensitive selenium cells.
Well, I found that selenium did the trick, for a peculiarity of that mighty peculiar metal is that it offers less resistance to a current when in the light than in the dark.
You know what we call the Tesla currents, and you know what selenium is.
The selenium then presents a grayish appearance, and is ready for use.
A seleniumactinometer has been described in the Comptes Rendus in a communication from M.
For example, selenium changes its electrical resistance under the influence of light and many applications of this phenomenon have been made.
The selenium bridge forms part of the circuit of a telephone receiver and the diaphragm is thus made to vibrate at the same frequency as the light beams do.
This result is obtained by using two selenium bridges, as shown better in the side view, Figure 76.
When light shines upon selenium its electrical resistance is lowered, and hence it can be used as a light-operated valve to control the flow of electric current.
From the paper they are reflected to a selenium cell or bridge.
There is a concave reflecting lens, which reflects half of the light upon the second cell, known as the balancer selenium bridge.
If the beam be caught by a parabolic reflector, in the focus of which is a selenium cell connected with a battery and a pair of sensitive telephone receivers, the effect of these pulsations of light is heard.
The electric resistance of a selenium cell undergoes diminution with the intensity of light that falls on it.
The selenium receiver was pointed upwards against the sky.
Selenium can be precipitated with sulphuretted hydrogen as a sulphide, which is readily soluble in ammonium sulphide.
The selenium separates as a red precipitate, which (on boiling) becomes denser and black.
It is distinguished from selenium by the insolubility, in a solution of cyanide of potassium, of the metal precipitated by sodium sulphite; whereas selenium dissolves, forming a soluble potassic seleno-cyanide.
This sulphide may be oxidised with hydrochloric acid and chlorate of potash; and theselenium separated in the manner described.
Thus, having studied the element sulphur in some detail, it is not necessary to study selenium and tellurium so closely, for most of their properties can be predicted from the relation which they sustain to sulphur.
Write the names and formulas of the oxides and oxygen acids of selenium and tellurium.
Kennedy was busy adjusting the apparatus, and paused only to remark that the boxes contained two sensitive selenium surfaces balanced against two carbon resistances.
Up-stairs in the art-gallery he next installed several boxes such as those which I had seen him experimenting with during his tests of selenium on the afternoon when Mr. Spencer had first called on us.
Because," he went on seriously, "that case interrupted a long series of tests I am making on the sensitiveness of selenium to light, and I want to finish them up soon.
The method consists in the use of that peculiar property of selenium of becoming a good conductor under the action of a luminous ray, while in darkness it totally prevents the passage of the electric current.
Under the influence of the luminous rays, the resistance that the selenium offers to the passage of an electric current instantly changes.
A selenide containing two atoms of selenium in each molecule.
Traces of gold, silver, selenium or thallium are sometimes present, and the mineral is sometimes worked as an ore of gold or silver.
On experiment the selenium was found to have all the resistance required; some of the bars displayed a resistance of 1400 megohms, as much as would be offered by a telegraph wire long enough to reach from the earth to the sun.
But this resistance was found to be extremely variable; the reason was disclosed when Mr. May, an assistant, observed that the resistance of selenium is less in light than in darkness.
Werner Siemens, the eminent German physicist, produced a variety of selenium fifteen times more conductive in sunlight than in darkness.
When seleniumis rapidly cooled from a fused condition it is a non-conductor.
The selenium is applied to the cell duly heated: next comes annealing.
It was early discovered that exposure to sunlight hastens the change of selenium from one allotropic form to another; an observation of significance in the light of recent discoveries.
It was a large, cheerful oblong of light, so quite naturally I stopped to investigate, being slightly phototropic, by virtue of the selenium grids in my rectifier cells.
My selenium cells throbbed white hot within the shell of my frame, and I made up my mind that I would learn more about the mission of this Langley, and I would get even with MS-33 even if they had me dismantled for it.
And I'll put in the most sensitiveselenium plate I can make.
Luckily I've got plenty of selenium plates for the sending end.
At length he fell into a fitful doze, and he had a wild dream that he was sliding down hill on a big mirror in which all sorts of reflections were seen--reflections that he could not get to show in the selenium plates.
But I don't exactly understand how it happened," said Ned, in some bewilderment, as he gazed at the selenium plate.
Sometimes selenium comes in crystal forms, and again it is combined with various metals for different uses.
Selenium is usually obtained from the flue-dust or chamber deposits of some factory where sulphuric acid is made.
Perhaps it will be easier if I say that sometimes selenium is found in native sulphur.
I must try a different solution ofselenium on the metal plate.
Berzelius, and he gave it that name from the Greek word for moon, on account of selenium being so similar, in some ways, to tellurium.
First I'll sensitize a selenium plate, and then I'll wet it.
A small shelf had been fitted up in the booth, or closet, and on this was the apparatus, consisting of a portable telephone set, and a small box, in which was set a selenium plate.
Well, since we can't go motor boating, I guess I may as well go back and see if that new supply of selenium has come.
I'll send for another kind of selenium crystals I've heard of, and we'll try them.
At first pure selenium separates; afterwards sulphuret of selenium; and, lastly, mere sulphur.
On a new Compound of Seleniumand Oxygen—Selenic Acid, by MM.
When sulphuret of selenium is fused with carbonate of potash, the alkali not being excess, the fused mass, dissolved in water, leaves selenium undissolved and free from sulphur.
Some of the sulphuret of selenium from Lukawitz, in Bohemia, was dissolved in potash, and the solution converted into hyposulphite by exposure to the air at the temperature of 65° F.
Water then dissolves out seleniate nitrate and nitrite of soda, no selenium remaining in the residue.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "selenium" in a variety of sentences. We hope that you will now be able to make sentences using this word.
