Vol. XXn. No. 5.] 



POPULAE SCIENCE NEWS. 



73 



€^e ^ojpukc Science i^etaiitf* 



BOSTON, MAY 1, 1888. 



AUSTIN P. NICHOLS, S.B Editor 



WILLIAM J. ROLFE, LiTT.D Associate Editor 



It has been noticed, when pure oxide of 

 zinc is heated over a Bunsen burner in a plati- 

 num crucible, that the platinum is blackened 

 from' the formation of an alloy with metallic 

 zinc ; and the onlj- explanation hitherto offered 

 has been, that the oxide was directly- disassoci- 

 ated by the heat of the flame into oxygen gas 

 and metallic zinc, just as water at very high 

 temperatures is decomposed into hydrogen and 

 oxygen. Messrs. ]\Iorse and Burton {Ameri- 

 can Chemical Journal) have investigated this 

 point, and come to the conclusion that the ef- 

 fect is one of reduction rather than disassocia- 

 tion. They find that the burning gas-flame 

 contains free hydrogen and oxygen, and that, 

 owing to the greater diff"usibility of the hydro- 

 gen through the heated platinum, it accumu- 

 lates on the inside of the crucible, where it 

 reduces the oxide of zinc to the metallic state 

 by the usual reaction. Zinc being quite vola- 

 tile at high temperatures, a very perceptible 

 loss may be caused in this way in the course 

 of an analj-sis, and the possibilit3' of such a 

 reducing atmosphere in a platinum vessel may 

 be of importance in many other analytical 



processes. 



« 



The legal restrictions upon the practice of 

 medicine in Illinois are particularly severe, 

 and the State Board of Health recently went 

 so far as to revoke the license of a physician 

 for having advertised in the newspapers. 

 This action was promptly set aside by the 

 courts, which maintained that every citizen 

 has a constitutional right to advertise his busi- 

 ness, and that the action of the Board was 

 illegal. This decision seems to us to be a 

 very just one ; for although as a matter of fact 

 no advertising physician is worthy of the slight- 

 est confidence, yet if a respectable doctor 

 chooses to advertise his business, and run the 

 risk of being classed with the quacks who 

 spread themselves and their alleged cures so 

 conspicuously before the public, it is going too 

 far to say that he shall be prevented from do- 

 ing so b^- law. Medicine is in one sense a 

 profession, but in another sense it is a trade, 

 and is governed by the same natural laws that 

 affect all other forms of business. 



The diflBculty experienced in breaking up an 

 established habit, even if it be a trivial one, is 

 very remarkable. The exchange editor on a 

 paper in this citj', who has to overlook some 

 twenty or thirt^^ periodicals each day, informs 

 us that it is almost impossible for him to turn 

 over the pages of the magazines in their proper 

 order ; but, in spite of numerous attempts to do 

 so, he finds himself " reading them backward," 

 commencing at the end, and turning the leaves 

 toward the beginning, although at an actual 

 personal inconvenience. There seems to be no 

 reason of any kind for this proceeding, and it 

 is probably only an instance of persistence of 

 a habit accidentally' formed. 



Thk close resemblance between the s}'mbols 

 for the dram (3) and ounce (r) in prescription- 

 writing is likely to be a cause of numerous 

 mistakes, which in some cases might even prove 

 fatal. The Medical World suggests that the 

 Greek letter delta (J) be substituted for the 

 present dram symbol, thus preventing this 

 source of error on the part of either prescriber 

 or dispenser. We can see no objection to 

 this change, except the natural slowness of 

 mankind to alter an established habit, and 

 should be glad to see the "delta symbol" in 

 general use. 



" A TEST for sewer-gas " has been going the 

 rounds of the papers which deserves notice on 

 account of its misleading character. It con- 

 sists in exposing to the suspected atmosphere 

 pieces of paper moistened with a solution of 

 sugar of lead, which are supposed to indicate 

 the presence of the dreaded gas by turning 

 black. This test is entirely unreliable, and only 

 indicates the presence of sulphuretted hydro- 

 gen, a verj- disagreeable gas, but not especially 

 dangerous in small quantities. It is true that 

 the air of sewers usually contains more or less 

 of this gas ; but this is not always the case, as 

 we have exposed such test-papers for half an 

 hour over the open mouth of a very offensive 

 sewer without the slightest discoloration taking 

 place. There is no definite test for sewer-gas 

 known, and it is much better to avoid all possi- 

 bilitj- of its presence than to depend upon any 

 chemical tests for indications of its existence. 



