XVII MOLECULAR ARCHITECTURE 429 



l8 55> 7, 1-22), who showed that complex products might 

 result from the displacement of several atoms of hydrogen 

 by an acid or basic radical. Thus three molecules of water 

 are required to produce phosphoric acid and bismuth 

 hydroxide, 



Ho) ~ 

 Bi}3 



or the salts, such as potassium hydrogen phosphate, and 

 bismuth nitrate, which are derived from them, 



H, 



Kekule (1857) on mixed types, Very similar to the 

 multiple types of Williamson and Odling are the MIXED 

 TYPES of Odling and Kekule. 



Odling (like Williamson) had derived sodium sulphate, 

 Na 2 SO 4 , from two molecules of water, but found it 

 necessary to derive sodium hyposulphite, Na 2 S 2 O 3 (ordinary 

 " hypo," now called sodium thiosulphate), from a molecule 

 of water and a molecule of sulphuretted hydrogen (Journ. 

 Chem. Soc., 1855, 7, 8), thus 



gives 2 o 2 (sodium sulphate) 



but 2 O + S gives 2 O + S (sodium thiosulphate). 



If written out in full (compare Williamson, p. 428) these 

 formulae would appear, thus : 



}o Na }o > N > 



gives S0 2 gives SO> 



H} Na} H} S Na) S 



These MIXED TYPES differ from the MULTIPLE TYPES only 

 in that the types which are linked together are different 

 instead of being identical. Kekule, who gave them their 

 name (Ann. Chem. Pharm., 1857, 104, 133), made use very 



