The Experimenter for April, 192.:,
415
THIS department
is conducted for the benefit of everyone interested in electricity in all its phase. We are glad to answer questions for the benefit of all, but necessarily can only publish such matter as interests the majority of readers. 1. Not more than three questions can be answered for each correspon dent. 2. Write on only ane side of the paper; all matter should be typewritten, or else written in ink. No attention can be paid to penciled letters. 4. This departmer t does not answer questions by mail free of charge. The Editor will, however, be glad to answer special questions at the rate of 25 cents for each. On questions entailing research work, intricate calculations, patent research work, etc. , a special charge will be made. Correspondents will be informed as to such charge. Kindly oblige us by making your letter as short as possible.
Pyroelect ricity and Piezoelectricity (507)
writes:
Mr. Chin Fu, of Canton, China,
Q. Will you be kind enough to give a brief explanation of what is meant by pyroelectricity and piezoelectricity? In reply we quote from Poynting and Thompson's 'Text Book of Physics'': "Certain crystals initially showing no electrification develop, if eated uniformly, opposite surface electrifications on opposite surfaces. If they are ccoled from the neutral condition, the polarity is reversed. The phenomenon is termed pyroelectricity and it was observed first in the eighteenth century. ''If these crystals without being heated are subjected to pressure along the axis of electrification which was observed when the temperature was changed, then opposite electrifications develop at th? end of the axis. If they are subjected to tension, the polarity is reversed. The phenomenon is termed piezoelectricity. It was. discovered by J. & P. Curie in 1880. They found that the electrification tinder pressure was the same in sign as that used for cooling, while that under tension was the same in sign as that due to heating. The phenomena are evidently related to each other." I
Direction Finding (508) Mr. J. T. Haight, Swift Current, Sask., Canada, asks: Q. Iiow can I locate a source of very marked and persistent interference in my radio reception? A. Mount a receiving set provided with a loop aerial in an at tomobile and by adjusting the loop determ ne the direction from which the interference seems to come. Draw a line on the map corresponding to this direction. then assume a new position considerably distant from your firs': one and repeat the observation. Draw another line on the map corresponding to the new direction and where these two lines intersect will be located the interfering station. To check your results three or four such observations can he taken from different positions. All the lines so drawn should intersect very nearly at the same point, that point indicating the position of the station.
Magnetism and Light (509) M. Olivier de Val-Tourraine, Bordeaux, France, inquires: Q. 1. What is meant by polarized light and what relation does it bear to magnetism? A. 1. According to the widely accepted undulatory theory of light, it consists of waves of the ether, which waves like those of water, adiance in a direction at right angles to the amplitud? or heights of the vibration. In ordinary light, the vibrations are distributed all around in a circle, the waves of ether existing at every possible angle referred to the lines of propagation as a center. If any portion of the waves are restricted in their vibrations to a single plane, the portion is said to be plane -polarized. This con-
dition can be brought about by various means: light reflected from a glass surface is partly polarized, and by transmitting light through certain transparent crystals, such as tourmaline, a well-known mineral, a transparent sample of which must of course be used, the :ight passing will be polarized. A crude analogy pictures the action of such a crystal as that of a bird cage, which would only permit waves to go through it whose undulations rose and fell parallel to its wires. I f light polarized in a definite plane is made to pass through glass and some other transparent substances, exposed to a strong magnetic field, the plane of polarization will he rotated just like twisting a ribbon of paper. This is the relation of magnetism and polarized light expressed in a very crude tvay.
CPERI.IIE.VTERS and aura
-
tcurs, we want your ideas. Tell electrical stunt you have meant to write up right along, but rater got to. Perhaps you hare a nee,' idea, any new chemical or wireless experiments, perhaps you hare.cecit snore new electrically arranged "do funny"-we want these ideas, all of them. For all such contributed articles that are accepted we will pay one cent a word upon publication. The shorter the article. and the better the illustration-whether it is a sketch or photograph-the better tie like it. 1Vhv not get busy at once? ยกVritelegibly, in ink, and on one side of the paper only. EDITOR. us about that new
Curing Sulphated Batteries Ii. Slsimigu, Tokio, Japan, writes: ato informed that sulphation of storage battery plates can be remedied. Can you tell me how this is done? A. The following excerpt front G. W. \'inal's book on Storage Batteries answers your question: "A simple and effective remedy for this condition is to pour out the electrolyte and fill the cells with water. After being allowed to stand for about an hour, the battery may be put on charge at any rate of current, provided that the voltage at the terminals of the cells is less than 2.3 volts per cell. It is desirable to make the voltage as near 2.3 volts per cell as is convenient and to give the battery what is practically a constant -potential charge. The resistance of the battery will be high at the start and the current initially small, but the current will increase as the sulphate is broken down. The cells will take the current as fast as they are capable of being charged, and the process becomes more or less automatic, but the temperature must be watched and the batteries cut off or the current decreased if the temperature reaches 40 degrees C. (104 degrees F.) The charging may also be clone by the constant -current method. The water which was put in the cells becomes a solution of sulphuric acid as the charge proceeds, and readings of the rising specific (510)
Q.
I
gravity can be made. If the final specific gravity obtained after prolonged charging becomes constant at too low a value, more electrolyte should be added. It not infrequently happens that the specific gravity of the electrolyte, initially water, will rise above the normal figure. say 1.300, and this is clear eeidence that acid has at some time been added to the cells improperly, that is, when they needed only water."
Phosphorus and Life (511) S. G. Hudson, Salt Lake City, Utah, writes: Q.-I was told that phosphorus is one of the essential elements of life, but have been unable to get more detailed information on tisis subject. \Vill you tell me in what resrects phosphorus is necessary to the maintenance of life? A.-Phosphorus is essential to the growth of plants and animals. Various compounds of phosphorus are present in the soil, and plants absorb and store up these compounds, especially in their seeds. This vegetable matter is then eaten by animals, who thus assimilate the phosphorus compounds originally in the soil, and deposit them in the hones, brain and nerve tissues. Most of these phosphorus compounds are very complex and the cannot here give their exact characteristics. Bones, however, consist of about 80 per cent. of calcium phosphate, Ca,
(PO,),.
The frequent growth of crops in the soil would rapidly exhaust its phosphate content, unless the latter were replenished. For this purpose various phosphorus -bearing substances are added to the soil in the form of natural or artificial fertilizers. Artificial fertilizers are made from phosphate rock which is found in large beds in South Caro lima, Tennessee. Florida and elsewhere. Slag from basic steel works is used a great deal as a fertilizer in Europe. It contains a large percentage of phosphates. There are other sources of supply.
Chemistry of Vinegar 1512) Ichobad Meriweather, Salem, Mass.,
asks:
Q.-Will you give me some information concerning the nature and production of vinegar? A.-Vinegar is dilute acetic acid containing from 4 to 6 per cent. of the acid. It is prepared by oxidizing dilute alcohol. The transformation is accomplished by fermentation. When dilute solutions of alcohol such as beer, or weak wines, are exposed to air, they slowly become sour, owing to the conversion of alcohol into acetic acid. This change is due to the presence and activity of a ferment named from the Greek, ntyroderma aeeti; this is what is familiarly called "mother of vinegar." It is a fungus- Strong wines and pure dilute alcohol do not become sour, because the fermentive fungus cannot live in such liquids. Substances containing starch and fermentable sugars, such as fruit juices, cider and molasses. slowly ferment when exposed to the air forming alcohol first and finally vinegar Cider vinegar is made in this way.