Chemistry and Physics. 279 



The reaction is accompanied with the disengagement of consider- 

 able heat, and when it is complete the solution is extracted with 

 ether, and after the ether has been dried with anhydrous sodium 

 sulphate, it is distilled off under diminished pressure, leaving the 

 carbon tetranitride in the form of a white crystalline body. It 

 melts at 35-50° C, commences to decompose at 90° C, and deto- 

 nates violently at 150° C. The danger of explosion is such that 

 only small quantities, two or three tenths of a gram, should be 

 prepared in a single operation. — Bulletin, xi, 4. h. l. w. 



3. Portland Cement. — E. Janecke has made an extensive study 

 of cement clinker and has reached the conclusion that a compound 

 8Ca0.2Si0 2 .Al 2 3 , melting at 13S2° C, is the important constit- 

 uent of this material. This is believed to be an actual compound 

 rather than an eutectic mixture, because it melts at a higher tem- 

 perature than the mixtures that approach it in composition. The 

 compound has been previously noticed by Tornebohm as a con- 

 stituent of cement and called by him " alite." The author says 

 there is no great difficulty in making a constitutional formula for 

 the compound, and advances a provisional one containing four 

 rings, two of which are like the following one : 



^ ^O— Ca— O^a- ^ 

 Ca< -Ca-0> Sl < 



In the opinion of the reviewer it would be preferable, since the 

 structure is entirely unknown, to give the simplest formula con- 

 sistent with valency, for example the following : 



^0-Ca-0-Al = 

 s - ^ O — Ca ^ ^ 

 fel \ o - Ca ^ U 



^ O - Ca ^ n 



^ O - Ca > U 



\ O - Ca - O - Al = O 



Furthermore, the formula just given has a theoretical advantage 

 in allowing for a simple combination with water in the setting of 

 the cement, while in the complicated ring formula such a combi- 

 nation with water would appear to be much less simple. — Zeitschr. 

 anorgan. Chem., lxxiii, 200. h. l. w. 



4. Annual Report of the International Committee on Atomic 

 Weights for 1912. — The committee, Clarke, Ostwald, Thorpe, 



and ITrbain, give a summary of the work on atomic weights that 

 has been published during the past year. It deals with 18 ele- 

 ments, and is of considerable importance. It is interesting to notice 

 that their International Table for 1912 contains 82 elements. The 

 single one added to last year's table is Niton, the radium emana- 

 tion, to which the weight 222*4 is given. The changes made since 

 last year are : calcium 40-07, erbium 167*7, iron 55*84, mercury 

 200*6, tantalum 181*5, and vanadium 51*0. h. l. w. 



