SCIENCE— SUPPLEMENT 



SCIENCE WEWS 



ALL STARS PROBABLY HAVE SAME 

 COMPOSITION 



Science Service 



CoNTEART to Tvhat has formerly been supposed, 

 hot stars and cool stars probably are very nearly 

 the same in chemical eompositdon, Dr. Henry Nor- 

 ris Russell, director of the Princeton University 

 Observatory and research associate of the Mount 

 Wilson Observatory, declared in an address before 

 the Carnegie Institution of Washington here to- 

 night. 



"Eecent physical research has told us so much 

 about the properties of atoms that Tve have come 

 to a new understanding of what we observe in the 

 stars, ' ' said Dr. Russell. ' ' Our knowledge of the 

 composition of the stars depends upon the lines 

 which we observe in their spectrum and which 

 show the presence of many of the familiar chem- 

 ical elements. 



' ' The atmosphere of tie cooler stars are full 

 of the vapors of metals, while in the hottest stars 

 the metals seem almost to disappear and to be 

 replaced by gases such as nitrogen and helium. 

 It has been supposed that this means that the 

 stars differ in chemical composition, or that atoms 

 of one kind are changed into those of another 

 kind at such high temperatures; but in the lab- 

 oratory we can subject atoms to far more violent 

 treatment than they receive in the atmosphere of 

 tlie stars without the least sign of their changing 

 into atoms of other sorts. We can, however, 

 knock one or two eleotrons off the atoms, and each 

 time an electron is removed the spectrum of the 

 light given by the atom changes entirely. After 

 two or three such changes there are practically 

 no lines left in the accessible part of the spec- 

 trum, though there may be strong radiations of 

 ultra violet light or X-rays." 



Dr. Russell said that in the hotter stars the 

 atoms of the metals are in this condition and 

 though still present, do not reveal themselves to 

 the spectroscope. On the other hand, he said, 

 gases like helium are so hard to set shining that 

 it is only in the hotter stars tliat we can tell that 

 they are there. The most abundant elements, such 

 as hydrogen, show their presence when less abun- 

 dant ones would disappear. 



' ' This theory of ionization makes it probable 

 that all the stars are very similar in actual coan- 

 position — the observed differences arising from 



differences in the state in wliioh the atoms find 

 themselves in their atmospheres," he concluded. 

 "On these priaeiples it is already possible to 

 reach conclusions about the temperature and pres- 

 sures in tlie a,tmospheres of the stars. The pres- 

 sures seem almost always to be very low and the 

 gas so rarified that we would almost call it a 

 vacuum in the laboratory. The temperature in 

 the hottest stars probably reaches 25,000 de- 

 grees. ' ' 



Deep in the interior of the stars the tempera- 

 tures are enormously higher and are probably 

 millions of degrees. Dr. RusseU estimated. Here 

 it is possible that once in a while atoms of one 

 element do become changed into atoms of an- 

 other kind. There is reason to believe, he said, 

 that if hydrogen atoms are changed into others 

 an enormous amount of heat would be set free, 

 wlhich would suffice to keep the stars shining for 

 billions of years. 



TRACES OF CHEMICALS DO GOOD AND 

 HARM 



Science Service 



Negligible traces or impurities may mar or 

 make a chemical process or a product, Jerome 

 Alexander, consulting engineer of New York, told 

 the American Institute of Chemical Engineers at 

 its annual meeting. 



The Germajis scrapped their own poison gas 

 plant when they learned how the British made 

 their ' ' mustard gas ' ' or diethyldichlorsuMde 

 during the war by analyzing it and determining 

 its impurities, he explained in labeling such 

 traces telltales. 



' ' Among tihe traces that help are vitamines, ' ' 

 he said. ' ' Also the value of traces of salts in 

 water, for brewing, baking and other operations, 

 is beginning to be appreciated, and we hear now 

 of these being specially added. While 0.216 per 

 cent, of arsenic reduces the conductivity of 

 copper 39 per cent., pure copper rolls much less 

 readily than that containing arsenic, and yields 

 tubes that corrode ten times more rapidly. A 

 little lead in brass makes it machine easily and 

 prevents chattering. The reputation of Swedish 

 iron is due to the manganese impurities it eon- 

 tains. A little copper inhibits the corrosion of 

 steel. Small quantities of barium harden lead 

 and make it ring like a bell. In many alloys 



