CIIKMISTKV. 



115 



i 11 



t 



1 physiological effects, and some of tho 



heretofore attributed to phosphorus is 

 iv due to it. So also is tin 1 smell that 

 !M|i:inis phosphorus, whose vupor as 

 is believed by Schonbein to bo odorless. 

 A proees.- for extracting oil patented by W. 

 ITS coii.Msts in treating oleaginous ma- 

 terial with a solvent, then expelling the dissolved 

 oil and solvent from tho mass by centrifugal 

 introducing steam to vaporize any of the 

 -n! \ent remaining in the residuum; and drying 

 :ie by applying centrifugal force. All 

 tin- different steps of tho process are applied 



;'iile the material operated upon is contained in 

 Iving chamber of a centrifugal machine. 

 In his colorimetric method for determining 

 tannin in barks, S. J. Ilinsdalo prepares a ferric 

 liniior by adding solution of ferric chloride to 

 solution of potassium ferrocyanide. A tannic 

 solution is then made. The substance in which 

 ,n in is to bo determined is brought in con- 

 tact with a little boiling water, and the solution 

 is diluted with cold water.- Six flat-bottomed 

 3 are set upon white paper, and in the first 

 are put 5 drops of tho solution to be titrated; 

 into the others are put, respectively, 4, 5, 6, 7, 

 and 8 drops of tho solution of tannin. To each 

 are then added 5 c. c. of the ferric liquor. After 

 the lapse of 3 minutes the experimenter observes 

 ' e tint of the tannin solution which corresponds 



,ost closely with the solution under examination. 



For the rapid estimation of arsenic in ores, P. 



'. Boam uses a modification of the " Uranium 

 __ jtate method," which is applicable to all ores 

 containing arsenic, and which are attacked by 

 HN'(> 4 . The author has tested it against other 

 methods, and finds it superior to all for rapidity 

 and accuracy. 



Atomic Weights. The Committee of Re- 

 vision and Publication of the Pharmacopoeia 'of 

 tho United States has published a table of ato- 

 mic weights, prepared, at its request, by Prof. F. 

 W. Clarke, upon the basis of the most recent 

 data and his latest computations. The com- 

 mittee regards it as highly desirable for this 

 tab!.- to be adopted and uniformly followed by 

 chemists in general, at least for practical pur- 

 till it is superseded by a revised edition; 

 and it requests that all calculations and analyti- 

 cal data which are to be given for its use or cog- 

 ni/ancf be ba<ed upon the values in the table. 

 The basis to which all the atomic weights in the 

 table are referred is O = 16. 



In their estimation of the atomic weight of 



.'iirnesinm, W. M. Burton and L. D. Vorce em- 

 ploy, -d, in order to obtain magnesium of excep- 

 tional purity, a method similar to that described 

 by I>r. II. X. Morse for the preparation of pure 

 zinc by distillation. Weighed portions of this 

 pure metal were converted into the nitrate, and 

 this was ignited to the oxide. Thus the errors 

 arising from the presence of impurities and 

 those involved in determining the impurities and 

 correcting them are believed by the authors to 

 have been avoided. The atomic weight given by 

 this process was 24*211. Perfect crystals of 

 magnesium were obtained during the experiments 

 and made objects of study. From them mag- 

 nesium appears to be more closely related to 

 beryllium in its crystal form than to zinc. 



Prof. Seubert's determinations of the atomic 



weight of osmium have been completed, and give 



a final mean value of 190-8. Tho settlement of 

 this question is regarded as very important, in- 

 asmuch as it removes the last oiu.standing excep- 

 tion to tho periodic generalization. On the sup- 

 position that the chemical and physical proper- 

 ties of the elements are functions of the atomic 

 weight, the atomic weights of the four metals of 

 the gold-platinum group should increa.se from 

 that of osmium up to that of gold. The accept nl 

 atomic weights of these metals previous to 1*7* 

 stood, however, in the reverse order. At that 

 time Seubert took up the problem. The ato- 

 mic weights of the several substances were grad- 

 ually corrected, and they now stand : Osmium, 

 190-3 ; iridium, 192-5 ; platinum, 194-8 ; and gold, 

 196-7 an order fully in accord with the grada- 

 tion of chemical arid physical properties of the 

 substances. 



The atomic weight of rhodium has been rede- 

 termined by Prof. Seubert and Dr. Kobbe, of the 

 University of Tubingen, with an accuracy which 

 is regarded as leaving no doubt that the value 

 of this constant has been arrived at within the 

 ordinary limits of inevitable experimental error. 

 The experiment was made by reducing the heated 

 ammoniacal salt Rh a (NH|) 10 Cl in a current of 

 pure hydrogen to metallic rhodium. The mean 

 of ten experiments gave = 15'96, Rh 102-7; or 

 O = 16-103. Rhodium therefore retains the place 

 in the periodical system marked out for it by its 

 chemical behavior, between ruthenium, 101-4, 

 and palladium, 106-3, and in the same vertical 

 group as its analogue iridium. 



Prof. F. P. Venable advocates making O = 16 

 the standard of reference for the atomic weights. 

 Hydrogen, although its small atomic weight 

 makes it the most convenient unit, does not fur- 

 nish a convenient standard, because the ratio of 

 the atomic Weight of only a few of the elements 

 can be compared directly with it. While the 

 exact ratio of oxygen to hydrogen (usually 

 written 0=15'96) would furnish the most suitable 

 standard were it fixedly determined, its selection 

 would not be wise, because it is still liable to 

 correction. Since extreme exactness is unattain- 

 able and a compromise is necessary, the selection 

 suggested offers the solution freest from objection. 

 " The atomic weights are but relative numbers. 

 To be in any respect constants, they must be rel- 

 ative to but one single element. With but few 

 exceptions, the ratio to oxygen can be deter- 

 mined. In revision of atomic weights, then, 

 this should receive the chief attention." 



The determination of the atomic weight of 

 lanthanum by Dr. Brauner, of Prague, is con- 

 tradictory to Winkler's hypothesis that the ele- 

 ment should be regarded as tetravalent, with an 

 atomic weight of 180, instead of being, as has 

 hitherto been accepted, trivalent, with an atomic 

 weight of 138-5. Dr. Brauner reasoned, from 

 the determinations of the specific heat of lan- 

 thanum, that the old figure was correct, and then 

 proceeded to redetermine the atomic weight. His 

 experimental method consisted in converting 

 known weights of the oxide into sulphate. His 

 value obtained for the atomic weight of the ele- 

 ment is 138*2, which keeps it in its old place in 

 the trivalent group of the periodic system marked 

 off for it by its basic properties. 



The atomic weight of oeryllium has been de- 



