658 



TRANS. ST. LOUIS ACAD. SCIENCE. 



ZwaN,, zincic nitride, 

 Z«3P25 " phosphide, 

 ZnS, " sulphide. 



GALLIUM. 



Atomic weight 68. 85. 

 Ga is +3 in 

 Ga^Og and corresponding salts. 



ARSENIC. 



Atomic weight 74.918 ± -016. 



A5 is — 3 in 

 H3A5, hydric arsenide, 

 CU3AS2, cupric " 

 FeAs, ferric " 



N/A5, nickelic " 

 (PA5, phosphorous arsenide)? 



A5 is 4- 3 in 

 A52O3 and all arsenites, 

 A52S3 and all thio-arsenites, 

 A5F3, arsenious fluoride, 

 A5C/3, " chloride, 



A5Br3, " bromide, 

 A5I3, " iodide, 



A5 is + 5 in 

 AS2O5 and all arsenates, 

 AS2S5 and all thio-arsenates. 



SELENIUM. 



Atomic weight about 80. 



The vapor-dehsityof Se, taken at 

 1420°, is 80.5. This seems to indi- 

 cate that the atomic weight, as de- 

 termined by the best analyses, is too 

 low. But the vapor-density cannot 

 be relied upon, since at 142° Se may 

 not be a perfect gas. The value, 

 S0.5, is however nearer the one re- 

 quired by the law of Dulong and 

 Petit. If we accept a compromise 

 of these considerations, allowing 

 analysis to weigh against specific 

 heat and vapor-density, the approx- 

 imate atomic weight of Se may be 

 taken at about 80. 



Another reason for accepting the 

 high value is given on p. 672. 



Se is — 2 in. 

 HjSe and all selenides. 



Se is -|- I in 

 ScaC^ai selenium chloride, 

 Se,Br2, " bromide, 



Se2l2) " iodide. 



Se is -|- 2 in 

 SeSOj, selenium sulphite. 



Se is +4 in 

 SeSj, selenium disulphide, 

 SeOa, and all selenites, 

 SeC/4, selenium tetrachloride, 

 SeB;'^, " tetrabromide, 



Scl J, " tetraiodide, 



SeOClo, selenyl chloride, 

 SeOBr,, " bromide, 

 SeOIa, '' iodide. 



Se is +6 in 

 SeOj and all selenates. 



BROMINE. 



Atomic weight 79.768 ± 019. 

 B;' is — I in 

 HB/- and all bromides. 

 Br is 4- I i" 

 HBrO and all hypobromites. 



Br is -|-5 in 

 HBr03 and all bromates. 



Br may he -{-'j in 

 HBrO^, hydric perbromate. 



RUBIDIUM. 



Atomic weight 85.251 ± -oiS. 

 R^ is -f- I in all compounds. 



STRONTIUM. 



Atomic weight 87.374 ± •032- 

 Sr is + 2 in 

 SrO and all strontic salts. 



Sr is + 4 in 

 SrO,, strontium dioxide. 



YTTRIUM. 



Atomic weight 89.816 ± .067. 

 Y is -I- 3 in 

 Y2O3 and all yttric salts. 



