94 



POPULAR SCIENCE MONTHLY. 



indifferently, but he used Latin and 

 symbols taken from alchemical manu- 

 scripts to designate chemical sub- 

 stances. 



THE CONDITIONS OF CHEMICAL 

 ACTION. 

 It has long been known that the 

 presence of water is necessary in order 

 that many chemical reactions shall take 

 place, and that substances which ordi- 

 narily unite with great violence have 

 no action upon each other when thor- 

 oughly dried. It has even been found 

 possible to distil phosphorus in an 

 atmosphere of oxygen, provided that 

 the phosphorus and oxygen are both 

 perfectly free from any trace of the 

 vapor of water. It has, however, been 

 found by a number of experimenters 

 that hydrogen and oxygen will unite 

 with each other when heated, even if 

 dried. This exception seemed to be due 

 to the fact that when the two gases 

 unite, water is formed, but theoretically 

 the first particles of the gases could not 

 unite unless a trace of water were 

 present. This led Professor Brereton 

 Baker, of Dulwich College, who has 

 done much work along this line, to the 

 idea that the gases used might not 

 be perfectly pure. The oxygen and 

 hydrogen for the experiment are gen- 

 erally formed by the electrolytic de- 

 composition of dilute sulfuric acid or 

 caustic potash. But several years ago 

 Professor Morley, of Cleveland, pointed 

 out that the gases from these sources 

 contain traces of impurities. Byelectro- 

 lyzing highly purified barium hydroxid, 

 Professor Baker was enabled to avoid 

 previous errors and obtain absolutely 

 pure gases. The mixed hydrogen and 

 oxygen were thoroughly dried (over 

 phosphorus pentoxid) and sealed in 

 glass tubes. After ten days' drying the 

 tubes were heated to 600 degrees Cen- 

 tigrade and remained perfectly un- 

 changed, while companion tubes, simi- 

 larly prepared, except as to the drying, 

 exploded in every instance. In tubes 

 which had been dried only two days, the 



hydrogen and oxygen united slowly to 

 form water, but did not explode. In 

 order to test the effect of higher tem- 

 peratures, tubes were prepared with a 

 silver spiral -attached to platinum 

 wires which were sealed into the glass. 

 The spiral was heated until the silver 

 melted, but no explosion took place 

 and no hydrogen was formed. When, 

 however, a platinum spiral was substi- 

 tuted the tubes did explode, probably 

 owing to the catalytic action of the 

 platinum. From the experiment with 

 the silver wires it is evident that when 

 perfectly dry, hydrogen and oxygen do 

 not combine with each other, even at 

 1,000 degrees Centigrade, the melting 

 point of silver. 



The experiment with the partially 

 dried gases seems to lend confirmation 

 to the theory of Dr. Armstrong that 

 without an electrolyte no chemical 

 action is possible; for though water is 

 but slowly formed, it is present in far 

 greater quantity than is necessary to 

 bring about the action, yet no explosion 

 follows. It may be assumed here that 

 the water formed by the union of very 

 pure gases is itself very pure, and 

 since pure water is not an electrolyte, 

 this water should not cause an explo- 

 sion of the gases. 



THE PERIODICITY OF SOLAR 

 PHENOMENA. 



In the Astronomische Nachrichten 

 (Numbers 3,723-24) F. Hahn has pro- 

 pounded a new theory to explain the 

 periodicity of solar phenomena. The 

 various theories, which have been ad- 

 vanced hitherto in explanation of the 

 periodic phenomena which occur at the 

 sim, have failed to take into account 

 the so-called solar atmosphere, the 

 light and heat absorbing envelope 

 which surrounds the photosphere. The 

 importance of this atmosphere, in con- 

 nection with its influence on the 

 radiant energy of the sun, has never 

 been properly appreciated, although 

 attention was called to it by Langley, 

 who showed that the sun, if deprived 



