NOVEMBEE 25, 1921] 



SCIENCE 



525 



and van Haagen's^ recent determination of the 

 atomic weight of boron, 10.900, indicates the 

 proportions of these isotopes as nearly 1 to 

 9, the relative intensities of the positive-ray 

 spectra^ point to a considerably larger pro- 

 portion of the lighter isotope. Since we have 

 redetermined the atomic weight of boron by 

 analysis of the chloride and bromide, and 

 have obtained a result more nearly in accord 

 with Aston's experiments than with those of 

 Smith and van Haagen, it seems advisable 

 to state the outcome of our preliminary ex- 

 periments, without waiting for the comple- 

 tion of the investigation. 



Boron was obtained by reduction of boric 

 oxide with an excess of magnesium and ex- 

 traction with either hydrochloric or hydro- 

 bromic acid. To prepare the chloride, dry 

 chlorine was passed over the boron at about 

 700°. To prepare the bromide, helium satu- 

 rated with bromine nearly at the boiling 

 point of the latter substance was passed over 

 boron at 700°. After removal of the excess 

 of halogen with mercury both halides were 

 repeatedly distilled with the use of Hempel 

 fractionating columns in sealed all-glass ves- 

 sels, with complete exclusion of air. Quanti- 

 tative testing even before the completion of 

 the fractionation showed the absence of sili- 

 con halides which constituted the worst im- 

 purity. Material was collected for analysis 

 in sealed glass bulbs. Analysis was effected 

 by comparison with silver in the usual way. 



The results of the analysis of the chloride 

 agree with those of the bromide in yielding 

 the value 10.83 ± 0.01 for the atomic weight 

 of boron. On the assumption that constant 

 boiling mixtures with the halogen acids were 

 •not formed and that no separation of the 

 eight possible combinations of two isotopes of 

 both boron and chlorine took place, this new 

 value for the atomic weight of boron indi- 

 cates the proportion of the heavier isotope 

 to be about five times that of the lighter. 



G. P. Baxter, 



A. Y. SOOTT 

 Harvard tlNiVERSirY 



3 Car. Inst. Pub., No. 267 (1918). 



4 Aston, loo. cit. 



THE AMERICAN CHEMICAL SOCIETY 



(Continued) 



Isomeric dlTcyl-pyrimidines and color phe- 

 nomena: Arthur W. Dox and Lester Yodee. 

 A series of alkyl-diketo-pyrimidines was prepared 

 by condensing alkyl-malonic esters with amidines. 

 In this series four types of isomerism occur, of 

 which the following derivatives are examples: 

 (a) 5-butyl and 5,5-diethyl; (b) 5-phenyl-2-methyl 

 and 5-methyl-2-phenyl; (e) 5-isoamyl-2-phenyl and 

 5,5-diethyl-2-p-tolyl ; (d) S-allyl and cyelobutane- 

 1,5-spiro. Some of these derivatives are white, 

 others are bright yellow. Color is dependent upon 

 the presence of an aromatic group on the 2-carbon 

 and a labile hydrogen on the 5-carbon. The latter 

 makes possible a rearrangement into a tautomeric 

 enolic form with three double linkages in the 

 ring. The only exception to the color rule is 

 the spiro derivative, which is yellow. Spectro- 

 scopic examination of a typical yellow derivative 

 showed an absorption band in the violet between 

 260 and 330 h/j.. 



An octet formula for ienzene: ERiresT C. 

 Crocker. Proposed formula is ring of six carbon 

 atoms acting as single complex atom. Individual 

 carbons bonded together by sharing single pairs of 

 electrons (single bonds), with hydrogens associated 

 with pairs of electrons, as usual. The six excess 

 electrons of system are " aromatic " electrons, 

 and vibrate between the carbons, in unison. ' ' Aro- 

 matic ' ' electrons cause two distinct patterns, 

 o.p., and m., according to the influence of sub- 

 stituents in the ring. The theory accounts well 

 for mono, di and tri substitution products of 

 benzene. It accounts for aromatic structure in 

 general; particularly thiophene, furane, pyrrol, 

 naphthalanene, and anthracene. 



Diisopropylliydrazine. J. E. Bailey, W. A. 

 Notes and H. L. Lochte. Diisopropylhydrazine 

 can be easily prepared by treating a solution con- 

 taining acetone, hydrazine chloride, gum arabic 

 and colloidal platinum with hydrogen under pres- 

 sure. Dimethylketazine (CH3),C:N— N:C(CH3), 

 is at first formed and this is reduced to diiso- 

 propylhydrazine, (CH3),CHNHNHCH(CH3),. The 

 latter is a monaeid base, which forms stable salts. 

 The free base is very easily oxidized, even by ex- 

 posure to the air, probably forming an azo com- 

 pound. The investigation of this and other rela- 

 tions will be continued. 



The chlorination products of formamlide: W. 

 Lee Lewis and E. S. Ely. When formanilide ia 

 chlorinated in the presence of chlorides of sulfur 



