CHEMISTRY. (ATOMIC WEIGHTS CHEMICAL ANALYSIS.) 



85 



Atomic Weights. Discrepancies still appear 

 in the value of the atomic weight of nitrogen as 

 deduced by chemical and by physical methods. 

 The mean value as found by the best chemical 

 determinations is 14.034, while the value calcu- 

 lated from the practically identical densities found 

 by Lord Rayleigh and Leduc is 14.000. A more 

 recent chemical determination, made by Mr. G. 

 Dean from silver cyanide in a state of great purity, 

 gives 14.031 nearly identical with the average 

 chemical value given above. Further work, Na- 

 ture says, is clearly necessary to explain the con- 

 siderable discrepancy of nearly 0.2 per cent, be- 

 tween the results obtained by physical and by 

 chemical methods. 



Experiments published several years ago indi- 

 cated that the formula of hyposulphurous (or 

 hydrosulphurous) acid was ELS.O., instead of the 

 accepted form H S SO 2 . This view was not gener- 

 ally adopted, and the author has made new experi- 

 ments in conjunction with M. Bazlen, to test them. 

 The results sustain them, and accordingly hypo- 

 sulphurous acid must be held to correspond in its 

 state of oxidation to the oxide S 2 O 2 . 



Four series of determinations of the atomic 

 weight of boron by Henri Gautier, using boron 

 sulphide, carbon boride, boron bromide, and boron 

 chloride, gave results the average of which is 

 11.016. This value is adopted by the author. It 

 is a little larger than the values previously found 

 by Abrahall, and again by Ramsay and Aston. 



The International Commission on Atomic 

 Weights has published a paper recognizing the de- 

 sirability of a universal standard of atomic weights 

 as asked by the German Chemical Society, but ex- 

 pressing the conviction that unanimity can not be 

 reached by starling from O = 16. Grave reasons are 

 urged by many voices against the abandonment of 

 the standard H 1. If alteration of the standard is 

 thought necessary, it would be better to start from 

 an element whose atomic weight can be conven- 

 iently ascertained such as silver or iodine which 

 also serves as a practical starting point in consid- 

 eration of the sharpness of its reactions in numer- 

 ous analytical operations. In the opinion of the 

 commission, urgent reasons for an alteration do 

 not yet present themselves. The time has not yet 

 come for an unchangeable table of atomic weights. 

 Teachers want simplicity and clearness, and in- 

 structors must suffer no difficulty in presenting 

 intelligible and confidence-inspiring statements. 

 The commission asks from teachers answers to the 

 following questions": 



Shall the unity of hydrogen be retained as the 

 standard for reckoning atomic weights? 



Shall the atomic weights be given approximately 

 with two decimal places in which the uncertain 

 figures can be recognized by the eye? 



Shall the International Atomic Weight Commis- 

 sion have the current table of atomic weights 

 edited on this basis? 



By experiments on the density of sulphur vapor 

 at very low pressures, O. Bleier and L. Kohn have 

 obtained results indicating that the true molecular 

 formula of gaseous sulphur, undissociated, is S,. 

 This value agrees with the conclusions previously 

 arrived at by the application of the freezing-point 

 and boiling-point methods to sulphur solutions. 



From two determinations with ferric oxide pre- 

 pared from precipitated ferric hydroxide, T. W. 

 Richards and G. Paul Baxter found 55.900 as the 

 mean value of the atomic weight of iron, and five 

 determinations with oxide made from ferric nitrate 

 gave the average 55.883. The latter value is re- 

 garded as nearest the truth. Experiments are 

 described which prove that ferric oxide occludes 

 no appreciable quantity of gas, and the same had 



been previously shown to be true of iron ignited 

 in hydrogen. Previous determinations are criti- 

 cised in the author's paper, and the errors which 

 led to the higher value commonly adopted are 

 suggested. 



Chemical Analysis. In a paper on the Chem- 

 istry of Perfumes, Dr. W. H. Warren, of St. Louis, 

 says that for the most part substances designated 

 as perfumes are high boiling oils. Formerly the 

 oils, Avhich are complex mixtures of several com- 

 pounds, were obtained exclusively from flowers, 

 but recently some of the essential principles have 

 been produced by chemical means, whereas the 

 artificial perfumes are mere imitations. With a 

 few exceptions, the essential principles that give 

 the perfumes their value belong to the class of the 

 terpenes. Nearly every substance having the prop- 

 erties of a perfume has in its molecule certain 

 atomic groups, the presence of which exerts a 

 marked influence on the odor. Among the more 

 important of these may be mentioned the aldehyde, 

 ketone, ester, ether, and alcohol groups. 



Dr. Carl Otto Weber begins a paper on The 

 Nature of India Rubber, with a reference to the 

 great experimental difficulties encountered in the 

 investigation of colloid bodies whose physical con- 

 stants are highly indeterminate, and which, in- 

 stead of melting points, boiling points, and solu- 

 bility, simply exhibit a gradual merging of the 

 one state into another. These difficulties are met 

 with in a pronounced degree in the chemical in- 

 vestigation of India rubber. If unworked India 

 rubber (Para) be treated with chloroform or car- 

 bon bisulphide partial solution gradually takes 

 place; and it was very early observed that by this 

 treatment the rubber was separated into two parts, 

 the one being soluble, the other insoluble and pre- 

 senting a peculiar reticulated appearance under 

 the microscope. Very divergent statements are to 

 be found respecting the relative proportions in 

 which these two constituents occur. The author, 

 on treating a specimen of Para rubber with chloro- 

 form, obtained a solution consisting of two layers, 

 the lower of which was a bright clear solution, 

 while the upper part consisted of small clots or 

 shreds of the insoluble part, composing nearly 6.5 

 per cent, of the dry weight of the rubber used. 

 This swelled to an enormous volume in various 

 solvents, but no appreciable part of it ever passed 

 into solution. The insoluble body was free from 

 stickiness, remarkably tough when dry, and only 

 moderately distensible. 



The body representing the soluble part contained 

 nearly 2 per cent, of oxygen, which on further 

 purification tended to approach a vanishing point. 

 Analysis showed that the soluble and insoluble 

 parts were not identical in composition, as had 

 been supposed. A high percentage of hydrogen 

 and a large amount of oxygen are remarkable 

 facts concerning the insoluble part. The experi- 

 ments left no doubt that to within a very few per 

 cent., India rubber consists of a soluble hydro- 

 carbon of exactly the same empirical composition 

 as the terpenes, C 10 H 10 . While the percentage of 

 oxygen may vary very considerably, the carbon- 

 hydrogen ratio is left practically unaffected, and 

 a number of varieties contain substantially the 

 same C 10 H 1(1 . We may therefore state that India 

 rubber consists chiefly of a hydrocarbon, C^H,,. 

 readily soluble in benzene, chloroform, and carbon 

 bisulphide; that at least one variety .(Para) con- 

 tains a small quantity insoluble in the above 

 solvents, and possessing a composition widely dif- 

 ferent from that of India rubber as above stated; 

 and that, in addition, oxygen products of the hy- 

 drocarbon C 10 H, n occur in quantities varying con- 

 siderably in different kinds of India rubber, but 



