BOTANICAL 



HAW* 



(CONTRIBUTION FROM THE T. JEFFERSON CO0LIDGE, JR. 

 CHEMICAL LABORATORY OF HARVARD UNIVERSITY.) 



A REVISION OF THE ATOMIC WEIGHT OF SILICON. 



THE ANALYSIS OF SILICON TETRACHLORIDE AND 



TETRABROMIDE. 



By Gregory P. Baxter, Philip F. Weatherill and 

 Edward W. Scripture, Jr. 



Received November 10, 1922. Presented February 14, 1923. 



Introduction. 



At the present time the atomic weight of silicon depends largely 

 upon the analysis of the chloride and bromide of this element. 

 Pelouze 1 and Dumas 2 compared the tetrachloride with silver, while 

 Schiel 3 determined the silver chloride obtained from the same sub- 

 stance. Thorpe and Young 4 converted the tetrabromide to silica, 

 and Becker and Meyer 5 used a similar method with the tetrachloride. 

 Two determinations of the density of silicon tetranuoride have been 

 made by Jaquerod and Tourpaian 6 and by Germann and Booth. 7 

 The results of all these determinations have been collected and re- 

 calculated by F. W. Clarke 8 and are summarized in the following 

 table. 



1 Pelouze, Compt rend., 20, 1047 (1845). 



2 Dumas, Ann. Chem. Pharm., 113. 31 (1860). 



3 Schiel, Ann. Chem. Pharm., 120, 94 (1861). 



4 Thorpe and Young, J. Chem. Soc, 61, 576 (1887). 



5 Becker and Meyer, Z. anorg. Chem., 43, 251 (1905); 47, 45 (1905). 



6 Jaquerod and Tourpaian, J. chim. phys., 11, 28, 269 (1913). 



7 Germann and Booth, J. Phys. Chem., 21, 81 (1917). 



8 Clarke, Memoirs of the Nat. Acad. Sci., Vol. XVI, No. 3. The Constants 

 c of Nature. Part V. A Recalculation of the Atomic Weights. 4th Ed., p. 



222 (1920). See also the discussion by Brauner in Abegg's Handb. d. anorg. 

 ;: Chem., Vol. Ill, Pt. 2, 284 (1909). 



9 Calculated by Clarke. 



QQ 