The decision of the Supreme Court in regard 

 to the validity of the Bell telephone patent is 

 very gratifying both to the owners of the prop- 

 erty and those who have known the history 

 of the invention from the beginning. There 

 cannot be the slightest doubt that the tele- 

 phone as first described and put into practical 

 use was entirely the invention of Professor 

 Bell. The charges of fraud in obtaining the 

 patent were silly and puerile to the last degree ; 

 the claims of prior discovery hy other inven- 

 tors were, to say the least, verj' improbable ; 

 and the evidence brought forward at the hearing 

 was weak and inconclusive. It is to be hoped 

 that the claims of the inventor may not be 

 called again in question. 



A suiiSCRiBEK sends us a photograph of the 

 lower side of a window in a roof while cov- 

 ered with ice and snow, which is of interest 

 as showing how the snow, while lying upon the 

 inclined surface, and exposed to alternate thaw- 

 ing and freezing, has developed the structure 

 of a glacier. As viewed from below, the centre 

 portion seems to have moved forward faster 

 than the sides, forming curved lines such as 

 are observed in the larger glaciers flowing down 

 the mountain-sides. This little patch of ice 

 doubtless was a glacier on a small scale, al- 

 though perhaps subject to somewhat difl'erent 

 laws from those which control the movements 

 of the larger members of the family. 



QUANTIVALENCE. 



The above term, familiar to every student 

 of chemistry, is applied to certain laws of 

 chemical combination, which, from their imjjor- 

 tance, may also possess a popular interest. 



We presume it is known to most of our 

 readers that the elements always unite among 

 themselves in definite and unchangeable pro- 

 portions. In the simple case of hydrochloric 

 acid, for instance, which is composed of one 

 volume of hydrogen and one of chlorine, the 

 proportion by weight between the- two is in- 

 variably as 1 to 35.5. And as hydrogen, being 

 the lightest substance known, is taken as unitj', 

 it follows that the smallest weight of chlorine 

 which will unite with it is 35.5 times as heavy 

 an equal volume of hydrogen ; or, according to 

 the modern theory, the weight of an atom of 

 chlorine is 35.5 times that of an atom of 

 hydrogen. 



Now, in all the investigations made by 

 chemists, no other compound of hydrogen and 

 chlorine has been discovered, and it is un- 

 doubtedly true that no other compound is 

 possible. Therefore we may s&y that hydro- 

 gen and chlorine each possess one chemical 

 affinit}-, like two magnets with a single pole, 

 which mutually attract each other ; and they 

 are therefore said to have a quantivalence of 

 one, and are' called monads, from the Greek 

 word monos. 



Now, if we take another simple substance, 

 water, and analyze it, we shall find that it 

 consists of two volumes of hydrogen and one 

 of oxygen ; that is, the atom of oxygen has 

 two affinities or poles, each of which fixes an 

 atom of hydrogen: oxygen, therefore, has a 

 quantivalence of two, and is a dyad. Repre- 

 senting these affinities by dashes, we may write 



the graphic symbol of water H O H, 



which shows clearly how the dyad oxygen 

 holds the two monad hydrogens. Another 

 compound of these gases — peroxide of hydro- 

 gen — is known, which contains equal volumes 

 of hydrogen and ox3-gen ; and the symbol 



must be written, H O O ^H, 



two of the oxygen affinities or valences com- 

 bining between themselves. Usually, in writ- 

 ing these symbols, two dashes are condensed 

 into one, which would make the above symbol 

 H -0-0-H. 



Ammonia is a compound of nitrogen and 

 hydrogen, NHg ; and here we find a triad ele- 

 ment, nitrogen holding three atoms of hj'- 

 drogen. Carbon is a tetrad or quadrivalent 

 element, and in marsh gas, CH^, holds four 

 atoms of monad hydrogen, and in carbonic di- 

 oxide, CO^, holds two atoms of dyad oxygen ; 

 in either case displaying its four valences. 

 Phosphorus is a pentad element, with five 

 affinities, as shown in phosphoric chloride, 

 PClj ; while sulphur may have as many as six 

 affinities, as in sulphuric acid, H^SO^, which 

 may be graphically represented by the symbol 

 O 



II 

 H — O — S— O — H. Here the hexad sul- 



II 

 O 



phut is seen to hold two dyad atoms of oxjgen 



